Kalyan Basu

Modeling QoS degradation in multimedia wireless networks

We propose call degradation and admission strategies based on modeling quality-of-service (QoS) degradation of multirate traffic for third generation multimedia wireless network. The real-time traffic is classified into K classes based on the bandwidth requirements, where a class i call uses i channels. To increase the carried traffic in an overloaded system, some of the ongoing calls release channels that they are using and enter a degraded mode of operation. Two orthogonal QoS parameters called carried traffic and bandwidth degradation are defined, and a cost function describing the total revenue earned by the system from a bandwidth degradation policy is formulated. This cost function model is extended to incorporate a call admission policy, and methods are shown to compute the optimal call admission and degradation policies which maximize the effective revenue earned. Detailed simulation experiments are conducted to validate our proposed model.

Microcell technology solution for wireless local loop applications

Since cellular system was introduced in early 1980s, the capacity was always one of the major areas to improve, investigate and research. The application of wireless as local loop access technology increased that demand on access capacity considerably due to very high traffic rate of the local loop customers. The microcell can be used as a capacity solution for the local loop application. A microcell underlay in an exiting wireless access network is considered as a strategy to achieve a high system performance and a broad coverage. High traffic areas are covered by the underlaying microcells while the macrocells cover the low traffic areas and provide an overflow group of channels for clusters of microcells. This paper is restricted to the considerations for a fixed wireless access network with a microcell underlay. The main objective is to evaluate the system capacity gains. The issues of RF planning and modelling are not addressed. A queueing model which captured the main traffic characteristics of the network with a microcell underlay is formulated from which we give an optimization algorithm to evaluate the system capacity gains of the network due to the microcell underlay. A study of an urban network shows that the system capacity can be significantly increased by deploying the microcell underlay.