Radio Resource Management in UMTS-WCDMA Systems.

Abstract

Universal Mobile Telecommunications System (UMTS) is a Third Generation (3G) cellular technology representing an evolution of a heterogenous mix of services and increased data speeds from today's second generation mobile networks. UMTS uses Wideband Code Division Multiple Access (WCDMA) as its radio air interface. The main advantage of this is its flexibility in resource management. The implementation of WCDMA is a technical challenge because of its complexity and versatility. Billions of dollars have been spent procuring these air interfaces. To exploit the flexibility of the air interface, development of 'Radio Resource Management (RRM)' schemes are imperative. RRM is comprised of power control, handover control, load control and resource allocation algorithms. These ensure optimum network coverage, maximize the system throughput and , guarantee Quality of Service (QoS) requirements to users having different requirements.

This research investigates mainly the resource allocation and power control algorithms with which the load control and handover control are intertwined. The state of the art is studied and their pros and cons are discussed, which lays the foundation for the need for more efficient RRM schemes that are eventually presented in this research.

The two main schemes considered here are:1)Adaptive Call Admission Control (ACAC) scheme for resource allocation where the system is mathematically modeled as a multi-rate system with priority. Further, a tier based analytical model pertaining to the hierarchical hexagonal cell structure is analyzed and mobility is given importance. 2) Adaptive Uplink Power Control (AUPC) scheme for power control is analyzed where Monte Carlo simulations are used to fine-tune WCDMA link budget parameters. Finally, Location Update (LU) procedures in cellular networks using Bloom Filters is studied where bandwidth gain is given importance. Various performance metrics are observed and two key metrics are given the most importance: the Call Blocking and Call Dropping probabilities. Simulation results are compared to the existing schemes and further strengthened by comparing them to analytical results which validate the entirety of this research.