Adaptive VoIP Multiplexing in LTE Backhaul

LTE has a distributed system architecture optimized for IP connectivity. Circuit switched technology is not supported by LTE at all; therefore it provides VoIP based voice service only. In LTE, VoIP packets are carried with significant protocol overhead, thus transporting each voice packet separately is a waste of bandwidth. A possible way to improve the bandwidth efficiency of voice service over LTE is to multiplex the packets of parallel VoIP connections into a single transport frame. On the downside, multiplexing requires that some VoIP packets are retained which in turn will increase their end-to- end delay. This paper proposes a multiplexing method, which provides a good balance between bandwidth gain and quality of service by adapting its operation to the actual traffic mix. Three alternative solutions are proposed and investigated with simulations. The results show that VoIP multiplexing significantly improves the bandwidth efficiency of the voice service over LTE with only minor impact on the quality of service.