Energy Saving Performance Comparison of Coordinated Multi-Point Transmission and Wireless Relaying

Currently, two cooperative transmission strategies, Coordinated Multi-Point (CoMP) Transmission and wireless relaying, are expected to be deployed in future cellular systems to improve the performance of cell-edge users. Due to the cooperation diversity, these technologies can potentially lead to more energy saving. Therefore in this paper, we analyze their energy saving performance with an average outage constraint. The impact of the traffic intensity and BS density are also investigated. Based on the typical parameters setting, our calculation results show that traffic intensity can be divided into three classes: ``coverage-limited'' region, ``energy-efficient'' region, and ``capacity-limited'' region. The coverage-limited region prefers offline fixed algorithms, while dynamic online algorithms are more suitable for the energy-efficient region. As BS density goes higher, the energy-efficient region becomes larger. However, the traffic load region where the cooperation schemes bring benefits becomes smaller. To overcome CoMP, relay stations need to consume energy as small as possible. Even through relay cost energy low enough, the traffic intensity region where wireless relaying overcomes CoMP will become smaller as network goes denser. Our analytical results are of great help for future ``green'' network planning.