CN108738100B - Cache information assistance-based high-coding-opportunity bidirectional access method - Google Patents

Cache information assistance-based high-coding-opportunity bidirectional access method Download PDF

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CN108738100B
CN108738100B CN201810316092.2A CN201810316092A CN108738100B CN 108738100 B CN108738100 B CN 108738100B CN 201810316092 A CN201810316092 A CN 201810316092A CN 108738100 B CN108738100 B CN 108738100B
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source node
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CN108738100A (en
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姚玉坤
李小勇
刘江兵
李威
濮浩
周海东
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Chongqing University of Post and Telecommunications
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/22—Communication route or path selection, e.g. power-based or shortest path routing using selective relaying for reaching a BTS [Base Transceiver Station] or an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/1607—Details of the supervisory signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L49/00—Packet switching elements
    • H04L49/90—Buffering arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L67/00—Network arrangements or protocols for supporting network services or applications
    • H04L67/50—Network services
    • H04L67/56—Provisioning of proxy services
    • H04L67/568—Storing data temporarily at an intermediate stage, e.g. caching
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/06—Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

The invention provides a cache information auxiliary-based high-coding-opportunity bidirectional access method which is mainly applied to a two-hop relay network and mainly comprises a coding matching stage for sending a control message and a data transmission stage after matching, wherein three new mechanisms of replacing four-way handshake with two-way handshake, improving coding opportunity by cache information auxiliary and updating a virtual cache region by modifying a frame format are adopted; the first and second new mechanisms work in the code matching stage, the third new mechanism works in the data transmission stage, and by using the three new mechanisms, the new access method provided by the invention can reduce the control overhead of unnecessary message interaction process, and can effectively improve the coding opportunity, thereby fully utilizing the network coding technology on the whole to realize the purposes of reducing the average time delay of data frames and increasing the throughput of the network.

Description

Cache information assistance-based high-coding-opportunity bidirectional access method
Technical Field
The invention belongs to the technical field of wireless communication, mainly aims at an application scene of a two-hop relay network, mainly aims at a scene of using a relay node to exchange data between a source node and a destination node, and more particularly relates to a cache information assistance-based high-coding opportunity bidirectional access method.
Background
The network coding technology is an information exchange technology for effectively fusing coding data and routing information, and the main idea is that a relay node transmits intercepted or cached data to other nodes after coding, and other nodes transmit the data to a destination terminal according to the same operation mode until a data frame reaches the destination terminal. The network coding technology can achieve the purpose of enhancing the network performance by increasing the information amount of a unit time slot, and the intermediate node codes and sends the received information, so that the multicast transmission can achieve the highest transmission capacity theoretically, the network throughput of the system can be effectively improved, and the method also has the advantages of reducing the network energy consumption, balancing the load, improving the network robustness and the like.
Both the analog network coding and the physical layer network coding are branches of network coding, which are mainly applied to a bidirectional relay network, through one of the technologies, two terminal users can simultaneously send data frames to a relay node, and the relay node effectively codes the superposed signals by using the physical layer network coding technology and then sends the superposed signals to the two terminal users, so that the transmission times of the data frames can be effectively reduced, and the network throughput is increased.
The main operation of the access mode of the data is performed in the MAC layer, and the MAC layer performs corresponding processing and operation on the transmission of the control frame and the data frame, so that the collision of the data frame can be effectively reduced and the utilization rate of the channel can be improved. In the current research situation at home and abroad, aiming at the situation that a source node and a destination node have data exchange with each other, document [1] proposes a bidirectional cooperation MAC protocol based on network coding for a bidirectional relay network, and aiming at a three-hop relay network scene, in a first time slot, the source node and the destination node respectively send respective data frames to respective next hops, the source next hop sends the source data frames to the next hop of the destination node, then the next hop of the destination node performs coding operation on the received data frames and sends the destination node and the next hop of the source node, and then the source node and the destination node can obtain corresponding data frames from each other. [1] Li Y, Xie Y, Peng M, et al. Joint Cooperative MAC and Network Coding for Two-way Relay Networks [ C ]// International Conference on Cyber-Enabled Distributed Computing and Knowledge distribution. IEEE Computer Society 2014: 478-.
Document [2] proposes a distributed MAC protocol based on Physical Layer Network Coding, which is different from a traditional access mode, and performs channel reservation through a relay node, that is, firstly, the relay node sends a Request To Send-Physical Layer Network Coding (RTS-PNC) control frame To reserve a channel, the control frame includes a source node address and a destination node address, and two nodes receiving the RTS-PNC message judge whether data are sent To each other, if data are sent, a Clear To Send (CTS) control message is replied, otherwise, a CTS message is not replied; at this time, the relay node determines whether to perform physical Layer Network coding operation according to the number of the received RTS frames, and if a data frame is received, the relay node transmits the data to the destination node in a conventional manner, and if two CTS frames are received, it indicates that physical Layer Network coding (pnc) can be used, thereby effectively solving the problem of data exchange between nodes. [2] Wang S, Song Q, Wang X, et al, distributed MAC Protocol Supporting Physical-Layer Network Coding [ J ]. IEEE Transactions on Mobile Computing,2013,12(5):1023 + 1036.
Document [3] proposes a random access method based on analog network coding, which mainly aims at a two-hop relay network application scenario, and firstly, a source node sends an RTS message To request an access channel, the RTS frame format includes a destination address of the next two hops, and after receiving the RTS, a relay node continues To broadcast an rtc (request To code) message; after receiving the RTC message, the destination node replies an ATC (answer To Cooperate) message, the relay node broadcasts a CTS message according To the received ATC message, the CTS message indicates whether data exchange exists between the two nodes, if so, the CTS message indicates that network coding operation can be carried out, and the data exchange between the two nodes is efficiently realized by adopting a network coding technology; the protocol also provides a flow compensation mechanism aiming at the condition that the destination node has no data exchange, namely when the destination terminal does not reply the ATC message in the set time and other nodes close to the destination terminal discover that the data is sent to the source node, the node replies the ATC message in the set time, so that the relay node can use the network coding technology as much as possible, thereby improving the coding opportunity and increasing the network throughput. [3] Mao W, Wang X, Tang A, et al. ANC-ERA: Random Access for Analog Network Coding in Wireless Networks [ J ]. Mobile Computing IEEE Transactions on,2016,15(1):45-59.
For the research of the bidirectional access method based on network coding in the document [3], in the scheme, it is determined whether four handshakes are needed for data exchange, which results in large control overhead, and the historical cache information is not fully utilized to accurately determine the coding opportunity, which results in insufficient utilization of the coding, and for this situation, it is necessary to provide a new access method, if the information of the data frame is cached, it can be determined whether the coding opportunity exists through two handshakes, and the problem of increasing the coding opportunity through a stream compensation mechanism is solved, so that the network throughput can be greatly improved. The present invention will therefore provide a practical solution to these problems.
Disclosure of Invention
In order to solve the problems of the existing bidirectional access method based on network coding, the invention provides a high-coding-opportunity bidirectional access method based on cache information assistance. The method comprises a new mechanism of replacing four-way handshake with two-way handshake; a new mechanism of 'buffering information to assist in improving coding opportunity'; the new mechanism of updating the virtual cache region is realized by modifying the frame format, and the new access method provided by the invention can fully improve the coding opportunity and reduce the control overhead, thereby fully utilizing the network coding technology on the whole to realize the purposes of reducing the average time delay of the data frame and increasing the throughput of the network.
First, the basic principle of the new mechanism proposed by the present invention
The basic principles of the new mechanism of replacing four-way handshake with two-way handshake, the new mechanism of improving coding opportunity with the assistance of buffer information, and the new mechanism of updating virtual buffer by modifying frame format are described in detail below.
1. New mechanism for replacing four-way handshake with two-way handshake
As shown in fig. 2, in the frame format of the RTS control message, the frame format DNAP field is used to store a destination index ID number corresponding to a data frame to be sent in the node cache queue; as shown in fig. 3, the frame format of the CTS message includes an AD field, where the AD field includes two fields, AD1 and AD2, which are respectively used to identify the address of a node that needs to transmit a data frame; and each node cache queue has two cache regions, one is an actual cache queue for caching actual data frames, and the other virtual cache region is used for recording index ID numbers corresponding to the data frames, the specific operation steps of the two-time handshake mechanism are as follows:
step 1, when a node has data to send, for example, the node a in fig. 1, it broadcasts an RTS message, where the DNAP field in the RTS message stores destination index ID numbers corresponding to N data frames to be sent, and after receiving the RTS message, the relay node B extracts the ID number corresponding to the DNAP field and buffers the corresponding information in its virtual buffer area.
Step 2, the relay node B that receives the RTS message starts to match the index ID corresponding to the data frame in the virtual buffer, as shown in fig. 1, when a node having data exchange with the node a is found, it is assumed here to be node C, and the relay node B adds the address of C and the address of node a to the DA field corresponding to the CTS message, and then broadcasts and transmits the address.
And 3, if other nodes find that the DA field of the CTS message does not have the address of the other nodes, the rest nodes wait in a silent mode, and the nodes corresponding to the DA field in the CTS message are confirmed to send the data frame to the relay node B.
2. Novel mechanism for improving coding opportunity by aid of cache information
In the mechanism, each node maintains two buffer areas, one buffer area is used for buffering an actual data frame and is called an actual buffer area, the other buffer area is used for recording the data frame and is called a virtual buffer area, the structure diagram of the buffer area is shown in fig. 4, information such as the number of data frames to be sent by neighboring nodes, the source ID and the destination ID of the data frame, and the number of hops the data frame needs to pass through is stored in the virtual buffer area, and the actual buffer area buffers the received data frame. The specific operation steps of the new mechanism for improving the coding opportunity by the aid of the cache information are as follows:
step 1, in the t-th time slot, a certain node a (assumed to be a) having data transmission first requests to transmit an RTS control message, which contains the destination index ID of N data frames in its data buffer and the destination address of the first data frame to be transmitted in its buffer, and the address is stored in the RTS frame format CA field.
Step 2, after receiving the RTS message, the relay node B firstly updates the virtual buffer area of the relay node B and then carries out code matching; that is, checking whether other nodes with the destination ID of the node A exist in the virtual cache region, and if so, entering the step 3; otherwise, if the data frame does not exist, in the t +1 time slot, the relay node B replies a CTS message, an AD field corresponding to the CTS message is empty, and after the source node receives the CTS message, the source node B sends the data frame to be sent to the relay node B.
Step 3 may have a plurality of conditions that satisfy code matching, and at this time, the relay node B determines which node is selected as the code matching node according to the number of data frames in the virtual buffer and the hop count, as shown in fig. 4, at this time, both the node C, E, F, G, H have data to the node a, but only the nodes C and F that satisfy two hops, and at this time, the nodes C and F have 5 and 4 data to the node a, respectively, so the node C with the larger number is selected as the code matching node, at this time, the relay node B adds the addresses of the node C and the node a to the AD1 and the AD2 of the AD field of the CTS message, and then broadcasts and transmits, and the a node and the C node that receive the CTS message transmit their own data frames to the node B at the time slot t +2, thereby completing code matching.
3. New mechanism for updating virtual cache by modifying frame format
In the mechanism, the RTS, CTS and ACK frame structures need to be effectively modified, so that the purpose of improving the coding opportunity can be achieved by using two times of handshaking. Specific fields of RTS and CTS control frame formats are shown in fig. 2 and fig. 3, respectively, which have already been introduced above and are not described again in this section; the frame format corresponding to the ACK frame is shown in fig. 5, and the field also includes a DNAP field, which is used for the node to update information corresponding to the data frame of the virtual buffer. On one hand, the virtual cache region can be effectively updated by sending RTS information through the node; on the other hand, after the relay node sends the encoded data frame to the two code matching nodes, the two code matching nodes broadcast the ACK message to the relay node, the DNAP field of the ACK message contains the ID of the N cache data corresponding to the destination, and the relay node and other nodes update their own virtual cache area immediately after receiving the ACK message.
Secondly, the main operation of the high coding opportunity bidirectional access method based on the buffer information assistance proposed by the invention
The invention provides a cache information auxiliary-based high-coding-opportunity bidirectional access method, which comprises a code matching stage for sending a control message and a data transmission stage after matching, wherein the main operation in the code matching stage is to perform code matching on a data frame according to an RTS/CTS control message sent between nodes, so that network coding operation can be performed between the nodes through a relay node; the main operation in the data transmission stage is that the source node sends a data frame, the relay node adopts a network coding technology to efficiently complete data exchange, and the node effectively updates the cache information of the node according to the received RTS frame and the replied ACK frame each time; the cache information assistance-based high-coding-opportunity bidirectional access method provided by the invention comprises (1) a new mechanism of replacing four-way handshake with two-way handshake; (2) a new mechanism of 'buffering information to assist in improving coding opportunity'; (3) the new mechanism of updating the virtual cache region is realized by modifying the frame format; the first and second new mechanisms work in the code matching stage, and the third new mechanism works in the data transmission stage.
The main operation steps of each part are as follows:
1. code matching stage
The cache information assisted high coding opportunity bidirectional access method provided by the invention firstly sends an RTS reservation channel when the core operation is that the node has data to send in the code matching stage, and the relay node carries the target ID number of N data in the current cache region according to the RTS message, so that the network coding technology can be fully utilized. When a network is initialized, nodes send HELLO messages to confirm neighbor nodes, route information is constructed through the messages, each node can be a source node, a destination node or a relay node, so that each node has two buffer areas, namely a virtual buffer area and an actual buffer area, when the node generates data and needs to send, the node sends an RTS reservation channel to become the source node, and other nodes do not try to send the RTS messages again after receiving the RTS messages.
Step 1, when the network is initialized, the node firstly acquires the information of the neighbor node through the HELLO message, and can establish a routing table through the message and establish an index ID number mapped as a destination address. Now, only a two-hop relay network scene is taken as a research object, and a network model diagram constructed by the scene is shown in fig. 1.
Step 2, in the t-th time slot, when a certain node i has data to send, it broadcasts RTS message, after receiving RTS message, a relay node j extracts the ID number corresponding to its DNAP field, and combines the address information of RTS message to effectively update the virtual buffer area, then detects whether there is node N in the virtual buffer areak(k is 1,2,3.. n.) there are also data frames to be sent to the node i, if yes, the step 3 is carried out; otherwise, if the message does not exist, the relay node j replies a CTS message in the t +1 time slot, the AD field content corresponding to the message is empty, after receiving the CTS message, the node i directly sends the data to be sent to the relay node j, and the node j forwards the data to the destination node corresponding to the data frame.
Step 3 at this time, there may exist a situation that a plurality of nodes all have data frames to be sent to the node i, and the code matching is satisfied, if there is only one node N1If the code matching is satisfied, the relay node j connects the node i with the node N1Is added into AD1 and AD2 of the AD field of the CTS message, and is broadcast and transmitted in the t +1 time slot, and the node N1And after receiving the CTS message, the node i immediately sends the data frame required to be sent to the relay node j in the t +2 time slot. If not only one node NkIf code matching is satisfied, step 4 is entered.
Step 4 Relay node j rootAccording to node N in the virtual cache regionkThe number of data frames and the number of hops in the CTS message determine which node to select as the code matching node, as shown in fig. 4, at this time, the node C, E, F, G, H has data to the node a, but only the nodes C and F satisfying two hops, and at this time, the nodes C and F have 5 and 4 data to the node a, respectively, so that the node C with a larger number of data frames is selected as the code matching node, at this time, the relay node B broadcasts a CTS message at a time slot t +1 to complete the code matching process, and if the remaining nodes find that there is no address of the other nodes in the DA field of the CTS message, the node N corresponding to the DA field in the CTS message is confirmed to wait for silence according to the duration in the CTS messagekAnd the node i sends the data frame to the relay node B in the t +2 time slot.
2. Data transmission phase
The invention provides a cache information assistance-based high-coding-opportunity bidirectional access method, which mainly relates to data transmission and updates a virtual cache region through an ACK message feedback mechanism in a data transmission stage. The method comprises the following specific steps:
after code matching is carried out in the step 1, the relay node adds the code matching node to the CTS message for broadcasting, and then receives two code matching nodes i and N of the CTS messagekThen sending respective data frame to relay node j at the same time, node j carrying out physical layer network coding on the two received data, and then sending to nodes i and NkAnd if the rest nodes find that the DA field of the CTS message has no own address, the rest nodes wait in a silent mode according to the duration time in the CTS message.
Step 2 nodes i and NkAfter receiving the encoded data frame, the nodes i and N can effectively decode the original data frame required by the node according to the own data frame and the encoded framekAnd replying an ACK message to the relay node j respectively, wherein the DNAP field of the ACK message contains the information that the N pieces of cache data correspond to the destination IDs, and the relay node and other nodes update the virtual cache region thereof immediately after receiving the ACK message.
And 3, after the data frame is transmitted, continuing to transmit the next data frame.
(III) advantageous effects of the invention
The invention has the advantages that the coding opportunity can be better improved by utilizing the cache information, so that the network coding technology is fully utilized, the total transmission times of data frames are reduced, the information quantity transmitted in unit time slot is increased, the network throughput is improved, and particularly, the invention aims at the scene of a two-hop relay network; secondly, the effect of effectively improving the coding opportunity can be achieved by reducing the handshake times, the control overhead is greatly reduced, and the specific advantages are as follows:
1. increasing network throughput
After the novel mechanism of 'cache information assisting and improving coding opportunity' is adopted, the relay node can better perform coding matching of the node by fully utilizing the cached auxiliary information, compared with the existing bidirectional access method based on network coding, the method can perform confirmation of coding matching without extra overhead, increases coding opportunity, and increases the number of data frames transmitted in unit time slot, thereby increasing network throughput.
2. Reducing end-to-end delay of data frames
After the new mechanism of replacing four-way handshake with two-way handshake is adopted, in the process that each node has a data transmission reservation channel, the coding opportunity is replaced by two-way handshake, compared with the original four-way handshake, the coding opportunity is further improved through the existing two-way handshake, the overhead of the two-way handshake is reduced, the coding opportunity is increased, the number of data frames transmitted in a unit time slot is increased, and therefore the network throughput is increased.
Drawings
Fig. 1 is a network model diagram corresponding to a two-hop relay network.
FIG. 2 is a diagram illustrating an example frame format of an RTS message
Fig. 3 is a diagram illustrating an example frame format of a CTS message
Fig. 4 is a diagram illustrating an example of a real cache region and a virtual cache region.
FIG. 5 is a diagram illustrating an example frame format of an ACK message
Detailed Description
The invention is suitable for a wireless two-hop bidirectional relay network scene, mainly relates to a code matching stage for sending a control message and a data transmission stage after matching, and mainly introduces a specific implementation mode of the invention from the two stages.
1. Code matching stage
The cache information assisted high coding opportunity bidirectional access method provided by the invention firstly sends an RTS reservation channel when the core operation is that the node has data to send in the code matching stage, and the relay node carries the target ID number of N data in the current cache region according to the RTS message, so that the network coding technology can be fully utilized. When a network is initialized, nodes send HELLO messages to confirm neighbor nodes, and route information is constructed through the messages, each node can be a source node, a destination node or a relay node, so that each node has two buffer areas, namely a virtual buffer area and an actual buffer area, when the node generates data to be sent, the node sends an RTS reservation channel to become the source node, and other nodes do not try to send the RTS messages again after receiving the RTS messages; the invention mainly aims at a two-hop relay network scene, and mainly comprises the following steps in a coding matching stage:
step 1, when the network is initialized, the node firstly acquires the neighbor node information through the HELLO message, and can establish a routing table through the message and establish an index ID number mapped as a destination address. Now, only a two-hop relay network scene is taken as a research object, and a network model diagram constructed by the scene is shown in fig. 1.
Step 2, in the t time slot, a certain node i has dataWhen sending, it will broadcast RTS message, after receiving RTS message, some relay node j will extract the ID number corresponding to its DNAP field, and combine the address information of RTS message to effectively update the virtual buffer area, then detect whether there is node N in the virtual buffer areak(k is 1,2,3.. n.) there are also data frames to be sent to the node i, if yes, the step 3 is carried out; otherwise, if the message does not exist, the relay node j replies a CTS message in the t +1 time slot, the AD field content corresponding to the message is empty, after the node i caches the CTS message, the node i directly sends the data to be sent to the relay node j, and the node j forwards the data to the destination node corresponding to the data frame.
Step 3 at this time, there may exist a situation that a plurality of nodes all have data frames to be sent to the node i, and the code matching is satisfied, if there is only one node N1If the code matching is satisfied, the relay node j connects the node i with the node N1Is added into AD1 and AD2 of the AD field of the CTS message, and is broadcast and transmitted in the t +1 time slot, and the node N1And after receiving the CTS message, the node i immediately sends the data frame required to be sent to the relay node j in the t +2 time slot. If not only one node NkIf code matching is satisfied, step 4 is entered.
Step 4, the relay node j according to the node N in the virtual cache regionkThe number of data frames and the number of hops in the CTS message determine which node to select as the code matching node, as shown in fig. 4, at this time, the node C, E, F, G, H has data to the node a, but only the nodes C and F satisfying two hops, and at this time, the nodes C and F have 5 and 4 data to the node a, respectively, so that the node C with a larger number of data frames is selected as the code matching node, at this time, the relay node B broadcasts a CTS message at a time slot t +1 to complete the code matching process, and if the remaining nodes find that there is no address of the other nodes in the DA field of the CTS message, the node N corresponding to the DA field in the CTS message is confirmed to wait for silence according to the duration in the CTS messagekAnd the node i sends the data frame to the relay node B in the t +2 time slot.
2. Data transmission phase
The main operation idea of the cache information assistance-based high-coding-opportunity bidirectional access method in the data transmission stage is that the code matching node firstly sends a data frame to the relay node, the relay node then sends the data frame to the code matching node by using a physical layer network coding technology, then the two code matching nodes reply an ACK message, and at the moment, the relay node can further update a virtual cache region according to the ACK message, so that the next data transmission is facilitated. The method comprises the following specific steps:
after code matching is carried out in the step 1, the relay node adds the code matching node to the CTS message for broadcasting, and then receives two code matching nodes i and N of the CTS messagekThen sending respective data frame to relay node j at the same time, node j carrying out physical layer network coding on the two received data, and then sending to nodes i and NkAnd if the rest nodes find that the DA field of the CTS message has no own address, the rest nodes wait in a silent mode according to the duration time in the CTS message.
Step 2 nodes i and NkAfter receiving the encoded data frame, the nodes i and N can effectively decode the original data frame required by the node according to the own data frame and the encoded framekAnd replying an ACK message to the relay node j respectively, wherein the DNAP field of the ACK message contains the information that the N pieces of cache data correspond to the destination IDs, and the relay node and other nodes update the virtual cache region thereof immediately after receiving the ACK message.
And 3, after the data frame is transmitted, continuing to transmit the next data frame.

Claims (1)

1. A high coding opportunity bidirectional access method based on cache information assistance is applied to a two-hop relay network, and is characterized in that: each node can be a source node, a relay node or a destination node and comprises a code matching stage for sending a control message and a data transmission stage after matching; in the code matching stage, code matching is performed on data frames according to RTS/CTS control messages sent between nodes, if network coding operation can be performed between a source node A and a destination node B through a relay node, if the destination node B does not send data to the source node, the relay node can still perform more efficient code matching to another destination node C according to the information of a virtual buffer area, and data exchange after network coding is completed between the source node A and the destination node C is preferentially performed; if a plurality of destination nodes and a source node A have data exchange, the relay node preferentially selects 2 hops and carries out code matching with a destination node D with the most data exchange with the source node A according to the information of a virtual cache region, and through the two modes, the relay node can find out a code matching node, then the relay node can put the address index ID of the source node A and the index ID of the destination node C or the destination node B into a CTS message, and then replies the CTS message; in the data transmission stage, a source node a and a destination node C or a destination node D send data frames to a relay node, the relay node exchanges data efficiently through a network coding technology, and each node updates cache information of the node, including a virtual cache region, effectively each time according to a received RTS frame and a replied ACK frame;
the method comprises the steps that four-way handshaking is replaced by a two-way handshaking new mechanism, a virtual cache information auxiliary encoding opportunity improvement new mechanism and a virtual cache updating new mechanism is realized by modifying a frame format, wherein the four-way handshaking is replaced by the two-way handshaking new mechanism and the virtual cache information auxiliary encoding opportunity improvement new mechanism works in an encoding matching stage, and the virtual cache updating new mechanism works in a data transmission stage by modifying the frame format;
the new mechanism for replacing four-way handshake with two-way handshake comprises that when a source node A sends data, the source node A sends a revised RTS request message, wherein the message carries a DANP field which stores destination index ID numbers corresponding to N data frames to be sent; after receiving the revised RTS request message, the relay node updates the virtual buffer area, and the relay node can obtain the index ID corresponding to the destination of each data frame of the source node through the DNAP field, so that code matching can be performed according to the information of the virtual buffer area, and when data exchange between the source node and the destination node of the source node is obtained, the relay node adds the addresses of the source node and the destination node of the source node to the revised CTS message and broadcasts the revised CTS message;
the new mechanism for improving coding opportunity assisted by cache information comprises that when a source node has data to send, the source node sends the revised RTS request message, at a certain time t, when the relay node obtains virtual cache information of at least one neighbor node data, the relay node can determine that the neighbor node carries out data exchange transmission, namely, 2 hops are preferentially selected and code matching is carried out on a destination node D which has the most data exchange with the source node A, and then the relay node adds an address of the source node A and an address of the destination node D which need to send data to the revised CTS message at the next time and then broadcasts and sends the revised CTS message;
the new mechanism for updating the virtual buffer by modifying the frame format comprises the steps of respectively adding a field DANP in the frame formats of an RTS message and an ACK message to form the modified RTS message and the modified ACK message, wherein the field DANP is used for storing a destination index ID of the source node data; and respectively changing the FA field and the PA field in the CTS message, and realizing the purpose of not increasing overhead by changing the FA field and the PA field into a mode of storing the address1 of the source node and the address2 of the destination node, wherein the relay node can effectively update a virtual cache area in real time according to the received revised RTS and ACK messages, and when data exchange can be performed without finding a node according to the virtual cache information, namely when data exchange exists without finding the matched source node, the relay node sets the address1 of the source node and the address2 of the destination node to be null when sending CTS, and then relays transmission through the relay node in a multi-hop manner.
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