Underwater sound distributed cooperative parallel transmission method based on PD-NOMA

Abstract

The invention provides an underwater sound distributed cooperative parallel transmission method based on PD-NOMA. The underwater sound distributed cooperative parallel transmission method based on PD-NOMA comprises the steps that all nodes store a whole network topological structure; the receiving end sends an RTR packet, and if an interference risk exists, the reservation time is adjusted until no interference exists; after receiving the RTR packet, the transmitting end judges whether a signal transmitting demand exists or not; if yes, whether interference risks exist or not is judged; if there is no interference, sending a signal, and if there is interference, adjusting the sending time or entering a back-off state, and sending an SNT packet; the paired communication pairs send DATA data packets according to specified time, and the non-paired non-interference communication pairs send local data; if not, the transmitting end enters back-off; and after the receiving end receives the DATA packet, the paired communication pairs are decoded by using the SIC according to the decoding sequence, the unpaired communication pairs are directly decoded, effective signals are extracted, and an ACK reply packet is sent. The method has the advantages that task requirements and underwater acoustic channel characteristics are fully combined, and efficient scheduling and parallel transmission of communication pairs are achieved.

Description

Technical Field

[0001] The present application belongs to the field of underwater acoustic communication networks and underwater acoustic MAC protocols, and specifically relates to an underwater acoustic distributed collaborative parallel transmission method based on PD-NOMA. Background Art

[0002] In recent years, with the deepening of marine development, the demand for applications such as marine environmental monitoring, offshore exploration and disaster prevention has continued to increase. Traditional single-node underwater acoustic communication equipment and point-to-point communication modes have been unable to meet the diverse information interaction needs. These needs have spawned the construction of collaborative multi-user underwater acoustic communication networks to break the underwater information islands and achieve efficient information sharing.

[0003] However, the complexity and dynamics of underwater acoustic channels pose great challenges to communication networks, especially in multi-user scenarios, where efficient utilization and fair allocation of shared channels are crucial. In this context, the MAC (Medium Access Control) protocol, as a key technology for channel resource management and multi-user communication, plays a core coordination role and is one of the important contents in the research of underwater acoustic communication networks.

[0004] Existing MAC protocols mainly include methods based on channel monitoring, reservation and dynamic resource allocation. Although they can alleviate communication conflicts to a certain extent, they still have limitations such as insufficient resource utilization and high transmission delay. Non-Orthogonal Multiple Access (NOMA) has gradually attracted attention due to its potential to significantly improve spectrum utilization by multiplexing resources in the power domain or code domain. However, current research based on NOMA is mostly focused on central node control, lacking support for the flexibility and adaptability of dynamic underwater acoustic distributed networks. Summary of the invention

[0005] The purpose of this application is to overcome the shortcomings of the prior art such as insufficient resource utilization and high transmission delay.

[0006] In order to achieve the above objectives, this application proposes a PD-NOMA-based underwater acoustic distributed cooperative parallel transmission method, including:

[0007] Step 1: Each node obtains the ID and location information of surrounding nodes through broadcasting, stores the topology of the entire network, and constructs the transmission power matrix required for random pairing of nodes in the entire network;

[0008] Step 2: In each round of reservation, the receiver dynamically generates an RTR packet carrying the ID, location information, and transmission plan information of the communication pair according to the task requirements, and sends it without affecting the communication of other communication pairs. If there is an interference risk, the random backoff mechanism is used to adjust the reservation time until there is no interference;

[0009] Step 3: After receiving the RTR packet sent to the local area, the transmitter first determines whether there is a need to send a message; if so, the receiver conducts interference assessment based on the network status extracted from the previously monitored RTR packet, and determines whether there is an interference risk by analyzing the time overlap and power coverage of the channel occupancy; if there is no interference, send the message as planned; if there is interference, adjust the sending time or enter the backoff state through the communication pair pairing algorithm to ensure signal synchronization and achieve parallel transmission, and send the SNT signaling packet to inform the receiver of the pairing and decoding information;

[0010] Step 4: After the transmitter sends the SNT signaling packet, the paired communication pair sends the DATA data packet at the specified time, and the non-paired non-interference communication pair directly sends the DATA data packet; if the pairing is not successful, the transmitter enters the backoff until the end of this round of communication and then enters step 3 to retry pairing;

[0011] Step 5: After receiving the DATA packet, the receiver decodes it according to the decoding order in the SNT signaling packet, extracts the valid signal, and sends an ACK reply packet without affecting other communication pairs occupying the channel.

[0012] As an improvement of the above method, the transmit power matrix construction formula is:

[0013]

[0014] Where P(R) is the transmit power; SNR 0 is the receiving signal-to-noise ratio threshold; B 3dB (R) is the 3dB bandwidth corresponding to the optimal frequency; N(f) is the power spectrum density of the ambient noise; A(R,f) is the acoustic attenuation model; R is the transmission distance.

[0015] As an improvement of the above method, the method for determining whether there is interference risk is:

[0016] There is a risk of interference when the following formula is not satisfied:

[0017]

[0018] in, represents the time when the RTR packet arrives at the node numbered i; T sendRTR Indicates the scheduled time when the receiving end initiates the RTR packet; d i represents the distance from the receiving end to the i-node; c represents the data packet transmission speed; Indicates the time when the receiving end finishes receiving the RTR packet, T control Indicates the transmission time of the RTR packet; Indicates the time when node i receives a data packet from node j; d jiIndicates the distance from node j to node i; It indicates the time when node i starts to receive a data packet sent by node j to node i; It indicates the time when node j sends a data packet to node i and the data packet is received by node i; ΔT is the protection time.

[0019] As an improvement of the above method, the step of adjusting the appointment time by a random backoff mechanism includes:

[0020] Calculate the sending time after random backoff: T sendRTR_1 =T sendRTR +T control rand, where the random number rand∈[0,1] is used to calculate whether there will be a conflict when sending at this time. If there is still a conflict, the sending time after backoff is recalculated until there is no more interference. In this process, the backoff waiting time t waiting (i) Updated to:

[0021] As an improvement of the above method, step 3 comprises:

[0022] Evaluate whether the communication pair's access to the network will cause interference to the communication pair already in the network: The transmitting node determines whether the time periods of the two communication pairs occupying the channel overlap by parsing the communication pair in communication, the start time of occupying the channel, and the power used in the RTR packet, and determines whether the communication pair that accesses later will cover the effective signal power of the communication pair that accessed earlier;

[0023] If both the time overlap and power coverage conditions are met, the receiving end is judged to be interfered with; taking into account the time overlap, power difference and number of pairs, the local sending time is adjusted to ensure that the local signal and the signal of the paired communication pair arrive at the near-end receiving end synchronously to achieve parallel transmission; otherwise, the back-off state is entered until there is no interference;

[0024] If the time overlap or power coverage conditions are not met, it is considered as a communication pair without interference and can send messages directly. Before sending a message, the transmitter will send an SNT signaling packet carrying pairing information and its local sending time to inform the receiving end of the pairing status and decoding order.

[0025] As an improvement of the above method, the method comprehensively considers time overlap, power difference and number of pairs, adjusts the local signaling time, ensures that the local signal and the signal of the paired communication pair arrive at the near-end receiving end synchronously, and realizes parallel transmission, including:

[0026] Check whether the communication pair to the access network meets the serial interference cancellation decoding conditions:

[0027]

[0028] Among them, P i represents the effective signal power of the i-th communication pair; N 0 Represents noise power; P j represents the interference signal power of other communication pairs; Q represents the signal-to-noise ratio threshold of the receiving end; k represents the number of communication pairs;

[0029] If the serial interference elimination decoding condition is met, then continue to determine whether the number of paired pairs is less than the set maximum number of parallel paired pairs; otherwise, enter the backoff state until there is no interference;

[0030] If the number of paired pairs is less than the set maximum number of parallel pairings, the pairing is successful, and the sending time of the local communication pair is adjusted so that the local signal and the signal of the paired communication pair can reach the near-end receiving end of the pairing group at the same time, and an SNT packet carrying the pairing information and the adjusted sending time is sent to the successfully matched communication pair; otherwise, the backoff state is entered until there is no interference.

[0031] As an improvement of the above method, it also includes:

[0032] Each node periodically clears the channel and dynamically updates the node information through broadcasting, re-stores the topology of the entire network, and constructs the transmission power matrix required for random pairing of nodes in the entire network, ensuring that the communication pairs can adjust resource allocation in time according to changes in network load.

[0033] Compared with the prior art, the advantages of this application are:

[0034] 1. The present invention provides an underwater acoustic distributed cooperative parallel transmission MAC protocol UPNC-MAC that combines PD-NOMA with a collision prediction mechanism, which realizes dynamic perception of channel busy status and resource scheduling in a distributed underwater acoustic communication network, thereby improving the adaptability and flexibility of the network;

[0035] 2. By combining the dynamic interference assessment and communication pair matching mechanism at the receiving end, the UPNC-MAC protocol ensures that multiple communication pairs can achieve efficient parallel transmission under interference-free conditions, effectively improving the channel time utilization and system throughput;

[0036] 3. The protocol designs a reservation and scheduling mechanism based on signaling, which reduces the backoff time and control packet overhead caused by channel competition, thereby significantly reducing end-to-end delay and optimizing network performance;

[0037] 4. Combined with serial interference cancellation (SIC) technology to eliminate interference of effective signals, interference-free transmission of multiple communication pairs is achieved in the dynamically changing underwater acoustic network, enhancing the system's adaptability to complex channel conditions and multi-user concurrent communication needs.

[0038] 5. Dynamic reservation and power allocation strategies are integrated into the protocol to adjust the pairing conditions of communication pairs in real time according to task requirements, meeting the communication efficiency requirements in different mission scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The figure shows the information transmission flow chart of the underwater acoustic distributed cooperative parallel transmission method combining PD-NOMA and collision prediction mechanism;

[0040] Figure 2 Shown is a diagram of the structure of an underwater acoustic distributed communication network;

[0041] Figure 3 The protocol timing diagram is shown;

[0042] Figure 4 Shown is the frame structure diagram of the RTR protocol;

[0043] Figure 5 Shown is a flow chart of the RTR-initiated reservation time adjustment mechanism;

[0044] Figure 6 Shown is a flowchart of interference assessment at the receiving end;

[0045] Figure 7 Shown is a flow chart of the pairing algorithm;

[0046] Figure 8 It is a schematic diagram showing the simulation comparison results of the normalized throughput of the transmission method proposed in the present invention, the Slotted FAMA protocol and the RIPT protocol under different numbers of nodes;

[0047] Fig. 9 It is a schematic diagram showing the simulation comparison results of the end-to-end delay of the transmission method proposed in the present invention, the Slotted FAMA protocol and the RIPT protocol under different numbers of nodes;

[0048] Fig.10 It is a schematic diagram showing the simulation comparison results of the protocol overhead of the transmission method proposed in the present invention, the Slotted FAMA protocol and the RIPT protocol under different numbers of nodes. DETAILED DESCRIPTION

[0049] The technical solution of the present application is described in detail below with reference to the accompanying drawings.

[0050] The present invention proposes an underwater acoustic distributed collaborative parallel transmission method that combines PD-NOMA (Power Domain NOMA) with a collision prediction mechanism. Through dynamic resource allocation and channel state perception, the task requirements and underwater acoustic channel characteristics are fully combined to achieve efficient scheduling and parallel transmission of communication pairs. The present invention can optimize network performance indicators, such as significantly improving throughput, reducing end-to-end latency, and improving channel resource utilization. At the same time, the transmission method dynamically adapts to complex and changeable underwater acoustic environments by combining prediction and scheduling, and is suitable for a variety of network scenarios.

[0051] like Figure 1 As shown, the underwater acoustic distributed cooperative parallel transmission method combining PD-NOMA and collision prediction mechanism provided by the present application includes:

[0052] 1. Network initialization and maintenance:

[0053] 1.1 During the network initialization phase, each node obtains the identity and location information of surrounding nodes through broadcasting to establish the initial topology. The broadcast information includes: node ID and location information, which are used for resource allocation for subsequent communication pairs.

[0054] 1.2 According to the topology of the entire network and the receiving threshold (SNR), the transmission power matrix required for random pairing of nodes in the entire network is constructed according to the following formula, which provides a basis for subsequent channel resource allocation.

[0055]

[0056] Among them, SNR 0 is the receiving signal-to-noise ratio threshold, B 3dB (R) corresponds to the optimal frequency f 0 is the 3dB bandwidth, N(f) is the power spectrum density of the ambient noise, A(R,f) is the acoustic attenuation model, and R is the transmission distance.

[0057] 1.3 During network maintenance, by regularly clearing the channel and rebroadcasting the management package, the node information is dynamically updated and the topology status is adjusted to ensure that the communication pair can adjust resource allocation in time according to changes in network load.

[0058] 2. The receiving end initiates a transmission request (RTR) reservation:

[0059] 2.1 In each round of reservation, the communication pair dynamically generates RTR packets according to task requirements, broadcasts the ID, location information and transmission plan of the communication pair, and each node listens to and parses the RTR packets to obtain the ID and location information of the communication pair, the reservation initiation time and the length of the transmission DATA packet.

[0060] 2.2 Ensure that the RTR reservation process does not affect other nodes' monitoring of the signaling or data packets being transmitted; if there is a risk of interference, the random backoff mechanism is triggered to adjust the reservation time until no interference occurs.

[0061] 3. Interference assessment and pairing judgment SNT: The transmitter conducts interference assessment on the receiver based on the network status extracted from the previous RTR packet, and determines whether there is an interference risk by analyzing the time overlap and power coverage of the channel occupancy; if there is no interference, the signal is sent as planned; if there is interference, the communication pairing algorithm is used to adjust the sending time or enter the backoff state to ensure signal synchronization and parallel transmission, and at the same time send an SNT signaling packet to inform the pairing and decoding information.

[0062] After receiving the RTR packet sent to the local area, the transmitter first determines whether there is a need to send a signal. If so, it will conduct a receiver interference assessment based on the previously monitored network status, and select an appropriate signaling strategy based on the assessment results and the communication pair matching algorithm.

[0063] 3.1 Schematic diagram of interference assessment at the receiving end Figure 3 In this process, the transmitting node calculates whether the time periods of the two communication pairs occupying the channel overlap, the receiving power ratio of different communication pairs, and whether the communication pair accessing later will cover the effective signal power of the communication pair accessing earlier, resulting in decoding failure, by parsing the information such as the communication pair in communication, the start time of occupying the channel, and the power used in the RTR packet.

[0064] 3.2 Communication pair matching algorithm Figure 7 As shown. For the communication pairs with interference risks in 3.1, it is necessary to monitor the network status and the dynamic interference assessment of the receiving end in real time, comprehensively consider the time overlap, power difference and number of pairings, and adjust the sending time of the communication pair: if there is no interference, send DATA directly and send the message according to the original planned time; if there is interference, further check whether the pairing conditions are met. If so, adjust the local sending time to ensure that the local signal and the signal of the paired communication pair arrive at the near-end receiving end synchronously to achieve parallel transmission; otherwise, enter the backoff state until there is no interference. After successful pairing, the transmitter will send an SNT signaling packet carrying pairing information and its local sending time before sending a message to inform the interfering receiving end of the pairing status and the order of SIC decoding.

[0065] 4. Send DATA: After sending the SNT packet, the paired communication pair sends the DATA data packet at the specified time, and the non-paired non-interference communication pair directly sends the local data. If the pairing is not successful, the local transmitter directly enters the backoff stage until the end of this round of communication and then enters the SNT stage to retry pairing. Through the above signaling strategy, the UPNC-MAC protocol effectively reduces the risk of conflicts in transmission while ensuring transmission efficiency.

[0066] 5. The receiving end replies ACK: After receiving the DATA packet, the receiving end decodes it with SIC according to the decoding order in the SNT packet, extracts the valid signal, and then sends an ACK reply packet without affecting other communication pairs occupying the channel to ensure the integrity of data transmission and synchronize the transmission status, so as to prepare for the next round of communication.

[0067] The model used in this embodiment is as follows Figure 2 As shown. This network model does not rely on the central node to allocate and schedule channel resources, and has the ability to perceive the network status and make autonomous decisions in order to dynamically access the network without collision. Assume that each node is randomly distributed in a three-dimensional underwater network with a three-dimensional coverage area of ​​3000m×3000m×300m. Each node dynamically acts as a transmitter or receiver according to task requirements and interacts with other nodes. The simulation parameter settings are shown in Table 1:

[0068] Table 1 Simulation parameter settings

[0069]

[0070] Initialize the network and maintain it: During the network initialization phase, each node will broadcast a management package carrying local location and identity information to ensure that all nodes can store the node identity and location information of the entire network. Subsequently, the transmission power matrix required for random pairing of nodes in the entire network is constructed based on the node positions and receiving thresholds of the entire network.

[0071] During network maintenance, the system periodically clears the channel and rebroadcasts the management package to dynamically update the node information of the entire network. After initialization, each node can reserve the channel normally and start communication and data transmission. The data transmission stage is as follows: Figure 3 shown.

[0072] RTR reservation: The receiving end of the communication pair dynamically generates RTR packets according to task requirements before communication. The frame structure is as follows: Figure 4 Before initiating an RTR reservation, ensure that it does not affect other nodes' monitoring of the RTR, SNT, DATA, and ACK packets being transmitted. If there is an impact, the random backoff mechanism is triggered and the reservation is adjusted to avoid interference. The specific adjustment process is as follows Figure 5 shown.

[0073] Assume that the scheduled time for the local receiver to initiate the RTR control packet is T sendRTR , the time to reach the node numbered i is: Accept the end time Among them, d i is the distance from the local receiver to the i-node, T control To control the transmission time of the packet.

[0074] The RTR, SNT, DATA, ACK and other packets monitored by other nodes contain the pairing status of the corresponding communication pair and the time schedule of data transmission. Assume that the time when node i receives a data packet from node j is: The time of acceptance is in, It indicates the time when node j sends a data packet to node i and node i starts to receive the data packet.

[0075] In order to avoid conflict, it is necessary to meet Right now Otherwise, the random backoff mechanism will be triggered, and the sending time after the random backoff will be calculated: T sendRTR_1 =T sendRTR +T control ·rand, where the random number rand∈[0,1] is used to calculate whether there will be a conflict when sending at this time. If there is still a conflict, the sending time after backoff is recalculated until there is no interference. In this process, the backoff waiting time t waiting (i) Updated to:

[0076] It should be noted that each communication pair can only be in one state at the same time. For example, a communication pair that has entered the sending state will no longer initiate a new RTR reservation to avoid state conflicts. The above mechanism can reduce the probability of the local receiving end initiating a reservation to interfere with the monitoring of other nodes, thereby ensuring subsequent data transmission.

[0077] Interference assessment and pairing judgment SNT: After receiving the RTR packet to the local, the transmitter first determines whether there is a need to send a signal. If so, it will conduct interference assessment on the receiving end in combination with the previously monitored network status, and select the appropriate signaling strategy based on the assessment results and the communication pairing algorithm.

[0078] The interference assessment process at the receiving end in this embodiment is as follows Figure 6 As shown. When the channel is occupied by more than two communication pairs at the same time, whether collision interference will occur depends on two conditions: communication time overlap; the local valid signal of the receiving end is covered by the interference signal power of other communication pairs. If both the time overlap and power coverage conditions are met, the receiving end is subject to non-negligible interference. The following is an explanation of the specific principle.

[0079] The communication pairs for this round of reservation are #ID1→#ID2 (near end) and #ID3→#ID4 (far end). The receiving ends #ID2 and #ID4 initiate channel reservations to the transmitting ends #ID1 and #ID3 respectively, and all nodes in the network receive the corresponding information. During this process, the transmitting nodes #ID1 and #ID3 know the following information:

[0080] 1) Communication pairs are formed: #ID1→#ID2, #ID3→#ID4;

[0081] 2) The time of each communication pair reservation channel: T sendRTR2 , T sendRTR4 ;

[0082] 3) Length of data packet to be sent: T data1 , T data3 ;

[0083] 4) Node distance matrix: where d ij represents the distance between nodes #IDi and #IDj;

[0084] 5) Transmitting power: #ID1 transmitting power P1, #ID4 transmitting power P2.

[0085] Based on the above information, first determine whether the time periods of the two communication pairs occupying the channel overlap:

[0086] max(T recvdata,12 ,T recvdata,34 )<min(T recvdata,12 +T data1 ,T recvdata,32 +T data3 )+ΔT

[0087] Among them, ΔT is the protection time, The time when #ID2 starts receiving a valid signal. is the start time of receiving the interference signal of #ID4. If the above formula is satisfied, it means that at the receiving end of the near-end communication pair, the reception time of the interference signal and the local valid signal overlaps. On this basis, each communication pair can parse other RTR packets to determine the arrival time period of the interference signal.

[0088] Secondly, power coverage means that the power of the interference signal at the receiving end is greater than the power of the effective signal. If the strength of the interference signal is lower than the effective signal, the effective signal can still be resolved even if there is time overlap as long as the signal-to-noise ratio meets the receiving threshold. To simplify the calculation, the communication ranges of each transmitting node can be compared to see if they overlap. The communication range refers to the maximum distance at which the transmitted signal decays to the receiving threshold.

[0089] The pairing algorithm process in this embodiment is as follows Figure 7 As shown. The algorithm is based on monitoring the network status and dynamic interference evaluation of the receiving end, and comprehensively considers factors such as time overlap, power difference and number of pairs to achieve reasonable scheduling and resource utilization of local communication pairs. The specific steps are as follows:

[0090] Step S1: input communication pair information;

[0091] ■ Implementation content: The system first inputs a list of paired communication pairs and scheduled communication pairs, and sets an upper limit value "M" for the number of pairings.

[0092] ■Purpose: To ensure that the algorithm has complete input conditions when running, while avoiding overloading of network resources.

[0093] ■Paired communication pairs: Communication pairs that have been successfully paired in the current network.

[0094] ■Scheduled communication pairs: communication pairs planned to be paired in this round.

[0095] ■M: The maximum number of parallel communication pairs allowed, which is a hard constraint on system capabilities.

[0096] Step S2: monitoring network communication status;

[0097] ■ Implementation content: The system monitors the communication status of the current network in real time, including existing communication pairs, interference signals, transmission power levels, etc.

[0098] ■Purpose: To determine whether the current network environment is suitable for the access of new communication pairs, to avoid communication failures due to network load or interference.

[0099] Step S3: Setting the maximum number of parallel communication pairs;

[0100] ■ Execution content: The system sets the maximum number of parallel communication pairs to 3, that is, "M=3".

[0101] ■Purpose: This parameter is used to limit the number of communication pairs allowed at the same time to ensure that system resources are not overloaded.

[0102] Step S4: traverse the communication pair list;

[0103] ■Execution content: According to the input communication pair list, the communication pairs "Ci" are extracted one by one for inspection.

[0104] ■Variable explanation: Ci is the currently paired or scheduled communication pair.

[0105] Step S5: Check the interference of the local communication pair to the receiving end of all Ci in the network after access, that is, whether

[0106] There is time overlap and power coverage;

[0107] ■Yes (interference exists): go to step S6 to further evaluate whether the interference elimination condition is met.

[0108] ■No (no interference): Directly enter the DATA phase and send the DATA data packet according to the original planned time.

[0109] Step S6: SIC decoding condition check;

[0110] ■Execution content: Check whether the SIC (Successive Interference Cancellation) decoding conditions are met at the communication pair "Ci":

[0111]

[0112] Among them, P i is the effective signal power of the i-th communication pair, N 0 is the noise power, P j is the interference signal power of other communication pairs, Q is the signal-to-noise ratio threshold at the receiving end, and k represents the number of communication pairs. This power difference is the key to SIC's ability to accurately eliminate interference and reconstruct effective signals.

[0113] ■Yes (conditions met): Continue to step S7.

[0114] ■No (conditions not met): Mark as "need to avoid", enter the avoidance process, and wait for the next pairing opportunity.

[0115] Step S7: Verify the pairing quantity limit;

[0116] ■Execution content: The system checks whether the number of paired pairs in the communication pair list is less than the maximum number of parallel pairings "M".

[0117] ■Yes (less than M): Go to step 8 and adjust the sending time.

[0118] ■No (greater than or equal to M): Mark as "need to avoid" and exit the configuration process of the current communication pair.

[0119] Step S8: Adjust the local sending time;

[0120] ■ Implementation content: Adjust the transmission time of the local communication pair so that its local signal can reach the near-end receiving end of the paired group at the same time as the signal of the paired communication pair.

[0121] ■ Adjustment strategy: Calculate the adjustment range of the sending time based on the dynamic feedback from the receiving end; use the synchronization mechanism to ensure that the timing of signals from different communication pairs arriving at the near-end receiving end is consistent.

[0122] Step S9: output the pairing result;

[0123] ■Execution content: The system outputs the results of this round of pairing and sends pairing information and adjusted sending time to the successfully matched communication pairs.

[0124] ■ Output content:

[0125] Pairing result: includes the paired communication pair, the transmitter and the receiver identification.

[0126] Pairing signaling (SNT packet): informs the receiving end of the pairing success, SIC decoding order and the locally adjusted sending time.

[0127] ■Function: Ensure that all communicating parties involved in pairing can correctly understand and execute the pairing plan.

[0128] Step S10: end;

[0129] ■Execution content: When all communication pairs are processed, the system exits the pairing process and enters the state of preparing to send DATA.

[0130] ■Note: The communication pairs that failed to pair will continue to try in the next round of pairing.

[0131] Send DATA: After sending the SNT packet, the paired communication pair sends the DATA data packet at the specified time, and the non-paired non-interference communication pair directly sends the local data. If the pairing is not successful, the local transmitter directly enters the backoff until the end of this round of communication and then enters the interference assessment and pairing judgment SNT to retry pairing. Through the above signaling strategy, the UPNC-MAC protocol effectively reduces the risk of conflicts in transmission while ensuring transmission efficiency.

[0132] After receiving the DATA packet, the receiver extracts the valid signal according to the decoding order of the SNT packet, and sends an ACK reply packet without affecting other communication pairs occupying the channel to ensure the integrity of data transmission and synchronize the transmission status to prepare for the next round of communication.

[0133] Figure 8 It is a schematic diagram of the simulation comparison results of the normalized throughput of the transmission method proposed in the present invention and the SlottedFAMA protocol and the RIPT protocol under different numbers of nodes. It can be seen from the simulation results that the normalized throughput of the transmission method provided by the present invention is significantly better than that of the other two protocols.

[0134] Fig. 9 It is a schematic diagram of the simulation comparison results of the end-to-end delay of the transmission method proposed in the present invention and the SlottedFAMA protocol and the RIPT protocol under different numbers of nodes in the embodiment. From the simulation results, it can be seen that the transmission method provided by the present invention has significantly better end-to-end delay than the other two protocols under low load conditions and medium and low packet length conditions.

[0135] Fig.10It is a schematic diagram of simulation comparison results of the transmission method proposed in the present invention and the overhead of the SlottedFAMA protocol and the RIPT protocol under different numbers of nodes. It can be seen from the simulation results that the overhead of the transmission method provided by the present invention is in the middle of the two protocols.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application is described in detail with reference to the embodiments, a person skilled in the art should understand that any modification or equivalent replacement of the technical solution of the present application does not depart from the spirit and scope of the technical solution of the present application and should be included in the scope of the claims of the present application.

Claims

1. A PD-NOMA-based underwater acoustic distributed cooperative parallel transmission method, comprising: Step 1: Each node obtains the ID and location information of surrounding nodes through broadcasting, stores the topology of the entire network, and constructs the transmission power matrix required for random pairing of nodes in the entire network; Step 2: In each round of reservation, the receiver dynamically generates an RTR packet carrying the ID, location information, and transmission plan information of the communication pair according to the task requirements, and sends it without affecting the communication of other communication pairs. If there is an interference risk, the random backoff mechanism is used to adjust the reservation time until there is no interference; Step 3: After receiving the RTR packet sent to the local area, the transmitter first determines whether there is a need to send a message; if so, the receiver performs interference assessment based on the network status extracted from the previously monitored RTR packet, and determines whether there is an interference risk by analyzing the time overlap and power coverage of the channel occupancy; if there is no interference, send the message as planned; if there is interference, adjust the sending time or enter the backoff state through the communication pairing algorithm to ensure signal synchronization and achieve parallel transmission, and send the SNT signaling packet to inform the receiver of the pairing and decoding information; Step 4: After the transmitter sends the SNT signaling packet, the paired communication pair sends the DATA data packet at the specified time, and the non-paired non-interference communication pair directly sends the DATA data packet; if the pairing is not successful, the transmitter enters the backoff until the end of this round of communication and then enters step 3 to retry pairing; Step 5: After receiving the DATA packet, the receiver decodes it according to the decoding order in the SNT signaling packet, extracts the valid signal, and sends an ACK reply packet without affecting other communication pairs occupying the channel.

2. The underwater acoustic distributed cooperative parallel transmission method based on PD-NOMA according to claim 1 is characterized in that: The transmit power matrix construction formula is: Where P(R) is the transmit power; SNR0 is the receive signal-to-noise ratio threshold; B 3dB (R) is the 3dB bandwidth corresponding to the optimal frequency; N(f) is the power spectrum density of the ambient noise; A(R,f) is the acoustic attenuation model; R is the transmission distance.

3. The underwater acoustic distributed cooperative parallel transmission method based on PD-NOMA according to claim 1 is characterized in that: The method for determining whether there is interference risk is as follows: There is a risk of interference when the following formula is not satisfied: in, represents the time when the RTR packet arrives at the node numbered i; T sendRTR Indicates the scheduled time when the receiving end initiates the RTR packet; d i represents the distance from the receiving end to the i-node; c represents the data packet transmission speed; Indicates the time when the receiving end finishes receiving the RTR packet, T control Indicates the transmission time of the RTR packet; Indicates the time when node i receives a data packet from node j; d ji Indicates the distance from node j to node i; It indicates the time when node i starts to receive a data packet sent by node j to node i; It indicates the time when node j sends a data packet to node i and the data packet is received by node i; ΔT is the protection time.

4. The underwater acoustic distributed cooperative parallel transmission method based on PD-NOMA according to claim 3 is characterized in that: The step of adjusting the appointment time by a random backoff mechanism includes: Calculate the sending time after random backoff: T sendRTR_1 =T sendRTR +T control rand, where the random number rand∈[0,1] is used to calculate whether there will be a conflict when sending at this time. If there is still a conflict, the sending time after backoff is recalculated until there is no more interference. In this process, the backoff waiting time t waiting (i) Updated to:

5. The underwater acoustic distributed cooperative parallel transmission method based on PD-NOMA according to claim 1 is characterized in that: The step 3 comprises: Evaluate whether the communication pair's access to the network will cause interference to the communication pair already in the network: The transmitting node determines whether the time periods of the two communication pairs occupying the channel overlap by parsing the communication pair in communication, the start time of occupying the channel, and the power used in the RTR packet, and determines whether the communication pair that accesses later will cover the effective signal power of the communication pair that accessed earlier; If both the time overlap and power coverage conditions are met, the receiving end is judged to be interfered with; taking into account the time overlap, power difference and number of pairs, the local sending time is adjusted to ensure that the local signal and the signal of the paired communication pair arrive at the near-end receiving end synchronously to achieve parallel transmission; otherwise, the back-off state is entered until there is no interference; If the time overlap or power coverage conditions are not met, it is considered as a communication pair without interference and can send messages directly. Before sending a message, the transmitter will send an SNT signaling packet carrying pairing information and its local sending time to inform the receiving end of the pairing status and decoding order.

6. The underwater acoustic distributed cooperative parallel transmission method based on PD-NOMA according to claim 5 is characterized in that: The method comprehensively considers time overlap, power difference and the number of pairs, adjusts the local signal transmission time, ensures that the local signal and the signal of the paired communication pair arrive at the near-end receiving end synchronously, and realizes parallel transmission, including: Check whether the communication pair to the access network meets the serial interference cancellation decoding conditions: Among them, P i represents the effective signal power of the i-th communication pair; N0 represents the noise power; P j represents the interference signal power of other communication pairs; Q represents the signal-to-noise ratio threshold of the receiving end; k represents the number of communication pairs; If the serial interference elimination decoding condition is met, then continue to determine whether the number of paired pairs is less than the set maximum number of parallel paired pairs; otherwise, enter the backoff state until there is no interference; If the number of paired pairs is less than the set maximum number of parallel pairings, the pairing is successful, and the sending time of the local communication pair is adjusted so that the local signal and the signal of the paired communication pair can reach the near-end receiving end of the pairing group at the same time, and an SNT signaling packet carrying the pairing information and the adjusted sending time is sent to the successfully matched communication pair; otherwise, the backoff state is entered until there is no interference.

7. The underwater acoustic distributed cooperative parallel transmission method based on PD-NOMA according to claim 1 is characterized in that: Also includes: Each node periodically clears the channel and dynamically updates the node information through broadcasting, re-stores the topology of the entire network, and constructs the transmission power matrix required for random pairing of nodes in the entire network, ensuring that the communication pairs can adjust resource allocation in time according to changes in network load.

Images