An implementation design of a cross-layer handover method with multi-path transmission for VoIP communication

This paper presents an implementation design of a handover method for VoIP communication, namely Frame-retry-based handover method with Multi-path Transmission (FMT). Because VoIP communication significantly suffers from packet losses occurring at handover, the FMT uses the frame-retry information obtained from the MAC layer through a cross-layer architecture as a handover trigger and then performs handover accordingly with multi-path transmission to reduce packet losses around the handover. In the previous paper, we proposed the FMT and examined its theoretical effectiveness in extensive simulations. In this work, we design the implementation and examine the effective performance in a real environment because typically there are some system constraints in an OS. Actually, depending on design, the implementation can often degrade the system performance even if the method shows good theoretical performance in mathematical analysis and simulation. In this paper, we first show the implementation design of the FMT on a Linux OS. This includes a novel asynchronous cross-layer design to achieve the collaboration between the two layers (i.e., the MAC and transport layer) while avoiding degradation of system performance. We then provide an implementation of all necessary functions for handover operations supporting VoIP communication by using the proposed cross-layer architecture. We finally examine the prototype system in a real environment in terms of effectiveness of the frame retry-based handover trigger, the multi-path transmission, and voice quality by comparing the FMT with comparative methods. The experimental results show that the FMT efficiently maintains voice quality with low additional network load in a real environment. (C) 2013 Elsevier B.V. All rights reserved.