Downlink performance of a CDMA system with distributed base station
Ryô Hasegawa, M. Shirakabe, Riaz Esmailzadeh, Masaki Nakagawa · 2003
High-speed and high-capacity communication is required in 4G mobile communication. However the currently used frequency band (2 GHz) will be insufficient to meet such a demand, thus more bandwidth, that seems to be allocated at higher frequencies (3 GHz or 5 GHz), is required. As the frequency band becomes higher, the propagation loss increases; thus mobile terminals (MT) need to strengthen transmission power. However, since there is a limitation on power consumption in an MT, the higher frequency band leads to reduction of cell size. Thus more base stations (BS) are needed to maintain the same area as a conventional system, boosting the infrastructure cost. To solve this problem, a system is proposed that uses some simple relay sub-base stations (SBS) for uplink and downlink and maintains the same coverage area as a conventional system. Due to the imbalance of uplink and downlink traffic, it is expected that capacity requirements are much higher in the downlink. We describe a CDMA (code division multiple access) based distributed base station (BS+SBS) system that fulfills coverage requirements. We evaluate the downlink performance of the proposed system through computer simulation and demonstrate an overall increased system capacity.