Channel Estimation and Resource Allocation of a WCDMA System in a Very High Mobility Environment
Date Issued
2009
Date
2009
Author(s)
Yang, Ya-Yin
Abstract
In the recent years, global mobile communication systems have gradually developed from 2G to 3G, and even to next generation systems. At present, mobile communication systems can provide services such as voice, web-browsing, electronic mail, and even multimedia services at a high transmission rate. The bandwidth that communication services can provide is dependent on the conditions of the channels. When the channel''s conditions are not ideal, such as when the user is in a moving environment, the bandwidth of the communication service available would be limited. Taiwan''s High Speed Rail officially started operations in 2007. The mainstream trend of the current 3G mobile communication systems is the 3GPP WCDMA. Thus, how to provide 3G services on a high speed vehicle is a very critical question.hannel estimation plays an important role in the performance of coherent receivers. High mobility may cause conventional symbol-level channel estimation to yield several errors. In this dissertation, we propose a chip-level channel estimation for downlink of a WCDMA system to support high mobility. In an uplink, a sub-symbol-level channel estimation is suggested to resist high mobility. Interpath interference cancellation and a moving average filter are added against interpath interference and noise.n addition, data distribution on the downlink channel is a widely-discussed issue in the research community, highlighting the importance of resource allocation to competing services on the downlink. Under given per-cell total power budget, we are able to formulate power allocation as a mathematical nonlinear optimization problem in an OVSF-CDMA system. We find that our NLP problem in an additive white Gaussian noise (AWGN)/ a Rayleigh fading/ a Rayleigh fading with diversity channel is solvable by Frank-Wolfe Algorithm or lambda-method. Moreover we incorporate the design of packet scheduler with consideration of priority, channel state and QoS requirements in deciding data transmission rates.
Subjects
WCDMA
channel estimation
high mobility
interpath interference cancellation
power allocation
QoS scheduling
Type
thesis
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