A robust mechanism to enable seamless handover of streamed IPTV in a WLAN is presented. Handover in a wireless network is usually based on signal strength measurements, but that approach does not consider levels of congestion within the network. Here, the case of stationary nodes with varying levels of network congestion is considered. A scheme that analyzes the jitter is used to establish the relationship between congestion and loss in WLANs. This Moving Average of Negative Jitter is used as the basis of a handover scheme which can minimize loss. The handover scheme uses a client with two simultaneous connections to the same server through two separate WLANs, and it is shown that the client can compare the jitter in the two streams to determine which network delivers the best performance; this information is then used to determine when to perform a handover. The proposed scheme is implemented and results are presented that show the successful handover of an RTP over UDP stream in a live WLAN environment. The test scenario used is aimed at ldquoOver-The-Toprdquo service delivery, but the core algorithm is expected to be more broadly applicable.
In the currently proposed schemes for performing a vertical handover between wireless networks, it is common for a substantial break in connectivity to occur that would be unacceptable for streamed video. This paper proposes a scheme that ensures packets are not lost, through the use of soft handover. It is shown that the client can decide when to perform a soft handover by using the difference in packet delay between the two streams. The scheme is implemented and results are presented that show the successful handover of an RTP stream using this scheme in a test bed that emulates network conditions.
This paper considers the adaptation of video for quality-of-service (QoS) in a system containing a video server linked to a mobile client. The video server is linked to the wireless network via a dedicated wire link that is lightly loaded. Locating the adaptation functionality at the transmit-side of the wireless link rather than at the server is proposed. The research work to determine the adaptation algorithm is outlined.
