CN102045809B - Routing method of opportunistic network based on wireless radio frequencies - Google Patents

Abstract

The invention provides a routing method of an opportunistic network based on wireless radio frequencies, which mainly aims at the opportunistic network consisting of a plurality of mobile nodes and is mainly applied to environments such as a school network, a small town network and the like. The routing method includes the following steps of: firstly selecting application scenes of the opportunistic network; then setting a plurality of wireless radio frequency reader-writers in the application scenes; thirdly, setting a communication terminal on the mobile nodes; and finally performing data transmission among the mobile nodes, dividing the network load into two parts, wherein one part of the network load is stored and transferred by relay nodes, the other part of the network load transmits data via wireless radio frequency signals, and the two parts are performed in parallel. The routing method has the advantages of small end to end delay, low network resource requirement, little influence caused by environment factors and the like on the basis of guaranteeing the successful transmission rate of the data.

Description

Opportunistic Network Routing Method Based on Radio Frequency

technical field

The invention relates to a routing method, in particular to a radio frequency-based opportunistic network routing method.

Background technique

Radio frequency technology is a technology that uses radio frequency signals to automatically identify target objects and obtain relevant information. As early as World War II, it showed its prototype in the "identification friend or foe" system that distinguished Allied and Nazi aircraft. At present, major software and hardware manufacturers including IBM, Motorola, Oracle, etc. are conducting research on this technology, and have launched a series of software and hardware products, which are used in logistics management, warehousing systems, expressway toll stations and other aspects of people's daily life. aspect to apply.

The research on opportunistic networks comes from the Interplanetary Internet Project (IPN) supported by DARPA of the US Defense Advanced Research Projects Agency, which is a mobile wireless network in which there is no complete path between the source node and the destination node in most cases. At present, it is gradually applied to biological tracking, campus network, home automation network, urban and rural network and other fields. Due to the characteristics of intermittent connections, high transmission delay, and uneven connections in opportunistic networks, the original TCP/IP protocol cannot establish end-to-end connections, resulting in a large number of packet loss.

In recent years, people have conducted various analyzes on opportunistic networks, and proposed many different routing protocols, but these protocols have some shortcomings, such as some protocols occupy too much network resources, and some protocols The performance of the successful transmission rate or the average delay is not ideal, and some protocols require that the movement of nodes must follow a specific method.

Contents of the invention

The technical problem solved by the present invention is to provide a radio frequency-based opportunistic network routing method that can meet the transmission rate and delay constraint requirements in a dynamically changing network environment, and can reasonably utilize resources such as cache and bandwidth in the network.

The technical solution that realizes the object of the present invention is: a kind of opportunistic network routing method based on radio frequency, comprises the following steps:

Step 1: Select the application scenario of the opportunistic network. The application scenario is a relatively closed environment. There are some mobile entities in this scenario, and some data transmission and sharing need to be carried out between the mobile entities;

Step 2: Set up several wireless radio frequency readers in the above application scenarios. These readers are located in places where mobile nodes are densely populated, and their coverage areas cannot overlap;

Step 3: Set up a communication terminal on the mobile node, the communication terminal includes two interfaces, one is a radio frequency read-write interface, and the other is a traditional wireless network read-write interface;

Step 4: For data transmission between mobile nodes, the network load is divided into two parts, one part of the network load is stored and forwarded through the relay node, and the other part of the network load is transmitted through radio frequency signals, and the two are performed in parallel.

Compared with the prior art, the present invention has the remarkable advantages that: it adopts the way of wireless radio frequency signal and traditional network signal to transmit data in parallel, improves the performance of opportunistic network, and is different from the traditional routing protocol that simply uses wireless network for data transmission In comparison, while increasing the transmission rate, the end-to-end delay is reduced, and the use of network resources is controlled within a reasonable range.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is an application scenario of the present invention.

FIG. 2 is a flowchart of a radio frequency-based opportunistic network routing method according to the present invention.

FIG. 3 is a flowchart of a method for transmitting data packets through a wireless network in the present invention.

Fig. 4 is a flowchart of communication between mobile nodes in the present invention.

FIG. 5 shows the method of transmitting data packets through radio frequency in the present invention.

Fig. 6 is a flowchart of the communication between the mobile node and the reader in the present invention.

FIG. 7 is a comparison of transmission rates between the routing strategy of the present invention and other routing strategies.

Fig. 8 is a delay comparison between the routing strategy of the present invention and other routing strategies.

FIG. 9 is a comparison of resources occupied by the routing strategy of the present invention and other routing strategies.

FIG. 10 is a comparison of the total traffic of the routing strategy of the present invention and other routing strategies.

Detailed ways

With reference to Fig. 1 and Fig. 2, a kind of opportunistic network routing method based on radio frequency of the present invention comprises the following steps:

Step 1: Select the application scenario of the opportunistic network. The application scenario is a relatively closed environment, such as a university campus. In this scenario, there are some moving entities, such as people or vehicles, and some data exchange is required between them. Pass and share. Usually, there is no direct end-to-end path between entities, and the real-time performance of the transmitted data is not very high;

Step 2: Set up a wireless radio frequency reader in the above application scenario. The reader is located in a place where mobile nodes are densely populated, and its coverage cannot overlap;

Step 3: Set up a communication terminal on the mobile node, the communication terminal includes two interfaces, one is a radio frequency read-write interface, and the other is a traditional wireless network read-write interface;

Step 4: Data transmission is performed between mobile nodes, and the network load is divided into two parts, one part of the network load is stored and forwarded through the relay node, and the other part of the network load is transmitted through radio frequency signals, and the two are performed in parallel.

The specific method of dividing the network load is: originally in the opportunistic network, a node will form multiple copies after generating a data packet, and send these copies to several different relay nodes, and then no longer copy the data Packet, all these nodes that store the copy will send the data packet to the destination node after encountering the destination node to complete the data transfer. This is a limited flood routing protocol. Set the number of flooding copies q on the basis of the restricted flooding routing protocol, and divide q into n and m parts after the source node generates data packets, where q=m+n, q>m>0, q> n > 0, in the subsequent point transfer process, n copies are forwarded through the relay node, and m copies are transmitted through radio frequency signals.

In combination with Fig. 3, the specific steps for storing and forwarding a part of the network load of the present invention through the relay node are as follows:

(1) The source node sends n-1 copies to the first n-1 different mobile nodes encountered according to the preset n copies, and keeps one for itself; the source node can also use a binary distribution strategy to carry out Distribution, specifically: when the source node distributes copies for the first time, it will pass half of the number of copies to the relay node, and then each node with the number of copies greater than or equal to 2 will pass half of the number of copies when distributing For other relay nodes, this division strategy can complete the distribution of copies as quickly as possible;

(2) Judging the relay node, if a relay node is the destination node, then complete the delivery of the data packet; otherwise, the n nodes carrying copies will no longer copy the data packet, and any node encounters When reaching the destination node, the data packet is delivered to the destination node to complete the data transfer.

Combined with Figure 4, in the actual environment, there may be multiple data packets to be transmitted during a meeting between any two nodes. Since the contact time of nodes is limited and the data transmission bandwidth is also limited, it is necessary to provide Packets that need to be sent are prioritized. First of all, the two nodes are equal, then either party starts to transmit the data packets with the other party as the destination node, and then the other party starts to transmit the data packets with the other party as the destination node, so that the transmission process of some data packets can be completed as soon as possible. Subsequently, any party starts to transmit data packets to be forwarded to the other party, and then the other party starts to transmit data packets to be forwarded to the other party, thus completing the entire communication process. If the communication between the nodes is interrupted due to the movement of the nodes during this process, the communication process will end and the data packets being transmitted will be discarded.

In conjunction with Fig. 5, another part of the network load of the present invention carries out the specific steps of data transmission through the wireless radio frequency signal as follows:

(a) The mobile node periodically initiates a session request to the reader. If the reader is busy, the mobile node delays 3~5s and initiates the session request again; if the reader is idle, execute step (b), and the reader itself enter a busy state;

(b) The reader sends a response signal and establishes a connection with the mobile node;

(c) The mobile node places a copy of the data packet transmitted by the radio frequency signal in the buffer and instructs the reader to read and write;

(d) The reader/writer reads and writes data from the mobile node, and then completes the reading and writing of a data packet; the reader/writer writes the data packet into the destination node in a subsequent session with the destination node;

(e) The reader-writer and the mobile node are disconnected after reading and writing, the reader-writer enters an idle state, the reader-writer communicates regularly, and distributes m copies of the data packet to m different readers superior.

The communication process between the node and the wireless radio frequency reader is described with reference to FIG. 6 . The mobile node first initiates a session request to the reader. If the reader is in the idle state, it will respond to the request, establish a connection between the reader and the node, and the reader will enter the busy state. If the node does not receive the response signal from the reader, it will initiate a session request again after a delay of 3 to 5 seconds until the connection is established. After that, the reader writes the sequential data packets with the node as the destination node into the specific buffer of the node, and instructs the node to receive them, and completes the delivery process of some data packets. Then the node puts the generated data packets that need to be transmitted through the radio frequency signal into the corresponding buffer in turn, and instructs the reader to read. After the reader finishes reading the content of the node, the node sends a request to end the session, the communication ends, and the reader enters the idle state again.

In the above process, the readers should be evenly distributed in various areas of the entire network, so as to ensure that the mobile node can quickly enter the coverage of the readers at any position in the network. In addition, the coverage radii of the readers should avoid overlapping, which may cause conflicts between readers and cause waste of resources. Only a small number of readers need to be installed in the entire network. On the one hand, this is due to cost considerations. In addition, too many readers can improve performance very little.

The movement of the node is carried out according to a certain movement model. Usually, the node has a destination, and then the node moves to the destination. It can stay at the destination for a certain period of time, and then select a new destination to continue moving.

The mobile node can transmit data with the reader through the radio frequency signal. This data transmission is bidirectional, that is to say, the reader can read data from the mobile node, and can also write data like the mobile node. In this way, during a communication process between the mobile node and the reader-writer, the reader-writer reads the newly generated data from the mobile node, and sends the data for its purpose to the node.

The mobile nodes can communicate with each other, and when the distance between two nodes is less than the coverage radius of the wireless network during the moving process, they can transmit data through the wireless network.

Readers can also communicate with each other. Readers can be seen as fixed infrastructure, so data can be shared among them, but this is not required. A central control system can be arranged, or a certain reader can be responsible for regularly collecting data packets that are not received by the reader, sorting them out, deleting duplicate data packets, and then returning the sorted results for each reader. The data sharing between readers can be transmitted through the wired network, so that the data can be quickly and timely distributed to various areas of the entire network.

When any node generates a new data to be sent, it will transmit data independently through radio frequency and wireless network. In the process of wireless radio frequency transmission, the node is responsible for transmitting a copy of the data packet to the first encountered reader, and then no longer transmits redundant copies through radio frequency signals. The destination node is within the coverage of the reader Within, the corresponding data packet can be obtained from the reader to complete the data transfer. During the transmission process of the wireless network, the node transmits n-1 copies of the data packet (n is related to the scale of the entire network) to the first n-1 different nodes encountered, and keeps one for itself. If the destination node is not encountered during this process, the data packet is no longer copied and forwarded. Until a node carrying the data packet encounters the destination node and sends it to the destination node, the transmission of the data packet is completed.

Nodes interact with readers periodically. If the node is not within the coverage of any reader, the node sends a request to communicate with the reader when the node moves within the coverage of a reader. If the reader is idle at the moment, a response is given to the node, a session connection is established between the two, and the reader enters a busy state. If the reader is busy at this time, the node cannot receive the response from the reader, and the node can delay a few seconds before sending a session request until it gets a response from the reader. Since the session time between each node and the reader-writer only accounts for a small part of the total time of the node, the probability that multiple nodes make session requests to the reader-writer at the same time is very small.

After the node establishes a connection with the reader, the reader first puts the data packet with the node as the destination node in the buffer of the node, and instructs the node to receive it. If the reader has no data to send to the node, or the data has already been received, the node will not receive an acceptance instruction from the reader, and can send its newly generated data in the buffer to wait for the reader to read . After the reader/writer reads the data, it will indicate to the node that the data has been received, and the node can put the next data packet into the buffer. After the reader has read all the data to be transmitted by the node, the node sends a disconnection request to the reader and ends the session with the reader. The reader/writer enters the idle state after receiving the disconnection request.

If the reader is in the process of talking with the node, the node moves out of the coverage of the reader, or any abnormality occurs during the data reading and writing process, the reader and the node will both interrupt the session with the other party , the node can try the session with the reader after a few seconds delay.

When the distance between any two nodes is within the transmission range of the wireless network, wireless communication between nodes can be performed. If more than two nodes are within the same range, only two connections will be established between them. The start of a session can be initiated by any node. The connection between nodes is bidirectional. After one party establishes a connection, two-way data transmission can be performed. However, there is only one-way communication at any time, and both nodes have data packets to send. When sending to the other party, they must be sent sequentially.

During the conversation between the two nodes, the data packets destined for the other party are sent first. Because these data packets are sent to the destination node, they can be discarded after the sending is completed, so that the data transfer can be completed as soon as possible. After that, the packets that need to be forwarded are transmitted. The status between nodes is equal, so the order in which two nodes send and receive is random. When a node tries to send a data packet to another node, it first checks whether the other party agrees to receive the data packet, and if the other party has already received the data packet (via radio frequency or other nodes), then abandon the transmission of the data packet , and then try to send another data packet, otherwise start the transmission of this data packet. After the transmission of a data packet is completed, any party can transmit a new data packet, and if neither party transmits a data packet, the session can be terminated. After the data exchange between the nodes is completed, the session between the nodes ends, and the node that initiates the connection ends the session. If during the transmission process, the distance between two nodes is greater than the wireless transmission distance due to the relative movement of the nodes, the connection between the nodes will be interrupted, and the data packets being transmitted will be discarded.

Each node has a local buffer of a certain size, which stores data packets generated by itself or forwarded by other nodes. When a new data packet is generated, or when a new data packet is received, if the local buffer is full, the node will discard the earliest data packet entering the buffer to find enough space to store the new data packet . For the data packet received for its own purpose, the node will not put it into the local buffer, but directly carry out further processing. If the same packet is received, it is discarded directly.

Below in conjunction with embodiment the present invention is described in further detail:

Example:

The present invention will be described in further detail below in conjunction with a township simulation environment. The area size of the scene is 4km*4km. The area is composed of mobile nodes, reader facilities, roads, and fixed facilities. Mobile nodes are divided into three types: nodes beginning with b represent bus, which run along a fixed road and will stay at the end for a period of time; nodes beginning with c represent car, such nodes can move on the main road , choose a fixed facility as the destination, and make a certain stop at the facility after arriving at the destination; the node starting with p represents a person, this kind of node can move on the main road and the secondary road, and also choose a fixed The facility as the destination, and after arriving at the destination, you can enter the facility to exercise. The various parameter settings of the three nodes are as follows:

Table 1 Parameter settings of three kinds of nodes

As can be seen from Table 1, there are a total of 100 nodes in the whole scene. The total time of the simulation is designed to be 12 hours, of which data packets will be generated according to the probability in the first 10 hours. Theoretically, the total number of data packets in a simulation process is 4000. The size of the packet is 5-100k, which is basically designed to be the size of an email. We set the number of copies of source-determined fog waiting and binary spray waiting to 12, then the number of copies forwarded through the wireless network in the radio frequency-based routing protocol is 6, and the other 6 copies are transmitted from the radio frequency. Set 6 fixed readers, the coverage radius of each reader is set to 150 meters, and the communication speed between the reader and the node is 10 read or write operations per second. At the same time, we implemented the currently popular Epidemic Router (ER), source-determined fog wait (Spray&Wait SW), source-determined binary spray wait (Binary Spray&Wait, BSW), single-copy direct delivery routing (DirectRouter DR) in the above scenarios. ) to compare their performance.

Under the above environment, the simulation data shows that the successful transmission rate of data packets is above 95% (Figure 7), the average delay is within 50 minutes (Figure 8), and the total occupied network resources are below 800M (Figure 9). The total amount of data is below 1800M (Figure 10). The above results show that the strategy proposed by the present invention has high feasibility and rationality.

Claims (1)

1. A radio frequency-based opportunistic network routing method, characterized in that, comprising the following steps: Step 1: Select the application scenario of the opportunistic network. The application scenario is a relatively closed environment. There are some mobile entities in this scenario, and some data transmission and sharing need to be carried out between the mobile entities; Step 2: Set up several wireless radio frequency readers in the above application scenarios. These readers are located in places where mobile nodes are densely populated, and their coverage areas cannot overlap; Step 3: Set up a communication terminal on the mobile node, the communication terminal includes two interfaces, one is a radio frequency read-write interface, and the other is a traditional wireless network read-write interface; Step 4: For data transmission between mobile nodes, the network load is divided into two parts, one part of the network load is stored and forwarded through the relay node, and the other part of the network load is transmitted through radio frequency signals, and the two are performed in parallel; the network The specific method of load division is as follows: on the basis of the limited flood routing protocol, set the number of flood copies q, and divide q into two parts n and m after the source node generates data packets, where q=m+n, 0<m<q, 0<n<q, in the subsequent transfer process, n copies are forwarded through the relay node, and m copies are transferred through radio frequency signals; the part of the network load is stored and forwarded through the relay node The specific steps are: (1) The source node sends n-1 copies to the first n-1 different mobile nodes encountered according to the preset n copies, and keeps one for itself, or the source node uses a binary distribution strategy to distribute ; (2) Judge the relay node, if a certain relay node is the destination node, then complete the delivery of the data packet; otherwise, the n nodes carrying copies will no longer copy the data packet, and any one of the nodes When the destination node is encountered, the data packet is passed to the destination node to complete the data transfer; The specific steps for the other part of the network load to transmit data through radio frequency signals are: (a) The mobile node periodically initiates a session request to the reader. If the reader is busy, the mobile node delays for 3 to 5 seconds and initiates the session request again; if the reader is idle, execute step (b), and the reader itself enter a busy state; (b) The reader sends a response signal and establishes a connection with the mobile node; (c) The mobile node places a copy of the data packet transmitted by the radio frequency signal in the buffer and instructs the reader to read and write; (d) The reader/writer reads and writes data from the mobile node, and then completes the reading and writing of a data packet; the reader/writer writes the data packet into the destination node in a subsequent session with the destination node; (e) The reader-writer and the mobile node are disconnected after reading and writing, the reader-writer enters an idle state, the reader-writer communicates regularly, and distributes m copies of the data packet to m different readers , so that all the m readers can write the data packet to the destination node.

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