Handover management based on the number of data frame retransmissions for VoWLAN

Ubiquitous networks enabling access by mobile nodes (MNs) at any time and at any location will consist of innumerable Wireless Local Area Networks (WLANs). In such ubiquitous networks, it is very likely that an MN will traverse several WLANs, due to each having a small service area, during VoIP communication. Thus, a single communication may experience several handovers between WLANs divided into different IP subnets by Internet Service Providers (ISPs), during which the communication quality may be degraded due to packet loss. In this paper, we propose an effective handover management scheme for Voice over IP (VoIP) communication in which the quality is sensitive to packet loss. For this purpose, our handover management scheme employs a transport protocol supporting multiple connections for VoIP communication and makes handover decisions based on a new criterion: the number of retransmissions experienced by a data frame on layer 2. Furthermore, to prevent packet loss during handover and to investigate the wireless link condition, the proposed handover management scheme selects single-path transmission or multi-path transmission according to the number of frame retransmissions. Through simulation experiments, we show that the proposed handover management scheme can promptly and reliably detect the degradation in a wireless link, and can reduce packet loss during handover.