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Channel assignment schemes in cellular communication systems Chong, Peter H. J.


The demand for mobile cellular communications services is increasing rapidly. Much effort is being devoted to the design of techniques to support a large number of users in a limited radio frequency band. One approach is to employ a more efficient channel assignment scheme. Packet-switching will also be used in future mobile cellular systems since it is expected that most of the traffic sources carried in future systems will be very bursty due to the combination of voice, data and video communications services. The objective of this thesis is to study various types of channel assignment methods, fixed channel assignment (FCA) and dynamic channel assignment (DCA), in order to improve capacity in current ox future cellular systems. The performance of a Reuse Partitioning (RP) system using FCA (FRP) with and without handoff is first analyzed. RP uses n cluster sizes instead of one as used in a conventional FCA system. It is shown that the performance of FCA can be substantially improved by using RP. With mobile users, the capacity improvement of FRP relative to FCA decreases with the average handoff rate. A new distributed DCA scheme, known as DCA with interference information (DCA-WI), is then proposed and studied by computer simulation. In this scheme, a base station in a cell assigns a channel to a call based on the channel information in its neighboring cells. It is shown that DCA-WI outperforms previous channel assignment schemes in both uniform and nonuniform traffic distributions. To support bursty traffic, FCA and DCA schemes used in conjunction with packet reservation multiple access (PRMA) and PRMA++ in a packet-switched voice cellular system are studied. Two measurement-based protocols, DCA/PRMA and DCA/PRMA++, are studied to cope with the highly unpredictable and time-varying microcellular environment. A channel reassignment technique is suggested which reduces the number of packets lost due to out-of-cell interference during speech talkspurts. It is shown that channel reassignment can improve the performance significantly.

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