Code-Division Multiple-Access (CDMA) is one of the leading digital wireless communication methods currently employed throughout the world. Third generation (3G) and future wireless CDMA systems are required to provide services to a large number of users where each user sends data burst only occasionally. The preferred approach is packet based CDMA so that many users share the same physical channel simultaneously. In CDMA, each user is assigned a pseudo-random (PN) code sequence. PN codephase synchronization between received signals and a locally generated replica by the receiver is one of the fundamental requirements for successful implementation of any CDMA technique. The customary approach is to start each CDMA packet with a synchronization preamble which consists of PN code without data modulation. Packets with preambles impose overheads for communications in CDMA systems especially for short packets such as mouse-clicks or ATM packets of a few hundred bits. Thus, it becomes desirable to perform PN codephase synchronization using the information-bearing signal without a preamble.
This work uses a segmented matched filter (SMF) which is capable of acquiring PN codephase in the presence of data modulation. Hence the preamble can be eliminated, reducing the system overhead. Filter segmentation is also shown to increase the tolerance to Doppler shift and local carrier frequency offset. <p>Computer simulations in MATLAB® were carried out to determine various performance measures of the acquisition system. Substantial improvement in probability of correct codephase detection in the presence of multiple-access interference and data modulation is obtained by accumulating matched filter samples over several code cycles prior to making the codephase decision. Correct detection probabilities exceeding 99% are indicated from simulations with 25 co-users and 10 kHz carrier frequency offset or Doppler shift by accumulating five or more PN code cycles, using maximum selection detection criterion. Analysis and simulation also shows that cyclic accumulation can improve packet throughput by 50% and by as much as 100% under conditions of high offered traffic and Doppler shift for both fixed capacity and infinite capacity systems.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-01022007-084014 |
| Date | 02 January 2007 |
| Creators | Rahaman, Md. Sajjad |
| Contributors | McCrosky, Carl, Makaroff, Dwight, Gokaraju, Ramakrishna, Dodds, David E. |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-01022007-084014/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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