Cross-layer design of combining AMC with HARQ in cooperative relay system with perfect and imperfect CSI

A cross-layer design which combines adaptive modulation and coding (AMC) at the physical layer with a hybrid automatic repeat request (HARQ) protocol at the data link layer (LL) is presented, in cooperative relay system over Nakagami-m fading channels with perfect and imperfect channel state information (CSI). In order to maximize spectral efficiency (SE) under delay and packet error rate (PER) performance constraints, a state transition model and an optimization framework with perfect CSI are presented. Then the framework is extended to cooperative relay system with imperfect CSI. The numerical results show that the scheme can achieve maximum SE while satisfying transmitting delay requirements. Compared with the imperfect CSI, the average PER with perfect CSI is much lower and the spectral efficiency is much higher.

基于改进OMP算法的毫米波大规模MIMO混合预编码设计

针对全连接单用户毫米波大规模MIMO系统,以最大化系统可达和速率为目标,提出一种基于改进的正交匹配追踪(orthogonal matching pursuit,OMP)算法的混合预编码方案。在既有的基于OMP算法的混合预编码基础上,首先,针对其迭代次数过多的问题,受多步长思想的启发,从阵列响应集合中选取与射频链路数目相等的最优的前多列矢量,从而求得模拟预编码矩阵;其次,针对其求逆运算复杂度高的问题,利用H9lder不等式及Schatten范数来逼近待优化的目标函数,从而求得最优的数字预编码矩阵。仿真结果表明,所提基于改进的OMP算法的混合预编码方案有效降低了运算复杂度,且在数据流数目与射频链数目相差较小时,其系统性能更优。