Multiple-input multiple-output (MIMO) communication systems employ multiple antennas at the transmitter and the receiver. Multiple antennas provide capacity gain and/or robust performance over single antenna communications. Traditional automatic-repeat-request (ARQ) techniques developed for single-input single-output (SISO) communication systems have to be modified in order to be employed in MIMO communication systems. In this dissertation, we propose and analysis some ARQ techniques for MIMO communication systems. The basic retransmission protocols of ARQ, stop-and-wait (SW-ARQ), go-back-$N$ (GBN-ARQ), and selective repeat (SR-ARQ), designed for SISO communication systems are generalized for parallel multichannel communication systems. The generalized ARQ protocols seek to improve the channel utilization of multiple parallel channels with different transmission rates and different packet error rates. The generalized ARQ protocols are shown to improve the transmission delay as well. A type-I hybrid-ARQ error control is used to illustrate the throughput gain of employing ARQ error control into MIMO communication systems. With the channel information known at both the transmitter and the receiver, the MIMO channel is converted into a set of parallel independent subchannels. The performance of the type-I hybrid-ARQ error control is presented. Simulation results show the throughput gain of using an ARQ scheme in MIMO communication systems. When the channel state information is unknown to the transmitter, error control codes that span both space and time, so-called space-time coding, are explored in order to obtained spatial diversity. As a consequence, the coding scheme used for ARQ error control has to be designed in order to consider coding across both space and time. In this dissertation, we design a set of retransmission codes for a type-II hybrid-ARQ scheme employing the multidimensional space-time trellis code as the forward error control code. A concept of sup-optimal partitioning of the (super-)constellation is proposed. The hybrid-ARQ error control scheme, consisting of the optimal code for each transmission, outperforms the hybrid-ARQ error control scheme, consisting of the same code for all transmissions.



College and Department

Ira A. Fulton College of Engineering and Technology; Electrical and Computer Engineering



Date Submitted


Document Type





ARQ, MIMO, retransmission protocols, space-time coding