Method and system for time synchronization of mesh ad hoc network nodes based on non-contention prach

Abstract

The application belongs to the technical field of network nodes, and particularly relates to a MESH self-organizing network node time synchronization method and system based on a non-competition PRACH. First, a channel is listened to for a cycle after starting, the surrounding node condition is confirmed, then in the next cycle, PRACH data and which time slots are occupied by the broadcast to send data are sent in the PRACH time slot in the broadcast subframe. Next, the time difference information of the neighbor node is checked by using the PRACH signal, and all nodes perform time synchronization to the minimum ID node. Then, IFFT transformation enters the time domain, a CP cycle prefix is added, a MIMO multipath fading channel is designed, the maximum Doppler is selected, a frequency offset is added, and a signal-to-noise ratio is added. Finally, the receiving node performs correlation operation on the PRACH sequence received in the broadcast subframe and the local original sequence in the frequency domain, and the position of the correlation peak obtained is the TA time delay between nodes. The TA value is broadcast in the broadcast channel, the MESH self-organizing network time synchronization is realized, and the data collision and packet loss problem caused by the multi-node competition for the same time slot resource is solved.

Description

Technical Field

[0001] This invention belongs to the field of network node technology, specifically relating to a time synchronization method and system for MESH self-organizing network nodes based on non-contention PRACH. Background Technology

[0002] In a WiFi mesh network, numerous nodes transmit their own data while also acting as intermediaries for other user nodes. All user nodes share and compete for the same communication medium. Collisions and retransmissions increase with network load. This leads to a problem: multiple user nodes may send the same preamble sequence to the eNB using the same PRACH resource in the same subframe, hoping to obtain resource authorization from the eNB. The eNB cannot identify which user node initiated the request. Therefore, each user node needs to send a unique message (MSG3) specific to itself, and the eNB must send a return message (MSG4) to the sending user node to confirm which user node has successfully connected. This problem causes frequent collisions and packet loss due to user nodes consuming time slot resources to transmit data, with collisions and retransmissions increasing with network load. This problem is particularly amplified and frequent in self-organizing mesh networks without base stations, and time slot resource collisions are unresolved. Furthermore, due to the large number of nodes and the fact that WiFi mesh networks are multi-hop networks, this inherent advantage often leads to contention-based data collisions, resulting in poor security performance. Figure 1 As shown. Summary of the Invention

[0003] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by this invention is to provide a time synchronization method and system for MESH self-organizing network nodes based on non-contention PRACH, in which each user node completes PRACH access within its own fixed frame time slot. This avoids contention when user nodes occupy time slot resources to send PRACH resource data, and solves the collision caused by contention when user nodes occupy time slots to send data, reducing error retransmissions and improving the security and efficiency of MESH self-organizing networks.

[0006] To solve the above technical problems, this invention provides the following technical solution: a MESH self-organizing network node time synchronization method based on non-contention PRACH, comprising: determining the node status in one round of channel monitoring; in the next round of cycle, the node selects its own fixed broadcast subframe to send PRACH data and broadcast occupied data subframes; allocating sequences; selecting the node with the smallest ID as the master clock; performing IFFT transformation to enter the time domain; inserting CP; designing a MIMO multipath fading channel; selecting the maximum Doppler, frequency offset, and signal-to-noise ratio; the receiving node performs correlation operations in the frequency domain using the received PRACH sequence and its local original sequence to obtain the TA value; and broadcasting the value in its own broadcast subframe. Figure 2 As shown.

[0007] As a preferred embodiment of the MESH self-organizing network node time synchronization method based on non-contention PRACH described in this invention, the node configuration includes allocating fixed time slot resources for random PRACH access.

[0008] In the fixed broadcast subframe design for each node, PBCH data and PRACH data each occupy one time slot. The broadcast subframe length is 2ms and has two time slots. Each time slot has a total of 14 OFDM symbols. The last GAP length of the broadcast subframe is 3320Ts, and the cell coverage transmission distance is 32km.

[0009] Each user node is allocated a fixed frame of 20ms in each round of broadcasting, including 1 broadcast subframe and 9 data subframes, with the broadcast subframe located at the very beginning;

[0010] When a user node needs to send data, it only sends PRACH data and broadcast-occupied data subframes in the PRACH time slots that belong to its fixed broadcast subframes.

[0011] As a preferred embodiment of the MESH self-organizing network node time synchronization method based on non-contending PRACH described in this invention, the allocation sequence includes:

[0012] At the transmitting end, different PRACH sequences are assigned to the 32 MESH self-organizing network nodes, using ZC sequences, with the expression:

[0013]

[0014] Where, x u (n) is the ZC sequence expression, u is the root index of the ZC sequence, n is the sequence index, and N ZC is the length of the ZC sequence.

[0015] As a preferred embodiment of the non-contending PRACH-based MESH self-organizing network node time synchronization method described in this invention, the allocation sequence further includes allocating two sequences, u=1 and u=556, as the original sequences based on the odd or even number of the user node ID, with the following expressions:

[0016]

[0017]

[0018] Define frequency domain data X, with the expression:

[0019] X(k+m*576+4)=x u (k), k∈[0,N] ZC -1]

[0020] Where k is x u (k) is the sequence number, and m is the number of access resource blocks;

[0021] Random access resource block allocation is represented as:

[0022]

[0023] Where floor is the base value and Nid is the node's ID value;

[0024] After padding the frequency domain data X with zeros to 8192 points, the defined frequency domain length is 8192Ts, expressed as:

[0025]

[0026] Where XF represents the zero-padded frequency domain data;

[0027] Perform an inverse IFFT to enter the time domain; the expression is:

[0028]

[0029]

[0030] Where S0(k) = ifft(XF), k∈[0, 8191], is the time-domain data after IFFT transformation; CS determines the cyclic shift value of a ZC sequence within the same random access resource block; mod is the remainder of the node ID, with a remainder less than or equal to 1. CS selecting 0 indicates selecting S0(k), and a remainder greater than 1 indicates selecting 1. S0(k) is cyclically shifted by 4096. prach (k) represents PRACH time-domain data.

[0031] As a preferred embodiment of the MESH self-organizing network node time synchronization method based on non-contention PRACH described in this invention, the design of the MIMO multipath fading channel includes inserting a CP cyclic prefix and designing a fading channel model that the transmitted data needs to pass through.

[0032] Define the sampling rate, design the pathDelay multipath delay and multipath relative fading avgPathgGains, select and generate the MIMO multipath fading channel, where dual antennas are used for transmission and reception, and PRACH data is detected and processed at the receiving node.

[0033] As a preferred embodiment of the MESH self-organizing network node time synchronization method based on non-contested PRACH described in this invention, the correlation operation includes obtaining a correlation peak through correlation operation between PRACH sequences, the user node performing CP cyclic prefix removal and FFT transformation on the received data to obtain frequency domain data, and then performing correlation operation with the original sequence stored locally to obtain the correlation peak, the position of the correlation peak being the TA value.

[0034] As a preferred embodiment of the MESH self-organizing network node time synchronization method based on non-contention PRACH described in this invention, the related calculations further include calculating the transmission delay x and master-slave time difference y between other adjacent nodes, expressed as:

[0035]

[0036] Where t1 is the time when the master node records the departure of the signal, t2 is the time when the slave node records the arrival of the signal, t3 is the time when the slave node sends the signal to the master node to leave, and t4 is the time when the master node records the arrival of the signal.

[0037] Data is sent in advance according to the receiving time of the receiving node, and the clock of each node is unified by the node with the smallest ID as the master clock to achieve time synchronization.

[0038] The entire process described above is as follows: Figure 3 As shown.

[0039] Another objective of this invention is to provide a time synchronization system for MESH self-organizing network nodes based on non-contention PRACH. This system can achieve precise time synchronization between nodes by designing fixed broadcast subframes on each node for PRACH access and broadcasting to occupy fixed data subframe resources. This solves the problems of low network efficiency, data loss, and security caused by data collisions due to multiple nodes competing for the same time slot resources in the prior art. This system can effectively manage and optimize wireless network resources, and improve the stability, reliability, and security of MESH self-organizing networks.

[0040] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a time synchronization system for MESH self-organizing network nodes based on non-contention PRACH, comprising a fixed frame time slot allocation module, a frame structure design module, a network parameter configuration module, a PRACH sequence generation module, a PRACH data transmission module, a PRACH data reception module, and a time synchronization module, such as... Figure 4 As shown;

[0041] The fixed frame time slot allocation module allocates a fixed broadcast subframe to each node for PRACH access and broadcasts it, occupying a fixed amount of data subframe resources.

[0042] The frame structure design module is used to design the specific structure of broadcast subframes, PRACH time slots, and PBCH time slots, so as to enable nodes to transmit data in PRACH.

[0043] The network parameter configuration module is used to configure the network parameters of this MESH self-organizing network.

[0044] The PRACH sequence generation module generates different PRACH sequences based on the IDs of all nodes in the network, which are used for related operations and time synchronization between nodes.

[0045] The PRACH data transmission module is used to determine the allocation of frequency domain resources to nodes based on the node ID, then perform IFFT transformation on the PRACH sequence to the time domain, insert CP, define the fading channel model, and finally generate the PRACH time domain signal that each node needs to transmit.

[0046] The PRACH data receiving module is used to receive PRACH data sent by other nodes at each node, configure receiving parameters, detect and synchronize PRACH sequences, perform channel estimation and equalization, and calculate the delay through related operations.

[0047] The time synchronization module obtains the TA value based on the received PRACH data from each node, thereby achieving time synchronization of all nodes.

[0048] A computer device includes a memory and a processor, the memory storing a computer program, characterized in that the processor executes the computer program to implement the steps of a MESH self-organizing network node time synchronization method based on non-contention PRACH.

[0049] A computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements the steps of a MESH self-organizing network node time synchronization method based on non-contention PRACH.

[0050] The beneficial effects of this invention are as follows: This invention uses the PRACH channel to maintain time synchronization for all nodes in a MESH self-organizing network, ensuring the normal operation of the entire network. It allocates fixed time slot resources to each user node to avoid contention when nodes occupy time slot resources to send PRACH resource data, and solves the collision caused by contention when user nodes occupy time slots to send data. This significantly reduces data collisions and retransmissions in the self-organizing network, and can greatly improve the security of the MESH self-organizing network. Attached Figure Description

[0051] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0052] Figure 1 This is a schematic diagram comparing the physical access of WIFI MESH with the MESH self-organizing network of the present invention, as provided in one embodiment of the present invention.

[0053] Figure 2 A flowchart of a MESH self-organizing network node time synchronization method based on non-contention PRACH provided in an embodiment of the present invention;

[0054] Figure 3 This is a flowchart illustrating the PRACH channel data transmission and reception process according to an embodiment of the present invention.

[0055] Figure 4 This is a schematic diagram showing the distribution of modules in a MESH self-organizing network node time synchronization system based on non-contested PRACH, provided as an embodiment of the present invention.

[0056] Figure 5 This is a structural diagram of a fixed frame for a user node provided in one embodiment of the present invention.

[0057] Figure 6 This is a schematic diagram of the PRACH and PBCH time slots in a broadcast subframe provided in an embodiment of the present invention.

[0058] Figure 7 This is a schematic diagram of the simulation results for a ZC sequence with a length of 558 provided in one embodiment of the present invention.

[0059] Figure 8 This is a schematic diagram of a defined PRACH sequence provided in one embodiment of the present invention.

[0060] Figure 9This is an overall schematic diagram illustrating how a user node's PRACH access and broadcast channel are conducted according to an embodiment of the present invention.

[0061] Figure 10 This is a schematic diagram of the master-slave time difference provided in one embodiment of the present invention.

[0062] Figure 11 The simulation results of user node 0, along with related peaks and TA values, are provided for one embodiment of the present invention.

[0063] Figure 12 The simulation results of user node 1, along with related peaks and TA values, are provided for one embodiment of the present invention.

[0064] Figure 13 The simulation results of user node 2, along with related peaks and TA values, are provided for one embodiment of the present invention.

[0065] Figure 14 The simulation results of user node 3, along with related peaks and TA values, are provided for one embodiment of the present invention.

[0066] Figure 15 The simulation results of user node 4, along with related peaks and TA values, are provided for one embodiment of the present invention.

[0067] Figure 16 The simulation results of user node 5, along with related peaks and TA values, are provided for one embodiment of the present invention.

[0068] Figure 17 Simulation results of user node 6, along with related peaks and TA values, are provided for one embodiment of the present invention.

[0069] Figure 18 The simulation results of user node 7, along with related peaks and TA values, are provided for one embodiment of the present invention. Detailed Implementation

[0070] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0071] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0072] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0073] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0074] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0075] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0076] Example 1

[0077] Reference Figures 2-8 As an embodiment of the present invention, a time synchronization method for MESH self-organizing network nodes based on non-contention PRACH is provided, comprising:

[0078] The monitoring channel determines the node status in one cycle, and the node selects its own fixed broadcast subframe to send PRACH data and broadcast occupied data subframe in the next cycle.

[0079] Assign the sequence, select the node with the smallest ID as the master clock, perform IFFT transformation to enter the time domain, insert CP, design the MIMO multipath fading channel, and select the maximum Doppler, frequency offset and signal-to-noise ratio;

[0080] The receiving node performs correlation operations between the received PRACH sequence and the local original sequence in the frequency domain to obtain the TA value, and then broadcasts it in its own broadcast subframe.

[0081] S1: The node status is determined in one round of channel monitoring. In the next round of cycle, the node selects its own fixed broadcast subframe to send PRACH data and broadcast occupied data subframe.

[0082] Furthermore, the node configuration includes allocating fixed frame time slot resources for PRACH random access;

[0083] In the fixed broadcast subframe design for each node, PBCH data and PRACH data each occupy one time slot. The broadcast subframe length is 2ms and has two time slots. Each time slot has a total of 14 OFDM symbols. The last GAP length of the broadcast subframe is 3320Ts, and the cell coverage transmission distance is 32km.

[0084] Each user node is allocated a fixed 20ms frame in each round. The frame includes one broadcast subframe and nine data subframes, with the broadcast subframe at the very beginning.

[0085] It should be noted that in this invention, the random access method adopted by the MESH self-organizing network is non-contention-based random access. Since no base station is used, user nodes are allowed to transmit data in the PRACH, and each user node is allocated a fixed frame of 20ms in each round of broadcasting, including one broadcast subframe and nine data subframes. Each user node broadcasts during its own broadcast time period and sends PRACH resources in the PRACH time slot of its fixed broadcast subframe. In this way, other user nodes will learn about the PRACH data through the PRACH time slot of the broadcast channel, and then use the local sequence to perform correlation calculations to obtain the TA value. They will also set their own broadcast time to broadcast on their own fixed frame and send PRACH resources in the PRACH time slot of the broadcast subframe, as well as decide which data subframe to place the TA value between the broadcast and the corresponding node. In this way, the PRACH channel can be used for the random access process.

[0086] It should also be noted that in each user node's fixed broadcast subframe, PBCH data and PRACH data each occupy one time slot, meaning the broadcast subframe length is 2ms and has two time slots: a 1ms PBCH time slot followed by a 1ms PRACH time slot. Each user node broadcasts in the broadcast subframe which resources it has occupied in the data subframe, and updates the received resource occupancy information of other nodes locally to prevent collisions during resource allocation. Figure 5 As shown.

[0087] It should also be noted that in the PBCH slot of the broadcast subframe, the 14 OFDM symbols are allocated as follows: the synchronization sequence consists of two identical ZC sequences, each 512Ts long, with a 72Ts CP added at the beginning, forming the first OFDM symbol. The synchronization sequence is used for coarse synchronization to obtain frequency offset and initial position. The broadcast data is 12 OFDM symbols long. A pilot symbol is inserted after the 6th broadcast data OFDM symbol, i.e., the 8th OFDM data symbol, used for piloting. The function of the pilot is channel estimation and equalization of channel data. The remaining 12 OFDM symbols in the PBCH slots are used to store broadcast data. Each OFDM symbol is 1096Ts long, including a 72Ts CP. Next is the PRACH slot, with 11 OFDM symbols used as PRACH resources for random access. The subframe ends with a guard interval (GAP) of 3320Ts (to ensure a maximum coverage range of 30km). This is the entire composition of the broadcast subframe. Figure 6 As shown.

[0088] It should also be noted that the designed MESH self-organizing network is a "multi-hop" network, a technology in which devices transmit their own data while also acting as relays for data transmission to other devices. Since each user node is a central node, if the availability of a user node decreases, the data will automatically reselect a node for transmission. If user node A broadcasts, other user nodes on the bus can detect this data; those that are theirs will send an acknowledgment, and those that are not will discard it. However, if user node A wants to send data to user node B, but node B is far away from user node A, exceeding the transmission distance of the MESH self-organizing network, then an intermediate node C between node A and node B is needed to assist in the transmission. That is, after node C receives the data sent to node B in node A's broadcast, it broadcasts it in its own broadcast subframe and sends the data to user node B. This fully leverages the advantages of MESH self-organizing networks: high penetration and long transmission distance.

[0089] It should also be noted that a key characteristic of star networks is that all user nodes communicate with a central user node. The central user node is responsible for listening to data packets from all nodes and forwarding them to the corresponding destination nodes. Star networks are widely used in computer networks. If a mesh ad hoc network is designed using a star topology, the central user node acts as the master clock node, and the clocks of the other nodes are synchronized with it. When another node, such as node A, broadcasts using its fixed time slot resources, the central node receives data from node A that it wants to send to node B. It then stores the data in a data subframe within its fixed frame and broadcasts it as data from node A to node B. In this way, nodes A and B can successfully exchange data. Because each node is allocated a fixed time slot resource in this scheme, multiple devices will not compete for the same wireless resource.

[0090] It should also be noted that the characteristic of a chain network is that the nodes are distributed in a chain, and only adjacent nodes can communicate directly. For example, user nodes 0, 1, 2, and 3 are distributed in a chain. User nodes 1, 2, and 3 send data to node 0, but node 3 needs nodes 2 and 1 as relays, and node 2 needs node 1 as a relay. After receiving the data sent to node 0 by node 3 in its broadcast, node 2 broadcasts in its own broadcast subframe to tell other nodes which data subframe it sent to node 0 and which data node 3 sent to node 0 were placed on. After receiving the broadcast from node 2, node 1 broadcasts in its own broadcast subframe to tell other nodes which data subframe node 2 sent to node 0 and which data node 3 sent to node 0 were placed on. In this way, node 0 successfully receives the data sent by nodes 3 and 2, which fully utilizes the advantages of MESH self-organizing networks, namely high penetration and long transmission distance.

[0091] S2: Assign the sequence, select the node with the smallest ID as the master clock, perform IFFT transformation to enter the time domain, insert CP, design the MIMO multipath fading channel, and select the maximum Doppler, frequency offset and signal-to-noise ratio;

[0092] Furthermore, the allocation sequence includes,

[0093] At the transmitting end, different PRACH sequences are assigned to the 32 MESH self-organizing network nodes, using ZC sequences, with the expression:

[0094]

[0095] Where, x u (n) is the ZC sequence expression, u is the root index of the ZC sequence, n is the sequence index, and N ZC This is the length of the ZC sequence, which is 557 here;

[0096] It should be noted that the length of the ZC sequence is usually a prime number. This is because the autocorrelation function of the ZC sequence reaches its minimum at 0, and the autocorrelation function is also very small when it is a non-zero integer multiple. This gives the ZC sequence good autocorrelation characteristics. When the ZC sequence length is even, the autocorrelation function will show a peak at 0, thus reducing the autocorrelation performance. Using ZC sequences with composite lengths may cause their subsequences to interfere with other codes. In addition, choosing a non-prime ZC sequence length will result in poor suppression around the correlation peak, and spurious signals will appear next to the correlation peak, directly affecting the determination of the correlation peak position. Therefore, in order to obtain better autocorrelation performance, the length of the ZC sequence is usually chosen to be a prime number. Longer ZC sequences can achieve higher autocorrelation levels, but they will increase computational complexity and power consumption. Since the subsequent random access resource block length is 576, this scheme chooses a ZC sequence length that is less than 576 but close to 576 as a prime number to ensure a high autocorrelation level. Finally, a ZC length of 557 is chosen, and the extra space corresponding to the random access resource block length of 576 is used as an interval to prevent interference. Figure 7 The simulation results were obtained using a ZC sequence length of 558, which is a non-prime number. Figure 7 As observed, the suppression effect around the correlation peak in the simulation results with a sequence length of 558 is very poor, there are obvious spurious waveforms next to the correlation peak, and the position of the correlation peak in the simulation results is shown at 0 (the position in the figure is at 256 because it was previously shifted by 256 to make the correlation peak appear in the middle of the figure for easier observation), and the correct TA value cannot be obtained. Therefore, this scheme selects a ZC length of 557 for simulation optimization.

[0097] Furthermore, the allocation sequence also includes allocating two sequences, u=1 and u=556, as the original sequence based on the parity of the user node ID, with the following expressions:

[0098]

[0099]

[0100] Define frequency domain data X, with the expression:

[0101] X(k+m*576+4)=x u (k), k∈[0,N] ZC -1]

[0102] Where m is the number of access resource blocks;

[0103] It should be noted that m is determined by the user node ID value, and m determines which random access resource block in the frequency domain the PRACH is transmitted in. Since the designed MESH ad hoc network has a total of 32 nodes, with node ID values ​​ranging from 0 to 31, m ranges from 0 to 7, resulting in a total of 8 random access resource blocks. Each random access resource block allows 4 nodes to perform random access. The broadcast has already specified the allowed resource block indexes for each node ID; for example, when m=0, the random access resource block is accessed by nodes 0, 1, 2, and 3.

[0104] Random access resource block allocation is represented as:

[0105]

[0106] Where floor is the base value and Nid is the node's ID value;

[0107] After padding the frequency domain data X with zeros to 8192 points, the defined frequency domain length is 8192Ts, expressed as:

[0108]

[0109] Where XF represents the zero-padded frequency domain data;

[0110] It should be noted that the defined frequency domain length is 8192Ts because subsequent steps involve IFFT (Inverse Fast Fourier Transform) and FFT (Fast Fourier Transform). Using a frequency domain data length that is an integer power of 2 can significantly improve the computational efficiency of FFT and IFFT. Since the frequency domain length occupied by the eight random resource blocks already exceeds 4096Ts, the final selected frequency domain data length is 8192Ts.

[0111] Perform an inverse IFFT to enter the time domain; the expression is:

[0112]

[0113]

[0114] Where S0(k) = ifft(XF), k∈[0, 8191], is the time-domain data after IFFT transformation; CS determines the cyclic shift value of a ZC sequence within the same random access resource block; mod is the remainder of the node ID, with a remainder less than or equal to 1. CS selecting 0 indicates selecting S0(k), and a remainder greater than 1 indicates selecting 1. S0(k) is cyclically shifted by 4096. prach (k) represents PRACH time-domain data.

[0115] It should be noted that the CS value is determined by the user ID. The node ID is then modulo 4 to distinguish nodes with remainders of 0, 1, 2, and 3. Nodes with remainders of 0 and 1 have a CS value of 0, while nodes with remainders of 2 and 3 have a CS value of 1. Nodes with remainders of 2 and 3 need to undergo a cyclic shift of half a cycle after the IFFT transformation. This is because the cyclic shift amount of the random access sequence specified in the broadcast is 4096Ts, or half a cycle. Since different original sequences have already been assigned based on the parity of the user node ID value, and 8 random access resource blocks are used, with each random access resource block allowing 4 nodes to perform random access, the above process has assigned different PRACH sequences to the 32 MESH self-organizing network nodes.

[0116] Furthermore, a CP cyclic prefix is ​​inserted into the PRACH data, and a fading channel model is designed for the data transmission.

[0117] It should be noted that after the IFFT transformation, the resulting time-domain data length is 8192 Ts. Due to ICI (Inter-Carrier Interference) occurring during data transmission, a cyclic prefix (CP) is inserted into the guard interval. The selected CP length is 2048 Ts, so the final time-domain data length is 10240 Ts. At this point, the transmitted PRACH data is complete. The PRACH sequence is defined as follows: Figure 8 As shown.

[0118] The sampling rate fs is defined as 15.36e6. The pathDelay multipath delay and the multipath relative fading avgPathgGains are designed. A MIMO multipath fading channel is selected and generated. The transmission and reception use dual antennas. PRACH is transmitted only on antenna 0. The maximum Doppler is selected as 100. The frequency offset dalta_f is added as 100. The signal-to-noise ratio snr is added as 100. The receiving node detects and processes the PRACH data. The design and processing of the transmitted data and the entire transmission system flow are shown above.

[0119] It should be noted that LTE offers several bandwidth options, such as 20MHz and 10MHz. For example, LTE supports a bandwidth of 10MHz, corresponding to 600 subcarriers. The subcarrier spacing is typically 15kHz, resulting in an effective bandwidth of 6*100*15kHz = 9MHz, with the remaining 1MHz used for spectrum leakage redundancy. In practice, due to the requirement for the nearest IFFT points, the closest point to 600 is 1024. Therefore, the transmitting end needs to perform a 1024-point IFFT, resulting in a total bandwidth of 15kHz*1024 = 15.36MHz, which is called the minimum sampling signal bandwidth. Of these 1024 subcarriers, only the middle 600 transmit data, while the remaining two outer subcarriers are empty (0). This means the other 424 subcarriers do not transmit data, so we consider LTE to occupy 10MHz of bandwidth. Our designed MESH self-organizing network communication system uses 10MHz bandwidth corresponding to 600 subcarriers, but also supports 5MHz and 2.5MHz. The OFDM length must correspond to the IFFT point requirement, so the designed number of subcarriers in the frequency domain is 1024. In reality, only 600 subcarriers are usable, with the remaining 424 subcarriers not carrying data. In the PRACH channel of this embodiment, each frame has 10 subframes, and each subframe corresponds to two time slots, totaling 20 time slots. Each time slot (RB) has 12 subcarriers, so the PBCH channel requires 240 subcarriers for access; therefore, a 5MHz bandwidth is chosen.

[0120] It should also be noted that since the entire MESH self-organizing network uses a 10M bandwidth, the actual data transmission uses 600 subcarriers, the total number of subcarriers is 1024, the subcarrier spacing is 15kHz, the sampling rate is 15.36MHz (1024*15kHz), the system uses TDD mode, and Ts is defined as 1 / 15.36e6s.

[0121] It should also be noted that, since the access time slot needs to overcome the propagation delay of the uplink and the interference caused by the user's uplink, a sufficient guard interval needs to be reserved in the time slot design. This guard interval is called GAT. The length of GAT determines the access radius that can be supported: the cell coverage distance is GAT*c / 2, where c is the speed of light. Since the last part of the designed broadcast subframe is the guard interval GAP, with a length of 3320Ts, the designed MESH self-organizing network cell coverage transmission distance is 32km, which exceeds 30km.

[0122] S3: The receiving node performs correlation operations between the received PRACH sequence and the local original sequence in the frequency domain to obtain the TA value, and selects its own broadcast subframe in the next broadcast time to broadcast this TA value and send PRACH resources in the PRACH time slot.

[0123] Furthermore, the correlation operation includes obtaining a correlation peak through correlation operations between PRACH sequences. The user node performs a series of CP cyclic prefix removal and FFT transformations on the received data to obtain frequency domain data, and then performs correlation operations with the original sequence stored locally to obtain the correlation peak. The position of the correlation peak is the TA value.

[0124] Furthermore, the related calculations include calculating the transmission delay x and master-slave time difference y between the node and other adjacent nodes, expressed as:

[0125]

[0126] Where t1 is the time when the master node records the departure of the signal, t2 is the time when the slave node records the arrival of the signal, t3 is the time when the slave node sends the signal to the master node to leave, and t4 is the time when the master node records the arrival of the signal.

[0127] Data is sent in advance according to the receiving time of the receiving node, and the clock of each node is unified by the node with the smallest ID as the master clock to achieve time synchronization.

[0128] Example 2

[0129] The second embodiment of the present invention differs from the first embodiment in that:

[0130] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0131] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0132] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0133] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0134] Example 3

[0135] Reference Figure 4 This is the third embodiment of the present invention. This embodiment provides a home load identification system based on automatic feature enhancement, including a fixed frame time slot allocation module, a frame structure design module, a network parameter configuration module, a PRACH sequence generation module, a PRACH data transmission module, a PRACH data reception module, and a time synchronization module.

[0136] The fixed frame time slot allocation module allocates a fixed broadcast subframe to each node for PRACH access and broadcasts it, occupying a fixed amount of data subframe resources.

[0137] The frame structure design module is used to design the specific structure of broadcast subframes, PRACH time slots, and PBCH time slots, so as to enable nodes to transmit data in PRACH.

[0138] The network parameter configuration module is used to configure the network parameters of this MESH self-organizing network.

[0139] The PRACH sequence generation module generates different PRACH sequences based on the IDs of all nodes in the network, which are used for related operations and time synchronization between nodes.

[0140] The PRACH data transmission module is used to determine the allocation of frequency domain resources to nodes based on the node ID, then perform IFFT transformation on the PRACH sequence to the time domain, insert CP, define the fading channel model, and finally generate the PRACH time domain signal that each node needs to transmit.

[0141] The PRACH data receiving module is used to receive PRACH data sent by other nodes at each node, configure receiving parameters, detect and synchronize PRACH sequences, perform channel estimation and equalization, and calculate the delay through related operations.

[0142] The time synchronization module obtains the TA value based on the received PRACH data from each node, thereby achieving time synchronization of all nodes.

[0143] Example 4

[0144] Reference Figure 9-18 As a fourth embodiment of the present invention, a time synchronization method for MESH self-organizing network nodes based on non-contested PRACH is provided. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and experiments.

[0145] The following section is an embodiment of the present invention, which provides a time synchronization method for MESH self-organizing network nodes based on non-contention PRACH, including:

[0146] This embodiment provides a method for checking the TA value between nodes using the PRACH signal.

[0147] Since there are no base stations in the MESH ad hoc network design, we use the node with the smallest ID value among the 32 user nodes as the master clock. Each user node synchronizes its time with the master clock by sending PRACH signals and obtains the TA transmission delay (time advance) between itself and other user nodes. After the synchronization process is completed, it searches for 20ms*1024 to confirm the status of neighboring nodes before setting its own broadcast time. If no synchronization sequence is detected, it is assumed that there are no neighboring nodes, and it selects its own time to send. When a neighboring node is found, it updates all neighbor information and waits for the next round of broadcast time to select its own broadcast subframe for broadcasting and send PRACH resources in the PRACH time slot. There are a total of 32 rounds, each round lasting 32*20ms, or 32 frames. The number of frames occupied by each user node in each round of broadcasting is fixed, which means non-contention-based random access is used. When user node 0 first enters the MESH ad hoc network, after confirming that there are no neighboring nodes, it sets its own broadcast time, occupies the first frame for broadcasting, and sends PRACH resources in the PRACH time slot of the broadcast subframe. In subsequent communications, the first frame is always allocated to node 0. Then, user node 1 enters the MESH network, confirms that only user node 0 is present, receives its PRACH signal, performs related calculations to obtain the TA value, and then sets its broadcast time in the next round, occupying the second frame to broadcast and sending PRACH resources in the PRACH time slot of the broadcast subframe. It also determines which data subframe to place the TA value between the broadcast and node 0. In subsequent communications, the second frame is always allocated to node 1. Next, user node 2 enters the MESH network, confirms that only user nodes 0 and 1 are present, receives their PRACH signals, performs related calculations, and then sets its broadcast time in the next round, occupying the third frame to broadcast and sending PRACH resources in the PRACH time slot of the broadcast subframe. It also determines which data subframe to place the TA value obtained from the related calculations between the broadcast and nodes 0 and 1. In subsequent communications, the third frame is always allocated to node 2. The remaining 29 nodes follow the same pattern. After 32 rounds (20ms * 1024), the entire MESH ad hoc network completes time synchronization. Figure 9 As shown.

[0148] The correlation peak is obtained through correlation operations between PRACH sequences, and the location of the correlation peak is the TA value. The sum of the transmission delay x between the node and other neighboring nodes and the master-slave time difference y is the TA value required for the simulation. The master node records the signal departure time t1, and the slave node records the signal arrival time t2. The slave node sends a signal to the master node at departure time t3, and the master node records the signal arrival time t4. For example... Figure 10As shown, knowing the TA value of adjacent nodes, user nodes can send data in advance based on the receiving node's receiving time. This allows receiving users to simultaneously receive data from other nodes at the specified time, and also enables time synchronization by using the node with the smallest ID as the master clock and unifying the clocks of all nodes.

[0149]

[0150] Using user nodes with IDs 0-7 as a simulation example, the designed PRACH channel is simulated. Since each resource block allows four nodes to perform random access, the eight nodes (0-7) only need to use two resource blocks sequentially, i.e., m = 0 and 1. After the receiving node receives the transmitted data from other nodes (0-7), it first removes the 2048Ts cyclic prefix (CP). CP is added by the sender before transmitting the PRACH data to prevent ICI (Inter-Carrier Interference). After obtaining the 8192Ts PRACH data, an FFT Fourier transform is performed to enter the frequency domain. Then, the frequency domain data of the random access resource block when m=0 is extracted. This embodiment performs correlation operations in the frequency domain because the computational load is much smaller in the frequency domain compared to the time domain, reducing resource usage.

[0151] Finally, the extracted random access resource block frequency domain data were correlated with the original sequences u=1 and u=556 respectively, resulting in a total of 4 correlation peaks. Two correlation peaks were obtained from the correlation with the odd and even original sequences. We can observe that the positions of the two correlation peaks obtained from the odd and even original sequences differ by exactly Nfft / 2. Finally, the correlation peaks were extracted according to Nfft / 2, yielding the detected ID node and the corresponding frequency domain position of the correlation peak. The frequency domain position of the correlation peak is the TA value, which includes the master-slave time difference and transmission delay. The simulation results for user nodes 0-3, along with the correlation peaks and TA values, are shown below. Figure 11 , Figure 12 , Figure 13 , Figure 14 As shown. Similarly, the frequency domain data of the random access resource block when m=1 is extracted and correlated with the original sequences when u=1 and u=556, respectively. The simulation results of user nodes 0-3, as well as the correlation peak and TA value, are shown below. Figure 15 , Figure 16 , Figure 17 , Figure 18 As shown.

[0152] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A time synchronization method for MESH self-organizing network nodes based on non-contention PRACH, characterized in that: include, The monitoring channel determines the node status in one cycle, and the node selects its own fixed broadcast subframe to send PRACH data and broadcast occupied data subframe in the next cycle. The allocation sequence includes assigning different PRACH sequences to 32 MESH self-organizing network nodes at the transmitting end; the node ID value ranges from 0 to 31, the node with the smallest ID is selected as the master clock, the PRACH sequence is transformed by IFFT to enter the time domain, a CP cyclic prefix is ​​inserted into the PRACH data, the MIMO multipath fading channel for transmitting data is designed, the maximum Doppler, frequency offset and signal-to-noise ratio are selected, and finally the PRACH time domain signal to be transmitted by each node is generated; The receiving node performs correlation operations between the received PRACH sequence and the local original sequence in the frequency domain to obtain the TA value, and then broadcasts it in its own broadcast subframe; The node configuration includes allocating fixed time slot resources for PRACH random access; In the fixed broadcast subframe design for each node, PBCH data and PRACH data each occupy one time slot. The broadcast subframe length is 2ms and has two time slots. Each time slot has a total of 14 OFDM symbols. The last GAP length of the broadcast subframe is 3320Ts, and the cell coverage transmission distance is 32km. Each user node is allocated a fixed frame of 20ms in each round of broadcasting, including 1 broadcast subframe and 9 data subframes, with the broadcast subframe located at the very beginning; When a user node needs to send data, it only sends PRACH data and broadcast-occupied data subframes in the PRACH time slots that belong to its fixed broadcast subframe.

2. The MESH self-organizing network node time synchronization method based on non-contention PRACH as described in claim 1, characterized in that: The allocation sequence includes assigning different PRACH sequences to the 32 MESH self-organizing network nodes at the transmitting end, using ZC sequences, with the expression: in, For ZC sequence expressions, The root index of the ZC sequence. The sequence number. is the length of the ZC sequence.

3. The MESH self-organizing network node time synchronization method based on non-contention PRACH as described in claim 2, characterized in that: The allocation sequence also includes two sequences, u=1 and u=556, allocated based on the parity of the user node ID as the original sequence, with the following expressions: Define frequency domain data The expression is: in, for The serial number, The number of access resource blocks; Random access resource block allocation is represented as: in, It is about finding the bottom. This is the ID value of the node; frequency domain data After padding the sequence with zeros to 8192 points, the defined frequency domain length is 8192Ts, expressed as: in, This is the frequency domain data after zero padding; Perform an inverse IFFT to enter the time domain; the expression is: in, This is the time-domain data after IFFT transformation. CS determines the cyclic shift value of a ZC sequence within the same random access resource block. mod is the remainder of the node ID, with a remainder less than or equal to 1. Selecting 0 for CS indicates selection. If the remainder is greater than 1, CS selects 1. Circular shift 4096, This is PRACH time-domain data.

4. The MESH self-organizing network node time synchronization method based on non-contention PRACH as described in claim 3, characterized in that: The MIMO multipath fading channel includes the insertion of a CP cyclic prefix, and the design of the fading channel model that the transmitted data needs to pass through; Define the sampling rate, design the pathDelay multipath delay and multipath relative fading avgPathgGains, select and generate the MIMO multipath fading channel, where dual antennas are used for transmission and reception, and PRACH data is detected and processed at the receiving node.

5. The MESH self-organizing network node time synchronization method based on non-contention PRACH as described in claim 4, characterized in that: The correlation operation includes obtaining the correlation peak through correlation operation between PRACH sequences. The user node performs CP cyclic prefix removal and FFT transformation on the received data to obtain frequency domain data, and then performs correlation operation with the original sequence stored locally to obtain the correlation peak. The position of the correlation peak is the TA value.

6. The MESH self-organizing network node time synchronization method based on non-contention PRACH as described in claim 5, characterized in that: The related calculations include calculating the transmission delay between the node and other adjacent nodes. Master-slave time difference The expression is: ， in, The master node records the time when the signal leaves. To record the arrival time of signals from the nodes, The time when the slave node sends a signal to the master node to leave. The master node records the arrival time of the signal; Data is sent in advance according to the receiving time of the receiving node, and the clock of each node is unified by the node with the smallest ID as the master clock to achieve time synchronization.

7. A system employing the non-contending PRACH-based MESH self-organizing network node time synchronization method as described in any one of claims 1 to 6, characterized in that: It includes a fixed frame time slot allocation module, a frame structure design module, a network parameter configuration module, a PRACH sequence generation module, a PRACH data transmission module, a PRACH data reception module, and a time synchronization module; The fixed frame time slot allocation module allocates a fixed broadcast subframe to each node for PRACH access and broadcasts it, occupying a fixed amount of data subframe resources. The frame structure design module is used to design the specific structure of broadcast subframes, PRACH time slots, and PBCH time slots, so as to enable nodes to transmit data in PRACH. The network parameter configuration module is used to configure the network parameters of this MESH self-organizing network. The PRACH sequence generation module generates different PRACH sequences based on the IDs of all nodes in the network, which are used for related operations and time synchronization between nodes. The PRACH data transmission module is used to determine the allocation of frequency domain resources to nodes based on the node ID, then perform IFFT transformation on the PRACH sequence to the time domain, insert CP, define the fading channel model, and finally generate the PRACH time domain signal that each node needs to transmit. The PRACH data receiving module is used to receive PRACH data sent by other nodes at each node, configure receiving parameters, detect and synchronize PRACH sequences, perform channel estimation and equalization, and calculate the delay through related operations. The time synchronization module obtains the TA value based on the received PRACH data from each node, thereby achieving time synchronization of all nodes.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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