CN111212462B

CN111212462B - On-demand awakening multi-address access method of underwater network

Info

Publication number: CN111212462B
Application number: CN201911387175.1A
Authority: CN
Inventors: 赵瑞琴; 赵月瑶
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2021-09-17
Anticipated expiration: 2039-12-30
Also published as: CN111212462A

Abstract

The invention provides an on-demand awakening multiple access method for an underwater network. Transmitting WU packet directional awakening target nodes by using TR, announcing that the communication starts and channel information is updated through broadcasting ACK, and preventing other nodes from transmitting information to the pair of transceiving nodes; and then, the TR is used for sending the DATA packet and the reply ACKD packet, the probability of successful DATA sending is improved, the interference to other nodes is reduced, the CHANNEL information is updated again by broadcasting the CHANNEL packet after the communication is finished so as to ensure the accuracy of the TR, and all the neighbor nodes are informed that the communication is finished. The reduction of the signal length can greatly reduce the transmitting energy consumption of the node, thereby effectively utilizing energy, improving the network throughput and the energy utilization rate, reducing the energy consumption for receiving invalid information, improving the energy utilization rate of the node, realizing the simultaneous information interaction of a plurality of pairs of communication nodes, and improving the channel utilization rate.

Description

On-demand awakening multi-address access method of underwater network

Technical Field

The invention relates to the technical field of underwater networks, in particular to a network node MAC access method for realizing high efficiency and energy saving underwater, which is suitable for underwater network networking with a node dormancy mode.

Background

Abundant resources are stored in the ocean, and the underwater acoustic sensor network has important application in the aspects of ocean military defense, underwater target search, ocean resource exploration, ocean environment monitoring and the like. However, most network nodes in the marine environment are powered by batteries and are difficult to replace or supplement power supplies, so that the energy consumption of the nodes is reduced, and the life cycle of the whole network is prolonged, which is difficult to realize the networking of the underwater acoustic sensor. Aiming at the problem, the dormancy awakening technology of the node can be utilized to increase the dormancy time of the node as much as possible, so that the purposes of reducing the energy consumption of the node and prolonging the network life cycle are achieved.

The wake-up dormancy technology of the network node comprehensively considers the physical layer and the MAC access method of the node. In terms of the MAC layer, the wake-on-sleep mechanism of the protocol can be divided into two categories, i.e., wake-on-demand and wake-on-demand, wherein the protocols requiring wake-on include two broad categories, i.e., wake-on-cycle and wake-on-demand.

For the MAC access method without waking up, the nodes are required to keep time synchronization, periodically sleep and wake up, and the nodes finish communication at the wake-up time, so the sleep strategy of the protocols is fixed. The MAC access method based on awakening-free has the advantages that the data conflict can be well avoided by designing the sleep time table of the nodes, and reasonable throughput is kept. However, this protocol also has significant drawbacks: the nodes adopt their own scheduling tables to switch between active and dormant states, so that precise time synchronization needs to be maintained, and the synchronization overhead is not inconstant. Also, the fixed wake-on-sleep strategy results in a protocol that does not adapt well to changes in network traffic.

The MAC access method based on the cycle dormancy awakening mechanism allows dormancy time tables of all nodes to be different, so that the time synchronization overhead can be reduced, but when data needs to be transmitted between the nodes, a sending node needs to firstly transmit an awakening signal to awaken a receiving node, and then the data is sent to complete communication. The wake-up signal needs to keep the length of a sleep cycle to ensure that the wake-up signal is accurately received by a receiving node, the longer wake-up signal causes the increase of end-to-end time delay and the waste of emission energy consumption in an underwater acoustic environment, and simultaneously, a large amount of preamble information is sent to cause the increase of channel pressure, thereby reducing the overall utilization rate of a channel.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides an on-demand awakening multiple access method of an underwater network. In order to solve the problem that the energy utilization rate and the channel utilization rate are low in the existing MAC access method, the invention provides an efficient and energy-saving underwater acoustic sensor network MAC access method, which enables network nodes to prolong the service life of the network nodes under the same communication task, can improve the channel utilization rate and avoid data collision.

The technical scheme adopted by the invention for solving the technical problem comprises the following specific steps:

step 1, in the process of awakening MAC access as required, defining the following five packet formats:

1.1, waking up (wake _ up) signal packets, namely WU packets for short, the packet length is only 11 bits, the packets contain ID information of self and receiving nodes, a sending node wakes up the receiving nodes in a dormant state by using the WU packets to transmit data, and the WU packets adopt a directional transmission mode to avoid invalid waking up of other neighbor nodes;

1.2, an acknowledgement packet of the wake-up signal, referred to as an ACK packet for short, is an acknowledgement packet replied to the sending node after the receiving node is successfully awakened, and simultaneously, channel information is obtained for the TR technology and sent to all neighboring nodes, and the communication start is announced, the ACK packet adopts a broadcast transmission mode, the packet length is only 21 bits, the packet contains a WU packet header, ID information of the WU packet header and the receiving node, communication start information and channel information, and the WU packet header is used for awakening all the neighboring nodes in a dormant state to receive the ACK packet;

1.3, a DATA packet, namely a DATA packet for short, with the packet length of 256 bits, wherein the DATA packet comprises ID information of the DATA packet and ID information of a receiving node, DATA packet generation time and DATA information, the DATA packet is DATA to be transmitted by a sending node, the DATA packet adopts a directional transmission mode, and the signal-to-noise ratio at the receiving node is improved by utilizing the space-time focusing property of a TR (transmitter-receiver);

1.4, a DATA confirmation packet, called an ACKD packet for short, with a packet length of 15 bits, containing ID information and DATA confirmation information, and when a receiving node correctly receives the DATA packet, replying the ACKD packet to a sending node to indicate that the DATA is correctly received, and adopting a directional transmission mode;

1.5, a communication end packet, called a CHANNEL packet for short, when a sending node receives an ACKD packet, the sending node sends the CHANNEL packet to inform all nodes that the communication is ended, other nodes communicate with the node at the moment and acquire CHANNEL information to all neighbor nodes again, a broadcast transmission mode is adopted, the packet length is 21 bits, the packet length comprises a WU packet header, address information, communication end information and CHANNEL information, and the WU packet header is used for awakening all the neighbor nodes in a dormant state to receive the CHANNEL packet;

when no communication task exists, all nodes are in a dormant state, the nodes can only be awakened by the WU packet, and after the packet stream is obtained, the packet stream needs to be judged:

i) if the packet is a WU packet, initializing and entering a step 2;

ii) if not a WU packet, re-entering the sleep state;

step 2, judging whether the node belongs to a sending node, a receiving node or a neighbor node:

i) if the WU signal comes from the application layer, the node belongs to a transmitting node, so the node needs to transmit a WU signal to a receiving node by using TR to wake up the WU signal, and then the step 4 is carried out;

ii) if the WU signal comes from the physical layer, the node belongs to a receiving node, the node is converted into an active state, the node is judged to be the receiving node or a neighbor node according to the type of a receiving packet, and then the step 3 is carried out;

step 3, after receiving the packet, the receiving node needs to judge the type of the packet:

i) if only one WU packet exists, the node is a receiving node, the WU packet is processed, the ID of the destination node is confirmed to be the same as the ID of the node, a reply ACK is broadcasted, the sending node is informed to be ready to receive data, and then the step 6 is carried out;

ii) if the ACK packet carries a WU packet, the node is a neighbor node, the received ACK packet is broadcasted by the receiving node and is not sent to the node, and the node enters a dormant state after processing channel information;

iii) if the packet is a CHANNEL packet carrying a WU packet, the node is a neighbor node, receives a notification from a certain sending node, indicates that the communication is completed, and then enters step 7;

step 4, the node is in the state of waiting for ACK at the moment:

i) if the ACK is not received in the two propagation delays and the two transmission delays, the WU signal is sent again after the random backoff is carried out for 0-5s, and the ACK reply is waited;

ii) if receiving ACK, using TR to send DATA to the receiving node, and then entering step 5;

step 5, the node is in a state of waiting for ACKD at the moment;

i) if the ACKD is not received in the two propagation delays and the two transmission delays, the DATA packet is sent again after the random backoff is performed for 0-5s, and the reply of the ACKD is waited;

ii) if the ACKD is received, checking whether the data queue is empty, if not, continuing to transmit the data, and then repeating the step 5; if the queue is empty, broadcasting and sending a CHANNEL packet, informing a receiving node that data is sent completely, simultaneously informing a neighbor node that the communication is finished, and then entering a dormant state;

step 6, the node is in a state of waiting for DATA at the moment;

i) if the DATA is not received in the two propagation delays plus the two transmission delays, the ACK signal is sent again after the random backoff is performed for 0-5s, and the DATA continues to be waited;

ii) if the DATA is received and the information of the DATA packet is determined to be correct, replying the ACKD packet to the sending node by using the TR, and then entering the step 8 to wait for the arrival of subsequent DATA;

step 7, when receiving the CHANNEL packet, reading the field of the CHANNEL packet, and judging whether the packet is sent to the node:

i) if the node is sent to the node, the communication process is finished, and the node enters a dormant state;

ii) if the data is not sent to the node, detecting whether the queue has data, and if the data does not exist, directly entering a dormant state; if the data exists, a WU packet is sent by using the TR, the receiving node is awakened, and then the step 3 is carried out;

step 8, judging whether a DATA packet or a CHANNEL packet is subsequently received:

i) if the received DATA packet is a DATA packet, entering step 6;

ii) if a CHANNEL packet is received, go to step 7.

The invention has the beneficial effects that:

the awakening signal length of the MAC access method awakened as required is extremely short, so that the awakening signal has important significance in the environment that the underwater transmitting energy consumption is far higher than the receiving energy consumption, and the transmitting energy consumption of the node can be greatly reduced by reducing the signal length, so that the energy is effectively utilized, and the service life of the node is prolonged.

The protocol effectively avoids the collision among various signals through reasonable design, thereby reducing the times of data retransmission, improving the network throughput and the energy utilization rate, and having more advantages for implementing multiple access, particularly in the environment with more collisions of an underwater network.

The protocol adopts a time reversal technology to complete directional transmission of the WU and ACKD packets, avoids the problem of excessive interception of neighbor nodes in a network which are not in a communication task, reduces energy consumption for receiving invalid information, and improves the energy utilization rate of the nodes.

The protocol adopts a time reversal technology to transmit the DATA packet, can realize simultaneous information interaction of a plurality of pairs of communication nodes, improves the channel utilization rate, and has necessary value for an underwater network with very limited bandwidth resources.

Drawings

Fig. 1 is a protocol flow diagram of the present invention.

Fig. 2 is a simulation diagram of energy consumption comparison of the present invention.

Fig. 3 is a network node scenario diagram of the present invention.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

The MAC access method of the invention can immediately awaken the nodes in the dormant state as required to transmit data after generating communication tasks at any time according to the flow change of the network, thereby achieving the aim of awakening as required, overcoming the defect of not awakening the MAC access method and well adapting to the change of the network flow. And the network nodes based on the access method do not need to be synchronized, thereby avoiding the synchronization overhead.

The sending node wakes up the receiving node by using the wake-up signal before sending data, and at the moment, the receiving node is in a dormant state and cannot receive the wake-up signal, so that the wake-up signal and noise in a channel can be distinguished by using a node external module, namely a wake-up circuit, and once the wake-up signal and the noise are successfully identified, the receiving node is awakened to carry out communication.

Meanwhile, the access method adopts two transmission modes: based on directional transmission and broadcast transmission of Time Reversal (TR), the time-space focusing of the time reversal technology can realize the transmission of packets to the designated nodes, thereby realizing the transmission of different packet types and improving the utilization rate of channels by avoiding data collision.

The access method utilizes TR to send WU packets to directionally awaken a target node, announces that the communication starts and updates channel information through broadcasting ACK, and other nodes do not send information to the pair of transceiving nodes; and then, the TR is used for sending the DATA packet and the reply ACKD packet, the probability of successful DATA sending is improved, the interference to other nodes is reduced, the CHANNEL information is updated again by broadcasting the CHANNEL packet after the communication is finished so as to ensure the accuracy of the TR, and all the neighbor nodes are informed that the communication is finished.

The MAC access method based on-demand awakening considers two parts in the aspect of reducing node energy consumption:

the method adopts Linquest Modem parameters and is based on the MAC access method of a cycle dormancy awakening mechanism, the length of an awakening signal is 5s, compared with the awakening signal of the MAC access method awakened as required, the awakening signal is very short, the awakening signal length can be found to be 0.0375s through calculation, and the transmitting power consumption is reduced to a great extent.

The WU signal is transmitted by using TR, so that the utilization rate of a channel can be improved by avoiding collision among various packets, and the waste of energy consumption is reduced by reducing the number of times of data retransmission.

Step 1, a flow chart of the MAC access wakeup on demand method is shown in fig. 1, and in this process, five packet formats are defined:

1.2, an acknowledgement packet of the wake-up signal, referred to as an ACK packet for short, is an acknowledgement packet replied to the sending node after the receiving node is successfully awakened, and simultaneously, channel information is obtained for the TR technology and sent to all the neighbor nodes, and the communication start is declared, the ACK packet adopts a broadcast transmission mode, the packet length is only 21 bits, the packet contains a WU packet header, ID information of the WU packet header and the receiving node, communication start information and channel information, and the WU packet header is used for awakening all the neighbor nodes in a dormant state to receive the ACK packet.

1.3, a DATA packet, namely a DATA packet for short, with a packet length of 256 bits, which contains ID information of the DATA packet and ID information of a receiving node, generation time of the DATA packet and DATA information, wherein the DATA packet is DATA to be transmitted by a sending node, and whether the DATA packet can be correctly received is very important, so that the DATA packet adopts a directional transmission mode, the signal-to-noise ratio at the receiving node is improved by utilizing the space-time focusing of a TR (transmitter-receiver) and the probability of successful reception of the DATA packet is improved, and the DATA packet is prevented from colliding with other control packets.

And 1.4, a DATA confirmation packet, namely an ACKD packet for short, with the packet length of 15 bits, containing ID information and DATA confirmation information, when the receiving node correctly receives the DATA packet, replying the ACKD packet to the sending node to indicate that the DATA is correctly received, and because the packet only needs to respond to the sending node, a directional transmission mode is adopted to reduce the interference to other nodes.

1.5, a communication end packet, called a CHANNEL packet for short, when a sending node receives an ACKD packet, the sending node sends the CHANNEL packet to inform all nodes that the communication is ended, at the moment, other nodes can communicate with the node and acquire CHANNEL information to all neighbor nodes again, a broadcast transmission mode is adopted, the packet length is 21 bits and comprises a WU packet header, address information, communication end information and CHANNEL information, and the WU packet header is used for awakening all the neighbor nodes in a dormant state to receive the CHANNEL packet;

i) if the packet is a WU packet, initializing and entering a step 2;

ii) if not a WU packet, re-entering the sleep state;

step 4, the node is in the state of waiting for ACK at the moment:

step 5, the node is in a state of waiting for ACKD at the moment;

step 6, the node is in a state of waiting for DATA at the moment;

i) if the received DATA packet is a DATA packet, entering step 6;

ii) if a CHANNEL packet is received, proceeding to step 7;

the above MAC access method can be implemented by avoiding the following types of collisions:

one WU packet wakes up all neighbor nodes: by adopting a TR (transmitter-receiver) technology, invalid non-destination nodes are prevented from being awakened, and energy is saved;

multiple WU packets wake up the same destination node: when a plurality of wake-up signals arrive at the same time, the ID information cannot be identified, no processing is carried out, the state of judging the packet type is continued, and the wake-up signals are sent again after the transmitting node randomly backs off; if a plurality of wake-up signals do not arrive at the same time, the receiving node broadcasts a reply ACK after receiving the first wake-up signal to inform that the communication is started. And after other nodes send the WU packet, the first ACK is received, which indicates that the node is known to be in communication, the node enters a dormant state, wakes up after waiting for receiving the CHANNEL packet, and sends a WU signal to start the communication process of the node if the queue has data.

The plurality of WU packets awaken a plurality of destination nodes: since the WU, DATA and ACKD signals are transmitted by TR, there may be multiple pairs of communication nodes communicating simultaneously (the communication channels may not be the same), and compared with the conventional protocol with only one channel, the channel utilization is greatly improved, thereby improving the network throughput.

Collision between WU packet and DATA: both WU and DATA packets are sent using TR, so there are no interference and collision problems between channels; when receiving the WU packet, the receiving node will busy the channel, and at this time will not receive the WU packet sent from other nodes.

The lengths of the control packets such as WU, ACK, ACKD and CHANNEL are far smaller than the length of the DATA packet, so that the conflict between the control packets and the DATA can be effectively avoided, and the DATA transmission efficiency is improved.

The energy consumption simulation comparison of the transmitting node is carried out on the MAC access method based on three different awakening dormancy mechanisms through MATLAB, and comprises the following steps: the final simulation result is shown in fig. 2, without waking up the MAC access method, based on the cyclic dormancy wakeup MAC access method, and based on the on-demand wakeup MAC access method. As shown in fig. 2, the energy consumption of the transmitting node of the MAC access method based on wake-on-demand is the lowest of the three mechanisms, so the service cycle of the network using the MAC access method based on wake-on-demand is the longest.

Taking the network scenario of fig. 3 as an example, a corresponding MAC access method scheme based on-demand wake-up is provided.

In the MAC access method based on demand awakening, nodes can be awakened at any time, so that all nodes without communication tasks are in a dormant state after the nodes are initialized in a network. The node scene of the underwater acoustic sensor network is assumed to be shown in fig. 3, the network has 5 nodes in total, S1 and S2 are sending nodes, R1 and R2 are receiving nodes, N is a neighbor node, and the communicated nodes can be reached in a single hop. The communication task start times of S1 and S2 are random, and it is assumed here that S1 starts communication at 1 st second, S2 starts communication at 2 nd second, and one communication cycle is more than 1 second.

The method comprises the following specific steps:

1. at time 1 second, S1 is woken up by the WU1 packet of the application layer, acknowledging itself as the transmitting node

Then, a WU1 packet is directionally sent to a receiving node R1 by using a TR technology, and an ACK reply of R1 is waited and is marked as ACK 1;

2. after receiving the WU1 packet, the R1 is switched from the dormant state to the active state, processes the WU1 packet after confirming that the packet is taken as a receiving node and the packet is sent to the R, and then broadcasts a reply ACK1 packet, wherein the S1, the R2 and the N node can all receive the ACK1 packet;

3. after receiving the ACK1 packet, the R2 and the N node process the packet, confirm that the packet is not sent to the R2 and the N node through ID information, record channel information in the packet and then enter a dormant state again;

4. after receiving the ACK1 packet, the S1 determines that the ACK packet is an ACK reply to itself, and then processes the ACK1 packet, and then sends the DATA packet to the R1 with TR orientation, and waits for an ACKD reply of the R1, which is recorded as ACKD 1;

5. after the R1 receives the DATA packet, if the DATA information in the packet is confirmed to be correct, the TR direction is used to reply the DATA confirmation packets ACKD1 to S1;

6. s1 processes the ACKD1 package after receiving the ACKD1 package, and broadcasts the CHANNEL1 package to inform that the communication is finished, and then enters the dormant state again after confirming that the data transmission is successful;

7. after receiving the CHANNEL1 packet, the R1 confirms that the communication is finished, and then enters a sleep state;

8. in the communication process of S1 and R1, the S2 and R2 can also communicate by using TR technology, at the time of 2 seconds, the S2 is awakened by a WU2 packet of an application layer, the step 1 is repeated, the WU2 packet is sent to a receiving node R2, and an ACK reply of the R2 is waited and recorded as ACK 2;

9. after receiving the WU2 packet, the R2 repeats step 2, and broadcasts a reply ACK2 packet, at which time both the S2 and R1 nodes can receive an ACK2 packet;

10. after receiving the ACK2 packet, the R1 node repeats the step 3, if the communication process is in progress, the current state is kept continuously, otherwise, the sleep state is entered again;

11. s2, repeating the step 4 after receiving the ACK2 packet;

12. after the R2 receives the DATA packet, if the DATA information in the packet is confirmed to be correct, the TR direction is used to reply the DATA confirmation packets ACKD2 to S2;

13. s2 processes the ACKD2 package after receiving the ACKD2 package, and broadcasts the CHANNEL2 package to inform that the communication is finished after confirming that the data transmission is successful, and at the moment, the R2 and the N node can both receive the CHANNEL2 package and then enter the dormant state again;

14. after receiving the CHANNEL2 packet, the R2 confirms that the communication is finished, and enters the sleep state again;

15. after receiving the broadcasted CHANNEL2 packet, the N node confirms that the S2 and the R2 have finished communication, and if data needs to be sent to the S2 or the R2 at the moment, the N node sends a WU packet to start communication, otherwise, the N node enters a sleep state after recording CHANNEL information.

Claims

1. An on-demand wake-up multiple access method for an underwater network, comprising the steps of:

i) if the packet is a WU packet, initializing and entering a step 2;

ii) if not a WU packet, re-entering the sleep state;

ii) if the WU signal is from the physical layer, the node belongs to a non-transmitting node, the node is converted into an active state, and at the moment, the node needs to be judged to be a receiving node or a neighbor node according to the type of a receiving packet, and the step 3 is carried out;

step 4, the node is in the state of waiting for ACK at the moment:

step 5, the node is in a state of waiting for ACKD at the moment;

step 6, the node is in a state of waiting for DATA at the moment;

i) if the received DATA packet is a DATA packet, entering step 6;

ii) if a CHANNEL packet is received, go to step 7.