A QoS-based Hybrid Multiple Access Transmission Strategy in WCDMA Downlink
| Autor: | Hao-Wei Chang, 張浩偉 |
|---|---|
| Rok vydání: | 2002 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 90 WCDMA (Wideband CDMA) is the primary candidate for the radio access technology with high data rate capability for the third generation (3G) cellular systems. Current 2G systems including the most popular GSM and an upgrade extension of GPRS have provided acceptable voice service and low bit rate data service. However, the main goal of the 3G systems is trying to further support multi-service including real-time and non real-time traffics in better quality. As Internet grows up, data services of video streaming and web browsing become more attractive but the data transmissions are asymmetric so that the downlink demands are much higher than the uplink ones. It is clear that the downlink is the bottleneck and we concentrate on improving the quality of service (QoS) of the downlink. In this thesis, we devote to decrease the mean packet delay for real-time traffics and the bit error rate (BER) for non real-time traffics. Additionally, we try to increase the grade of service (GOS) and the throughput. Four issues are carefully proposed and evaluated in this thesis: (1) Radio access. (2) Admission control. (3) Power allocation. (4) Scheduling. A new hybrid multiple access (HMA) transmission strategy that integrates the traditional mutli-access mode and the novel uni-access mode is proposed to decrease the mean packet delay, bit error rate (BER) and increase the throughput. The HMA provides an approach to choose transmission mode from either uni-access or multi-access that guarantees higher QoS provision. After QoS provision measurements of the target base station, we design an admission control policy based on QoS threshold to deal with real-time and non real-time calls from handoff or new arrival. A sufficient but not superabundant power allocation scheme is derived because the capacity of a WCDMA system is interference limited. We also propose a new scheduling algorithm including the earliest deadline first (EDF) for real-time traffics and the static priority scheduling (SPS) for non real-time traffics to meet the delay and BER requirements respectively. In order to further make analytical decisions between uni-access and multi-access transmission mode, a throughput optimization extension for the HMA is proposed. The throughput gain is our objective but the QoS provision especially the mean packet delay is considered at the same time. Only the radio access network is taken into account and the QoS provision is evaluated. The performance analysis is carried on a dynamic simulation environment including multiple cells, four traffic types, hard handoff and inter-cell interference. The results show that the HMA outperforms the general multi-access CDMA system with better GOS, lower mean packet delay, lower BER and higher throughput. Our proposed system architecture as well as algorithms including radio access, admission control, scheduling and power allocation are presented in chapter II. The Simulation model and results are described in chapter III. Chapter IV concludes this thesis. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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