On Coordinated Multi-point Transmission with Partial Channel State Information Via Delayed Feedback

Coordinated multi-point transmission (CoMP) is considered as a strategic approach to handle inter-cell interference, hence increasing spectral efficiency in interference-limited cellular networks. This paper studies a CoMP downlink transmission with delayed and quantized channel state information feedback through a capacity-limited uplink channel. The delay effects and quantization error as well as large scale path loss potentially degrade entire network performance. Under this consideration, we first characterize the system performance in terms of achievable rate for two typical CoMP techniques, namely joint processing (JP) and coordinated beamforming (CBF), in a multi-cell network. Accurate closed-form expressions are derived for evaluating the CoMP performance. Based on the derived results, an adaptive transmission strategy of switching between JP and CBF is proposed to maximize the system throughput and the operating regions of the two schemes are provided under different system setup parameters. Simulation verifies that the superiority of JP or CBF depends on system parameters including feedback delay, codebook size as well as CoMP user locations.