Information Technology Journal1812-56381812-5646Asian Network for Scientific Information10.3923/itj.2010.305.311WangKai-Hua ZhangChuan-Qing XuJi-Lin 2201092Traditional hybrid automatic repeat request (HARQ) protocols extract time diversity in a scalar fading channel. The performance depends critically on the channel variation over retransmissions. The slow fading channel model considered allows no time diversity for the HARQ protocols to exploit. But traditional protocols can not effectively exploit spatial diversity provided by a Multiple Input Multiple Output (MIMO) system. A new Alamouti-based HARQ transmission scheme for a MIMO system in a slowly varying channel is proposed. This new scheme is a combination of the packet combining HARQ and the Alamouti Space-Time Coding (STC). This technique increases the efficiency of HARQ packet transmission by exploiting both the spatial and time diversity of the MIMO channel. It uses the full diversity of Alamouti STC and the added gain of the packet combining scheme to provide reliable communication. The Packet Error Rate (PER) analysis of space-time coded MIMO-HARQ is presented. An n-dimension Pair Wise Error Probability (PWEP) analysis of the optimal Alamouti-based HARQ protocol is derived. Simulation results show that this new scheme outperforms traditional Chase Combining (CC) and reveal the gain of ARQ feedback in space-time coded MIMO systems.]]>Alamouti, S.,19981614511458Carvalho, E. de and P. Popovski, 200812441443Chase, D.,198533385393Chuang, A., A.G.I. Fabregas and L.K. Rasmussen,20085439683986Kim, T. and M. Skoglund, 20075327432759Koike, T., H. Murata and S. Yoshida,2004529192923Oh, M.K., Y.H. Kwon and D.J. Park,20044589592Sesia, S., G. Caire and G. Vivier,20045213111321Tarokh, V., N. Seshadri and A.R. Calderbank,199844744765Zheng, K., H. Long, L. Wang and W. Wang,20072007pp: 35433547