Research On Key Technologies Of Ad Hoc Cellular Communication Networks

By introducing ad hoc communication mode into cellular networks, the ad hoc cellular mobile communication systems (the hybrid networks) solve some disadvantages of today's cellular networks. So it attracts more and more attentions. Presently, many projects are involved in the research of the combination of the cellular networks and the ad hoc networks. Supported by a project of the 863 Program—"research on ad hoc networks based on 3G technology" and a project of the NSFC—"Research on the future mobile communication system which supports ad hoc mode", this thesis discusses some key technologies of the ad hoc cellular communication systems.This thesis discusses the coverage enhancement problem of the hybrid networks which is caused by ad hoc communication mode. In order to discuss it, the thesis puts forward an analysis model and an evaluation metric—"the service ratio of system". After the analytical analyses and algorithm simulations, the results show that the service ratio of the hybrid networks is better than that of the pure cellular networks, and the factors that determine the merit include the density of nodes, the transmission radius of nodes, the number of dead spots, the radius of dead spots, and the maxium hops of the system.After the advantages caused by ad hoc communication mode (the problems why the ad hoc mode is introduced) are discussed, the thesis then discusses the methods of introducing the ad hoc mode to cellular networks (the problems how the ad hoc mode is introduced).Firstly, based on the integration level between the ad hoc communication mode with the cellular networks and the allocation scheme of the wireless resources, the thesis classifies the ad hoc cellular communication system. For each framework of the hybrid network classifications, the thesis analyses its network structure, the types of nodes and the protocol levels in detail.Secondly, the thesis studies the resources allocation of the ad hoc cellular communication system and puts forward some ideas to resolve the problem. For the resources allocation scheme that the ad hoc mode between nodes and the cellular mode between base stations and nodes use one wireless physics channel, the thesis puts forward two resources allocation algorithms. Simulations show that the throughput of the hybrid networks is better than that of the pure cellular systems, and the throughput of the hybrid networks which use algorithm I is better than the throughput of the hybrid networks which use algorithm II, besides, the performance of the algorithms is related to the localization of the traffics, the transmission radius of the ad hoc communication mode and the maximum hops allowed in the system.At last, besides the algorithm design and simulation to some key problems, the research that how ad hoc mode is introduced also includes the realization of an ad hoc cellular demonstration system. The model of the system has two air interfaces; its ad hoc mode is introduced in terminals. The cellular part of the system uses the existing 3G system and the ad hoc part of the system is designed by us. From the protocol level point of view, the ad hoc part is composed of the application; route program used Q-AODV; OS; the multi-hops control layer (IMD); the NIC driver; the BR-TDMA MAC layer based on a synchronous channel and the physics layer based on the slot burst scheme of the UTRA TDD LCR. From the physics formation point of view, the ad hoc part is composed of a PC and an ad hoc communication module. The debugging of the system is over, and the test results show that this system realizes the combination of the cellular networks and the ad hoc networks, its function and performance achieve the requirement of the design.