Adaptive Cellular Cyclic Delay Diversity for Multi-Carrier Spread Spectrum Systems

The cell border area in a multi-carrier spread spectrum (MC-SS) based system is influenced by large inter-cell interference for a total frequency reuse in the neighboring cells. To handle this inter-cell interference and to enable reliable soft handoff procedures, macro diversity techniques can be applied for these scenarios. Applying multi-antenna transmit diversity techniques in a cellular environment, transmit diversity is transformed to macro diversity. In this paper, the cellular transmit diversity technique based on cyclic delay diversity (CDD), namely cellular CDD (C-CDD), is further investigated in terms of adaptive transmit powers and proper choices of the cyclic delays. The adaption of these system parameters results in a broadened receiving diversity area and eliminates the performance degradation within the standard C-CDD. Further, we show that the use of spread spectrum multi-carrier multiple access (SS-MC-MA) exploits the scarce system resources in a more efficient way with almost the same or better performance compared to the well-known multi-carrier code division multiple access (MC-CDMA) scheme.