Design and analysis of protocols with QoS guarantees in packet-switched networks

It is a difficult problem to guarantee the end-to-end quality of service (QoS) for the supported applications in multihop packet-switched networks. In this work, an infrastructure is investigated which consists of wireless local networks and a peer-to-peer backbone netnrork (WAN) connecting the local segments. We consider QoS as it pertains to end-to-end packet delay. Meanwhile, other issues such as fairness and packet loss ratio are also taken into account.; For the multihop wireless local network, a new multiple access protocol is proposed by combining a Galois-based scheduling policy with a method called "protocol threading". The protocol guarantees the successful transmission for any packet with an upper bound on delay, which is a function of the local nodal-degree parameter. This relation will always hold in face of topology changes, therefore the protocol is adaptive to the nodal mobility, which is an important advantage in mobile networks. Performance measures of this protocol are investigated based on probabilistic analysis and the property of Galois fields. The comparison between analytical modeling and simulation resulted in at most 5% difference; the throughput and delay are at least as good as the optimal values in Slotted Aloha.; The work also studies the general TDMA protocols used in either cellular networks or any other networks with a fully meshed topology or a broadcast channel. A fundamental relation between fairness and optimal throughput is shown, which demonstrates that, under quite general conditions, optimal system throughput is obtained if and only if the bandwidth of each user is assigned fairly.; For the backbone peer-to-peer system, a novel relation is derived for the worst case end-to-end congestion delay, the maximum allowed source rate and buffer requirement using a simple system model. The relation is described by the Delay Theorem, which is of significant interest in both theory and application. Based on the Delay Theorem, an original call admission control strategy is proposed, which guarantees the end-to-end delay over the backbone with no packet losses. These desirable properties fit perfectly with the recent parameterized QoS requirements defined by the ATM Forum. Additionally, this work also derives an optimal routing protocol which minimizes the probability of a connection request being rejected.; In all, by combining the access protocols in local segments with a network-wise call admission control in the wide area backbone, this work leads to a specific guarantee of QoS for packet delay.