Method and system for generating higher order modulations with QPSK modulator
View Patent ↗Method and system for generating higher order modulations with QPSK modulators. A complex sequence of binary digits is input to QPSK modulators. The binary digits are mapped to constellation points and multiplied with weighting coefficient. Constellation points of higher order modulation are mapped to inputs of the QPSK modulator, and, after modulation QPSK symbols are summed to compose symbols of higher order modulation.
1. Method for generating higher order modulations with QPSK modulators wherein
a complex-valued input chip sequence is split into real and imaginary parts by a splitter and input to QPSK modulators in which the sequence is mapped to constellation points, multiplied with weighting coefficients in first multipliers, outputs of the multipliers are pulse shaped and supplied to second multipliers for multiplication by cos (ωt) and −sin(ωt), respectively, and the outputs of these multipliers are summed by an adder, thereby generating a resulting signal of the QPSK modulators,
the resulting signal is spread by multiplying it with spreading code,
constellation points of higher order modulation are mapped to inputs of the QPSK modulator, and,
after modulation and spreading, QPSK symbols are summed to compose symbols of higher order modulation.
2. Method according to claim 1 wherein different mapping tables are generated for different modulation schemes.
3. Method according to claim 1 , wherein symbols of higher order modulations are generated by summing up a number of weighted QPSK symbols.
4. Method according to claim 1 , wherein constellation points of higher order modulation are mapped to inputs 0 , 1 or DTX(=Discontinuous Transmission mode) of weighted QPSK modulators.
5. Method according to claim 1 , wherein 8PSK symbol is obtained by summing the outputs of two spreaders/modulators having different weighting coefficients.
6. Method according to claim 1 , wherein 16QAM symbol is obtained by summing the outputs of two spreaders/modulators.
7. Method according to claim 1 , wherein 64QAM symbol is obtained by summing the outputs of three spreaders/modulators.
8. Method according to claim 1 , wherein High Speed Downlink Packet Access (HSDPA) is used.
9. Method according to claim 1 , wherein spreading and modulation are performed in the same operation in the transmitter.
10. System for generating higher order modulations with QPSK modulators comprising
means for splitting a complex-valued chip sequence into real and imaginary parts,
means for inputting the sequence to QPSK modulators in which the sequences is mapped to constellation points, multiplied with weighting coefficients in first means for multiplying, outputs of the first means for multiplying are pulse shaped and supplied to second means for multiplying for multiplication by cos (ωt) and −sin(ωt), respectively, and the outputs of the second means for multiplying are summed by means for adding, thereby generating a resulting signal of the QPSK modulators,
means for spreading the resulting signal,
means for mapping constellation points of higher order modulation to inputs of the QPSK modulator, and,
means for summing, after modulation and spreading, QPSK symbols to compose symbols of higher order modulation.
11. System according to claim 10 comprising different mapping tables for different modulation schemes.
12. System according to claim 10 , wherein the summing means is adapted to sum up a number of weighted QPSK symbols.
13. System according to claim 10 , wherein the mapping means is adapted to map constellation points of higher order modulation to inputs 0 , 1 or DTX(=Discontinuous Transmission mode) of weighted QPSK modulators.
14. System according to claim 10 , wherein the summing means is adapted to sum the outputs of two spreaders/modulators for generating 8PSK or 16QAM symbols.
15. System according to claim 10 , wherein the summing means is adapted to sum the outputs of three spreaders/modulators for generating 64QAM symbols.