This paper describes the measurements made in an urban canyon environment of a relay network scenario to determine the capacity of the multiple-input-multiple-output (MIMO) channel. While varying antenna number and spacing, we measure the channel matrices in the 3.7 GHz band using a 44 switching MIMO channel sounder. The results show that antenna spacing is shown to have less impact than signal-to-noise (SNR) on MIMO channel capacity in a line-of-sight (LOS) environment when physical antenna spacing is selected at four wavelengths. As a result, in an urban MIMO LOS scenario, a base station can provide sufficient data throughput to relay station because most links from base station to relay station have LOS environment and are free from restriction of antenna spacing.

We propose a modified orthogonal transmit diversity (OTD) scheme, which can simultaneously achieve full path diversity and temporal diversity by using symbol splitting. Our proposed method is comparable to space-time spreading (STS) in performance and superior to STS in the cost and efficiency of base station RF devices.