A Qos Routing protocol based on AODV

A Qos Routing protocol based on AODV (QOSAODV) is proposed aiming at the problem of the traditional QoS routing protocol which can not be applied perfectly in VANET. The weakness of the AODV routing protocol mechanism and the protocol itself are represented. By the simulation, the effectiveness and feasibility were completely verified. QOSAODV shows the superior performances in effectively lowering the routing broke ratio as well as packet drop ratio significantly, meanwhile, increasing the network throughput and scale.


introduction
At present ,Routing protocol for vehicular ad hoc networks [1] has being hotspot at home and abroad.in order to improve its performance, many routing protocols has been proposed.Most of them concentrated on the use of geographic information system (GIS) vehicle routing protocol research.However, the routing protocol algorithm based on geographical location information complexity is high, the node real-time computation load is bigger, and abnormal GPS devices, protocol cannot work at all.And in terms of QoS [2] (1) the available bandwidth values for: When each node needs to know its own bandwidth available, it will access the MAC layer, and obtained value of the available bandwidth by the method of mathematical expectation.The formula is as follows: (2) Link stability degree of access: In formula, ∆T i As type of HELLO message of twice arrival interval time.In this paper, m was set to 10, Link _ Stability set to 100; if the calculation result more than this value, it is set to 100.10≥Stability_Link≥0 ,if the interval of the HELLO information received are the same, it is very ideal link-state; stability degree is 0, for the best.
Actual comparing with the inside of the RREQ packet link stability degree, they need a conversion function, depending on the environment Settings.

The QOSAODV Protocol
QOSAODV routing protocol divided into the following three steps: (1) routing request initiated: When node receives from the upper after sending a data packet, they first check for efficient reach the destination node routing.if there are, the data packet are direct forwarded; if there are not , request is routed.Before the data was cache, message protocol extract the data packet header QoS mission requirements to carry value, and record in the routing

Simulation
This article uses the Manhattan model [7], The specific parameters of the simulation environment such as the following Table3-1.The proposed QOSAODV protocol's performance is analyzed using NS2 simulator.
security, almost follows the traditional QoS Ad Hoc network routing protocol mechanism, unable to reflect the characteristics of vehicular ad hoc networks.Based on the above situation, this paper proposes is not based on the geographic location information of the o vehicular ad hoc networks routing protocol strategy, introducing QoS safeguard mechanism of AODV routing protocol, and make it adapted to the vehicle mobile environment.In the AODV protocol[3], each node maintains a neighbor list inside, which only save IP address and sequence number of the neighbor, so data forwarding do not know and the link between the neighbor node which is more suitable for data forwarding, and blind selection and forwarding.But the actual link is much different from the ideal situation, especially in the road between the link status of the vehicle is more obvious.Because of its direction are different for several vehicles in the one hop range, so it can maintain effective communication mobile distance difference is great, which shows do not consider the link state and random neighbor selection as forwarding nodes of AODV strategy will often lead to link the frequent fracture.If the node can know the state of the link between itself and the neighbor node in real time, it can effectively carry out the selective forwarding, which can improve the effective maintenance time of the link.And in single frequency wireless channel environment, each node are and the neighbor nodes share the limited wireless bandwidth resources, so through the method of monitoring the idle channel, channel access can use the degree of bandwidth[4], can be in accordance with the task transmission bandwidth requires the selection of bandwidth wider links.In this way, it can improve the performance of the AODV protocol, and also can achieve the classification of QoS tasks.Here is a reflection of this idea, a QoS strategy is proposed: (1) when the source node sends RREQ to control the message, the bandwidth requirement of the task and the link stability are written into RREQ and broadcast.(2)when the intermediate DOI: 10.1051/ C Owned by the authors, published by EDP Sciences, 201 RREQ packet, it first to compare their bandwidth ability and RREQ packet demands the bandwidth of the value, if not satisfied without forwarding, it discarded directly.If meet, then compare the previous radio RREQ neighbor nodes and their link-state values and RREQ packet request link stability value, if meet the forwarding, if does not meet the discarded directly, not to deal with.(3) when the destination node receives RREQ packet, they also compare their bandwidth capacity and link stability.by comparison, they embed the minimum RREP message and reply to the source node.(4) when the source node received the corresponding RREP message ,they extract its bandwidth value and stability of the link, update the routing tables, and data forwarding.This QoS routing forwarding mechanism can effectively avoid the lack of poor condition of node and poor bandwidth link, choose a more stable sufficient bandwidth of the link.But also some deficiencies, for example, if the intermediate node through the comparison, they will lost RREQ packet, they unable to find a satisfactory routing and lead to the routing request packet radio invalid, consumption of network bandwidth[5].Also, if the source node find the routing path of failure for the first time, because of the change of the unpredictable link-state, the link disconnected, until received RRER message to re-launch the routing request ,they operation.Through repeated experiment and simulation, the mechanism does not significantly improve performance of routing vehicular ad hoc networks protocol.How to accurately obtain the node itself available bandwidth capacity and link between neighbor nodes is the key of the routing protocol design performance, which influence QoS mechanism of state .Due to considering the portability of mobile terminals and CPU capacity, extract QoS index and the index of compare and select the operation and routing algorithm is not too complicated.This article take the simple and effective mathematical expectation and mathematical statistical methods to calculate the variance QoS parameter values.

table .
Protocol use the extracted Qo S demand value do a (3) respond routing: Receiving RREQ packets, destination node, as well as the operation of the intermediate nodes, update the routing table, and concluded minimum value of QoS.In order to respond to the source node , destination node make a RREP message, QoS minimum value are written into the RREP message of destination node, and sent to the source node.RREP reply according to the RREQ packet forwarding generated in the process of reverse routing, the source node to unicast.