A semi-coherent multiple-input multiple-output (MIMO) scheme, which only requires one of its receivers to operate coherently while others can be non-coherent, is proposed. In this scheme, the information symbols at the non-coherent receivers are estimated with the aid of a coherent receiver through a covariance estimator, thus allowing signals to be decoded coherently in the final stage. Results show that the proposed system is able to provide performance on par with that of the more complicated fully coherent MIMO systems.

Femtocell structures can offer better voice and data exchange in cellular networks. However, interference in such networks poses a major challenge in the practical development of cellular communication. To tackle this issue, an advanced interference mitigation scheme for Line-Of-Sight (LOS) femtocell networks in indoor environments is proposed in this paper. Using a femtocell management system (FMS) that controls all femtocells in a service area, the aggressor femtocells are identified and then the transmitted beam patterns are adjusted using the linear array antenna equipped in each femtocell to mitigate the interference contribution to the neighbouring femtocells. Prior to that, the affected users are switched to the femtocells that provide better throughput levels to avoid increasing the outage probability. This paper considers different femtocell deployment indexes to verify and justifies the feasibility of the findings in different density areas. Relative to fixed and adaptive power control schemes, the proposed scheme achieves approximately 5% spectral efficiency (SE) improvement, about 10% outage probability reduction, and about 7% Mbps average user throughput improvement.