Design and analysis of MIMO multiuser system under coexistence of direct and relay-aided links

This paper studies multiuser MIMO (multiple input multiple output) system with a mixed structure of two transmission schemes in which each user chooses direct or AF (amplify and forward) relay-aided link depending on the channel condition. First, an equivalent two stage MTMR (multiple transmitter multiple receiver) model is introduced to simplify the problem, then SINR (signal to interference plus noise ratio) performance analysis is given. Next, two kinds of design methods utilizing ZF (zero forcing) are described based on the two stage model. Through computer simulations assuming fading channels, the effectiveness and features of the proposed design methods are investigated.