Effects of outdated CSI on the coverage of CoMP-based ultra-dense networks

Feedback delay can severely impact network performance in mobile network and the theoretical quantification of performance degradation has attracted much research interest recently. In this paper, we conduct coverage analysis of mobile ultra-dense networks (UDNs) where coordinated multipoint (CoMP) technology is adopted to enhance network performance and the available channel state information (CSI) is outdated due to feedback delay, especially for large cluster case. Coverage probability is evaluated by obtaining a closed-form expression, which considers the effect of outdated CSI. Furthermore, we give the approximated expression of coverage probability so that the impact of cluster size can be overtly observed. Numerical results illustrate that coverage probability decreases with the user's velocity but can be compensated by relatively larger cluster size scheme or denser access point (AP) deployment, which can also provide useful insights into the parameter design of UDNs.