CN112533262B - Multi-path on-demand routing method of rechargeable wireless sensor network - Google Patents

Multi-path on-demand routing method of rechargeable wireless sensor network Download PDF

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CN112533262B
CN112533262B CN202011101995.2A CN202011101995A CN112533262B CN 112533262 B CN112533262 B CN 112533262B CN 202011101995 A CN202011101995 A CN 202011101995A CN 112533262 B CN112533262 B CN 112533262B
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CN112533262A (en
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刘贵云
张若扬
钟晓静
蓝雪婧
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Guangzhou University
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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
    • H04W40/023—Limited or focused flooding to selected areas of a network
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/24—Multipath
    • 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
    • H04W40/04—Communication route or path selection, e.g. power-based or shortest path routing based on wireless node resources
    • H04W40/10—Communication route or path selection, e.g. power-based or shortest path routing based on wireless node resources based on available power or energy
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/24—Connectivity information management, e.g. connectivity discovery or connectivity update
    • H04W40/246—Connectivity information discovery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/24—Connectivity information management, e.g. connectivity discovery or connectivity update
    • H04W40/28—Connectivity information management, e.g. connectivity discovery or connectivity update for reactive routing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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Abstract

The invention discloses a multipath on-demand routing method of a rechargeable wireless sensor network, which comprises the following steps: s1, route discovery: the source node broadcasts the RREQ message, and the destination node receives the request packet and returns a RREP message; s2, route response: after receiving the RREP message returned by the destination node, adopting a broadcast response strategy to respond; s3, balancing energy loss of nodes on a path through a parallel transmission strategy in data transmission; s4, route maintenance: after the source node finishes transmitting data, the maintenance network protocol is continued only when the next source node which needs to transmit data but has no path to the destination node appears. The AOMDV-SEC of the invention adopts a broadcast response strategy in a targeted manner to avoid the failure phenomenon of route discovery caused by a unidirectional link, and balances the energy loss of nodes on a path through a parallel transmission strategy to further prolong the life cycle of a network.

Description

Multi-path on-demand routing method of rechargeable wireless sensor network
Technical Field
The invention relates to the technical field of wireless network protocols, in particular to a multi-path on-demand routing method of a rechargeable wireless sensor network.
Background
The silent changes of the life of people benefit from the continuous development of the related technology of the wireless sensor network, and the results are not deeply researched by various students. In many research directions, the problem of energy limitation is of great concern, and therefore, some scholars begin to research strategies on node charging and construct rechargeable wireless sensor networks according to the strategies. Meanwhile, in order to reduce and balance the energy consumption of the nodes, a multi-path on-demand routing protocol is favored. In this type of protocol, the nodes do not need to maintain paths in real time and with each other, and only under the condition that the source node has a need but does not have data transmission, the nodes search a plurality of paths going to the destination node and selectively transmit data in the plurality of paths.
The AOMDV protocol is a classic early multipath on-demand routing protocol, which is a multipath extension protocol of AODV. But these protocols rely only on the "hop count" of a path as the only path selection criterion and their multipath generation mechanisms limit to some extent the maximum number of paths. Therefore, the number of hops of the node and the remaining energy of the node are considered together, and in order to discover more paths, a multi-path on-demand routing protocol EEMP-AODV based on special partially disjoint paths is proposed, which is capable of preventing the nodes from generating congestion. However, the EEMP-AODV does not consider the problem of unidirectional links in the network and the situation that the node is not congested, the generation of the unidirectional link problem makes the source node probably have no way to transmit data, and under the condition of no congestion, the data packet is probably transmitted in an optimal path all the time, and the energy loss situation of the node is not well relieved.
Therefore, there is an urgent need in the industry to develop a method for researching a multi-path on-demand routing protocol in the environment of a rechargeable wireless sensor network, which can overcome the problem of unidirectional links and further alleviate the energy loss of nodes.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a broadcast response strategy combined with a unidirectional link probability estimation model and an improved model, and well overcomes the problem of unidirectional links; and meanwhile, a parallel transmission strategy is adopted, so that the energy loss of the nodes is further relieved.
The purpose of the invention is realized by the following technical scheme:
a multi-path on-demand routing method of a rechargeable wireless sensor network comprises the following steps:
s1, route discovery: the source node broadcasts the RREQ message, and the destination node receives the request packet and returns a RREP message;
s2, route response: after receiving the RREP message returned by the destination node, adopting a broadcast response strategy to respond;
s3, data transmission: the source node needs to adaptively set the total amount of transmitted data packets according to actual conditions, and energy loss of nodes on a path is balanced through a parallel transmission strategy;
s4, route maintenance: after the source node has finished transmitting data, the maintenance network protocol only continues when the next source node that needs to transmit data but has no path to the destination node appears.
Preferably, the route discovery includes:
s11, before broadcasting the RREQ message, the source node adds 1 to the 'destination node sequence number' field of the source node, and sets the TTL value of the RREQ message;
s12, the source node broadcasts RREQ information, and 1 is added to a corresponding RREQ ID field in the information;
s13, the intermediate node judges whether the RREQ message is from the same source node but the RREQ message of the 2 nd and the RREQ message after the 2 nd with different RREQ ID; if not, the intermediate node receives the RREQ message, adds 1 to the hop number fields of the node and the RREQ respectively, adds the previous hop field information of the node, and generates a reverse route;
s14, judging whether the intermediate node is a destination node or not, or whether the intermediate node is a node in the communication range of the destination node or not; if the intermediate node is neither the destination node nor the node in the communication range of the destination node, and the TTL value of the set intermediate node is greater than 0, executing the step S; if the intermediate node is a node within the communication range of the destination node, executing step S16;
s, the intermediate node continuously broadcasts the RREQ message, subtracts 1 from the TTL value, and repeatedly executes S12-S14;
s16, the intermediate node broadcasts DREQ information, wherein only the target node receives the DREQ information;
s17, the destination node receives the request packet, and if the serial number of the request packet is greater than that of the destination node, the serial number of the request packet is assigned to the serial number of the destination node; otherwise, if the sequence number of the request packet is not greater than the sequence number of the destination node, no processing is performed; the destination node then starts to transmit back the RREP message.
Preferably, the route reply includes:
s21, the node receives the RREP message returned by the destination node, adds the field information of the next hop of the node, sets the effective time of the forward route, and updates the field of the path node minimum residual energy of the RREP;
s22, judging whether the node receiving the RREP message is a source node; if not, executing step S23; if yes, executing step S24;
s23, combining the unidirectional link probability estimation model, comparing the geographical distance d between the node receiving the RREP message and the neighbor node with the set radius threshold value R 0 Determining the propagation strategy of the RREP according to the size of the RREP;
s24, the node receiving the RREP message selects the path corresponding to the field with the maximum value as an optimal path according to a path quality calculation formula, and prepares to transmit a data packet; if d > R 0 If P is greater than 0, the node broadcasts RREP; otherwise, if d is less than or equal to R 0 Then P =0 and the node still unicasts a RREP.
Preferably, the unidirectional link probability estimation model is a probability P (d) that a link between the node i and the node j is a unidirectional link when the node i receives the RREQ sent by the node j i，j ，R 0 ) Is composed of
Figure GDA0002933948470000041
Wherein d is i，j Is the geographical distance of the node i, j, and R is the communication radius of the node. R 0 To generate the radius threshold for the unidirectional link, λ is a base parameter, and R 0 ∈[0，R]，λ∈(0，+∞)。
Preferably, the "path quality" calculation formula is:
Figure GDA0002933948470000042
wherein alpha represents an influence factor, RE and HC respectively represent a path energy index and a path hop index and respectively satisfy
Figure GDA0002933948470000043
Figure GDA0002933948470000044
Wherein
Figure GDA0002933948470000045
Represents a path P i The residual energy of the ith node among the upper m nodes, IE represents the initial energy of the node,
Figure GDA0002933948470000046
the hop count of the ith path in the w paths from the source node to the destination node.
Preferably, the first and second electrodes are formed of a metal,
assuming that the transmission times Total _ Package _ transitions of the source node in the ith round of data transmission satisfy the following formula:
Total_Packet_Transfers(i)＝Slow(i)*Row(i)*Number(i)
wherein Slow represents a circadian-period transmission influence factor, row represents a residual energy transmission influence factor, and Number represents a Number-of-paths transmission influence factor;
the data transmission comprises:
s31, the source node determines the Number value, namely the transmission Number of the data packets in one data transmission according to the discovered path Number, namely the Number of the field information of the last hop
S32, combining a solar energy supply model, and if the nodes in the network are in the time period from 9 am to 14 pm, setting the Slow value to be 4; if the energy supplement rate of the node is low, even 0, not in the time period, even in the night environment, the Slow value is set to be 2;
s33, the source node has 3 or more than 3 pieces of path information, namely when the Number is more than or equal to 3, if the re values corresponding to 3 or more than 3 paths are less than half of the maximum value of the node energy, namely the Number of the field values of the path node minimum residual energy in the RREP received by the source node, which are less than half of the maximum value of the node energy, is not less than 3, the Row value is 1; otherwise, the Row value is 2;
s34, when the path information owned by the source node is less than 3, namely the Number is less than 3, if the re value corresponding to 1 or more than 1 path is less than half of the maximum value of the node energy, namely the Number of the field value of the path node minimum residual energy in the RREP received by the source node, which is less than half of the maximum value of the node energy, is more than 0, the Row value is 1; otherwise, the Row value is 2;
s35, when the downstream nodes on the paths receive the data packets, the Number values of the nodes are determined according to the Number of the field information of the next hop, and the values of Slow and Row in the round are still adopted and substituted into a formula of transmission times Total _ Packet _ Transfers, so that the corresponding Number of data packets are sequentially distributed to the corresponding paths.
Preferably, the route maintenance comprises:
when the 'next hop' of the intermediate node is not reachable, adding 1 to the serial number of the 'next hop' node, and returning a RERR message by the node along a reverse route to delete a corresponding failure path, namely the 'next hop' information of the upstream node;
the source node continues to use the remaining paths for data transmission; meanwhile, according to the existing path Number, the source node adjusts the Number of the data packets transmitted at one time, namely the Number value.
Compared with the prior art, the invention has the following advantages:
the multi-path on-demand routing protocol AOMDV-SEC sets a solar energy replenishment model for the node, and meanwhile, the node sets the data transmission times of each round according to the ambient environment and the self residual energy condition. Because nodes in the network do not need to maintain all paths of the topology in real time, the nodes do not have the route reaching the base station under the general condition, therefore, before data transmission, a route discovery process is initiated firstly, a proper TTL value is set according to the area size, the RREQ is prevented from being distributed throughout the whole network, and meanwhile, in order to overcome a series of problems generated by a unidirectional link, the nodes determine whether to adopt a broadcast response strategy according to specific conditions. Finally, according to the number of paths, the source node sets the number of data packets to be transmitted in one data transmission, and the intermediate node equally distributes the data packets in the paths according to the number of 'last hops', namely the owned path information.
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The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic structural diagram of a multi-path on-demand routing method of a rechargeable wireless sensor network according to the present invention.
Fig. 2 is a schematic structural diagram of a DREQ message mechanism according to the present invention.
FIG. 3 is a simulation diagram constructed by using MATLAB software.
FIG. 4 is a graph of the effective number of cycles of EEMP-AODV and AOMDV-SEC.
FIG. 5 is a graph of the actual round number data for EEMP-AODV and AOMDV-SEC.
FIG. 6 is a graph of the mean failure rate of route discovery for EEMP-AODV and AOMDV-SEC.
FIG. 7 is a graph of the routing discovery failure rate variance of EEMP-AODV and AOMDV-SEC.
Detailed Description
The invention is further illustrated by the following figures and examples.
The Wireless Sensor Network (WSN) is a Network with the forms of self-organization, multi-hop transmission, etc. formed by a large number of micro Sensor nodes through a Wireless communication mode. The system is small in size, low in cost and easy to deploy, and object monitoring and data acquisition are carried out in a specific environment. The charging module is arranged in the sensor node, so that the nodes can automatically supplement energy without replacing batteries, and the nodes form a rechargeable wireless sensor network, so that the life cycle of the network is better prolonged. According to the invention, the solar energy collection and conversion device is arranged in the node, so that the node can continuously supplement energy by using environmental energy.
For better deployment, it is assumed that the nodes in the network satisfy the following preconditions:
(1) all nodes are randomly deployed in a square area with the side length Zm, wherein Z belongs to C. And all nodes have the same altitude.
(2) Once all nodes are deployed, the location does not change any more and has a unique node ID.
(3) All nodes are homogeneous and have the same communication radius.
(4) The Base Station (BS) located at the center of the area serves as a sink node in the network and is also a destination node of all nodes in the network. The source node is randomly selected from other nodes.
(5) The base station has strong computing capability and does not have the problem of energy limitation.
(6) The weather in the environment is constant over a period of time.
(7) In a period of time, at the same time of different days, the energy supplement value of the node basically tends to be stable, but slightly fluctuates due to the influence of the environment, and the influence degree of each node is slightly different.
(8) Nodes in the network may be in either a daytime or nighttime environment.
(9) The links between nodes in the network are not perfectly symmetrical, but do not take into account the possibility of unidirectional links occurring during data transmission.
The r does not take into account the possibility of unidirectional links between the base station and the base station's neighbor nodes.
Figure GDA0002933948470000083
All nodes trust each other.
Meanwhile, in the network, the following two energy models are adopted by the nodes.
The FORM model: in the WSN environment, data forwarding and data reception dominate the energy consumption of the nodes. Heinzelman W B, etc [25] A simplified energy loss Model (First Order Radio Model) of the wireless sensor network node is applied. If the node i receives the data packet sent by the node j, the energy consumption of the node j is
Figure GDA0002933948470000081
The energy consumption of node i is
E DX (l)＝l×E elec
Wherein E TX (l，d i，j ) For the energy consumption of the transmitting end, E DX (l) For the energy consumption of the receiving end, E elec For the basic energy consumption required for processing data in the transceiver circuit, l is the bit value of the data packet, ε fs For free space transmission of coefficient of power consumption, epsilon mp Transmitting coefficient of power for multipath fading, d i，j Is the geographical distance of the node i, j, and R is the communication radius of the node. d 0 Is a data transmission threshold value, and the threshold value is satisfied
Figure GDA0002933948470000082
Solar energy supply model: the model takes into account the effective light receiving area of the solar panel, wherein the effective light receiving area depends on the complementary angle of the light incidence angle; meanwhile, data fitting is carried out according to the light radiation intensity at the same moment in 6 days to obtain a probability density function F (t) approximately meeting normal distribution and a corresponding distribution function F (t), and the output electric energy h (t) of the node cell panel in a period of time is calculated according to the set parameters and the variables to be
Figure GDA0002933948470000091
Where η =0.15 is the energy conversion efficiency of the solar panel, σ =2, μ =12, s is the surface area of the solar panel, t denotes the acquisition time, n denotes the specific number of days, θ denotes the complement of the incident angle, and the complement θ satisfies the condition
Figure GDA0002933948470000092
The model is a result obtained by performing data fitting after multiple sampling, in practice, different degrees of deviation values exist in H (t) of a node under the influence of environment, and if omega is the deviation value of the influence of the environment and epsilon is the deviation degree, the actual output electric energy H (t) of a node battery plate is
H(t)＝ω×h(t)ω∈[1-ε，1+ε]，ε∈[0，1]
The multi-path On-demand routing method of the rechargeable wireless sensor network is an Ad-hoc On-demand routing protocol (AOMDV-SEC) based On a Solar Energy Collection type sensor network. The AOMDV-SEC protocol can be divided into 4 parts, route discovery, route reply, route maintenance and data transfer, respectively. When receiving the message, the intermediate node firstly judges the Type of the message according to the Type value in the message format. 1 represents RREQ or DREQ;2 represents RREP;3 represents RERR; if the Type value is not any of the above 3, a packet is received on behalf of the intermediate node. Generally, if only one source node performs a route discovery process or the like, the intermediate node receives the RREQ or DREQ first, and possibly the RREP. If the intermediate node receives the RREP, the node is likely to receive data packets transmitted hop by hop from the source node to the destination node after a moment of time. After a period of time, if the link is broken in the path, the node that is unreachable by the next hop returns the RERR to the source node along the reverse route, and determines which route information to delete according to the situation. However, when a plurality of source nodes initiate a route discovery process almost simultaneously, the intermediate nodes do not necessarily receive corresponding messages according to the above sequence, so the invention is necessary to perform module planning of the algorithm through the view of any intermediate node itself. The method comprises the following specific steps:
referring to fig. 1, a multi-path on-demand routing method for a rechargeable wireless sensor network includes:
s1, route discovery: the source node broadcasts the RREQ message, and the destination node receives the request packet and returns a RREP message;
when receiving the message, the intermediate node firstly judges the Type of the message according to the Type value in the message format. 1 represents RREQ or DREQ;2 represents RREP;3 represents RERR; if the Type value is not any of the above 3, a packet is received on behalf of the intermediate node. Generally, if only one source node performs a route discovery process or the like, the intermediate node receives the RREQ or DREQ first, and possibly the RREP. If the intermediate node receives the RREP, the node is likely to receive data packets transmitted hop by hop from the source node to the destination node after a moment of time. After a period of time, if a link is broken in the path, the node that is inaccessible for the next hop returns the RERR to the source node along the reverse route, and the route information to be deleted is determined according to the situation. However, when multiple source nodes initiate the route discovery process almost simultaneously, the intermediate nodes do not necessarily receive the corresponding messages in the above order
Specifically, the route discovery includes:
s11, before broadcasting the RREQ message, the source node adds 1 to the 'destination node sequence number' field of the source node, and sets the TTL value of the RREQ message;
s12, the source node broadcasts RREQ information, and 1 is added to a corresponding RREQ ID field in the information; the maximum value of the message ID field of the multiple RREQs depends on the neighbor node count value of the source node.
S13, the intermediate node judges whether the RREQ message is from the same source node but the RREQ message of the 2 nd and the RREQ message after the 2 nd with different RREQ ID; if not, the intermediate node receives the RREQ message, adds 1 to the hop number fields of the node and the RREQ respectively, adds the previous hop field information of the node, and generates a reverse route; if the serial number of the RREQ is smaller than the serial number of the node, assigning the serial number of the node to the serial number of the RREQ; otherwise, if the sequence number of the RREQ is not less than the sequence number of the node, no processing is performed.
S14, judging whether the intermediate node is a destination node or not, or whether the intermediate node is a node in the communication range of the destination node or not; if the intermediate node is neither the destination node nor the node in the communication range of the destination node, and the TTL value of the intermediate node is set to be greater than 0, executing the step S; if the intermediate node is a node within the communication range of the destination node, executing step S16;
s, the intermediate node continuously broadcasts the RREQ message, subtracts 1 from the TTL value, and repeatedly executes S12-S14;
s16, the intermediate node broadcasts DREQ information, wherein only the target node receives the DREQ information;
in order to enable a Destination node to receive RREQs broadcasted from different directions and reduce the proportion of the number of public links in a network to the total number of links between nodes, a DREQ message mechanism (Destination Request) is provided. Firstly, the nodes in the network are subjected to preliminary region division, and the division standard is whether the target node exists in a neighbor node table of the nodes. If yes, when the node receives the RREQ broadcasted by the 'last hop' node, the node broadcasts a DREQ message, the DREQ is a special RREQ, when the neighboring node receives the DREQ, the neighboring node judges whether the neighboring node is a target node or not, if yes, the neighboring node receives the DREQ and unicasts the RREP along a reverse route formed by the 'last hop' node including the node, and if not, the DREQ is discarded; if not, the node continues broadcasting after receiving the RREQ unless the node is the destination node.
As shown in fig. 2, the node pointed by the single-line solid arrow and the arrow indicates that RREQ broadcast from the neighbor node of the "previous hop" is received by the node, the double-line solid arrow indicates that DREQ broadcast from the neighbor node in the communication range of the destination node is received by the destination node, the dotted line indicates that the node discards the DREQ, and nodes W, X, Y and Z are all neighbor nodes of the destination node D. When nodes X, Y and Z receive RREQ messages broadcasted from nodes T, U and V respectively, the nodes X, Y and Z broadcast DREQ because neighbor nodes of the nodes comprise destination nodes. Since nodes T, U, V, W are not destination nodes, only D receives DREQ, and the rest of nodes discard DREQ.
The mechanism can ensure that the destination node D can receive RREQ messages from different directions, and simultaneously reduces the quantity value of public links in a path, but if the neighbor node is not only in the communication range of the destination node, but also the neighbor nodes of the node are in the communication range of the destination node, under the DREQ mechanism, the neighbor nodes can not receive the DREQ messages all the time, namely, the neighbor nodes become a special isolated node. For example, node W in fig. 2, because the neighbor nodes of nodes T, U, and V do not include node W, and node W must discard the DREQ broadcasted from nodes X, Y, and Z, node W does not participate in the data receiving and forwarding operations in the network under the DREQ message mechanism in a certain sense.
S17, the destination node receives the request packet (RREQ message), and if the sequence number of the request packet is greater than that of the destination node, the sequence number of the request packet is assigned to the sequence number of the destination node; otherwise, if the sequence number of the request packet is not greater than the sequence number of the destination node, no processing is performed; and then the destination node starts to transmit back the RREP message.
S2, route response: after receiving the RREP message returned by the destination node, adopting a broadcast response strategy to respond; if the node is used only to collect data and transmit the data to the base station, the node does not need to perform route discovery and data transmission in real time. Therefore, at this stage, the source node needs to adaptively set the total amount of transmitted data packets according to the actual situation, wherein how to allocate the transmission times and how many data packets are transmitted at one time all need to be discussed according to the situation.
Specifically, the route reply includes:
s21, the node receives the RREP message returned by the destination node, adds the field information of the next hop of the node, sets the effective time of the forward route, and updates the field of the minimum residual energy of the route node of the RREP;
s22, judging whether the node receiving the RREP message is a source node; if not, executing step S23; if yes, go to step S24;
s23, combining the unidirectional link probability estimation model, comparing the geographical distance d between the node receiving the RREP message and the neighbor node with the set radius threshold value R 0 Determining the propagation strategy of the RREP according to the size of the RREP;
s24, the node receiving the RREP message selects the path corresponding to the field with the maximum value as an optimal path according to a path quality calculation formula, and prepares for transmitting a data packet; if d > R 0 If P is greater than 0, the node broadcasts RREP; otherwise, if d is less than or equal to R 0 Then P =0 and the node still unicasts the RREP.
In this embodiment, the unidirectional link probability estimation model is a probability P (d) that when the node i receives the RREQ sent from the node j, the link between the node i and the node j is a unidirectional link i，j ，R 0 ) Is composed of
Figure GDA0002933948470000131
Wherein d is i，j Is the geographical distance of the node i, j, and R is the communication radius of the node. R is 0 To generate the radius threshold for the unidirectional link, λ is a base parameter, and R 0 ∈[0，R]，λ∈(0，+∞)。
In this embodiment, the "path quality" calculation formula is:
Figure GDA0002933948470000132
wherein alpha represents an influence factor, RE and HC respectively represent a path energy index and a path hop index and respectively satisfy
Figure GDA0002933948470000141
Figure GDA0002933948470000142
Wherein
Figure GDA0002933948470000143
Represents a path P i The remaining energy of the ith node among the upper m nodes, IE represents the initial energy of the node,
Figure GDA0002933948470000144
the hop count of the ith path in the w paths from the source node to the destination node.
S3, data transmission: the source node needs to adaptively set the total amount of transmitted data packets according to actual conditions, and energy loss of nodes on a path is balanced through a parallel transmission strategy; in certain situations, if a node is not congested, packets will all travel along an optimal path unless a later discovered path is better than an earlier discovered path. Therefore, in order to more fully utilize the paths that have been discovered by the source node, and to simplify the packet offloading operation, it is very necessary to directly adopt the packet parallel transmission strategy.
The method comprises the steps of setting the number of data packets required for transmitting data once according to the number of paths found by a source node, and evenly dividing the data packets equally in each path, namely, as long as a small number of even one data packet is transmitted on each path, on the premise that the packet loss phenomenon does not occur, the method is equivalent to that the source node transmits a plurality of data packets to a destination node. Wherein, according to the calculation formula of the path quality, the optimal path can be selected, if the value of the impact factor corresponding to the path energy index is increased, the number of data packet transmission can be properly increased on the optimal path. This allows the advantage of multipath to be better reflected in the short term than a data transmission scheme that concentrates all packets into an optimal path.
In this embodiment, it is assumed that, in the ith round of data transmission, the Total _ Packet _ Transfers of the transmission times satisfies the following formula:
Total_Packet_Transfers(i)＝Slow(i)*Row(i)*Number(i)
wherein Slow represents a circadian-period transmission influence factor, row represents a residual energy transmission influence factor, and Number represents a Number-of-paths transmission influence factor;
specifically, the data transmission includes:
s31, the source node determines the Number value, namely the transmission Number of the data packets in one data transmission according to the discovered path Number, namely the Number of the field information of the last hop
S32, combining a solar energy supply model, and if the nodes in the network are in the time period from 9 am to 14 pm, setting the Slow value to be 4; if the energy supplement rate of the node is low, even 0, not in the time period, even in the night environment, the Slow value is set to be 2;
s33, the source node has 3 or more than 3 pieces of path information, namely when the Number is more than or equal to 3, if the re values corresponding to 3 or more than 3 paths are less than half of the maximum value of the node energy, namely the Number of the field values of the path node minimum residual energy in the RREP received by the source node, which are less than half of the maximum value of the node energy, is not less than 3, the Row value is 1; otherwise, the Row value is 2;
s34, when the path information owned by the source node is less than 3, namely the Number is less than 3, if 1 or more than 1 paths correspond to the value of re which is less than half of the maximum value of the node energy, namely the Number of the value of the field of the path node minimum residual energy in the RREP received by the source node which is less than half of the maximum value of the node energy is more than 0, the Row value is 1; otherwise, the Row value is 2;
s35, when the downstream nodes on the paths receive the data packets, the Number values of the nodes are determined according to the Number of the field information of the next hop, and the values of Slow and Row in the round are still adopted and substituted into a formula of transmission times Total _ Packet _ Transfers, so that the corresponding Number of data packets are sequentially distributed to the corresponding paths.
S4, route maintenance: after the source node has finished transmitting data, the maintenance network protocol only continues when the next source node that needs to transmit data but has no path to the destination node appears.
Specifically, the route maintenance includes:
when the 'next hop' of the intermediate node is not reachable, adding 1 to the serial number of the 'next hop' node, and returning a RERR message by the node along a reverse route to delete a corresponding failure path, namely the 'next hop' information of the upstream node;
the source node continues to use the remaining paths for data transmission; meanwhile, according to the existing path Number, the source node adjusts the Number of the data packets transmitted at one time, namely the Number value.
Simulation of experiment
MATLAB software is used for constructing a square area with the side length of 800m, the number of nodes is 201 (including base stations), the base stations are deployed in the center of the area, the rest nodes are deployed randomly, and a simulation parameter list shown in a table 1-1 is set. Where the base station is marked as diamond (next to BS), node No. 4 (upper right of node No. 174) is selected as the source node for this round; the two circles represent the communication boundaries of the source node and the base station, respectively. Since the base station has 6 neighbor nodes, according to the multi-path generation mechanism of the EEMP-AODV protocol and the AOMDV-SEC protocol, the conclusion that the source node can find 6 paths at most can be obtained.
TABLE 1-1 simulation parameter List
Figure GDA0002933948470000171
Analysis of simulation results
The network life cycle definition uses whether the source node can continue data transmission as a standard, defines the network life cycle as the time corresponding to that the source node does not find the destination node in several consecutive rounds, and replaces the network life cycle with the number of simulation rounds as the sampling time interval is random and does not exceed 6 minutes at most.
Due to the unidirectional link problem in the network, the latency of the network becomes very large if no adequate solution is adopted. Therefore, in multiple rounds of simulation, if the source node has the condition of transmitting data through one Round of route discovery, the Effective Round number (Effective _ Round) is added with one, otherwise, the failure times (failurs) are added with one, and the sum of the Effective Round number and the failure times is the actual Round number, namely the Total Round number (Total _ Round). The relationship of the three is expressed by the following formula:
Total_Round＝Effective_Round+Failures (1)
as shown in fig. 4 and fig. 5, the number of times of successive failures of route discovery of the source node is defined as 3 times, 5 times, 8 times and 13 times, respectively, and the number of effective rounds and the actual round data of EEMP-AODV and AOMDV-SEC are obtained by performing experiments for 6 times with different protocols under different definitions, respectively, in combination with the above formula.
Meanwhile, the route discovery failure rate is defined as the ratio of the effective round number to the actual round number, and is expressed by the following formula:
Figure GDA0002933948470000181
according to the formula (1) and the formula (2), 6 groups of route discovery failure rates (failrates _ Rate) under 4 different definitions are calculated respectively. The 6 groups of data were sequentially averaged and varied, and the results are shown in fig. 6 and 7.
It can be found that the route discovery failure rate of the EEMP-AODV reaches at least 25%, and reaches at most even nearly 50%, wherein when the number of continuous failures is 3, the corresponding variance of the failure rate of the EEMP-AODV is relatively large, which indicates that under the definition, if the source node can not find the path to the destination node continuously for many times, the network ends operation when the definition condition is satisfied for stopping loss in time; meanwhile, because the existence of the unidirectional link has uncertainty, even if a loose ending condition is set, such as a condition that the number of continuous failures reaches 3 times, the source node can find the path on the premise that the definition condition is not met.
If the ending condition, i.e. the failure times, in the network life cycle defining condition is continuously adjusted to be high, the absolute value of the difference between the failure rates of AOMDV-SEC and EEMP-AODV is properly reduced. The network applying the EEMP-AODV protocol cannot be easily ended in advance due to the problem of the unidirectional link along with the stricter ending condition of the network; meanwhile, as the nodes are randomly deployed in the network, the number of the last hops of the destination node is uncertain, that is, the maximum value of the number of paths that can be discovered by the source node is also uncertain. So in most cases, the source node will not find a path to the destination node because nodes near the destination node die consecutively, which is also the same in AOMDV-SEC. Under strict end conditions, the network has large variance of the failure rate of route discovery due to the randomness of the maximum value of the number of paths. Fig. 6 shows that the failure rate of AOMDV-SEC gradually increases under the condition that the network termination condition is more and more strict, such as the condition that the number of consecutive failures reaches 13 times; fig. 7 also shows that the failure rate variance of EEMP-AODV is also large under the setting that the network has 13 consecutive failures.
However, the AOMDV-SEC adopts a parallel transmission strategy, the failure rate of the AOMDV-SEC is lower than that of the EEMP-AODV, and meanwhile, under the condition of the same network life cycle definition and the same effective round number, the node energy consumption of the EEMP-AODV is more unbalanced. Under the setting that the network life cycle is defined as that the source node finishes without finding a path for 5 times continuously and the number of effective rounds does not exceed 300 rounds, the final number of effective rounds of EEMP-AODV is only 250 rounds, and the total number of failures reaches 83 times. In such a case, the energy consumption of EEMP-AODV is still unbalanced, and a total of 7 dead nodes appear in the network, wherein there are 4 dead nodes in the communication range of the destination node. On the premise that the number of effective rounds reaches 300 rounds, compared with the node energy consumption situation of EEMP-AODV, the AOMDV-SEC protocol finds that under the same condition, the node energy consumption is more uniform by adopting the parallel transmission strategy. Wherein, when the number of effective rounds of EEMP-AODV is less than 300 rounds, more dead nodes appear; and after the effective round number of the AOMDV-SEC reaches 300 rounds, no dead node still appears.
From the above analysis, the tabulated comparative results shown in tables 1-2 can be obtained.
TABLE 1-2 comparison of Performance of two protocols
Figure GDA0002933948470000201
In summary, the AOMDV-SEC of the present invention specifically adopts the broadcast reply strategy to avoid the failure of route discovery caused by the unidirectional link, and balances the energy loss of the nodes on the path through the parallel transmission strategy, thereby further prolonging the life cycle of the network.
The above detailed description is a preferred embodiment of the present invention, and is not intended to limit the present invention, and any other modifications or equivalent substitutions that do not depart from the spirit of the present invention are intended to be included within the scope of the present invention.

Claims (6)

1. A multi-path on-demand routing method for a rechargeable wireless sensor network, comprising:
s1, route discovery: the source node broadcasts the RREQ message, and the destination node receives the request packet and returns a RREP message;
s2, routing response: after receiving the RREP message returned by the destination node, adopting a broadcast response strategy to respond; the route reply comprises:
s21, the node receives the RREP message returned by the destination node, adds the field information of the next hop of the node, sets the effective time of the forward route, and updates the field of the path node minimum residual energy of the RREP;
s22, judging whether the node receiving the RREP message is a source node; if not, executing step S23; if yes, go to step S24;
s23, combining the unidirectional link probability estimation model, comparing the geographical distance d between the node receiving the RREP message and the neighbor node with the set radius threshold value R 0 Determining the propagation strategy of the RREP according to the size of the RREP;
s24, the node receiving the RREP message selects the path corresponding to the field with the maximum value as an optimal path according to a path quality calculation formula, and prepares to transmit a data packet; if d > R 0 If P is greater than 0, the node broadcasts RREP; otherwise, if d is less than or equal to R 0 If P =0, the node still unicasts RREP; wherein, P represents the probability that the link between the node receiving the RREP message and the neighbor node is a unidirectional link;
s3, data transmission: the source node needs to adaptively set the total amount of transmitted data packets according to actual conditions, and energy loss of nodes on a path is balanced through a parallel transmission strategy;
s4, route maintenance: after the source node finishes transmitting data, the maintenance network protocol is continued only when the next source node which needs to transmit data but has no path to the destination node appears.
2. The multi-path on-demand routing method for a chargeable wireless sensor network of claim 1, wherein the route discovery comprises:
s11, before broadcasting the RREQ message, the source node adds 1 to the own 'destination node sequence number' field and sets the TTL value of the RREQ message;
s12, the source node broadcasts RREQ information, and 1 is added to a corresponding RREQ ID field in the information;
s13, the intermediate node judges whether the RREQ message is from the same source node but the RREQ message of the 2 nd and the RREQ message after the 2 nd with different RREQ ID; if not, the intermediate node receives the RREQ message, adds 1 to the hop number fields of the node and the RREQ respectively, adds the previous hop field information of the node, and generates a reverse route;
s14, judging whether the intermediate node is a destination node or not, or whether the intermediate node is a node in the communication range of the destination node or not; if the intermediate node is neither the destination node nor the node in the communication range of the destination node, and the TTL value of the intermediate node is set to be greater than 0, executing the step S; if the intermediate node is a node within the communication range of the destination node, executing step S16;
s15, the intermediate node continuously broadcasts the RREQ message, subtracts 1 from the TTL value, and repeatedly executes S12-S14;
s16, the intermediate node broadcasts DREQ information, wherein only the target node receives the DREQ information;
s17, the destination node receives the request packet, and if the serial number of the request packet is greater than that of the destination node, the serial number of the request packet is assigned to the serial number of the destination node; otherwise, if the sequence number of the request packet is not greater than the sequence number of the destination node, no processing is performed; and then the destination node starts to transmit back the RREP message.
3. The multi-path on-demand routing method for the rechargeable wireless sensor network according to claim 2, wherein the unidirectional link probability estimation model is the probability P (d) that when the RREQ sent by the node j is received by the node i, the link between the node i and the node j is a unidirectional link i，j ，R 0 ) Is composed of
Figure FDA0003947516310000021
Wherein d is i，j Is the geographical distance of the node i, j, R is the communication radius of the node, R 0 To generate a radius threshold for the unidirectional link, λ is a base parameter, and R 0 ∈[0，R]，λ∈(0，+∞)。
4. The multi-path on-demand routing method for a rechargeable wireless sensor network of claim 3, wherein the "path quality" calculation formula is:
Figure FDA0003947516310000031
wherein alpha represents an influence factor, RE and HC respectively represent a path energy index and a path hop index and respectively satisfy
Figure FDA0003947516310000032
Figure FDA0003947516310000033
Wherein
Figure FDA0003947516310000034
Represents a path P i In the upper m nodesThe remaining energy of the ith node, IE represents the initial energy of the node,
Figure FDA0003947516310000035
the hop count of the ith path in the w paths from the source node to the destination node.
5. The multi-path on-demand routing method for a rechargeable wireless sensor network of claim 4,
assuming that the transmission times Total _ Package _ transitions of the source node in the ith round of data transmission satisfy the following formula:
Total_Packet_Transfers(i)＝Slow(i)*Row(i)*Number(i)
wherein Slow represents a circadian-period transmission influence factor, row represents a residual energy transmission influence factor, and Number represents a Number-of-paths transmission influence factor;
the data transmission comprises the following steps:
s31, the source node determines the Number value, namely the transmission Number of the data packets in one data transmission according to the discovered path Number, namely the Number of the field information of the last hop
S32, combining a solar energy supply model, and setting a Slow value to be 4 if the nodes in the network are positioned in a time period from 9 am to 14 pm; if the energy supplement rate of the node is low, even 0, not in the time period, even in the night environment, the Slow value is set to be 2;
s33, when the source node has 3 or more than 3 pieces of path information, namely the Number is more than or equal to 3, if the re value corresponding to 3 or more than 3 paths is less than half of the maximum value of the node energy, namely the Number of the field value of the path node minimum residual energy in the RREP received by the source node, which is less than half of the maximum value of the node energy, is not less than 3, the Row value is 1; otherwise, the Row value is 2;
s34, when the path information owned by the source node is less than 3, namely the Number is less than 3, if 1 or more than 1 paths correspond to the value of re which is less than half of the maximum value of the node energy, namely the Number of the value of the field of the path node minimum residual energy in the RREP received by the source node which is less than half of the maximum value of the node energy is more than 0, the Row value is 1; otherwise, the Row value is 2;
s35, when the downstream nodes on the path receive the data packets, determining the Number values of the nodes according to the Number of the 'next hop' field information, and substituting the values of Slow and Row in the round into a formula of transmission times Total _ Packet _ transitions to sequentially distribute the corresponding Number of data packets to the corresponding paths.
6. The multi-path on-demand routing method for a rechargeable wireless sensor network of claim 5, wherein the route maintenance comprises:
when the 'next hop' of the intermediate node is not reachable, adding 1 to the serial number of the 'next hop' node, returning a RERR message by the node along a reverse route, and deleting a corresponding failure path, namely 'next hop' information of an upstream node;
the source node continues to use the remaining paths for data transmission; meanwhile, according to the existing path Number, the source node adjusts the Number of the data packets transmitted at one time, namely the Number value.
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