Modeling and resource management in wireless multimedia WCDMA systems
Abstract (Summary)The focus of this thesis is on modeling and optimal resource management in wireless multimedia wideband code-division multiple access (WCDMA) systems. Resource management in CDMA systems has two major roles: to increase spectral efficiency by controlling cochannel interference, and to accommodate multimedia services by proper adjustment of the allocated resoarces. In this thesis, the system model sup ports a new class of services with limited delay tolerance in addition to real time and delay insensitive services which have been already considaed in the literature. The basic control variables in CDMA resource management are transmit powers, data rates, and base station assignments (handoff decision). Previous works have induded a subset of these variables in their resource management algorithms. In this thesis, these control variables are combined in a mathematical programming problem which maximizes the profit gained by a wirelesa mdtimedia service provider subject to satisfying the service and quality of service (QoS) requirement for each user. The profit is obtained as the Werence between the network revenue and cost. A pricing scheme has been developed to map the network throughput onto the network revenue and the handoff switching ovahead onto a certain cost. In this prieiag scheme, every usa pays proportionally to its instantaneous data rate md quality of service. The mathematical programming problem is analyzed, restructured, and solved for single- and multi-cd systems. The single-ceIl solution has the advantage of low complexîty and global convergence in cornparison with the previous work. MrUmum achievable throughpat (capacity) of a single c d is mathematically evaluated aad has been used as the benchmark for performance measare of single- and mdti-cell systems. For multi-cd systems, diffkrent solution approaches lead to différent redts. The best redt is generated by the improved mixed-integer nonlinear programming (1-MINLP) algorithm which achieves np to 94% of the capacity in a network with 9 base stations, equivalent to a reuse efficiency of 0.94. The sensitivity of the resource management solution to erroneous input data (path gains) is examined. It has been shown that the higher the ca- pacity utilbation, the higher the vuinerability to estimation enor. As a practical issue, resource management at different operation Ievels (centralized, partially de- centralized, decentralized, and M y decentralized) is discussed. To facilitate the centralized implementation, a more practical version for the 1-MINLP algorithm has been developed. The centralized and partially decentrahed schemes are pre- ferred for thek high performance and flexibility. The contribution of this thesis is conhed to the reverse link of WCDMA systems. We have assumed that neces- sary mechanisms to perform handoff procedures, when a user is assigned to a new base station, exist and have not addressed soft handoff. A resource management algorithm that combines the result of this research with the well known dosed-loop power control is suggested to enhance reverse-link FDD-mode resource management in IMT-2000, the global standard for third-generation wireless systems. A part of this research has been reported in [l, 21.
Source Type:Master's Thesis
Date of Publication:01/01/1999