JP2008099289A - Frame collision processing method and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restore collision frames by providing a frame collision processing method and a system. <P>SOLUTION: A frame collision processing method includes: a step (a) of processing information bits using a spread sequence, and transmitting the information bits to a receiving node; a step (b) of despreading an overall signal received using the spread sequence to obtain a sequence maximum power addition value, a symbol shift and a code chip shift corresponding to each spread sequence; a step (c) of determining whether a frame collision occurs by comparing each sequence maximum power addition value with a threshold, performing the processing of a step (d) for a frame required to be restored when there are colliding frames, and performing the processing of a step (d) on each of other frames corresponding to a total maximum sequence maximum power addition value; and a step (d) of acquiring synchronization information, applying precise synchronization processing to a symbol shift value, determining a frame that can be restored, and acquiring a media access control layer load, so that NAV can be set in accordance with preset rules. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to the field of data transmission technology, and more particularly to a frame collision processing method and system.

  In a wireless communication system, when signals are transmitted simultaneously from a plurality of mobile terminals, there is a high possibility that a frame is lost due to a collision. Obviously, the loss of frames affects the data transmission of the mobile terminal.

  Therefore, a plurality of solutions are currently proposed. Hereinafter, each of these solutions will be briefly described.

  In the wireless LAN standard, two types of media access control algorithms are defined. One is a basic DCF algorithm (DCF, Distributed Coordination Function), and the other is a transmission request / transmission permission handshaking DCF (RTS / CTS Handshaking DCF) algorithm. The basic DCF algorithm is used for transmission of short data frames, and the RTS / CTS handshake DCF algorithm is used for transmission of long data frames.

  Like other media access control algorithms, the idea of the DCF algorithm is to avoid collisions. In order to reduce the probability of collision, DCF algorithm can be used, for example, physical carrier sense, network allocation vector (NAV) setting, binary exponential backoff (BEB) algorithm, and RTS / CTS hand There are multiple methods defined to avoid collisions, such as shake channel hold.

  However, the DCF algorithm also has the following problem.

  (1) The algorithm does not make full use of the potential capabilities of the physical layer, i.e. uses only physical layer carrier sense information. In fact, the physical layer can provide more information for collision avoidance, but the DCF algorithm does not fully consider this point.

  (2) Depending on the BEB algorithm used for the DCF algorithm, collision cannot be effectively avoided. For example, when there are many network nodes, even if the BEB algorithm is used, a plurality of nodes may select the same number of back-off slots, so that collision may occur.

  (3) Since there is a possibility of collision in the RTS / CTS frame itself, it is guaranteed that the data frame is transmitted without interference even by holding the RTS / CTS handshake channel defined by the DCF algorithm. Can not.

  (4) When a collision occurs, no countermeasure can be provided by the DCF algorithm, in other words, a data frame is always lost when a collision occurs.

  In view of the above problem of the DCF algorithm, a multi-packet reception technique (MPR, Multiple Packet Reception) has been proposed. According to the technology, the conventional physical layer model of “collision is equivalent to frame loss” can be changed and the performance of the wireless random access network can be greatly improved. It is. At present, the MPR technology that has attracted the most attention is a multi-packet reception technology based on a Polynomial Phase Sequence (PPS). The main idea of the PPS multi-packet reception technique is as follows. A common code book is stored for each node, and the code book includes several feature codes (color codes). When there is data to be transmitted from the node, one feature sequence is randomly selected from the common codebook and the transmitted signal is marked. When receiving, the receiving node performs an exhaustive search for all the feature sequences in the common codebook, determines the feature sequence included in the received signal, and transmits a plurality of transmissions based on the determined feature sequence. Separate the signal sent from the node.

  In the PPS multi-packet reception technique, although it is the main idea to set different feature sequences for each transmission node, it cannot be said that there is no possibility that different transmission nodes select the same feature sequence. Obviously, if different transmitting nodes select different feature sequences, the receiving node can perform signal separation of different transmitting nodes according to the signal processing method. On the other hand, when a plurality of transmitting nodes select the same feature codeword, the receiving node cannot restore all signals transmitted from these nodes based on the feature codeword.

  There are also other problems with the PPS multi-packet reception technique.

  (1) Since the receiving node determines the feature sequence included in the received signal by exhaustive search from a common code book, the calculation complexity is very high. Further, in order to reduce the probability that a plurality of nodes select the same feature codeword, the PPS multi-packet reception technique requires that the size of a common codebook is eight times the total number of nodes. When the number of nodes in the network is very large, the common codebook becomes very large, so the complexity of the receiving node becomes very high and it becomes very unacceptable.

  (2) In the PPS multi-packet reception technique, the interval between frames transmitted from the same node is required to be larger than the length of the sliding window of the receiving node. The length is usually twice the frame length. However, in the media access control layer protocol, a control frame such as CTS and positive acknowledgment (ACK) must respond quickly within a short time interval. Cannot be integrated.

  In conventional wireless random access networks, there are two cross-layer design proposals related to multi-packet reception, one is Network Assisted Diversity Multiple Access (NDMA) and the other is One is the MPR-p algorithm.

  The NDMA algorithm is a method applied to a network in which time slots are synchronized. That is, the node can transmit a frame only at the start timing of each time slot. Clearly, frame collisions occur when multiple nodes transmit frames in a time slot. In the NDMA algorithm, when a frame collision occurs, the receiving node obtains sufficient information for all the nodes that transmitted the frame until the receiving node can restore the frame in which the collision has occurred. It is notified that frames are continuously transmitted in the time slot. In addition, in order to ensure that the receiving node can identify which node's frame has collided, it is necessary to assign a unique ID to each node, and the IDs of different nodes are orthogonal to each other.

  The main drawback of the NDMA algorithm is that it applies only to networks where time slots are synchronized, not to asynchronous networks. However, most of current wireless random access networks such as wireless LAN IEEE 802.11b and IEEE 802.11a are all asynchronous networks.

  As shown in FIG. 1, when there is data to be transmitted from the transmitting node Tx to the adjacent receiving node Rx, the Tx first transmits the RTS to the Rx, and then the MPR-p algorithm operates as shown in FIG. Request Rx to send a frame. The RTS frame transmitted from the Tx is received not only by Rx but also by other neighboring nodes of Tx. Assuming that the other adjacent node is the node A, when the node A correctly receives the RTS, the node A performs a normal back-off algorithm. That is, its own network allocation vector is set so that the node cannot access the channel before the Tx and Rx data exchange ends. When the destination node Rx receives the RTS correctly, it responds with a CTS frame to the Tx, receives the request for the Tx, and indicates that the Tx data transmission start is permitted. Since the MPR-p algorithm assumes that the physical layer has multi-packet reception capability, Tx transmits data to Rx and other neighboring nodes of Rx can also transmit data frames to Rx. As shown in FIG. 1, Node B and Node C can also transmit data to Rx. Thus, Rx can receive multiple data frames. In this example, these data frames are specifically Tx, node B and node C data frames. Since the MPR-p algorithm assumes that the physical layer has multi-packet reception capability, data frames transmitted from different nodes can be separated based on the assumption. After separating these frames, Rx further transmits the augmented ACK frame to indicate that the data has been received correctly, and the augmented ACK frame includes the addresses of all nodes that transmitted the data frame to Rx. It is included. That is, in the above example, the ACK frame should include Tx and the addresses of Node B and Node C.

  The main problems existing in the MPR-p algorithm are as follows.

  (1) Request to provide more information from the network. The MPR-p algorithm requests each node to send information on the number of neighboring nodes of the node to other nodes by using the CTS frame by knowing which neighboring nodes are around it. The node calculates a transmission probability based on the adjacent node number information in the CTS frame, and determines whether to transmit a data (DATA) frame based on the probability. However, because the network changes dynamically, each node must periodically send a “probe” to obtain this information. Obviously, such processing will occupy a large amount of network resources and will greatly reduce the performance of the network.

  (2) The MPR-p algorithm requires modification of the format of the CTS frame and the ACK frame in the conventional protocol. For example, as described above, it is necessary to include the number information of adjacent nodes in the CTS frame. Also, the address information of the node needs to be included in the CTS frame. The address information of the node allows the node that has received the CTS frame to know from which node the CTS frame is transmitted, so that the DATA frame that needs to be transmitted to the node is To determine if it exists. It is necessary to put a plurality of address fields in the ACK frame, so that the receiving node can respond to a plurality of received data frames through one ACK frame.

  (3) The MPR-p algorithm uses the multi-packet reception capability of the physical layer only for data frames, and does not use the multi-packet reception capability for control frames such as CTS and ACK. Although the multi-packet reception capability for the control frame in the physical layer can be restored and used when a control packet collides, the MPR-p algorithm has no mechanism for using such capability. Therefore, if frames such as CTS and ACK collide and are lost, they cannot be restored. For example, in FIG. 1, when an ACK frame collides and is lost unfortunately, Tx, Nodes B and C think that the data frame transmitted by itself is lost because it did not receive the ACK frame. Even if the target node actually receives the data frame correctly, the data frame is retransmitted thereafter. Obviously, the retransmission process not only reoccupies the network resources, but there is still the possibility of collisions. If the multi-packet reception capability of control frames is fully developed and used, such retransmission can be avoided and network resources can be used effectively.

  In summary, there is no conventional method for solving frame restoration and related processing when a collision occurs.

  In view of the above problems, the main problem to be solved by the present invention is to provide a frame collision processing method to realize restoration for a collision frame.

  Another problem that the present invention seeks to solve is to provide a frame collision handling system.

  In order to solve the above problem, the present invention provides the following technical solution.

In the frame collision processing method according to the present invention, a spreading sequence that uniquely corresponds to each frame type is set in advance, and the method further includes that the transmitting node uses the spreading sequence to process information bits input to the node. Step a for processing to the receiving node and then transmitting to the receiving node;
The receiving node performs despreading processing on the entire received signal using the spreading sequence to obtain a sequence maximum power addition value corresponding to each spreading sequence, a corresponding symbol shift, and a corresponding code chip shift. b,
The receiving node determines whether or not a frame collision has occurred by comparing the sequence maximum power addition value corresponding to each spreading sequence with a preset threshold value. Based on the related information, a frame that needs to be restored is identified, the process of step d is performed on the frame, and if there is no collided frame, the maximum sequence maximum among all the sequence maximum power addition values A step c for setting the power addition value as a total maximum sequence maximum power addition value, identifying a frame corresponding to a spreading sequence corresponding to the sequence maximum power addition value, and performing the process of step d on the frame;
The receiving node acquires frame synchronization information, performs frame synchronization by performing fine synchronization processing on the symbol shift value of the frame, identifies a frame that can be restored, and performs detection on the frame. Obtaining a media access control layer load of the frame;
And a step e in which the receiving node sets a network allocation vector NAV using a preset rule in the media access control layer.

The frame collision processing system according to the present invention has a transmission node and a reception node, of which
The transmitting node performs processing on the information bits input to the present node using a preset spreading sequence, transmits the processed information bits to the receiving node,
The receiving node performs a despreading process on the entire received signal using a preset spreading sequence, and obtains a sequence maximum power addition value corresponding to each spreading sequence, a corresponding symbol shift, and a corresponding code chip. A shift is acquired, and each sequence maximum power addition value is compared with a preset threshold value to determine whether or not a frame collision has occurred, and when there is a collision frame, in the related information of the collision frame, If the frame that needs to be restored is identified and no frame collision occurs, the maximum sequence maximum power addition value is selected from all the sequence maximum power addition values and the total maximum sequence maximum power addition value is selected. And specify the frame corresponding to the spreading sequence corresponding to the maximum sequence power addition value. By performing fine synchronization processing on the specified frame, the frame that can be restored is specified, and by detecting the frame, the media access control layer load is obtained, and in the media access control layer, NAV is set using a preset rule.

  By simulating the physical layer design and the media access control layer design according to the present invention and comparing the simulation result with the simulation result of the prior art means, the effectiveness in the present invention can be proved. The effectiveness may be proved from the effects in the physical layer and the media access control layer of the receiving node, respectively.

  First, simulation settings are made for physical layer channels, media access control layer data load length, frame structure, spreading sequence, transmitting node, receiving node and corresponding information. The specific physical layer simulation settings are as follows: become.

Set the channel as a Rayleigh fast decay channel, i.e. the channel response remains unchanged in each frame and changes randomly in different frames,
For the basic DCF algorithm, the data load length of the media access control layer is set to 1000 bits, for the RTS / CTS handshake DCF algorithm, the data load length is set to 8000 bits,
The frame structure is set based on the wireless LAN standard, that is, the preamble length is 144 bits, the physical layer frame head length is 48 bits, and the media access control layer packet head and media Access control layer data loading, and
Adopting four different polyphase complex spreading sequences based on Barker sequence as spreading sequence, the length is 11 code chips,
Two transmission nodes are set, and at each transmission timing, the two transmission nodes independently generate a frame to be transmitted, and whether or not the frames of the two transmission nodes collide is a preset probability. Determined by P, that is, P is the collision probability, (1-P) is the probability that no collision will occur,
One receiving node is set and used to execute the detection method according to the present invention.

  The simulation for the physical layer in which the perspective effect exists further includes additional settings. Specifically, the transmission power of a nearby transmission node is 30 dB higher than that of a distant transmission node, and at each transmission timing, one transmission node is selected at random with a probability of 0.5, and the other transmission node is selected. A distant transmission node is assumed.

  In addition, the transmission node according to the present invention guarantees the consistency of the bandwidth with the conventional wireless LAN standard by adopting different spreading methods for the high data rate and the low data rate. In the conventional standard, a Barker sequence of 11 code chips length is adopted and spread. For low data rates, the Barker sequence spreads over the entire frame, but for high data rates, the Barker sequence spreads only for the preamble and physical layer frame head. The present invention simply replaces the Barker sequence with four 11 code chip length sequences, and does not change the spreading scheme. Since the spreading scheme does not change and the spreading code length does not change, the entire transmitter configuration can be kept unchanged, and the bandwidth is not increased.

  Simulation is performed based on the above settings, and simulation results shown in FIGS. 7 to 14 are obtained. Hereinafter, each of these simulation results will be described.

  7 to 10 show the simulation results of the physical layer when there is no perspective effect and the data rate is 5.5 Mbps. There are a total of 16 types of collisions, but the results are similar, so some of the same types of control frame collisions, different types of control frame collisions, control frame and data frame collisions, and data frame and data frame collisions. Only the simulation results of typical collision types are shown. According to the simulation results, the processing method according to the present invention can obtain much better performance than the conventional reception method, and in particular, in the case of high SNR, the frame error rate of the system can be greatly reduced.

  11 to 12 show the simulation results of the physical layer when there is no perspective effect and the data rates are 1 Mbps, 2 Mbps, and 11 Mbps. According to the figure, the transmitter according to the present invention is effective for both low data rates (1 Mbps, 2 Mbps) and high data rates (11 Mbps), and can greatly improve the frame error rate performance of the system. .

  13 to 14 show the simulation results of the physical layer when there is a perspective effect and the data rate is 5.5 Mbps. According to the figure, the transmitter processing method according to the present invention is very effective even under the perspective effect.

  Similarly, it is necessary to first set up a simulation for the media access control layer, and specifically includes a network topology, a frame arrival distribution, a frame length, a performance metric, and the like. Specific simulation settings include:

  The network topology is set to a square grid, which has 16 nodes, each node is distributed at the grid intersections, and each node has at most 4 adjacent nodes. In addition, each node can only receive signals from adjacent nodes.

  Frame arrival distribution is set as Poisson Distribution.

  The frame length is 1000 bits similarly to the frame load length in the basic DCF algorithm, and the frame load length in the RTS / CTS handshake DCF algorithm is 8000 bits.

  The performance metrics include network throughput and transmission delay.

In the media access control layer simulation, when a collision occurs, it is necessary to restore the collided frame with a certain “restoration probability”. The “restoration probability” is obtained by physical layer simulation. First, the frame error rate of each type of collision when the collision probability is 1 in the physical layer simulation is obtained, and the frame error rate is subtracted by 1 to obtain the “restoration probability”. Tables 1 and 2 show the simulation results of the physical layer frame error rate in the case of three types of SNRs (3 dB, 7 dB, 10 dB). The “restoration probability” used in the media access control layer simulation can be calculated from Table 1 and Table 2.

  Among them, the frame error rate in Table 1 is the frame error rate when the data frame load is 1000 bits, the data transmission rate is 11 Mbps, and the collision probability is 1, and the SNR corresponding to Table 1 (a) Is 3 dB, the SNR corresponding to Table 1 (b) is 7 dB, and the SNR corresponding to Table 1 (c) is 10 dB. The frame error rate in Table 2 is the frame error rate when the data frame load is 8000 bits, the data transmission rate is 11 Mbps, and the collision probability is 1. The SNR corresponding to Table 2 (a) is 3 dB. The SNR corresponding to Table 2 (b) is 7 dB, and the SNR corresponding to Table 2 (c) is 10 dB.

  15 to 16, the basic DCF algorithm and the network throughput performance and delay performance of the algorithm according to the present invention are shown. According to FIG. 15, according to the present invention, the network throughput performance can be greatly improved. When the SNR is 3 dB, about 50% can be improved, and when the SNR is 7 dB, about 66% can be improved. According to FIG. 16, according to the present invention, the transmission delay of the network can be greatly reduced.

  17 to 18 show the RTS / CTS handshake DCF algorithm and the network throughput performance and delay performance of the algorithm according to the present invention. According to FIG. 17, according to the present invention, the network throughput performance can be greatly improved. When the SNR is 3 dB, about 35% can be improved, and when the SNR is 10 dB, about 41% can be improved. According to FIG. 18, according to the present invention, the transmission delay of the network can be greatly reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the frame collision processing method and system can be provided and the restoration | repair with respect to a collision frame is realizable.

  Hereinafter, the present invention will be described in detail based on the drawings and specific embodiments.

  As can be seen from the analysis for the PPS multi-packet reception algorithm, the main origin of its complexity is that each node spreads using a different spreading sequence than the other nodes, and the receiving node Is to separate them. Obviously, if the number of nodes in the network is very large, there will be a correspondingly large number of spreading sequences, and the receiving node will need to search all possible spreading sequences, increasing complexity. It will be.

  In fact, while the number of nodes in the network is large, there are only a limited number of types of frame types. For example, in the case of the wireless LAN standard IEEE 802.11, there are only four types of frames: RTS, CTS, DATA, and ACK. Therefore, since a unique spreading sequence is assigned to each node, instead of giving a unique spreading sequence to each frame type, the receiving node only has to search all four spreading sequences in total. The complexity of the receiving node can be greatly reduced.

  Therefore, the main idea of the present invention is as follows. A corresponding spreading sequence is set for each frame type, and the transmitting node spreads the frame using the spreading sequence in the physical layer. The receiving node performs the following processing after receiving the signal. In the physical layer, the receiving node performs a despreading process on the received signal based on the spreading sequence, determines whether or not a frame collision has occurred based on the result of the despreading process, and the collision occurs. Based on the frame type and / or the arrival time of the frame, the frame that needs to be restored is identified and the frame restoration process is performed. In the media access control layer, the different collision types are determined based on the preset rules. Perform different NAV settings for.

  In order to simplify the description, the wireless LAN standard IEEE802.11b will be described in detail below as an example. The wireless LAN standard IEEE802.11b includes four types of frame structures: RTS frame, CTS frame, DATA frame, and ACK frame. Since it is necessary to set a spreading sequence corresponding to each frame type, a total of four spreading sequences are required. Each spreading sequence may be set to a code chip having a length of 11. In addition, it is necessary to define the restoration process and NAV setting method in each case.

  Based on the above settings, the transmitting node according to the present invention first uses these spreading sequences to perform spreading processing on the frames transmitted to the receiving node, and uses the transmission antennas for the frames after spreading processing. To the receiving node.

  After receiving the signal, the receiving node first performs processing similar to RAKE reception using these four spreading sequences, and can determine whether or not a frame collision has occurred through the processing. If no collision occurs, the receiving node performs conventional processing. For example, processing such as signal detection and demodulation / decoding is performed, and the media access control layer load obtained by the processing is transmitted to the media access control layer of this node. Thereafter, the media access control layer of the receiving node needs to further set the NAV. When the NAV value of the received load is larger than its own NAV value, the NAV value of the received load is updated. When it is smaller than its own NAV value, it maintains its own NAV value.

  When a collision occurs, the receiving node first determines whether to perform frame restoration processing and which frame to restore based on the related information of the collided frame in the physical layer, and after restoring the frame, The load of the media access control layer is separated and transmitted to the media access control layer of this node together with the related information of the previously specified frame. Thereafter, the media access control layer of the receiving node further performs a corresponding NAV setting based on the related information of the frame transmitted from the physical layer and the load obtained by restoration.

  Hereinafter, specific processing of the transmission node and the reception node will be described in detail.

  The processing of the transmission node is specifically divided into two types: a high data rate (5.5 Mbps and 11 Mbps) and a low data rate (1 Mbps and 2 Mbps). The configuration of the transmission node is shown in FIGS. 2 (a) and 2 (b), respectively.

  As shown in FIG. 2 (a), the operation flow of the low data rate transmission node is to modulate information bits input to the transmission node, including a preamble, a physical layer frame head, and a media access control layer load; Then, spreading the corresponding frame using the spreading sequence, and transmitting the spread frame to the receiving node via the transmitting antenna. Among them, the diffusion process can be known from FIG.

  As shown in FIG. 2 (b), the operation flow of the high data rate transmission node is to group the input information bits, group the preamble and physical layer frame head into one group, and load the media access control layer. The step of making one group, and then modulating the preceding one group, spreading the corresponding frame using the spreading sequence, and complementary code keying (CCK: complementary code keying) for the following one group ) Step of performing spread modulation (the two processes can be known from FIG. 3 (b)), and finally, the two groups of data after the spread process are multiplexed and transmitted to the reception side via the transmission antenna Including the step of.

  The use of different transmission node configurations for low and high data rates is to maintain better compatibility with wireless LAN standards. According to FIG. 1, the transmission node according to the present invention maintains almost the same configuration as the conventional transmission node without increasing the bandwidth. The difference from the conventional transmission node is that only the number of spreading sequences is changed, that is, one spreading sequence is changed to four spreading sequences.

  In order not to lose generality, it is assumed that RTS adopts spreading sequence SC1, CTS uses spreading sequence SC2, DATA uses spreading sequence SC3, and ACK uses spreading sequence SC4.

  Hereinafter, the receiving node according to the present invention shown in FIG. When the receiving node performs frame restoration in the physical layer, first, synchronization and channel estimation are performed on data, and then processing such as detection, demodulation and decoding is performed based on the synchronization information.

  The conventional synchronization processing of the receiving node is as follows. The spread signal is used to despread the received signal, then the spread sequence is shifted by one code chip, and the received sequence is further despread, and when the relevant peak appears, the shift is recorded and the above operation is continued. . If a second related peak appears at a location 11 code chips away, the shift at this time is recorded and the above operation is continued. If a third related peak appears at a location 22 code chips away from the first record, it is considered synchronized. And after the synchronization process is complete, the receiver proceeds to a subsequent detection process.

  According to the conventional synchronization process of the receiving node, it is applied only to frame synchronization when there is no collision. If a collision occurs, at most only one frame can be synchronized, and all the collided frames cannot be synchronized.

  In order to overcome the shortcomings in the conventional receiving node synchronization process, the present invention provides an improved frame synchronization algorithm. Specifically, there are three types of code chip synchronization, symbol synchronization, and frame type synchronization. In order to simplify the description, the case of a single path channel and a long PLCP will be described as an example.

  This process corresponds to the next step as shown in FIG.

  In step A, despreading processing is performed on the entire received signal using these four spreading sequences.

  Performing the despreading process using SC1, SC2, SC3 and SC4 may be performed by serial processing, that is, SC1, SC2, SC3 and SC4 in order, or parallel processing, that is, SC1, SC2, SC3 and SC4 may be processed simultaneously. However, the despreading process of each spreading sequence is the same. Therefore, the despreading process will be described by taking the first spreading sequence, that is, SC1 as an example. Specific processing includes the following.

  In step a, using SC1, the entire received signal is despread to obtain the first sequence, the code chip of SC1 is cyclically shifted by the first position, and the received signal is despread to obtain the second sequence. The first sequence is acquired, and then the cyclic shift and the despreading process are repeated nine times to acquire a total of 11 sequences, and each sequence has a corresponding code chip shift.

  In step b, slide power addition is performed on each of the acquired 11 sequences using a slide window having a length of 192. That is, first, a power addition value from the first symbol to the 192nd symbol is obtained. Then, the window is moved by one symbol, and then the power addition value from the second symbol to the 193rd symbol is obtained, the window is further moved, and the remaining symbols are processed in the same manner. Of these, 192 is the sum of the length of the preamble and the physical layer frame head. By comparing all the power addition values obtained for the sequence, the maximum power addition value and the corresponding symbol shift can be obtained, and the maximum power addition value is called a sequence maximum power addition value. Each of the 11 sequences obtained in step a can obtain a sequence maximum power addition value and a corresponding symbol shift through step b, so that a total of 11 sequence maximum power addition values and corresponding symbols can be obtained. Shifts can be obtained, and one code chip shift corresponds to each sequence.

  In step c, the 11 sequence maximum power addition values obtained in step b are compared, and if necessary, the corresponding sequence maximum power addition values, the corresponding symbol shifts and the corresponding code chip shifts are recorded and obtained. All three values correspond to the spreading sequence SC1.

  If the frame collision type that needs to be detected is not identified, i.e., it is necessary to detect the collision of any of a plurality of frames, in step c, the 11 sequence maximum power addition values and the corresponding symbol shifts And the code chip shift must be recorded. All the sequence maximum power addition values and the corresponding information are recorded because there is a possibility that a plurality of frames of the same type collide with each other.

  If only a few frame collisions need to be detected, only a corresponding number of sequence maximum power sums and corresponding information may be recorded in step c. For example, if only a collision between two frames needs to be detected, only the maximum sequence maximum power addition value and the second largest sequence maximum power addition value and corresponding information may be recorded in step c. Similarly, if only three frame collisions need to be detected, only the previous three sequence maximum power sums and corresponding information may be recorded in step c.

  In step B, it is determined whether or not there is a collided frame by comparing the sequence maximum power addition value corresponding to the spreading sequences SC1, SC2, SC3, and SC4 with a preset threshold value. If there is a collided frame, the frame that needs to be restored is determined based on the related information of the colliding frame, and then the process of step C is performed. If there is no collided frame, the processing of step C is performed on the frame corresponding to the spreading sequence corresponding to the maximum sequence maximum power addition value among all the sequence maximum power addition values, and the maximum sequence maximum power The added value is called the total maximum sequence maximum power added value.

  In this step, the process of determining whether or not there is a collided frame by comparing these sequence maximum power addition values with a preset threshold value is specifically the sequence maximum power addition value and a preset threshold value. If two or more sequence maximum power addition values are greater than the threshold, it is determined that a frame collision has occurred, and the type of the collided frame is determined by these sequence maximum power addition values greater than the threshold. it can. Specifically, the type of the collided frame is the type of the frame corresponding to the spreading sequence to which these sequence maximum power addition values correspond.

  Among them, since the setting of the threshold affects the system performance and the calculation complexity at the same time, when setting the threshold in advance, it is necessary to comprehensively consider it according to the actual situation and set it appropriately. If the threshold value is relatively small, the probability that frame determination will be lost decreases, and the system has relatively good performance, but the calculation complexity of the system increases. When the threshold is too large, the calculation complexity of the system is reduced, but the probability that the frame determination is missed is increased, and the system performance is also reduced. Actually, it is necessary to set according to the calculation complexity allowed by the system and the required performance. For example, if the system performance is the first target, a relatively small threshold value is selected, and a high performance is replaced instead of a large calculation complexity. In the opposite case, a relatively large threshold is selected.

  By the above process, it is possible to determine a collision between a plurality of arbitrary frames. Since there are fewer collisions of more than three frames in an actual system, a detailed description is given here of two frame collisions and three frame collisions.

  In the case of a collision of two frames, the maximum sequence maximum power addition value and finally the second largest sequence maximum power addition value are finally obtained by comparing all the sequence maximum power addition values, and finally It is determined whether the second largest sequence maximum power addition value is larger than a preset threshold value. When it is larger, it is determined that a collision between two frames has occurred. In other cases, it is determined that there is no frame collision.

  In the case of a collision of three frames, by comparing all sequence maximum power addition values, finally the maximum sequence maximum power addition value, finally the second largest sequence maximum power addition value, and finally the third A large sequence maximum power addition value is obtained, and finally it is determined whether or not the second largest sequence maximum power addition value and finally the third largest sequence maximum power addition value are larger than the threshold value. If only the 3rd largest sequence maximum power addition value is greater than the threshold, it is determined that a collision between two frames has occurred. Finally, if the 3rd largest sequence maximum power addition value is greater than the threshold, there is a collision between 3 frames. Judgment has occurred and finally the second largest sequence maximum power addition value and finally the third largest sequence When large power addition value is equal to or less than the threshold together, it is determined that there is no frame collision.

  Obviously, from the above description of two frames and three frames, it is possible to directly infer the processing when four or more frames collide. Here, for the processing of collision of more than three frames, No detailed explanation.

  Further, according to the above description, the frames determined to have collided may be the same type of frame or may be different types of frames.

In step B above, it is necessary to determine the frame that needs to be restored based on the information related to the collision frame. Before determining a frame that needs to be restored, it is first necessary to set a restoration order corresponding to the related information of the frame. For example, a frame arrival time and / or a restoration order corresponding to different frame types may be set. As a specific setting method, it may be set according to a system request. For example, set the frame or frames that arrived earliest as a restored frame, set the frame or frames that arrived last as a restored frame, or set a certain type of frame as a restored frame To do. Of course, the frame type and the arrival time of the frame may be set in combination.

  Specifically, when reconstructing according to the frame type and targeting the maximum network throughput, for RTS, CTS, DATA and ACK frames, when setting two collision frames to have the same target address, A frame having a high restoration priority is restored and the priority of the frame is defined as ACK = DATA> CTS> RTS. That is, the DATA frame and ACK need to be restored for any collision type. Further, when the RTS frame having the lowest priority is further set and another frame collides with the RTS frame, only when the target address of the other frame is different from the RTS and the end of the RTS frame is late, Restore the RTS frame.

  Based on the above setting for restoring the frame based on the frame type, it can be further set to determine which frame to restore based on the arrival time. For example, if it is determined that the priority of the collision frame is the same, it is possible to determine which frame arrives first and which frame arrives later based on the arrival time. The restoration process is performed on the frame to be processed.

  How to restore a frame based on collision type, frame priority, and arrival time can be processed with reference to the operations given in Table 3.

  In order to simplify the description, a frame collision type may be set. Then, a corresponding restoration method is set based on the frame collision type.

  Hereinafter, taking the wireless LAN standard IEEE802.11b as an example, the determination of the frame collision type when only the collision of two frames is considered will be described. In IEEE802.11b, there are four frame types, and the frame collision can be divided into a total of 16 types of collision based on the arrival order of the frames after the collision. RTS-RTS collision, RTS-CTS collision, RTS-DATA collision, RTS-ACK collision, CTS-RTS collision, CTS-CTS collision, CTS-DATA collision, CTS-ACK collision, DATA-RTS collision, DATA-CTS Collision, DATA-DATA collision, DATA-ACK collision, ACK-RTS collision, ACK-CTS collision, ACK-DATA collision, ACK-ACK collision. Among them, the first frame indicates a frame that has arrived first in the collision. The second frame shows the frame that arrived later in the collision.

  As can be seen from the above, the collision type information is obtained by a synchronization algorithm. Specifically, when a collision occurs, it is possible to determine the type of the two frames that have collided based on the frame type information output by the synchronization algorithm, and based on the magnitude of the symbol shift and code chip shift Thus, the arrival order of the two frames is determined. In this way, the collision type can be determined.

  In step C, frame synchronization is realized by acquiring synchronization information of a frame that needs to be restored and performing a fine synchronization process on the symbol shift value of the frame.

  The frame synchronization information includes a frame type, code chip shift information, and a symbol shift value. These pieces of information can be determined by the spreading sequence corresponding to the sequence maximum power addition value.

  The symbol shift value determined by the spreading sequence is only a coarse synchronization symbol shift value. Specifically, there are 16 known symbols in the rear part of the preamble, which is called a frame start delimiter (SFD) and indicates the start of the physical layer frame head. Depending on the symbol shift value obtained from the maximum sequence power addition value, the position of the SFD may not be determined directly. It can be said that it is not until the frame is synchronized until the SFD is correctly found. Therefore, it is necessary to determine whether or not the symbol shift value is correct based on whether or not the SFD can be determined from the symbol shift value. If not, it is necessary to determine the SFD by finely adjusting the symbol shift value to achieve frame synchronization.

  In Step C, specific processing for performing precise synchronization with respect to the symbol shift value of the frame is as follows.

  The symbol shift value is used as a start position, and 16 symbols are continuously taken from a place away from 128 symbols, that is, 129-144th symbols are taken, and demodulation and decoding are performed on the 16th symbols. If the 16 symbols are SFD, it indicates that the symbol shift value is correct, and the symbol shift value of fine synchronization is equal to the symbol shift value. On the other hand, if the 16 symbols are not SFD, it indicates that it is necessary to finely adjust the symbol shift value. A specific method of fine adjustment is to set an initial radius in advance and search for SFDs in order within the radius with the symbol shift value obtained in step C as the center. When the SFD is searched through the search, the search is terminated, it is determined that the synchronization is successful, and a correct symbol shift value is output. In other cases, the search may be continued until the SFD is searched, and the subsequent search may be performed by expanding the search range to a certain extent. If the SFD cannot be finally found, the synchronization failure is determined. If synchronization fails, it means that the receiving node cannot correctly find the start position of the frame, and therefore the transmission signal cannot be detected. At this time, the receiving node discards the frame and does not perform subsequent detection processing.

  In step D, a frame that can be restored is determined based on the processing in step C, and detection is performed on the frame.

  The processing of steps B and C has a plurality of results. One result is obtaining the synchronization information of the collision frames that need to be reconstructed, ie, the frame type, symbol shift value, and code chip shift value. In this situation, all the frames that need to be restored can be restored. Another result is that a collision occurred and only the synchronization information of the frame that needs to be restored could be obtained. In this situation, only the collision frame from which the synchronization information has been acquired can be restored. Another result is that there was no collision. In addition, synchronization may fail regardless of whether there is a collision.

  If synchronization fails in step D, the frame is directly discarded. When synchronization is successful and no collision occurs, the frame is restored by performing operations such as frame detection, demodulation and decoding directly using the synchronization information of the frame. Thereafter, the media access control layer load is separated from the frame and transmitted to the media access control layer. When synchronization is successful and a collision as described above occurs, processing is performed on a frame that can be restored, that is, a frame that has complete synchronization information and needs to be restored. Specifically, the interference cancellation and detection are performed on the collided frames by first performing serial interference cancellation using the frame synchronization information. Then, the detected frame is demodulated and decoded to restore the initial transmitted frame, and then the load of the media access control layer is separated from the restored frame and transmitted to the media access control layer To do.

  In Step E, after receiving the load of the media access control layer, the receiving node performs NAV setting in the media access control layer using a preset rule.

  The main purpose of NAV setting is to reduce the collision probability.

  The preset rule may allow the data transmission of the exposed node by setting the NAV without using the RTS frame obtained by restoration, or the NAV using the CTS frame obtained by restoration. By setting, the data transmission of the hidden node may be prohibited, or the NAV may be set using the DATA frame obtained by restoration. Table 3 shows the NAV setting rules for different collision types.

In order to further improve the system performance, NAV setting rules may be further set. For example, the NAV of the node is set without using the received RTS frame in which no collision has occurred.

  Table 3 shows operations for different collision types when the goal is to obtain the maximum throughput of the network. In Table 3, the rows indicate the frames that arrived earlier in the collision, and the columns indicate the frames that arrived later in the collision. Table 3 shows operations corresponding to whether to perform frame restoration and to set NAV for each collision type. The reception node may perform a corresponding operation based on the processing shown in Table 3 when performing reception processing on the received signal.

  In order to reduce the calculation complexity of the system, in step A, first, a despreading process may be performed using a certain spreading sequence to synchronize with the frame. The specific synchronization process is the same as that in step C, and thus the description thereof is omitted here. After the frame is synchronized, interference cancellation is performed on the received signal using a known preamble and partly known frame head information in the frame. After canceling the interference, the remaining three spreading siemens are used to despread the signal after the interference cancellation.

  In step B, it is determined whether or not there is a collided frame by comparing the magnitude of the sequence maximum power addition value corresponding to the four spreading sequences with a preset threshold value.

  Correspondingly, in step C, it is not necessary to perform precise synchronization with the first frame. This means that if there is no frame in which a collision has occurred and the maximum power addition value corresponding to the first frame is the final maximum sequence maximum power addition value, frame synchronization processing need not be performed in step C. Means.

  The interference cancellation process in step A is specifically as follows.

  FIG. 5 shows an RTS frame structure at the time of 11 Mbps and 5.5 Mbps data rates in the case of long PLCP and short PLCP. The frame is divided into three parts: preamble, physical layer frame head and media access control layer load. According to FIG. 5, the preamble is completely known and the physical layer frame head is partially known. After the frame type is determined, a part of the frame head of the media access control layer load is also known. The known or partially known portion occupies most of the entire frame length. For long PLCP, known and partially known parts occupy 65% and 22% of the total frame length, respectively. For short PLCP, known and partially known parts occupy 57% and 19% of the total frame length, respectively. In the case of a data rate of 11 Mbps, the specific gravity occupied by the known and part of the known part is even greater. According to the above, the known and partially known parts occupy the largest part of the entire frame length. Therefore, the receiving node can perform interference cancellation using these pieces of information. As a result, the performance can be improved and the calculation complexity of the receiving node can be greatly reduced.

  Performing interference cancellation processing using a known preamble and partially known frame head information is specifically performed by performing channel estimation using the preamble of the first frame, obtaining channel coefficients, and then Replay interference using known preamble information, partially known frame head information and channel coefficients, and from received signal for second frame synchronization and media access control layer load detection The reproduced interference is subtracted to further improve the power ratio of the received signal to the interference. Also, when there is a high SNR or perspective effect during interference playback, for example, better performance can be obtained by performing interference playback of the media access control layer load portion.

  Further, in order to further reduce the complexity of the receiving node, the receiving node may determine whether to restore the received frame based on the state information of this node. For example, if it is assumed that a DATA frame is not transmitted from a certain node, there is always no ACK frame transmitted to the node. In step A, when the node despreads using a different spreading sequence in the physical layer, if it finds an ACK frame, it discards the frame directly and does not perform processing such as signal detection, demodulation / decoding, etc. May be. The processed information does not need to be transmitted to the media access control layer. Obviously, the processing is compared with the means in which the receiving node detects the signal, demodulates and decodes it, transmits it to the media access control layer, determines that the frame is not its own frame in the media access control layer, and discards it. Reduced the processing load on the receiving node.

  In the means of the present invention, the transmission node and the reception node constitute a system, and the system is called a frame collision processing system.

  In the system, the transmission node processes information bits input to the node using a preset spreading sequence, and transmits the processed information bits to the reception node.

  The receiving node performs a despreading process on the entire received signal using a preset spreading sequence, and obtains a sequence maximum power addition value corresponding to each spreading sequence, a corresponding symbol shift, and a corresponding code chip shift. By acquiring and comparing each sequence maximum power addition value and a preset threshold value, it is determined whether a frame collision has occurred, and if there is a collision frame, based on the relevant information of the collision frame, When a frame that needs to be restored is determined and no frame collision occurs, the maximum sequence maximum power addition value is selected from all the sequence maximum power addition values to obtain the total maximum sequence maximum power addition value. The frame corresponding to the spreading sequence corresponding to the maximum sequence power addition value is determined and confirmed. By performing fine synchronization processing on the frame that has been determined, a frame that can be restored is determined, and by detecting the frame, the media access control layer load is obtained, and a predetermined rule is set in the media access control layer. To set the network allocation vector NAV.

As described above, the transmission node may transmit at a low data rate or a high data rate. When transmitting at a low data rate, the node has a MOD module and a spreading module, as shown in FIG.
The MOD module modulates the received information bits and sends them to the spreading module,
The spreading module spreads the corresponding frame of the received information bits using a preset spreading sequence.

When the transmission node transmits at a high data rate, as shown in FIG. 3B, it has a MOD module, a diffusion module, a CCK module, and a multiplexing module,
The MOD module receives the preamble of information bits and the physical layer frame head, modulates it and sends it to the spreading module;
The spreading module spreads the received preamble and the physical layer frame head using a preset spreading sequence and sends it to the multiplexing module,
The CCK module receives the media access control layer load of the information bits, performs CCK spread modulation on it, sends the processed information to the multiplexing module,
The multiplexing module multiplexes and transmits the information transmitted from the spreading module and the CCK module.

The receiving node has a despreading module, a threshold comparison module, a synchronization module, and a NAV setting module, as shown in FIG.
The despreading module performs a despreading process on the entire received signal using a preset spreading sequence, and adds a sequence maximum power addition value corresponding to each spreading sequence, a corresponding symbol shift, and a corresponding code chip shift. Is sent to the threshold comparison module,
The threshold comparison module determines whether or not a frame collision has occurred by comparing the sequence maximum power addition value corresponding to each spreading sequence with a preset threshold, and if there is a collision frame, Based on the related information, the frame that needs to be restored is determined, the frame is transmitted to the synchronization module, and if no frame collision occurs, the maximum sequence maximum power addition is selected from all the sequence maximum power addition values. Select a value as the total maximum sequence maximum power addition value, determine the frame corresponding to the spreading sequence corresponding to the sequence maximum power addition value, and send the frame to the synchronization module;
The synchronization module determines the frame that can be restored by performing fine synchronization processing on the frame, acquires the media access control layer load by detecting the frame, and transmits the load to the NAV setting module. And
The NAV setting module sets the NAV using a preset rule.

The despreading module further includes a despreading processing module, a sliding window processing module, and a comparison module, of which
The despreading processing module performs a despreading process on the entire received sequence using the spreading sequence to obtain the first sequence, and then cyclically shifts the code chips of the spreading sequence in order, Using the spreading sequence obtained by shifting every time, each received signal is despread, the same sequence as the number of code chips of the spreading sequence is acquired, and transmitted to the sliding window processing module,
The sliding window processing module performs the sliding window power addition for each obtained sequence using the sliding window, and compares them to obtain the sequence maximum power addition value and the corresponding symbol shift for each sequence. To the module,
The comparison module compares the obtained sequence maximum power addition value, records the corresponding sequence maximum power addition value, the corresponding symbol shift, and the corresponding code chip shift, if necessary, and transmits them to the threshold comparison module.

In the threshold value comparison module, determining whether or not a frame collision has occurred by comparing the sequence maximum power addition value corresponding to each spreading sequence with a preset threshold value depends on each sequence maximum power addition value in advance. Compared with the set threshold, if two or more sequence maximum power addition value is larger than the threshold, it is determined that a frame collision has occurred, otherwise, it is determined that there is no frame collision,
Alternatively, the maximum sequence maximum power addition value and finally the second largest sequence maximum power addition value are finally obtained by comparing all the sequence maximum power addition values, and finally the second largest sequence maximum power value. It is determined whether the power addition value is greater than a preset threshold value. If the power addition value is large, it is determined that a collision between two frames has occurred. In other cases, it is determined that there is no frame collision.
Or, by comparing all the sequence maximum power addition values, finally the maximum sequence maximum power addition value, finally the second largest sequence maximum power addition value, and finally the third largest sequence maximum power addition value And finally determine whether the second largest sequence maximum power addition value and finally the third largest sequence maximum power addition value are larger than a preset threshold, and finally the second largest If only the sequence maximum power addition value is greater than the threshold value, it is determined that two frames have collided. Finally, if the third largest sequence maximum power addition value is greater than the threshold value, it is determined that three frame collisions have occurred. Finally, the second largest sequence maximum power addition value and the third largest sequence maximum power addition value If both smaller than the threshold value, it is determined that no frame collision.

In the threshold comparison module, determining a frame that needs to be restored based on the related information of the collision frame determines the collision frame based on the related information of the collision frame, and sets information corresponding to the collision frame and a preset value. Using the restored restoration rules to determine which collision frames need to be restored,
Alternatively, the collision frame is determined based on the related information of the collision frame, the corresponding frame collision type is determined based on the collision frame, and the frame collision type and the relationship between the preset frame collision type and the restored frame are determined. Determine the collision frames that need to be restored.

  Specifically, when a frame collision occurs, the NAV module sets the NAV without using the restored RTS frame, thereby allowing the data transmission of the exposed node and the restored CTS. By setting the NAV using the frame, the data transmission of the hidden node is prohibited, the NAV is set using the DATA frame obtained by the restoration, or the received collision has not occurred. At least one of setting the NAV of the node without using the RTS frame is performed.

  Further, when there is no frame collision, the NAV module updates its own NAV value with the NAV when the received NAV value of the media access control layer load is larger than the own NAV value, and when it is smaller, The NAV value is maintained.

  The above is only a relatively preferred embodiment of the present invention and does not limit the protection scope of the present invention.

FIG. 1 is a diagram showing processing by a conventional MPR-p algorithm. FIG. 2A is a configuration diagram of a transmission node for a low data rate according to the present invention. FIG. 2B is a configuration diagram of a transmission node for a high data rate according to the present invention. FIG. 3A is a diagram showing a spreading method for spreading on a frame in the case of a low data rate according to the present invention. FIG. 3B is a diagram showing a spreading method for spreading the frame in the case of a high data rate according to the present invention. FIG. 4A is a diagram showing processing of the receiving node according to the present invention. FIG. 4B is a configuration diagram of a receiving node according to the present invention. FIG. 5 is a diagram showing the proportion occupied by a known preamble and a part of a known frame head in a frame. FIG. 6 is a diagram illustrating a proportion between a case where two frames collide and a case where a plurality of frames collide. FIG. 7 is a simulation result diagram of the system frame error rate performance when there is no perspective effect and the control frame of the same type collides when the data rate is 5.5 Mbps. FIG. 8 is a simulation result diagram of the system frame error rate performance when there is no perspective effect and when different types of control frames collide when the data rate is 5.5 Mbps. FIG. 9 is a simulation result diagram of system frame error rate performance when there is no perspective effect and the data frame collides with the control frame when the data rate is 5.5 Mbps. FIG. 10 is a simulation result diagram of system frame error rate performance when there is no perspective effect and when data frames collide with each other when the data rate is 5.5 Mbps. FIG. 11 is a simulation result diagram of the system frame error rate performance when there is no perspective effect and when different types of control frames collide when the data rates are 1 Mbps and 2 Mbps. FIG. 12 is a simulation result diagram of the system frame error rate performance in the case where different types of control frames collide when there is no perspective effect and the data rates are 5.5 Mbps and 11 Mbps. FIG. 13 is a simulation result diagram of system frame error rate performance when there is a perspective effect and when different types of control frames collide when the data rate is 5.5 Mbps. FIG. 14 is a simulation result diagram of the system frame error rate performance when there is a perspective effect and the data frames collide when the data rate is 5.5 Mbps. FIG. 15 is a comparison diagram of network throughput performance between the basic DCF algorithm and the algorithm according to the present invention. FIG. 16 is a comparison diagram of transmission delay performance between the basic DCF algorithm and the algorithm according to the present invention. FIG. 17 is a comparison diagram of the network throughput performance of the RTS / CTS handshake DCF algorithm and the algorithm according to the present invention. FIG. 18 is a comparison diagram of transmission delay performance between the RTS / CTS handshake DCF algorithm and the algorithm according to the present invention. FIG. 19 is a flowchart showing processing of the receiving node according to the present invention.

Explanation of symbols

ae ... step, AE ... step, AB ... node, a1-a2 ... step, b1-b3 ... step

Claims (25)

Preset a spreading sequence that uniquely corresponds to each frame type,
A step in which the transmitting node performs processing on information bits input to the present node using the spreading sequence, and then transmits to the receiving node;
The receiving node performs despreading processing on the entire received signal using the spreading sequence to obtain a sequence maximum power addition value corresponding to each spreading sequence, a corresponding symbol shift, and a corresponding code chip shift. b,
The receiving node determines whether or not a frame collision has occurred by comparing the sequence maximum power addition value corresponding to each spreading sequence with a preset threshold value. Based on the related information, a frame that needs to be restored is determined, the process of step d is performed on the frame, and if there is no collided frame, the maximum sequence maximum of all sequence maximum power addition values A step c for setting a power addition value as a total maximum sequence maximum power addition value, determining a frame corresponding to a spreading sequence corresponding to the sequence maximum power addition value, and performing the process of step d on the frame;
The receiving node obtains the frame synchronization information, performs fine synchronization processing on the symbol shift value of the frame to realize frame synchronization, thereby determining a frame that can be restored and performs detection on the frame. Obtaining a media access control layer load of the frame;
A frame collision processing method, wherein the receiving node includes a step e of setting a network allocation vector NAV using a predetermined rule in the media access control layer. If the sending node sends at a low data rate,
In step a, the transmitting node modulates information bits input to the node, and then performs processing for spreading the corresponding frame using the spreading sequence for the information bits using the spreading sequence. The method according to claim 1, wherein the method is performed. If the sending node sends at a high data rate,
In step a, the transmitting node groups the preamble of information bits input to the node and the physical layer frame head into one group, the media access control layer load into another group, modulates the previous group, and , Spreading the corresponding frame using the spreading sequence, performing complementary code key input spreading modulation on the subsequent group, and finally multiplexing the two groups of processed data, The method of claim 1, wherein the method performs the information bits using a spreading sequence. In the step b, the receiving node despreads the signal using each spreading sequence,
Using the spreading sequence, the entire received sequence is despread to obtain the first sequence, and the code chip of the spreading sequence is cyclically shifted in order, and the spreading sequence obtained by shifting each time is obtained. Step b1 in which each received signal is despread to obtain the same number of sequences as the number of code chips in the spreading sequence, and one code chip shift is associated with each sequence;
Step b2 for obtaining a sequence maximum power addition value and a corresponding symbol shift of each sequence by performing slide power addition for each sequence using a slide window and comparing each sequence obtained, and
The step b3 comprises comparing the sequence maximum power addition values in step b2 and, if necessary, recording the corresponding sequence maximum power addition values, the corresponding symbol shifts and the corresponding code chip shifts. The method according to 1.   In step b3, the process of recording as necessary is to record all the sequence maximum power addition values, the corresponding symbol shifts and the corresponding code chip shifts, or two of the sequence maximum power addition values from the larger one. 5. The method according to claim 4, wherein the process is a process of recording a maximum number of sequence maximum power addition values, corresponding symbol shifts and corresponding code chip shifts from the largest. In the step c, the receiving node compares the sequence maximum power addition value corresponding to each spreading sequence with a preset threshold value,
Each sequence maximum power addition value is compared with a preset threshold value. When two or more sequence maximum power addition values are larger than the threshold value, it is determined that a frame collision has occurred. In other cases, there is no frame collision. Is to judge,
Alternatively, the maximum sequence maximum power addition value and finally the second largest sequence maximum power addition value are finally obtained by comparing all the sequence maximum power addition values, and finally the second largest sequence maximum value. It is determined whether or not the power addition value is larger than a preset threshold value. If the power addition value is larger, it is determined that a collision between two frames has occurred. In other cases, it is determined that there is no frame collision.
Or, by comparing all the sequence maximum power addition values, finally the maximum sequence maximum power addition value, finally the second largest sequence maximum power addition value, and finally the third largest sequence maximum power addition value And finally determine whether the second largest sequence maximum power addition value and finally the third largest sequence maximum power addition value are larger than the threshold value, and finally the second largest sequence maximum power addition value. If only the sum is greater than the threshold, it is determined that two frames have collided. Finally, if the third largest sequence maximum power sum is greater than the threshold, it is determined that three frames have collided. The second largest sequence maximum power addition value and finally the third largest sequence maximum power addition value. If less than the monitor threshold method according to claim 1, characterized in that by determining that no frame collision. In step c, determining the frame that needs to be restored based on the related information of the collision frame includes:
A collision frame is determined based on information related to the collision frame, and a collision frame that needs to be restored is determined using information corresponding to the collision frame and a preset restoration rule. The method of claim 1.   The preset restoration rule is a restoration rule set based on a frame arrival time, a restoration rule set based on a frame type, or a restoration rule set based on a preset frame priority. The method according to claim 7, comprising at least one of the following: In step c, based on the related information of the collision frame, determining a frame that needs to be restored is:
Determine the collision frame based on the related information of the collision frame, determine the corresponding frame collision type based on the collision frame, and based on the relationship between the frame collision type and the preset frame collision type and the restored frame, The method according to claim 1, characterized in that the collision frames that need to be restored are determined.   In step c, determining the corresponding frame collision type based on the collision frame determines the frame type of the collision frame, and determines the arrival order of the collision frames based on the size of the symbol shift and code chip shift. 10. The method of claim 9, wherein determining is to determine a type of frame collision. In step d, the receiving node performs a fine synchronization process on the symbol shift value of the frame.
A symbol shift value is used as a start position, a plurality of symbols are continuously taken with a specific numerical value, and demodulation and decoding are performed on the symbols. When the taken symbol is a frame start delimiter SFD, the symbol shift value is correct. The symbol shift value of fine synchronization is equal to the symbol shift value, and in other cases, fine adjustment is performed, and the fine adjustment is performed by setting an initial radius in advance and centering on the symbol shift value. The method according to claim 1, wherein the SFD is searched in order. If it is determined in step c that a frame collision has occurred, the determination of the frame that the receiving node can restore in step d is a collision that has complete synchronization information and needs to be restored. The frame is determined to be a recoverable frame,
If it is determined in step c that there is no frame collision, in step d, the frame that can be restored by the receiving node is determined. In step c, the frame corresponding to the total maximum power addition value has complete synchronization information. The method according to claim 1, wherein the frame is determined to be a frame that can be restored and the frame can be restored.   The pre-set rules used in step e allow or restore the exposed node's data transmission by setting the NAV without using the transmission request RTS frame obtained by restoration when a frame collision occurs. By setting the NAV using the transmission permission CTS frame obtained in the above, prohibiting the data transmission of the hidden node, allowing the setting of the NAV using the data DATA frame obtained by the restoration, or The method according to claim 1, comprising at least one of setting a NAV of a node without using a received RTS frame in which no collision has occurred.   The pre-set rule used in step e is to update its own NAV value with the NAV when the received media access control layer load NAV value is greater than its own NAV value when there is no frame collision, 2. The method of claim 1, wherein the method maintains its own NAV value otherwise. In step b, the receiving node performs a despreading process on the entire signal using the spreading sequence,
First, a signal is despread by an arbitrary spreading sequence to obtain a corresponding sequence maximum power addition value, a corresponding symbol shift, and a corresponding code chip shift, and fine synchronization processing is performed on the symbol shift value. Step a1 for realizing the synchronization of the sequence maximum power addition value and the corresponding frame by performing
After synchronizing with the frame, using the known preamble and partially known frame head information of the frame, canceling the interference with the received signal, using the remaining spreading sequence, Step a2 for performing despreading processing on the signal after canceling interference;
The method of claim 1, comprising: In the step a2, the interference cancellation process includes
Channel estimation is performed using the preamble information of the frame obtained in step a1 to obtain a channel coefficient, interference reproduction is performed using known preamble information, partially known frame head information and the channel coefficient, The method of claim 15, wherein the process is subtracting the reproduced interference from a received signal. After step a and before step d,
The receiving node determines a corresponding frame based on the obtained sequence maximum power addition value, and determines, based on the status information of the node, whether the frame is a frame that needs to be restored;
2. The method according to claim 1, wherein the corresponding processing in step b and step c is performed only on a frame determined to require the restoration processing. The frame collision processing system has a transmitting node and a receiving node,
The transmitting node performs processing on the information bits input to the present node using a preset spreading sequence, transmits the processed information bits to the receiving node,
The receiving node performs a despreading process on the entire received signal using a preset spreading sequence, and obtains a sequence maximum power addition value corresponding to each spreading sequence, a corresponding symbol shift, and a corresponding code chip shift. By acquiring and comparing each sequence maximum power addition value and a preset threshold value, it is determined whether a frame collision has occurred, and if there is a collision frame, based on the relevant information of the collision frame, When a frame that needs to be restored is determined and no frame collision occurs, the maximum sequence maximum power addition value is selected from all the sequence maximum power addition values to obtain the total maximum sequence maximum power addition value. Confirm the frame corresponding to the spreading sequence corresponding to the maximum sequence power addition value, and confirm The frame that can be restored is determined by performing a fine synchronization process on the received frame, and the media access control layer load is obtained by detecting the frame, and is preset in the media access control layer. A network allocation vector NAV is set using the rule. When the transmitting node transmits at a low data rate, the transmitting node has a MOD module and a spreading module;
The MOD module modulates the received information bits and sends them to the spreading module,
The system of claim 18, wherein the spreading module spreads the corresponding frame of the received information bits using a preset spreading sequence. When the transmitting node transmits at a high data rate, the transmitting node has a MOD module, a spreading module, a complementary code key input CCK module, and a multiplexing module;
The MOD module receives the preamble of information bits and the physical layer frame head, modulates it and sends it to the spreading module;
The spreading module spreads the received preamble and the physical layer frame head using a preset spreading sequence and sends it to the multiplexing module,
The CCK module receives the media access control layer load of the information bits, performs CCK spread modulation on it, sends the processed information to the multiplexing module,
The system according to claim 18, wherein the multiplexing module multiplexes and transmits the information transmitted from the diffusion module and the CCK module. The receiving node includes a despreading module, a threshold comparison module, a synchronization module, and a NAV setting module,
The despreading module performs a despreading process on the entire received signal using a preset spreading sequence, and adds a sequence maximum power addition value corresponding to each spreading sequence, a corresponding symbol shift, and a corresponding code chip shift. Is sent to the threshold comparison module,
The threshold comparison module determines whether or not a frame collision has occurred by comparing the sequence maximum power addition value corresponding to each spreading sequence with a preset threshold, and if there is a collision frame, Based on the related information, the frame that needs to be restored is determined, and the frame is transmitted to the synchronization module. When no frame collision occurs, the maximum sequence maximum power is selected from all the sequence maximum power addition values. Select the addition value as the total maximum sequence maximum power addition value, determine the frame corresponding to the spreading sequence corresponding to the sequence maximum power addition value, and send the frame to the synchronization module;
The synchronization module determines a frame that can be restored by performing fine synchronization processing on the frame, obtains the media access control layer load by performing detection on the frame, and sets the load to NAV. To the module,
The system of claim 18, wherein the NAV setting module sets the network allocation vector NAV using a preset rule. The despreading module further includes a despreading processing module, a sliding window processing module, and a comparison module.
The despreading processing module performs despreading processing on the entire received sequence using the spreading sequence to obtain the first sequence, and then cyclically shifts and shifts the code chips of the spreading sequence in order. Using the spreading sequence obtained each time, each received signal is subjected to despreading processing to obtain the same number of sequences as the number of code chips of the spreading sequence, and sent to the sliding window processing module,
The sliding window processing module performs the sliding window power addition for each obtained sequence using the sliding window, and compares them to obtain the sequence maximum power addition value and the corresponding symbol shift for each sequence. To the module,
The comparison module compares the obtained sequence maximum power addition value, records the corresponding sequence maximum power addition value, the corresponding symbol shift, and the corresponding code chip shift, if necessary, and transmits them to the threshold comparison module. The system according to claim 21, characterized in that The threshold comparison module determines whether a frame collision has occurred by comparing a sequence maximum power addition value corresponding to each spreading sequence with a preset threshold value,
Each sequence maximum power addition value is compared with a preset threshold value. When two or more sequence maximum power addition values are larger than the threshold value, it is determined that a frame collision has occurred. In other cases, there is no frame collision. Judgment,
Alternatively, the maximum sequence maximum power addition value and finally the second largest sequence maximum power addition value are finally obtained by comparing all the sequence maximum power addition values, and finally the second largest sequence maximum power value. It is determined whether or not the power addition value is greater than a preset threshold value. If it is larger, it is determined that a collision between two frames has occurred. In other cases, it is determined that there is no frame collision.
Or, by comparing all the sequence maximum power addition values, finally the maximum sequence maximum power addition value, finally the second largest sequence maximum power addition value, and finally the third largest sequence maximum power addition value And finally determine whether the second largest sequence maximum power addition value and finally the third largest sequence maximum power addition value are greater than the threshold, and finally the second largest sequence maximum power addition value. If only the sum is greater than the threshold, it is determined that two frames have collided. Finally, if the third largest sequence maximum power sum is greater than the threshold, it is determined that three frames have collided. The second largest sequence maximum power addition value and finally the third largest sequence maximum power addition value. If the less than the threshold, the system according to claim 21, characterized in that by determining that no frame collision. Determining the frame that the threshold comparison module needs to be restored based on the related information of the collision frame;
Determine the collision frame based on the related information of the collision frame, determine the collision frame that needs to be restored using information corresponding to the collision frame and a preset restoration rule,
Alternatively, the collision frame is determined based on the related information of the collision frame, the corresponding frame collision type is determined based on the collision frame, and the frame collision type and the relationship between the preset frame collision type and the restored frame are determined. The system according to claim 21, characterized in that a collision frame that needs to be restored is determined.   When a frame collision occurs, the NAV module sets the NAV without using the restored RTS frame to allow the data transmission of the exposed node and uses the restored CTS frame. By setting the NAV, the data transmission of the hidden node is prohibited, the NAV is allowed to be set using the DATA frame obtained by the restoration, or the received RTS frame in which no collision has occurred. 19. The system of claim 18, including at least one of setting a node's NAV without using.

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