| Summary: | 博士 === 國立交通大學 === 資訊科學系 === 90 === This study presents a novel architecture, multihop cellular network (MCN), for wireless data communications. MCN preserves the benefit of conventional single-hop cellular networks (SCN) where the service infrastructure is constructed by fixed bases, and it also incorporates the flexibility of ad-hoc networks where wireless transmission through mobile stations (MSs) in multiple hops is allowed. MCN can reduce the number of required bases or improve the throughput performance, while limiting path vulnerability encountered in ad-hoc networks. This thesis consists of three parts: (I) the modeling of MCN and SCN, (II) the routing protocol designed for MCN, and (III) the implemented prototype of MCN.
First of all, this thesis analyzed the performance of MCN and SCN in terms of mean hop count, mean number of channels (i.e. simultaneous transmissions), hop-by-hop throughput, and end-to-end throughput under different traffic localities and radio distance. Analytical results show that the throughput of MCN exceeds that of SCN; the former also increases as the radio distance decreases. The above results can be accounted for by the different orders, linear and square, at which mean hop count and mean number of channels increase, respectively. Then, because the existing routing protocols designed for ad-hoc networks are not suitable for MCN, herein, a hybrid of table-driven and demand-driven protocols with base-centric computing is designed. The base tracks network topology by the table-driven method and can thus compute paths for MSs, constituting base-centric computing. When MSs need paths, the path query messages are unicast to the base. If MSs do not obtain paths from the base, then path query messages will be flooded as in demand-driven AODV. The simulation confirms the analytical results and shows that the throughput of MCN is about 2 to 3 times that of SCN when the radio distance is 1 to 1/4 of that in SCN. Besides, with the base-centric computing, the hybrid protocol overall outperforms AODV because most path query messages are unicast to the base and the overhead is greatly reduced. At last a prototype of MCN, capable of multihop routing and roaming, is implemented over a wireless LAN platform. Demonstration shows that MCN is a feasible architecture for wireless LANs.
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