A novel direct sequence spread spectrum wireless modem based on frequency shift keying
Date
1995
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Abstract
A Direct Sequence Spread Spectrum (DSSS) wireless modem system based on Frequency Shift Keying (FSK) is introduced and studied in this thesis. The modem is designed to support data rates from as low as 1200 bps to as high as 100 kbps, which results in a variable-.modulation index for the FSK modulation. For the conventional frequency modulation system, the modulation index is kept small to achieve the best performance as well as the most efficient bandwidth usage. Using DSSS, the transmitted signal occupies a much wider bandwidth than the information signal. Therefore, bandwidth efficiency is not an issue for this system. However, a large modulation index may degrade the system performance. For the two post detectors considered, single sample detector and integrateand-dump detector, the thesis demonstrates that the performance degradation from a large modulation index is significant for the single sample detector, but very small for the integrate-and-dump detector. The thesis also shows that the single sample detector provides a marginal processing gain, which does not change when the length of the Pseudonoise (PN) code increases. The integrate-and-dump detector produces a very good processing gain for the system.
Performance degradation caused by the non-perfect PN code synchronization is also analyzed. This degradation is significant when intermittent tracking is employed. Better performance can be achieved by using continuous tracking, such as the tau-dither tracking scheme.
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Bibliography: p. 102-105.
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Citation
Tan, W. (1995). A novel direct sequence spread spectrum wireless modem based on frequency shift keying (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/19687