Cross-layer design with feedback delay over MIMO Nakagami-m fading channels

A cross-layer design of packet-data transmission with space-time block coding (STBC) over multiple input and multiple output (MIMO) Nakagami-m fading (NMF) channels is presented. Based on the imperfect channel state information (CSI), the closed-form expressions of average packet error rate (PER) and average spectral efficiency (ASE) of the system with a feedback delay are derived, respectively. Due to the feedback delay, the variable threshold method is employed to reduce the effect of imperfect CSI on the system performance. Numerical results reveal that the derived theoretical expressions can effectively evaluate the performance of the system with the delay. The achieved ASE of the system is higher than that of the system with fixed thresholds, but it will decrease while the error probability increasing when the feedback delay becomes large.