Blind Adaptive MIMO Receivers for CDMA Systems with Space-Time Block-Codes and Low-Cost Algorithms

TL;DR

This paper introduces low-complexity blind MIMO receivers for CDMA systems with space-time coding, utilizing constrained optimization and stochastic gradient algorithms to improve performance in multipath channels.

Contribution

It presents novel low-complexity blind adaptive algorithms for MIMO CDMA receivers that exploit space-time code structures and a subspace-based channel estimation scheme.

Findings

Achieves excellent performance in simulations

Outperforms existing methods

Effective in multipath channels

Abstract

In this paper we present low-complexity blind multi-input multi-output (MIMO) adaptive linear multiuser receivers for direct sequence code division multiple access (DS-CDMA) systems using multiple transmit antennas and space-time block codes (STBC) in multipath channels. A space-time code-constrained constant modulus (CCM) design criterion based on constrained optimization techniques and low-complexity stochastic gradient (SG) adaptive algorithms are developed for estimating the parameters of the space-time linear receivers. The receivers are designed by exploiting the unique structure imposed by both spreading codes and STBC. A blind space-time channel estimation scheme for STBC systems based on a subspace approach is also proposed along with an efficient SG algorithm. Simulation results for a downlink scenario assess the receiver structures and algorithms and show that the proposed schemes achieve excellent performance, outperforming existing methods.