Hybrid FDD/SDD-WCDMA system architecture: joint power control and space diversity for demand access channels

We present a hybrid FDD/SDD-WCDMA system architecture for supporting symmetric and asymmetric data users, with the former served by a cellular network and the latter served by broadcast systems. The asymmetric data users employ packet-mode access to transmit demand messages in relatively short bursts and are silent at other times, whereas the symmetric data users employ circuit-mode access. This imposes a significant challenge for performance optimization since accessing asymmetric data users can degrade the performance of currently active symmetric data users by introducing extra interference variations which reduce system capacity. We study the implementation and performance of a special version of iterative SIR-based power control algorithms in which currently active symmetric data users are protected from interference by accessing asymmetric data users. Moreover, as the accessing asymmetric data users are expected to have short duty cycles on the cellular network's reverse link, significant overhead may be required for iterative power control. We thus investigate the use of space diversity schemes to help reduce the high iteration overhead and access their performance jointly with the proposed iterative SIR-based power control algorithm.