Capacity and admission control schemes in multimedia DS-CDMA wireless networks

This work addresses the capacity estimation and admission control problems, in DS-CDMA cellular networks with multi-media traffic, in three distinct parts. Models for capacity estimation are developed. Then, algorithms for admission control algorithms that regulate user transmission rates and powers are presented. Finally, priority service schemes are developed and analyzed for link bandwidth partitioning.;First, the capacity of a multi-code DS-CDMA cellular architecture supporting integrated (voice and data) traffic is analyzed. The capacity estimate (on the uplink) is the number of voice users and data users, at different data rates, that the system can support with QoS guarantees (frame error rates, outage probability). The capacity estimates are based on models that consider both perfect and imperfect power control, different user distributions in the cell and the coverage trade-off resulting from hand-set power limitations. The analysis investigates the effect of important factors on capacity, such as: (1) Received power levels for the different classes of users, (2) Data user activity (3) Localized interference from high power/rate data users. The results obtained are useful in designing power allocation and burst-level admission control strategies to optimize the capacity.;The problem of admission control in a DS-CDMA network carrying a heterogeneous mix of traffic is addressed next. In an interference limited system such as DS-CDMA, admission of a new user impacts the performance of all other users, as well as the system capacity. The admission process is concerned with two factors: (1) Maintaining the QoS of active users (2) Allocating bandwidth to new users. We propose a simple power control algorithm and prove that it is optimal in the sense of maintaining active link quality while maximizing free capacity for new admissions. We also propose a set of algorithms that assign the transmission rates to data users in different DS-CDMA architectures. These algorithms model the constraints arising from the data rate requirements of the users as well as the power limitations of their power budgets and are designed to maximize the overall carried traffic (throughput).;Priority based link-bandwidth partitioning is required to support services, having diverse QoS (delay, throughput) requirements. A new class of service disciplines, termed "batch and prioritize" or BP admission control (AC), is proposed. The BP algorithms use the delay tolerance of applications to batch requests in time slots. Bandwidth assignment is made either at the end of the slot, or during the slot, on a priority basis. Analytical and simulation models are developed to quantify the performance of the BP schemes. The results are compared with those obtained for a First-Come-First-Served (FCFS) service discipline. In a system with applications requiring multiple transmission rates, the class of BP schemes trade-off the delay and loss tolerance of applications to improve the net carried traffic on the link. Further, such schemes enable an easy implementation for adaptive prioritization, where the degree of precedence given to an application varies with offered load and the link capacity.