MISO broadcast channel with user-cooperation and limited feedback

This paper presents a user-cooperation scheme with limited feedback in a broadcast channel. The proposed scheme allows mobile stations to forward received messages over finite-capacity orthogonal channels, known as conferencing. In addition, the proposed scheme jointly uses the feedback from mobile stations to mitigate multi-user interference by choosing the best beamforming vectors from a finite-sized codebook. As a result, a multi-user broadcast channel is located between a point-to-point multiple-input multiple-output channel and a multi-user multiple-input single-output channel. The former is where full coherent cooperation among receiver antennas is allowed, and the latter is where no cooperation among mobile stations is assumed. Then, this paper analyzes the relation between the amounts of user-cooperation and limited feedback, and shows a trade-off between the relative use of each. Simulation results verify the advantage of cooperation and feedback as complementary technologies in wireless cellular networks.