Crest factor reduction in multicarrier transmission schemes

A method of reducing the crest factor of a transmitted signal in a multicarrier transmission system which uses a set of carriers spaced apart in frequency, the method comprising:

• receiving a data signal for transmission;
• mapping the data signal to a parallel set of constellation values, where each constellation value determines modulation of one carrier in the set of carriers;
• applying a frequency domain-to-time domain transform to the set of modulated carriers to generate a time-domain signal;
• detect when the time-domain signal exceeds a predetermined criterion;
• modifying the constellation value of at least one of the carriers, wherein a carrier is selected for adjustment on the basis of a number of bits allocated to that carrier.

A transmitter for a multicarrier transmission system, comprising:

• an input for receiving a data signal for transmission;
• a mapper arranged to map the received data signal into a set of complex data symbols, where each data symbol determines modulation of one carrier in a set of carriers which are spaced in frequency;
• a frequency domain-to-time domain transform stage arranged to convert the set of modulated carriers to a time-domain signal;
• a peak detector arranged to detect when the time-domain signal exceeds a predetermined criterion;
• a constellation modifier arranged to modify the constellation value of at least one of the carriers in the time-domain.

A method of reducing the crest factor of a transmitted signal in a multicarrier transmission system which uses a set of carriers spaced apart in frequency, comprising:

• inputting a data signal for transmission;
• mapping the received data signal into a set of complex data symbols, where each data symbol determines modulation of one carrier in a set of carriers which are spaced in frequency;
• performing a frequency domain-to-time domain transform to convert the set of modulated carriers to a time-domain signal;
• detecting when the time-domain signal exceeds a predetermined criterion;
• modifying the constellation value of at least one of the carriers in the time-domain.