Multi-band OFDM UWB communication systems having improved frequency diversity

1. A method for transmitting symbols in a communication system having a plurality of frequency bands, each frequency band including a plurality of tones, the method comprising the steps of:

transmitting a first symbol on a first tone using a first constellation mapping and a second symbol on a second tone using a second constellation mapping different from the first constellation mapping the second tone different from the first tone, the first and second symbols selected from among the symbols, the first and second tones selected from among the plurality of tones; and

retransmitting the first symbol on the second tone using the second constellation mapping and the second symbol on the first tone using the first constellation mapping.

2. The method according to claim 1 , wherein a predetermined tone separation is provided between the first and second tones, the predetermined tone separation being constant over the plurality of tones.

3. The method according to claim 1 , the step of retransmitting further including the steps of retransmitting a negative complex conjugate of the second symbol and retransmitting a complex conjugate of the first symbol.

4. The method according to claim 1 , further including a step of determining a data rate of the communication system,

wherein when the data rate is greater than a first data rate, the steps of transmitting and retransmitting include using the first and second constellation mappings where each of the first and second constellation mappings are N-QAM constellations, where N is a power of two and greater than or equal to two, and

when the data rate is less than a second data rate, the second data rate being less than the first data rate, the steps of transmitting and retransmitting include reducing a size of the first and second symbols and using the first and second constellation mappings where each of the constellation mappings are M-QAM constellations, where M is less than N.

5. A computer-readable medium encoded with a computer program which when executed causes a computer to perform the method according to claim 1 .

6. A method for detecting symbols in a communication system having a plurality of frequency bands, each frequency band including a plurality of tones, the method comprising the steps of:

demapping a first set of signals corresponding to first and second symbols mapped using respective first and second constellation mappings, the second constellation mapping different from the first constellation mapping, the first and second symbols selected from among the symbols;

demapping a second set of signals corresponding to the first and second symbols mapped using the respective second and first constellation mappings;

combining the first and second sets of demapped signals to form a combined signal; and

detecting the first and second symbols from the combined signal.

7. The method according to claim 6 , the step of detecting the first and second symbols further comprising the step of determining a decision statistic from the combined signal and applying a predetermined threshold to the decision statistic to detect the first and second symbols.

8. A computer-readable medium encoded with a computer program which when executed causes a computer to perform the method according to claim 6 .

9. A data transmission apparatus, the data transmission apparatus including a transmitter for transmitting symbols in a plurality of frequency bands, each frequency band including a plurality of tones, the data transmission apparatus comprising:

a constellation mapper for 1) mapping first and second symbols using respective first and second constellation mappings to modulate respective first and second tones for transmitting the first and second symbols by the transmitter, the second constellation mapping different from the first constellation mapping the second tone different from the first tone, and 2) mapping the first and second symbols using the respective second and first constellation mappings to modulate the corresponding second and first tones for retransmitting the first and second symbols by the transmitter, the first and second symbols selected from among the symbols, the first and second tones selected from among the plurality of tones.

10. Apparatus according to claim 9 , wherein the first and second tones include a frequency separation of 256 MHz.

11. Apparatus according to claim 9 , wherein a predetermined tone separation is provided between the first and second tones, the predetermined tone separation being constant over the plurality of tones.

12. Apparatus according to claim 11 , wherein the predetermined tone separation is 50 tones.

13. Apparatus according to claim 11 , wherein the predetermined tone separation is 64 tones.

14. A data reception apparatus, the data reception apparatus including a receiver for receiving a first set of signals and a second set of signals in a communication system having a plurality of frequency bands, each frequency band including a plurality of tones, the data reception apparatus comprising:

a demodulator including:

a demapper for demapping the first and second sets of signals received by the receiver to form first and second demapped signals, the first set of signals corresponding to first and second symbols mapped using respective first and second constellation mappings, the second constellation mapping different from the first constellation mapping, the second set of symbols corresponding to the first and second symbols mapped using the respective second and first constellation mappings, the first and second symbols selected from among the symbols;

a combiner for combining the first and second demapped signals to form a combined signal; and

a detector for detecting the first and second symbols from the combined signal.

15. A system, the system including a transmitter for transmitting a first set of signals and a second set of signals in a plurality of frequency bands and a receiver for receiving the first set of signals and the second set of signals transmitted by the transmitter, the system comprising:

a data transmission device comprising:

a constellation mapper for 1) mapping the first and second symbols using respective first and second constellation mappings to modulate corresponding first and second tones for transmitting the first and second symbols by the transmitter as the first set of signals, the second constellation mapping different from the first constellation mapping the second tone different from the first tone, and 2) mapping the first and second symbols using the respective second and first constellation mappings to modulate the respective second and first tones for retransmitting the first and second symbols by the transmitter as the second set of symbols, the first and second symbols selected from among the symbols, the first and second tones selected from among the plurality of tones; and

a data reception device comprising:

a demodulator including:

a demapper for demapping the first and second sets of signals received by the receiver to form first and second demapped signals,

a combiner for combining the first and second demapped signals to form a combined signal; and

a detector for detecting the first and second symbols from the combined signal.