A baseband architecture and signal processing method for a co-existence integrated receiver

Abstract

The application discloses a kind of through guide integrated receiver baseband architecture and signal processing method, the processing of compatible MF-TDMA and GNSS signal, support satellite communication and the integration of navigation signal reception.The application architecture includes reusable DFE module, GNSS signal coprocessing module, MF-TDMA symbol cache module, AB time-sharing control module, load evaluation and task scheduling coprocessing module and through guide service processing module.The application is processed in parallel to GNSS and MF-TDMA signal by reusable DFE module, in combination with the time-sharing control method based on load evaluation and task scheduling again, MF-TDMA signal and GNSS can be designed and low-power design of time slot processing of flexible design, it can also degenerate into full-time slot GNSS system or full-time slot MF-TDMA communication system.The application saves hardware resource consumption and can be flexibly designed through guide integrated low-power design.

Description

Technical Field

[0001] This invention belongs to the fields of GNSS navigation receivers and baseband design of satellite communication receivers with MF-TDMA signal system, and specifically relates to a baseband architecture and signal processing method for an integrated communication and navigation receiver. Background Technology

[0002] Autonomous outdoor robots and drones require multi-source sensors to perform environmental perception, autonomous speed measurement, direction measurement, absolute time and geographical location measurement to achieve autonomous navigation. Global Navigation Satellite System (GNSS) is one of the key sensors for three-dimensional absolute spatiotemporal information. Currently, ordinary GNSS receivers can provide UTC time at the microsecond level, three-dimensional latitude, longitude and altitude data at the meter level, and carrier velocity information at the sub-meter level. Based on the latitude, longitude and altitude data provided by GNSS, further information such as the approximate northeast-southeast trajectory and heading of the drone can be obtained. In drone applications, to ensure the operational safety of drones and respond to emergencies such as collisions, a multi-layered, redundant, and reliable communication system is needed to ensure the link between the drone and the human backend system. Satellite communication can achieve global coverage, providing communication guarantees for critical commands and data for drones in areas without terrestrial networks. Common satellite communication widely uses MF-TDMA (Multi-Frequency Time Division Multiple Access) signaling systems, employing a two-dimensional multiple access method combining frequency division (FDMA) and time division (TDMA) for networking and communication. Constellation modulation methods generally use common phase modulation methods such as QPSK. To ensure sufficient effective operating range and sustainability, the endurance of drones is crucial. However, limited by payload capacity and battery weight, outdoor robots and drones place high demands on the power consumption of various components. Existing technologies employ parallel processing to process both MF-TDMA and GNSS signals simultaneously. This approach cannot adapt to the characteristics of MF-TDMA burst frame frequency and GNSS signal real-time signal strength (carrier-to-noise ratio) to perform signal processing on demand, placing high demands on receiver hardware area and the power consumption tolerance of the carrier. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a baseband architecture and signal processing method for an integrated communication and navigation receiver, which is compatible with the processing of MF-TDMA and GNSS signals, supports the integrated reception of satellite communication and navigation signals, and the time-slot-divided or full-time-slot processing of the two signals.

[0004] Technical solution: To achieve the above-mentioned objectives, the present invention provides a baseband architecture for an integrated communication and navigation receiver, comprising:

[0005] The reusable digital front end (DFE) module is used to perform digital front-end processing on received Global Navigation Satellite System (GNSS) signals and Multi-Frequency Time Division Multiple Access (MF-TDMA) communication signals in a time-division multiplexing manner to generate baseband signals;

[0006] The GNSS signal coprocessing module is used to receive and process GNSS baseband signals from the multiplexable DFE module;

[0007] MF-TDMA symbol caching module, used to cache MF-TDMA baseband symbol data streams from the reusable DFE module;

[0008] The communication and navigation service processing module is used to perform MF-TDMA communication and GNSS navigation service processing;

[0009] The AB time-division control module is used to divide a preset time window into time slice A and time slice B, and control the communication and navigation service processing module to perform MF-TDMA communication signal processing tasks or remain idle in time slice A, and to perform GNSS signal processing tasks in time slice B. The duration of the preset time window is determined by the minimum GNSS positioning update cycle.

[0010] The load assessment and task scheduling coprocessing module is used to assess the task processing load in real time, obtain assessment parameters, and adaptively generate time slot time-division control scheduling parameters based on the task processing load assessment parameters to configure the duration of time slot A and time slot B in the next preset time window.

[0011] Preferably, the reusable DFE module uses a high-multiplexed operating clock for time division multiplexing, the frequency of which is greater than a predetermined multiple of the maximum sampling rate of the input signal; the reusable DFE module receives the sampling data of GNSS signals and MF-TDMA communication signals through a ping-pong buffer, and performs mixing, filtering and downsampling processing on the two input signals using time division multiplexing.

[0012] Preferably, the size of the MF-TDMA symbol cache module is configured to store baseband symbol data for at least two MF-TDMA burst frames, and the storage space for each MF-TDMA burst frame is determined based on the maximum symbol rate, sampling multiple, number of bytes per symbol, and maximum time slot per frame; it supports writing one frame of data while reading another frame of data.

[0013] Preferably, the task processing load evaluation parameters include:

[0014] The average carrier-to-noise ratio of GNSS signals is obtained by calculating the carrier-to-noise ratio of each tracked satellite, then summing the carrier-to-noise ratios of all tracked satellites and calculating the average value.

[0015] The number of burst frames to be processed in MF-TDMA communication is calculated from the number of MF-TDMA symbols to be processed in the MF-TDMA symbol buffer module;

[0016] The signal power of the MF-TDMA burst signal is estimated by the reusable DFE module from the received MF-TDMA signal.

[0017] Preferably, the load assessment and task scheduling coprocessing module adaptively generates the time-slot time-division control scheduling parameters based on the task processing load assessment parameters, specifically including:

[0018] When the average carrier-to-noise ratio is greater than the first carrier-to-noise ratio threshold, the duration quota of time slice B is reduced; when the average carrier-to-noise ratio is less than the second carrier-to-noise ratio threshold, the duration quota of time slice B is increased; the first carrier-to-noise ratio threshold is greater than or equal to the second carrier-to-noise ratio threshold.

[0019] When the number of burst frames is less than the frame number threshold, the duration quota of time slice A is reduced; when the number of burst frames is greater than or equal to the frame number threshold, the duration quota of time slice A is increased.

[0020] When the signal power is greater than the power threshold, the duration quota of time slice A is reduced; when the signal power is less than or equal to the power threshold, the duration quota of time slice A is increased.

[0021] Preferably, when the demand for increasing the time slot A duration quota competes with the demand for increasing the time slot B duration quota, a competition processing strategy that prioritizes GNSS signal processing is adopted to ensure that the allocated duration of time slot B is greater than or equal to the allocated duration of time slot A.

[0022] Preferably, the duration configuration of time slot A and time slot B includes: when the duration configuration of time slot A is 0, the entire preset time window is allocated to time slot B to achieve full-time slot GNSS reception; when the duration configuration of time slot B is 0, the entire preset time window is allocated to time slot A to achieve full-time slot MF-TDMA communication.

[0023] This invention also provides a baseband signal processing method for an integrated communication and navigation receiver, applied to the baseband architecture of the integrated communication and navigation receiver, the method comprising:

[0024] The received GNSS signals and MF-TDMA communication signals are digitally processed in a time-division multiplexing manner using a reusable DFE module to generate baseband signals.

[0025] The GNSS signal coprocessing module receives and processes GNSS baseband signals from the reusable DFE module.

[0026] The MF-TDMA baseband symbol data stream from the reusable DFE module is cached through the MF-TDMA symbol caching module.

[0027] The AB time-division control module divides the preset time window into time slot A and time slot B, and controls the communication and navigation service processing module to perform MF-TDMA communication signal processing tasks or remain idle in time slot A, and to perform GNSS signal processing tasks in time slot B.

[0028] The load assessment and task scheduling coprocessing module evaluates the task processing load in real time, obtains assessment parameters, and adaptively generates time slot time-division control scheduling parameters for configuring the duration of time slot A and time slot B in the next preset time window based on the task processing load assessment parameters.

[0029] The present invention also provides a computer system, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the processing steps of the AB time-division control module, the load assessment and task scheduling coprocessing module, and the communication and navigation service processing module in the baseband signal processing method of the integrated communication and navigation receiver.

[0030] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0031] 1. This invention uses a reusable DFE module to alternately process GNSS signals and MF-TDMA communication signals in a time-division multiplexing manner, allowing the two types of signals to share the same set of front-end processing resources. Based on the existing GNSS baseband, only the DFE needs to be modified for time-division multiplexing and an MF-TDMA symbol buffer module and AB time-division control logic need to be added. The baseband processing of MF-TDMA burst symbols can be realized through the communication and navigation service processing module. With a small amount of additional hardware overhead, baseband processing of two different types of signals, GNSS and MF-TDMA, can be achieved on the basis of the GNSS receiver.

[0032] 2. This invention sets up an MF-TDMA symbol caching module to cache the burst frame symbol stream, ensuring that communication burst frames are not lost. It controls the navigation and communication service processing module to perform MF-TDMA communication signal processing (or remain idle) in time slice A and perform GNSS signal processing in time slice B. The duration of the preset time window is determined based on the minimum GNSS positioning update cycle, which ensures navigation and positioning performance.

[0033] 3. The load assessment and task scheduling co-processing module of this invention assesses the task processing load in real time, adaptively generates time-slot time-division control scheduling parameters based on the assessment parameters, and dynamically configures the duration of time slot A and time slot B within the next preset time window. It supports adaptive time slot allocation and task scheduling based on factors such as GNSS carrier-to-noise ratio, MF-TDMA burst frame count, and burst signal power, significantly reducing system power consumption. It also supports configuring the duration of time slot A or time slot B to zero, enabling time-slotted or full-slot GNSS reception or full-slot MF-TDMA communication for both GNSS and MF-TDMA signals on the same platform, saving hardware resources and allowing for more flexible, integrated communication and navigation low-power design. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below.

[0035] Figure 1 This is a schematic diagram of a baseband architecture for an integrated communication and navigation receiver provided in an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of a baseband architecture and time-division control for an integrated communication and navigation receiver provided in an embodiment of the present invention.

[0037] Figure 3 This is a specific implementation diagram of a GNSS communication and navigation integrated prototype receiver in the receiver baseband architecture provided by an embodiment of the present invention.

[0038] Figure 4 This is a schematic diagram illustrating the specific process of signal processing, such as AB time-sharing and load assessment task allocation, during a certain period as exemplified in an embodiment of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] like Figure 1 and Figure 2As shown in the figure, an embodiment of the present invention discloses a baseband architecture for a communication and navigation integrated receiver, including a reusable digital front-end (DFE) module M1, a GNSS signal co-processing module M2, an MF-TDMA symbol buffer module M3, a load assessment and task scheduling co-processing module M4, an AB time-division control module M5, and a communication and navigation service processing module M6. The reusable DFE module M1 is used to perform digital front-end processing on the received GNSS signals and MF-TDMA communication signals using time-division multiplexing to generate baseband signals; the GNSS signal co-processing module M2 is used to receive and process the GNSS baseband signals from the reusable DFE module; the MF-TDMA symbol buffer module M3 is used to buffer the MF-TDMA baseband symbol data stream from the reusable DFE module; the communication and navigation service processing module M6 is used to perform MF-TDMA communication and GNSS navigation service processing; and the AB time-division control module M5 is used to set a preset time... The time window is divided into time slot A and time slot B. The communication and navigation service processing module is controlled to perform MF-TDMA communication signal processing tasks or remain idle in time slot A, and to perform GNSS signal processing tasks in time slot B. The duration of the preset time window is determined by the minimum GNSS positioning update cycle. The load assessment and task scheduling coprocessing module M4 is used to assess the task processing load in real time, obtain assessment parameters, and adaptively generate time slot time-division control scheduling parameters for configuring the duration of time slot A and time slot B in the next preset time window based on the task processing load assessment parameters.

[0041] In some optional implementations, module M1 is used for signal preprocessing of the digital intermediate frequency input signal, including down-conversion, filtering, decimation, and signal power estimation. This module uses a high-multiplexed operating clock for time-division multiplexing, the frequency of which is greater than a predetermined multiple of the maximum sampling rate of the input signal. It receives sampled data from GNSS and MF-TDMA communication signals via a ping-pong buffer and performs mixing, filtering, and downsampling on the two input signals using time-division multiplexing, enabling real-time processing of two or more different input signals.

[0042] Specifically, in module M1, a high-multiplexing clock frequency is used to perform mixing, filtering, and downsampling on the two input signals. Two pre-installed RAMs buffer the two input signals in a ping-pong manner. Let num_gnss be the number of clock cycles required for the DFE to process an N-millisecond GNSS signal, and num_mf be the number of clock cycles required to process an N-millisecond MF-TDMA signal. Since the DFE's operating clock is C MHz, the number of clock cycles available for signal processing within N milliseconds is C*N*1000. As long as C*N*1000 is greater than (num_gnss + num_mf), the DFE can process both GNSS and MF-TDMA signals simultaneously at a clock frequency of C MHz.

[0043] In module M1, after the GNSS signal is processed by the DFE, it is sent in real time to the GNSS signal coprocessing module M2 for further acquisition and tracking hardware processing; the MF-TDMA communication signal is first processed by the DFE, and then the processed data is written to the MF-TDMA symbol buffer module M4, while the CPU is notified through interrupt and AXI bus.

[0044] In some optional implementations, the GNSS signal co-processing of module M2 employs industry-standard GNSS acquisition engines and GNSS tracking correlator engines. The acquisition engine uses a partially matched filter FFT (PMF-FFT) algorithm, implemented in hardware. The tracking correlator engine supports 64 channels, each containing 16 correlation calculation units. Combined with the closed-loop tracking algorithm in the communication and navigation service processing module M6, it utilizes a third-order phase-locked loop (PLL) and a second-order independent code loop (DLL) to achieve GNSS signal acquisition and tracking signal processing.

[0045] In some optional implementations, the communication and navigation service processing module M6 includes a typical processor in the industry, such as a CPU or DSP, for processing communication and GNSS navigation services. It also includes peripheral units such as UART, SPI, I2S, AXI bus and RAM for configuring various modules of the receiver, coordinating the entire signal and information layer processing process through software, and performing further baseband signal processing, message and symbol demodulation, and receiver output on the output data of the GNSS signal coprocessing module and the output data of the MF-TDMA symbol FIFO.

[0046] After storing one frame of data, the MF-TDMA symbol buffer in module M3 notifies the CPU via an interrupt. The communication and navigation service processing software running on the CPU then extracts data and processes services when the MF-TDMA task time slot arrives, based on the task information of the current time slot provided by the AB time-division control module M5. The buffer size of module M3 is configured to store baseband symbol data for at least two MF-TDMA burst frames. The storage space for each MF-TDMA burst frame is determined based on the maximum symbol rate, sampling multiple, number of bytes per symbol, and maximum time slot per frame. It supports writing one frame of data while reading another.

[0047] The load assessment and task scheduling coprocessing module M6 is responsible for assessing the receiver's communication and navigation task processing load and adaptively generating time-slot time-division control scheduling parameters based on the GNSS positioning update cycle in real time. The AB time-division control module, according to the specific time slots and task allocation, controls the communication and navigation service processing module to execute corresponding signal processing tasks. For example... Figure 2 As shown in Table 1, time-slot division control based on the GNSS positioning update cycle is implemented, and its implementation is described below:

[0048] S1: AB time-division control divides each signal processing time window Tgn into two time slices, AB;

[0049] S2: Each time slice can be used to execute different baseband signal processing tasks. Time slice B executes the GNSS positioning task to ensure the continuity of the GNSS positioning cycle; time slice A can execute the MF-TDMA communication task and maintain the idle state (IDLE), denoted as task X.

[0050] S3: Time allocation is denoted as {A(n), B(n)}, where A(n) represents the processing time allocated to time slice A when the time window index is n; B(n) represents the processing time allocated to time slice B when the time window index is n; the time unit is ms.

[0051] S4: Time window size Tgn (ms) = A(n) + B(n). The system allocates A(n) and B(n) according to the size of Tgn. Tgn is equal to the minimum GNSS positioning update period required by the receiver system specifications.

[0052] S5: Time window index n, used in this embodiment to mark the sequence number of the current processing time window.

[0053] In some optional implementations, the task processing load assessment parameters used in the load assessment and task scheduling coprocessing module include: the average carrier-to-noise ratio of the GNSS signal, which is obtained by calculating the carrier-to-noise ratio of each tracked satellite, then summing the carrier-to-noise ratios of all tracked satellites and calculating the average value; the number of unprocessed burst frames of MF-TDMA communication, which is calculated from the number of unprocessed MF-TDMA symbols in the MF-TDMA symbol buffer module; and the signal power of the MF-TDMA burst signal, which is obtained by the multiplexable DFE module estimating the signal power of the received MF-TDMA signal.

[0054] The load assessment and task scheduling coprocessing module adaptively generates the time-slot time-division control scheduling parameters based on the task processing load assessment parameters, specifically including:

[0055] When the average carrier-to-noise ratio is greater than the first carrier-to-noise ratio threshold, the duration quota of time slice B is reduced; when the average carrier-to-noise ratio is less than the second carrier-to-noise ratio threshold, the duration quota of time slice B is increased; the first carrier-to-noise ratio threshold is greater than or equal to the second carrier-to-noise ratio threshold.

[0056] When the number of burst frames is less than the frame number threshold, the duration quota of time slice A is reduced; when the number of burst frames is greater than or equal to the frame number threshold, the duration quota of time slice A is increased.

[0057] When the signal power is greater than the power threshold, the duration quota of time slice A is reduced; when the signal power is less than or equal to the power threshold, the duration quota of time slice A is increased.

[0058] In this embodiment, the load assessment and task scheduling coprocessing module M4 is responsible for assessing the task processing load of the receiver's communication and navigation service processing module. Based on three conditions—1) the average carrier-to-noise ratio of the current target tracking GNSS signal, 2) the number of currently received MF-TDMA communication burst frames, and 3) the signal power of the currently received MF-TDMA burst signal—it adaptively generates a schedule based on the GNSS positioning update cycle in real time. Figure 2 The time-slot time-division control scheduling parameters shown in Table 1 dynamically adjust the AB time slot quota for the next time slot. The specific quota adjustment amount can be optimized in advance based on the signal code rate and system performance requirements, and further optimized according to system priority.

[0059] Specifically, the average carrier-to-noise ratio (CNR) of the target-tracking GNSS signal is the average CNR of the target GNSS satellite signal currently being tracked by the receiver, denoted as cnr_avr; the number of currently received MF-TDMA communication burst frames refers to the total number of MF-TDMA burst frames currently being received, received but yet to be processed in the symbol buffer of module M4, denoted as burst_num; and the power estimation result of the currently received MF-TDMA burst signal is denoted as signal_snr.

[0060] When the average carrier-to-noise ratio cnr_avr is greater than the threshold cnr_thd, the GNSS signal quality is considered high, and the quota of time slot B can be reduced in the next scheduling time slot; otherwise, the quota of B needs to be increased. When the number of MF-TDMA burst frames to be processed, burst_num, is less than the threshold burst_num_thd, the number of bursts to be processed is considered low, and the quota of time slot A can be reduced in the next scheduling time slot; otherwise, the quota of A needs to be increased. When the signal power estimation result of the MF-TDMA burst signal to be processed, signal_snr, is greater than the threshold signal_snr_thd, the MF-TDMA signal quality is considered high, and the quota of time slot A can be reduced in the next scheduling time slot; otherwise, the quota of A needs to be increased.

[0061] When the demand for increasing the time slot A duration quota competes with the demand for increasing the time slot B duration quota, a competition processing strategy that prioritizes GNSS signal processing is adopted to ensure that the allocated duration of time slot B is greater than or equal to the allocated duration of time slot A.

[0062] In this embodiment, the size of the time window Tgn in the AB time-division control module M5 is uniquely determined by the receiver's GNSS positioning frequency requirements. Time slot B is fixed for GNSS processing to ensure that the GNSS positioning output frequency meets the requirements; time slot A is used entirely for MF-TDMA signal processing, or partially for MF-TDMA signal processing, with the remaining time kept idle. Since MF-TDMA is a burst signal, when there are no MF-TDMA burst frames to process in the current time window, time slot A can be configured entirely as idle to further reduce system power consumption. If an MF-TDMA burst frame arrives during the processing of time slot B, the DFE stores the MF-TDMA burst frame data in the MF-TDMA symbol FIFO of module M3 for processing when the next time slot A arrives.

[0063] like Figure 3As shown below, a GNSS integrated communication and navigation prototype receiver is used as a specific embodiment to further illustrate the present invention. This prototype receiver supports the processing of L-band MF-TDMA satellite communication and BeiDou B1I signals from a certain low-Earth orbit satellite. The receiver's RF channel receives L-band BeiDou B1I signals and MF-TDMA satellite downlink communication signals in parallel. The maximum symbol rate is 48kHz, and the length of a TDMA burst frame is 60ms. It supports voice and data communication. The RF channel outputs two digital intermediate frequency signals to the receiver's baseband via an ADC, where the B1I sampling rate is 15.36MHz and the MF-TDMA sampling rate is 960kHz. The baseband adopts the integrated communication and navigation receiver baseband signal processing architecture described in this invention, which includes:

[0064] M1: A reusable digital front-end (DFE) module used for signal preprocessing such as down-conversion, filtering, decimation, and signal power estimation of digital intermediate frequency input signals. This module supports time-division multiplexing via a high-multiplexed operating clock, enabling real-time processing of two or more different input signals.

[0065] M2: GNSS signal coprocessor module, including industry-typical GNSS acquisition engine, GNSS tracking correlator engine, etc.;

[0066] M3: MF-TDMA symbol buffer module, which is used to buffer the baseband symbol data stream of MF-TDMA;

[0067] M4: Load assessment and task scheduling coprocessing. This module is responsible for assessing the receiver's communication and navigation task processing load and adaptively generating time-slot time-division control scheduling parameters based on the GNSS positioning update cycle in real time. Figure 3 Table 2);

[0068] M5: AB time-sharing control, which controls the communication and navigation service processing module to execute corresponding signal processing tasks based on specific time slots and task allocations. AB time-sharing control is implemented in software. (See attached image) Figure 3 As shown in Table 2, time-slot division control based on the GNSS positioning update cycle is implemented as follows:

[0069] S1: AB time-division control divides each signal processing time window Tgn into two time slices, AB;

[0070] S2: Each time slice can be used to execute different baseband signal processing tasks. Time slice B executes the GNSS positioning task to ensure the continuity of the GNSS positioning cycle; time slice A can execute the MF-TDMA communication task and maintain the idle state (IDLE), denoted as the MF / IDLE task.

[0071] S3: Time allocation is denoted as {A(n), B(n)}, where A(n) represents the processing time allocated to time slice A when the time window index is n; B(n) represents the processing time allocated to time slice B when the time window index is n; the time unit is ms; in this specific embodiment, the system prioritizes GNSS tracking quality, and A(n) is configured as 20ms by default, and B(n) is configured as 80ms; specifically, when the time window indices n are 11, 12, and 13, A(11) = 0ms, B(11) = 100ms, A(12) = 60ms, B(12) = 40ms, A(13) = 20ms, and B(13) = 80ms;

[0072] S4: Time window size Tgn (ms) = A(n) + B(n). The system allocates A(n) and B(n) according to the size of Tgn. Tgn is equal to the minimum GNSS positioning update period required by the receiver system specifications. In this specific embodiment, Tgn = 100ms, which corresponds to a minimum GNSS positioning update period of 100ms, that is, the GNSS positioning solution output frequency is 10Hz.

[0073] S5: Time window index n, used in this embodiment of the invention to mark the sequence number of the current processing time window;

[0074] M6: Communication and Navigation Service Processing Module. This module includes a typical processor in the industry, such as a CPU or DSP, and supporting software to perform communication and GNSS navigation service processing. It also includes peripheral units such as UART, SPI, I2S, AXI bus, and RAM, which are used to configure various modules of the receiver, coordinate the entire signal and information layer processing through software, and perform further baseband signal processing, message and symbol demodulation, and receiver output on the output data of the GNSS signal coprocessing module and the output data of the MF-TDMA symbol FIFO.

[0075] Uplink Transmit Module: As a component of the prototype receiver, it completes the transmission of MF-TDMA signals. The RF channel supports full-duplex transmission and reception. The uplink transmit module adopts a typical industry design, which will not be elaborated here.

[0076] In this embodiment of the invention, the unified operating clock of the SOC baseband is 104MHz (period approximately 9.7ns), which is 6 to 7 times the maximum input signal sampling rate of the DFE, 15.36MHz. In this example, one 15.36MHz ADC sampling rate B1I signal and one 960kHz ADC sampling rate signal enter the receiver in parallel and are stored in the two front-end memories (RAMs) of the DFE using a ping-pong buffering method. Both front-end RAMs are configured to store 2.5ms of data, with the RAM depth for GNSS data storage being 15.36MHz * 2.5ms and the RAM depth for MF-TDMA data storage being 960kHz * 2.5ms. When the data to be processed stored in RAM exceeds 1ms, the DFE starts and uses a 104MHz operating clock. It performs preprocessing such as mixing, downsampling, and signal power calculation on the data in the two RAMs using time-division multiplexing. The preprocessing is implemented using hardware pipeline. The processing time is the number of input sampling points to be processed * the operating clock cycle + the processing delay. The processing delay is introduced by hardware registers. The DFE processing delay is generally in the microsecond range. In this example, the DFE processes the two input signals in 1ms frames. The GNSS num_gnss = 15.36MHz * 1ms = 15360 frames, and the MF-TDMA num_mf = 960kHz * 1ms = 960 frames. In practical applications, in addition to the operating clock cycle required for each sampling point, the processing delay of the DFE signal processing should also be considered. In this example, both GNSS and MF-TDMA signals use 64-point FIR filters. Including power calculation and decimation, the entire processing delay does not exceed 200 operating clock cycles, corresponding to approximately 200 * 9.7 ns (1940 nanoseconds). Therefore, the DFE processing takes a total of (15360 + 960) * 9.7 ns + 1940 ns = 160.244 microseconds. Thus, in this embodiment, for 1 ms of GNSS and MF-TDMA data, the DFE only needs approximately 160.244 microseconds to complete the processing, before the next millisecond of ADC data arrives.

[0077] The MF-TDMA symbol buffer of module M3, considering the maximum symbol rate of the target MF-TDMA burst frame is 48KHz, is stored at 4 times sampling, with each symbol occupying 2 bytes, and the maximum time slot of a single TDMA frame is 60ms, requires 60ms*48KHz*4*2byte=23040bytes of storage space; considering that MF-TDMA signal processing can be performed once in each time window, and the baseband processing speed is much greater than the symbol rate, in this embodiment of the invention, the size of the MF-TDMA symbol buffer is designed to be 2*23040bytes, approximately 46Kbytes, which can continuously store the symbols of two frames of MF-TDMA.

[0078] In this embodiment of the invention, the MF-TDMA symbol buffer of module M3 is preferably connected to the central processing unit via an AXI high-speed bus. The AXI bus bandwidth exceeds 200 Mbyte / s, allowing all data in the MF-TDMA buffer to be read via DMA within 1 ms. Simultaneously with buffer reading, new burst frame symbols from the DFE can be written to the buffer, thus supporting continuous time-slot processing of the MF-TDMA signal. Alternatively, a ping-pong buffering method can be used to reduce the AXI bus frequency, thereby reducing instantaneous power consumption during data reading.

[0079] The time-division control of module M5 has a time window size Tgn determined by the GNSS positioning frequency. In this embodiment, the GNSS positioning frequency requirement is 10Hz, so Tgn is equal to 100ms; if the GNSS positioning frequency requirement is 5Hz, then Tgn is configured to 200ms.

[0080] In this embodiment of the invention, the communication and navigation service processing module M6 is jointly implemented by the CPU, SRAM, and peripherals on the SOC system side, and the turbo / viterbi channel codec accelerator, GNSS coprocessor, DFE, and BUFFER modules on the SOC baseband side. This invention preferably adopts a typical industry-standard SOC architecture based on the ARM Coterx A7, including a set of peripherals such as SRAM, AXIOC bus, UART, and SPI; it also communicates with the GNSS coprocessor via the AXI bus and interrupts. Software code based on the FreeRTOS operating system runs on the CPU Coterx A7 of the on-chip system to implement the communication and navigation service processing functions. This software runs GNSS-related software programs such as GNSS tracking soft loop, GNSS message demodulation, and GNSS positioning calculation on different threads, as well as MF-TDMA frame synchronization, frequency estimation, channel estimation and equalization, symbol demodulation and decoding, and other processing. Since computationally intensive tasks such as Fourier transform and channel decoding are implemented using hardware acceleration, the processing pressure on the pure software on the A7 CPU is relatively low. This invention does not limit the specific design of the software and hardware of the communication and navigation service processing module. It can be designed specifically according to the target GNSS and MF-TDMA system of the receiver, while ensuring the task processing capability.

[0081] The load assessment and task scheduling coprocessing of module M4 is responsible for assessing the real-time task processing load of the communication and navigation service processing module in the current time slot of the receiver. In this embodiment of the invention, it is implemented in software. Software implementation can support greater flexibility. In this example, this module is specifically implemented in software running on a Cortex A7 CPU, and is integrated with the software code of module M5, which is the communication and navigation service processing module.

[0082] The load assessment and task scheduling coprocessing of module M4 is responsible for generating time slot allocation parameters for time-sharing control of module M5 in real time. In this invention example, a strategy based on system index priority is adopted to design optional AB time slice configurations. At the same time, based on the characteristics of the code rate of B1I frequency point 2.046MHz and the maximum symbol rate of MF-TDMA 48KHz, four preferred time slice configuration levels of 20ms, 40ms, 60ms and 80ms are designed in advance, as well as IDLE (0ms) and full time slot (100ms), for a total of 6 levels.

[0083] Since system requirements prioritize GNSS accuracy, in this embodiment of the invention, the default AB time slice configuration is selected as A(n) = 20ms and B(n) = 80ms (e.g., Figure 3 The configuration under time window index 13 in Table 2 (using the default configuration) ensures higher GNSS tracking performance under normal circumstances.

[0084] In this embodiment, based on three conditions—1) the average carrier-to-noise ratio (cnr_avr) of the current target tracking GNSS signal, 2) the number of currently received MF-TDMA communication burst frames (burst_num), and 3) the signal power (signal_snr) of the currently received MF-TDMA burst signal—time-slot time-division control scheduling parameters based on the GNSS positioning update cycle are generated in real time. This supports dynamic adjustment of the A and B time slice allocation for the next time slot. This invention does not limit the specific dynamic adjustment criteria for A(n) and B(n) under different n values.

[0085] In practical applications, the average carrier-to-noise ratio (CNR) of the current target tracking GNSS signal, cNR_avr, is calculated by first calculating the CNR of each tracked satellite using the industry-standard wideband / narrowband power ratio method or the fourth-order moment estimation method. Then, the CNRs of all tracked satellites are summed and the average is calculated to obtain cNR_avr. The number of currently received MF-TDMA communication burst frames, burst_num, is calculated using the number of unprocessed MF-TDMA symbols in the M4 symbol buffer of the module. In this example, the maximum symbol rate of the target MF-TDMA burst frame is 48 kHz, and the maximum time slot of a single TDMA frame is 60 ms, corresponding to 60 ms * 48 kHz = 2880 symbols. The number of unprocessed symbols is modulo 2880 to obtain the number of unprocessed burst frames, burst_num. The signal power of the currently received MF-TDMA burst signal, signal_snr, is obtained by the DFE estimating the signal power of the received MF-TDMA signal. In this example, the DFE uses the industry-standard signal envelope method for calculation, but a lookup table method can also be used.

[0086] In this embodiment of the invention, considering the complexity of the GNSS scenario, the preferred setting for the average carrier-to-noise ratio (CNR) threshold cnr_thd is 28dB and 35dB. When cnr_avr is greater than 35dB, the GNSS signal cnr_avr is defined as high; when cnr_avr is less than 35dB but greater than 28dB, the GNSS signal cnr_avr is defined as medium; and when cnr_avr is less than 28dB, the GNSS signal cnr_avr is defined as low. When cnr_avr is high, the quota of time slice B can be significantly reduced in the next scheduling time slot; when cnr_avr is medium, the default configuration can be maintained or the quota of time slice B can be appropriately reduced; when cnr_avr is low, the quota of B needs to be increased. The specific quota is selected from the system's preferred time slice configuration level.

[0087] The threshold for the number of pending MF-TDMA burst frames, burst_num_thd, is set to 2. When there are fewer than 2 pending frames, it is considered that the number of pending bursts is small, and the quota of time slice A can be reduced in the next scheduling time slot; otherwise, the quota of A needs to be increased.

[0088] The threshold signal_snr_thd for the power estimation result of the MF-TDMA burst signal to be processed is set to 6dB. When the power estimation result of the burst signal to be processed exceeds 6dB, the MF-TDMA signal quality is considered high, and the quota of time slot A can be reduced in the next scheduling time slot; otherwise, the quota of A needs to be increased.

[0089] In this embodiment of the invention, in accordance with the requirement of prioritizing GNSS accuracy, when the allocation requirements of both A and B time slices need to be increased, the competition processing strategy is to prioritize GNSS processing time slices, that is, the allocation of time slice B should be greater than or equal to that of time slice A.

[0090] For example, the specific process of signal processing such as AB time-sharing and load assessment task allocation during a certain period is as follows: Figure 4 As shown:

[0091] During time window index n=10, the load assessment observed the following in the current time slot: 1) cnr_avr is low (time slot B share needs to be increased), 2) burst_num is 0 (no MF-TDMA processing requirement, time slot A share should be reduced), and 3) signal_snr has no signal and is not assessed. The task scheduling parameters for the next time slot are generated as follows: time slot A is allocated 0ms, IDLE task; time slot B is allocated 100ms GNSS task (to improve GNSS signal tracking quality).

[0092] During time window index n=11, within time slot A (11) 0ms, the receiver is in an IDLE low-power state; within time slot B (11) 100ms, the receiver executes a GNSS task. Based on the historical state of the previous time window, the GNSS signal tracking loop is re-locked and outputs observations. The firmware updates and outputs a positioning solution report based on the new observations. At this time, the receiver simultaneously receives a 60ms MF-TDMA burst frame and stores it in the BUFFER of module M4. Meanwhile, the load assessment observes that under the current time slot 1) cnr_avr is high (which can reduce the share of time slot B), 2) burst_num is high (which requires more processing time), and 3) signal_snr is low (which requires complex algorithms and processing time). The task scheduling parameters for the next time slot are generated as follows: time slot A is allocated 60ms for MF task (MF-TDMA communication processing task); time slot B is allocated 40ms for GNSS task.

[0093] During time window index n=12, within 60ms of time slot A (12), the receiver processes the MF-TDMA burst frames received in the previous time window, including time-frequency synchronization, channel equalization, symbol demodulation and decoding, etc., and completes the demodulation of the burst data frames; at the same time, the MF-TDMA BUFFER continues to store the newly arrived MF-TDMA burst frames; within 40ms of time slot B (12), the receiver performs the same GNSS signal processing; at the same time, the load assessment observes that in the current time slot 1) cnr_avr is low (time slot B share can be appropriately reduced or maintained), 2) burst_num is low (time slot A share can be appropriately reduced), 3) signal_snr is high (time slot A share can be appropriately reduced), and generates the task scheduling parameters for the next time slot: time slot A is allocated 20ms, MF task; time slot B is allocated 80ms, GNSS task;

[0094] During time window index n=13, time slice A (13) processes the new MF-TDMA burst frame stored in time window index 12; time slice B (13) performs GNSS signal processing; when time slice B (13) is about to run out, a new MF-TDMA burst frame arrives and is stored in the MF-TDMA symbol BUFFER; at the same time, the load assessment observes that in the current time slot 1) cnr_avr (the share of time slice B can be appropriately reduced or maintained), 2) burst_num is 0, 3) signal_snr has no signal and is not evaluated, and generates the task scheduling parameters for the next time slot: time slot A is allocated 20ms, IDLE task; time slot B is allocated 80ms, GNSS task;

[0095] During time window index n=14, since new MF-TDMA frames have not been fully received during time index 13, the receiver is assigned to the IDLE state during the 20ms of time slot A (14); GNSS processing is performed during the 80ms of time slot B (14), and at the same time, two consecutive MF-TDMA frames continuously enter the receiver and are stored in the MF-TDMA symbol BUFFER. When the second MF-TDMA frame enters the MF-TDMA symbol BUFFER, the receiver firmware preferably starts DMA in advance to move the first MF-TDMA burst frame data in the BUFFER to the SOC. In RAM, ensure that even if a third frame of MF-TDMA bursts in, there is still enough space in the MF-TDMA symbol buffer for storage. Meanwhile, load assessment observes that in the current time slot: 1) cnr_avr (requiring an increase in time slice B share), 2) burst_num is high (requiring an increase in time slice A share), and 3) signal_snr is low (requiring increased processing time). A and B are in contention. Based on system design principles, GNSS accuracy is prioritized. Therefore, after synthesis, the task scheduling parameters for the next time slot are generated: time slot A is allocated a 40ms MF task; time slot B is allocated a 60ms GNSS task.

[0096] During time window index n=15, the 40ms of time window A (15) processes the two frames of MF-TDMA received during time window index 14; GNSS processing is performed in the 60ms of time window B (15); as time window B (15) nears the end, a new MF-TDMA burst frame arrives and is stored in the MF-TDMA symbol BUFFER; at the same time, the evaluation observes that 1) cnr_avr is high, 2) burst_num is 0, and 3) signal_snr has no signal and is not evaluated, and generates the task scheduling parameters for the next time window: time window A is allocated 60ms, IDLE task; time window B is allocated 40ms, GNSS task;

[0097] During time window index n=16, the receiver is assigned to the IDLE state for 60ms in time slot A (16), and GNSS processing is performed by the communication and navigation service processing software for 40ms in time slot B (16). The load assessment and task scheduling software continues to allocate time slots and tasks for the next time slot based on the receiver's cnr_avr, burst_num, signal_snr, etc. during the current time slot. At the same time, the new MF-TDMA burst frames that enter during time window index 15 have not yet been fully received, and the receiver continues to receive and store the MF-TDMA symbol BUFFER during time window index 16. The receiver continues to work in this way.

[0098] Under the signal processing and task scheduling described above, the receiver in the specific embodiment of the present invention maintains a specific GNSS positioning calculation frequency, and performs targeted time slot adaptive allocation and task orchestration scheduling based on the current time slot receiver cnr_avr, burst_num, signal_snr, etc., thereby realizing the integrated reception of low-power GNSS navigation and MF-TDMA communication signals.

[0099] This invention also provides a baseband signal processing method for an integrated communication and navigation receiver, applied to the baseband architecture of the integrated communication and navigation receiver. The method includes: performing digital front-end processing on received GNSS signals and MF-TDMA communication signals in a time-division multiplexing manner using a reusable DFE module to generate baseband signals; receiving and processing GNSS baseband signals from the reusable DFE module using a GNSS signal coprocessing module; buffering MF-TDMA baseband symbol data streams from the reusable DFE module using an MF-TDMA symbol buffering module; dividing a preset time window into time slot A and time slot B using an AB time-division control module, and controlling the communication and navigation service processing module to perform MF-TDMA communication signal processing tasks or remain idle in time slot A, and to perform GNSS signal processing tasks in time slot B; and evaluating the task processing load in real time using a load assessment and task scheduling coprocessing module to obtain evaluation parameters, and adaptively generating time slot time-division control scheduling parameters for configuring the duration of time slot A and time slot B in the next preset time window based on the task processing load evaluation parameters.

[0100] This invention also provides a computer system, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the processing steps of the AB time-division control module, the load assessment and task scheduling coprocessing module, and the communication and navigation service processing module in the integrated communication and navigation receiver baseband signal processing method.

[0101] The above embodiments are preferred embodiments of the present invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. For example, the size of the time window, the preferred time configuration parameters of time slices A and B, the cnr_avr threshold, the burst_num threshold, the signal_snr threshold, etc. can be adjusted according to GNSS positioning frequency, performance requirements, signal quality indication, etc. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the claims.

Claims

1. A baseband architecture for an integrated communication and navigation receiver, characterized in that, include: The reusable digital front-end (DFE) module is used to perform digital front-end processing on received Global Navigation Satellite System (GNSS) signals and Multi-Frequency Time Division Multiple Access (MF-TDMA) communication signals in a time-division multiplexing manner to generate baseband signals; The GNSS signal coprocessing module is used to receive and process GNSS baseband signals from the multiplexable DFE module; MF-TDMA symbol caching module, used to cache MF-TDMA baseband symbol data streams from the reusable DFE module; The communication and navigation service processing module is used to perform MF-TDMA communication and GNSS navigation service processing; The AB time-division control module is used to divide a preset time window into time slice A and time slice B, and control the communication and navigation service processing module to perform MF-TDMA communication signal processing tasks or remain idle in time slice A, and to perform GNSS signal processing tasks in time slice B. The duration of the preset time window is determined by the minimum GNSS positioning update cycle. The load assessment and task scheduling coprocessing module is used to assess the task processing load in real time, obtain assessment parameters, and adaptively generate time slot time-division control scheduling parameters based on the task processing load assessment parameters to configure the duration of time slot A and time slot B in the next preset time window.

2. The integrated communication and navigation receiver baseband architecture according to claim 1, characterized in that, The reusable DFE module uses a high-multiplexed operating clock for time division multiplexing, the frequency of which is greater than a predetermined multiple of the maximum sampling rate of the input signal. The reusable DFE module receives the sampling data of GNSS signals and MF-TDMA communication signals through a ping-pong buffering method, and performs mixing, filtering and downsampling processing on the two input signals using time division multiplexing.

3. The integrated communication and navigation receiver baseband architecture according to claim 1, characterized in that, The size of the MF-TDMA symbol buffer module is configured to store baseband symbol data for at least two MF-TDMA burst frames. The storage space for each MF-TDMA burst frame is determined based on the maximum symbol rate, sampling multiple, number of bytes per symbol, and maximum time slot per frame. It supports writing another frame of data while reading one frame of data.

4. The integrated communication and navigation receiver baseband architecture according to claim 1, characterized in that, The task processing load evaluation parameters include: The average carrier-to-noise ratio of GNSS signals is obtained by calculating the carrier-to-noise ratio of each tracked satellite, then summing the carrier-to-noise ratios of all tracked satellites and calculating the average value. The number of burst frames to be processed in MF-TDMA communication is calculated from the number of MF-TDMA symbols to be processed in the MF-TDMA symbol buffer module; The signal power of the MF-TDMA burst signal is estimated by the reusable DFE module from the received MF-TDMA signal.

5. The integrated communication and navigation receiver baseband architecture according to claim 4, characterized in that, The load assessment and task scheduling coprocessing module adaptively generates the time-slot time-division control scheduling parameters based on the task processing load assessment parameters, specifically including: When the average carrier-to-noise ratio is greater than the first carrier-to-noise ratio threshold, the duration quota of time slice B is reduced; when the average carrier-to-noise ratio is less than the second carrier-to-noise ratio threshold, the duration quota of time slice B is increased; the first carrier-to-noise ratio threshold is greater than or equal to the second carrier-to-noise ratio threshold. When the number of burst frames is less than the frame number threshold, the duration quota of time slice A is reduced; when the number of burst frames is greater than or equal to the frame number threshold, the duration quota of time slice A is increased. When the signal power is greater than the power threshold, the duration quota of time slice A is reduced; when the signal power is less than or equal to the power threshold, the duration quota of time slice A is increased.

6. The integrated communication and navigation receiver baseband architecture according to claim 5, characterized in that, When the demand for increasing the time slot A duration quota competes with the demand for increasing the time slot B duration quota, a competition processing strategy that prioritizes GNSS signal processing is adopted to ensure that the allocated duration of time slot B is greater than or equal to the allocated duration of time slot A.

7. The integrated communication and navigation receiver baseband architecture according to claim 1, characterized in that, A strategy based on system indicator priority is adopted to design optional AB time slice configuration levels. The time-sharing configuration of the corresponding level is selected according to the increase or decrease of the duration of time slice A and time slice B.

8. The integrated communication and navigation receiver baseband architecture according to claim 1 or 7, characterized in that, The duration configuration of time slot A and time slot B includes: when the duration configuration of time slot A is 0, the entire preset time window is allocated to time slot B to achieve full-time slot GNSS reception; when the duration configuration of time slot B is 0, the entire preset time window is allocated to time slot A to achieve full-time slot MF-TDMA communication.

9. A baseband signal processing method for an integrated communication and navigation receiver, applied to the baseband architecture of the integrated communication and navigation receiver according to any one of claims 1 to 8, characterized in that, include: The received GNSS signals and MF-TDMA communication signals are digitally processed in a time-division multiplexing manner using a reusable DFE module to generate baseband signals. The GNSS signal coprocessing module receives and processes GNSS baseband signals from the reusable DFE module. The MF-TDMA baseband symbol data stream from the reusable DFE module is cached through the MF-TDMA symbol caching module. The AB time-division control module divides the preset time window into time slot A and time slot B, and controls the communication and navigation service processing module to perform MF-TDMA communication signal processing tasks or remain idle in time slot A, and to perform GNSS signal processing tasks in time slot B. The load assessment and task scheduling coprocessing module evaluates the task processing load in real time, obtains assessment parameters, and adaptively generates time slot time-division control scheduling parameters for configuring the duration of time slot A and time slot B in the next preset time window based on the task processing load assessment parameters.

10. A computer system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the computer program is executed by the processor, it implements the processing steps of the AB time-division control module, the load assessment and task scheduling coprocessing module, and the communication and navigation service processing module in the baseband signal processing method of the integrated communication and navigation receiver according to claim 9.

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