Blind uplink space-time channel estimation for space-time coded multicarrier code division multiple access systems

The uplink of a space-time coded multicarrier code division multiple access (MS-CDMA) system equipped with a uniform linear array (ULA) at the base station is investigated. Transmission takes place over frequency-selective fading channels and the goal is to blindly estimate the space-time channels and the directions of arrival (DOA) for all active users in one macrocell. An auxiliary matrix including both uplink space-time channels and DOAs is constructed, on which the eigen decomposition is performed to acquire the DOAs for multiple users. Then, the singular value decomposition (SVD) is applied on the eigenvectors corresponding to the DOA of individual user to obtain a closed-form solution of the uplink space-time vector channel. Computer simulations demonstrate the effectiveness of the proposed scheme.

1. INTRODUCTION

Space-time coding (STC) is an effective coding technique that uses transmit diversity to combat the detrimental effects in wireless fading channels by combining signal processing at the receiver with coding techniques appropriate to multiple transmit antennas to achieve higher date rates. The matured MC-CDMA is another technique that has properties desirable for high-data-rate wireless communications, such as insensitivity to frequency-selective channel and frequency diversity. Thus, the combination of STC and MC-CDMA is one of the most promising schemes for next-generation wireless cornmunications^{[1], [2], [3]}. However, for MC-CDMA systems with STC transmitter diversity, each co-channel signal source will produce extra interference signals that appear independent to antennas at the receiver^[1], which results in severe multiuser interference (MUI). So, it is meaningful to exploit spatial processing techniques with antenna array at the base station to resist MUI and enhance system capacity.