Congestion Relief in Subway Areas by Tuning Uplink Power Control in LTE

Providing an adequate quality of service in subway areas is a challenging task in cellular networks, due to the complexity of the indoor propagation and the effects of group mobility. Thus, it is common that traffic congestion appears in subway cells. In this paper, a self-tuning method for uplink power control (ULPC) parameters is proposed to solve congestion problems in long-term evolution (LTE) cells located in a subway network. First, a thorough analysis of congestion phenomena in LTE subway cells is presented. The aim of the analysis is to show how uplink performance is severely degraded with group mobility in subway cells. Then, a heuristic algorithm is proposed to tune the nominal power parameter in ULPC on a cell basis to solve localized congestion problems. The aim of the algorithm is to exploit cell isolation by increasing user transmit power to improve system spectral efficiency and thus reduce the average cell load. Field trial results show that the algorithm significantly improves network accessibility and retainability in subway scenarios without any hardware upgrade.