CN113596949B - Routing method based on multi-source path interference optimization under multi-event triggering - Google Patents
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Abstract
The invention relates to a routing method based on multi-source path interference optimization under multi-event triggering, which comprises the following steps: initializing a network; clustering strategies based on multiple event triggers; candidate relay selection based on an interference avoidance mechanism; relay election based on interference sensitivity; power control and data multi-hop transmission. The invention ensures that the transmission links of different events are completely disjoint and the interference degree among the links is smaller by introducing the node state and the interference sensitivity, effectively solves the interference conflict problem in the multipath parallel transmission data, and improves the transmission efficiency of the network.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a routing method based on multi-source path interference optimization under multi-event triggering.
Background
Along with the continuous improvement of communication technology, the development scale of the wireless sensor network is larger and larger, large-scale sensor nodes are densely deployed in a monitoring area, environment is monitored or target tasks are tracked in real time, sensitive events occurring in the environment are responded, and corresponding countermeasures are taken. In a large-scale wireless sensor network, real-time monitoring is continuously performed by utilizing all nodes, so that a large amount of unnecessary energy consumption is easily caused, and therefore, the event-driven network is widely applied to a plurality of fields such as forest fire prevention, medical application and the like instead of a time-driven network.
When the event is not triggered, the common node is mostly dormant, the node only periodically collects a small amount of data, and when the event occurs, the node is activated and performs data collection and transmission. In the past, most of event-driven sensor networks are based on a routing algorithm triggered by a single event, and if a plurality of event links transmit data at the same time, interference conflict can be generated among different links, so that the transmission efficiency of the network is reduced. In an actual large-scale wireless sensor network, the occurrence of events often has randomness and multiple occurrence, and a plurality of different events may occur in different places, so that the network is required to be capable of timely collecting a plurality of event information and safely and reliably transmitting the event information to the same Sink node (Sink node for short).
The existing communication mechanism based on time division multiple access (TDMA for short) and carrier sense multiple access/collision avoidance (CSMA/CA for short) has certain communication defects for the wireless sensor network under the drive of multiple events.
TDMA is a typical fixed allocation mechanism, in which time slot resources are allocated to nodes in a network in advance, each node in the network sends information according to the allocated time slot resources, and by dynamically reserving data time slots, conflicts generated by contention can be effectively avoided, but in a wireless sensor network under event driving, the occurrence of events has burstiness, TDMA is difficult to allocate time slots in advance to randomly triggered active nodes to transmit data, and the data is dynamically changed under event triggering, while TDMA is insensitive to the change of data traffic to be sent, and a large amount of bandwidth loss is easily caused.
CSMA mechanism is a typical random access mechanism, and each node in the network avoids collision by interception and random avoidance. The node needs to monitor the channel before transmitting data, if the channel is idle, the node transmits the data immediately, and if the channel is busy, the node waits for a period of time until the transmission of the data information in the channel is finished, and then the node starts the data information. And if the data conflict, performing a rollback attempt to retransmit the data information. The wireless communication network based on the CSMA mechanism can effectively reduce the probability of collision occurrence and can be well adapted to the access of emergency nodes. However, as the number of trigger events increases, the density between transmission nodes increases, and the CSMA mechanism generates serious collisions, resulting in a dramatic decrease in network throughput and a decrease in transmission efficiency.
The following problems are mainly faced with designing a multi-source routing algorithm that satisfies event-based triggering:
firstly, for a wireless sensor network triggered by multiple events, multiple transmission links exist for transmitting event data, data signals in different transmission links are overlapped, and the mutual interference among the links not only causes a great amount of waste of network node energy, but also causes rapid increase of data transmission delay, so that network throughput is reduced, and the transmission efficiency of the network is seriously reduced. How to reduce the interference probability of data sent by the nodes and improve the transmission efficiency is a key problem of the wireless sensor network.
Secondly, for a multi-event driven wireless sensor network, the data transmission quantity is large, the transmission energy consumption is high, and how to design an algorithm to construct a proper transmission path to balance the energy consumption of each node is a difficulty and an important point of research to maximize the life cycle of the whole network.
In the existing routing research of the wireless sensor network based on event driving, the very important goal of reducing network interference is ignored in most optimization algorithms, and the routing algorithm is designed only from the point of view of network energy consumption. The constructed network topology has larger interference, signals of a plurality of nodes collide, network energy consumption and communication time delay caused by data retransmission are increased, and the transmission efficiency of the network is reduced.
At present, most of routing algorithms considering interference problems are from two angles of power control and node degree. The power control type routing algorithm constructs a proper topological structure by reducing the communication power of the nodes so as to reduce the interference in the network, however, the method can lead the topological structure of the network to be sparse, the communication distance between the nodes is too long, the path is possibly disconnected, the fault tolerance of the sparse network structure is weak, the failure or death of part of the nodes can lead to the disconnection of the network, namely, the routing algorithm does not consider two optimization targets of energy efficiency and network fault tolerance at the same time when focusing on reducing the network interference.
Another type of interference control routing algorithm uses the node degree as a relay selection index, and the more the number of neighbor nodes of the current node is, the greater the possibility and degree of interference are, so as to reduce transmission interference. However, at some point, not all nodes within the interference area of the current node will interfere with that node, and only those transmitting simultaneously will interfere with that node at that point. In the event-triggered wireless sensor network, the neighbor nodes which are not triggered are in a dormant state and do not participate in data transmission, and the interference suffered by the nodes is defined simply by the number of surrounding nodes and is not very accurate, so that the interference problem needs to be considered again.
Disclosure of Invention
The invention aims to solve the technical problem of providing a routing method based on multi-source path interference optimization under multi-event triggering, which can ensure the reliability and instantaneity of multi-event data transmission and reduce the communication interference and energy loss among multiple paths, thereby improving the transmission efficiency of a network and prolonging the service life of the network.
The technical scheme adopted for solving the technical problems is as follows: the routing method based on multi-event triggering multi-source path interference optimization comprises the following steps:
(1) Network initialization: the node obtains the minimum hop count from the sink node and the ID of the upper node through the periodical broadcast data packet of the sink node and the relay forwarding of the node, and divides the network into a hierarchical gradient topological structure; defining other event occupying nodes in the communication range of the neighbor node as heterogeneous interference nodes of the node; dividing the nodes into a free state, an occupied state, a potentially interfering state and a dead state;
(2) Clustering strategies based on multiple event triggers: when different events occur, the node which detects the event in the trigger area is activated; all activated nodes in a single event triggering area are regarded as a cluster, the node with the highest energy is selected from all the activated nodes to be used as a cluster head node, and other nodes are used as periodic acquisition event information of member nodes in the cluster and are transmitted to the cluster head node in a single-hop mode;
(3) Candidate relay selection based on an interference avoidance mechanism: the cluster head node is used as a source node, the sink node is used as a destination node, the states of the nodes and the hop count level are used as constraint conditions, invalid neighbor nodes in occupied states, potential interference states and death states are eliminated, and nodes in free states in the upper nodes are selected to be used as candidate relays; if the neighbor node in the free state does not exist, selecting the node in the potential interference state in the upper node as a candidate relay;
(4) Relay election based on interference sensitivity: when the candidate relays are all nodes in a free state, the node residual energy is used, the node distance is used as a relay election probability objective function, and the candidate relay with the largest function value is selected as the next hop node; when the candidate relay is a node in a potential interference state, introducing interference sensitivity to evaluate the interference strength of other event transmission to the candidate relay, constructing a relay election probability objective function by using the node residual energy, the node distance and the interference sensitivity, and selecting the candidate relay with the largest function value as a next hop node;
(5) And updating the node state in the next hop relay node routing information table to be occupied, and then starting data transmission.
The node in the free state is not triggered by an event and is not used as a relay node in the data transmission process, and the neighbor node of the node is not used as a relay node of a transmission link; the node in the occupied state refers to a relay node which is selected as a data transmission link after the event triggering; the node in the potential interference state refers to a relay node with a neighbor node in a communication range as a certain event data transmission; the dead node refers to a node which cannot bear the task of data transmission.
And when other events occupying nodes in the communication range of the neighbor node are defined as the heterogeneous interference nodes of the nodes, the ID marks of the heterogeneous nodes, the lengths of data packets of the events to be transmitted and the signal interference intensity are defined.
The step (3) specifically comprises the following steps: the node i sends a routing request to a neighbor node j in a transmission radius, wherein the routing request comprises the ID of the current node, the hop count from the sink node and the length of a data packet to be transmitted; after receiving the routing request, the neighbor node j updates the state information of the node i in the routing table into an interference state, and adds the ID number of the node i, the length of the data packet to be transmitted of the node i and the received signal strength; the neighbor node j replies a response to the node i, wherein the reply response comprises the ID of the node j, the information of the heterogeneous interference node, the node state and the residual energy; and after receiving the reply response, the node i determines a candidate relay according to the reply response.
In the step (4), when the candidate relays are nodes in a free state, the relay election probability objective function
Wherein E is j Residual energy for candidate neighbor node j, +.>
Average residual energy, d, for all candidate neighbor nodes j Is the distance between the candidate neighbor node j and the current node, d opt For the optimal relay distance, alpha and beta are weight coefficients of node residual energy and node distance indexes respectively.
In the step (4), when the candidate relay is a node in a potentially interfering state, the relay election probability objective function
Wherein E is j Residual energy for candidate neighbor node j, +.>
Average residual energy, d, for all candidate neighbor nodes j Is the distance between the candidate neighbor node j and the current node, d opt IS for the best relay distance (i,j) For interference sensitivity +.>
Generating probability for interference of kth event transmission link to link (i, j), RSSI k For the interference intensity of the kth event to the link (i, j), α, β and η are weight coefficients of node residual energy, node distance and interference sensitivity, respectively.
The optimal relay distance
Wherein,,E Telec and E is Relec The energy consumption is the basic energy consumption of node sending and receiving respectively, epsilon is the energy consumption coefficient of the transmitting power consumption circuit, and gamma is the channel attenuation factor of wireless transmission.
And (5) adjusting the transmitting power of the node according to the received signal strength of the node when the data is transmitted.
Advantageous effects
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects:
firstly, the method is suitable for the large-scale wireless sensing network based on multi-event triggering, and nodes which do not participate in data collection and transmission in the network are all in a dormant state, so that the energy loss of the network is greatly reduced.
Secondly, the invention designs an interference avoidance mechanism aiming at the problems of transmission interference and load balancing in the multi-event data transmission process, all nodes in the network are divided into four states of free, potential interference, occupation and death, in the candidate relay election process, the nodes in the occupied and potential interference states are eliminated according to the state information of the nodes, the free nodes in the upper nodes are selected as the candidate relays of the next hop, the mechanism can effectively avoid the problems of conflict interference and overload load caused by the simultaneous receiving and transmitting of different transmission link information by a single node, and meanwhile, the space distance between the nodes is larger than the communication interference distance, so that the mutual noninterference between different transmission links is caused, and the transmission efficiency is improved.
In addition, the invention provides the interference sensitivity as an evaluation index of the relay election function, the probability of interference generated by other event links to the candidate links and the interference intensity are used for measuring the interference intensity of other event links to the candidate links, and the transmission efficiency is poor as the interference suffered by the transmission links with high interference sensitivity is larger, the link quality is poorer at the moment. By introducing the interference sensitivity, the probability and the intensity of interference generated among different links can be effectively reduced, the interference conflict problem caused by channel competition among transmission links is relieved, and the efficiency of data transmission is improved.
Drawings
FIG. 1 is a flow chart of an embodiment of the present invention;
FIG. 2 is a schematic diagram of a state of a node in an embodiment of the invention;
FIG. 3 is a schematic diagram of event triggered clustering in an embodiment of the present invention;
FIG. 4 is a flow chart of information collection based on multiple event triggering in an embodiment of the invention;
fig. 5 is a flowchart of candidate relay selection based on an interference avoidance mechanism in an embodiment of the present invention;
FIG. 6 is a schematic illustration of an anomaly empty set in an embodiment of the invention;
FIG. 7 is a flowchart of a relay election strategy based on interference sensitivity in an embodiment of the invention;
FIG. 8 is a simple linear model schematic;
fig. 9 is a schematic diagram of a protocol interference model.
Detailed Description
The invention will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention. Further, it is understood that various changes and modifications may be made by those skilled in the art after reading the teachings of the present invention, and such equivalents are intended to fall within the scope of the claims appended hereto.
The embodiment of the invention relates to a routing method based on multi-source path interference optimization under multi-event triggering, wherein a network applied by the method consists of a plurality of isomorphic sensor nodes and a Sink node, the sensor nodes have fixed positions and same calculation and communication capacities, and all the nodes are in a dormant state when no event occurs, as shown in fig. 1, and the method comprises the following steps:
s1 network initialization
Node information of the network is first initialized. The node obtains the minimum hop count from the Sink node and the ID of the upper node through the periodical broadcast data packet of the Sink node and the relay forwarding of the node, thereby dividing the network into a hierarchical topological structure. In addition, to better describe interference collision between different links, network nodes in sleep state are divided into four states of Free (Free), occupied (occupied), potential-interference (Potential-interference) and Death (Death). Meanwhile, when the neighbor node of a certain node is in the communication interference range of other event transmission links, the data receiving and transmitting of the neighbor node can be interfered by other link transmission, and the interference degree is related to the data quantity to be transmitted of the node under other event transmission. Thus, other event occupying nodes within the communication range of the neighbor node are defined as heterogeneous interference nodes of the node. In the network initialization stage, all node states are in free states, and the heterogeneous interference node information set is an empty set.
Hop count hop of node i from Sink node i The information and the upper node information are determined by a data packet broadcast and transmitted by the Sink node. The specific implementation steps are as follows:
the Sink node first broadcasts a packet (ID, hop=0), where hop represents the number of hops from the Sink node. If a certain node receives the packet and the hop count is not set, setting the hop count of the node to hop=hop+1 according to the hop count in the data packet and storing the ID information of the transmitting node. And then continues to broadcast a packet (ID, hop) to its own neighbor nodes. When node i receives the packet (hop) from other node j j ) If hop j ＜hop i -1, node i updates its hop count to hop j +1, while updating upper node information again, if hop j ＝hop i -1, node i hops are unchanged and the node ID information is sent in the data packet is saved. Repeating the above steps continuously broadcasts a packet (hop) i ) And giving the neighbor until all nodes obtain the minimum hop count of the Sink node, no data packet needs to be transmitted in the network, and finally, restoring the dormancy state after the hop count information and the upper node information are stored by the nodes. The network can be divided into a hierarchical topology by the minimum number of hops from the node to the Sink node. Considering that node death can cause the minimum hop count and path from the node to the Sink node to change, the Sink node periodically repeats the broadcasting process to update the topology of the network in real time.
In this embodiment, the node State is divided into free State, occupied State, potential interference State and death State, the State diagram is shown in fig. 2, and specific setting rules are as follows:
A. free state: the method is not triggered by an event, is not used as a relay node in the data transmission process, and is not used as a relay node of a transmission link in the neighbor nodes.
B. Occupancy state: the event trigger has been selected as a relay node in the data transmission link for transmitting the collected information.
C. Status of potential interference: the neighbor nodes exist in the communication range and serve as relay nodes for transmitting certain event data, event information sent by other event transmission nodes is received with a certain probability, and the nodes which can be interfered by other event transmission can be obtained.
D. Death state: when the node energy is lower than a certain threshold value, the node is defined as dead, and the task of data transmission cannot be born.
The heterogeneous interference node is an occupied node of other event transmission links in the communication range, and all nodes in the communication range are in a potential interference state under the influence of the heterogeneous interference node. And considering that different heterogeneous interference nodes have different interference strengths on nodes with different distances in a communication area due to different interference distances and different data amounts to be transmitted. The information table of the heterogeneous node is defined to include the ID flag of the heterogeneous node, the length of the data packet of the event to be transmitted and the signal interference intensity, and the information is set as shown in table 1.
Table 1: heterogeneous node information table
| Sign mark | Meaning of the following description |
| ID | Heterogeneous interfering node identification |
| S (i,j) | Data packet length to be transmitted by heterogeneous interference node |
| RSSI (i,j) | Signal interference strength of heterogeneous interference node |
S2 clustering strategy based on multi-event triggering
After initializing the network, the nodes are in a dormant state, and when different events occur, the sensor nodes which detect the events in the trigger area are activated. All the active nodes in the single event triggering area are regarded as a cluster, the node with the highest energy is selected from all the active nodes to be used as a cluster head node, and the rest nodes are used as periodic acquisition event information of the member nodes in the cluster and are transmitted to the cluster head node in a single-hop mode.
As shown in fig. 4, after an event is triggered, the node that perceives the event information is activated, assuming that the single event trigger area is small and all active nodes within the area are at the same level of gradient. All active nodes in a single trigger area are considered as one cluster set, and a cluster schematic diagram is shown in fig. 3. The specific process of event-triggered clustering is as follows:
first, cluster head node election is carried out. And broadcasting self IDs and residual energy information to surrounding nodes by all the active nodes in the event triggering area, and confirming the ID number of the event active node with the highest residual energy from the broadcasting information, wherein the active node is used as a cluster head node, and the rest active nodes are used as common nodes. The cluster preference probability formula is:
MaxE rest (i) Current event cluster head node
Wherein E is res (i) The remaining energy of the node is activated for the i-th candidate.
After the cluster head node is selected, the rest active nodes are member nodes in the cluster. The cluster member nodes periodically collect event information and send the information to the cluster head nodes in a single-hop mode, and the cluster head nodes fuse the received data.
S3 candidate relay selection based on interference avoidance mechanism
After information of different events is converged to a cluster head node, the cluster head node is used as a source node, a Sink node is used as a destination node, and next-hop data transmission relay is reasonably selected to construct an interference-free multi-source transmission link. In order to avoid the interference among link transmission and the load balancing problem, an interference avoidance mechanism is designed, the states of nodes and the hop count level are used as constraint conditions, invalid neighbor nodes in occupied states, potential interference states and dead states are eliminated, and nodes in free states in upper nodes are selected to be used as candidate relays. When the triggering events are more or the triggering events are close to the Sink node area, if no neighbor node in a free state exists, selecting a node in a potential interference state in the upper node as a candidate relay.
In this step, transmission interference with other links is taken as a consideration, and according to the principle that communication links at a relatively long distance cannot generate interference or generate very small interference, nodes which are completely disjoint and have a distance between links greater than the communication interference distance are selected as candidate transmission relays. The interference avoidance mechanism is shown in fig. 5, and the specific implementation process is as follows:
first, node i transmits power P t And sending a route Request to the neighbor nodes in the transmission radius. The Request data packet contains the ID of the current node and hop count hop from the current node to the sink node i Length S of data packet to be transmitted (i,j) . The neighbor node j receives the Request data, and the signal receiving strength at the moment is RSSI (i,j) . The node i is a heterogeneous interference node of the neighbor node, the neighbor node updates State (j) information in a routing table to be an interference State, and an ID number of the node i and the length S of a data packet to be transmitted by the node are added (i,j) Received signal strength RSSI (i,j) A list of heterogeneous interfering nodes to nodes.
To avoid routing loops during routing and to minimize transmission hops, next hop relay nodes hop from sink nodesThe number should be smaller than the current node. Therefore, hop count from sink node is hop i After the superior neighbor node of-1 receives the Request data packet, the neighbor node in the non-dead state transmits power P t Replying a response data packet to the current node i, wherein the response data packet comprises an ID number and information of a heterogeneous interference node
Node state residual energy E j Information.
And after receiving the response data packet, the node determines a candidate relay set according to the return information. When the triggering events are less or the triggering events are far away from the Sink node area, the communication overlapping areas of different links are smaller, the interference among the links is smaller, and at the moment, the adjacent nodes in the free state are selected as candidate relays, so that the path nodes of the different source nodes are completely disjoint, the distance among the different path nodes is larger than the communication interference distance, the interference is completely avoided, and the overlarge network load of a single node is avoided.
When the triggering events are increased or the triggering events are close to the Sink node area, the data transmission paths triggered by different events have larger overlapping areas, the nodes in occupied and interference states are increased, and the neighbor nodes in free states may not exist in the neighbor nodes replying to the message, as shown in fig. 6. At this time, the nodes in all the potential interference states are selected as candidate relay nodes.
After the node i determines a candidate relay set according to node state constraint, storing candidate neighbor node information and response signal receiving power P in a candidate set response data packet r And forming a candidate adjacent point information table.
S4 relay election based on interference sensitivity
After the candidate relay nodes are determined, a relay election probability objective function F (N) is constructed to select the next hop relay. When the candidate relay sets are all adjacent nodes in a free state, selecting node residual energy, and selecting a node with large node residual energy and closest to the optimal relay distance as a next-hop node, wherein the node distance is used as a relay election function index; when the candidate relay is concentrated into the nodes in the potential interference state, heterogeneous interference nodes exist in the communication range, namely, the data transmission and the reception of the data can be interfered by the data transmission of a plurality of different events, so that one interference sensitivity is introduced to evaluate the interference intensity of other event transmission to the candidate relay nodes. And comprehensively considering the node residual energy, the node distance and the interference sensitivity to construct a relay election probability function, and selecting the candidate relay with the largest function value as the next hop relay node.
As shown in fig. 7, under the condition that the triggering event is less or far away from the Sink node area, after the step of selecting the candidate relay, the candidate relay nodes are free state nodes, so that complete avoidance of interference is realized, data collision caused by simultaneous data receiving and transmitting of the same node and communication interference of other event transmission links do not exist, and node residual energy E is selected on the basis of the free state nodes j Node distance d j As a selection index of the relay node, network energy consumption of data transmission is minimized, namely a relay selection probability function of the jth node is as follows:
wherein E is j Remaining energy for candidate neighbor node j,
average residual energy, d, for all candidate neighbor nodes j Is the distance between the neighbor node j and the current node, d opt For the optimal relay distance, alpha and beta are weight coefficients of node residual energy and node distance indexes respectively.
(1) For the objective function F (N j ) In (a) and (b)
The calculation formula is as follows:
(2) For the distance d between the adjacent node j and the current node i j The present embodiment uses the received signal power P r To measure, distanceThe following relation is satisfied with the signal receiving power:
γlgd j ＝lg(P t )-lg(P r )
where γ is the channel attenuation factor of the wireless transmission.
(3) For the optimal relay distance d opt The formula is satisfied:
wherein E is Telec And E is Relec The energy consumption is the basic energy consumption of node sending and receiving respectively, epsilon is the energy consumption coefficient of the transmitting power consumption circuit, and gamma is the channel attenuation factor of wireless transmission. The deduction process is as follows:
the first-order radio energy consumption model can know that the energy consumed by the node to send the lbit data to the node with the distance d is:
E Tx (l,d)＝l(E Telec +εd γ ),2≤γ≤4
the energy consumption of the node for receiving the lbit data is as follows:
E Rx (l)＝lE Relec
wherein E is Telec And E is Relec The energy consumption is the basic energy consumption of node sending and receiving respectively, epsilon is the energy consumption coefficient of the transmitting power consumption circuit, and gamma is the channel attenuation factor of wireless transmission.
Assuming that the distance between the source node and the destination node is D, when the distances between all hops are D, the source node passes through
The energy consumption and minimum of each node in the jump line data transmission to the destination node are called the distance d as the optimal relay distance of the node transmitting the data to the sink node, < >>
Is the optimal hop count.
Assuming that the distance from the current node to the sink node is D, a simple linear model is shown in FIG. 8, and the total network energy consumption of the node transmitting the lbit data to the sink node is
The above method can obtain the d derivative
Let E' D (d) Available =0
Pair E D (d) Can be obtained by carrying out secondary derivation
As can be seen from the above, E D (d) 0 is constant, thus E' D (d) Is a monotonically increasing function, let E' D (d) D to solve for=0 is E D (d) Minimum optimal relay distance d opt I.e. the optimal relay distance of the next hop of the node is obtained after knowing the inherent power consumption parameter of the node and the attenuation factor of the wireless environment is
In order to prolong the service life of the path, the energy consumption of the network is saved as much as possible, and the node with more residual energy of the node is selected as much as possible to be used as the next hop relay, and the specific deduction analysis shows that the energy consumption value of the network is minimum under the optimal relay distance, so that the distance between the next hop relay node and the current node is close to the optimal relay distance as much as possible.
Under the condition that triggering events are increased or the triggering events are close to Sink node areas, candidate relay nodes are in a potential interference state, occupied nodes for data transmission of other events exist in the communication range of the candidate relay nodes, channel resource competition exists between the candidate relay nodes and other event transmission nodes, and data is carried out simultaneously when the candidate relay nodes and the other event transmission nodes compete with each otherInterference collision occurs during transmission (see fig. 9), and the interference strength and the probability of interference generation are related to the size of the link transmission data packet. The larger the traffic of the interfering link, the longer the communication time of its data transmission, generating the probability of interference collision P i (j) The larger the interference strength, the stronger its link quality. Therefore, the candidate neighbor node IS introduced as the interference sensitivity IS in the next hop relay (i,j) As a relay selection index, if a node with the lowest probability of being interfered and the lowest strength is prioritized as a next-hop relay node, the relay election probability objective function F (N j ) The method comprises the following steps:
wherein, alpha, beta and eta are respectively the node residual energy, the node distance and the weight coefficient of interference sensitivity.
Interference sensitivity IS (i,j) The influence degree of the current link (i, j) by other event transmission links in the multi-source data transmission process is reflected, the interference probability and the interference intensity of other event transmission are comprehensively considered, and the specific formula is as follows:
in the method, in the process of the invention,
generating probability for interference of kth event transmission link to link (i, j), RSSI k The interference strength to link (i, j) for the kth event.
(1) Probability of interference
The transmission links of different events have a certain conflict when transmitting data in the same time slot of the same channel, therefore, the probability of interference conflict of two interference links is defined as that the link (i, j) occupies the channel time period tau (i,j) During which at least one other event link node transmits packets to reach the nodePoint j. The specific calculation process is as follows:
assuming that the packet arrival process conforms to a poisson distribution process, wherein the probability density of the poisson distribution is
Where λ is the total number of packets expected to be received in a certain time T, i.e. the number of packets sent by the source node. k is the total number of data packets actually received by the node in time T.
S (i,j) For the length of the data packet to be transmitted for the current link (i, j), r (i,j) For the data transmission rate of link (i, j), node N i Relay node N to its next hop j The transmission time required for transmitting the data packet is
Another event transmission interfering node k is in the time period tau (i,j) The probability that a data packet arrives at node j while transmitting data is obtained from the probability density formula of poisson distribution
Wherein S is k The number of packets is sent for the nuisance event.
The probability of interference collision between two interfering links is that the link (i, j) occupies the channel time period tau (i,j) During which at least one data packet transmitted by the other event link node k arrives at node j. The probability of interference is
(2) RSSI for interference strength k The data transmitted by other event transmission links are affected by the link quality and transmission distance, and have different current nodesThe interference degree, therefore, the signal receiving strength of the current node receiving the heterogeneous interference node is taken as the interference strength of the kth event to the link (i, j).
S5 power control and data multi-hop transmission
After determining the next hop relay, updating the node state in the next hop relay node routing information table to be occupied, and then starting data transmission. In order to reduce the energy consumption loss caused by the transmission power redundancy, the service life of the path is prolonged, and the transmission power of the node is adjusted according to the received signal strength of the node. And the network repeats the steps S3 and S4 until all relay nodes in the path are determined, and then each hop relay transmits the event triggering information to the Sink node with optimal transmitting power.
In this step, the optimal transmit power is defined as: p (P) (i,j) ＝P t -(P r -P min )+ΔP。
Wherein P is t Signal transmission power, P, for transmitting response packets for neighbor nodes r Signal receiving power for receiving data packet sent by adjacent node for node, P min For the minimum signal strength of the data packet which can be correctly received, Δp is not less than 0, which is a fault-tolerant numerical term, if the energy consumption is to be reduced, the numerical value can be reduced, and if the transmission of the data packet is to be more reliable, the numerical value can be increased appropriately. Adjusting the transmit power according to the formula may reduce energy waste due to transmit power redundancy when transmitting data packets.
Compared with other routing algorithms, the method and the device can effectively solve the interference conflict problem in multipath parallel transmission data, improve the transmission efficiency of the network, and simultaneously can better balance the network energy consumption of the nodes, save the energy consumption of the network, improve the service life of the network and have better effects on network throughput, transmission delay and network energy consumption for the network energy consumption caused by a large amount of data generated in the multi-event transmission process.
Claims (5)
1. A routing method based on multi-event triggered multi-source path interference optimization, comprising the steps of:
(1) Network initialization: the node obtains the minimum hop count from the sink node and the ID of the upper node through the periodical broadcast data packet of the sink node and the relay forwarding of the node, and divides the network into a hierarchical gradient topological structure; defining other event occupying nodes in the communication range of the neighbor node as heterogeneous interference nodes of the node; dividing the nodes into a free state, an occupied state, a potentially interfering state and a dead state; the node in the free state is not triggered by an event and is not used as a relay node in the data transmission process, and the neighbor node of the node is not used as a relay node of a transmission link; the node in the occupied state refers to a relay node which is selected as a data transmission link after the event triggering; the node in the potential interference state refers to a relay node with a neighbor node in a communication range as a certain event data transmission; the node in the death state refers to a node which cannot bear a data transmission task;
(2) Clustering strategies based on multiple event triggers: when different events occur, the node which detects the event in the trigger area is activated; all activated nodes in a single event triggering area are regarded as a cluster, the node with the highest energy is selected from all the activated nodes to be used as a cluster head node, and other nodes are used as periodic acquisition event information of member nodes in the cluster and are transmitted to the cluster head node in a single-hop mode;
(3) Candidate relay selection based on an interference avoidance mechanism: the cluster head node is used as a source node, the sink node is used as a destination node, the states of the nodes and the hop count level are used as constraint conditions, invalid neighbor nodes in occupied states, potential interference states and death states are eliminated, and nodes in free states in the upper nodes are selected to be used as candidate relays;
if the neighbor node in the free state does not exist, selecting the node in the potential interference state in the upper node as a candidate relay;
(4) Relay election based on interference sensitivity: when the candidate relays are all nodes in a free state, the node residual energy is used, the node distance is used as a relay election probability objective function, and the selection function value is the largestAs a next hop node; when the candidate relay is a node in a potential interference state, introducing interference sensitivity to evaluate the interference strength of other event transmission to the candidate relay, constructing a relay election probability objective function by using the node residual energy, the node distance and the interference sensitivity, and selecting the candidate relay with the largest function value as a next hop node; when the candidate relays are nodes in a free state, the relay election probability objective function
Wherein E is j The residual energy of the candidate neighbor node j is E, the average residual energy of all the candidate neighbor nodes is d j Is the distance between the candidate neighbor node j and the current node, d opt Alpha and beta are weight coefficients of node residual energy and node distance indexes respectively for the optimal relay distance; when the candidate relay is a node in a potentially interfering state, the relay election probability objective function +.>
Wherein E is j The residual energy of the candidate neighbor node j is E, the average residual energy of all the candidate neighbor nodes is d j Is the distance between the candidate neighbor node j and the current node, d opt IS for the best relay distance (i,j) For interference sensitivity +.>
P i k (j) Generating probability for interference of kth event transmission link to link (i, j), RSSI k For the interference intensity of the kth event to the link (i, j), alpha, beta and eta are respectively the weight coefficients of node residual energy, node distance and interference sensitivity;
(5) And updating the node state in the next hop relay node routing information table to be occupied, and then starting data transmission.
2. The routing method based on multi-event triggered multi-source path interference optimization according to claim 1, wherein defining the node occupied by other events in the communication range of the neighbor node as the heterogeneous interference node of the node includes defining an ID flag of the heterogeneous node, a packet length of the event to be transmitted, and a signal interference strength.
3. The routing method based on multi-event triggered multi-source path interference optimization of claim 1, wherein the step (3) specifically comprises: the node i sends a routing request to a neighbor node j in a transmission radius, wherein the routing request comprises the ID of the current node, the hop count from the sink node and the length of a data packet to be transmitted; after receiving the routing request, the neighbor node j updates the state information of the node i in the routing table into an interference state, and adds the ID number of the node i, the length of the data packet to be transmitted of the node i and the received signal strength; the neighbor node j replies a response to the node i, wherein the reply response comprises the ID of the node j, the information of the heterogeneous interference node, the node state and the residual energy; and after receiving the reply response, the node i determines a candidate relay according to the reply response.
4. The routing method based on multi-event triggered multi-source path interference optimization of claim 1, wherein the optimal relay distance
Wherein E is Telec And E is Relec The energy consumption is the basic energy consumption of node sending and receiving respectively, epsilon is the energy consumption coefficient of the transmitting power consumption circuit, and gamma is the channel attenuation factor of wireless transmission.
5. The routing method based on multi-event triggered multi-source path interference optimization of claim 1, wherein the step (5) adjusts the transmit power of the node according to the received signal strength of the node when transmitting data.
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