Channel assignment schemes in cellular communication systems

by Chong, Peter H.

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 kznited radio frequency band. One approach is to employ a more efficientchannel assignrnent scheme. Packet-switching wiiI also be used in future mobile cellular systerns 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 assignrnent (DCA), in order to irnprove capacity in current orfuture 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 conventiond FCA systern. It is shown that the performance of FCA cm be substantially improved by using RF. 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 @CA-WI), is then proposed and studied by cornputer simulation. In this scherne, a base station in a ce11 assigns a channe1 to a cal1 based on the channel information in its neighborîng cells. It is shown that DCA-WI outperforms previous channel assignment schemes in both uniforrn and nonuniform trafic distributions. To support bursty trafic, FCA and DCA schernes used in conjunction with packet reservation multiple access (PRMA) and PRMA++ in a packet-switched voice cellular systern are studied. Two measurement-bâsed protocols, DCA/PRMA and DCA/PRMA-t-+, 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-ce11 interference during speech talkspurts. It is shown that channel reassignment can improve the performance significantly. iii