A wireless self-synchronization method between 5G base stations

Abstract

This invention belongs to the field of 5G waveform-based mesh network communication and discloses a wireless self-synchronization method among 5G base stations. This invention solves the synchronization problem between nodes in a wireless mesh network in scenarios without a unified external high-precision clock source, ultimately ensuring clock self-synchronization among 5G base stations. In a time-division multiplexing (TDD) integrated 5G access and backhaul communication system, this invention adjusts the clock offset and frequency offset of each slave node based on the automatically selected master-slave node relationship, through the measurement of transmission delay and the exchange of delay information between master and slave nodes, to achieve clock self-synchronization of all network nodes, thereby ensuring clock synchronization of NR services on different nodes. This invention's method effectively reduces the subsequent time offset variation through frequency offset calibration, effectively improving the efficiency of time offset calibration and reducing the load on air interface signaling.

Description

Technical Field

[0001] This invention belongs to the field of 5G waveform-based Mesh network communication. Specifically, in a time-division multiplexing-based 5G access and backhaul integrated communication system, this invention introduces a method to achieve clock synchronization between nodes by adjusting the frequency, which solves the synchronization problem between nodes in a wireless Mesh network in scenarios without a unified external high-precision clock source, and ultimately ensures clock self-synchronization between 5G base stations. Background Technology

[0002] The time-division multiplexing (TDD) integrated 5G access and backhaul communication system simultaneously supports 5G NR services and inter-node relay communication. Each mesh network node achieves wireless connectivity by time-division multiplexing the same spectrum resources as the 5G NR services, forming a distributed multi-hop topology network. The 5G integrated access and backhaul system is a mobile communication network that does not rely on fixed infrastructure, featuring decentralization, self-organization, flexible network topology, and strong resilience. Under normal circumstances, the 5G integrated access and backhaul communication system relies on a unified satellite synchronization source to achieve high-precision synchronization between nodes. In the absence of a unified satellite synchronization source, nodes need to use independent synchronization algorithms to achieve clock self-synchronization, while simultaneously providing a clock synchronization source for 5G NR services, thereby ensuring that terminals accessing different 5G base stations can perform operations such as cell handover normally.

[0003] In satellite-denied applications, traditional clock synchronization algorithms primarily rely on time offset measurements to adjust the time slot boundaries of slave nodes, thereby achieving clock synchronization between nodes. This algorithm requires frequent, periodic adjustments to the time offset, resulting in significant signaling overhead. Furthermore, when the adjusted time offset is large, it can affect the normal transmission of underlying data in the 5G channel. Summary of the Invention

[0004] The main objective of this invention is to design a wireless self-synchronization method between 5G base stations for a time-division integrated communication system for 5G access and backhaul under satellite denial scenarios, so as to ensure the normal transmission of 5G services and data between Mesh network nodes, reduce the signaling overhead of synchronization, and avoid data interruption at the underlying level.

[0005] The technical solution adopted in this invention is as follows: A method for wireless self-synchronization between 5G base stations includes the following steps: Step 1: Define the time-division multiplexed 5G NR time slots and Mesh network time slots. Define periodic synchronization time slots on the Mesh network time slots to transmit the Mesh network's SSB signals. The SSB signals include synchronization signals and physical broadcast channel blocks. Initially, each Mesh network node uses blind search to detect its neighboring nodes, obtain basic information about each neighboring node, and determine the master-slave relationship between nodes. Step 2: Search for SSB signals sent by neighboring nodes from the node, obtain the SSB signal of the master node through initial frequency sweep, perform time delay measurement, align the local time slot boundary with the boundary of the master node time slot number and the receiving time slot, and complete the initial coarse synchronization. Step 3: After the slave node completes the initial coarse synchronization, it periodically sends its own SSB signal. After receiving the slave node's SSB signal, the master node measures the transmission delay from the slave node to the master node and sends the measured transmission delay to the slave node through a synchronization signaling message. After receiving the master node's SSB signal, the slave node measures the transmission delay from the master node to the slave node. When the slave node obtains the bidirectional time transmission delay between the master and slave nodes, it calculates the actual transmission delay and the deviation of the time slot boundary between the two nodes, adjusts the local time slot boundary, and aligns it with the boundary of the master node's transmission time slot to achieve initial clock synchronization between the master and slave nodes. Step 4: After the master and slave nodes complete the initial synchronization, the master node periodically measures the transmission delay corresponding to the SSB signal of each slave node and periodically broadcasts it to each slave node. The slave nodes calculate the frequency deviation of the clock between the master and slave nodes and calibrate the frequency deviation between the master and slave nodes through an adaptive frequency calibration algorithm.

[0006] Furthermore, in step 4, the frequency deviation between the master and slave nodes is calculated by the slave node, and the frequency and time deviations between the master and slave nodes are calibrated using an adaptive frequency calibration algorithm, specifically as follows: Step 401: Let the actual transmission delay between the master and slave nodes be Delay. Based on the transmission delay from the other node to this node measured by the master and slave nodes respectively (Delay_...),... 主节点测量 and Delay_ 从节点测量 Calculate the new clock offset between the two nodes within the current measurement period: Offset=(Delay_ 主节点测量 – Delay_ 从节点测量 ) / 2; Step 402, calculate the frequency deviation of the slave node relative to the master node: Frequency deviation = (Offset / Measurement interval) * Clock frequency; Step 403, adjust the frequency of slave nodes in stages: The target frequency of the slave node is the current slave node frequency plus the frequency deviation. The adjustment is carried out in two stages. Phase 1: First, adjust the frequency of the slave node according to "current frequency + 2 * frequency deviation", and start the measurement interval timer at the same time; Phase 2: After the timer for the measurement interval times out, the frequency of the slave node is adjusted according to "current frequency - frequency deviation".

[0007] The advantages of this invention compared to the prior art are: This invention effectively reduces the amplitude of subsequent time offset variations through frequency offset calibration, significantly improving the efficiency of time offset calibration and reducing the load on air interface signaling. Furthermore, this invention ensures clock synchronization among NR service base stations through a frequency offset adaptive adjustment mechanism between wireless mesh network nodes. This provides excellent protection for the normal service transmission of the time-division integrated 5G access and backhaul communication system under satellite denial scenarios, avoiding NR service interruptions caused by underlying time offset adjustments. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the phased frequency offset adjustment according to an embodiment of the present invention. Detailed Implementation

[0009] The invention will be further explained below with reference to the accompanying drawings.

[0010] A method for wireless self-synchronization between 5G base stations includes the following steps: Step 1: Define fixed time slots for sending synchronization signals and node configuration information for the Mesh network; Time-division multiplexing (TDD) 5G NR time slots and Mesh network time slots are defined. Periodic synchronization time slots are defined on the Mesh network time slots, with each node's synchronization time slot staggered. The actual location of each node's synchronization time slot is determined by its node ID. This synchronization time slot is used to transmit the Mesh network's SSB signal, which includes a synchronization signal and a Physical Broadcast Channel (PBCH). The SSB consists of the Mesh network's dedicated PSS (Primary Synchronization Signal), SSS (Secondary Synchronization Signal), and PBCH (Physical Broadcast Channel). The PSS and SSS are used to transmit the Mesh network's node ID information, while the PBCH is used to transmit the basic configuration information of the Mesh network nodes. Initially, each Mesh network node uses blind search to detect surrounding neighboring nodes, obtain basic information about each neighboring node, and determine the master-slave relationship between nodes.

[0011] Step 2: Perform the initial synchronization process; The node searches for SSB signals sent by neighboring nodes and obtains the master node's SSB signal through initial frequency sweep. It then performs delay measurement, aligns the local time slot boundary with the master node's time slot number and the boundary of the receiving time slot, and completes the initial coarse synchronization.

[0012] Step 3: Perform initial clock synchronization between master and slave nodes; After the slave node completes initial coarse synchronization, it periodically sends its own SSB signal. Upon receiving the slave node's SSB signal, the master node measures the transmission delay from the slave node to the master node and sends the measured transmission delay to the slave node via a synchronization signaling message. After receiving the master node's SSB signal, the slave node measures the transmission delay from the master node to the slave node. Once the slave node obtains the bidirectional time transmission delay between the master and slave nodes, it calculates the actual transmission delay between the two nodes and the deviation of the time slot boundary, adjusts its local time slot boundary to align with the boundary of the master node's transmission time slot, and achieves initial clock synchronization between the master and slave nodes. After completing self-synchronization, the slave node activates its NR time slot, allowing NR terminals to access the network.

[0013] Step 4: Perform the frequency offset calibration procedure; Once the master and slave nodes complete initial synchronization, the clocks of adjacent nodes are aligned in time slots, enabling normal transmission and reception. However, if there is a frequency deviation between the master and slave nodes' clock crystals, the time offset between the two nodes will gradually increase over time, potentially leading to subsequent loss of synchronization. Therefore, the master node needs to periodically measure the transmission delay corresponding to the synchronization signal of each slave node and periodically broadcast this information to the slave nodes. The slave nodes then continuously adjust the frequency offset to maintain clock synchronization with the master node.

[0014] After the master and slave nodes complete the initial synchronization, the master node periodically measures the transmission delay corresponding to the SSB signal of each slave node and periodically broadcasts it to each slave node. The slave nodes calculate the frequency deviation of the clock between the master and slave nodes and calibrate the frequency deviation between the master and slave nodes through an adaptive frequency calibration algorithm.

[0015] Assuming the master node measures the synchronization signal delay of the slave node within a period of T, the master node sends a transmission delay measurement to all surrounding slave nodes in each period. Each time a slave node receives the delay measurement from the master node, it calculates the clock offset between itself and the master node. Based on the clock offset, it calculates the frequency deviation (Delta_F) between the two nodes and then calculates the master node's current clock frequency. Subsequently, based on the frequency deviation between the master and slave nodes, the slave node adjusts its frequency in stages, calibrating the timing offset back within the measurement period and ultimately aligning its frequency with the master node's frequency.

[0016] Assuming that at time TOD_t0, the master node's master frequency is Freq_master_t0 and the slave node's master frequency is Freq_slave_t0, and at time TOD_t0, the slave node has completed the initial fine synchronization with the master node, then: TOD_master_t0 = TOD_slave_t0; TOD_master_t0 is the master node clock at time TOD_t0, and TOD_slave_t0 is the slave node clock at time TOD_t0. Assuming a measurement period T has elapsed, i.e. at time TOD_t1, the master node TOD is TOD_master_t1 and the slave node TOD is TOD_slave_t1, then the time deviation and frequency deviation have the following relationship: (TOD_master_t1 - TOD_ t0) / (TOD_slave_t1 - TOD_ t0) = Freq_master_t0 / Freq_slave_ t0 Assuming that after receiving a synchronization message from the master node, the slave node calculates the local clock offset between the two nodes as Offset, then: Offset = TOD_master_t1 - TOD_slave_t1; Assuming the initial frequency difference between the master and slave nodes is defined as Delta_F_t0, then: Delta_F_t0= Freq_master_t0 - Freq_slave_t0; Assuming the measurement period is calculated from the node according to T = TOD_slave_t1 - TOD_t0, then: Delta_F_t0 = (Offset / T) * Freq_slave_t0; When adjusting the time offset using frequency offset adjustment, the first stage first determines the target time duration T_phase1 for the time offset adjustment, and then calculates the additional frequency adjustment amount additional_DeltaF required to complete the time offset adjustment within this interval. Assuming the frequency offset adjustment magnitude of the slave node in the first stage is defined as Delta_F_phase1, then: Delta_F_phase1 = Delta_F_t0 + additional_DeltaF Assuming T_phase1 is set to T / n (where n is a number greater than or equal to 1), it means that within a duration of T / n, the frequency offset of the slave node needs to be adjusted to align TOD_slave with TOD_master. In this case, additional_DeltaF needs to be set according to the following formula: additional_DeltaF = n* Delta_F_t0; That is, during the first stage from TOD_slave_t1 to TOD_slave_t1 + T / n, the slave node's frequency is adjusted to Freq_slave_t0 + Delta_F_t0 + n* Delta_F_t0. Then, at TOD_slave_t1 + T / n, the slave node's frequency is adjusted to Freq_slave_t0 + Delta_F_t0. Through these two stages of adjustment, both the time and frequency offsets of the master and slave nodes are calibrated. Figure 1 As shown.

Claims

1. A method for wireless self-synchronization between 5G base stations, characterized in that, Includes the following steps: Step 1: Define the time-division multiplexed 5G NR time slots and Mesh network time slots. Define periodic synchronization time slots on the Mesh network time slots to transmit the Mesh network's SSB signals. The SSB signals include synchronization signals and physical broadcast channel blocks. Initially, each Mesh network node uses blind search to detect its neighboring nodes, obtain basic information about each neighboring node, and determine the master-slave relationship between nodes. Step 2: Search for SSB signals sent by neighboring nodes from the node, obtain the SSB signal of the master node through initial frequency sweep, perform time delay measurement, align the local time slot boundary with the boundary of the master node time slot number and the receiving time slot, and complete the initial coarse synchronization. Step 3: After the slave node completes the initial coarse synchronization, it periodically sends its own SSB signal. After receiving the slave node's SSB signal, the master node measures the transmission delay from the slave node to the master node and sends the measured transmission delay to the slave node through a synchronization signaling message. After receiving the master node's SSB signal, the slave node measures the transmission delay from the master node to the slave node. When the slave node obtains the bidirectional time transmission delay between the master and slave nodes, it calculates the actual transmission delay and the deviation of the time slot boundary between the two nodes, adjusts the local time slot boundary, and aligns it with the boundary of the master node's transmission time slot to achieve initial clock synchronization between the master and slave nodes. Step 4: After the master and slave nodes complete the initial synchronization, the master node periodically measures the transmission delay corresponding to the SSB signal of each slave node and periodically broadcasts it to each slave node. The slave nodes calculate the frequency deviation of the clock between the master and slave nodes and calibrate the frequency deviation between the master and slave nodes through an adaptive frequency calibration algorithm.

2. The wireless self-synchronization method between 5G base stations according to claim 1, characterized in that, In step 4, the frequency deviation between the master and slave nodes is calculated by the slave node. An adaptive frequency calibration algorithm is then used to calibrate the frequency and time offsets between the master and slave nodes. Specifically: Step 401: Let the actual transmission delay between the master and slave nodes be Delay. Based on the transmission delay from the other node to this node measured by the master and slave nodes respectively (Delay_...),... 主节点测量 and Delay_ 从节点测量 Calculate the new clock offset between the two nodes within the current measurement period: Offset=(Delay_ 主节点测量 – Delay_ 从节点测量 ) / 2; Step 402, calculate the frequency deviation of the slave node relative to the master node: Frequency deviation = (Offset / Measurement interval) * Clock frequency; Step 403, adjust the frequency of slave nodes in stages: The target frequency of the slave node is the current slave node frequency plus the frequency deviation. The adjustment is carried out in two stages. Phase 1: First, adjust the frequency of the slave node according to "current frequency + 2 * frequency deviation", and start the measurement interval timer at the same time; Phase 2: After the timer for the measurement interval times out, the frequency of the slave node is adjusted according to "current frequency - frequency deviation".

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