Adaptive Power Control for 4G OFDMA Systems on Frequency Selective Fading Channels

Future cellular radio systems aim at maximizing the spectral efficiency. OFDMA radio resources are the scarce good with their dimensions bandwidth, time and space. Due to frequency selective fading the effective path-loss varies in all dimensions. Adaptive algorithms are available which allocate the best modulation and coding scheme depending on the expected SINR, as well as dynamic subchannel assignment which aims to choose the best subchannel for each user. This already boosts the performance of OFDMA system. However, these algorithms alone do not touch the transmitted power per subchannel. On the cell edge this is fine, but large areas are covered with a transmitted power exceeding the usually required SINR. In this paper we introduce a power control which saves power on the users within the cell. This leads to a reduced interference into neighbor cells, especially for future reuse one systems. Also some of the saved power can be used to boost transmissions at the cell edge. In this paper we introduce an adaptive power control concept and arrange it into a closed loop control system which contains blocks for all adaptive algorithms for modulation, power, subchannel usage and channel quality indication.