CN111526603A - Multi-channel multi-address access method for wireless ad hoc network - Google Patents

Abstract

The invention discloses a multi-channel multi-access method for a wireless ad hoc network, wherein a transmitting/receiving channel of each node of the wireless ad hoc network can work at one of a plurality of mutually orthogonal frequencies and can be switched among the mutually orthogonal frequencies, and a set formed by the mutually orthogonal frequencies is known and shared in the whole network; the method reduces the overhead of the control frame by initiating handshake by the receiver, and respectively transmits the control frame and the data frame by using different channels. The method has the characteristics of portability and flexibility in networking, and does not need the synchronization of the whole network clock in a distributed and centerless wireless ad hoc network; the receiver initiates handshake to reduce the overhead of control frame, and uses different channels to transmit control frame and data frame, to improve the time utilization of channel; the collision probability can be found and reduced, and the spatial multiplexing degree of the channel can be increased. These mechanisms allow the network to maintain higher throughput at higher traffic volumes.

Description

A kind of multi-channel multiple access method for wireless ad hoc network

technical field

The present invention relates to the technical field of wireless communication, in particular to a multi-channel multiple access method suitable for wireless ad hoc networks, a method applied to non-centralized and distributed wireless ad hoc networks, using multiple A method for implementing multiple access using separate channels.

Background technique

Wireless ad hoc network (also known as Ad Hoc network) is a multi-hop, centerless, self-organizing wireless network. The network is based on algorithms such as MAC (media access control) and routing control, which can quickly adapt to the dynamic topology changes of the network. (node movement, link interference and blocking), it is suitable for communication application environments where bandwidth is limited (node's packet processing capability, link capacity is low) and power is limited (miniaturized node equipment).

IEEE 802.11DCF is a wireless ad hoc network single-channel access technology developed on the basis of wireless local area network standards. The technology is based on the random access strategy with the carrier sensing (CSMA/CA: Carrier Sensing Multiple Access/Collision Avoid) mechanism, which greatly reduces the utilization of the channel while reducing the probability of collision. Proved difficult to meet high-traffic application scenarios.

Compared with the RTS-CTS-DATA-ACK three-way handshake mechanism initiated by the sender in IEEE 802.11DCF, the MACA-BI protocol is a MAC protocol initiated by the receiver. It omits RTS, retains CTS, and changes it to RTR (Ready to Receive), which increases the time utilization of the channel by reducing the number of handshakes, but brings problems of hidden terminals and exposed terminals, and increases the probability of network conflict.

Note: A "multi-hop network" is constructed of nodes, including devices such as computers and mobile phones, all wirelessly connected to each other, which can then forward data to each other over the network. Data hops from node to node until it reaches its destination. Data is always available unless all nodes fail, making this network topology reliable and scalable.

DBTMA is a channel access protocol based on dual channel plus busy tone channel. In DBTMA, the channel is divided into control channel and data channel, RTS and CTS control messages are transmitted on the control channel, data messages are transmitted on the data channel, and there are two out-of-band busy tones with different frequencies: send busy tone and Receive busy tone. Multi-channel improves the network throughput, but also brings the problem of multi-channel hidden terminals and exposed terminals. The space utilization of channels is not high, and the transmission and detection of two out-of-band busy tone signals require additional hardware support.

SUMMARY OF THE INVENTION

The technical problems to be solved by the present invention are: the multi-channel improves the network throughput rate, but also brings the problems of multi-channel hidden terminals and exposed terminals, the space utilization rate of the channels is not high, and the transmission and detection of two out-of-band busy tone signals require Additional hardware support; MACA-BI protocol brings hidden terminal and exposed terminal problems, and the problem of increased probability of network conflict.

In view of the above problems, the present invention provides a multi-channel multiple access method suitable for wireless ad hoc networks. The wireless ad hoc network method is particularly suitable for application scenarios of industrial Internet of Things or industrial sensor networks, and is suitable for distributed wireless ad hoc networks and Internet of Things with high traffic volume or low transmission rate. In this application mode, nodes generally work in half-duplex mode, each node has one send/receive channel, and the network traffic volume is relatively constant, and the network traffic volume is relatively large compared to the node's data processing capability and bandwidth limitations. Based on the above characteristics, through the targeted design of the network multiple access control method, the access performance such as the network throughput rate is improved.

The technical scheme adopted in the present invention is:

A multi-channel multiple access method for a wireless ad hoc network, wherein the transmit/receive channel of each node of the wireless ad hoc network can work at a certain frequency among a plurality of mutually orthogonal frequencies, and can These mutually orthogonal frequencies are switched, and the set of these mutually orthogonal frequencies is known and shared by the entire network;

The method reduces the overhead of the control frame by initiating a handshake by the receiver, uses different channels to transmit the control frame and the data frame respectively, and increases the time utilization rate of the channel.

The implementation process of the method also includes the following contents:

The RTR control frame, ACK control frame, NTR control frame and DATA data frame of the wireless ad hoc network are transmitted on different channels respectively;

The destination node of the wireless ad hoc network uses the RTR control frame to initiate data transmission, and uses the NTR control frame as needed to alleviate transmission conflicts;

The source node uses the DATA data frame to send data, and the destination node uses the ACK control frame to confirm the successful data transmission.

The wireless ad hoc network includes 3 channels, namely the master control channel C _mc , the slave control channel C _sc , and the data channel C _d ; the channels of the wireless ad hoc network are mutually orthogonal in frequency and have a certain bandwidth, The message can be transmitted at the corresponding transmission rate.

The network node of the wireless ad hoc network controls the node's reception and transmission respectively by maintaining two NAVs (Network Allocation Vectors), so as to discover and reduce the collision probability and increase the spatial multiplexing degree of the channel.

The RTR (Ready to Receive) control frame contains information such as source node address, destination node address, and current value of NAV of the destination point, and is transmitted on the main control channel C _mc to notify the data sender to send data.

The NTR (No Transmission Request) control frame includes the source node address, destination node address, and current value information of the destination node NAV. It does not have to include a specific frame structure. It can be a busy tone with the same frequency as the carrier frequency, as long as the receiver can Accumulate enough signal energy to correctly judge the existence of the signal; NTR is transmitted from the control channel C _sc channel, the function is to terminate the transmission in time when the risk of transmission collision is high.

The ACK (Acknowledgement) control frame includes source node address, destination node address, and destination node NAV current value information, and is transmitted on the main control channel C _mc channel to notify the data sender that the data has been correctly received.

The DATA data frame is transmitted on the data channel _Cd , and the function is to carry service data.

The NAV (Network Allocation Vector, Network Allocation Vector) sets a timer with a time length value, and when the timer times out, a prompt is sent to the network node using the method to drive the node to respond accordingly; the method includes 2 NAVs, namely NAV _N-RTR (No-RTR-transmission) and NAV _N-DATA (No-DATA-transmission);

At each reset, set NAV _N-DATA = 2τ+ξ+δ+γ, where ξ is the time required by the carrier detection circuit from the start of detection to the confirmation of the detection of the carrier; δ is the DATA frame sending delay; γ is the RTR , NTR, ACK frame sending delay, by setting the NAV _N-DATA to be the maximum time length sufficient to complete a transmission between the current source node and the destination node;

Set NAV _N-RTR = δ+2τ-ξ (ie, the maximum remaining time of ongoing transmission), RTR is not allowed to be sent before NAV _N-RTR times out, and DATA is not allowed to be sent before NAV _N-DATA times out.

The implementation process of the method includes the following contents:

1) Node initialization

Step 1: The node first monitors C _mc for 2τ seconds in the initialization phase, does not send signals during this period, and monitors the channel, so that the node can discover the usage of the channel, τ is the maximum signal propagation delay between the two nodes; the node is normal Enter the Passive state after initialization;

2) The node is in Passive state

Step 1: Check if NAV _N-RTR is 0;

Step 2: If NAV _N-RTR is not 0, continue monitoring; if NAV _N-RTR is 0, set the timer TTX time to a random number in (0, T _s ), where T _s is the average channel access time;

Step 3: The node monitors C _mc before the TTX times out;

Step 4-1: If the carrier is monitored, the node starts to back off, receives and parses the received message; if the carrier is not monitored, go to step 5;

Step 4-2: If the RTR sent to other nodes is received, the node resets the NAV _N-DATA . During this time period, the node can still reset the TTX and send an RTR invitation; if it receives an ACK, The node directly discards this frame; if the received frame cannot be correctly parsed due to interference, the node still updates the NAV _N-DATA ;

Step 5: If the carrier is not detected on the C _mc before the TTX times out, the node sends its own RTR on the C _mc , and the node enters the receiving state;

4) The node is in the DATA receiving state, which is called the destination node; when the node sends RTR, it enters the DATA receiving state:

Step 1: After the destination node sends an RTR, it transfers to the C _d channel to monitor a period of time with a length of ξ;

Step 2-1: If C _d is idle within the duration ξ, continue to keep the monitoring state until the DATA of the source node is completely received; if the carrier on C _d is detected within the duration ξ, go to step 3;

Step 2-2: If the DATA is correct, go to C _mc to send ACK to end the transmission, and set NAV _N-DATA ; if the DATA is wrong, go to C _mc without sending ACK, set NAV _N-DATA and start the restart. Transmission mechanism; the retransmission mechanism described in the method of the present invention may be similar to the retransmission mechanism in IEEE 802.11 DCF.

Step 3: If the carrier on C _d is detected within ξ, then go to C _sc to send NTR, and the source node is listening on C _sc at this time; after sending NTR, the destination node goes to the main control channel and sets the NAV _N-RTR , return to the Passive state; if the destination node waits on C _d for more than 2τ+ξ and has not received DATA, it also returns to the Passive state;

5) The node is in the DATA sending state, called the source node; when the node receives the RTR, it enters the DATA sending state:

Step 1: If the node in Passive state correctly receives the RTR sent to itself, judge whether its NAV _N-DATA is 0;

Step 2-1: If its NAV _N-DATA is 0, go to C _sc to monitor for a period of time ξ; if its NAV _N-DATA is not 0, go to step 3;

Step 2-2: If NTR is received within the time period ξ, go to the main control channel C _mc and re-enter the Passive state; if no NTR is received, go to C _d and start sending DATA;

Step 2-3: After the DATA transmission is completed, go to the C _mc and wait to receive ACK;

Step 2-4: If the ACK sent by the destination node is received, it is judged that the transmission is successful, re-enter the Passive state and end the transmission; if the correct ACK is not received, it is considered that the data frame transmission failed, and the Passive state is entered and the transmission is terminated. prepare for retransmission;

Step 3: If the NAV _N-DATA of the source node is not 0, the destination node discards the RTR sent to itself and continues to stay on C _mc ; in this case, the destination node is on C _d within the (ξ+2τ) time period If the DATA cannot be waited, it is judged that the transmission fails, the transmission is ended and the Passive state is entered.

6) The condition for resetting NAV _N-DATA is to receive an incorrect RTR or ACK, the destination node is not its own RTR, or after receiving a DATA frame; the condition for resetting NAV _N-RTR is after NTR is sent; NAV _N-DATA and NAV _N-RTR are set separately to control transmission and reception respectively.

The method of the invention solves the multi-channel hidden terminal problem by relying on two mechanisms of NTR frame and NAV _N-DATA /NAV _N-RTR , and on this basis, encourages parallel transmission and improves the spatial multiplexing degree of the channel.

The beneficial effects of the present invention are:

The method of the invention has the characteristics of light and flexible networking, and in a distributed and non-central wireless ad hoc network, there is no need to synchronize the clocks of the entire network; the network nodes work in half-duplex mode, and each network node has one send/receive channel, and the frequency of the send/receive channel can be switched at several mutually orthogonal frequency points. The receiver initiates a handshake to reduce the control frame overhead, and use different channels to transmit control frames and data frames respectively, increasing the number of channels. Introduce a kind of NTR control frame, and control the node's receiving and sending timing by maintaining 2 NAVs (Network Allocation Vector) respectively, in order to find and reduce the collision probability, and increase the spatial multiplexing degree of the channel. These mechanisms allow the network to maintain high throughput rates under higher traffic volumes.

Description of drawings

Fig. 1 is the signal control schematic diagram of the present invention;

FIG. 2 is a schematic diagram of the implementation flow of the present invention.

Detailed ways

The method of the present invention can be implemented by firmware in the wireless network card, or in the driver of the wireless network card. Below in conjunction with the accompanying drawings of the description, the present invention is further described according to specific embodiments:

Example 2

As shown in FIG. 2, a multi-channel multiple access method for wireless ad hoc network, the implementation process of the method includes the following contents:

1) Node initialization

Step 1: The node first monitors C _mc for 2τ seconds in the initialization phase, does not send signals during this period, and monitors the channel, so that the node can discover the usage of the channel, τ is the maximum signal propagation delay between the two nodes; the node is normal Enter the Passive state after initialization;

2) The node is in Passive state

Step 1: Check if NAV _N-RTR is 0;

Step 2: If NAV _N-RTR is not 0, continue monitoring; if NAV _N-RTR is 0, set the timer TTX time to a random number in (0, T _s ), where T _s is the average channel access time;

Step 3: The node monitors C _mc before the TTX times out;

Step 4-1: If the carrier is monitored, the node starts to back off, receives and parses the received message; if the carrier is not monitored, go to step 5;

Step 4-2: If the RTR sent to other nodes is received, the node resets the NAV _N-DATA . During this time period, the node can still reset the TTX and send an RTR invitation; if it receives an ACK, The node directly discards this frame; if the received frame cannot be correctly parsed due to interference, the node still updates the NAV _N-DATA ;

Step 5: If the carrier is not detected on the C _mc before the TTX times out, the node sends its own RTR on the C _mc , and the node enters the receiving state;

4) The node is in the DATA receiving state, which is called the destination node; when the node sends RTR, it enters the DATA receiving state:

Step 1: After the destination node sends an RTR, it transfers to the C _d channel to monitor a period of time with a length of ξ;

Step 2-1: If C _d is idle within the duration ξ, continue to keep the monitoring state until the DATA of the source node is completely received; if the carrier on C _d is detected within the duration ξ, go to Step 3;

Step 2-2: If the DATA is correct, go to C _mc to send ACK to end the transmission, and set NAV _N-DATA ; if the DATA is wrong, go to C _mc without sending ACK, set NAV _N-DATA and start the restart. Transmission mechanism; the retransmission mechanism described in the method of the present invention may be similar to the retransmission mechanism in IEEE 802.11 DCF.

Step 3: If the carrier on C _d is detected within ξ, then go to C _sc to send NTR, and the source node is listening on C _sc at this time; after sending NTR, the destination node goes to the main control channel and sets the NAV _N-RTR , return to the Passive state; if the destination node waits on C _d for more than 2τ+ξ and has not received DATA, it also returns to the Passive state;

5) The node is in the DATA sending state, called the source node; when the node receives the RTR, it enters the DATA sending state:

Step 1: If the node in Passive state correctly receives the RTR sent to itself, judge whether its NAV _N-DATA is 0;

Step 2-1: If its NAV _N-DATA is 0, go to C _sc to monitor for a period of time ξ; if its NAV _N-DATA is not 0, go to step 3;

Step 2-2: If NTR is received within the time period ξ, go to the main control channel C _mc and re-enter the Passive state; if no NTR is received, go to C _d and start sending DATA;

Step 2-3: After the DATA transmission is completed, go to the C _mc and wait to receive ACK;

Step 2-4: If the ACK sent by the destination node is received, it is judged that the transmission is successful, re-enter the Passive state and end the transmission; if the correct ACK is not received, it is considered that the data frame transmission failed, and the Passive state is entered and the transmission is terminated. prepare for retransmission;

Step 3: If the NAV _N-DATA of the source node is not 0, the destination node discards the RTR sent to itself and continues to stay on C _mc ; in this case, the destination node is on C _d within the (ξ+2τ) time period If the DATA cannot be waited, it is judged that the transmission fails, the transmission is ended and the Passive state is entered.

The condition for resetting NAV _N-DATA is to receive an incorrect RTR or ACK, the destination node is not its own RTR, or after receiving a DATA frame; the condition for resetting NAV _N-RTR is after NTR is sent; NAV _{N- DATA} and NAV _N-RTR are set separately to control transmission and reception respectively.

Example 2

As shown in Figure 1, it is assumed that nodes A and B, B and A and C, C and B and D, and D and C are adjacent nodes. In the initial state, the NAV _N-DATA and NAV _N-RTR of each node are both 0.

Node A monitors TTX on C _mc for a specified period of time and no carrier is detected, and considers that the channel is idle, sends RTR to node B and is successfully received by node B, and node A switches to C _d to monitor and wait to receive DATA frames. Since the neighboring nodes A and C of B do not occupy C _d at this time, after B monitors the C _sc channel for a length of ξ, it transfers to C _d to send a DATA frame and then transfers to C _mc to monitor. This DATA frame is correctly received by node A, node A sends ACK on C _mc and is received by node B, and a data transmission is completed.

During the communication between node A and node B, node C that monitors C _mc for a period of time thinks that C _d is idle, so it sends an RTR to node D on C _mc and is correctly received by node D, and node D turns to C _sc to start monitoring, At the same time, node C goes to monitor on C _d . At this time, node C will monitor the data sent by node B on C _d and know that C _d is occupied. Therefore, node C goes to C _sc to send NTR and set its own NAV _{N- RTR} , NTR will be received by node D within the time period ξ, so that node D will not transmit data, the data transmission between nodes C and D is terminated, avoiding collision with the data transmission between node A and node B .

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims (10)

1. A multi-channel multiple access method for a wireless ad hoc network is characterized in that a transmitting/receiving channel of each node of the wireless ad hoc network can work at one of a plurality of mutually orthogonal frequencies and can be switched among the mutually orthogonal frequencies, and a set formed by the mutually orthogonal frequencies is known and shared in the whole network;

the method reduces the overhead of the control frame by initiating handshake by the receiver, and respectively transmits the control frame and the data frame by using different channels.

2. The method of claim 1, wherein the implementation of the method further comprises the following steps:

the wireless ad hoc network respectively transmits an RTR control frame, an ACK control frame, an NTR control frame and a DATA DATA frame on different channels;

a target node of the wireless ad hoc network initiates data transmission by using an RTR control frame, and uses an NTR control frame as required to relieve transmission conflict;

and the source node of the wireless ad hoc network sends DATA by using the DATA DATA frame, and the destination node confirms that the DATA transmission is successful by using the ACK control frame.

3. The method of claim 2, wherein the ad hoc network comprises 3 channels, each of which is a master control channel C_mcFrom the control channel C_scData channel C_d(ii) a The channels of the wireless ad hoc network are mutually orthogonal in frequency, have certain bandwidth and can transmit messages at corresponding transmission rate.

4. A method according to claim 3, wherein the network nodes of the wireless ad hoc network control the reception and transmission of the nodes, respectively, by maintaining two NAVs.

5. The method of claim 4, wherein the RTR control frame comprises a source node address, a destination NAV current value information, and is in a main control channel C_mcAnd the upper transmission is used for informing the data sender to send the data.

6. The multi-channel multiple access method for wireless ad hoc networks according to claim 5, wherein the NTR control frame contains source node address, destination node NAV current value information, so that the receiver can accumulate enough signal energy to correctly judge the existence of signal; NTR in slave control channel C_scAnd transmitting on the channel, wherein the transmission is stopped in time when the transmission collision risk is high.

7. A method for wireless ad hoc network according to claim 6The multi-channel multi-access method is characterized in that the ACK control frame comprises a source node address, a destination node address and destination node NAV current value information, and the ACK control frame is arranged in a main control channel C_mcAnd the transmission on the channel is used for informing the data sender that the data is correctly received.

8. The method of claim 7, wherein the DATA DATA frame is characterized in a DATA channel C_dAnd the function of the uplink transmission is to carry service data.

9. The method of claim 8, wherein the NAV is configured to set a timer of a time length value, and when the timer expires, to prompt a network node using the method to drive the node to respond accordingly; the method comprises 2 NAVs, respectively NAV_N-RTRAnd NAV_N-DATA；

Setting NAV at each reset_N-DATA2 τ + ξ + + γ, where ξ is the time required for the carrier detect circuit to detect the carrier from the start, the DATA frame transmission delay, γ is RTR, NTR, ACK frame transmission delay, and the NAV is set by setting_N-DATAA maximum length of time sufficient to complete a transmission between the current source node and the destination node;

setting NAV_N-RTRAt NAV, +2 τ - ξ_N-RTRNot allowing RTR to be sent before timeout, at NAV_N-DATADATA is not allowed to be sent before a timeout.

10. The method of claim 9, wherein the method is implemented by the following steps:

1) node initialization

Step 1: the node firstly listens for C in the initialization phase_mc2 tau seconds, during which no signal is transmitted and the channel is monitored so that the node finds out the use of the channel, tau being the maximum between two nodesA signal propagation delay; after the node is initialized normally, entering a Passive state;

2) the node is in the Passive state

Step 1: checking for NAV_N-RTRWhether or not it is 0;

step 2: if NAV_N-RTRIf not, continuing monitoring; if NAV_N-RTRTo be 0, the timer TTX time is set to be (0, T)_s) Inner one random number, T_sIs the average channel access time;

and step 3: node snooping C before TTX timeout_mc；

Step 4-1: if the carrier is monitored, the node starts to retreat and receives and analyzes the received message; if the carrier is not monitored, turning to the step 5;

step 4-2: if an RTR is received that is sent to another node, the node resets the NAV_N-DATADuring this period, the node can still reset the TTX and issue an RTR invitation; if the received ACK is ACK, the node directly discards the frame; if the received frame cannot be correctly resolved due to interference, the node still updates the NAV_N-DATA；

And 5: if TTX is not timed out before C_mcOn detected carrier, node is in C_mcSending the RTR of the node, and enabling the node to enter a receiving state;

4) the node is in a DATA receiving state and is called a destination node; after the node sends RTR, entering a DATA receiving state:

step 1: after sending RTR, destination node turns to C_dA period of ξ channel listening length;

step 2-1 if C is within duration ξ_dIdle, then continue listening until the source node's DATA is completely received, if C is detected within duration ξ_dThe carrier wave is transmitted to the step 3;

step 2-2: if DATA is error-free, go to C_mcSending ACK to end the transmission and setting NAV_N-DATA(ii) a If DATA is incorrect, go to C_mcNot sending ACK after last, setting NAV_N-DATAAnd starting a retransmission mechanism;

step 3 if C is detected in ξ_dCarrier wave on, then go to C_scUp sending NTR, when the source node is in C_scUpper monitoring; after transmitting NTR, the destination node transfers to the main control channel and sets NAV_N-RTRReturning to the Passive state again; if the destination node is at C_dIf the waiting time exceeds 2 tau + ξ, the DATA is not received yet, and the PASSIVE state is returned again;

5) the node is in a DATA sending state and is called as a source node; after receiving the RTR, the node enters a DATA sending state:

step 1: if the node in Passive state correctly receives the RTR sent to the node, the NAV of the node is judged_N-DATAWhether or not it is 0;

step 2-1: if it is NAV_N-DATA0, then go to C_scListen for a period of time ξ, if it is NAV_N-DATAIf not, turning to the step 3;

step 2-if NTR is received within time period ξ, go to Primary control channel C_mcRe-entering the Passive state; if NTR is not received, go to C_dAnd starts sending DATA;

step 2-3: after DATA transmission is complete, go to C_mcWaiting for receiving ACK;

step 2-4: if the ACK sent by the destination node is received, the transmission is judged to be successful, the Passive state is re-entered, and the transmission is ended; if the correct ACK is not received, the data frame transmission is considered to be failed, and the Passive state is entered and retransmission is prepared;

and step 3: if the NAV of the source node_N-DATAIf not, the destination node discards the RTR sent to the destination node and continues to remain in C_mcThe above step (1); in this case the destination node is at C_dIf the DATA is not obtained in the upper (ξ +2 τ) time period, the transmission is judged to fail, and the transmission is ended and the Passive state is entered.

6) Resetting the NAV_N-DATAThe condition is that an error RTR or ACK is received, the received target node is not the RTR of the target node or the received DATA frame is finished; resetting the NAV_N-RTRProvided that after the NTR is sent; NAV_N-DATAAnd NAV_N-RTRThe setting is separated, and the transmission and the reception are controlled respectively.

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