QoS guarantees in wireless /mobile networks.

Abstract

Recent years have witnessed a tremendous growth of research and development to provide mobile users a means of seamless communication through wireless media. This dissertation examines how to provide diverse Quality-of-Service (QoS) to mobile users generating/receiving heterogeneous traffic. It addresses QoS at two different levels: (1) packet-level QoS such as packet delivery delay, throughput, and error performance; and (2) connection-level QoS associated with connection setup and management. To provide packet-level QoS, we develop a unified architecture for wireless LANs. We first define a polling-based medium access control (MAC) protocol for uplink accesses. Then, we address resource reservation, packet scheduling, connection-admission control, and how to handle location-dependent channel errors. With the proposed protocols, the delivery delays of real-time packets are bounded at the cost of some packet losses depending on the channel condition while allowing mobiles to have loss-free and fair accesses for transmitting non-real-time traffic. We also develop an uplink code-division multiple access (CDMA) system with various packet-level QoS provisioning for wide-area cellular networks. Based on a transmission-rate request MAC protocol, we address the issues of resource reservation, packet scheduling, and connection-admission control. To satisfy the pre-defined error-performance requirements for each traffic class, we use a concatenated RS/convolutional code, and develop a new scheme for allocating mobiles appropriate power levels. For connection-level QoS, we propose predictive, adaptive bandwidth reservation for hand-offs and admission control for newly-requested connections so as to keep the hand-off dropping probability below a pre-specified target assuming that each connection requires a certain amount of bandwidth. Our schemes utilize history-based mobility estimation to predict user mobility. For the purpose of comparison, we also consider five other existing schemes. Through detailed simulations of various scenarios, we show the superiority of the proposed schemes to the other schemes. Finally, we propose a unified architecture for wireless bandwidth management utilizing the concept of adaptive QoS. The allocated throughput to each connection is adapted depending on time-varying channel conditions and user mobility, where a connection's acceptable throughput range as well as adaptation constraints are specified during the admission control phase. The BS allocates bandwidth to each connection so as to maximize the service provider's aggregate reward. The proposed adaptive and non-adaptive schemes are compared to demonstrate the advantages of the adaptive scheme.