Research On Key Technologies For LTE-A CoMP Systems

In 3 GPP Long Term Evolution (LTE) systems, as frequency reuse factor of one is approved, the inter-cell interference (ICI) is severe. In order to mitigate ICI, coordinated multiple-point transmission and reception (CoMP) has been adopted in 3GPP LTE-Advanced systems. This dissertation analyzes the challenges to conventional radio air interface when CoMP is introduced. Moreover, effective solutions are proposed to solve these challenges, so as to guarantee the performance gain of CoMP. The main research contents of this dissertation are summarized as follows:In downlink CoMP systems, multiple-point coordinated transmission technique is an promising tool to enhance the signal quality. This dissertation adopts a linear precoder design by maximizing a signal to leakage and noise ratio (SLNR) metric, which can decrease the ICI with reasonable computation complexity. Furthermore, distributed/centralized multiple-point joint scheduling algorithms are designed for different coordination scenarios.In downlink LTE systems, the demodulation of data channel is based on cell-specific reference signal (RS). In LTE-Advanced systems, to satisfy the needs of CoMP and high-order MIMO, User-specific demodulation RS are adopted to demodulate data channel. This dissertation puts forward a set of demodulation RSs, which are uniformly distributed in time/frequency domains. Simulation proves that when the RS overhead is the same, the proposed RS design achieves best performance in high-speed movement environment.In uplink CoMP, the conventional power control (PC) scheme cannot work well since a UE can be served by multiple cells. This dissertation analyzes uplink PC issues in detail, and proposes an effective scheme aiming to obtain the reception diversity gain from CoMP. System-level simulation results have shown that the proposed scheme can improve both cell average and cell edge throughput.In heterogeneous network (het-net), the interference situation between macro and pico cells may become extremely unfavorable without some form of coordination. Hence, het-net is an important application scenario for CoMP. In 3GPP, two het-net scenarios are defined. This dissertation studies the merits and drawbacks, open issues, expected performance for the two het-net scenarios. Moreover, system-level simulation is performed for het-net CoMP.