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UBC Theses and Dissertations

Differentially detected MSK and GMSK modulation schemes in CCI channels for mobile cellular telecommunication systems Shin, Soon Sun


Continuous Phase Modulation (CPM) has come under close scrutiny for the last decade because of its excellent spectral properties and power efficiency. The thesis looks into two popular members — Minimum Shift Keying (MSK) and Gaussian Minimum Shift Keying (GMSK). The latter has been adopted as the standard transmission for the Pan-European all-digital mobile cellular network. The first part of the thesis deals with the problem of analyzing and evaluating the performance of differentially detected Minimum Shift Keying (MSK) signals in the presence of additive Gaussian noise and Co-Channel Interference (CCI). For CCI, a general model is considered, which additively perturbs the transmitted signals and consists of an arbitrary number of statistically independent interferers that also employ MSK signals. The performance analysis is based upon the derivation of the phase angle distribution of the received corrupted signal. By employing a Fourier-Bessel series expansion technique, it was possible to analytically evaluate very efficiently and accurately the performance of such systems. Various bit error rate (BER) performance evaluation results are presented as a function of the Signal-to-Noise Ratio (SNR) with the Carrier-to-interference (C/I) ratio and the number of interferers as parameters. The asymptotic case where the number of interferers approaches infinity is also investigated. Some of the analytical BER performance evaluation results were also verified by means of computer simulation. In the second part of the thesis, the performance of conventional and decisionfeedback differential detection receivers for GMSK signals transmitted in the presence of CCI and AWGN is evaluated by means of computer simulation. Again for the interference, a general model is adopted, which includes N statistically independent static as well as Rayleigh-faded CCI. Various BER performance evaluation results have indicated that the decision-feedback receivers under investigation perform better as compared to other conventional receiver structures such as 1- or 2-bit differential detectors. Especially significant BER improvements have been obtained for the static CCI channel. For example, it was found that with C/I = 14 dB, the performance of a 2-bit decision feedback differential receiver outperforms a conventional 2-bit differential detector by more than 14 dB (at a BER of 10-³). For CCI with fading, there is less improvement: they result mainly in error floor reductions of about half an order of magnitude. By comparing the performance of static and faded CCI, it was found that for a given C/I, the performance of the former would depend on the number of interferers whereas this is not the case for the latter.

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