Adaptive Multi Lane technique for LTE radio access VoIP

Abstract

This paper describes a novel radio access channel adaptive technique designed for the Long Term Evolution (LTE) VoIP codecs. In previous 3GPP releases, the circuit switched Adaptive Multi Rate (AMR) voice codec has proven robust performance under different radio channel conditions. With the 3GPP Release 8 LTE standards, the circuit switched domain is cancelled, making LTE an all IP system and VoIP the only way to carry voice. Despite that VoIP codecs are well developed for internet applications, these codecs are not designed to adapt according to the radio channel conditions, as in the case of AMR. With the new Adaptive Multi Lane (AML) approach, the system is to stream 1, 2 or 4 lanes of speech frames in parallel according to the radio channel conditions. Each lane has a different fractional speech frame delay increasing the probability of getting out of fading dips. The AML technique has been modeled and simulated over OMNET++ ver4.1 including the INET framework and VoIP tool extension. The VoIP tool has been modified to implement the lane selection algorithm. The resulting speech quality was evaluated using the ITU P.862 PESQ. Simulation results show improvement in the average PESQ MOS readings exceeding 44% compared to the normal single path model. We conclude that the AML is a useful technique for improving VoIP codecs performance in cellular systems.