With emerging multi-media wireless applications, there is a need for next-generation W-CDMA to be designed to support variable rate traffic. Several schemes have previously been proposed to support variable rate transmission, namely, variable spreading gain (VSG), multicode transmissions and fixed spreading gain (FSG). In this paper, a universal framework to evaluate and compare the various variable rate transmission schemes in terms of bit error rate (BER), power and required bandwidth is proposed. The framework also provides for the synthesis of the power assignment that delivers a specified BER to heterogeneous variable rate sources under each scheme.

In a code division multiple access system, the quality of service delivered to a user depends on its transmission power and the level of multiple access interference. When variable bit-rate users are statistically identical, conventional power control (uniform) is used to guarantee fairness of service to the users in the system by avoiding the near-far problem, However, when the probability of a user being active is high, the system might experience a low throughput due to increased congestion in the network. In such a situation, it may be possible to improve the system throughput by employing non-uniform power control policies. These power control schemes may be designed to offer the same quality of service to each of the individual users. Analysis of various power control policies are examined in this work.

In this work, the region of achievable quality-of-service (QoS) is precisely described for a system of real-time heterogeneous variable bit rate (VBR) sources competing for slots (packet transmission times) of a time division multiple access (TDMA) frame. The QoS for each application is defined in terms of a maximum tolerable packet-dropping probability. Packets may be dropped due to delay violations and channel induced errors. The region of achievable QoS is precisely described for an interference/resource limited network by considering the underlying TDMA-multiple access control (TDMA-MAC) structure and the physical channel. A simple QoS-sensitive error-control protocol that combats the effects of the wireless channel while satisfying the real-time requirements is proposed and its impact on the region of achievable QoS is evaluated. The results presented here clearly illustrate the negative impact of a poor channel and the positive impact of the employed error-control protocol on the achievable QoS. The region of achievable QoS vectors is central to the call admission problem, and in this work, it is used to identify a class of scheduling policies capable of delivering any achievable performance.

The focus of this paper is on determining the call admission region and scheduling policies for a time-division multiple-access (wireless) system supporting heterogeneous real-time variable bit rate applications with distinct quality of service (QoS) requirements and traffic characteristics. The QoS is defined in terms of a maximum tolerable packet delay and dropping probability. A packet is dropped if it experiences excess delay. The call admission region is established for policies that are work-conserving (WC) and that satisfy the earliest due date (EDD) service criterion (WC-EDD policies). Such policies are known to optimize the overall system performance. In addition to the determination of the call admission region, this study leads also to the construction of scheduling policies that deliver any performance in the region established for WC-EDD policies. Finally, an upper bound on the call admission region that can be achieved under any policy (not limited to the WC-EDD policies) is determined.

In Wireless ATM networks transmission resources are shared among geographically disperse applications with diverse Quality of Service (QoS) requirements and traffic characteristics. To provide QoS guarantees and use the bandwidth efficiently, call admission and scheduling functions are necessary. These functions should ensure the delivery of the target QoS to the supported applications while achieving statistical multiplexing gains, without explicit and continuous exchange of information between sources and scheduler. In this paper the problem of sharing resources (slots of an up-link TDMA frame) among heterogeneous Variable Bit Rate (VBR) applications with diverse QoS requirements is addressed. The QoS requirements for each application is defined in terms of a maximum tolerable packet delay and dropping probability; a packet is dropped if it experiences excess delay. The region of achievable QoS vectors is established for policies that are work-conserving and satisfy the earliest due ...