The detailed operation of conventional Bandgap Reference (BGR) Core circuits, including the Current Mirror BGR (CM-BGR) and the Cascaded Current Mirror BGR (Cascaded CM-BGR), is discussed in this section. These architectures are analyzed in terms of their temperature compensation mechanisms, process variation tolerance.
Conventional BGR core
Integrated circuits (ICs) must operate reliably in harsh environmental conditions, ranging from hot desert temperatures to sub-zero polar temperatures. To operate stably under such conditions, a Bandgap Voltage Reference (BGR) Core has been designed to generate a temperature-independent reference voltage, as shown in Fig. 1. The BGR circuit is essential to maintain stable operation by demonstrating process independence, stable operation over different semiconductor fabrication processes, voltage independence, minimizing variations due to supply fluctuations, and temperature independence, to operate reliably over a broad temperature range, usually from − 40 to + 125 °C14. The basic principle behind a BGR circuit is the generation of two voltages with opposite temperature coefficients to attain thermal stability. One such voltage is the Complementary to Absolute Temperature (CTAT) voltage, derived from the base-emitter voltage (VBE) of a bipolar junction transistor (BJT). The VBE voltage is of negative temperature coefficient, reducing by about − 2 mV/°C with a rise in temperature15. This CTAT voltage, from a diode-connected BJT, forms the foundation for temperature compensation in BGR circuits to provide a stable reference voltage over changing environmental conditions16.
Band gap reference core circuit. A design using NPN transistor.
So, VBE is negative temperature co-efficient (− 2mv/°C).
The second one is PTAT Voltage (Proportional to Absolute Temperature). Derived from the thermal voltage (VT = kT/q), which increases linearly with temperature at a rate of approximately + 0.087 mV/°C. By scaling this voltage appropriately, its temperature coefficient can be matched to that of VBE. A PTAT voltage generator achieved by subtracting the VBE of two BJTs operating with a current density ratio N7.
The sum of these voltages, appropriately weighted, yields a temperature-independent reference voltage.
The output reference voltage is given by.
VREF = VBE + VT⋅ln (N) = constant, which independent of PVT variations (when slope of CTAT = PTAT).
where ln (N) is a scaling factor determined by the ratio of slopes(m = 2/0.087 = 23). So, N should be very large in millions of transistors should be connected in the 2nd stage.
Robust cascaded current mirror-based Bandgap Reference (BGR) circuits
A conventional current mirror and a stable cascaded current mirror-based BGR circuit are analysed in this section for improving stability against variations of Process, Voltage, and Temperature (PVT)13,14,15. A single-stage BGR circuit based on current mirrors can be seen in Fig. 2a. The circuit consists of a PMOS current mirror (M1-M2) and a transistor-based BGR core (Q1-Q5). Temperature compensation is achieved by combining proportional-to-absolute-temperature (PTAT) and complementary-to-absolute-temperature (CTAT) voltages through the resistor RBGR.
Fig. 2
Schematic and simulation results (a) CM-BGR (b) VBGR_OUT1 simulation for different RBGR values (c) cascaded CM-BGR (d) VBGR_OUT2 simulation for different RBGR values (e) The simulation results for the variation of BGR output against the variations of supply voltage.
The cascaded current mirror-based BGR17 with its robust structure shown in Fig. 2c is comprised of two additional current mirror stages (M11-M22 and M33-M44) to achieve better current replication. As a result, the output reference voltage (VBGROUT2) has enhanced immunity to supply variations.
Figure 2b, d illustrate the impact of RBGR variation on VBGROUT1 and VBGROUT2. Similarly, the Single-stage current mirror and the Cascaded current mirror have linear relationships between V_BGR and RBGR with varying sensitivity slopes, at 37.236 μV/Ω and 42.246 μV/Ω, respectively12. Due to the greater slope obtained in the cascaded current mirror structure, it may be possible to obtain proportional to absolute temperature compensation (PTAT) for smaller RBGR values.
The stability of BGR across an operating temperature range is shown through Fig. 2b, d. Figure 2e also shows how VBGR_OUT1 and VBGR_OUT2 with varying supplies (VDD) compared to each other. A stable bandgap reference (BGR) topology, by virtue of using cascaded current mirrors, has less sensitivity to the supply voltage noise. Supply voltage is changed from 0 to 4 V, simulations are carried at various process corners as well as over a − 40 °C and 125 °C temperature range making use of the 65 nm CMOS process.
Figure 3 shows the effect of startup resistance variations on the BGR circuit output and the startup transistor biasing characteristic13,16. In Fig. 3a, the BGR output voltage (VBGROUT1) is studied versus various startup resistance (Rs) values. For lower Rs values (regions S1 and S2), the output is shifted away from the expected value and remains at around 3.2 V, which shows proper startup functioning, due to improper biasing of NM4. Thus, it is operated in a linear region as given in Fig. 3c. Nevertheless, as Rs increases above a critical value (around 20kΩ), the BGR output begins producing a constant 1.3 V (from Fig. 3b) (regions S3 to S5), which indicates that the startup circuit successfully biases the BGR properly at high resistance values, when NM4 is biased to run in the saturation region. Figure 3c shows the biasing voltage (VGS) of the startup transistor NM4 versus different Rs values. At the beginning, NM4 is in the linear and saturation regions, allowing proper circuit startup. However, as Rs increases above a certain value, NM4 switches to the cutoff region, disabling the startup circuit and causing startup failure. This analysis verifies that choosing an optimum startup resistance is crucial in ensuring reliable BGR operation.
Fig. 3
The BGR output (a) against the variations of startup resistance (b) with startup circuit (c) Biasing voltage of startup transistor (VNM4).
As shown in Fig. 4a, without the startup circuit, BGR fails to initialize correctly and stays in a metastable state, while with the startup circuit, it reaches the correct operating voltage of 1.3 V, as shown in Fig. 4b. A startup circuit is required to pull a small current at the beginning of operation in order to force the BGR into its correct operational state in Fig. 4c. Once the startup circuit is turned on, the startup transistor (NM4) pulls down on the VX4 node, which turns on the PMOS load transistors (M1, M4), taking the BGR from the zero-current state into the active operating region. During this stage, the biasing voltage VNM4 for the NM4 is very high which guarantees its conduction. The startup circuit must turn off once BGR settles so that unnecessary power dissipation does not take place when NM5 is turned on by a high potential at VX3, pulling down the N4 node, consequently turning NM4 off and ensuring that the startup circuit is disabled after initialization. After stabilization of the BGR core, the startup circuit acts as a normal turn-off circuit that prevents any unnecessary power from being consumed, as is seen from the startup transistor (INM4) reverting to zero at 120 µs.
Fig. 4
The BGR output (a) without startup circuit (b) with startup (c) current through startup transistor (INM4).
Figure 5 presents the output occurrence graphs of CM-BGR and Cascaded CM-BGR under a supply sweep at 4 V. The results indicate that the Cascaded CM-BGR is able to maintain its target output voltage of 1.05 V, thus demonstrating its stability against supply changes. On the other hand, the CM-BGR demonstrates large deviations in its output voltage, tending towards higher supply levels in the samples. Such deviations indicate that the CM-BGR is more sensitive to supply changes, thus less stable.
Fig. 5
Output occurrence plots of CM-BGR and cascaded CM-BGR.
BGR circuit design using operational amplifier
Operational amplifiers are used in applications where there is high gain and high speed. A differential input and differential output multi-stage configuration makes the circuit highly stable. With this configuration, differential signals are amplified and common-mode signals and noise are rejected simultaneously18. Differential inputs, V+ and V −, are connected to transistors M9 and M10 as shown in Fig. 6. A differential voltage can be translated into a differential current by these transistors, which form a differential pair. Transistors M1, M2, M3, and M4 also form the current mirror circuit, which provides the active load impedance of the differential pair.
Fig. 6
Schematic of 2-stage operational amplifier.
The first stage consists of the differential pair (M5, M6) and the current mirror load (M1, M2). The gain of this stage is
Figure 7a, b illustrates how the phase response of the circuit changes when frequency is altered. Phase margin, or the phase shift from − 180°, is highly significant in establishing the stability of the amplifier.
Characteristics of operational amplifier (a). Phase response (b). Gain response between outputs to differential input nodes (c) gain response between cascading nodes (d) overall gain.
At differential gain, differential gain is the difference between the Vout gain and the gain of V+, V−, with intermediate nodes (Vy1, Vz1) considered. Ripples and peaks at high frequencies indicate parasitic effects or insufficient compensation. A sudden voltage gain vs. frequency spike in Fig. 7c might indicate resonances or noise coupling within the circuit. A plot of CMRR (Fig. 7d) illustrates the difference between the differential signal and the interference resulting from common-mode signals. The higher the CMRR, the higher the rejection by a differential amplifier of common-mode signals and noise.
A BGR circuit generates stable voltage that is independent of temperature, supply voltage, and process variations. Q1, Q2, Q3, Q4, Q5 and Q6 generates the CTAT voltages (VBE1, VBE2). R1 determines the current I1, which is proportional to the voltage difference VBE1–VBE2. R2 scales the PTAT current to generate the required voltage at the output. The operational amplifier enforces a virtual short condition, ensuring that the voltages at its inputs are equal19.
Operational Amplifier-based Bandgap Reference (BGR) circuit functions based on the production of a process-insensitive and temperature-stable reference voltage7,20,21. The operational principle of this circuit is the integration of two voltage terms with opposite temperature coefficients: the base-emitter voltage (VBE) of a bipolar junction transistor (BJT), with a negative temperature coefficient, and thermal voltage (Vt)7. The nomenclature is derived from the resistor network that exhibits a positive temperature coefficient. The operational amplifier provides for proper biasing by equating the voltages at its input terminals (VBE1, VX), thus ensuring the desired current flow through the BJT network as shown in the Fig. 8a. The current is copied across multiple transistors (M0, M1, M2) to provide a voltage proportional to absolute temperature (PTAT), which is then added to the complementary-to-absolute-temperature (CTAT) results, producing an effectively temperature-insensitive output voltage. The resistive ratio determines the PTAT voltage value, allowing precise reference voltage adjustment, typically to 1.2 V. MOSFET-based current sources offer a stable bias condition, with minimal supply voltage sensitivity. Figure 8b shows the relation between RBGR and slope of VBGROUT3 for the range of temperature − 40 °C to 125 °C. RBGR is adjusted to 139KΩ bring PTAT strength which equals to CTAT. The simulation results demonstrate the range of RBGR for which slope of VBGROUT3 is constant22.
(a) Band Gap reference circuit design1 using single operational amplifier (b) VBGR_OUT3 simulation for different RBGR values.
Sub-BGR circuit design using operational amplifier
The circuit shown in Fig. 9a is a sub-BGR, which produces constant reference voltage through current summing technique5,9. The sub-BGR is achieved using bipolar junction transistors (BJTs) (Q1–Q5) to produce base-emitter voltages (VBE) with negative temperature coefficient (CTAT). The R1 resistor is used to produce a current with positive temperature coefficient, since the differential CTAT voltage (VBE1–VBE2) produces a voltage drop across it, which essentially produces a proportional-to-absolute-temperature (PTAT) current. Since VX is a CTAT voltage, the voltage drops across R2 produces a CTAT current. The sum of PTAT and CTAT currents flow through M1 to make the resulting overall current constant23. M2 mirrors the constant current to resistor R0, where the combined CTAT and PTAT components produce a stable reference voltage at VBGROUTC1. A PMOS current mirror (M1) supplies stable bias currents to facilitate proper circuit operation. An operational amplifier keeps equal voltages (VBE1 and VX) at its inputs to facilitate proper generation of the PTAT current. The PTAT current, produced by the difference between the base-emitter voltages (VBE1 and VBE2) of the BJTs and scaled by resistor R1, is summed up with the CTAT current at the output node to facilitate temperature-compensated reference current24. This current, when passed through RBGR, produces a stable output voltage (VBGROUTC1).
Fig. 9
(a) Sub-BGR circuit design1 using Operational Amplifier (b) VBGR_OUTc1 simulation for different RPTAT values.
Figure 9b plots the output voltage (VBGROUTC1) variation with temperature for different RPTAT values, which reflects the effect of RPTAT on temperature stability and the operation of the bandgap reference. The ideal bandgap reference should have a stable output voltage irrespective of the temperature change, with proper temperature compensation19. When RPTAT is scaled PTAT behavior is dominated and slope of output voltage (VBGROUTC1) is also changes, thus RPTAT is determined based on the VBGROUTC1 slope.
A century ago, the County Limerick village of Kilteely had seven pubs but one by one they shut. This year, it braced to lose the last.
The economic and social trends that have shuttered family-run pubs across Ireland appear remorseless, leaving many communities with nowhere to meet, have a drink and share stories.
But this week Kilteely bucked the trend. The doomed bar reopened after 26 villagers clubbed together to buy it. “We felt we were going to be annexed into other communities if we didn’t have a place to meet and call our own,” said Liam Carroll. “So here we are, we’re publicans.”
The new owners pooled their savings and formed a syndicate to buy the pub, which otherwise faced probable demolition and conversion into accommodation.
The new owners formed a syndicate and bought the bar and licence for €300,000. Photograph: Johnny Savage/The Guardian
The eclectic group – which includes a barrister, a solicitor, a pharmacist, a clinical psychologist, a carpenter, an accountant, a teacher, a signmaker, builders, farmers and electricians – bought the bar and licence for €300,000 (£260,000) and used its varied skills to reestablish and refurbish the business.
Previously Ahern’s, the pub is now called the Street Bar, a reference to the local expression “heading up the street”, a euphemism for heading out for a pint. (Some syndicate members wanted to call it the Ambush, after a famous 1921 attack during the British-Irish war that killed 11 soldiers and police, but that was vetoed.)
It has new wiring, a cool room for beer, Sky Sports and, tucked between wine and whiskey, a sign: “Welcome to the Street Bar. A community working together in Kilteely.” Another sign lists syndicate members.
“We hope other communities will see that it can be done,” said Carroll, the barrister. “All these closures – it doesn’t have to happen.”
Since 2005, Ireland has lost a quarter of its pubs: more than 2,100, averaging 112 a year, according to a study commissioned by the Drinks Industry Group of Ireland. The phenomenon is highest in rural areas. At county level, Limerick, in the south-west, recorded the highest decrease of 37.2%.
The closure of the pub would have left Kilteely’s main street empty of most businesses. Photograph: Johnny Savage/The Guardian
Multiple reasons are cited: the cost of living, high taxes on alcohol, drink-driving laws, young people drinking less, preferences to drink at home, the Covid pandemic and shrinking profit margins. A similar trend has closed 15,000 pubs in England, Wales and Scotland since 2000, according to the British Beer and Pub Association.
Having already lost post offices, shops and other pubs, the closure of Ahern’s – which had been kept afloat by Noreen Ahern, who is near retirement age, working an estimated 90 hours a week – would have left Kilteely’s main street empty and abandoned, save for a recycling business.
Rather than mourn, some residents proposed a rescue based on an example from the County Waterford village of Rathgormack: in 2021, 19 local people formed a syndicate to buy and run the last pub, which was due to close permanently.
A group of 20 Kilteely residents each contributed €15,000 to meet the €300,000 price and turn the pub into a private limited company with a social enterprise ethos. “We made clear to all who invested that they should expect not to see a return of their money,” said Carroll.
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The group divided tasks such as paperwork, accounts, electrics and carpentry according to skillset, said Gerry O’Dea, 54, a farmer and financial adviser. “Everybody brought something to the table.”
The pub was turned into a private limited company with a social enterprise ethos. Photograph: Johnny Savage/The Guardian
Heeding advice from the Rathgormack syndicate, the Kilteely group separated ownership and management. “You couldn’t run a pub where you have 20 people with different opinions about the price of drinks,” said Carroll.
The shareholders appointed a five-member board that in turn hired a manager who, unlike them, had experience running a pub. “You hire the best people and get out of their way,” said Eoin English, 50, an engineer. The pub would remain a gathering point, he said. “This is where people have birthday parties or post-funeral receptions.”
Daniel Kreith, 29, a solicitor and syndicate member originally from Galway, said his home village had lost nine of its 13 pubs. Kilteely showed that decline and oblivion was not inevitable, he said: “Some of them could have been saved.”
The model appears to be spreading – County Kerry’s first community-owned pub is due to open soon.
Bosco Ryan, 56, another Kilteely syndicate member, said stakeholders and their friends and families formed a network that could help sustain the Street. “We all have a responsibility to support it.”
The initial search yielded a total of 150 studies across four databases. After removing duplicates, 120 unique records were screened based on titles and abstracts. Of these, 30 full-text articles were assessed for eligibility. Following a full-text review, 14 studies were included in the final synthesis from PubMed, Scopus, Web of Science, and Google Scholar (Fig. 1). The remaining studies were excluded for reasons including lack of educational context, absence of AI-related content, or unavailability of full text. A summary of the study selection process is presented in the PRISMA flow diagram (Fig. 1).
Fig. 1
PRISMA flow diagram of study selection
Study characteristics
The narrative review includes 14 studies covering diverse geographic locations including the United States, India, Australia, Germany, Saudi Arabia, and multi-national collaborations. The selected studies employed a mix of methodologies: scoping reviews, narrative reviews, cross-sectional surveys, educational interventions, integrative reviews, and qualitative case studies. The target population across studies ranged from undergraduate medical students and postgraduate trainees to faculty members and in-service professionals.
Artificial Intelligence (AI) was applied across various educational contexts, including admissions, diagnostics, teaching and assessment, clinical decision-making, and curriculum development. Several studies focused on stakeholder perceptions, ethical implications, and the need for standardized curricular frameworks. Notably, interventions such as the Four-Week Modular AI Elective [13] and the Four-Dimensional AI Literacy Framework [12] were evaluated for their impact on learner outcomes.
Table 1 provides a comprehensive summary of each study, outlining country/region, study type, education level targeted, AI application domain, frameworks or interventions used, major outcomes, barriers to implementation, and ethical concerns addressed.
Risk of bias assessment
A comprehensive risk of bias assessment was conducted using appropriate tools tailored to each study design. For systematic and scoping reviews (e.g., Gordon et al. [2], Khalifa & Albadawy [8], Crotty et al. [11]), the AMSTAR 2 tool was applied, revealing a moderate risk of bias, primarily due to the lack of formal appraisal of included studies and incomplete reporting on funding sources. Observational studies such as that by Parsaiyan & Mansouri [9] were assessed using the Newcastle-Ottawa Scale (NOS) and showed a low risk of bias, with clear selection methods and outcome assessment. For cross-sectional survey designs (e.g., Narayanan et al. [10], Ma et al. [12], Wood et al. [14], Salih [20]), the AXIS tool was used. These showed low to moderate risk depending on sampling clarity, non-response bias, and data reporting. Qualitative and mixed-methods studies such as those by Krive et al. [13] and Weidener & Fischer [15] were appraised using a combination of the CASP checklist and NOS, showing overall low to moderate risk, particularly for their methodological rigor and triangulation. One study [19], which employed a quasi-experimental design, was evaluated using ROBINS-I and was found to have a moderate risk of bias, primarily due to concerns about confounding and deviations from intended interventions. Lastly, narrative reviews like Mondal & Mondal [17] were categorized as high risk due to their lack of systematic methodology and critical appraisal Table 2.
Table 2 Risk of bias assessment of included studies
Characteristics of included studies
A total of 14 studies were included in this systematic review, published between 2019 and 2024. These comprised a range of study designs: 5 systematic or scoping reviews, 4 cross-sectional survey studies, 2 mixed-methods or qualitative studies, 1 quasi-experimental study, 1 narrative review, and 1 conceptual framework development paper. The majority of the studies were conducted in high-income countries, particularly the United States, United Kingdom, and Canada, while others included contributions from Asia and Europe, highlighting a growing global interest in the integration of artificial intelligence (AI) in medical education.
The key themes addressed across these studies included: the use of AI for enhancing clinical reasoning and decision-making skills, curriculum integration of AI tools, attitudes and readiness of faculty and students, AI-based educational interventions and simulations, and ethical and regulatory considerations in AI-driven learning. Sample sizes in survey-based studies ranged from fewer than 100 to over 1,000 participants, representing diverse medical student populations and teaching faculty.
All included studies explored the potential of AI to transform undergraduate and postgraduate medical education through improved personalization, automation of feedback, and development of clinical competencies. However, variability in methodology, focus, and outcome reporting was observed, reinforcing the importance of structured synthesis and cautious interpretation.
A.
Applications of AI in Medical Education
AI serves multiple educational functions. Gordon et al. identified its use in admissions, diagnostics, assessments, clinical simulations, and predictive analytics [2]. Khalifa and Albadawy reported improvements in diagnostic imaging accuracy and workflow efficiency [8]. Narrative reviews by Parsaiyan et al. [9] and Narayanan et al. [10] highlighted AI’s impact on virtual simulations, personalized learning, and competency-based education.
B.
Curricular innovations and interventions
Several studies introduced innovative curricular designs. Crotty et al. advocated for a modular curriculum incorporating machine learning, ethics, and governance [11], while Ma et al. proposed a Four-Dimensional Framework to cultivate AI literacy [12]. Krive et al. [13] reported significant learning gains through a four-week elective, emphasizing the value of early, practical exposure.
Studies evaluating AI-focused educational interventions primarily reported improvements in knowledge acquisition, diagnostic reasoning, and ethical awareness. For instance, Krive et al. [13] documented substantial gains in students’ ability to apply AI in clinical settings, with average quiz and assignment scores of 97% and 89%, respectively. Ma et al. highlighted enhanced conceptual understanding through their framework, though outcomes were primarily self-reported [12]. However, few studies included objective or longitudinal assessments of educational impact. None evaluated whether improvements were sustained over time or translated into clinical behavior or patient care. This reveals a critical gap and underscores the need for robust, multi-phase evaluation of AI education interventions.
C.
Stakeholder perceptions
Both students and faculty showed interest and concern about AI integration. Wood et al. [14] and Weidener and Fischer [15] noted a scarcity of formal training opportunities, despite growing awareness of AI’s importance. Ethical dilemmas, fears of job displacement, and insufficient preparation emerged as key concerns.
D.
Ethical and regulatory challenges
Critical ethical issues were raised by Mennella et al. [16] and Mondal and Mondal [17], focusing on data privacy, transparency, and patient autonomy. Multiple studies called for international regulatory standards and the embedding of AI ethics within core curricula.
While several reviewed studies acknowledged the importance of ethical training in AI, the discussion of ethics often remained surface-level. A more critical lens reveals deeper tensions that must be addressed in AI-integrated medical education. One such tension lies between technological innovation and equity AI tools, if not designed and deployed with care, risk widening disparities by favoring data-rich, high-resource settings while neglecting underrepresented populations. Moreover, AI’s potential to entrench existing biases—due to skewed training datasets or uncritical deployment of algorithms—poses a threat to fair and inclusive healthcare delivery.
Another pressing concern is algorithmic opacity. As future physicians are expected to work alongside AI systems in high-stakes clinical decisions, the inability to fully understand or challenge these systems’ inner workings raises accountability dilemmas and undermines trust. Educational interventions must therefore go beyond theoretical awareness and cultivate critical engagement with the socio-technical dimensions of AI, emphasizing ethical reasoning, bias recognition, and equity-oriented decision-making.
E.
Barriers to implementation
Implementation hurdles included limited empirical evidence [18], infrastructural constraints [19], context-specific applicability challenges [20], and an over-reliance on conceptual frameworks [10]. The lack of unified teaching models and outcome-based assessments remains a significant obstacle.
These findings informed the creation of a conceptual framework for integrating artificial intelligence into medical education, depicted in Fig. 1. A cross-theme synthesis revealed that while AI integration strategies were broadly similar across countries, their implementation success varied significantly by geographic and economic context. High-income countries (e.g., USA, Australia, Germany) demonstrated more comprehensive curricular pilots, infrastructure support, and faculty readiness, whereas studies from LMICs (e.g., India, Saudi Arabia) emphasized conceptual interest but lacked institutional capacity and access to AI technologies. Contextual barriers such as resource limitations, cultural sensitivity, and institutional inertia appeared more pronounced in LMIC settings, influencing the feasibility and depth of AI adoption in medical education.
Based on the five synthesized themes, we developed a Comprehensive Framework for the Strategic Integration of AI in Medical Education (Fig. 2). This model incorporates components such as foundational AI literacy, ethical preparedness, faculty development, curriculum redesign, and contextual adaptability. It builds on and extends existing models such as the FACETS framework, the Technology Acceptance Model (TAM), and the Diffusion of Innovation theory. Unlike FACETS, which primarily categorizes existing studies, our framework is action-oriented and aligned with Kern’s curriculum development process, making it suitable for practical implementation. Compared to TAM and Diffusion of Innovation, which focus on user behavior and adoption dynamics, our model integrates educational design elements with implementation feasibility across diverse economic and institutional settings.
Fig. 2
A comprehensive framework for the strategic integration of artificial intelligence in medical education
Table 3 shows a comparative synthesis of included studies evaluating AI integration in medical and health professions education using Kern’s six-step curriculum development framework. The analysis reveals that most studies effectively identify the need for AI literacy (Step 1) and conduct some form of needs assessment (Step 2), often through surveys, literature reviews, or scoping exercises. However, only a subset of studies explicitly define measurable educational goals and objectives (Step 3), and even fewer describe detailed instructional strategies (Step 4) or implement their proposed curricula (Step 5). Evaluation and feedback mechanisms (Step 6) were rarely reported, and when included, they were typically limited to short-term student feedback or pre-post knowledge assessments. Longitudinal evaluations and outcome-based assessments remain largely absent. The findings underscore a critical implementation gap and emphasize the need for structured, theory-informed, and empirically evaluated AI education models tailored to medical and allied health curricula.
Table 3 Mapping AI integration in medical education: A comparative analysis using kern’s Six-Step curriculum framework
This conceptual model is informed by thematic synthesis and integrates principles from existing frameworks (FACETS, TAM, Diffusion of Innovation) while aligning with Kern’s six-step approach for curriculum design.
In a new and dramatic move, Meta CEO Mark Zuckerberg is making the most aggressive move in his AI arm race. Zuckerberg is now reorganising the company’s artificial intelligence operations by restricting the Meta Superintelligence Labs (MSL) into four distinct teams. As reported by Business Insider the company outlined the move in an internal memo from the newly appointed chief of AI Alexandr Wang. The restructuring is taking place after the aggressive hiring process in which Meta poached dozens of top AI researchers from its rivals companies. The internal email, sent by Alexandr Wang, the 28-year-old head of Meta Superintelligence Labs (MSL), outlines a dramatic restructuring aimed at accelerating Meta’s pursuit of “personal superintelligence”—AI that can outperform humans across intellectual domains.
Four pillars of Meta’s new AI strategy
In the internal memo shared with employees, Wang talks about the four specialised teams:
TBD Lab: This is a small elite unit that will majorly focus on training and scaling large models, including a mysterious “omni” model.
FAIR: It is a research arm of Meta and now it will take care of feeding innovations directly into model training.
Products & Applied Research: This team will be led by ex-GitHub CEO Nat Friedman. The team will work on integrating AI into Meta’s consumer offerings.
MSL Infra: This team will be headed by engineering veteran Aparna Ramani and it will work on building the infrastructure needed to support cutting-edge AI development.
Most of these leaders now report directly to Wang, signaling a centralization of power within MSL.
FAIR and TBD: Meta’s innovation engine
FAIR, led by Rob Fergus and chief scientist Yann LeCun will now play an important role in the development of MSL’s model. Whereas, TBD Lab will look for new directions, including the enigmatic “omni” model—believed to be a multimodal system capable of understanding text, audio, video, and more.The research wing at MSL will be headed by Shengjia Zhao, co-creator of ChatGPT, who notably does not report directly to Wang.
Read Alexandr Wang’s full memo here
Superintelligence is coming, and in order to take it seriously, we need to organize around the key areas that will be critical to reach it — research, product and infra. We are building a world-class organization around these areas, and have brought in some incredible leaders to drive the work forward.
As we previously announced, Shengjia Zhao will direct our research efforts as Chief Scientist for MSL, Nat Friedman will lead our product effort and Rob Fergus will continue to lead FAIR. Today, I’m pleased to announce that Aparna Ramani will be moving over to MSL to lead the infrastructure necessary to support our ambitious research and product bets.
As part of this, we are dissolving the AGI Foundations organization and moving the talent from that team into the right areas. Teams whose work naturally aligns with and serves our products will move to Nat’s team. Some of the researchers will move to FAIR to double down on our long term research while teams working on infra will transition into Aparna’s org. Anyone who is changing teams will get an update from their manager or HRBP today, if you haven’t already.
We’re making three key changes to our organizational design that will help us to accelerate our efforts.
Centralizing core, fundamental research efforts in TBD Lab and FAIR.
Bolstering our product efforts with applied research that will work on product-focused models.
Establishing a unified, core infrastructure team to support our research bets.
The work will map to four teams:
TBD Lab will be a small team focused on training and scaling large models to achieve superintelligence across pre-training, reasoning, and post-training, and explore new directions such as an omni model.
FAIR will be an innovation engine for MSL and we will aim to integrate and scale many of the research ideas and projects from FAIR into the larger model runs conducted by TBD Lab. Rob will continue to lead FAIR and Yann will continue to serve as Chief Scientist for FAIR, with both reporting to me.
Products & Applied Research will bring our product-focused research efforts closer to product development. This will include teams previously working on Assistant, Voice, Media, Trust, Embodiment and Developer pillars in AI Tech. Nat will continue to lead this work reporting to me.
MSL Infra team will unify elements of Infra and MSL’s infrastructure teams into one. This team will focus on accelerating AI research and production by building advanced infrastructure, optimized GPU clusters, comprehensive environments, data infrastructure, and developer tools to support state-of-the-art research, products and AI development across Meta. Aparna will lead this team reporting to me.
Ahmad and Amir will continue reporting to me focusing on strategic MSL initiatives they will share more about later.
I recognize that org changes can be disruptive, but I truly believe that taking the time to get this structure right now will allow us to reach superintelligence with more velocity over the long term. We’re still working through updated rhythms and our collaboration model across teams, including when we’ll come together as a full MSL org.
Thank you all for your flexibility as we adapt to this new structure. Every team in MSL plays a critical role and I’m excited to get to work with all of you.
Obesity is a complex disease that not only affects an individual’s appearance but also has multifaceted negative impacts on physical health, including cardiovascular diseases, type 2 diabetes, hypertension, fatty liver disease, and certain types of cancer1. Additionally, obesity contributes to psychological distress, increasing the risk of depression and anxiety, and imposes a significant economic burden on public health systems2,3. Given the rising prevalence of obesity, understanding how consumers estimate food calories and make dietary choices is essential for both public health and marketing strategies. Previous research has strongly linked obesity with the underestimation of food calories, highlighting the need for interventions that help consumers make more informed choices4,5,6.
Food choices are influenced by various factors, including economic conditions, sociocultural influences, psychological aspects, marketing strategies, and food packaging design7,8,9. Among these, food packaging color plays a crucial role in shaping consumer perceptions and decision-making. Colors can act as implicit cues that influence caloric estimations, thereby affecting consumers’ food selections and dietary behaviors10. As a key element of sensory marketing, packaging color has the potential to nudge consumers toward healthier choices, making it a valuable tool for both businesses and policymakers.
Despite extensive research on food packaging and consumer behavior, there remains a significant research gap regarding how color influences calorie estimation and the mediating role of perceived healthiness in this relationship. Furthermore, most existing studies rely on self-reported surveys or controlled laboratory experiments, which may lack ecological validity. This study uses virtual reality technology to investigate how food packaging color (red vs. green) influences consumers’ calorie estimations and whether perceived healthiness mediates this effect. By uncovering these mechanisms, this research provides insights that are relevant not only to public health interventions but also to food industry marketing strategies and regulatory policies. Specifically, these findings can inform front-of-pack labeling regulations and guide food manufacturers in designing health-oriented packaging that encourages better consumer choices11,12. Given the increasing emphasis on behavioral nudges in public policy, understanding the impact of color-coded cues on food perception can help develop more effective marketing and regulatory frameworks, ultimately contributing to obesity prevention and healthier consumer behavior.
Color, caloric estimation, and perceived healthiness
Color is one of the most immediate and influential visual cues in food packaging, shaping consumer perceptions and decision-making processes. Previous research has highlighted the significant impact of front-of-pack (FOP) visual cues on consumer food choices and eating behaviors, emphasizing the role of packaging color as a critical element in shaping dietary decisions13. Consumers frequently rely on packaging color to infer the healthiness and caloric content of food rather than consulting detailed nutritional labels5,14,15. However, the specific mechanisms by which color affects food health perception and caloric estimation remain unclear, particularly regarding the mediating role of perceived healthiness in this relationship.
Food packaging color plays a crucial role in shaping consumer perceptions of healthiness. Research has shown that color-coded packaging influences consumer expectations about food attributes, often more strongly than textual nutritional information16. Green is typically associated with health, natural ingredients, and lower calories, whereas red is often linked to high-calorie, indulgent, and less healthy foods17,18. These associations arise not only from everyday experiences but also from strategic marketing practices. Many health-oriented products use green packaging to emphasize their nutritional benefits, while high-calorie snacks or fast foods often employ red to attract attention and stimulate impulse purchases19,20. Moreover, color influences sensory expectations, with red enhancing perceptions of richness and indulgence, whereas green can make food seem healthier but potentially less flavorful21. Recent research has expanded from examining singular color effects to investigating the interactions between color and other visual cues, such as shape and labeling22. Recent research by Hallez et al. (2023) further supports the significant role of packaging color in shaping consumer perceptions of healthiness, sustainability, and taste among young consumers. Their study demonstrates that color, in interaction with packaging claims, influences product evaluations, with findings closely aligning with the current research on color-driven health perceptions. This highlights the importance of considering interactive effects between color and other visual or textual cues in food packaging design, an area warranting further exploration in the context of calorie estimation23. For example, Grunert & Wills (2007) found that consumers prefer simplified front-of-pack labeling formats but differ in their reliance on color-based health cues depending on the product category and context24. However, the precise mechanisms by which color influences food health perception require further empirical validation.
Studies suggest that consumer perceptions of a food product’s healthiness significantly influence their caloric judgments25. Prior research indicates that consumers tend to overestimate the caloric content of foods they perceive as unhealthy while underestimating those they deem healthy25. This phenomenon has been observed in various contexts; for example, when consumers compare two identical yogurt products labeled as “low-fat” and “full-fat,” they consistently judge the full-fat yogurt as having higher calories, despite both products containing the same caloric content26. Similarly, fast food consumers—especially those frequenting health-branded chains such as Subway—tend to underestimate the caloric content of meals, leading to higher caloric intake27. In one study, participants were asked to evaluate the healthiness and caloric content of eight different foods. The results showed that foods perceived as healthy or beneficial for weight loss were typically underestimated in caloric content, whereas foods perceived as unhealthy or detrimental to weight loss were overestimated17. Furthermore, the health-oriented branding of a restaurant can lead consumers to underestimate the caloric content of its meals, resulting in increased caloric intake14. These findings indicate that consumers do not estimate calorie content directly based on the food itself but rather indirectly through their judgments of healthiness. Thus, food packaging color may first influence health perception, which in turn affects caloric estimation19,20. While perceived healthiness has been widely studied in consumer decision-making, its specific mediating role in the color–caloric estimation relationship remains underexplored.
Overall, food packaging color may influence caloric estimation by first shaping consumers’ perceptions of healthiness. However, most existing research has focused on color’s impact on food choice and consumption behavior, with limited direct investigation into how color affects caloric estimation22. Additionally, prior studies have relied primarily on self-reported surveys or controlled laboratory experiments, which may lack ecological validity. With the development of Virtual Reality (VR) technology, this research integrates VR to further enrich and develop its application in consumer behavior studies. Compared to traditional research methodologies, VR technology offers low costs, reusability of experimental scenarios, and immersive experiences that more accurately replicate real-world environments28, thereby holding significant advantages in consumer research. Therefore, this experiment leverages VR technology to perform experimental manipulations, aiming to explore the underlying mechanisms more profoundly.
Theoretical framework: association theory and embodied cognition theory
Sensory marketing research frequently utilizes Association Theory and Embodied Cognition Theory to explain how sensory cues influence consumer perceptions and behaviors. These theories provide a foundation for understanding how color cues (red vs. green) affect consumers’ calorie estimations through their perceptions of healthiness.
Association Theory posits that repeated co-occurrences of stimuli lead to learned associations, allowing consumers to anticipate one event based on the presence of another29. In food packaging, red and green are commonly used in health-related messaging, shaping consumer expectations. Red is often associated with cautionary signals, energy, and intensity, while green is frequently linked to health, natural ingredients, and lower-calorie options. These learned associations influence consumer judgments, leading to expectations that green-packaged foods are healthier and lower in calories, whereas red-packaged foods may be perceived as less healthy and higher in calories. This heuristic processing may guide consumer decision-making, particularly in contexts where detailed nutritional information is not immediately considered.
Embodied Cognition Theory, in contrast, suggests that cognitive processes are deeply rooted in bodily interactions with the environment, meaning that sensory experiences—such as visual exposure to color—can directly shape cognitive evaluations and perceptions. Research has demonstrated that bodily perceptions significantly impact consumer experiences; for instance, tactile sensations influence service perception, with soft textures enhancing tolerance for service failures30, while rough textures evoke empathy and generosity31. Similarly, product shape affects size perception, as consumers tend to perceive round pizzas as smaller than square pizzas of the same surface area32. In the context of food perception, color can elicit immediate cognitive and affective responses, influencing how consumers assess healthiness and caloric content. Red may enhance perceptions of higher energy content, whereas green may reinforce associations with health and lower caloric density.
By integrating Association Theory and Embodied Cognition Theory, this study examines how packaging color influences consumers’ calorie estimations through their perceptions of healthiness, providing insight into the cognitive mechanisms underlying food-related judgments.
Research objectives
This study aims to investigate how food packaging color (red vs. green) influences consumers’ calorie estimations and whether perceived healthiness mediates this effect. While previous research has demonstrated that color cues shape consumer perceptions, the underlying cognitive mechanisms—particularly the mediating role of perceived healthiness—remain underexplored. Drawing on Association Theory and Embodied Cognition Theory, this research seeks to clarify how learned associations (e.g., red with unhealthiness and green with health) and direct sensory experiences influence food-related judgments.
Specifically, this study examines whether red packaging leads to higher calorie estimations and green packaging leads to lower ones, particularly in the context of unhealthy foods. Since consumers often rely on heuristic cues, color may serve as a visual shortcut for evaluating a product’s healthiness, subsequently influencing calorie estimation. However, if the association between color and healthiness is disrupted—such as through an experimental manipulation where color is framed as unrelated to health—the effect of color on calorie estimation should diminish. Additionally, this research explores whether altering the color-health association affects consumers’ food choices, potentially leading to an increase in food selection when color no longer serves as a heuristic signal for health.
To address these research objectives, the following hypotheses are proposed:
H1: For unhealthy foods, red packaging will increase consumer calorie estimations compared to green packaging.
H2: Perceived healthiness mediates the effect of packaging color on calorie estimation of unhealthy foods.
H3: For unhealthy foods, the association of red with unhealthiness will lead to higher calorie estimations of foods in red packaging. After manipulating “color unrelated to health,” the impact of color on calorie estimation will disappear in the manipulated group.
H4: Compared to the control group, the number of food choices will increase in the manipulated group where “color is unrelated to health.”
By testing these hypotheses, this study seeks to provide both theoretical contributions to sensory marketing and practical implications for food packaging design and public health communication. Understanding how color influences calorie estimation through perceived healthiness can inform strategies for promoting healthier eating behaviors and improving consumer awareness of nutritional content.
Study 1: the impact of food packaging color on calorie Estimation
Study 1 employs a single-factor between-subjects design, with the independent variable being packaging color, divided into two levels: red and green. The dependent variable is the numerical estimation of calories, and the mediating variable is the perceived level of healthiness.
Experimental objectives and hypotheses
The purpose of Study 1 is to explore the impact of food packaging color on calorie estimation and to examine the mediating mechanism of perceived healthiness. The following hypotheses are proposed for this experiment:
H1: For unhealthy foods, red packaging will increase calorie estimations compared to green packaging.
H2: Perceived healthiness mediates the effect of packaging color on calorie estimation for unhealthy foods.
Participants
Participants were recruited through the distribution of a survey link on social media platforms using Questionnaire Star. A total of 159 respondents completed the survey, including 67 males and 92 females, with an age range of 18–32 years (M = 23.55, SD = 2.46). The studies involving human participants were reviewed and approved by Fudan University Ethics Committee (FDU-SSDPP-IRB-2024-2-103). They were performed by the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. All participants in the study provided informed consent, which involves the consent to publish their data.
Experimental materials
Food packaging images
Following previous studies, the products were categorized into two broad categories: healthy and unhealthy, with a total of six products selected (see Appendix 1).
This design allows for a controlled and focused examination of the influence of color on perceived calorie content, leveraging both visual stimuli and participant self-report measures to gather data on perception dynamics influenced by packaging color (see Fig. 1).
Fig. 1
Example of product images (red on the left and green on the right).
Healthy categories include yogurt, nuts, and fruit cereal, while unhealthy categories include potato chips, chocolate, and milk tea instant beverages. These six products were processed through Photoshop, keeping all aspects identical except for the packaging color. To maintain consistency, the RGB color values for red are: Red: 213; Green: 32; Blue: 53. The RGB color values for green are: Red: 123; Green: 225; Blue: 47.
To exclude other possible explanations such as taste appeal and attractiveness of packaging, participants were required to evaluate the taste appeal of the food, the attractiveness of the packaging, and their perception of the healthiness associated with the colors. The taste appeal was rated on a scale from 1 (not tasty at all) to 7 (very tasty). The attractiveness of the packaging was rated from 1 (not attractive at all) to 7 (very attractive).
Results (see Table 1) indicate that participants did not perceive a significant difference in taste between red and green packaging (M_red = 4.81, SD_red = 1.45; M_green = 4.80, SD_green = 1.47; t(475) = 0.05, p = 0.96), thus excluding taste appeal as another possible explanation.
Table 1 Effect of packaging color on perceived food taste ratings.
Additionally, as shown in Table 2, there is no significant difference in the perceived attractiveness of the packaging between the red and green options (M_red = 4.16, SD_red = 1.50; M_green = 4.13, SD_green = 1.48; t(475) = 0.23, p = 0.82). Therefore, the potential explanation based on the attractiveness of the packaging is also ruled out.
Table 2 Effect of packaging color on perceived packaging attractiveness.
Caloric Estimation measurement
In this experiment, participants were asked to estimate the caloric content of the displayed foods, using the calorie content of walnuts as a reference. Specifically, participants were informed: “The calorie content of walnuts we commonly consume is 574 cal per 100 g. Please estimate the calorie content per 100 g for the food items shown in the picture above.”
Measurement of perceived healthiness
Perceived healthiness refers to consumers’ immediate judgment on the healthiness of a food item. This was measured using two items: perceived healthiness of the food (1 = very unhealthy, 7 = very healthy) and perceived increase in body fat after consuming the food (1 = very little, 7 = very much). The scores for perceived increase in body fat were reverse-scored and then averaged with the perceived healthiness score to construct a healthiness variable for the food (α = 0.787), where higher scores indicate greater perceived healthiness.
Experimental procedure
Study 1 employed a questionnaire method. Participants were instructed: “Hello: Thank you very much for your participation. We are currently conducting a study on food packaging. Please fill out the questionnaire on your phone or computer based on your actual situation, which will take about 5 minutes of your time. We solemnly promise that all data is anonymous and will only be used for this research.” Participants were first required to fill out personal information, then view product images presented in the questionnaire, estimate the calorie content of the products based on the reference calorie information provided, and answer questions about their perceived healthiness of the food. Subsequently, participants evaluated the taste of the food (1 = not tasty at all, 7 = very tasty), the attractiveness of the packaging (1 = not attractive at all, 7 = very attractive), and the healthiness perception related to the color (measured by the item “Color is related to people’s physical and mental health” (1 = strongly disagree, 7 = strongly agree)). To avoid practice and fatigue effects, the order of image presentation was balanced as “unhealthy-healthy-unhealthy.”
The study distributed 159 questionnaires, retrieved 159 effective responses, and then processed the data and performed statistical analysis.
“Some of the crew were repeatedly drinking more than they were allowed to as part of their routine quality control testing,” said a subsidiary of the East Japan Railway Company, commonly known as JR East.
The misdemeanor on the swanky Train Suite Shiki-shima started around September 2022, according to the subsidiary JR East View Tourism and Sales.
“This not only severely undermines trust in our business, but is unacceptable behavior for those in a position to oversee the itinerary of our guests,” it added.
Local media reports said that six staff members have so far been taken off duty, leaving the operator with what it called “manpower” shortages.
As a result, an upcoming jaunt due to begin on Aug. 30 around the bucolic regions of Niigata and Nagano has been canceled, it said on Aug. 21.
The journey of two nights and one day costs upwards of US$3,000 and promised, among other things, in-train dinner with French cuisine, expensive wines and a winery visit.
“We sincerely apologize for the inconvenience caused to those looking forward to (the trip),” JR East said.
This section showcases the accomplishment of the suggested approach CBMDFBA and validates it using simulation data. Overall, energy usage and latency parameters concerning MDs and MHs are calculated. The simulation setup described in the section below is used to test the effectiveness of CBMDFBA.
Simulation setup
The geographical distribution of MDs is uniform inside the small dense area. Parameters used in simulation are shown in Table 4. BS is situated at a distance of 200 m from the area. 72 MDs are randomly located inside the small dense area of 20 m in length and 4.5 m in width. Out of 72 MDs, up to 20 available MHs can be selected randomly for computation offloading. For D2D connectivity, range for communication with MHs is 5 m. For both MDs and MHs, the maximum transmit power ({P_{hbox{max} }}) is 24 dBm. The network can tolerate a latency of 0.2 s. MDs and MHs have the following set of compute resources: ({f_{MD}})∈1 × 109 CPU cycles/sec and ({f_{MH}})∈1 × 109 CPU cycles/sec. For RES computation resource ({f_{RES}})∈15 × 109 CPU cycles/sec and for ES is ({f_{ES}})∈40 × 109 CPU cycles/sec. To compute 1-bit task,(Cr) ranges from 1500 to 2000. The devices effective system capacitance is ({C_Psi }) =10−28. The channel noise and path loss exponent are ({N_0}) = −174 dBm and (alpha) = 4 respectively. The data size for each user with high computational demands is uniformly distributed in ({L_r})∈ [1 2.5] Mbits. MATLAB 2023a version was used to perform simulation outcomes. The system features Intel(R) Core (TM) i5-8250 CPU running at 1.6 GHz, 16 GB RAM, and 64-bit Windows 11.
Table 4 Simulation variables.
Simulation results
The results of various computing demands are discussed in this section. The performance is measured based on two parameters: latency and energy consumption. Total energy consumption is calculated by Eq. (16). Equations (1), (4), and (5). The difference in latency is vast between the proposed work and the existing work. So, latency is plotted on a logarithmic scale to differentiate the simulation results.
In Figs. 3 and 72 users have been considered when considering the ideal case of a dense area. And out of 72 users, five users are seeking task computation. A total of four schemes have been compared in Fig. 3 name as (1) Resource allocations using Q learning with considering parameter throughput- RA(QL-Munkres-TH), (2) Resource allocations using Q learning with considering parameter distance- RA(QL-Munkres-Dist), (3) Resource allocation with considering maximum power- RA(Max-Power), (4) Proposed scheme for resource allocation using CBMDFBA. The results have shown that the latency calculated in Fig. 3(a) for 1Mbps task size in the proposed scheme is reduced by 99.87% in comparison with RA(QL-Munkres-TH) scheme, 99.89% in comparison with RA(QL-Munkres-Dist) scheme and 99.73% in comparison with RA(Max-Power) scheme. The average latency has been calculated at 2.13ms only in the proposed scheme CBMDFBA. In Fig. 3(a), it is clear that the proposed algorithm is showing that the latency is reducing with increasing the number of users. In Fig. 3(b), the task size has been considered 1.5Mbps, and it found that 99.86% has reduced the latency, 99.88%, and 99.71%, respectively, to the scheme RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power). The average latency has been calculated at 3.75ms only in the proposed scheme CBMDFBA. Figure 3(b) shows that the proposed method decreases latency as the number of user increases. In addition, it is performing well, even with an increment in task size.
Fig. 3
Latency vs. MDs for (a)({t_s}) = 1Mbps, (b)({t_s}) = 1.5Mbps, (c)({t_s}) = 2Mbps, (d)({t_s}) = 2.5 Mbps.
Figure 3(c) shows that when compared to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power) with task size of 2Mbps resulted in a 99.87%, 99.89%, and 99.74% reduction in latency. According to the proposed CBMDFBA scheme, the average latency is 4.34 ms. It also indicates that the proposed algorithm’s latency is decreasing with increasing users. Figure 3(d) demonstrates that a task size of 2.5Mbps led to a 99.84%, 99.87%, and 99.68% reduction in latency when compared to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power). The average delay, as per the proposed CBMDFBA scheme, is 6.69ms. Also, the latency is decreasing with the number of users.
In Fig. 4, Energy consumption is calculated, and simulation results are compared. In Fig. 4(a), the average energy consumption is 973.4 J for the proposed CBMDFBA scheme, which is 53.56% less than a comparison of scheme RA(QL-Munkres-TH). And 61.20% less in comparison with scheme RA(QL-Munkres-Dist) and 67.67% less with scheme RA(Max-Power) for the task size of 1Mbps. Figure 4(b) demonstrates that a task size of 1.5Mbps led to a 72.82%, 75.62%, and 79.69% reduction in energy consumption when using CBMDFBA as compared to RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power).
Fig. 4
Energy usage vs. MDs for (a)({t_s}) = 1Mbps, (b)({t_s}) = 1.5Mbps, (c)({t_s}) = 2Mbps, (d)({t_s}) = 2.5 Mbps.
The average energy consumption is calculated at 899.1 J in the proposed scheme CBMDFBA. In Fig. 4(c), task size 2Mbps is considered, and it found that the energy consumption is reduced by 76.31%, 80.21%, and 83.51%, respectively, to the scheme RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power). The average energy consumption is 917.4 J only in the proposed scheme CBMDFBA. Figure 4(d) shows that, when the proposed scheme is compared to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power) with taking task size 2.5Mbps, it resulted in 83.26%, 86.01%, and 88.34% reduction in energy consumption. According to the proposed CBMDFBA scheme, the average energy consumption is 841 J. From Fig. 4, it is clear that energy consumption is increasing with the increasing number of users.
In next scenario, we have considered the 52 MDs and 20 MHz are available in dense areas. We have increased the number of MHs to see the variation in simulation results. In Fig. 5, latency has been calculated with varying numbers of MHs. Figure 5(a) shows that the CBMDFBA scheme lowers latency by 99.86% when compared to the RA(QL-Munkres-TH), 99.88% when compared to the RA(QL-Munkres-Dist) scheme, and 99.71% when compared to the RA(Max-Power) strategy for a 1Mbps task size.
Fig. 5
Latency vs. MHs for (a)({t_s}) = 1Mbps, (b)({t_s}) = 1.5Mbps, (c)({t_s}) = 2Mbps, (d)({t_s}) = 2.5 Mbps.
In the CBMDFBA scheme, the average latency is calculated at 2.27 ms. Figure 5(b) shows that, when comparing proposed scheme with scheme RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power), the latency is decreased by 99.84%, 99.87%, and 99.70%, respectively, with 1.5Mbps. In the proposed CBMDFBA system, the average latency is determined at 3.59ms. Task size of 2Mbps is examined in Fig. 5(c), and it is found that, in comparison to Schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power), the latency in the proposed scheme is decreased by 99.87%, 99.89%, and 99.72%, respectively. In the proposed CBMDFBA system, the average latency is 4.89 ms. Figure 5(d) shows that, when comparing scheme RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power) with proposed CBMDFBA, the latency is decreased by 99.88%, 99.90%, and 99.78%, respectively with task size 2.5Mbps. The proposed CBMDFBA technique yielded an average delay of 5.10 ms. From Fig. 5, it is evident that the latency is decreasing with the increase in the number of helpers, and it also shows better results for larger task sizes.
Fig. 6
Energy usage vs. MHs for (a)({t_s}) = 1Mbps, (b)({t_s}) = 1.5Mbps, (c)({t_s}) = 2Mbps, (d)({t_s}) = 2.5 Mbps.
Figure 6 presents the energy consumption calculation and a comparison of the simulation results. Figure 6(a) shows that the proposed CBMDFBA scheme’s average energy consumption is 955.9 J, 53.91% less than scheme RA(QL-Munkres-TH). Additionally, there was a 60.82% decrease from scheme RA(QL-Munkres-Dist) and a 67.35% decrease from scheme RA(Max-Power). In Fig. 6(a), the task size is considered 1Mbps.
Compared to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power), Fig. 6(b) shows that a task size of 1.5Mbps resulted in a reduction of 68.93%, 74.05%, and 78.37% in energy usage for the proposed scheme. The proposed approach calculates the average energy usage at 943.7 J. When comparing the proposed scheme CBMDFBA to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power), Fig. 6(c) shows that a task size of 2Mbps resulted in a reduction in energy consumption of 78.29%, 81.87%, and 84.89% with schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power) respectively.
Fig. 7
Latency vs. RES computation (a)({t_s}) = 1Mbps, (b)({t_s}) = 1.5Mbps, (c)({t_s}) = 2Mbps, (d)({t_s}) = 2.5 Mbps.
The total average energy consumption in the proposed scheme is 908.3 Joules. Comparing the CBMDFBA to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power) with a task size of 2.5Mbps, Fig. 6(d) shows that the reduction in energy usage is reduced by 79.45%, 82.83%, and 85.69% respectively for schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power) with proposed scheme. The average energy usage is 1036 J for the CBMDFBA scheme. In Fig. 6, it is clearly shown that the energy consumption is increasing with the increasing number of helpers due to the increment of the interference between the devices.
Figure 7 presents simulation results for latency vs. RES computation (cycle/sec). Figure 7(a) shows that the proposed CBMDFBA scheme’s average latency is 2.09ms, 99.88% less than scheme RA(QL-Munkres-TH). Additionally, there is a 99.90% reduction from scheme RA(QL-Munkres-Dist) and a 99.76% reduction from scheme RA(Max-Power). In Fig. 7(a), the task size is considered to be 1Mbps. Figure 7(b) shows that, when comparing the proposed scheme with scheme RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power), the latency is decreased by 99.88%, 99.90%, and 99.75%, respectively with considering task size 1.5 Mbps. In the proposed CBMDFBA scheme, the average latency is determined to be 3.05ms. The task size of 2Mbps is examined in Fig. 7(c), and it is found that, in comparison to Schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power), the latency in the proposed scheme is decreased by 99.86%, 99.88%, and 99.71%, respectively. The average latency in the proposed CBMDFBA system is calculated at 4.61 ms. Figure 7(d) shows that, when comparing scheme RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power) with CBMDFBA, the latency is decreased by 99.86%, 99.88%, and 99.72%, respectively, when the task size selected 2.5 Mbps. The proposed CBMDFBA technique yielded an average delay of 5.93ms. Figure 7 shows that the proposed scheme performs well even if the task size increases. Latency is decreasing; even RES computation is expanding.
Figure 8 presents the energy consumption calculation and a comparison of the simulation results for RES computation. Figure 8(a) shows that the proposed CBMDFBA scheme’s average energy consumption is 1114 J, 46.52% less than scheme RA(QL-Munkres-TH). Additionally, there is a 55.31% reduction from scheme RA(QL-Munkres-Dist) and a 62.76% reduction from scheme RA(Max-Power). In Fig. 8(a), the size of the task is considered 1Mbps. Compared to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power), Fig. 8(b) shows that a task size of 1.5Mbps resulted in a reduction of 66.36%, 71.89%, and 76.58% in energy usage for the proposed scheme.
Fig. 8
Energy usage vs. RES computation for (a)({t_s}) = 1Mbps, (b)({t_s}) = 1.5Mbps, (c)({t_s}) = 2Mbps, (d)({t_s}) = 2.5 Mbps.
The proposed approach determines the average energy usage as 989.4 J. When comparing the proposed scheme CBMDFBA to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power), Fig. 8(c) shows that a task size of 2Mbps resulted in a reduction in energy consumption of 76.65%, 80.49%, and 83.74%. The total average energy consumption in the proposed scheme is 937.7 Joules. Comparing the CBMDFBA to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power) with a task size of 2.5Mbps, Fig. 8(d) shows that the reduction in energy usage is 81.63%, 84.66%, and 87.21%. The average energy usage is 933.4 J per the planned CBMDFBA system. In Fig. 8, it is clearly shown that the energy consumption increases with the increase in the RES computation due to the increase in the interference between the devices.
Fig. 9
latency vs. ES usage for (a)({t_s}) = 1Mbps, (b)({t_s}) = 1.5Mbps, (c)({t_s}) = 2Mbps, (d)({t_s}) = 2.5 Mbps.
Figure 9 presents simulation results for latency vs. ES computation (cycle/sec). Figure 9(a) shows that the proposed CBMDFBA scheme’s average latency is 2.47 ms, 99.86% less than scheme RA(QL-Munkres-TH). There are 99.88% and 99.71% reductions, respectively, to scheme RA(QL-Munkres-Dist) and RA(Max-Power). In Fig. 9(a), the size of the task is considered to be 1Mbps. Figure 9(b) shows that, when comparing the proposed scheme with scheme RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power), the latency is decreased by 99.87%, 99.89%, and 99.72%, respectively with task size 1.5 Mbps. In the proposed CBMDFBA scheme, the average latency is calculated at 3.53ms. The task size of 2Mbps is examined in Fig. 9(c), and it is found that, in comparison to Schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power), latency in the proposed scheme is decreased by 99.86%, 99.89%, and 99.72%, respectively. In the proposed CBMDFBA scheme, the average latency is determined at 4.73 ms. Figure 9(d) shows that, when comparing scheme RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power) with CBMDFBA, the latency is decreased by 99.88%, 99.90%, and 99.75%, respectively with task size 2.5 Mbps. The proposed CBMDFBA technique yielded an average delay of 4.94ms. Figure 9 shows that the proposed scheme performs well even if task size increases. Latency also decreases even with ES computations increasing.
Fig. 10
Energy consumption vs. ES computation for (a)({t_s}) = 1Mbps, (b)({t_s}) = 1.5Mbps, (c)({t_s}) = 2Mbps, (d)({t_s}) = 2.5 Mbps.
Figure 10 presents the energy consumption calculation and a comparison of the simulation results for ES computation. Figure 10(a) shows that the proposed CBMDFBA scheme’s average energy consumption is 974.4 J, which is 53.33% less than scheme RA(QL-Munkres-TH), 61.01% less than scheme RA(QL-Munkres-Dist) and a 67.51% less from scheme RA(Max-Power) for 1Mbps task size. Compared to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power), Fig. 10(b) shows that a task size of 1.5Mbps resulted in a reduction of 68.54%, 73.71%, and 78.09% in energy usage for the proposed scheme. The proposed approach determines the average energy usage as 964.8 J. When comparing the proposed scheme CBMDFBA to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist) and RA(Max-Power), Fig. 10(c) shows that a task size of 2Mbps resulted in a reduction in energy consumption of 75.96%, 79.92%, and 83.26%. The total average energy consumption in the proposed scheme is 982.4 Joules. Comparing the CBMDFBA to schemes RA(QL-Munkres-TH), RA(QL-Munkres-Dist), and RA(Max-Power) with a task size of 2.5Mbps, Fig. 10(d) shows that the reduction in energy usage is 78.44%, 81.99%, and 84.99%. The average energy usage is 1037 J, as per the CBMDFBA. In Fig. 10, it is clearly shown that the energy consumption increases with enlarge in the RES computation due to surge in the interference between the devices.
Fig. 11
Fairness Index with varying (a) Mobile users, (b) mobile helps, (c)({f_{RES}}), (d)({f_{ES}}).
A high fairness index means resources are distributed efficiently in the system. A comparison between all the baseline algorithms and the proposed algorithm is shown in Fig. 11. The figure shows that the proposed algorithm has the highest fairness index.
Figure 12 represents a plot between energy efficiency and edge server computation for the all baseline algorithms and proposed algorithm for varying MUs, MHs, ({f_{RES}})and({f_{ES}}). The figure shows that the energy efficiency is highest for the proposed algorithm compared to baseline algorithms.
Fig. 12
Energy Efficiency with varying (a) Mobile users, (b) mobile helps, (c)({f_{RES}}), (d)({f_{ES}}).
Convergence of the proposed algorithm CBMDFBA is shown in Fig. 13. Average Q-values settle after a certain number of repetitions.
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We conducted a prospective cohort at The King Chulalongkorn Memorial Hospital in Bangkok, Thailand. The study included participants aged ≥ 18 years diagnosed with EGFR-mutated recurrence or advanced-stage NSCLC. EGFR mutation testing was conducted using single gene testing Cobas® mutation test v2. or diver alteration gene panel. All participants received EGFR TKIs (1st -3rd generation) as first-line treatment, according to the provided physician. The pretreatment assessment and response evaluation were conducted as a standard practice of the institute. Demographic characteristics were obtained from the hospital’s electronic medical records. I confirm that all experiments were performed in accordance with the Declaration of Helsinki. The Institutional Review Board of the Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand, approved the study. (IRB No. 894/63 and 580/66). Written informed consent was obtained from all participants. The Bureau of Registration Administration, Ministry of Interior, Bangkok, Thailand, validated the participant’s death date.
Tumor immune microenvironment assessment
Tissue samples were collected upon the diagnosis of advanced-stage non-small cell lung cancer. CD8 Tumor-infiltrating lymphocytes (TILs) and PD-L1 were evaluated by immunohistochemistry. The interpretation was made by one pathologist (S.S.) who was blinded to clinical outcomes. TILs were assessed using immunohistochemistry staining to evaluate the expression of CD8 + T-cells according to the guidelines established by the International TILs Working Group in 2014 17. The evaluation was based on the spatial location of CD8 + TILs, intra-tumoral or stromal. Intra-tumoral CD8 + TILs were defined as CD8 + TILs with direct cell-cell contact with carcinoma cells. The results will be presented as percentages based on tumor cells17. High intra-tumoral CD8 + TILs were defined as intra-tumoral CD8 + TILs ≥ 10%18. PD-L1 was assessed using the Dako FLEX 22C3 and presented by the tumor proportion score19,20. High PD-L1 was defined as PD-L1 TPS ≥ 15% as previously demonstrated the correlation with prognosis21. The definition of inflammatory tumor microenvironment was defined as either PD-L1 TPS ≥ 15% or intra-tumoral CD8 + TILs ≥ 10% as previously reported4,18,21,22.
Blood specimen correction and HLA typing evaluation
Blood samples were collected before the participants started EGFR TKIs treatment in an EDTA tube, centrifuged, and kept at -80 °C until further process. The evaluation of HLA typing was performed by buffy coat using whole-exome sequencing technology. Briefly, DNA from the buffy coat was extracted using a Qiagen blood mini kit following manufacturer protocol. Library preparation was proceeded using SureSelectXT V6 + UTR library prep kit (Illumina, San Diego, CA, USA). The sequencing was conducted using NovoSeq to generate 150 bp paired-end reads at Macrogen Inc. (Seoul, Korea). We analyzed data through bcbio-nextgen version v1.2.923 with target sequences of approximately 90 Mb. Unmapped BAM was generated from Fastq raw data, aligned with hg38 reference using BWA version 0.7.1724, and processed by using the GATK best practice pipeline through Genome Analysis Toolkit recommendation (GATK version 4.1.0.0 including MarkDuplicates, base quality score recalibration, indel realignment, duplicated removal. We identify high polymorphic HLAs using OptiType algorithm25 which shown high accuracy26. The HLA-A was classified into interested and non-interested subtypes based on the binding affinity of the EGFR mutation subtype, which had been previously reported15. The higher binding affinity of the HLA-A subtype represented potential neoantigen. The interested HLA-A was also correlated with favorable prognostic outcomes in resectable NSCLC15. For EGFR L858R alteration, interested HLA-A subtypes were HLA-A*30:01, HLA-A*31:01, HLA-A*33:01, HLA-A*33:03, HLA-A*34:01, HLA-A*66:02, HLA-A*68:01, HLA-A*68:03, HLA-A*68:04, and HLA-A*68:05. While EGFR exon 19 deletion, interested HLA-A subtypes were HLA-A*03:01, HLA-A*03:02, HLA-A*11:01, HLA-A*30:01, HLA-A*34:02, HLA-A*68:01. The presence of one allele of interested HLA-A was considered positive for interested HLA-A.
Sample size calculation
The author was calculated based on Dimou A., et al., who reported that the interesting HLA-A alleles, i.e., HLA-A*11:01, HLA-A*24:02, HLA-A*02:03, HLA-A*33:03, and HLA-A*02:07, exhibited greater binding efficacy to either EGFR L858R or exon 19 deletion peptides. The prevalence of HLA-A*11:01, HLA-A*24:02, HLA-A*02:03, HLA-A*33:03, and HLA-A*02:07 of the Thai population was 26%, 11%, 11%, 11%, and 8%, respectively as previously reported by Satapornpong et al.16. The prevalence of the inflammatory TIME reported by Matsumoto et al. was 13.5%4. We proposed a hypothesis that an interested HLA-A results in a four-fold higher frequency of inflamed TIME compared to uninterested HLA-A subtypes. Using a proportion sample size calculation27to achieve a Type 1 error rate of 5% and a power of 80%, the sample size was calculated to be 74, without continuity correction.
Statistical analysis
Categorical data was analyzed using the Chi-square or Fisher exact test. Continuous data was analyzed using the Mann-Whitney test. The correlation between the HLA-A and either inflammatory TIME or intra-tumoral CD8 TILs was calculated using the Chi-square test. Progression-free survival (PFS) was defined by the time of initiation EGFR-TKIs treatment to the date of objective disease progression or death from any cause. Overall survival (OS) was determined by the time of initiation of EGFR-TKIs treatment to the date of death from any cause. The data was censored on December 31, 2023, for alive or non-progressive disease participants. Multivariate analyses of clinical factors, HLA-A subtype, and tumor immune microenvironment expression level were performed using a Cox proportional hazards model. The Kaplan-Meier method was used to evaluate survival, and the log-rank test was used to evaluate the significance of the difference between groups. The significance level was defined as p-value < 0.05. Statistical analysis was performed using SPSS version 29.0.
This section outlines the deception detection methodology proposed in this study. It discusses the traditional SQM metrics, as well as the MuSD and MuSDA metrics and their threshold calculation methods. Additionally, the computation process of the WMA-BC algorithm is also examined.
Spoofing detection process
The spoofing detection process (Fig. 2) follows a sequential workflow: First, the GNSS receiver demodulates the intermediate frequency (IF) signal. Then, multiple correlators process this signal to generate correlator outputs, which are used to calculate two key metrics—MuSDA and MuSD. These metrics undergo further processing through the WMA-BC algorithm for enhanced detection capability. Finally, the processed metric values (M_{x}) are compared against thresholds (theta_{x}) for spoofing signals to determine whether the received signal is authentic or spoofed.
Fig. 2
Flowchart of WMA-BC for GNSS spoofing detection.
Expressions of the monitoring metrics
Monitoring metrics utilize the correlator output parameter with different composition methods to detect spoofing signals. To understand the metrics, the statistical characteristics must be known. The mean value and noise variance of the metrics can be obtained through calculations, and differences in the signal-to-noise ratio, correlation integral time, and correlator positions can change the noise variance of the metrics. We considered six SQM metrics for comparison: the ELP, ratio, delta, double delta, slope, and double slope metrics. The detailed derivation of the noise variance of each metric is presented in the Appendix.
Table 1 summarizes the definitions and statistical characteristics of the SQM metrics. ({{I_{E} } mathord{left/ {vphantom {{I_{E} } {Q_{E} }}} right. kern-0pt} {Q_{E} }}) and ({{I_{L} } mathord{left/ {vphantom {{I_{L} } {Q_{L} }}} right. kern-0pt} {Q_{L} }}) are the values of the early/late correlator in the in-phase/quadrature correlators, where (E) and (L) are 0.5 and -0.5, respectively. (I_{0}) denotes the output value of the maximum correlator; (I_{{d_{1} }}), (I_{{d_{2} }}), (I_{{ – d_{1} }}) and (I_{{ – d_{2} }}) are the output values of the additional correlators, where the negative sign represents early and no negative sign represents late, (d) denotes the spacing between the correlators and the maximum correlator, and the numbers are used as identifiers. The unit of (d) is chips.
Table 1 Definitions and theoretical statistics of the SQM monitoring metrics.
MuSD and MuSDA metrics
This section describes the NeSD, MiSD, FaSD, MuSD, and MuSDA metrics. Correlators at different locations have distinct offset detection advantages. NeSD, MiSD, and FaSD have complementary properties because the correlators used are at specific locations. However, relying solely on the correlators used by NeSD, MiSD, or FaSD to obtain spoofing detection results is unreliable. MuSD and MuSDA effectively utilize all the different correlators used by NeSD, MiSD, and FaSD by aggregating slope information from correlators at different offsets. This method leverages this diversity to build a more comprehensive signal integrity profile, efficiently increasing the spoofing detection range and preventing, slope, ratio, and ELP from effectively detecting only significant changes at the top or both sides of the correlation peak.
The correlators needed to construct the metrics are shown in Fig. 3. The MiSD correlator (d_{2} = 0.5) chips, which is the (E – L) correlator of the receiver, and (d_{0} = 0) chips, which is the prompt correlator of the receiver. The NeSD and MiSD correlators are located on either side of the (E – L) correlator. The correlator spacing is (d_{1} > d_{2} > d_{3} > d_{0}) , which is determined based on the offset detection advantages of using correlators at different locations.
Fig. 3
Correlator locations for NeSD, MiSD, FaSD, MuSDA and MuSD. The blue dots indicate added correlators, and the red dots indicate the original E, L, P correlators of the receiver.
The (d_{3}) correlator of NeSD is effective for monitoring the ACF near-point distortion by very small code phase difference spoofing and low power spoofing due to its proximity to the prompt correlator. The NeSD can be expressed as
Intermediate code phase difference spoofing causes ACF distortion near the correlator, reducing the spoofing detection capability of NeSD for middle and far distortion points. MiSD utilizes the receiver’s original (E – L) correlator to supplement the NeSD performance. The metric is defined as
Due to correlation limitations, NeSD and MiSD have difficulty detecting small ACF distortions at far points. Thus, to prevent spoofing leakage detection, the far point correlator (d_{1}) is deployed beyond the (E – L) correlator, and the FaSD metric is defined as follows:
MuSD is a joint decision metric that is not directly obtained by the correlators but is jointly determined by the NeSD, MiSD, and FaSD results through logical association operations. The MuSD metric is expressed as follows:
where (H_{SDN}), (H_{SDI}), and (H_{SDF}) are the NeSD, MiSD, and FaSD decision results, respectively.
The MuSDA metric is derived from the receiver’s E, L, and P correlators, as well as additional correlators, using the mean-value difference method, and the MuSDA metric is defined as
MuSD and MuSDA use the same correlator and can therefore be used simultaneously to detect spoofing.
Theoretical thresholds and decision rules for metrics
The threshold for the metrics can be adaptively calculated based on the desired false alarm rate and the statistical characteristics. For satellite navigation signals, the hypothesis testing theory of signal processing is used to identify spoofing signals, with a null hypothesis (H_{0}) indicating that no spoofing signal exists and an alternative hypothesis (H_{1}) indicating that a spoofing signal exists. Assuming that the probability density function of the noise in the case of (H_{0}) follows a normal distribution with mean (mu_{x}) and standard deviation (delta_{x}), the false alarm rate (P_{fa}) is expressed as
where (erfc^{ – 1} (x)) is the inverse function of (erfc).
The false alarm rate can be flexibly adjusted according to the specific requirements of different application scenarios. For instance, high-risk scenarios may tolerate a slightly higher false alarm rate to ensure critical events are not missed, whereas low-risk applications require stricter control over the false alarm rate to avoid unnecessary disruptions.
In the spoofing monitoring process, the decision is divided based on the results of the comparison between the metric measurement and its threshold. The discriminant is as follows:
If the metric measurements exceed the thresholds, there is a spoofing signal; otherwise, there is no spoofing signal.
Weighted moving average bias correction
Noise, spoofing signals and other interference sources all cause transient or short-term fluctuations in metric data. When the spoofed signal operates in the frequency unlocking mode, the relative carrier phases of the real and spoofed signals change over time, leading to significant oscillations in the monitoring metrics and causing unnecessary false alarms33. To reduce the influence of noise interference, we propose the weighted moving average bias correction algorithm, which can be applied to metric data. This approach considers recent data obtained over time, smooths the curve of the monitoring data, reduces the influence of random interference, and improves the robustness and detection performance of the metrics. This subsection describes the computational process and analyzes the simulation results obtained with this method. The traditional weighted moving average algorithm (WMA) expression is
$$P_{t} = beta P_{t – 1} + (1 – beta )M_{t}$$
(20)
where (P_{t}) and (P_{t – 1}) are the predicted values of the monitoring data at moments (t) and (t – 1) , respectively.(M_{t}) is the measured value at moment (t), where (beta) represents the rate of the decay weights, and its expression is
$$beta = 1 – frac{1}{{T_{c} }}$$
(21)
The moving window size in the WMA-BC algorithm is directly related to the receiver’s PIT, as (T_{c}) represents the minimum time interval over which coherent signal accumulation occurs. Therefore, we set the window size equal to the PIT.
During the receiver’s operation, we adopt an adaptive PIT adjustment strategy based on the scene type to optimize system performance. This mechanism determines the current scene type (low-speed/static or dynamic) by analyzing the Doppler rate (Delta {text{f}}) of change and dynamically adjusts the PIT. When the Doppler rate of change is less than or equal to 2 Hz/s, the system identifies the scene as low-speed/static, and the PIT is set to 10 ms to save computational resources and improve response speed. When the Doppler rate of change exceeds 2 Hz/s, the system identifies the scene as dynamic, and the PIT is adjusted to 100 ms to accommodate environments with large frequency fluctuations. The PIT can be expressed as:
The WMA algorithm smooths ACF data by averaging past observations, giving more weight to recent data. While this reduces jitter, it can introduce bias due to small initial values. To address this, we propose the WMA-BC algorithm, which adds a bias correction step to reduce the discrepancy between smoothed and actual values, improving prediction accuracy. The WMA-BC algorithm is as follows:
where (P_{{biased_{t} }}) is the weighted moving average bias correction, (P_{t}) is the predicted weighted moving average.
Experimental results and discussion
Performance of the WMA-BC algorithm
To evaluate the performance of the WMA-BC algorithm, we conducted experiments on the TEXBAT dataset. In the TEXBAT dataset, Cases 2–8 are examples of synchronized spoofing intrusions, while Case 1 is an example of spoofing switching34.
In Case 2, the spoofed signal has a higher power (+ 10 dB) than does the authentic signal, and the spoofers operate in frequency-unlocked mode (the carrier phase difference between the spoofed and authentic signals is not fixed). Case 3 differs from Case 2 in that the spoofed signal operates in frequency-locked mode (the carrier phase difference between the spoofed and authentic signals is fixed), and the power is reduced from 10 dB to 1.3 dB.
We compared the spoofing detection rates of SQM metrics using WMA-BC, WMA, MA-based, and MV-based algorithms, as well as MuSDA and MuSD metrics in Case 2 (Fig. 4(a)) and Case 3 (Fig. 4(b)). The spoofing detection times ranging from 60 to 300 s and the predetection integration time (T_{c} = 100ms), and (P_{fa} le 10^{ – 7}). The detection rate is defined as
$${text{detection rate}} = frac{{text{Samples that exceed the detction threshold}}}{{text{Samples in which deception exists}}}$$
(25)
Fig. 4
(a) Detection rates of the SQM MuSDA and MuSD metrics with the WMA-BC algorithm. (Case 2,(T_{c} = 100ms), and (P_{fa} le 10^{ – 7}) ). (b) Detection rates of the SQM MuSDA and MuSD metrics with the WMA-BC algorithm. (Case 3,(T_{c} = 100ms), and (P_{fa} le 10^{ – 7}) ).
In Case 2, the detection rates of the metrics obtained based on the WMA-BC algorithm are all improved, but the effect differs for different metrics, with the detection rates of the slope, ratio, MuSDA and MuSD metrics significantly improved by more than 70%. As the detection rates of the double slope, delta, double delta, and ELP metrics were originally close to 0, the improvement in the detection rate was limited. Case 3 shows results similar to those of Case 2; the metrics obtained based on the WMA-BC algorithm have higher detection rates, and the detection rates of the metrics improve by approximately 22% to 53%.
Experimental data analysis shows significant performance differences among the four methods in the spoofing detection task. In Case 2 testing, the WMA-BC method performed the best, achieving detection rates of 100% and 81.4% for the MuSDA and slope metrics, respectively, which represents an improvement of 4.8% and 38.3% compared to the WMA algorithm. In comparison, the MA method only reached 66.3% and 26.2%, while the MV method achieved 40.4% and 32.5%. Notably, the MV method completely failed on the ratio metric (0% detection rate), whereas WMA-BC maintained an effective detection rate of 87.1%, which is an improvement of 15.1% compared to WMA.
Further analysis of the Case 3 data reveals that the advantage of WMA-BC is even more pronounced on the slope metric, where its detection rate was more than 30% higher than both the MA and MV methods, with an improvement of about 5% to 20% compared to the WMA method. This method also maintained stable performance on the double slope, delta, MuSDA, and MuSD metrics, demonstrating strong overall performance. In contrast, while the MA method performed reasonably well on the ratio and MuSD metrics, it achieved only a 14.1% detection rate on the delta metric, showing clear performance limitations. The MV method exhibited unbalanced characteristics: it performed excellently on the double slope (63.7%), double delta (63.7%), and ELP (52.6%) metrics but underperformed on key metrics such as ratio (26.2%), MuSDA (5.9%), and MuSD (23.4%).
Overall, WMA-BC demonstrated clear advantages over WMA, MV and MA in terms of performance. The superior performance of WMA-BC is primarily attributed to its weighted computation mechanism, which dynamically adjusts weights over time, effectively enhancing feature differentiation. In contrast, the MA method, due to its simple mean calculation, is prone to losing crucial temporal information. The MV method, which treats all data points within the window equally, cannot implement variance calculations that incorporate features such as exponential decay weights, which are more suited to time-series characteristics, resulting in insufficient performance.
Quantitative analysis demonstrates that WMA-BC significantly enhances the discriminative capability of embedded GNSS systems, achieving more than a 70% improvement in detection rate for key signal metrics. For instance, in Case 2, the Slope metric shows a remarkable increase from 3.6% (raw metric) to 81.4% with WMA-BC, outperforming the MA approach at 26.2% and the MV method at 32.5%.
Despite the computational burden associated with multi-correlator architectures, such as MuSDA/MuSD, which require around 750 M floating-point operations per second (FLOPs), including an overhead of 200 M FLOPs due to additional correlators—WMA-BC introduces only a minimal overhead of 0.50 M FLOPs (just 0.07% of the baseline), along with an additional 48 kB of RAM usage (Table 2).
Table 2 FLOPs and RAM overheads of three algorithms under multi-correlator metrics.
This efficiency makes WMA-BC, along with MuSD and MuSDA metrics, highly suitable for deployment on resource-constrained embedded platforms. For example, when implemented on the TMS320C6748 processor (clocked at 456 MHz with a peak performance of 3648 MFLOPs and a typical power consumption of 1.1W), the added computational load is relatively small, representing less than 5.5% of the total processing capacity. Moreover, WMA-BC maintains linear time complexity O(n), ensuring robust scalability for real-time applications—unlike MV, which has O(n2) complexity and incurs a 13 M FLOP overhead, approximately 72 times greater than that of WMA-BC.
These findings underscore WMA-BC’s unique ability to balance robust spoofing detection with stringent resource efficiency, fulfilling the demanding requirements of real-time GNSS spoofing detection systems in resource-constrained environments.
We calculated and plotted the receiver operating characteristic curves for Case 2 (Fig. 5(a)) and Case 3 (Fig. 5(b)), and performed statistical analysis (Table 3). In the experiments, (P_{d}) and (P_{fa}) were measured by continuously decreasing the metric thresholds. We evaluated the AUC, which is an important parameter for detection performance.
Fig. 5
(a) Comparison of ROC curves for different metrics (Case 2). The solid lines with circles represent curves obtained without the WMA-BC algorithm, the dashed lines with asterisks represent curves obtained based on the WMA-BC algorithm, and the dot with a triangle indicates the curve obtained based on the WMA algorithm. (b) Comparison of ROC curves for different metrics (Case 3). The solid lines with circles represent curves obtained without the WMA-BC algorithm, the dashed lines with asterisks represent curves obtained based on the WMA-BC algorithm, and the dot with a triangle indicates the curve obtained based on the WMA algorithm.
Table 3 The summary of AUC of ROC curves for different metrics.
In Case 2, the AUC values of the metrics obtained based on the WMA-BC algorithm are markedly larger than those of the metrics obtained without the WMA-BC algorithm and those using the WMA algorithm. The AUC area with the WMA-BC algorithm increased by 0.01 to 0.197 compared to the WMA algorithm, and increased by 0.043 to 0.376 compared to the original metrics. Additionally, the MuSDA metric obtained based on the WMA-BC algorithm has an AUC equal to 1, demonstrating a 100% detection rate with no false alarms. In Case 3, the AUC area of the metrics combined with the WMA-BC algorithm increased by 0.01 to 0.072 compared to the WMA algorithm, and the AUC increased by 0.038 to 0.207 compared to the original metrics, which also indicates that these metrics achieved stronger detection capabilities.
In summary, the WMA-BC algorithm-based metrics achieve enhanced spoofing detection rates and superior performance with minimal computational overhead. The GNSS receiver thereby attains improved ROC performance—regardless of whether spoofing signals operate in frequency-locked or frequency-unlock modes, and irrespective of spoofing signal power being higher than or approximately equal to authentic signals.
Spoofing detection experiments with different code phase offsets and carrier phase offsets
To examine the detection performance of various metrics in synchronized spoofing against different code phase offsets and carrier phase offsets (based on the WMA-BC algorithm), we perform experiments by simulating a GPS satellite with the following signal simulation parameters: ({C mathord{left/ {vphantom {C {N_{0} }}} right. kern-0pt} {N_{0} }}) is 45 dB, the C/A code phase difference (mathop tau limits^{ sim } = left| {tau_{s} – tau_{a} } right|) between the authentic signal and the spoofing signal ranges from 0 to 1 chip, with a step size of 0.005 chips, and carrier phase difference (mathop {theta_{s} }limits^{ sim } = left| {theta_{s} – theta_{a} } right|) ranges from 0 to 2π, with a step size of 0.1π, for a total of 4221 grid experiments. Due to the high similarity between spoofing signals and authentic signals in the experiment, and considering the tracking stability of the receiver and the timeliness of spoofing detection, (T_{c}) is 10 ms. The correlators used to obtain the MuSD and MuSDA metrics in the experiments are (d_{1} = 0.9) chips, (d_{2} = 0.5) chips, and (d_{3} = 0.1) chips.
The spoofing detection rates at the experimental grid points are demonstrated in Fig. 6, where the grid color indicates the spoofing detection probability. Each grid represents the detection rate in one experiment, and (P_{fa} le 10^{ – 7}), which can effectively reflect the detection sensitivity of the metrics obtained in each experiment. The detection rates of some metrics decrease in cases with long intrusion times, such as the slope, double slope, delta, and double delta metrics. This is because in the early stage of the spoofing attack, the output values of the early and late correlators change or differ significantly, and the detection difficulty is small. However, in the spoofing attack of the middle or late stages, the change in the output values of the early and late correlators decreases, and the detection difficulty increases. However, the MuSD and MuSDA metrics are obtained using multiple correlators, which can monitor small fluctuations in bilateral slopes at multiple points simultaneously, ensuring high sensitivity and detection rates.
Fig. 6
Detection rate of each metric in different code phase shift and carrier phase shift spoofing experiments. The code phase offset (mathop tau limits^{ sim }) ranges from 0 to 1 chip, and the carrier phase shift (mathop {theta_{s} }limits^{ sim }) ranges from 0 to 2π ((P_{fa} le 10^{ – 7})).
To evaluate the detection performance of the metric more objectively, we evaluated the detection coverage of each metric. The detection coverage is the ratio of the detectable area to the total area in a certain detection region. This value is a more comprehensive reflection of the performance of the metrics. The result of each experiment is 1 unit, and the total number of units is 4221. The detection coverage is defined as
$${text{detection coverage}} = frac{{text{Detectable area }}}{{text{Total area}}}$$
(26)
The detectable area in (26) is the sum of the detectable grid points, and we set a minimum acceptable detection rate of (P_{{d_{min } }}). If (P_{d} le P_{{d_{min } }}), the grid is undetectable, and its grid value is recorded as 0; otherwise, the grid value is set as 1.
Figure 7 shows the detection coverage of each metric when the minimum acceptable detection rate is set to 0.8. The yellow region in the figure represents the detectable region ((P_{d} ge 80%)), and the blue region represents the undetectable region. For both the slope and delta metrics with two correlators and the double slope and double delta metrics with four correlators, the detectable area is smaller than that of the other metrics, and the detection coverage is less than 60%. For the ELP and ratio metrics, undetectable grids are found at their edges or at the center in more places. In contrast, the MuSD and MuSDA metrics have mainly detectable areas, except for the undetectable areas at the edges of (mathop tau limits^{ sim } le 0.055) and (left{ {begin{array}{*{20}c} { , 0 le mathop {theta_{s} }limits^{ sim } le 0.6pi } \ {1.4pi le mathop {theta_{s} }limits^{ sim } le 2pi } \ end{array} } right.). The existence of this blind spot arises from the fact that when the code/carrier phase shift of the deception signal is extremely small, its impact on the correlation peak of the real signal is negligible, typically manifesting as a very weak “boost” or “distortion.”
Fig. 7
Detectable region of each metric in different code phase shift (mathop tau limits^{ sim }) and carrier phase shift (mathop {theta_{s} }limits^{ sim }) spoofing experiments. ((P_{min } = 80%)).
Under the stable operation of the receiver, the receiver experiences fluctuations such as thermal noise and quantization noise, which are very similar to the changes caused by spoofing signals. The adaptive threshold (theta_{x}) we set has a statistical fluctuation offset range given by
When the spoofing signal is extremely similar to the true signal, the metric shift (Delta x) caused by the spoofing signal is very small, and the subtle changes induced by the spoofing signal are easily masked by the inherent noise. The expression is:
$$Delta x = left| {M_{spoofing} – mu_{x} } right|$$
(28)
where (M_{spoofing}) is the measured metric’ value when spoofing is present. Its shift mainly comes from the minor distortions of the signal generator and the additional noise introduced by the spoofing signal itself. When the metric shift (Delta x) caused by the spoofing signal is less than or equal to the statistical fluctuation range (offset) , the receiver cannot effectively detect the spoofing, leading to a detection blind spot.
The detection coverage of the eight detection metrics is summarized (Fig. 8), and the performance of the metrics can be ranked as follows: delta (26.4%) < slope (37.4%) < double delta (52.4%) < double slope (58.3%) < ELP (61.1%) < ratio (73.3%) < MuSDA (95.8%) < MuSD (96.1%). MuSD has the highest detection coverage of 96.1%, and MuSDA has a slightly lower detection coverage than the MuSD metric, with a value of 95.8%, which is approximately 22% to 69% higher than that of the other metrics. These results show that MuSDA and MuSD possess smaller blind zones and outperform the other metrics in terms of code phase offset and carrier phase offset detection.
Fig. 8
Detection coverage of different metrics ((P_{min } = 80%)).
We evaluated the performance of MuSD under different correlator spacing combinations (Table 4). The experimental results show that as (d_{1}) decreases and (d_{3}) increases (with the receiver’s inherent correlator spacing (d_{2} = 0.5)), the detection coverage of MuSD decreases significantly. In this experiment, the configuration (d_{1} = 0.9), (d_{2} = 0.5), and (d_{3} = 0.1) achieved the highest detection coverage (95.8%). This result indicates that this configuration effectively ensures high detection coverage of MuSD across different code phase offset and carrier offset experiments, demonstrating the strongest robustness.
Table 4 The detection coverage of the MuSD metric under different combinations of correlator spacings.
Test with the TEXBAT dataset
To further validate the performance of the metrics (based on the WMA-BC algorithm), we used seven spoofing intrusion cases from the TEXBAT dataset as tests. The battery can be considered the data component of an evolving standard meant to define the notion of spoof resistance for civil GPS receivers. According to this standard, successful detection of or imperviousness to all spoofing attacks in TEXBAT, or a future version thereof, could be considered sufficient to certify a civil GPS receiver as spoof resistant34. It includes dynamic, static, power matching, carrier/code phase matching, and other scenarios (Table 5), among which the challenge of spoofing detection on a dynamic platform is to distinguish spoofing effects from natural fading and multipath.
Table 5 Summary of the TEXBAT dataset.
We detected the signals from 60 to 300 s for each case (240 s in total) and selected the period from 120 to 300 s (spoofing intrusion phase) to calculate the spoofing detection rate. The PIT was set to (T_{c} = 100ms), and the false alarm rate (P_{fa} le 10^{ – 7}).
Through experiments based on the TEXBAT dataset, we visualized the detection rate for each metric (Fig. 9) and performed statistical analysis (Table 6). This result reflects the detection effectiveness in defending against deceptive intrusions. Case 2 is a time-specific attack. The detection rates of the slope, ratio, MuSDA, and MuSD metrics are relatively high, reaching greater than 80%, with MuSDA and MuSD reaching 100%. In contrast, the detection rates of the double slope, delta, double delta, and ELP metrics are not more than 25%. Case 3 is the same as Case 2 except that the power difference between the spoofed and authentic signals is reduced from 10 dB to 1.3 dB, and the spoofers operate in frequency-locked mode. The frequency-locked mode increases the change in the correlator detection value, which is favorable for spoofing detection. The detection rates of the double slope, delta, double delta, and ELP metrics are improved in this case, and the ratio, MuSDA, and MuSD metrics maintain high detection rates of 81.9%, 85.2%, and 94.4%, respectively. Case 4 is the same as Case 3 except that the power difference between the spoofed and authentic signals is reduced (from 1.3 dB to 0.4 dB), and the spoofed signals are position offset-type spoofs. Compared to the results in Case 3, the detection rates of the metrics decrease, while the MuSDA and MuSD metrics still maintain high detection rates of 92.9% and 99.1%, respectively. Case 5 is similar to Case 2, except that the receiver platform is changed from static to dynamic, and obvious changes in the power and phase values occur, making spoofing detection more difficult. The detection rates of the double slope, delta, and double delta metrics are close to 0 in this case. The detection rates of the slope and ratio metrics decrease to 10.3% and 48.7%, respectively, while the MuSDA and MuSD metrics maintain high detection rates of 97.6% and 99.9%, respectively. Case 6 is similar to Case 4, except that the receiver platform is changed from static to dynamic. In Case 6, the detection rates of the various metrics show different degrees of change, with the slope, double slope, delta, double delta, ELP, ratio, MuSDA, and MuSD metrics obtaining detection rates of 20%, 55.3%, 22.5%, 53.6%, 4.9%, 63.7%, 76.1%, and 98.8%, respectively. Case 7 is similar to Case 3, except that a carrier phase alignment strategy is implemented for the spoofed signals. In this case, the delta metric has a detection rate of 0%, the ELP metric has a detection rate of only 1.8%, the slope, double slope, and double delta metrics have detection rates between 50 and 51%, and the MuSDA and MuSD metrics have detection rates of 62.9% and 63.8%, respectively. In Case 8, zero-delay security code estimation and replay attacks are used. In this case, compared to those of Case 7, the double slope and ELP metrics still perform poorly, with detection rates of approximately 0, and the detection rates of the slope and ratio metrics decrease by 13.6% and 13.1%, respectively. The detection rates of the double slope, double delta, MuSDA, and MuSD metrics remain approximately unchanged, with MuSD showing the best detection rate of 63.3%.
Fig. 9
Detection rates of the different metrics based on the TEXBAT dataset (Cases 2 to 8). (T_{c} = 100ms),(P_{fa} le 10^{ – 7}).
Table 6 Summary of detection rates for different metrics based on the TEXBAT dataset.
Overall, among the eight metrics considered in the experiments, the MuSD and MuSDA obtained the best detection performance, showing the highest detection rates in all the experiments. The ratio and slope metrics showed the next best detection performance; although their detection capability was not as good as that of the MuSD and MuSDA metrics, they obtained good detection rates in all the cases. In contrast, the double delta, double slope, delta, and ELP metrics performed poorly, with detection rates close to 0 in some cases. The reason is that MuSD and MuSDA exploit advantages including the offset detection capability of complementary correlators, which comprehensively improves the detection capability of time-type and location-type spoofing signals, such as phase shifts, power suppression, and Earth-centered Earth-fixed coordinate deviations. It also solves the problem in that other metrics are not effective in detecting highly similar spoofing (the code phase, the carrier phase, and power are all very close), improving the spoof detection ability.