Signal design method for communication and perception
By replacing the CP of the OFDM symbol with an empty symbol in a special time slot of the communication system and processing it at the receiver, the problem of degraded sensing performance caused by insufficient CP length is solved, and an efficient combination of communication and sensing functions is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HENAN ACAD OF SCI INST OF APPLIED PHYSICS CO LTD
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-21
AI Technical Summary
In integrated communication and sensing systems, the existing technology suffers from severe degradation in sensing performance due to insufficient CP length, especially when detecting distant targets with significant errors.
In a special time slot of the communication system, the CP of the first OFDM symbol before the GAP is replaced with an empty symbol, and the base station does not transmit signals during the duration of the symbol. At the same time, the received echo data is processed at the receiving end, including bit-phase addition and frequency domain analysis.
It effectively avoids mutual interference between adjacent OFDM symbols, improves sensing performance, and ensures the dual realization of communication and sensing functions.
Smart Images
Figure CN121907657A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a signal design method for communication and sensing, belonging to the field of communication technology. Background Technology
[0002] In communication systems, especially 5G systems, data is transmitted in wireless networks in units of radio frames. Each radio frame is 10 ms long and is further divided into two 5 ms half-frames. Each half-frame contains 5 subframes, and each subframe is 1 ms long. Each subframe is further divided into... It consists of several time slots, among which The value of u depends on the subcarrier spacing configuration used, with different u indicating different subcarrier spacings. In Normal Cyclic Prefix mode, each slot contains 14 OFDM symbols.
[0003] Each OFDM symbol consists of a valid symbol portion and a cyclic prefix (CP), and its structure is as follows: Figure 3 As shown. A cyclic prefix is created by adding a trailing symbol. The symbol is formed by copying and adding samples to the symbol header. In communication transmission, due to the multipath effect, the current OFDM symbol may be affected by the interference of the previous symbol. By inserting a CP (Cost Per Component), as long as its length is greater than the maximum multipath delay of the channel, the interference of the previous symbol is limited to the CP part and will not affect the effective data part of the current symbol, thus effectively overcoming inter-symbol interference (ISI).
[0004] However, using OFDM signals for target sensing presents new challenges. The target being sensed may be located near the base station or at a distant location at the cell edge. If conventional communication methods are still used, processing only the valid symbol portion after removing the CP at the receiver, the echo signal from a distant target may not completely contain the valid signal of the current OFDM symbol within a preset time window, as part of it may be occupied by interference from the previous symbol. In this case, directly using this truncated signal for target detection and parameter estimation (such as distance and velocity) will introduce significant errors. Summary of the Invention
[0005] This application aims to address the problem of severely degraded sensing performance caused by insufficient CP length when communication and sensing share OFDM symbols in an integrated communication and sensing system. It provides a signal design method and apparatus for communication and sensing.
[0006] The present invention solves the above-mentioned technical problems through the following technical solution: A signal design method in a communication-sensing integrated system includes subframes, wherein the subframes include The time slots are configured with a superscript u indicating system configuration parameters used to indicate the subcarrier spacing of the OFDM system. The time slots include special time slots, which include downlink OFDM symbols, uplink OFDM symbols, and GAP symbols. The feature is that the first OFDM downlink OFDM symbol before the GAP is used to transmit communication data and sense targets within the cell, and the CP of the OFDM symbol is replaced with an empty symbol, that is, the base station does not transmit any signal during the duration of the CP.
[0007] Based on the above technical solution, this application further improves and refines the above technical solution as follows: Furthermore, the base station transmits the first OFDM symbol before the GAP (Gap) used for transmitting communication data and sensing targets within the cell, and simultaneously receives the echo data of the OFDM symbol. After removing the empty symbol from the received OFDM symbol, it compares it with the data on the GAP. Each sample point is summed in pairs, and the sensing distance spectrum is calculated based on the sum of the pairs. It is determined by the distance to the perceived target.
[0008] Furthermore, the communication terminal receives the first OFDM before the GAP and the GAP. For each sample point, the communication terminal removes the CP from the OFDM symbol and then connects it to the GAP. Each sample point is summed bitwise, and the subsequent data detection is performed based on the result of the bitwise summation. , This represents the number of samples in the first OFDM hollow symbol before the GAP.
[0009] Furthermore, the bandwidth occupied by the OFDM symbol used for communication and sensing differs from the bandwidth occupied by the OFDM symbol preceding the OFDM symbol by at least one subcarrier. Furthermore, the bandwidth occupied by data on an OFDM symbol used for communication and sensing is different from the bandwidth occupied by data on the OFDM symbol preceding the OFDM symbol.
[0011] The advantages of this application are: it is geared towards the advanced form of integrated communication and sensing, and uses a unified communication signal to realize the dual functions of communication and sensing. By designing the position of the OFDM symbol used for communication sensing in the subframe, setting the CP symbol to empty, and designing the processing procedures for the base station and the terminal to receive the OFDM symbol, it effectively avoids mutual interference between adjacent OFDM symbols due to multipath and effectively improves the sensing performance. Attached Figure Description
[0012] Figure 1It uses a 5G-NR frame structure; Figure 2 The number of time slots under different 5G-NR configurations; Figure 3 A schematic diagram of OFDM symbol construction; Figure 4 The CP of traditional OFDM symbols cannot isolate interference between OFDM symbols; Figure 5 The time slot allocation in the 5G frame structure; Figure 6 OFDM symbols in special time slots; Figure 7 The OFDM symbols received by the end user are the superposition of multiple channel paths with different time delays; Figure 8 For end-user signal processing; Figure 9 For the sensing signal processing process; Figure 10 A schematic diagram showing the bandwidth allocation between the communication and sensing symbols and the previous downlink OFDM symbol. Detailed Implementation
[0013] The following embodiments, in conjunction with the accompanying drawings, are merely for illustrating the technical solutions described in the claims and are not intended to limit the scope of protection of the claims.
[0014] In this application, a 5G communication system is used as an example: The frame structure in a 5G communication system is as follows: Figure 1 As shown. Data is transmitted in wireless networks in units of wireless frames. Each wireless frame is 10 ms long and is further divided into two 5 ms half-frames. Each half-frame contains 5 subframes, and each subframe is 1 ms long. Each subframe is further composed of... It consists of several time slots, among which The value depends on the subcarrier spacing configuration used. In Normal Cyclic Prefix mode, each slot contains 14 OFDM symbols. For details on the number of slots per frame and per subframe under different subcarrier spacing configurations, please refer to [link to relevant documentation]. Figure 2 .
[0015] exist Figure 5 In this context, we assume the subcarrier spacing is 60kHz, based on... Figure 2A radio frame comprises 40 time slots. Through configuration, a configuration cycle of 5 time slots can be used. Within each 5 time slots, 3 slots are used for downlink data transmission (labeled DL), 1 slot for uplink data transmission (labeled UL), and one special time slot (labeled X). Of the 14 OFDM symbols in the special time slot, 10 are used for downlink data transmission, 2 for uplink data transmission, and the remaining 2 are GAP symbols, which cannot transmit any data. In this application, we use the first OFDM symbol before the GAP symbol for communication and sensing.
[0021] OFDM symbol design for communication and sensing: The first OFDM symbol before the GAP is used for both communication and sensing functions. In this OFDM symbol, its CP (Concurrent Phase) is replaced with an empty symbol, meaning that the base station does not transmit any signal during the duration of the CP. Then, the OFDM symbols in special time slots are as follows: Figure 6 As shown.
[0022] The following signal processing procedure can enable both communication and sensing functions to achieve better performance.
[0023] Communication and sensing signal processing: In special time slots, the signal processing flow for OFDM symbols used for downlink and uplink, excluding communication and sensing symbols, is the same as that for regular communication OFDM symbols, and will not be elaborated here. For communication and sensing symbols, the base station transmits these OFDM symbols in the same way as other downlink OFDM symbols, the only difference being that their CP (Content Capture) is empty, meaning no data is transmitted. The reception process is described separately for communication and sensing functions.
[0024] In communication, when an end user receives an OFDM symbol, due to multipath propagation, the received OFDM symbol is a superposition of multiple channel paths with different delays, such as... Figure 7 As shown.
[0025] Assume the received communication and sensing symbols are ,in For the received data of OFDM symbol 9, N This represents the number of samples within an OFDM symbol. Removing the CP from the symbol yields... ,in for The vector, This represents the number of sample points within the OFDM symbol after removing the CP.
[0026] Continue receiving within OFDM symbol 10 (the first GAP symbol). From the sample points, we obtain Since OFDM symbol 10 is a GAP symbol, the base station does not transmit any information within this symbol. Therefore, the data received by the terminal user within OFDM symbol 10 is the data of OFDM symbol 9 after multipath delay.
[0027] Will and Adding opposite positions, that is The above signal processing procedure is as follows: Figure 8 As shown.
[0028] For communication terminal users, the maximum delay of channel multipath is within the CP (Concurrent Protocol) range. This is achieved through the above processing steps. It contains complete OFDM symbol information. After the above processing, its function is the same as the original CP, that is, it transforms the linear time delay caused by multipath into a cyclic time delay, and then it can be processed according to the usual OFDM symbol processing procedure.
[0029] For sensing, the base station receives the echoes of OFDM symbols 9 and 10, and the signal reception process is similar to that in communication. Since the time difference between the echoes from targets closer to the base station and those from targets farther away is much greater than the length of a single CP (Concurrent Response) block, we can accommodate a larger time delay by widening the reception window length for OFDM symbol 10. The signal processing process is as follows: Figure 9 As shown.
[0030] Assuming a cell radius of 500 meters, the time delay difference between the echo from near-end users and the echo from far-end users is: When the subcarrier spacing is 60kHz, the delay difference is... Approximately Therefore, in OFDM symbol 10, the time window is three times the CP length. Within this time window, the received signal of OFDM symbol 10 is the signal of OFDM symbol 9 reflected from a distant target within the cell. and By adding the positions, the result contains all target reflected echo data of OFDM symbol 9. Similar to the principles of communication signal processing, this operation transforms the linear time delay caused by multipath propagation into a cyclic time delay, allowing for time-frequency domain conversion via Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT). Below, we briefly describe the processing procedure for sensing symbols: Step 1: Receive data from OFDM symbol 9, remove CP, and obtain... Step 2: Receive OFDM symbol 10 before Each sample point was obtained. ,in The time duration for each sample point must be greater than or equal to 1. , , For the radius of the cell, It is the speed of light.
[0031] Step 3: and Add the positions one by one to obtain ; Step 4: [Regarding...] Do Point Fourier transform, transforming to the frequency domain, yields .
[0032] Step 5: [Regarding...] Perform channel estimation, i.e. ,in It is the frequency domain data transmitted by the base station on OFDM symbol 9; Step Six: [Regarding...] Perform IFFT, . This refers to the distance spectrum data in perception theory, where each sample point represents a distance unit.
[0033] The processing steps after the radar range spectrum, such as Doppler spectrum and angle spectrum estimation, are the same as those of traditional radar algorithms and are not related to this invention, so they will not be described in detail here.
[0034] Users scheduled on OFDM symbol 8 should be as far apart as possible from users scheduled on OFDM symbol 9 in the frequency domain.
[0035] pass Figure 9 It can be seen that, through and The addition of opposite positions, although While the OFDM symbol 9 already contains all the information, some samples from OFDM symbol 8 are also leaked into the reception window of OFDM symbol 9. This is because the length of the CP (Content Component) cannot cover the echo delay difference between near and far targets within the cell. These leaked samples from OFDM symbol 8 will interfere with the reception of OFDM symbol 9, affecting the sensing performance to some extent.
[0036] To mitigate the impact of this interference, further constraints are imposed on the users scheduled on OFDM symbol 8. For example, the bandwidth occupied by data on OFDM symbol 8 is staggered with the bandwidth occupied by data on OFDM symbol 9. Figure 10 As shown.
[0037] By adding such scheduling constraints, even if the receive window of OFDM symbol 9 contains samples leaked from OFDM symbol 8, the bandwidth used by the data in OFDM symbol 9 is different from that in OFDM symbol 8. Therefore, when using FFT to... Even after transformation to the frequency domain, the interference of OFDM symbol 8 can still be filtered out in the frequency domain, thereby reducing the interference between symbols.
[0038] This does not require that the bandwidths used for data in OFDM symbol 8 and OFDM symbol 9 be completely staggered. This is because the number of data samples leaked from OFDM symbol 8 is not large, and these samples are all signals from echoes of distant targets, with relatively weak energy. Therefore, the interference to OFDM symbol 9 is not very serious. Thus, this constraint can be considered not a strong constraint, but rather a best-effort constraint.
[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A signal design method in a communication-sensing integrated system, comprising subframes, wherein the subframes include Each time slot contains a superscript u indicating a system configuration parameter used to indicate the subcarrier spacing of the OFDM system. The time slots include special time slots, which comprise downlink OFDM symbols, uplink OFDM symbols, and GAP symbols. The characteristic of this configuration is that... The first OFDM downlink OFDM symbol before GAP is used to transmit communication data and sense targets within the cell, and the CP of this OFDM symbol is replaced with an empty symbol, that is, the base station does not send any signal during the duration of the CP.
2. The signal design method in the integrated communication and sensing system according to claim 1, characterized in that, The base station transmits the first OFDM symbol before the GAP (Gap Point) for transmitting communication data and sensing targets within the cell, and simultaneously receives the echo data of the OFDM symbol. After removing the null symbol from the received OFDM symbol, it compares it with the data on the GAP. Each sample point is summed in pairs, and the sensing distance spectrum is calculated based on the sum of the pairs. It is determined by the distance to the perceived target.
3. The signal design method in the integrated communication and sensing system according to claim 2, characterized in that, The communication terminal receives the first OFDM before the GAP and the GAP. For each sample point, the communication terminal removes the CP from the OFDM symbol and then connects it to the GAP. Each sample point is summed bitwise, and the subsequent data detection is performed based on the result of the bitwise summation. , This represents the number of samples in the first OFDM hollow symbol before the GAP.
4. The signal design method in the integrated communication and sensing system according to claim 3, characterized in that, The bandwidth occupied by an OFDM symbol used for communication and sensing differs from the bandwidth occupied by the OFDM symbol preceding it by at least one subcarrier.
5. The signal design method in the integrated communication and sensing system according to claim 4, characterized in that, The bandwidth occupied by data on an OFDM symbol used for communication and sensing is different from the bandwidth occupied by data on the OFDM symbol preceding that OFDM symbol.