Abstract
Connected and software-defined vehicles now rely on edge infrastructure for access, payment, and identity-linked services. Entry and exit at a parking facility are two of the most frequent points at which a vehicle transacts with that infrastructure, and each carries financial and privacy risk: a plate may be read incorrectly, a payment request may arrive twice, the cloud link may drop, and plate-payment records may stay linkable long after the vehicle has left. We describe a cyber-resilient session protocol built for software-defined vehicular edge infrastructure. The vehicle on-board unit exchanges entry, payment, exit, and closure messages with a roadside edge service over IEEE 802.11p. On the edge side, a short-lived pseudonymous token holds the session together; payment and exit invariants are enforced locally, state is cached while the cloud is unreachable, and injected low-confidence automated license-plate recognition (ALPR) events are routed to a review queue. We modeled the control logic in UPPAAL 5.0.0 as a single-session FogController paired with a receipt deadline observer. The verified properties cover duplicate payment exclusion, penalty exclusion after payment and during dispute, exit-induced session closure, synchronization consistency, deadlock freedom, eventual receipt completion, and absence of receipt deadline violations. A single 11,000-s SUMO/OMNeT++/Veins run then instantiated 200 vehicles across four controlled pre-transmission loss cohorts of 0%, 5%, 10%, and 20%. Of those, 159 sessions became active, 135 payment confirmations and 132 receipts arrived, and 74 sessions completed end to end. Mean application-level response times were roughly 50 ms for token, payment, duplicate payment, and exit responses, and 100 ms for receipts. Injected fault paths comprised 19 uncertain-ALPR events, 8 duplicate payment rejections, 10 fog-cloud outages with a configured 10-s recovery interval, and 5 exit mismatches with a configured 5-s review interval. The two evaluations give complementary formal safety and wireless execution evidence. They also show that one-shot messaging without retransmission limits both completion and token-revocation reliability under loss.
1 Introduction
In most smart-city work, parking is filed under services. For a connected or software-defined vehicle, it functions as a vehicle-to-infrastructure (V2I) transaction, one that repeats every time the driver arrives or leaves. The vehicle and the roadside infrastructure communicate with each other across many different parameters in one session, including time, location, access rights, payment, and identity evidence. The control path must respond quickly enough to raise a gate. It must remain consistent when the radio link or the cloud connection fails. It should also avoid building a durable record that ties a driver to a plate and a payment history. These three demands pull against one another.
Automated license-plate recognition (ALPR), occupancy sensing, mobile applications, and cloud payment services are already being used in smart parking systems. The failure modes at the transaction layer receive far less attention. A violation may be recorded when a plate reading is uncertain. A payment request sent twice can turn into a billing dispute. A session can get stuck halfway through if a payment or an exit response is lost. A plate that stays attached to a payment account creates a mobility-finance trail. These effects remain small in an isolated installation of camera and barrier. They grow once parking becomes a connected-vehicle service.
This problem is well addressed by software-defined vehicular networking and vehicular edge computing, as the session logic that must be quick can sit close to the vehicle and the access point. In our design, the vehicle on-board unit (OBU) requests a short-lived token and then exchanges session messages with the edge application located at the roadside. The edge holds the authoritative view of the active session. It verifies its invariants before committing to a payment or an exit decision; it maintains its records locally when the cloud is not available; and it forwards uncertain evidence to review.
The pattern generalizes beyond parking. Connected aerial vehicles, autonomous delivery drones, charging stations, and edge-managed vertiports must all address temporary authorization, local sensing, confirmation that a payment or service went through, and a safe method for handling evidence they cannot fully trust. For these reasons, we choose to use a ground-vehicle parking facility as a bounded case study. The pattern could be adapted to aerial vehicles, which we leave as future work and present here as such.
We make four contributions. The first is an SDV-to-edge session architecture in which the OBU and the roadside edge application exchange pseudonymous entry, payment, exit, and closure messages. The second is an ALPR uncertainty-aware decision policy that forwards injected low-confidence or inconsistent recognition events to entry or exit review, while the automatic penalty transition is blocked by a guard. Third, we verify a single-session control model in UPPAAL, introducing a dedicated observer for receipt deadlines, thereby explicitly stating the timing claim. Fourth, we run the request-response exchange over an actual IEEE 802.11p stack in SUMO/OMNeT++/Veins, across four cohorts of pre-transmission message loss and report the message delivery, response time, lifecycle progression, fault handling, and edge-cache estimates.
The remainder of this article is organized as follows. Section 2 reviews the work on smart parking, ALPR uncertainty, privacy, vehicular edge computing, and formal verification. Section 3 outlines the architecture, threat model, session protocol, UPPAAL model, and co-simulation setup. Section 4 summarizes the formal and communication results, Section 5 deals with the implications and trade-offs, Section 6 states the limitations and what we plan to do next, and Section 7 concludes the article.
2 Related work
2.1 Smart parking systems and operational limitations
Smart parking architectures encompass bay discovery, fee calculation, navigation, sensing, and integration with mobile services (; ; ), while fog-supported designs reduce reliance on a remote cloud for access decisions that cannot wait (; ). The session itself is less examined. This collection of work is dominated by occupancy, recognition accuracy, and service automation (), while explicit invariants for duplicate payment, receipt completion, dispute handling, outage recovery, and final closure are rarely stated.
A parking interaction is a stateful, financial, and access-control transaction. We are studying the protocol that runs at the edge. It separates routine pseudonymous control from long-term identity storage, and it allows a selected set of unsafe transitions to be checked formally. Occupancy sensing and payment application design are outside the scope of the work.
2.2 ALPR uncertainty, adversarial handling, and decision policy
Deep-learning detectors and OCR pipelines have improved ALPR performance (), and they now run on resource-constrained edge devices (). Recognition stays fragile in the ways it has always been fragile: lighting, camera angle, dirt, occlusion, blur, reflective plates, and domain shift all degrade it. When the output of that pipeline is used to authorize a payment or open an exit gate, the confidence value attached to it should be handled as evidence and given proportionate weight.
Adversarial plate perturbations () strengthen the case for defensive decision logic. Our contribution at this layer is a protocol policy: events that are low-confidence, noisy, inconsistent, or otherwise suspicious are kept as evidence and passed to review. Building or benchmarking an ALPR model falls outside the present scope. In the experiment reported below, these events are injected deterministically, and we evaluate no image dataset and no recognition model.
2.3 Privacy and non-repudiation in parking transactions
A parking record ties together a user account, payment details, a place, and a time, and a run of them becomes a mobility-finance history. approach this through privacy-preserving parking services designed against European data-protection requirements; blockchain-based schemes approach the topic from the perspective of auditability and integrity (; ). FedVR360 () offers a considerably stronger privacy mechanism for vehicular edge learning, combining federated learning with Rényi differential privacy. Our problem is narrower than either. We are trying to reduce direct-identifier exposure while a transaction is live, using short-lived pseudonymous session identifiers.
Anonymity and unlinkability lie outside what the design proves. Under defined exception conditions, the cloud, or an authorized operator, can still tie a token back to a registered profile. Our privacy claim is correspondingly limited: pseudonymization reduces identity exposure and keeps routine edge control separate from long-term records. Differential privacy guarantees and ledger-based auditability are different claims.
2.4 SDV edge infrastructure
Software-defined vehicular networks bring programmable networking together with vehicular communication (), and vehicular edge computing moves selected control and computation close to the vehicles themselves (). Our parking service follows that split: time-sensitive session state stays at the roadside edge, while registration, settlement, and long-term audit stay in the cloud.
take up the trade-off between security and latency in the Internet of Vehicles (IoV), integrating blockchain with edge computing and then optimizing away the latency that consensus and encrypted processing introduce. Our design puts no blockchain transaction behind a gate event, relying on a local session table and a receipt record. Architectural complexity drops, as does the strength of the guarantee: we have no distributed-ledger consensus and no equivalent immutability.
2.5 Formal verification of IoT and vehicular edge protocols
A simulation covers the executions it happens to run. Establishing that no unsafe state is reachable calls for a different instrument. UPPAAL timed automata have been applied across a wide range of verification problems (), including the formalization of access-control models for IoT environments (). They fit this controller because the properties at stake (duplicate billing, penalty exclusion, receipt response, synchronization, exit closure, and freedom from deadlock) are all state and timing properties. The executable model abstracts away the internals of the ALPR, payment provider, cryptographic, cloud, and barrier components; that abstraction is deliberate.
We do not claim novelty for the individual components, nor for their combination alone. The specific contribution is that the uncertainty-aware ALPR policy and the payment and exit invariants are expressed as machine-checkable properties and discharged against a timed-automata model, and that the same protocol path is then executed over a wireless vehicle-edge link. Table 1 sets this against the closest existing protocols on primary focus, vehicle orientation, uncertainty, and privacy handling, and the formal or session-level guarantee each provides. UPPAAL and SUMO/Veins run independently, with no coupling at runtime. One explores every reachable state of a single parameterized session controller; the other runs message exchanges for many moving vehicles under a fixed radio configuration and controlled loss cohorts.
TABLE 1
| Study | Primary focus | Vehicle/SDV orientation | Uncertainty/privacy handling | Formal/session guarantee |
|---|---|---|---|---|
| IoT and fog smart-parking latency | Infrastructure centered | Not central | No formal session invariants | |
| Fault-tolerant fog scheduling | Transportation edge | Not central | Fault tolerance, not parking session correctness | |
| Consortium-blockchain parking privacy | Infrastructure centered | Ledger-based privacy/audit | No timed session model | |
| YOLOv8 ALPR on edge devices | Perception component | Recognition accuracy | No payment/session verification | |
| IoT parking with ALPR and payment | Infrastructure centered | ALPR performance | No duplicate payment or penalty invariant | |
| Fog-blockchain autonomous parking | Autonomous vehicle parking | Not central | Blockchain/fog security; no UPPAAL session model | |
| GDPR-compliant parking privacy | Service privacy | Legal/privacy architecture | No communication-aware session verification | |
| Federated vehicular edge learning | Connected-vehicle edge | Differential privacy and attack evaluation | Learning/privacy guarantees, not parking transactions | |
| Blockchain-encrypted IoV edge latency | IoV edge computing | Security-latency trade-off | Latency optimization, not parking session invariants | |
| This study | SDV-to-edge parking session protocol | Vehicle OBU and roadside edge | Pseudonymization and injected ALPR uncertainty review | UPPAAL invariants plus IEEE 802.11p execution |
Comparison with related smart parking, privacy, vehicular edge, and formal session studies (Source: Author).
3 Materials and methods
3.1 Proposed infrastructure architecture
The system is a software-defined edge session protocol serving both registered and guest vehicles. A registered vehicle may keep a cloud profile and a payment account; a guest vehicle uses a temporary transaction path: a web link, a kiosk, a QR code, or a mobile application. Either way, the active session lives at the roadside edge service, which performs the decision checks locally.
Six functional layers make up the architecture: (1) the vehicle/SDV layer, holding the driver interface, the OBU, and the session application; (2) sensing and actuation (ALPR cameras, occupancy or gate sensors, and the physical barrier); (3) the V2I communication layer; (4) the edge/fog session service; (5) cloud registration and payment services; and (6) audit and dispute handling. Our final Veins implementation instantiates the vehicle application together with a single roadside unit (RSU) edge application, and passes entry, payment, exit, and closure messages between them through the IEEE 802.11p stack. Figure 1 shows the layered architecture, and Table 2 lists each component and its function.
FIGURE 1
TABLE 2
| Layer | Component | Function in revised architecture |
|---|---|---|
| Vehicle/SDV layer | Connected-vehicle OBU/SDV application | Sends entry, payment, exit, and closure requests; receives and stores the short-lived token and responses |
| Registered or guest user interface | Uses a linked profile or temporary transaction path for payment and dispute interaction | |
| Sensing and actuation layer | Entry/exit ALPR cameras | Provide recognition evidence to the uncertainty-aware policy; not implemented as an image model in the final simulation |
| Bay, gate, and barrier components | Provide occupancy or sequence evidence and physical actuation; outside the verified implementation boundary | |
| V2I communication layer | IEEE 802.11p radio and roadside unit | Carries smart parking request-response messages between vehicle and RSU applications |
| Edge/fog session layer | Session orchestrator | Maintains local state, enforces payment and exit guards, and schedules responses |
| Uncertainty and dispute policy | Routes injected low-confidence or mismatch evidence to review | |
| Token manager and local cache | Issues regular or temporary tokens, estimates active-state footprint, and attempts revocation after closure | |
| Cloud and payment layer | Registration and payment services | Abstractly confirms payment and stores long-term records after synchronization |
| Audit and dispute layer | Receipt and review service | Records receipts and resolves uncertainty, payment, or exit ambiguity |
System components and functions in the revised SDV-to-infrastructure architecture (Source: Author).
Inside the edge application is a per-vehicle session table carrying token, active, paid, receipt, exit, outage, and mismatch state. From that table, the application issues a regular token or a temporary token where an uncertainty event has been injected; it turns down a second payment request once the session is marked paid; it schedules synchronization after a configured cloud outage; and it authorizes exit only when the local payment and receipt checks pass. Once the vehicle reaches SessionClosed, a best-effort closure notice goes back to ask for the token to be revoked.
3.2 Threat model, trust boundaries, and token lifecycle
We assume an adversary who can replay or duplicate application messages, drop or delay messages, present plate and token evidence that does not agree, obscure or perturb a plate, steal a session token, and cut fog-cloud connectivity. Under that assumption, the vehicle-to-RSU wireless channel and the cloud link are both untrusted transport domains. The formal and simulation models do assume the proper functioning of the FogController/RSU application, the local clock, session state storage, and the cryptographic primitives. A fully compromised OBU, RSU operating system, cloud administrator, payment provider, camera, or barrier controller is outside of the verified trust boundary.
Tokens are intended to be short-lived and bound to a particular session. The duplicate payment state is rejected at the edge, and once the session has closed locally, the vehicle sends a SessionCloseNotice for the RSU to mark the token revoked. The final experiment uses one-shot messages, with no acknowledgment and no retry, so even if the session is closed cleanly on the vehicle side, the RSU may still have a live token. This is explicitly described in the results.
3.3 Session tokenization and privacy model
An identifier for each parking interaction is used in place of the plate and the associated payment account in the routine edge key. The edge creates a short-lived token once detection and the uncertainty decision are complete. For a registered vehicle, the cloud could map the token to the long-term profile, and the token for a guest vehicle would simply identify the temporary transaction path.
While a session is active, its edge record carries the token, vehicle hint, payment state, receipt state, dispute state, synchronization state, and the lifecycle flags. The Veins implementation also stores the number of active sessions and a serialized-record byte estimate. That estimate is reproducible and measures representation size. The amount of C++ heap memory is not reported and is a separate quantity. The scheme reduces routine use of direct identifiers, and formal anonymity and unlinkability are distinct attributes that remain unproven.
3.4 ALPR reliability index and adversarial handling
For a plate recognition event, let Ri be a conceptual edge-side reliability score. It could rely on the confidence level of the ALPR model, the quality of the image, the agreement of the auxiliary gate sensors, and whether the reading is consistent with the current token and the direction of travel we would expect. In this experiment, images are not used to calculate Ri. Selected vehicle identifiers trigger low-confidence protocol events deterministically instead.
A simplified representation is
The suspicion term grows with evidence of obstruction, odd texture, sensor disagreement, or repeated recognition failure on the same vehicle. These are architectural requirements of a perception implementation that we have yet to build; nothing in this dataset-free experiment measures them.
Evidence that the policy deems reliable enough maps to TokenIssued or ExitVerified. Uncertain entry evidence is passed on to EntryDisputeReview and may come back as TemporaryTokenIssued, while uncertain exit evidence is passed on to ExitDisputeReview and then to ManualResolution. A penalty transition is never authorized when confidence is low.
The protocol then reacts defensively. Uncertain evidence is logged, irreversible financial or penalty action is not taken, and the review path is taken instead. Our claims involve the correctness of that route of decision making, not the accuracy or robustness of the underlying ALPR neural network.
3.5 Parking session state model
Every parking interaction is a finite-state session. The normal sequence runs Idle, EntryRequest, ALPRChecked, TokenIssued, SessionActive, ParkingStarted, PaymentConfirmed, ReceiptGenerated, ExitRequested, ExitVerified, and SessionClosed, followed by TokenRevoked once a closure notice reaches the RSU. VehicleDetected and PlateCaptured are conceptual sensing steps that Figure 2 shows collapsed into EntryRequest. Branching off the normal sequence are the exception pathways: LowConfidenceALPR, EntryDisputeReview, TemporaryTokenIssued, DuplicatePaymentIgnored, NetworkOutage, SyncPending, CloudSynchronized, ExitMismatch, ExitDisputeReview, ManualResolution, and the constrained penalty path through PenaltyEligible, PenaltyIssued, and SessionClosedWithPenalty. Figure 2 shows the session lifecycle, and Table 3 defines every state.
FIGURE 2
TABLE 3
| State | Description |
|---|---|
| Idle | No active parking session exists |
| VehicleDetected | Vehicle is detected at entry (conceptual sensing state) |
| PlateCaptured | ALPR evidence is captured (conceptual external component) |
| EntryRequest | The vehicle sends an entry request to the roadside edge service |
| ALPRChecked | The uncertainty-aware policy evaluates the supplied evidence |
| TokenIssued | A regular short-lived session token is issued |
| LowConfidenceALPR | An injected uncertain-recognition event is active |
| EntryDisputeReview | Entry-side uncertainty is routed to review |
| TemporaryTokenIssued | A temporary token is issued after the uncertainty path |
| SessionActive | The vehicle has received a token and the local session is active |
| ParkingStarted | The tokenized vehicle reaches the parking area in SUMO |
| PaymentConfirmed | The first payment request has been accepted |
| DuplicatePaymentIgnored | A repeated payment request is rejected because the session is already paid |
| ReceiptGenerated | A receipt response is generated for the accepted payment |
| NetworkOutage | The abstract fog-cloud connection is unavailable |
| SyncPending | The local record is retained while synchronization is pending |
| CloudSynchronized | The configured recovery event restores synchronization |
| ExitRequested | The vehicle sends an exit-verification request |
| ExitMismatch | Injected exit evidence does not match the token/session |
| ExitDisputeReview | The mismatch is routed to review |
| ManualResolution | The configured review path resolves the mismatch |
| ExitVerified | The RSU authorizes exit after local state checks |
| SessionClosed | The vehicle reaches local session closure |
| SessionClosedWithPenalty | The session terminates through the constrained penalty path |
| TokenRevoked | The RSU receives a closure notice and marks the token revoked |
| PenaltyEligible/PenaltyIssued | Conceptual/modeled penalty path constrained by payment, low ALPR, and dispute guards; no separate identityResolved or violationConfirmed variables are verified |
Parking session state definitions (Source: Author).
A handful of transitions are ruled out by construction. Neither a confirmed payment nor an active dispute can lead to a penalty. A duplicate request cannot push paidCount past one. An exit mismatch cannot complete the exit before dispute mode is entered. A verified exit clears the active-session flag. Receipt completion and synchronization carry liveness and consistency properties on top of these.
3.6 Formal verification with UPPAAL
We ran the formal verification in UPPAAL 5.0.0 (revision 714BA9DB36F49691) on Microsoft Windows 11 Home. The executable system includes two templates, FogController and ReceiptObserver, declared as “system FogController, ReceiptObserver.” FogController represents a single parameterized parking session and works on paidCount, paymentDone, receiptDone, waitingReceipt, rclk, lowALPR, disputeMode, penaltyDone, exitMismatchFlag, exitDone, sessionActive, networkDownFlag, syncPending, syncCompleted, and synced. ReceiptObserver maintains its own clock, obsClk, and synchronizes on paymentConfirmedEvt and receiptGeneratedEvt. Figure 3 shows the structure of the verified model.
FIGURE 3
When the payment is confirmed, the observer goes to Waiting. Transitions go to ReceiptObserved when either of the receipt-producing controller edges emits receiptGeneratedEvt, and they enter DeadlineMissed if obsClk passes five model time units. The queries we ask relate to safety, reachability, liveness, bounded response, synchronization, and deadlock. The model verifies the controller’s behavior with respect to abstract events. ALPR/OCR internals, token cryptography, payment provider correctness, the cloud implementation, camera hardware, and the physical barrier all lie outside it. In SUMO/Veins, the concurrency of multiple vehicles is handled, while UPPAAL instantiates a single session.
3.7 SUMO/Veins co-simulation setup
The co-simulation ran on OMNeT++ 6.3.0 with Veins 5.3.1 (), under WSL on a Windows 11 host. SUMO generated 200 vehicles, 50 parking bays, two entry gates, and two exit gates across an 11,000-s horizon, with a single RSU placed at (178, 67, 3) m. We fixed the IEEE 802.11p configuration at 20 mW transmit power, 6 Mbps bitrate, a −98 dBm noise floor, a −110 dBm minimum power level, a SimplePathlossModel with exponent 2.0, and a 5.890 GHz center frequency, with propagation delay enabled. Periodic beacons and vector recording were switched off. The OMNeT++ seed was 20260802; the SUMO launch seed was 0. Figure 4 shows the co-simulation setup.
FIGURE 4
Vehicle identifiers assigned each vehicle to one of four controlled, independent pre-transmission loss cohorts at 0%, 5%, 10%, and 20%. We applied the injection to smart parking requests and RSU responses before sendDown; anything left undropped went through the Veins IEEE 802.11p stack as normal. Separate CSV logs captured attempted messages, injected drops, packets handed to IEEE 802.11p, peer receptions, response round-trip time, lifecycle states, fault states, and cache snapshots. This is a single reproducible sensitivity run. Fading, C-V2X, high congestion, and multi-seed statistics lie beyond its design.
4 Results
4.1 UPPAAL verification outcomes
Every UPPAAL query in Table 4 came back satisfied. Duplicate charging is excluded by the invariant A[] paidCount <= ≤1. Penalty after a confirmed payment and penalty during review are excluded by A[] paymentDone imply !penaltyDone and A[] disputeMode imply !penaltyDone. Exit safety rests on three properties: A[] exitMismatchFlag imply disputeMode, A[] exitMismatchFlag imply !exitDone, and A[] exitDone imply !sessionActive.
TABLE 4
| Property | UPPAAL query | Result | Interpretation |
|---|---|---|---|
| Session closure reachable | E<> FogController.SessionClosed | Satisfied | The normal lifecycle can reach closure |
| Cloud recovery reachable | E<> FogController.CloudSynchronized | Satisfied | The outage recovery path is executable |
| No duplicate payment | A[] paidCount ≤ 1 | Satisfied | The model never records more than one accepted payment |
| No penalty after payment | A[] paymentDone imply !penaltyDone | Satisfied | A paid session cannot be penalized |
| No penalty during dispute | A[] disputeMode imply !penaltyDone | Satisfied | Review prevents penalty completion |
| Low ALPR does not penalize | A[] lowALPR imply !penaltyDone | Satisfied | Uncertainty alone cannot produce penalty |
| Exit mismatch enters dispute | A[] exitMismatchFlag imply disputeMode | Satisfied | Mismatch activates dispute mode |
| Mismatch cannot complete exit | A[] exitMismatchFlag imply !exitDone | Satisfied | Exit remains incomplete while mismatch is active |
| Exit clears active session | A[] exitDone imply !sessionActive | Satisfied | Verified exit clears the active-session flag |
| Outage is unsynchronized | A[] networkDownFlag imply !synced | Satisfied | The outage flag excludes synchronized state |
| Pending sync is unsynchronized | A[] syncPending imply !synced | Satisfied | Pending records remain marked unsynchronized |
| Sync completion restores consistency | A[] syncCompleted imply synced | Satisfied | Completed synchronization restores the synced flag |
| Receipt follows payment | paymentDone -- receiptDone | Satisfied | Every confirmed payment state eventually reaches receipt completion |
| Observer starts | E<> ReceiptObserver.Waiting | Satisfied | The deadline observer is non-vacuously activated |
| Receipt success reachable | E<> ReceiptObserver.ReceiptObserved | Satisfied | The observer can record receipt completion |
| No receipt deadline miss | A[] not ReceiptObserver.DeadlineMissed | Satisfied | No reachable run exceeds the five-time-unit deadline without receipt |
| Receipt clock constraint | A[] waitingReceipt imply rclk≤5 | Satisfied | The controller waiting state does not coexist with rclk above five |
| Deadlock freedom | A[] not deadlock | Satisfied | The two-template model has no reachable deadlock |
Final UPPAAL verification results (Source: Author).
Receipt liveness no longer rests on the clock constraint alone. The leads-to query paymentDone receiptDone was satisfied. Reachability queries confirmed that both ReceiptObserver.Waiting and ReceiptObserver.ReceiptObserved are executable, and A[] not ReceiptObserver.DeadlineMissed held. A[] waitingReceipt imply rclk <= 5 constrains the controller’s receipt-waiting clock, but we read it only as a state-clock constraint and nothing stronger.
The network properties A[] networkDownFlag imply !synced, A[] syncPending imply !synced, and A[] syncCompleted imply synced were all satisfied, as were reachability of FogController.CloudSynchronized and FogController.SessionClosed and global freedom from deadlock. All of this holds for the single-session timed-automata abstraction. None of it speaks to the internal correctness of the external sensing, payment, cryptographic, cloud, or actuation components.
4.2 Mobility and communication-aware simulation results
All 200 vehicle applications were initialized in the 11,000-s run. SUMO inserted all 200 vehicles and reported none still active after a simulation time of 9,896 s. Protocol-layer counts came out lower: 159 vehicles received a regular or temporary token and entered SessionActive, and 159 recorded ParkingStarted; 135 vehicles received PaymentConfirmed, and 132 received ReceiptGenerated; 74 vehicles received ExitVerified and reached local SessionClosed. One-shot message loss with no retransmission behind it accounts for the gap between physical trip completion and protocol completion because the mobility horizon itself was long enough. Table 5 reports the full configuration and the protocol outcomes.
TABLE 5
| Category | Metric/event | Value | Interpretation |
|---|---|---|---|
| Environment | Host and execution | Windows 11 Home; WSL | Linux-based OMNeT++/Veins execution on Windows host |
| Environment | Simulation software | OMNeT++ 6.3.0; Veins 5.3.1 | Final communication environment |
| Reproducibility | Seeds | OMNeT++ 20260802; SUMO 0 | Single fixed-seed run |
| Scenario | Simulation horizon | 11,000 s | All 200 SUMO vehicles inactive by 9,896 s |
| Scenario | Vehicles/capacity/gates | 200/50 bays/2 entry +2 exit | Fixed parking facility |
| Radio | RSU position | (178, 67, 3) m | Midpoint placement covering both entry gates |
| Radio | Frequency/bitrate/transmit power | 5.890 GHz/6 Mbps/20 mW | Fixed IEEE 802.11p configuration |
| Radio | Noise/path loss | −98 dBm noise floor; alpha = 2.0 | SimplePathlossModel; propagation delay enabled |
| Radio | Periodic beacons | Disabled | No background beacon-load experiment |
| Loss design | Controlled cohorts | 0%, 5%, 10%, 20% | Independent pre-transmission message-loss injection |
| Lifecycle | Applications initialized | 200 | All planned vehicle applications were instantiated |
| Lifecycle | Regular/temporary tokens received | 142/17 | 159 sessions became active |
| Lifecycle | ParkingStarted | 159 | Only tokenized sessions entered the protocol parking state |
| Lifecycle | PaymentConfirmed/ReceiptGenerated | 135/132 | Three receipt responses did not reach vehicles |
| Lifecycle | ExitVerified/SessionClosed | 74/74 | End-to-end local lifecycle completion |
| Fault path | LowConfidenceALPR/EntryDisputeReview | 19/19 | Injected uncertainty events entered review |
| Fault path | DuplicatePaymentIgnored | 8 | Second payment requests were rejected |
| Fault path | NetworkOutage/CloudSynchronized | 10/10 | Configured 10-s recovery path completed |
| Fault path | ExitMismatch/ManualResolution | 5/5 | Configured 5-s review path completed |
| State overhead | Peak active sessions/serialized cache | 176/6,118 bytes | Representation size estimate, not heap memory |
| Closure reliability | TokenRevoked at RSU | 5 | Only five best-effort closure notices reached the RSU |
Final SUMO/Veins configuration and protocol outcomes (Source: Author).
Response-side end-to-end success fell from 95.58% in the 0% injected-loss cohort to 91.52%, 86.40%, and 75.25% in the 5%, 10%, and 20% cohorts, respectively. Completed sessions dropped alongside it: 27/50 (54%), 24/50 (48%), 16/50 (32%), and 7/50 (14%). Request-side end-to-end success stayed between 73.08% and 77.99%. Channel delivery, measured after excluding the deliberate drops, was not monotonic across cohorts because each cohort produced a different mix of entry, payment, exit, and closure opportunities: a message lost early stops the later stages from ever being attempted. Mean round-trip time came to roughly 0.05048 s for token, payment, duplicate payment, and exit responses, and 0.10048 s for receipts. Table 6 gives the per-cohort delivery and completion counts, and Table 7 gives the aggregate response times.
TABLE 6
| Group | Injected loss | Requests attempted/received | Request channel delivery | Request end-to-end | Responses attempted/received | Response end-to-end | Completed sessions |
|---|---|---|---|---|---|---|---|
| 0 | 0% | 176/136 | 77.273% | 77.273% | 181/173 | 95.580% | 27/50 (54%) |
| 1 | 5% | 159/124 | 80.519% | 77.987% | 165/151 | 91.515% | 24/50 (48%) |
| 2 | 10% | 129/96 | 83.478% | 74.419% | 125/108 | 86.400% | 16/50 (32%) |
| 3 | 20% | 104/76 | 90.476% | 73.077% | 101/76 | 75.248% | 7/50 (14%) |
Message delivery and session completion by controlled loss cohort (Source: Author).
TABLE 7
| Response type | n | Mean RTT (s) | Observed minimum (s) | Observed maximum (s) |
|---|---|---|---|---|
| TokenIssued | 142 | 0.050481 | 0.050470 | 0.050794 |
| TemporaryTokenIssued | 17 | 0.050479 | 0.050471 | 0.050483 |
| PaymentConfirmed | 135 | 0.050482 | 0.050473 | 0.050824 |
| ReceiptGenerated | 132 | 0.100483 | 0.100472 | 0.100489 |
| DuplicatePaymentIgnored | 8 | 0.050478 | 0.050473 | 0.050485 |
| ExitVerified | 74 | 0.050481 | 0.050473 | 0.050486 |
Aggregate application-level response time in the final run (Source: Author).
“Channel delivery” divides peer receptions by messages passed to the IEEE 802.11p stack after excluding deliberately injected drops. “End-to-end” divides peer receptions by all attempted messages. Cohort comparisons are descriptive because earlier failures change the number and type of later-stage message opportunities.
4.3 Fault and dispute behavior
The RSU logged 19 injected LowConfidenceALPR and EntryDisputeReview events, of which 17 temporary token responses were successfully transmitted to a vehicle. Eight duplicate payment rejections were received. Ten NetworkOutage events ran through SyncPending to CloudSynchronized once the configured 10-s recovery interval had elapsed, and five ExitMismatch events passed through ExitDisputeReview to ManualResolution after the configured 5-s review interval. Edge state peaked at 176 active sessions, with a peak serialized cache estimate of 6,118 bytes, or roughly 34.8 serialized bytes per active record. Closure notification performed poorly: although 74 vehicles reached local SessionClosed, only five SessionCloseNotice messages arrived at the RSU and produced TokenRevoked, which shows that best-effort notification does not survive loss. Figure 5 traces the lifecycle counts across the run.
FIGURE 5
The two tools supply different kinds of evidence. UPPAAL establishes the stated invariants and timing properties for the abstract single-session controller. The co-simulation shows that the matching request, response, uncertainty, outage, dispute, and duplicate payment paths execute over IEEE 802.11p. A simulation trace could still violate a formal property, and the co-simulation cannot rule that out. The two tools have no dynamic coupling.
5 Discussion
We have developed an edge-resident session protocol for connected vehicles. The OBU participates in negotiating the token, the RSU application holds the programmable session state, and the ALPR output enters the system as uncertain evidence bound by protocol constraints. Our previous evaluation focused only on events. The current implementation improves on it by pushing smart parking requests and responses through the Veins IEEE 802.11p stack.
The state at the edge provides continuity during short cloud outages: the session survived in simulation, and synchronization completed once the configured recovery interval had passed. The 0.05 s configuration for the RSU processing time, combined with the 0.10 s configuration for the receipt generation time, directly yields a small communication overhead on the successful response paths. These are simulation parameters plus wireless execution time. The numbers would differ for a deployed payment provider or cloud service.
The privacy contribution is selective pseudonymization. Routine edge decisions operate on a short-lived token and a minimal session record, while long-term registration and audit sit apart from the identifier used at the gate. FedVR360 has more formal privacy with differential privacy, and GDPR-oriented parking work reaches further into legal compliance than we do. The one quantity our design does report is the operational edge-state footprint, which is a peak serialized estimate of 6,118 bytes across 176 active sessions.
The loss cohorts reveal an engineering compromise. The safety checks may remain accurate while availability degrades underneath them. If a token, payment, receipt, exit, or closure message is lost, the session halts without causing duplicate billing or an unsafe formal transition. Safety holds even as the service becomes less useful. This effect is directly reflected in the token-revocation counts, and a broader RSU coverage, persistent revocation queues, or acknowledgments will be required before deployment. Our results establish the feasibility of the protocol path and locate its resilience gaps. The fixes above would be needed for production readiness.
6 Limitations and future work
Five limitations bound what we can claim. The UPPAAL model represents one parameterized session and abstracts the payment provider, the camera and OCR engine, the cryptographic token generator, the cloud implementation, the mobile application, and the barrier actuator. Low-confidence ALPR events are injected, with no real or benchmarked image dataset behind them. The communication evaluation is a single fixed-seed run with one RSU, a simple path-loss model, no periodic beacon load, and controlled pre-transmission message loss; fading, interference, congestion, C-V2X, and multi-seed comparisons are outside it. A SUMO route continues even when a protocol message is lost, so it does not model physical barrier enforcement. Pseudonymous tokens stay linkable by authorized cloud services, and we offer no anonymity or unlinkability proof.
Reliable messaging is the first thing to fix. The next implementation needs acknowledgment-based retransmission, idempotent request identifiers, timeout recovery, persistent token-revocation queues, and either multiple RSUs or direction-specific ones. Experiments after that should vary transmit power, path loss, fading, channel load, interference, vehicle density, and random seeds, and should set IEEE 802.11p against a suitable C-V2X model. Real memory use and real cryptographic processing cost should replace our serialized-record estimates.
On the perception side, the uncertainty-aware decision policy needs testing against real dirty plate, low light, occlusion, and adversarial-perturbation datasets, and review workload, false escalation, and decision delay all need measuring. Trusted execution environments are a plausible way to protect token generation and local state. The same formally constrained session pattern could later be adapted to aerial-vehicle landing, charging, or maintenance services, although that extension would need its own sensing, communication, and safety validation before it could be considered reliable.
7 Conclusion
This article set out a cyber-resilient, pseudonymization-based session protocol for connected vehicles operating in software-defined edge infrastructure. UPPAAL verification of the single-session FogController together with the ReceiptObserver satisfied the duplicate payment, penalty exclusion, exit closure, synchronization, receipt liveness, deadline, reachability, and deadlock properties. A SUMO/OMNeT++/Veins run then carried smart parking messages over IEEE 802.11p for 200 vehicles across four controlled loss cohorts, recording 159 active sessions, 135 payment confirmations, 132 receipts, and 74 complete local closures, with response times of roughly 50 ms for most responses and 100 ms for receipts. The uncertainty, duplicate payment, outage, and ExitMismatch paths all behaved as designed. The incomplete sessions and the five delivered revocation notices point to retransmission and reliable closure handling as the next requirements. The contribution is a formally constrained session-control design, with wireless execution demonstrated and with the privacy, AI, and communication claims bounded explicitly.
Statements
Data availability statement
The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.
Author contributions
NA: Conceptualization, Methodology, Software, Visualization, Writing – original draft. TM: Formal analysis, Investigation, Project administration, Writing – original draft. DG: Data curation, Resources, Writing – original draft. BA-A: Methodology, Software, Validation, Writing – review and editing.
Funding
The author(s) declared that financial support was not received for this work and/or its publication.
Acknowledgments
The authors acknowledge the support of their respective departments and colleagues who provided technical feedback on the manuscript.
Conflict of interest
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Generative AI statement
The author(s) declared that generative AI was used in the creation of this manuscript. The authors also acknowledge that OpenAI ChatGPT (GPT-5.6 Thinking, 2026) was used for language editing, structural revision, code-review assistance, and preparation of tables and explanatory text. The authors reviewed and take responsibility for the final content, analyses, and claims.
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Supplementary material
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/ffutr.2026.1924100/full#supplementary-material
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Summary
Keywords
connected vehicles, formal verification, privacy-preserving session management, smart parking, software-defined vehicles, trustworthy AI, V2I communication, vehicular edge computing
Citation
Ajax NDC, Meshack T, Gabriel DGN and Al-Athwari B (2026) A cyber-resilient and privacy-preserving session protocol for connected vehicles in software-defined edge infrastructure. Front. Future Transp. 7:1924100. doi: 10.3389/ffutr.2026.1924100
Received
30 June 2026
Revised
04 August 2026
Accepted
27 August 2026
Published
29 September 2026
Volume
7 - 2026
Edited by
Haoxuan Dong, National University of Singapore, Singapore
Reviewed by
Weiwei Jiang, Beijing University of Posts and Telecommunications (BUPT), China
He Li, Nanyang Normal University, China
Updates
Copyright
© 2026 Ajax, Meshack, Gabriel and Al-Athwari.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Baseem Al-Athwari, baseem_cs@kduniv.ac.kr
Disclaimer
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.