Channel capacity for linearly precoded multiuser MIMO for discrete constellations

Ghaffar, Rizwan; Knopp, Raymond
PIMRC'09, 20th IEEE international Symposium on Personal, Indoor and Mobile Radio Communications, September 13-16, Tokyo, Japan

This paper is based on the idea of exploiting the discrete constellation alphabets in linear precoding for the downlink of multiuser (MU) MIMO. We study the effect of discrete constellation inputs on the sum rate of different linear precoders while confining ourselves to the case of two single antenna users. We show that contrary to the case of Gaussian alphabets where altruistic solutions as interference cancellation (channel inversion - CI) and interference attenuation (regularized channel inversion - RCI) are the recommended strategies for linear precoding, it is beneficial not to attenuate or cancel the MU interference, if it is coming from discrete constellations. This interference belonging to finite sized constellations has a structure which can be effectively exploited in improving the error resilience at the users. Under such a scenario, it is better to use the degrees of freedom available at the transmitter to improve the desired signal strength at the users instead of utilizing them to nullify or attenuate the undesired signals (interferences) at the users. Therefore the egoistic linear solutions as matched filter (MF) based precoding bears the potential of enhanced sum rate and improved performance as compared to the altruistic linear solutions.

Communication systems
Eurecom Ref:
© 2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.