Transmit Power Efficiency of a Multi-Hop Virtual Cellular System

Recently, there is a strong demand for higher speed data transmissions in cellular mobile communications systems. However, there will be a serious problem; as data transmission rate becomes higher, the peak transmit power becomes larger. To decrease the peak transmit power while increasing the data transmission rate, the cell size should be made significantly small. We proposed a virtual cellular concept to efficiently realize picocell network and showed that the virtual cellular system can significantly reduce the transmit power of a mobile terminal while increasing frequency efficiency. The virtual cell consists of a central port, which is a gateway to the network, and many distributed wireless ports. In the virtual cellular system, data relay between the central port and wireless ports is necessary. In this paper, multi-hop wireless system is applied for data relay. The virtual cell control layer is introduced for the multi-hop transmission. The routing algorithm that minimizes the total uplink transmit power of wireless ports for data relay is presented. The total transmit powers of uplink and downlink for data relay are evaluated by computer simulation to show that the multi-hop system can reduce considerably the total transmit powers, while avoiding unnecessary large time delay, irrespective of the values of path-loss exponent α and the shadowing loss standard deviation σ.