D2D Assisted MU-MIMO Precoding to Enhance LTE Network.

Multi-user multiple-input multiple-output (MU-MIMO) has been adopted as a key enabling technique to achieve the capacity demand in 4G wireless networks. However, there are still some problems existing in the frequency division duplex (FDD) MU-MIMO system, such as the channel quality indicator (CQI) mismatch problem, large uplink feedback, low pairing probability of MU communication. In this paper, we exploit a MU-MIMO scheme in FDD assisted by device-to-device (D2D) technique to enhance the conventional LTE network. The proposed scheme could not only solve the above problems in conventional MU-MIMO systems, but also achieve significant performance improvement than conventional MU-MIMO schemes. Since the user pairing process is done at the user side, the feedback of the proposed scheme is reduced dramatically compared with the conventional scheme. Simulation results show that the proposed D2D assisted MU-MIMO scheme has clear superiority in terms of throughput over conventional MU-MIMO scheme in LTE networks. Because with D2D assisted MU-MIMO, the proposed scheme tackles the CQI mismatch problem and increases the multi-user pairing probability to enhance the overall throughput.