INCREASED CAPACITY COMMUNICATIONS SYSTEMS, METHODS AND/OR DEVICES

• US 20100002789A1
• Filed: 06/09/2009
• Published: 01/07/2010
• Est. Priority Date: 07/07/2008
• Status: Active Grant

• Current Assignee: Odyssey Wireless, Inc.
• Original Assignee: Odyssey Wireless, Inc.
• Inventors: Karabinis, Peter D.
• Granted Patent: US 8,462,860 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

Communications architectures, systems, devices and/or methods are disclosed that can increase capacity of conventional OFDM/OFDMA systems, devices, methods and/or protocols by as much as 100%. Conventional OFDM/OFDMA transmitter/receiver architectures, methods, systems and/or devices are improved upon via additional signal processing to provide the increased capacity and reduce non-linear distortion effects on higher-order modulation alphabets such as, for example, 256-QAM.

Claims

1. A method comprising:

receiving a signal comprising N first sub-carriers;

wherein N≧

2;

generating 2N′

samples of the signal;

wherein N′

≧

N;

performing a first transformation on a first sub-set of the 2N′

samples;

performing a second transformation on a second sub-set of the 2N′

samples; and

combining an element of the first transformation with an element of the second transformation.

2. A method according to claim 1, wherein the N first sub-carriers are orthogonal therebetween.

3. A method according to claim 1, wherein the signal further comprises M second sub-carriers;

M≧

0;

wherein the M second sub-carriers are superimposed on the N first sub-carriers over a frequency interval of bandwidth B Hz that is substantially occupied by the N first sub-carriers and over a time interval of T seconds in duration over which the N first sub-carriers are defined.

4. A method according to claim 3, wherein the M second sub-carriers are orthogonal therebetween and wherein at least one of the M second sub-carriers is not orthogonal to at least one of the N first sub-carriers.

5. A method according to claim 1, wherein the 2N′

samples comprise 2N′

time-domain samples.

6. A method according to claim 5, wherein at least one of the 2N′

time-domain samples comprises a complex value.

7. A method according to claim 1, wherein the signal comprises a bandwidth of B Hz, wherein B≧

N/T and wherein T denotes a signaling interval over which the N first sub-carriers are defined.

8. A method according to claim 7, wherein receiving a signal comprises receiving a passband signal wherein B is centered at a frequency f₁ and wherein the passband signal is frequency shifted to a frequency f₂ prior to the generating 2N′

samples of the signal.

9. A method according to claim 8, wherein f₂=B/2, f₂=0, f₂<

f₁ or f₂≧

f₁.

10. A method according to claim 3, wherein a spacing between two adjacent sub-carriers of the N first sub-carriers is 1/T Hz, a spacing between two adjacent sub-carriers of the M second sub-carriers is 1/T Hz and a spacing between a first sub-carrier of the N first sub-carriers and a sub-carrier of the M second sub-carriers that is adjacent to the first sub-carrier of the N first sub-carriers is ½

T Hz.

11. A method according to claim 3, wherein the first sub-set of the 2N′

samples comprises a first set of N″

samples and the second sub-set of the 2N′

samples comprises a second set of N′

″

samples;

wherein N″

≦

2N′ and

N′

″

≦

2N′

.

12. A method according to claim 11, wherein N″

=N′

″

=N′

, a spacing between two adjacent samples of the first set of N″

samples is T/N′

seconds, a spacing between two adjacent samples of the second set of N′

″

samples is T/N′

seconds and a spacing between a first sample of the first set of N″

samples and a sample of the second set of N′

″

samples that is adjacent to the first sample of the first set of N″

samples is T/2N′

seconds.

13. A method according to claim 1, wherein the first transformation and the second transformation each comprises a time-domain to frequency-domain transformation.

14. A method according to claim 13, wherein the time-domain is a discrete time-domain, the frequency-domain is a discrete frequency-domain and wherein the time-domain to frequency-domain transformation comprises a Discrete Fourier Transform and/or a Fast Fourier Transform.

15. A method according to claim 1, further comprising modifying the element of the first transformation and/or modifying the element of the second transformation prior to the combining.

16. A method according to claim 15, wherein combining comprises:

forming γ

^Tb+δ

^Tr;

wherein b comprises the element of the first transformation, r comprises the element of the second transformation, γ

^Tb comprises modifying the element of the first transformation, δ

^Tr comprises modifying the element of the second transformation and wherein the superscript T denotes transpose and/or conjugate transpose.

17. A method according to claim 16, further comprising:

calculating γ and

δ

such that the statistical expectation E[|γ

^Tb+δ

^Tr−

B_k|²] is minimized;

wherein E[•

] denotes statistical expectation, |•

| denotes magnitude and B_k denotes a data element that is associated with a k^th sub-carrier;

k=1, 2, . . . , N.

18. A method according to claim 17, wherein calculating comprises calculating for at least one value of k;

k=1, 2, . . . , N.

19. A method according to claim 18, further comprising:

using γ

^Tb+δ

^Tr to determine an estimate of B_k for at least one value of k.

20. A communications receiver comprising a processor that is configured to:

receive a signal comprising N first sub-carriers;

wherein N≧

2;

generate 2N′

samples of the signal;

wherein N′

≧

N;

perform a first transformation on a first sub-set of the 2N′

samples;

perform a second transformation on a second sub-set of the 2N′

samples; and

combine an element of the first transformation with an element of the second transformation.

21. A communications receiver according to claim 20, wherein the N first sub-carriers are orthogonal therebetween.

22. A communications receiver according to claim 20, wherein the signal further comprises M second sub-carriers;

M≧

0;

wherein the M second sub-carriers are superimposed on the N first sub-carriers over a frequency interval of bandwidth B Hz that is substantially occupied by the N first sub-carriers and over a time interval of T seconds in duration over which the N first sub-carriers are defined.

23. A communications receiver according to claim 22, wherein the M second sub-carriers are orthogonal therebetween and wherein at least one of the M second sub-carriers is not orthogonal to at least one of the N first sub-carriers.

24. A communications receiver according to claim 20, wherein the 2N′

samples comprise 2N′

time-domain samples.

25. A communications receiver according to claim 24, wherein at least one of the 2N′

time-domain samples comprises a complex value.

26. A communications receiver according to claim 20, wherein the signal comprises a bandwidth of B Hz, wherein B≧

N/T and wherein T denotes a signaling interval over which the N first sub-carriers are defined.

27. A communications receiver according to claim 26, wherein the signal comprises a passband signal, wherein B is centered at a frequency f₁ and wherein the passband signal is frequency shifted to a frequency f₂ before the processor generates the 2N′

samples of the signal.

28. A communications receiver according to claim 27, wherein f₂=B/2, f₂=0,f₂<

f₁ or f₂≧

f₁.

29. A communications receiver according to claim 22, wherein a spacing between two adjacent sub-carriers of the N first sub-carriers is 1/T Hz, a spacing between two adjacent sub-carriers of the M second sub-carriers is 1/T Hz and a spacing between a first sub-carrier of the N first sub-carriers and a sub-carrier of the M second sub-carriers that is adjacent to the first sub-carrier of the N first sub-carriers is ½

T Hz.

30. A communications receiver according to claim 22, wherein the first sub-set of the 2N′

samples comprises a first set of N″

samples and the second sub-set of the 2N′

samples comprises a second set of N′

″

samples;

wherein N″

≦

2N′ and

N′

″

≦

2N′

.

31. A communications receiver according to claim 30, wherein N″

=N′

″

=N′

, a spacing between two adjacent samples of the first set of N″

samples is T/N′

seconds, a spacing between two adjacent samples of the second set of N′

″

samples is T/N′

seconds and a spacing between a first sample of the first set of N″

samples and a sample of the second set of N′

″

samples that is adjacent to the first sample of the first set of N″

samples is T/2N′

seconds.

32. A communications receiver according to claim 20, wherein the first transformation and the second transformation each comprises a time-domain to frequency-domain transformation.

33. A communications receiver according to claim 32, wherein the time-domain is a discrete time-domain, the frequency-domain is a discrete frequency-domain and wherein the time-domain to frequency-domain transformation comprises a Discrete Fourier Transform and/or a Fast Fourier Transform.

34. A communications receiver according to claim 20, wherein the processor is further configured to modify the element of the first transformation and/or to modify the element of the second transformation before the processor combines the element of the first transformation with the element of the second transformation.

35. A communications receiver according to claim 34, wherein the processor is further configured to form γ

^Tb+δ

^Tr;

wherein b comprises the element of the first transformation, r comprises the element of the second transformation, γ

^Tb comprises the modified element of the first transformation, δ

^Tr comprises the modified element of the second transformation and wherein the superscript T denotes transpose and/or conjugate transpose.

36. A communications receiver according to claim 35, wherein the processor is further configured to calculate the vectors γ

and δ

such that the statistical expectation E[|γ

^Tb+bδ

^Tr−

B_k|²] is minimized;

wherein E[•

] denotes statistical expectation, |•

| denotes magnitude and B_k denotes a data element that is associated with a k^th sub-carrier;

k=1, 2, . . . , N.

37. A communications receiver according to claim 36, wherein the processor is configured to calculate the vectors γ

and δ

for at least one value of k;

k=1, 2, . . . , N.

38. A communications receiver according to claim 37, wherein the processor is further configured to use γ

^Tb+δ

^Tr to determine an estimate of B_k for at least one value of k.