Abstract—The joint combination of Multiple-Input Multiple-Output (MIMO) technology and relay, known as cooperative MIMO systems, can extremely boost the spectral efficiency of wireless systems. Relevant researches regarding protocol, capacity limit and power allocation for such a system can be easily found in the literature. However, a study on Bit Error Rate (BER) performance which is crucial for this system has received less attention. This motivates us to perform further investigation on this topic. In order to conduct the simulation, the system with single relay and half-duplex decode-and-forward protocol, which is quite simple from practical point of view, is considered in this paper. Our results indicate that it is worth to have relay in MIMO system since relay can provide power saving at least 8 dB comparing with MIMO system without relay at BER of 10−6. Moreover, the use of simple relaying strategy called silent source in multiple-access (MAC) mode does not degrade the BER performance in MIMO relay systems.