Performance of VoIP in Presence of MIMO Interference in OFDMA (LTE) Networks

Voice over Internet Protocol (VoIP) being highly sensitive to errors is usually transmitted using diversity mode (Space Frequency Block Coding (SFBC)) of Multiple Input Multiple Output (MIMO) in Orthogonal Frequency Division Multiple Access networks. In Long Term Evolution, the Closed Loop Rank - 1 (CLR-1) being more error resilient than higher order MIMO modes is also one of the attractive options that can be used for VoIP transmission. This work presents an algorithm for Semi-Persistent VoIP scheduling using CLR-1 MIMO mode. The performance is evaluated following ITU specified test methodologies. Since it requires frequency reuse-unity to be used, it is expected that cell edge users will experience heavy co- channel interference. As MIMO communication is affected differently by different interfering MIMO modes, comparison of several combinations of using SFBC and CLR-1 in desired and interfering link is presented for the proposed algorithm. Finally, predication of PRB usage and VoIP capacity for CLR- 1 are also shown.