Optimum Transmission Power in High Capacity Umbrella Cell Systems
Hierarchical cell systems with microcells and overlay macrocells show many advantages compared to homogeneous structures. Usually a band separation between the two different cell types is necessary to avoid strong interference and ‘out-matching’ of microcells by macrocells. This requires additional radio spectrum and does not lead to optimum spectrum efficiency. Existing macrocell systems of certain cluster sizes can be extended to hierarchical structures without using additional frequency resources. This can be realized by reuse of already macrocell assigned resources in far away microcells of the same cluster. Wave propagation characteristics in microcells are different from macrocells. This has to be considered to overcome interference problems. If the transmission power is adjusted properly it is possible to increase the subscriber capacity of existing macrocellular systems by a factor of three. The paper describes the optimum transmission power adjustment in Ricean fading channels. Furthermore the achievable additional capacity gain when applying a decentralized dynamic channel assignment scheme is estimated.
KeywordsCluster Size Cochannel Interferer Ricean Fading Channel Reuse Distance Channel Assignment Scheme
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