Técnicas de acceso y gestión de recursos para garantizar calidad de servicio en sistemas de comunicaciones moviles basados en CDMA

Alonso Zárate, Luis Gonzaga · 2023 · Crossref

DOI: 10.5821/dissertation-2117-94185

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Summary

This doctoral thesis, authored by Luis Gonzaga Alonso Zárate in 2001, addresses the challenge of guaranteeing Quality of Service (QoS) in third-generation mobile communication systems based on Code Division Multiple Access (CDMA). The research is motivated by the standardization of Universal Mobile Telecommunications System (UMTS) and the need for efficient Medium Access Control (MAC) protocols and resource management algorithms capable of supporting diverse service classes, including conversational, streaming, interactive, and background data. The work aims to design and optimize a new MAC protocol, DQRAP/CDMA, and integrate it with scheduling mechanisms to ensure QoS in both standalone and cellular environments. The study begins by reviewing CDMA principles, power control, and existing MAC protocols such as ALOHA and CSMA variants. It then proposes DQRAP/CDMA, a Distributed Queueing Random Access Protocol adapted for CDMA. The protocol utilizes reservation resources and transmission rules to manage access, featuring mechanisms for collision resolution, automatic traffic adaptation, and flow control. The author performs analytical modeling to evaluate total system delay, including delays from collision resolution and data transmission subsystems. The protocol is further optimized through dynamic code assignment, adjusting the number of minislots per code, and adapting transmission speeds to maximize performance and minimize detection errors in control minislots. To validate the protocol in realistic conditions, the thesis presents simulations within a cellular environment. These simulations incorporate propagation models, power control, user mobility, and handover algorithms (comparing IS-95 and UTRA approaches). The results analyze system performance under standard conditions, the impact of handover mechanisms, active set size variations, and traffic concentration. Additionally, the research extends DQRAP/CDMA to support guaranteed QoS by implementing independent queues for different services and a distributed resource management scheme. This includes a novel "Service Credit" concept for scheduling the transmission subsystem and specific allocation algorithms for the access subsystem. Simulations using traffic models for voice, variable bit rate data, and best-effort data demonstrate the protocol's ability to maintain QoS parameters across heterogeneous traffic loads. The significance of this work lies in its comprehensive approach to integrating MAC layer design with resource scheduling for CDMA systems. By optimizing DQRAP/CDMA and introducing specific QoS management mechanisms, the thesis provides a framework for efficient resource utilization in UMTS networks. The findings suggest that the proposed protocol and scheduling algorithms can effectively handle mixed traffic types while maintaining service quality, offering valuable insights for the implementation and evolution of third-generation mobile standards. The research concludes with recommendations for future integration into UMTS specifications and identifies areas for further investigation in dynamic resource management.

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