Norival R. Figueira

Providing quality of service for wireless links: wireless/wired networks

Over the last ten years, a number of scheduling disciplines have been developed to address the problem of providing QoS guarantees in packet-switched networks. When one considers the integration of wireless links with these networks, difficulties arise in their implementation because of the relatively large and time-varying bit error rates of wireless links, due to impairments that are difficult to predict. We address this problem at the (wireless) link level, where we have developed a link access scheme called remote-queuing multiple access (RQMA). RQMA supports the flexible and efficient allocation of bandwidth for real-time sessions in a way that allows the wireless link to be seamlessly integrated with a wired network that supports QoS guarantees. We describe RQMA, and present performance results.

VirtualQueue: A technique for packet voice stream reconstruction

Statistical multiplexing in packet-switched networks creates problems for packetized voice streams by introducing variable delays on delivered packets. The resulting jitter needs to be filtered so that received voice packets can be reconstructed as a continuous stream at the receiver. One common approach to reconstruction is to play back the receiver voice data after a delay offset from the departure time at the source of the packet stream. While the added delay helps filter jitter, one cannot introduce too much delay, otherwise, interactiveness suffers. This paper presents a new technique to find the necessary delay offset (or play-back delay) to recreate the original voice data stream. This technique gives the user control over the fraction of packets that should arrive in time to be played back so that the added play-back delay can be effectively minimized.