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In this paper a multi-service/multi-rate system using Frequency Division Multiplexing/ Frequency Hopping and Code Division Multiple Access (FDM/FH/CDMA) is investigated. In such a system low bit rate signals (e.g. voice) are spread over the whole allocated bandwidth while higher bit rates data are transmitted over narrow-band frequency slots which are either fixed (FDM) or hopping (FH). The error performance of a two service system (10 kbps voice and 500 kbps data) in two different environments (indoorPic0 cell and outdoor-Micro cell) is evaluated and compared with previous results of pure CDMA in which all signals with different bit rates are direct-sequence spread over the whole allocated bandwidth. 1-IntroductionIn [ 11 and [2] the performance of a multi-serviceimulti-rate pure CDMA system in a fading channel was investigated. The phrase pure CDMA implies that all signals with different bit rates, whether low or high, are direct-sequence spread over the whole allocated bandwidth with different processing gains. The statistics of the low and high bit rates interference, as random variables, for both Gaussian and Rayleigh fading channels were derived and, based on them, bit error probabilities for such a system were calculated. The intention of this paper is to present the results of an investigation similar to that of pure CDMA for a multi-rate Frequency Division MultiplexedFrequency Hopped Code Division Multiple Access (FDMIFHICDMA) system. In such a system low bit rate signals (e.g. voice) are spread over the whole bandwidth as in the case of pure CDMA but higher bit rate data is transmitted over narrow-band frequency slots which are either fixed (FDM) or hopping (FH). The investigation starts with the characteristics of narrow-band and wide-band interference in section-2. In section-3 the parameters for this investigation are set and the environments (channels) used are described. Error performances of high bit rate FDM and FH signals and low bit rate spread spectrum DS signals in fading channels are discussGd in section 4. Finally section-5 is the conclusion.

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