Higher-Level Multi-Carrier Modulation and Its Implementation
نویسندگان
چکیده
|We introduce a CDMA system based onmulticarrier spread spectrum (MC-SS) with one identical code for all users. In general, the employment of a multi-carrier transmission technique would increase the dynamic range of the correspondent lowpass time signal, and therefore would require a highly linear power ampli er. By carefully designing the code of a MC-SS signal a signi cant decrease of several orders of magnitude in dynamic range can be obtained. The spectral properties of the multi-carrier signal are not a ected by the code. In some spread spectrum systems, however, it is desired to support di erent data rates over the same modem by leaving the spreading code unchanged. If the signal-tonoise ratio (SNR) is su ciently high, the reduced dynamic range of the unmodulated multi-carrier signal allows for a multi-level modulation of the narrowband signal for higher rate transmission. A pair of surface acoustics wave (SAW) lters can be used for both spreading and despreading the signals at low cost. Di erent implementations for MC-SS are shown in this paper.
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