Co-channel interference cancellation using precoding for bi-direction multiple hops MIMO relay systems

Vu Van Son,Nguyen Huy Hoang,Pham Thanh Hiep

doi:10.1186/s13638-015-0493-0

Abstract

In order to increase performance of a system while saving power consumption, multiple hop MIMO relay systems (MHMRSs) have been considered. There are many researches on the physical (PHY) layer, medium access control (MAC) layer, and MAC-PHY cross-layer to avoid a co-channel interference, such as the matched/orthogonal weight algorithm, TDMA-based smart antenna and so on. The matched/orthogonal algorithm is available for bi-directional communications; however, it requests at least three antenna elements at every relay. Consequently, it is unavailable for small wireless devices that are being demanded. In this paper, we propose an algorithm to cancel the co-channel interference of bi-directional communication MHMRSs by signal processing at receivers using precoding at transmitters. The proposal algorithm can perform with only two antenna elements while maintaining character of MIMO. The proposal algorithm is compared to the TDMA-based smart antenna algorithm which also can perform with two antenna elements, in both perfect and imperfect channel state information (CSI) schemes. Numerical calculation results indicate that a channel capacity of proposal algorithm is much higher than that of TDMA-based smart antenna algorithm in the perfect CSI scheme due to complete cancellation of co-channel interference and viability of bi-directional communications of proposal algorithm. In the imperfect CSI scheme, the channel capacity of the TDMA-based smart antenna algorithm is more robust when channel estimation errors increase; however, the channel capacity of proposal algorithm is still higher when the channel estimation error is large.

Highlights

Limitations on frequency resources and transmit powers are important problems for wireless communication networks
We have optimized that distances between each transceiver transmit powers of every transmitter to improve the performance of multiple hop Multiple input multiple output (MIMO) relay systems (MHMRSs) whether there is a control on medium access control (MAC) layer [12, 13] or not [14]
Every relay can transmit data to bi-direction in the same channel, and the channel capacity is improved by means of networkoriented MIMO interference cancellation that cannot be achieved by time division multiple access (TDMA)-based smart antenna MIMO networks

Summary

Introduction

Limitations on frequency resources and transmit powers are important problems for wireless communication networks. In order to maintain the high channel capacity while saving transmit powers and sharing spectrum, multiple hop MIMO relay systems (MHMRSs) are taken into account. Every relay can transmit data to bi-direction in the same channel, and the channel capacity is improved by means of networkoriented MIMO interference cancellation that cannot be achieved by TDMA-based smart antenna MIMO networks. The interference from two adjacent relays is cancelled; the co-channel interference from other relays still affects the performance of MHMRSs. In this paper, we propose a method to cancel the cochannel interference from all sensors that share the spectrum while achieving the diversity/multiplexing gains. The proposal algorithm uses the precoding at every transmitter; it is called as co-channel interference cancellation using precoding (CICP) for multiple hop MIMO relay systems.

System model

Channel capacity of CICP algorithm

Imperfect CSI scheme

Numerical evaluation

Conclusions