Transmission Timing in WCDMA terminals

Power control is one of the technologies used to utilize the radio resources as efficient as possible in WCDMA. The transmission power is adjusted to transmit with the lowest power level possible while the required received signal quality is maintained. Since there are large variation in channel quality over time, the power has to be adjusted to compensate for these variations. During moments of bad channel conditions a high transmission power has to be used which will to a greater extent interfere with other users in the system.To solve this problem a concept called transmission timing was proposed. The basic idea is that the transmitter avoids data transmission during the short periods of bad channel conditions caused by fast fading. Higher bit rates can be used to compensate for this when the channel conditions are good.In this thesis the performance of transmission timing applied to uplink data transmissions is evaluated…


1 Introduction
1.1 Background
1.2 Problem Specification
1.3 Objectives
1.4 Delimitation
1.5 Thesis Outline
2 Cellular Radio Communication
2.1 Radio Channels
2.1.1 Fading
2.1.2 Time Spread
2.2 Rake Receiver
2.3.1 Architecture of UMTS
2.3.2 Spread Spectrum Communications
2.3.3 Separation of Uplink and Downlink
2.3.4 Uplink Transmission
2.3.5 Handover
2.4 Radio Resource Management
2.4.1 Power Control
2.4.2 Interference
2.4.3 DRAC
3 Uplink Transmission Timing
3.1 Implementation of the Algorithm
4 Theoretical Analysis
4.1 Transmitted Power Reduction
4.1.1 Probability Distribution of Fast Fading
4.1.2 Requirements on Received Power
4.1.3 Mean Transmitted Power
4.1.4 Numerical Example
4.2 Abrupt Change in Power Gain
5 Simulations
5.1 Single User System
5.1.1 Parameter Tuning
5.1.2 Shorter TTI-length
5.1.3 Transmission Power Reduction
5.1.4 Adjacent Cell Interference
5.1.5 Abrupt Change in Channel Gain
5.1.6 Power Consumption at Different Activity Factors
5.1.7 Power Reduction at Different Speeds
5.2 Multiuser System
5.2.1 Instability Due to Aligned TTI:s
5.2.2 Interference Reduction
5.2.3 Abrupt Change in Load
6 Summary
6.1 Conclusions
6.2 Suggestions to Further Studies
A System Parameters

Author: Törnqvist, David

Source: Linköping University

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