Constrained least squares SDMA detector for Single Carrier transmission with Cyclic Prefix

The two major obstacles towards high-capacity indoor wireless networks are distortion due to the indoor channel and the limited bandwidth which necessitates a high spectral efficiency. The combination of Single Carrier with Cyclic Prefix (SC-CP) modulation and Spatial Division Multiple Access (SDMA) tackles both obstacles and paves the way for low cost, high-capacity wireless indoor networks [ 1]. The channel distortion due to multipath propagation is elegantly mitigated with SC-CP while the bandwidth efficiency is increased with the use of SDMA. However, to keep the WLAN cost low, simple SDMA processors with good performance are necessary. Hence, we propose a new low-complexity multi-user SDMA detector, which is designed for constant modulus signals. This linear Constrained Least Squares (CLS) receiver, which explicitly exploits the constant modulus nature of the modulation, is compared in terms of performance and complexity with the Zero Forcing (ZF) and the Minimum Mean Square Error (MMSE) receiver. Simulations show that the CLS detector significantly outperforms the ZF detector and comes very close to the performance of the MMSE detector. Furthermore, the estimation complexity for the CLS detector is substantially lower than for the MMSE detector, which additionally requires estimation of the noise power.