A wireless communication method and system based on double-layer synchronization and state feedback

Abstract

The application discloses a wireless communication method and system based on double-layer synchronization and state feedback. By presetting a dynamic security root (DSF), both communication parties independently run PSSM, and two layers of synchronization guarantee are established: the first layer is that logical counters are strictly equal, and zero signaling parameter generation is ensured; the second layer is that physical anchor points are aligned, and the receiving end measures timing observation error through sliding correlation detection, and compares the timing observation error with a capture deviation tolerance to judge a physical layer synchronization state. The physical layer maintains a synchronization mark `ready`, and when out of synchronization, informs the PSSM to enter a synchronization maintenance mode (continue to evolve the logical state but pause data transmission and reception), and immediately restarts communication after recovery. Both parties utilize the same PSSM pilot sequence to realize closed-loop mutual calibration of bidirectional ranging and timing advance, and an external time reference (GPS / base station) is not needed. The application converts a physical layer out-of-synchronization event into a non-disastrous pause-recovery process, supports scenarios such as passive tracking after a launch vehicle maneuver, dynamic joining of a UAV swarm, and the like, and significantly improves system robustness and survivability.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, specifically relating to a wireless communication synchronization method and system based on a Protocol Secure State Machine (PSSM). In particular, by establishing a two-level model of logic counter synchronization and physical anchor alignment, and introducing a physical layer state feedback interface, it achieves highly robust and high-precision bidirectional synchronization and communication between communicating parties without the need for an external time reference. This invention is applicable to scenarios with extremely high requirements for synchronization accuracy and anti-interference capabilities, such as satellite communication, UAV swarms, vehicle-to-everything (V2X) communication, industrial automation, and military data links. Background Technology

[0002] To achieve deterministic communication with zero signaling, those skilled in the art know that communication parameters can be generated by pre-setting a Dynamic Security Foundation (DSF) and a Protocol Security State Machine (PSSM) (see the applicant's prior patents). However, existing solutions mainly address the synchronization problem of "logical states," assuming the physical layer is already in an ideal synchronized state. In real-world physical environments, the following two practical problems remain unresolved: 1. Physical Anchor Point Acquisition Deviation: Both communicating parties independently sample their local physical clocks at the logical decision-making moment, inevitably resulting in a deviation in sampling timing, i.e., acquisition deviation. Existing solutions assume that this deviation can be eliminated through traditional physical layer synchronization, but they do not quantify its tolerance boundary, nor do they design a closed-loop adjustment mechanism linked to this deviation.

[0003] 2. Physical Layer Synchronization Loss Detection and Handling: When channel quality deterioration causes physical layer synchronization loss, the high-layer state machine in traditional solutions continues to evolve according to its original logic, but the entire protocol stack is in a "blind flight" state. The existing PSSM framework lacks a clear, low-latency cross-layer interface for feeding back the physical layer's synchronization state to the PSSM in real time.

[0004] This invention is proposed to solve the above-mentioned practical problems. It builds a complete two-level synchronous closed-loop system on the PSSM framework established by the previous patent, and particularly strengthens the bidirectional positioning and synchronization maintenance capabilities in mobile scenarios. Summary of the Invention

[0005] Core concept definition Concept 1: Dynamic Security Foundation (DSF) DSF is a cryptographically secure triple `(K_sec, Init_Anchor, Rule_ID)` shared by both communicating parties, used for the generation of all deterministic parameters and state synchronization.

[0006] - `K_sec`: Shared key, distributed via secure pre-sharing.

[0007] - `Init_Anchor`: Initial anchor point, containing the initial logical state `S(0)` and the agreed-upon start anchor point `T0`.

[0008] - `Rule_ID`: State transition rule identifier, including logical tick length `T_step`, state update function, calibration period parameter `N_calib`, etc.

[0009] Concept 2: Protocol Security State Machine (PSSM) PSSM is a deterministic state machine based on DSF. It evolves independently among the communicating parties, outputting a time-varying logic state `S(t)`. The evolution is independent of the physical clock and is driven only by the logic tick. As long as the same DSF is shared, the PSSMs of each party remain synchronized on the logical time axis.

[0010] Concept 3: The Logical Decision Moment Discrete moments on the logical timeline defined by `Rule_ID`. At each logical decision moment, the PSSM outputs the current state `S(t)` and triggers physical layer operations.

[0011] Concept 4: Unified Anchor Point Timing and Acquisition Deviation At the logical decision moment, the node instantaneously reads the value obtained from its local physical clock, denoted as `T_anchor`. The difference between the `T_anchor` values ​​of the two communicating parties is defined as the "capture bias" described in this invention, denoted as `δ = |T_anchor,A - T_anchor,B|`. The capture bias is a quantitative indicator of physical layer synchronization.

[0012] Concept 5: Capture Deviation Tolerance The acquisition deviation tolerance `Δ_sync` is the maximum allowable acquisition deviation that ensures the receiver can successfully complete signal detection and synchronization. This tolerance value can be determined by referring to the cyclic prefix length of the OFDM system (e.g., 2.34 μs for a 30 kHz subcarrier spacing), or it can be configured independently according to system requirements. In practical systems, the receiver indirectly determines whether the acquisition deviation is within the tolerance by measuring the deviation between the arrival time of the received signal and the local expected time.

[0013] Concept 6: Fixed Offset and Timing Protection Margin Fixed offsets Δ_tx and Δ_rx are pre-configured fixed time offsets used to calculate physical layer timing from T_anchor: transmission time T_TX = T_anchor + Δ_tx, reception time T_RX = T_anchor + Δ_rx. Δ_tx and Δ_rx can be equal or unequal, and can be statically configured or dynamically generated by PSSM.

[0014] The timing protection margin T_margin is a safety margin used to ensure that the transmission and reception timings do not overlap, and is used to absorb and handle uncertainties such as timing jitter and propagation delay variations. The fixed offset must satisfy: Δ_rx - Δ_tx ≥ T_proc + T_prop_max + T_margin Where T_proc is the receiver processing time, and T_prop_max is the maximum propagation delay.

[0015] Concept 7: Physical Layer Synchronization State Interface The physical layer maintains a synchronization state flag `ready`. When the physical layer detects that the timing observation error exceeds the acquisition deviation tolerance `Δ_sync` multiple times consecutively or cannot demodulate the other party's signal, it sets `ready` to `false` and notifies the PSSM through a dedicated interface. This interface is key to achieving cross-layer collaboration and rapid recovery in this invention.

[0016] Concept 8: Silent Calibration A periodic, signalless long-term drift correction mechanism. The master node broadcasts a status verification token every `N_calib` logical ticks, and the slave nodes verify and silently correct using local counter candidate values ​​`n-1, n, n+1`.

[0017] Concept 9: Integration of Two-Way Positioning and Synchronization Both communicating parties send known DSF pilot sequences to each other, and each measures the actual arrival time of the other party's pilot through sliding correlation detection. The timing observation error is obtained by comparing it with the theoretical arrival time. This error is used to correct the local timing advance (TA) and calculate the distance between the two parties, so as to achieve closed-loop mutual calibration of ranging and synchronization.

[0018] The two-level synchronization model on which this invention is based This invention defines and relies on two independent but cooperative synchronization layers: - First level: Logical counter synchronization (strict equality): Let the counters of communicating parties A and B after the logical decision time be `n_A` and `n_B` respectively, then `n_A = n_B` must be satisfied. This level ensures that both parties can independently generate the same resource intention, which is the basis for zero signaling parameter generation.

[0019] - Second level: Physical anchor alignment (bounded error): At the logical decision moment, both communicating parties instantaneously sample their local physical clocks to obtain anchor times `T_anchor,A` and `T_anchor,B`, the difference of which is called the acquisition bias. Physical anchor alignment is indirectly guaranteed by measuring the timing observation error at the receiving end and ensuring that it does not exceed the acquisition bias tolerance `Δ_sync`.

[0020] The two layers are independent of each other: the long-term consistency of the logic counter synchronization does not depend on the continuous tracking of the physical clock, and the instantaneous error of the physical anchor alignment does not affect the value of the logic counter. The collaborative work of the two layers constitutes the complete synchronization system of this invention.

[0021] Technical solution First aspect: Establishment and maintenance of two-level synchronization A two-level synchronous communication method based on a protocol-secure state machine includes the following steps: 1. Pre-configuration and Startup Phase: Both communicating parties pre-configure the DSF securely and agree on a startup anchor point T0. T0 can be an absolute physical time (such as UTC time), a time offset relative to a certain event (such as "the 1000th local clock cycle after receiving this configuration"), or a consensus time obtained through pre-shared calibration (such as a wired connection). After their respective local clocks reach T0, both parties independently start the PSSM, independently evolving the logic counter n and state S(t) from S(0) in T_steps. The determination of T0 is not limited to external infrastructure; it can rely on the pre-calibrated clocks of both parties, or allow a certain initial deviation (which is absorbed in subsequent closed-loop calibration).

[0022] 2. Logical Counter Synchronization (Level 1): Both parties ensure the long-term stability of Level 1 synchronization through an initial anchor point, deterministic stepping rules, and a low-frequency silent calibration mechanism. Silent calibration includes: the master node broadcasts a status verification token every `N_calib` logical ticks, and the slave node uses local counter candidate values ​​`n-1, n, n+1` to verify the token. Upon successful matching, the local counter is silently updated.

[0023] 3. Physical Anchor Alignment (Second Level): At each logical decision-making moment, both parties independently execute the following sub-steps: - The node reads the local physical clock and obtains `T_anchor`.

[0024] - Calculate the physical layer timing based on the pre-configured fixed offsets `Δ_tx` and `Δ_rx`: transmission time `T_TX = T_anchor + Δ_tx`, reception time `T_RX = T_anchor + Δ_rx`.

[0025] - Synchronization quality detection at the receiver: The receiver uses a locally generated pilot sequence to perform sliding correlation processing on the received signal, finds the correlation peak, and records the actual arrival time t_actual. Based on the local PSSM state and fixed offset, the local theoretical reception time t_expected (i.e., T_RX) is calculated. The timing observation error ε = t_actual - t_expected is calculated. This error comprehensively reflects the effects of propagation delay, crystal oscillator drift, and sampling deviation between the anchor points of both sides (i.e., acquisition deviation δ). After the system enters the closed-loop stable state, the TA closed loop has compensated the propagation delay to the point where the residual error is negligible, and silent calibration has also suppressed crystal oscillator drift. At this time, the fluctuation of ε is mainly determined by the acquisition deviation δ, i.e., ε ≈ δ (ignoring small residual terms). Therefore, if |ε| exceeds the preset acquisition deviation tolerance Δ_sync multiple times consecutively, it can be determined that the physical layer synchronization has failed, triggering out-of-synchronization processing; otherwise, physical synchronization is considered normal.

[0026] The second aspect: Loss-of-synchronization management based on physical layer state feedback The physical layer maintains the synchronization status flag `ready`, which is used to provide feedback on the physical layer synchronization quality to the PSSM. 1. Out-of-sync detection and notification: The physical layer continuously monitors the timing observation error `ε` of the received signal. When it detects that `|ε|` exceeds `Δ_sync` multiple times consecutively or fails to demodulate the other party's signal multiple times consecutively, the physical layer sets the `ready` flag to `false` and immediately notifies the PSSM through a dedicated interface.

[0027] 2. PSSM Synchronization Maintenance Mode: Upon receiving a `ready=false` notification, PSSM enters "Synchronization Maintenance Mode". In this mode: - PSSM continues to evolve the logic state and counter according to the original logic rhythm (`n` increments normally, `S(t)` is updated normally); PSSM suspends the sending and receiving of user data; - Optionally, PSSM generates and sends extremely short heartbeat probe frames at each logical decision moment for rapid sensing of physical layer recovery.

[0028] 3. Channel Recovery and Fast Reboot: When the physical layer detects that the downlink signal quality has recovered, can be correctly demodulated, or |ε| ≤ Δ_sync, it sets the `ready` flag to `true` and notifies the PSSM. Upon receiving the notification, the PSSM immediately exits the synchronization maintenance mode and resumes normal data transmission and reception using the latest logic state `S(t)` and counter value. Since the logic counter never stops evolving during the out-of-sync period and remains synchronized with the network side (both PSSMs evolve independently but synchronously), no calibration or signaling interaction is required after recovery.

[0029] Third aspect: Integration of two-way closed-loop calibration and positioning synchronization 1. Pilot Generation and Mutual Derivation: Both communicating parties generate pilot sequences based on their respective individual DSF and PSSM current states `S(t)`. Uplink and downlink pilots satisfy a conjugate symmetry relationship: `P_DL = conj(P_UL)`. Therefore, the `P_UL` and `P_DL` generated by the first node based on its own PSSM state can uniquely determine the pilot sent by the second node; and vice versa. The same pilot sequence simultaneously performs three functions: - Used as a demodulation reference signal for channel estimation and data demodulation (communication functions); - Serves as a reference signal for time of arrival measurement, used for two-way ranging (positioning function); - Used as a measurement signal for frequency / phase deviation for synchronous closed-loop calibration (synchronization function).

[0030] 2. Time of Arrival Measurement: Within the expected reception window, the first node performs sliding correlation detection on the received signal using a locally generated pilot copy. The position of the correlation peak corresponds to the actual arrival time of the pilot sequence, denoted as `t_actual`. Simultaneously, the first node calculates its local theoretical reception time `t_expected` (i.e., `T_RX = T_anchor,A + Δ_rx`) based on its own PSSM logic state and a fixed offset. Once the system has entered a closed-loop stable state, the theoretical reception time can be approximated as the local `T_RX`, because the TA closed loop has already compensated for the propagation delay.

[0031] 3. Timing Observation Error and Propagation Delay Extraction: Calculate the timing observation error `ε = t_actual - t_expected`. In the initial stage before TA convergence, `ε` mainly reflects the combined effect of propagation delay and clock deviation; during closed-loop operation, fluctuations in `ε` mainly reflect acquisition deviation and channel changes. The first node uses `ε` to update the timing advance: `TA_new = TA_old + α·ε`, where `α` is the adjustment step size (usually taken as 0.5~1). Simultaneously, if the current TA value (i.e., the estimated value of the one-way propagation delay) is known, then the distance `d = c · TA` (c is the speed of light). To improve accuracy, the average value of bidirectional measurements can be used.

[0032] 4. Bidirectional Mutual Calibration: The second node processes the pilot signal of the first node in exactly the same way, obtains the second propagation delay `τ_BA`, and corrects its own TA. Since both nodes measure independently, a closed-loop mutual calibration is formed, so even if one moves, the other can dynamically track it.

[0033] 5. Distance Information Applications: Distance information obtained from two-way ranging can be directly used for applications such as relative positioning, collision warning, and formation keeping, without the need for additional positioning signaling. When combined with a multi-antenna array, the positioning dimensionality can be further improved through angle of arrival (AOA) estimation.

[0034] 6. Integrated Effect: The above measurements and calibrations are performed continuously at each logical decision point, forming a two-way closed-loop control system. The long-term statistical value of the timing observation error `ε` can reflect whether the acquisition deviation exceeds the tolerance, and is used to trigger the second aspect of out-of-synchronization processing. Communication and ranging share the same pilot signal, eliminating the need for a dedicated positioning reference signal, achieving true sensing-comprehension integration.

[0035] Fourth aspect: Group network expansion and dynamic joining Based on the point-to-point two-level synchronization method described in the first to third aspects above, multiple communication nodes can form a self-organizing group network, wherein: 1. Group DSF and Individual Derivation: All nodes within a group share the same group DSF root key `K_sec_group`, and each node is assigned a unique group identifier `ID`. A node's individual DSF is derived from the group DSF and its identifier: `K_sec_node = PRF(K_sec_group, ID, "NODE_KEY")`, `Init_Anchor_node = PRF(Init_Anchor_group, ID, "NODE_ANCHOR")`. Each node independently runs its PSSM based on its individual DSF. All node pilot sequences are dynamically generated from their respective PSSM states and individual keys; pilot sequences between nodes are automatically orthogonal and collisions are avoided.

[0036] 2. Dynamic addition of new nodes: When a new node needs to join an existing group, perform the following steps: - Discovery and Acquisition: New nodes acquire the group DSF through a secure pre-sharing method.

[0037] - Anchor Alignment: The new node listens for at least one full silent calibration cycle to resolve the current logic counter value (e.g., `n=10000`). To verify the continuity of the count, the new node should listen for a second cycle to confirm that `n=10001` has been received, thus confirming that its own clock is aligned with the group time base.

[0038] - Synchronous Joining: The new node calculates the physical time of the next logical decision moment (corresponding to `n=10002`) as its own startup anchor point `T0_new`, starts the PSSM at `T0_new`, and sets the initial counter to `10002`. Afterward, the new node generates a pilot sequence based on its `ID` and PSSM state, maintaining orthogonality with other nodes in the group without requiring additional coordination.

[0039] 3. Group resource management: - When the group size does not exceed the total number of available dedicated physical resources, each node uses the fixed dedicated physical resources allocated during the configuration phase and maps the logical resource index generated by PSSM to the fixed resource to achieve zero-collision hard isolation.

[0040] When the group size exceeds the total number of available physical resources, the nodes elect an arbitration node, which then performs a two-step deterministic arbitration of resource conflicts.

[0041] Fifth aspect: Enhanced mobile survivability One of the communicating parties (such as a transmitter vehicle or ground station) can move freely during communication. During this movement, the mobile party periodically transmits pilot signals (even empty frame pilot signals are transmitted when there is no user data). The other party passively receives these pilot signals, continuously measures the change in timing observation error `ε`, and calculates the mobile party's trajectory and current position in real time. The mobile party does not need to send any additional positioning requests or response signals, and its maneuvering behavior does not affect its tracking capability.

[0042] Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: 1. Theoretical completeness: For the first time, the patent clearly defines a "two-level synchronization model" that separates logic counter synchronization from physical anchor point alignment, providing a clear theoretical framework for analyzing and optimizing synchronization performance.

[0043] 2. Quantization control: By introducing timing observation error `ε` and capture deviation tolerance `Δ_sync`, the physical layer synchronization quality becomes a measurable feedback quantity, fundamentally solving the problem of open-loop system error accumulation.

[0044] 3. High robustness: The "physical layer state notification" interface and the "synchronization maintenance mode" of PSSM were designed, which transformed the catastrophic "out-of-step-reconstruction" process in the traditional scheme into a smooth "pause-recovery" process, greatly improving the system's survivability under extreme channel conditions.

[0045] 4. Integrated Two-Way Positioning and Synchronization: The two communicating parties achieve closed-loop mutual calibration of two-way ranging and timing advance by measuring the arrival time of each other's pilot signals, without relying on GPS or requiring additional positioning signaling. When one party moves, the other party can passively track its position changes without the other party actively transmitting positioning signals.

[0046] 5. Enhanced Mobile Survivability: Specifically, the launch vehicle can be immediately maneuvered and relocated after missile launch. The missile continuously tracks the launch vehicle's real-time location by passively receiving the conventional downlink pilot signal still being transmitted by the launch vehicle. The launch vehicle does not need to transmit any additional signals to be "tracked," and its own mobility does not affect its tracking capability. This greatly shortens the launch vehicle's electromagnetic exposure window and significantly reduces its probability of being hit by enemy fire.

[0047] 6. Completeness of the architecture: The "fixed offset" logic of the previous patent is closely integrated with the "timing observation error" and "ready" feedback mechanism of this patent to form a complete, self-consistent, and engineering-implementable deterministic communication synchronization system.

[0048] 7. Scalable Groups: Through the group DSF and individual derivation mechanism, new nodes can be dynamically added during operation without interrupting group communication; the group size can be flexibly expanded and automatically adapted to hard isolation or arbitration mode.

[0049] 8. Intrinsic security: Through the key derivation mechanism, each node's individual key is independent, so even if the key of a single node is leaked, it will not affect other nodes in the group. Attached Figure Description

[0050] Figure 1 : Schematic diagram of the two-level synchronization model and timing observation error.

[0051] Figure 2 Flowchart of Physical Layer Out-of-Sync Handling and PSSM State Transition Based on Ready Interface.

[0052] Figure 3 Flowchart of integrated two-way closed-loop calibration and positioning synchronization.

[0053] Figure 4 Group network architecture and dynamic joining flowchart. Detailed Implementation

[0054] Example 1: Missiles and Launch Vehicles – Mobile Survivability and Two-Way Tracking Before launch, the launch vehicle and missile are connected by a cable and the DSF is pre-set, with the activation anchor point `T0` agreed upon. The launch vehicle obtains the initial TA value through wired ranging and writes it into the missile. After the missile leaves the launch tube, both independently activate the PSSM at `T0`.

[0055] Two-way synchronization and positioning during flight: At each logical decision moment, the missile transmits an uplink pilot signal, which the launch vehicle receives and performs sliding correlation detection to obtain the actual arrival time `t_actual`. Simultaneously, based on the local PSSM and a fixed offset, it calculates the theoretical reception time `t_expected`, resulting in `ε = t_actual - t_expected`. This `ε` is used to update the TA (TA_new = TA_old + α·ε) and calculate the distance. The launch vehicle simultaneously transmits a downlink pilot signal, and the missile calculates `ε` and updates its own TA in the same way. Both sides obtain distance information, achieving two-way mutual measurement. All pilot signals are dynamically generated by the PSSM, are orthogonal, and unpredictable.

[0056] Launch vehicle relocation: After missile launch, the launch vehicle immediately withdraws from the launch site at maximum speed. During this process, the launch vehicle continues to transmit downlink pilots according to the PSSM rhythm (transmitting empty frame pilots even when there is no user data). The missile passively receives these downlink pilots, continuously measures the changes in `ε`, and calculates the launch vehicle's trajectory and current position in real time. The launch vehicle does not need to send any additional positioning request or response signals, and its maneuvering does not affect the missile's tracking capability.

[0057] Loss-of-synchronization recovery: If the missile enters the blackout zone, causing the physical layer to lose lock, and the physical layer detects `|ε|>Δ_sync` multiple times consecutively (e.g., `Δ_sync = 2.34μs`), it sets `ready` to `false` and notifies the PSSM. The PSSM enters synchronization maintenance mode, continuing to evolve the logic state but suspending data transmission and reception, while sending a synchronization pilot every logic cycle. After exiting the blackout, the launch vehicle receives the synchronization pilot, transmits the TA adjustment value back, and the missile resumes communication. The interruption time is less than 2ms. After recovery, the missile immediately resumes tracking the launch vehicle's position.

[0058] Example 2: Drone Swarm - Dynamic Group Joining and Resource Management The ground station assigns a group DSF and ID to 20 UAVs. Each UAV derives its individual DSF from the group DSF and independently launches its PSSM. After takeoff, each UAV dynamically generates a pilot sequence based on its PSSM state `S(t)` and individual key. The pilots between nodes are automatically orthogonal, preventing collisions.

[0059] New UAV Dynamic Joining: A UAV-21 needs to join an already flying swarm. The UAV-21 obtains the group DSF using a pre-set group key. It listens for silent calibration tokens in the air, resolving the current logical counter value `n=10000` in the first complete cycle; in the second cycle, it resolves `n=10001`, verifying the continuity of the count and the alignment of its own clock. Based on this, the UAV-21 calculates the physical time of the next logical decision moment (corresponding to `n=10002`) as its startup anchor point `T0_new`. At `T0_new`, it starts the PSSM and sets the initial counter to `10002`, immediately synchronizing with the swarm. Afterward, the UAV-21 derives its individual DSF based on its ID. Its pilot sequence is derived from the PSSM state `S(t)` and the individual key, and is orthogonal to the pilots of other nodes in the group.

[0060] Resource pool allocation strategy: When the group size does not exceed the total number of available dedicated physical resources, the ground station can allocate a fixed dedicated spreading code to the UAV-21. The UAV-21 will map the logical resource index to the fixed resource to achieve zero-collision hard isolation. When the resource pool is full, the UAV-21 will directly use the resources dynamically generated by the PSSM to participate in the two-step arbitration, and its pilots will still remain orthogonal.

[0061] Example 3: Vehicle-to-Vehicle (V2V) Networking – Two-way Positioning and Collision Avoidance Vehicle A and Vehicle B are traveling on a highway. Both vehicles have the same pre-installed group DSF (distributed by the roadside unit within the coverage area). After leaving the base station coverage, each vehicle operates its PSSM independently. Each vehicle sends a pilot signal dynamically generated by the PSSM at each logical decision moment, while simultaneously receiving the other vehicle's pilot signal.

[0062] Vehicle A obtains its actual arrival time through sliding correlation detection, calculates the timing observation error `ε`, and then obtains its distance `d_AB` relative to vehicle B, while simultaneously correcting its own timing detection (TA). Vehicle B similarly calculates `d_BA`. Both vehicles obtain their relative distances for collision warning. If vehicle A brakes suddenly, its pilot arrival time will change abruptly, allowing vehicle B to immediately perceive the distance reduction (within tens of milliseconds) at the next logical decision moment, triggering an alarm. The entire process does not rely on GPS and is equally effective in areas with no signal, such as tunnels.

[0063] Example 4: Individual Soldier Handheld Terminal – Silent Mobile Collaboration Two soldiers are conducting a mission behind enemy lines. Before setting off, they exchange DSFs via contact. During the march, both soldiers' terminals operate independently using PSSMs, sending extremely short pilot signals (empty frames) every few seconds. These pilot signals are dynamically generated by the PSSM. Each soldier receives the other's pilot signals and performs slide correlation detection to know the distance and location of their teammate in real time, without actively transmitting location signals. If one soldier moves rapidly (e.g., lying down or sprinting), the other soldier's terminal automatically updates the relative position. The terminals maintain radio silence at all times (only sending extremely short, unpredictable pilot signals), making them difficult for the enemy to detect.

[0064] Industrial applicability This invention can be widely applied to scenarios such as satellite communication, drone swarms, vehicle networking, individual soldier self-organizing networks, and missile data links, achieving highly robust and high-precision two-way synchronization and positioning without relying on external time references. It is especially suitable for mobile platform communication in highly dynamic, highly contested, and GPS-free environments.

Claims

1. A two-level synchronous communication method based on a protocol-secure state machine, characterized in that, include: Logical counter synchronization: The two communicating parties independently maintain the protocol security state machine (PSSM) through a shared Dynamic Security Foundation (DSF) to keep the logical counters strictly equal on the logical time axis, i.e., n_A = n_B; Physical anchor alignment: At each logical decision moment, both communicating parties independently sample their local physical clocks to obtain a unified anchor moment T_anchor; both communicating parties calculate the physical layer timing based on pre-configured fixed offsets Δ_tx and Δ_rx: transmission moment T_TX = T_anchor + Δ_tx, reception moment T_RX = T_anchor + Δ_rx; the receiving end obtains the actual arrival moment through sliding correlation detection and compares it with the local theoretical reception moment to obtain the timing observation error ε; when |ε| exceeds the preset acquisition deviation tolerance Δ_sync multiple times consecutively, the physical layer synchronization is determined to have failed.

2. The method according to claim 1, characterized in that, The capture deviation tolerance `Δ_sync` is independent of the timing protection margin `T_margin` in the fixed offset configuration; where `Δ_sync` is used to determine the signal synchronization quality, and `T_margin` is used to absorb the uncertainty of processing time and propagation delay.

3. The method according to claim 1, characterized in that, It also includes the physical layer state feedback step: - The physical layer maintains the synchronization state flag `ready`; - When the timing observation error `|ε|` continuously exceeds `Δ_sync` or the other party's signal cannot be demodulated, `ready` is set to `false` and PSSM is notified; - After PSSM receives `ready=false`, it enters "synchronization maintenance mode": it continues to evolve the logic state and counter, but suspends the sending and receiving of user data; - When the physical layer recovers and `|ε| ≤ Δ_sync`, set `ready` to `true`, and PSSM exits synchronization maintenance mode and resumes normal communication.

4. The method according to claim 1, characterized in that, It also includes a two-way closed-loop calibration and positioning integration step: - The first node receives the pilot sequence sent by the second node, obtains the actual arrival time through sliding correlation detection, and subtracts it from the local theoretical reception time to obtain the timing observation error `ε`, which is used to correct the timing advance of the first node and calculate the distance to the second node. - The second node processes the pilot sequence of the first node in the same way to obtain the second timing observation error, thereby achieving mutual calibration of bidirectional ranging and timing advance. - The bidirectional measurement continues at each logical decision moment, forming a closed-loop control system.

5. The method according to claim 4, characterized in that, The pilot sequence is derived from the PSSM state and individual DSF of each node. The uplink and downlink pilots satisfy the conjugate symmetry relationship. The same pilot sequence is used for communication demodulation, two-way ranging and synchronization calibration.

6. The method according to claim 1, characterized in that, It also includes a silent calibration step: the master node broadcasts a status verification token every `N_calib` logical ticks, the token containing the master node's logical counter value and a hash authentication code generated based on `K_sec` and `S(t)`; the slave node verifies the token using local counter candidate values ​​`n-1, n, n+1`, and silently updates the local counter after a successful match.

7. The method according to claim 1, characterized in that, Multiple communication nodes share the same group DSF. Each node derives its individual DSF from the group DSF and its unique identifier, and runs its PSSM independently based on its individual DSF. The pilot sequences of all nodes are dynamically generated by their respective PSSM states and individual keys, and the pilots between nodes are automatically orthogonal.

8. The method according to claim 7, characterized in that, It also includes the step of dynamically adding new nodes: - New nodes obtain group DSF; - The new node listens for at least one complete silent calibration cycle, parses the current logic counter value, and verifies the continuity of the count by listening to subsequent cycles; - The new node uses the physical time of the next logical decision moment as the starting anchor point, starts PSSM and sets the initial counter to achieve synchronization with the group.

9. The method according to claim 7, characterized in that: When the group size does not exceed the total number of available dedicated physical resources, each node uses the fixed dedicated physical resources allocated during the configuration phase and maps the logical resource index generated by PSSM to the fixed resource to achieve zero-collision hard isolation; when the group size exceeds the total number of available physical resources, the nodes elect an arbitration node, which then performs two-step deterministic arbitration of resource conflicts.

10. The method according to claim 1, characterized in that, The two parties communicating are the missile and the launch vehicle or the ground station and the mobile terminal. After launch, the launch vehicle or the ground station can move freely. During the movement, it periodically sends pilot signals. The other party passively receives the pilot signals and continuously tracks its position by measuring the timing observation error. The launch vehicle or the ground station does not need to send additional positioning signals for this purpose.

11. A wireless communication system, characterized in that, Includes a communication device for performing the method according to any one of claims 1 to 10.

12. A communication device, characterized in that, It includes a processor and a memory, the memory storing a computer program, and the processor executing the program to implement the steps performed by the corresponding node in the method according to any one of claims 1 to 10.

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