Peak power reduction method for wireless communication systems and corresponding transmitter
A peak power reduction method for wireless communication systems is proposed in which a constellation shaping is applied on input data symbols in order to reduce the peak power of the signal samples to be transmitted by the communication system. According to the invention, the symbols are modified using functions each representing the contribution of a symbol to the output signal samples of large magnitude.
1. Peak power reduction method for wireless communication systems using transform based signal formats such as OFDM and CDM communication systems,
comprising:
applying a constellation shaping for modifying the representation, in a signal constellation, of possible values of transmitted data symbols generating the signal samples to be transmitted by the communication system,
wherein the symbols are modified using functions each representing the contribution of a symbol to the output signal samples of large magnitude.
2. Method according to claim 1 , further comprising:
for each data symbol, computing the function representing the contribution of said data symbol to the output signal samples of large magnitude to be transmitted by the communication system;
identifying the functions corresponding to the strongest contribution;
modifying the value of the symbols having the identified functions, and;
updating the signal samples to be transmitted by the communication system on the basis of the modified values of the data symbols.
3. Method according to claim 1 , wherein the values are modified by applying functions elaborated using the said identified functions having the strongest contribution, respectively.
4. Method according to claim 1 , wherein all the values that are modified are modified using identical quantities.
5. Method according to claim 1 , wherein the value of the symbols is modified by modifying the amplitude of the symbols.
6. Method according to claim 1 , wherein the value of the symbols is modified by modifying the phase of the symbols.
7. Method according to claim 2 , wherein computing the said function representing the contribution of the data symbol, identifying the function corresponding to the strongest contribution, modifying the value of the symbols and updating the output signal samples are performed iteratively.
8. Method according to claim 1 , wherein the constellation shaping is performed on a Phase-Shift Keying (PSK) signal constellation.
9. Method according to claim 1 , wherein the constellation shaping is performed on a quadrature amplitude modulation signal constellation.
10. Transmitter for wireless communication system using transform based signal formats such as OFDM and CDM communication systems, for carrying out a process according to claim 1 , wherein the system comprises a first circuit for computing output signal samples corresponding to input data symbols, a second circuit comprising means for calculating, for each data symbol, a function representing the contribution of the symbol to the output samples of large magnitude, means for identifying the function corresponding to the strongest contribution and means for modifying the representation of the data symbols in a signal constellation.
11. Transmitter according to claim 10 , wherein the transmitter is a transmitter for CDM or CDMA Communication System or a transmitter for OFDM or OFDMA Communication System.