MAC Protocol Research In Ad Hoc Network With Direction Antenna

Ad hoc network is a temporary autonomous system, consisting of a series of wireless mobile terminal. It is a multi-hop network without any network infrastructure. Previous research shows that using directional antenna significantly improves the performance of network, reduces the signal interference and perfects the quality of uplink. But the studies mostly focus on sending with directional antenna and receiving with omni-directional antenna. This paper aims to study the performance of the network which uses directional antenna to send and receive signal, and discuss MAC protocol that apply to this network.In two-directional network, there are more restrictions on communications because of directionality of directional antenna. The neighbor discovery algorithm in omni-directional network is not suitable for directional network. It is necessary to found the suitable discovery algorithm for the bi-directional network. By simulation of the random algorithm (CRA) and scan-based algorithm (SBA), it is found that the neighbor discovery time of SBA is less than CRA and it is suitable for bi-directional network.In this thesis, a TDMA-based directional MAC protocol is studied. In order to confirm and analyze performance of the protocols, a directional antenna model is created in OPNET. It is proved that it can optimize the network performance by using directional antenna in Ad hoc network. The TDMA-based directional MAC protocol is designed. The protocol consists of neighbor discovery process and data communication. SBA-D algorithm is used in the protocol to discovery neighbor. In data communication process, each frame is divided into two sub-frames:reservation sub-frame and data transmission sub-frame. Reservation sub-frame is used for two nodes to reassure their connection detected during neighbor discovery and to make data transmission slots reservation; data transmission sub-frame is used to send data by nodes at their ordered time slots. The feasibility of the protocol is confirmed by modeling in OPNET, the simulation analysis shows directional network achieves higher data rate, and dramatically improve throughput, but also increase the transmission delay which determined by length of frame.