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CN-121984555-A - Remote passive channel shaping method based on passive intelligent reflecting surface

CN121984555ACN 121984555 ACN121984555 ACN 121984555ACN-121984555-A

Abstract

The invention belongs to the technical field of wireless communication, and particularly relates to a remote passive channel shaping method based on a passive intelligent reflecting surface, wherein a transmitting end periodically broadcasts synchronous references, drives a RIS control panel to correct a symbol counter in a moving average manner and aligns OFDM symbol boundaries; the method comprises the steps of pre-loading a reflecting pattern, submitting a designated target symbol and a safety window at fixed time, acquiring a delay sample by using a pilot frequency of coverage switching, obtaining a stable completion upper bound according to a quantile value and an error allowance, selecting a window in a CP, reserved symbol or blank micro-segment according to the upper bound, and synchronously updating a reflecting unit in the window through global latch/pointer exchange. The method limits the switching disturbance in a safety window, suppresses invisible ICI, reduces error codes and improves throughput stability.

Inventors

  • LI YONGDE
  • HUANG YONGJUN
  • LI GANG
  • FU NING

Assignees

  • 四川图林科技有限责任公司

Dates

Publication Date
20260505
Application Date
20260403

Claims (10)

  1. 1. A remote passive channel shaping method based on a passive intelligent reflecting surface is characterized in that a transmitting end, a RIS control board and a receiving end of a communication system are cooperatively controlled, and the following steps are executed: The method comprises the steps that 1, a transmitting end is controlled to periodically broadcast synchronous reference information to an RIS control board, the RIS control board is driven to execute a moving average algorithm through the reference information to correct a local symbol counter, and the time sequence of the RIS control board is aligned with the orthogonal frequency division multiplexing symbol boundary of the transmitting end; step 2, the transmitting end is controlled to issue a preloaded command to the RIS control panel, then the transmitting end is controlled to generate and send a timing submitting command according to the service time sequence, and the target symbol number and the target safety window type of the effective reflection pattern are specified in the timing submitting command; Step 3, the transmitting terminal is controlled to transmit pilot signals for covering the whole RIS switching process to the receiving terminal, and a plurality of switching delay samples are collected according to switching change detection points and switching stabilization points fed back by the receiving terminal; Step 4, the transmitting end is controlled to compare the switching stability completion delay upper bound with the available length, the available length=the cyclic prefix length of the current orthogonal frequency division multiplexing symbol-the protection margin; And 5, in the selected safety window, the hardware logic of the RIS control board is used for forcedly executing global latching or read pointer exchanging operation to drive all reflection units of the RIS array to synchronously update the state, so that the switching from the current reflection pattern to the reflection pattern at the next moment is completed.
  2. 2. The method for shaping a remote passive channel based on a passive intelligent reflecting surface according to claim 1, wherein step 2 comprises: in the pre-loading stage, carrying version numbers and reflection pattern data by pre-loading commands, and controlling the RIS control board to write data into the shadow buffer area in an isolated manner after verification is passed; In the timed commit phase, the RIS control board is controlled to continuously monitor the local symbol counter by the timed commit command carrying the target symbol number and the target security window type, and to perform the operation of applying the shadow buffer data to the reflection unit only when the timing match condition is satisfied.
  3. 3. The method for shaping a long-distance passive channel based on a passive intelligent reflecting surface according to claim 1, wherein in step 1, the synchronization reference message comprises a symbol number of a transmitting end and a high-precision transmission timestamp; Configuring an RIS control board to calculate an alignment error between a local time and a high-precision transmission time stamp, and calculating an average value based on a plurality of alignment error samples to execute correction; The calculation formula of the protection margin is G=P sync +G res , wherein G is the protection margin, P sync is a preset quantile value of the absolute value of the alignment error for a plurality of times, and G res is the upper limit of the resolution of the symbol counter.
  4. 4. A method of shaping a remote passive channel based on a passive smart reflective surface according to claim 3, wherein in step 3, calculating a handover stability completion delay upper bound comprises the steps of: The transmitting terminal is controlled to continuously transmit a plurality of demodulation reference signal pilot symbols and drive the RIS to execute reflection pattern switching; the receiving terminal is instructed to carry out channel estimation on the received pilot frequency symbols, a switching change detection point and a switching stable point are identified, and single switching delay is calculated according to the target trigger time; counting repeatedly collected multiple switching delay samples, and selecting a bit dividing value meeting a preset target leakage probability; determining a measurement error margin, wherein the measurement error margin comprises the sum of a measurement resolution upper bound and a synchronous alignment error upper bound; calculating a switching stability completion delay upper bound according to a formula D safe =d P +M, wherein D safe is the switching stability completion delay upper bound, D P is a bit division value of target leakage probability, and M is a measurement error margin; The control system executes a rolling window updating mechanism, and triggers a reacquisition procedure when the environmental temperature change or the control link delay jitter exceeds a threshold value.
  5. 5. The method for shaping a remote passive channel based on a passive intelligent reflecting surface according to claim 4, wherein in step 4, the decision logic for the system to perform adaptive security window scheduling is: judging whether the condition D safe ≤T CP -G;T CP is satisfied or not as the cyclic prefix length of the current OFDM symbol; If yes, locking a switching mode in the CP, and configuring a switching trigger time as a delay trigger offset delta of the CP starting time, wherein the delta meets 0< delta less than or equal to T CP -D safe -G; If not, scheduling to a reserved symbol mode, controlling the transmitting end to insert a reserved symbol which does not bear service data before the target symbol number, and indicating RIS to trigger switching in an effective area of the reserved symbol.
  6. 6. The method for shaping a remote passive channel based on a passive intelligent reflecting surface according to claim 5, wherein the adaptive security window scheduling further comprises a blank segment mode; When the frame structure of the judging system does not allow the insertion of reserved symbols and does not meet the condition of the intra-CP switching mode, the transmitting end is controlled to divide a blank section which does not bear data in an effective area of a service symbol; encapsulating offset and length parameters of the blank section in a timing submitting command, and driving the RIS control panel to trigger switching in the blank section; the length of a blank section divided by the system is more than or equal to the upper limit +2G of the switching stability completion delay.
  7. 7. A method of shaping a remote passive channel based on a passive smart reflector according to claim 1, wherein in step 5, atomic switching is enforced by configuring the RIS control board in one of the following ways: the first mode is that the RIS control board is configured to generate a global synchronous latch pulse, drive all reflection units to synchronously latch preloaded reflection state codes in a shadow buffer area at the same rising edge of the global synchronous latch pulse, and synchronously update the output state of the reflection units; and secondly, the RIS control board is configured to exchange the read pointers of the current buffer area and the shadow buffer area through the multiplexer, and the read pointers are controlled to instantly point to the shadow buffer area.
  8. 8. The method for shaping a remote passive channel based on a passive intelligent reflecting surface according to claim 1, further comprising a step of controlling the execution of a post-switching self-test; the self-checking step after the control is switched is as follows: the transmitting end is controlled to configure double-probe resources at the symbol position after the reflection pattern is switched, wherein the double-probe resources are two adjacent pilot symbols or two time domain pilot fragments in a single symbol; The receiving end is instructed to perform channel estimation on the double-probe resources respectively to obtain two groups of channel estimation results h 1 and h 2 , and a channel inconsistency index U= |h 2 -h 1 |/|h 1 | is calculated; when the channel inconsistency index U is larger than the switching stability completion delay upper bound, the time-varying risk in the symbol is judged to exist, and the receiving end reports the failure sign to the transmitting end.
  9. 9. The method for shaping the remote passive channel based on the passive intelligent reflecting surface according to claim 8, further comprising a closed loop self-adaptive correction step based on a self-checking result; The closed loop self-adaptive deviation rectifying step based on the self-checking result comprises the following steps: Counting the number of failure marks in a continuous preset window; when the number of the failure marks is lower than a first threshold value, maintaining the current control state, and periodically updating the upper bound of the stable switching completion delay; When the number of the failure marks reaches a first threshold value, triggering the system to enter a window expanding state; When the system is in a windowing state and the number of continuously-appearing failure marks reaches a second threshold value, triggering the system to enter a rollback state, forcedly rollback to the last stable reflection pattern and restarting switching delay sample acquisition.
  10. 10. The method for shaping a remote passive channel based on a passive intelligent reflecting surface according to claim 9, wherein in a window-expanding state, the system automatically performs at least one of the following correction control operations: the statistical quantile value point selected when calculating the upper bound of the stable completion delay of switching is improved; Increasing the value of the measurement error margin; reducing the trigger offset in the intra-CP switching mode; And if the current is the intra-CP switching mode, forcedly scheduling to a reserved symbol mode.

Description

Remote passive channel shaping method based on passive intelligent reflecting surface Technical Field The invention belongs to the technical field of wireless communication, and particularly relates to a remote passive channel shaping method based on a passive intelligent reflecting surface. Background The reconfigurable intelligent reflecting surface (Reconfigurable Intelligent Surface, hereinafter abbreviated as 'RIS') is used as a novel technology in the field of wireless communication, and the discrete phases and amplitude states of a large number of passive reflecting units in an array are subjected to programmable configuration, so that the propagation path of wireless signals can be flexibly regulated and controlled, the 'customized' shaping of a communication environment is realized, and the link quality can be obviously improved especially in the scenes such as remote communication blind compensation, shielding scene diffraction enhancement and the like, so that the method becomes one of key technologies for improving the coverage capacity and transmission reliability of a wireless communication system. The passive RIS is more suitable for large-scale deployment and long-distance link application due to the advantages of no need of additional radio frequency link power supply, simple structure, low cost and the like. In an actual communication system, an orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, hereinafter referred to as "OFDM") system has the characteristics of multipath fading resistance, high spectrum utilization rate, and the like, and becomes a mainstream choice for long-distance wireless communication. The demodulation process of an OFDM system has a core premise that the channel characteristics remain approximately unchanged in the effective data interval of a single OFDM symbol. However, when introducing a passive RIS for dynamic channel shaping, the reflection pattern of the RIS needs to be periodically switched to adapt to propagation environment changes, and this switching process can create serious challenges for demodulation preconditions of the OFDM system: 1. The conflict between the reflective pattern switching and the OFDM demodulation precondition, that is, the effective moment of RIS reflective pattern switching is not absolutely stable, and is influenced by multiple factors, namely, on one hand, the transmission delay jitter of a control link can cause the uncertainty of the time for a switching command to reach an RIS control board, and on the other hand, the uncertainty of the effective moment of switching can be further aggravated by queuing processing delay of the RIS control board, device working temperature change (such as wide-temperature working scene of-20 ℃ to 60 ℃), load fluctuation (such as the change of the configuration quantity of a reflective unit), synchronization error of a large-scale RIS array surface and the like. When the uncertain switching process invades the effective data region of the OFDM symbol, the equivalent channel characteristics in the symbol are mutated, so that the orthogonality among the subcarriers is directly destroyed, and the Inter-subcarrier interference (Inter-CARRIER INTERFERENCE, hereinafter referred to as 'ICI') is introduced. 2. Unlike the failure of the fixed configuration scheme, i.e., unlike the conventional dominant interference (such as link drop), the ICI introduced by RIS switching often appears as "invisible interference", i.e., the link is not directly interrupted, but it can cause deterioration of Error Vector Magnitude (EVM) (typically by more than 10%), increase of Bit Error Rate (BER) (up to an order of magnitude), decrease of throughput (up to 15%), and such performance deterioration is difficult to be quickly located by conventional link detection means, which makes system maintenance and optimization very difficult. To circumvent the above problems, the prior art mainly employs a "fixed waiting interval" or "fixed offset" strategy. For example, a preset fixed waiting time (e.g., 100 μs) ensures that the symbol active area is re-entered after the handover is completed, or the handover trigger time is fixedly shifted to a specific position of the Cyclic Prefix (CP) (e.g., 50% of the CP length). However, in a real deployment scenario, the fixed configuration has the obvious defects that firstly, delay jitter of a control link (the fluctuation range can reach +/-30 mu s) and queuing delay of a control board (the random fluctuation +/-10 mu s) can cause the failure of a fixed waiting interval, secondly, temperature change of a device (the response delay of the device changes by about 5 mu s when the temperature is changed every 10 ℃, the response delay of the device increases by about 8 mu s when the number of reflecting units are configured to be increased) change the time required for switching stabilization, so that the whole switching process cannot be covered by a fixed