Transmit Power Allocation for Precoded Distributed MIMO OFDM Systems

This paper deals with a new multi-user linear precoding technique for downlink of distributed MIMO OFDM systems. We consider a distributed broadband wireless system where some base stations are transparently linked by optical fiber to a central unit. We further assume that the user terminals are equipped with an antenna array and the distributed base stations equipped with either single or an antenna array. This architecture provides a high speed backhaul channel allowing an efficient joint multi-cell processing. The proposed power allocation algorithm is based on minimization of the sum of inverse signal-to-noise ratio (SNR-1) on each user terminal over the available subcarriers. The motivation to minimize the sum of SNR-1 instead of bit error rate (BER) is in the fact that the first criterion achieves a closed-form solution, which is more interesting from practical point of view. The aim is to propose a practical distributed precoding technique to remove the inter-cell interference and improve the user´s fairness at the cell-edges. The performance of the proposed scheme is evaluated, considering typical pedestrian scenarios based on LTE specifications.