A Robust and Precise Solution to Permutation Indeterminacy and Complex Scaling Ambiguity in BSS-Based Blind MIMO-OFDM Receiver

The multiuser separation problem in a multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) system can be represented as an instantaneous blind source separation (BSS) problem in complex domain. But reconstruction of multiuser signals suffers from permutation indeterminacy, amplitude scaling ambiguity and phase distortion which are inherent to complex BSS. This paper presents a robust and precise solution to these problems in order to reconstruct multiuser OFDM signals. It is based on the characteristics introduced to transmitted OFDM symbols by convolutional encoding at the transmitter. The accuracy of these characteristics is obtained by optimizing the convolutional code. Despite the previous BSS-based MIMO-OFDM multiuser signal reconstruction method, the proposed method is independent of channel characteristics. Experimental results show that even over channels with necessities required for efficiency of the previous method, the proposed method concludes significantly better performance.