Study on the Mobile Ad Hoc Network Integration OLSR Protocol.doc

1、1Study on the Mobile Ad Hoc Network Integration OLSR ProtocolAbstract. In recent years， Mobile Ad Hoc Networks has been increasingly be concerned about. Many applications for the position of nodes have a strong dependence on the location of the node， which can greatly reduce the complexity of the ap

2、plication of the algorithm， but also improve the overall performance of the network. This paper analyzes the RTS / CTS way of background， the meaning and impact of its wireless network performance， and proposes a Mobile Ad Hoc Networks calculate the distance between nodes， and the algorithm depends

3、on the physical layer model and related theories of algorithm design framework and implementation process. Key words： Ad Hoc， RTS/CTS2， Path attenuation model， Integrated OLSR agreement， Routing 1. Introduction In recent years， Mobile Ad Hoc Networks has drawn increasing attention. In particular， it

4、 is because of the strong dependence of the applications for the position of node localization in Mobile Ad Hoc Networks. However， many of the 2existing network protocols cannot provide satisfactory node positioning technology， which is very limited to the application. 2. RTS / CTS Control Mode 2.1

5、Background IEEE 802. 11 are a wireless LAN physical layer and MAC layer protocol， which provides a DCF （Distributed Coordination Function） work method. 802.11DCF （Distributed Coordination Function） using CSMA / CA （Carrier Sense Multiple Access with Collision Avoidance） technology for preventing int

6、er-node conflict. However， due to not simultaneously transmit data and the listener channel state cannot be used with Collision Detection CSMA / CD access channel. As the DCF works of supplement， PCF provides conflict-free， real-time business service in the network， but need to configure an access p

7、oint AP also more complex， so few applications. Even with the work of the 802.11 protocol DCF CSMA / CA mechanism cannot be in Mobile Ad Hoc Networks completely solve the hidden terminal problem 2. As shown in Figure 1， Figure circle indicates the transmission range of the nodes， because of the limi

8、ted range of communication nodes A and C phase for B 3hidden terminal to each other. If the nodes A and C at the same time or within similar time in the Node B Transmission data is generated in the Node B conflict， this is a hidden terminal problem is generated. 2.2 RTS / CTS Control Mode Overview T

9、he DC F has two ways to access technology work. The source node sends a packet only when its correct reception confirmation message packet （ACK） to the destination node is sent successfully. Another hidden terminal problem in order to solve the wireless network 3， based on the RTS / CTS handshake wa

10、y access strategy. RTS / CTS handshake mechanism to avoid conflict of principle is shown in Figure 2. When the node A to the node B transmit data， the node A in accordance with the CSMA mechanism competition radio channel when their access to the usage rights of the channel， the first send an RTS fr

11、ame to the node B， and node B receives the frame， which followed to Node A returns a CTS frame， after the successful exchange of RTS / CTS frame sequence A further node B Transmission actual data frame. RTS / CTS exchange the frame， node A is not only notify its neighbors， but also the use of the CT

12、S frame at the same time informs the neighbors of Node Bto eliminate the C nodes become possible potential hidden 4terminal. 2.3 RTS / CTS Control on the Wireless Network Performance Impact Analysis RTS / CTS control method will affect the performance of the wireless network. First， the transmission

13、 of the RTS frame is based on the CSMA / CA mechanism， RTS frame makes the conflict still exists； Secondly， the length of the RTS frame is 20 bytes， in order to allow more neighbor nodes perceive the presence of the RTS frame， the transmitting node using the minimum The rate of transmission， the RTS

14、 frame requires 8 time slots （20 us / slot） for transmission， the time overhead cannot be ignored； Finally， if the potential hidden terminal back off counter value is less than eight time slots， the guide to the RTS / CTS frame exchange during the conflict， will further reduce the network throughput

15、， thus affecting the overall network performance. Between nodes in a multi-hop wireless network， with the hidden terminal appears the probability of collision will be significantly increased. Even if the use of RTS / CTS handshake mechanism cannot completely solve the hidden terminal problem， especi

16、ally equipped with a high-speed wireless equipment nodes， in order to be able to successfully receive the packet 5data， you must use a higher signal-to-noise ratio （SINR） ， This will make the network even more prominent 4. Before sending the actual business packet data， the sending node can know its

17、 near node distribution， you can advance to take appropriate measures to reduce the interference of nodes bring better and found hidden terminal and improve the node the success rate on the packet data to send business. Herein， the node sending business packet data on the front， first calculate the

18、node and its （1-hop or 2 hops） the distance between the neighbor nodes， using the distance information to judge the existence of the sending node and receiving node hidden terminal， and Rate nearby nodes to this node brought about by interference. 3. Algorithm Uses Physical Layer Model As measured i

19、n accordance with the following method 4.The Calculation of the Distance Between the Wireless Network Nodes The physical layer of the wireless network， when the nodes within the receiver receives a business packet data， the received signal strength of the packet data Can be calculated， when to take

20、the set The value of the later， The value can also be calculated， can be obtained according to Equation 1 6Equation 4 When the node receives the packet data of a business， the distance between the Physical layer entity computing nodes ， this distance of the current node and directly send the distanc

21、e data between the nodes of the service packet （packet during transmission may pass through a multi-hop）. Related data structure is created in the layer used to save the information， the algorithm uses the distance information in the table to the temporary storage between these nodes， as shown in Ta

22、ble 2， the information stored in the table with the IP address of the direct transmission node （Direct Sender IP） ；distance between nodes（ ） ， Its value can be by using the formula 4， calculated from the units of meters （m） ； creation time （Time ） represents the time of the line information is inser

23、ted； modification times （Modified T in s） indicate that the record in a certain interval. Be modified within the number of times in the range， the more the number of changes that the movement of the node is relatively frequent. Distance information recorded in the above table， it should be sent to t

24、he upper layer protocol of the wireless network， including the MAC layer and the network layer， but not every node receiver received traffic packet data are 7transmitted to the upper distance information. The added distance information， the routing table of the network layer， the node can use these

25、distance information to better select the path， to improve the success rate of the transmission. The specific implementation of this algorithm must also seriously consider： First， the problem of interference from other nearby nodes and ambient noise， interference will make the accuracy of calculatio

26、n of the distance between nodes reduce. Secondly， the distance information from the physical layer returns to the upper layer protocol used by time interval value size. If the value is too small， the routing table of the upper layer of course be immediately updated， but will increase the load on the

27、 node where the contrary， the routing table of the upper layer cannot be immediately updated. Furthermore， the distance information sent to its neighbors using the time interval value size. If the value is too small wireless network load increases， the performance degradation. One method is to creat

28、e a new packet format type， using it to encapsulate the distance information， and then sends it to the upper layer protocol in the physical layer. Another method is using OLSR routing protocol HELLO message， the insertion distance information in the message， and then transfer it to 8the upper layer

29、protocol， this article uses two kinds of methods. 5. Integrated OLSR Protocol Design Calculated the distance between the wireless networks nodes need to be integrated into the routing protocols， routing protocols， the distance between nodes can use the information to better design routing algorithm.

30、 Integrated wireless network node distance information， the paper to the OLSR protocol of the wireless network integration node distance method， referred to as integrated OLSR protocol support multiple routing protocols in Wireless Ad Hoc Networks. The OLSR protocol type messages by periodically bro

31、adcasting HELLO provide node discovery mechanism of its neighbor nodes. This message is only sent to nodes within a jump， when the node receives the message can be perceived around neighbors. The current node is calculated from the inter-node distance as HELLO type message piggybacking data is trans

32、mitted to a neighbor node. The neighbor node receives such a message， you can use the distance information to optimize the routing algorithm to achieve better algorithm. In order to preserve the distance information， you need to change the OLSR protocol of the neighbors node set， link set topology i

33、nformation table and routing table structure to make 9it able to node distance information stored in the data collection. Distance between wireless network nodes， on the method of calculation of the information and integrated to the OLSR protocol algorithm is as follows： The node receives traffic pa

34、cket data sent by the transmitting node， is calculated in accordance with Equation 4 （in accordance with a certain time interval） between the current node and the transmitting node distance information. Then， the current node to neighbor nodes broadcast HELLO message piggybacking distance informatio

35、n between nodes； Any node in its neighbor nodes broadcast HELLO packet is received， check whether the package containing the distance information between nodes， and， according to those in the routing table and neighbor table corresponding to the distance information； In order to make the node can kn

36、ow the OLSR routing protocol with the distance between the other nodes， it is necessary to modify the format of a TC message， and so the distance information can spread to the current node of all MPR selector. The transfer of a node in a wireless network will be 10subject to interference from a neig

37、hbor node to meet the relevant requirements of the data transmission in order to enable the transmission condition of the transmitter nodes， select a path with the least interference critical algorithm modified OLSR routing algorithm in the path selection algorithm， the goal is to find a minimum nei

38、ghbor node of the transmitting node in the data transmission of interference， the path with the least number of hops in order to reduce the impact of interference from neighbor nodes for data transmission. The routing algorithm is necessary to meet the requirements of the data packet transmission qu

39、ality， business packet data right on time to meet the target node； want to select a data transfer by the path of least interference. To a certain extent， these requirements and objectives can be achieved in the routing table to add a new item of information （distance between nodes）. 6. Integrated OL

40、SR Protocol Routing Algorithm In order to meet the requirements in accordance with certain requirements of the transmission of data packets， the algorithm modifies the basic OLSR protocol path selection algorithm， a new link is created， we must calculate the distance information with links， and these links information