Research On MAC Protocols In Ad Hoc Networks

A mobile Ad hoc network (MANET) is a decentralized, multi-hop, self-configuring, peer-to-peer communication network that consists of several nodes with radio transceivers. It can be rapidly deployed and networked adaptively without relying on the pre-existing network infrastructure. The nodes in a MANET can dynamically join and leave the network without notice in advance, and possibly without disruption to other nodes'communication.Ad hoc network is the current hotspot in the academe of wireless communications, especially in the field of civil situation. The design of the MAC protocol is one of the key technologies of the Ad hoc network, which directly impacts the network performance such as the access fairness, throughput, delay and the packet-lost-ratio etc. Ad hoc network has its own characteristics, which make the design of MAC protocol face lots of challenging technical issues.Based on Ad hoc network practical application, this paper first describes the architecture, the key technical issues to be resolved and the application prospects of Ad hoc network. And then it deeply investigates the key points of MAC protocols in Ad hoc network based on the existing MAC protocols, considering the special requirements of MAC protocols of Ad hoc network. After that, a research on how different system control rules impact the SINR and moreover the overall system performance is carried out, based on which two kinds of MAC protocols, packet-length-control-and-rate-control and packet-length-control-and- power-control, i.e. LCRC and LCPC, are worked out. Incorporating the merits of two above protocols and also considering the Ad hoc network traffic classes in reality and their various Quality-of-Service (QoS) requirements, a MAC protocol which considers different traffic class accessing and guarantees their respective QoS requirements is brought forward, traffic-differentiate-and-QoS-guarantee, i.e. TDQG protocol.The main research work and creative poinits are listed as follows:Firstly, the characteristics of the Ad hoc network are deeply investigated, and then the special requirements of its MAC protocol design are indicated. Meanwhile, a concept of average Signal-Interference-and- Noise- Ratio ( S INR) is defined to estimate the network status and offer a criterion of system performance evaluation.Secondly, the relationship between the transmission power and the system performance based on different control rules (rate control/power control) are digged out, and the curves of this relationship are also given, which offers a strong base of the protocol design.Thirdly, a novel MAC protocol LCRC is presented for optimizing system throughput. Considering the characteristics of Ad hoc network, the impacts of different optimal rules on the system performance are thoroughly analyzed, and a transmission strategy using reasonable high power, adaptive length and rate is verified. And the protocol is presented, i.e. LCRC protocol. LCRC incorporates the merits of rate control rules and adaptively adjusting packet length rules, fully optimizing the system throughput and embodies the advantage of Ad hoc network. Based on above strategy, a QoS scheme is also given which strongly guarantees the throughput of the practical Ad hoc system using the LCRC protocol.Fourthly, a new MAC protocol called LCPC is proposed for optimizing the energy effectiveness. To compensate the insufficiency in energy effectiveness of LCRC, the relationship between transmission power and transmission rate is investigated, which is the foundation of the QoS guarantee. Then the LCPC protocol is presented aiming at optimizing the energy effectiveness. This protocol makes use of the virtue of the power-control and the adaptive adjusting packet-length, fully optimizing the energy effectiveness, materializing the superiority of Ad hoc network and the capability of effectively allocating and utilizing channel resources.Finally, a new MAC protocol which is suitable to Ad hoc network and effectively considers different traffic class accessing and offers high QoS levels is presented. With the development of Ad hoc network, it is deployed to a variety of environments such as mobile meeting, home networking, WPAN, and so on. In terms of such demands, a novel protocol TDQG is proposed which incorporates the merits of the LCRC and LCPC protocols, and a QoS scheme, which can guarantee the QoS of the real traffics, is also proposed. This protocol fully considers the characteristics of Ad hoc network, reserving resources for the upcoming traffic accessing and dynamically allocating system resources to implement fully system utilization, which can offer high QoS level for the traffic accessing.