A multi-carrier transmission method in which the symbol rate can be decreased in proportion to the number of carriers of the multi-carrier system is also an effective technique to mitigate induced waveform distortion. The waveform factor may be used to assess the relationship between symbol rate and modulation method for a particular outage budget. This relationship is given in a pictorial form in Recommendation ITU-R F.1093, from which the maximum symbol rate that may be transmitted for a given modulation scheme may be established, once an outage budget is specified.
If the gross data rate to be transmitted exceeds the corresponding value calculated from the symbol rate in the above method, then the use of multi-carrier techniques may be necessary. It is also possible to determine the number of carriers needed in the multi-carrier case.
In general, the use of a multi-carrier method requires the development of higher linearity power amplifiers and the optimization of sub-carrier spacing to avoid intermodulation distortions and intra-system interference produced by adjacent carriers of the same multi-carrier system.
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