Adaptative multi-carrier code division multiple access

1. A system comprising:

a serial to parallel converter configured to

receive a bit stream and a number of CDMA sequences, the number of CDMA sequences being equal or greater than a number of a plurality of carriers, and

divide the bit stream over the number of CDMA sequences to produce the same number of virtual carrier signals;

a modulator configured to modulate each virtual carrier signal of the number of virtual carrier signals to produce the same number of modulated virtual carrier signals;

a PN generator configured to generate PN sequences; and

a summarizer configured to receive an input that specifies a number o f CDMA sequences per carrier and a length of each CDMA sequence per carrier, to add modified virtual carrier signals for each carrier of the plurality of carriers, each modified virtual carrier signal being the product of one of the virtual carrier signals and a PN sequence.

2. The system of claim 1 wherein the modulator modulates each virtual carrier signal according to an input for that virtual carrier signal.

3. The system of claim 1 further comprising a bit loading memory, wherein

the serial to parallel converter is configured to receive the number of CDMA sequences from the bit loading memory, and

the modulator is configured to receive an input for each virtual carrier signal from the bit loading memory for modulating that virtual carrier signal.

4. The system of claim 1 wherein the input for each virtual carrier signal specifies a number of bits per symbol or a constellation size of the modulation.

5. The system of claim 1 further comprising an IFFT configured to

receive from the summarizer, for each carrier of the plurality of carriers, the sum of the modified virtual carrier signals for that carrier, and

perform an inverse fast Fourier transform function on each sum.

6. The system of claim 1 wherein the input further specifies a chip length of each CDMA sequence per carrier.

7. The system of claim 1 , further comprising circuitry configured to transmit the plurality of carriers on a wired media.

8. The system of claim 1 , further comprising circuitry configured to wirelessly transmit the plurality of carriers.

9. A method performed by a first node in a communication system, the method comprising:

receiving a channel performance metric for each carrier of a number of carriers from a second node in the communication system;

determining a number of CDMA sequences over each carrier based on the channel performance metric for each carrier;

determining a number of virtual carrier signals by summing the number of CDMA sequences over the number of carriers;

dividing a bit stream into a number of virtual carrier signals;

modulating each of the virtual carrier signals;

combining the modulated virtual carrier signals to produce an XN(u) signal for each carrier of a number of carriers, the number of carriers being less or equal than the number of virtual carrier signals; and

performing an inverse fast Fourier transform function on the XN(u) signals to produce a digital signal.

10. The method of claim 9 further comprising determining a number of bits per symbol or a constellation size of the modulation for each of the CDMA sequences, wherein modulating each of the virtual carrier signals employs the determined number of bits or constellation size.

11. The method of claim 9 further comprising determining a length of each CDMA sequence per carrier based on the channel performance metric for that carrier.

12. The method of claim 9 further comprising determining a chip length of each CDMA sequence per carrier based on the channel performance metric for that carrier.

13. The method of claim 9 , further comprising:

converting the digital signal into an analog signal; and

transmitting the analog signal on a wired media.

14. The method of claim 9 , further comprising:

converting the digital signal into a Radio Frequency analog signal; and

wirelessly transmitting the Radio Frequency analog signal.

15. A system comprising:

a serial to parallel converter configured to

receive a bit stream and a number of CDMA sequences, the number of CDMA sequences being equal or greater than a number of a plurality of carriers, and

divide the bit stream over the number of CDMA sequences to produce the same number of virtual carrier signals;

a modulator configured to modulate each virtual carrier signal of the number of virtual carrier signals to produce the same number of modulated virtual carrier signals;

a PN generator configured to generate PN sequences;

a summarizer configured to receive an input that specifies a number o f CDMA sequences per carrier and a length of each CDMA sequence per carrier, to add modified virtual carrier signals for each carrier of the plurality of carriers, each modified virtual carrier signal being the product of one of the virtual carrier signals and a PN sequence;

an IFFT configured to receive from the summarizer, for each carrier of the plurality of carriers, the sum of the modified virtual carrier signals for that carrier, and perform an inverse fast Fourier transform function on each sum to produce an IFFT output;

Digital to Analog conversion circuitry operable to convert the IFFT output to a transmit signal.

16. The system of claim 15 wherein the modulator modulates each virtual carrier signal according to an input for that virtual carrier signal.

17. The system of claim 15 further comprising a bit loading memory, wherein

the serial to parallel converter is configured to receive the number of CDMA sequences from the bit loading memory, and

the modulator is configured to receive an input for each virtual carrier signal from the bit loading memory for modulating that virtual carrier signal.

18. The system of claim 15 wherein the input for each virtual carrier signal specifies a number of bits per symbol or a constellation size of the modulation.

19. The system of claim 15 further comprising an IFFT configured to

receive from the summarizer, for each carrier of the plurality of carriers, the sum of the modified virtual carrier signals for that carrier, and

perform an inverse fast Fourier transform function on each sum.

20. The system of claim 15 wherein the input further specifies a chip length of each CDMA sequence per carrier.