Multiple-input multiple-output (MIMO) with spatial multiplexing can enable the maximum capacity transmission in a line-of-sight (LOS) environment using a feasible array size for millimeter-wave (mmWave). Typical applications for mmWave LOS-MIMO are fixed wireless access such as small cell backhaul and data centers for high data rate wireless communications. In this paper, we derive exact expressions of eigenvalues, capacity, signal-to-interference-plus-noise ratio (SINRs) and bit error rate (BER) of zero forcing (ZF) linear receiver as a function of array design for 3×3 and 4×4 UCAs in LOS-MIMO channels. The expressions of capacity and BER are validated via simulations and tested under different array parameters. We show that simulation results are closely agreement with the analytical results, and mmWave LOS-MIMO with UCAs is not sensitive to deviations from the optimal array parameters.