An Intercell Interference Power Level Feedback Technique for One-Cell Reuse TDMA Systems with OFDM-Based Adaptive Modulation Scheme

摘要

To implement a one-cell reuse time division multiple access (TDMA) system using orthogonal frequency division multiplexing-based adaptive modulation scheme (OFDM AMS) and multilevel transmit power control (MTPC), co-channel interference [intercell interference (ICI)] from adjacent cells that varies dynamically on the frequency axis must be fed back very accurately to the transmitting station. Therefore, in this paper, we propose an ICI feedback technology in one-cell reuse TDMA with OFDM AMS/MTPC. First, the interference power of each subchannel is estimated by calculating the vector error which is the difference between the reference symbol on the receiving side and the received symbol. Next, instead of a digital signal method capable of expanding the amount of information, analog quadrature amplitude modulation (QAM) is adopted in order to feed back the errors with high accuracy. In addition, code division multiplexing (CDM) is adopted in order to improve the robustness to multipaths. Furthermore, to reduce the amount of feedback information, we adopt a method where the estimated interference noise power is formed into blocks by multiple adjacent subcarriers, and only the average of the block is set as the notification target, and interference power information less than some constant value is not notified. The evaluation results of the characteristics of the proposed method by a computer simulation verified that the interference noise power can be estimated very accurately and can accurately notify by using a notification frame with optimized power distribution.