The Research On Control Frame Rate Adaptation Algorithms For Ad Hoc

Ad hoc network is a special kind of wireless network and is not dependent on any network infrastructure anytime and any place. It has a lot of advantages:free wiring, mobility, networking flexibility, survivability, and low cost of investment. Therefore, it is widely used in operational command, project supervision, and implementation of emergency rescue and relief mission occasions.The network environment of Ad Hoc network is time-varying due to its special networking. Therefore, it is not feasible to directly adopt TCP/IP layered protocol in Ad hoc network which is well applied in the traditional wired networks. The paper presents a cross-layer design approach for Ad hoc network protocol. That is to say:From the global point of view the paper designs multi-protocol stack by crossing layers to allow more information sharing and interaction between the layers. As a result, the system can achieve optimized integrated performance and improve resource utilization ratio and overall system performance.To maximize network throughput, this paper makes research on channel access mechanism and the rate selection mechanism in MAC layer and physical layer of Ad hoc network based on IEEE 802.11 protocol, and introduces the classical rate adaptation mechanisms in detail:ARF, RBAR and OAR. Most of the rate adaptation algorithms are about the data frame rate. However, the rate adaptation algorithm about the control frames is still very rare. This paper adopts the classical rate adaptation algorithm of OAR for the data frame and presents a novel rate adaptation algorithm for the control frames by modifying the virtual carrier sensing and with the help of extended inter frame space EIFS and physical carrier sensing. The paper uses the network simulation tool ns2 to simulate the proposed rate adaptation algorithm for the control frames using five different sizes of data packet in the three different environments. The simulation results show that the proposed rate adaptation algorithm can effectively reduce overall system cost, increase the system throughput in different settings. The larger the data packet, the greater the system throughput. The improvement ratio of the system throughput is the largest in the environment of multiple hops and multiple flows compare with the other environments.