University of Twente Student Theses


Path search algorithms for application in W-CDMA systems

Damstra, M.C. (2004) Path search algorithms for application in W-CDMA systems.

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Abstract:The CADTES and SAS groups of the EEMCS faculty are working on the Adaptive Wireless Networking (AWGN) project. As part of this project adaptive algorithms are developed for digital signal processing in W-CDMA systems. One of these algorithms is the path search algorithm that estimates the delays of the paths between a transmitter and a receiver that are caused by reflections. Several options exist for implementing the path search algorithm. One of the questions posed within the AWGN project is: to what extent will it be useful for the path search function to switch between different algorithms, as the conditions between transmitter and receiver change? First, this document presents an overview of path search algorithms from literature. About twenty papers are discussed, the algorithms they describe have been compared with each other on sixteen points. Based on the similarities that are discovered, the algorithms are classified in three classes: algorithms using a Power Delay Profile (PDP), algorithms based on a Maximum Likelihood Estimation (MLE) method and subspace-based algorithms. Next, an algorithm is selected from each class. Both the Power Delay Profile and the Maximum Likelihood algorithms are implemented, the subspace algorithm is analyzed in theory only. In order to set up meaningful simulations channel models and simulation scenarios are investigated. The available simulator is discussed, as well as the modifications that were made. The algorithms' performance is determined by simulation, results show that the MLE algorithm outperforms the PDP algorithm in most situations. The MLE algorithm however requires more computations under all circumstances. In view of this trade-off between performance and number of computations the MLE algorithm should be used in case of closely spaced paths, if time-variant path delays need to be estimated and if strong Doppler effects occur. BER simulations will have to be carried out to quantify the benefits of selecting the MLE algorithm in these cases.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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