时分双工MIMO放大转发中继系统中下行链路的联合鲁棒设计

Joint robust design for TDD MIMO amplify-and-forward relay downlink systems

考虑了时分双工MIMO放大转发中继系统中下行链路基站预编码器、中继预编码器与用户均衡器的联合设计问题。在实际应用中信道估计误差以及信道互易延迟会显著恶化基于理想信道状态信息(CSI)的联合设计性能。从估计误差的分布和互易延迟的时间相关特性出发,建立了综合考虑两方面因素的联合"估计误差-互易延迟"信道模型。基于该模型,针对第一跳传输设计了信道奇异值分解的基站预编码方案,避免了第二跳CSI的反馈开销,然后将给定中继总发送功率约束下最小化用户和均方误差(SMSE)的中继预编码器和用户均衡器进行联合优化,并利用KKT(Karush-Kuhn-Tucker)条件给出了该优化问题的闭合解。数值结果验证了所提方案的鲁棒性和有效性。

The problem of joint designing the base station （BS） precoder, the relay precoder and user equalizers for TDD MIMO amplifying- and-forwarding relay downlink systems is considered. In practical applications, the channel estimation error and the channel reciprocity delay can result in a serious performance loss of a joint designing based on ideal Channel State Information （CSI）. Evolved from the distribution of estimation error and the temporal correlation of reciprocity delay, a joint ＂estimation error-reciprocity delay＂ channel model that takes both effects into account was established. Based on this model, a channel SVD-based precoding scheme at BS aiming at the first hop transmission was presented, which avoids the feedback overhead of the second hop CSI. Then a joint optimization problem of the relay precoder and user equalizers, which is based on minimizing the sum mean square error （SMSE） of all users with a constraint on the relay total transmit power, was set up. By using KKT （ Karush- Kuhn-Tucker） conditions, a closed-form solution to this problem was achieved. Numerical results verify the robustness and effectiveness of the proposed scheme.