Systems, methods and transceivers for wireless communications over discontiguous spectrum segments

• US 7,974,176 B2
• Filed: 02/27/2007
• Issued: 07/05/2011
• Est. Priority Date: 02/28/2006
• Status: Active Grant

• Current Assignee: ATC Technology Corporation (FedEx Corporation)
• Original Assignee: ATC Technology Corporation (FedEx Corporation)
• Inventors: Zheng, Dunmin
• Primary Examiner(s): Moe; Aung S
• Assistant Examiner(s): Louis; Vinncelas
• Application Number:
  US11/679,598
• Publication Number:
  US 20070202816A1
• Time in Patent Office: 1,589 Days
• Field of Search: 370203-210, 370/344, 455/571, 455/12.1, 375/299, 375/260, 375/295
• US Class Current: 370/203
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

Methods of transmitting a plurality of communications signals over a plurality of discontiguous bandwidth segments in a frequency band include defining a plurality (N_FFT) of orthogonal subcarriers across the frequency band, defining a plurality (N) of available physical subcarriers from among the orthogonal subcarriers. The available physical subcarriers are distributed among the plurality of discontiguous bandwidth segments. The methods further include multiplexing the plurality of communications signals onto the plurality of available physical subcarriers. Multiplexing the plurality of communications signals onto the plurality of available physical subcarriers may include assigning the communications signals to respective ones of a plurality (N) of logical subcarriers, and mapping the plurality of logical subcarriers to corresponding ones of the plurality of available physical subcarriers. Related transmitters, receivers and communications systems are also disclosed.

Claims

1. A method of transmitting a plurality of communications signals over a plurality of discontiguous bandwidth segments in a frequency band, comprising:

defining a plurality (N_FFT) of orthogonal subcarriers across the frequency band;

defining a plurality (N) of available physical subcarriers from among the orthogonal subcarriers, wherein N<

N_FFT, and wherein the available physical subcarriers are distributed among the plurality of discontiguous bandwidth segments; and

multiplexing the plurality of communications signals onto the plurality of available physical subcarriers;

wherein multiplexing the plurality of communications signals onto the plurality of available physical subcarriers comprises;

assigning the communications signals to respective ones of a plurality (N) of logical subcarriers;

mapping the plurality of logical subcarriers to corresponding ones of the plurality of available physical subcarriers;

assigning at least one pilot signal to at least one of the plurality of logical subcarriers; and

modulating each of the available physical subcarriers with data from a corresponding logical subcarrier, the method further comprising;

defining a plurality (N_FFT-N) of unavailable physical subcarriers within the frequency band; and

setting an input data signal corresponding to each of the plurality of unavailable physical subcarriers to zero;

wherein the communications signals and the at least one pilot signal comprise N information signals corresponding to the available physical subcarriers; and

wherein modulating each of the available physical subcarriers with data from a corresponding logical subcarrier comprises performing an N_FFT-point inverse fourier transform of the N information signals corresponding to the available physical subcarriers and the N_FFT-N input data signals corresponding to each of the plurality of unavailable physical subcarriers.

2. The method of claim 1, further comprising

converting an output of the N_FFT-point inverse fourier transform to a serial data stream;

and

transmitting the serial data stream.

3. The method of claim 1, further comprising:

defining a plurality of clusters in the discontiguous bandwidth segments, each of the clusters comprising a plurality of contiguous subcarriers;

defining an adaptive modulation and coding (AMC) subchannel comprising a plurality of contiguous clusters extending over a plurality of contiguous symbols;

allocating a first plurality of subcarriers within the AMC subchannel as pilot subcarriers, such that the pilot subcarriers are distributed uniformly across the AMC subchannel; and

allocating a second plurality of subcarriers within the AMC subchannel as data subcarriers.

4. The method of claim 3, wherein defining the AMC subchannel comprises defining a subchannel comprising two clusters over three symbols.

5. The method of claim 3, wherein defining the AMC subchannel comprises defining a subchannel comprising one cluster over six symbols.

6. The method of claim 3, wherein the pilot subcarriers for an AMC subchannel are allocated at locations determined by the indices of logical subcarriers.

7. The method of claim 6, wherein pilot subcarriers in an AMC channel are offset by two subcarriers in adjacent symbols.

8. The method of claim 6, wherein the pilot subcarriers for an AMC channel including nine subcarriers per cluster are determined according to the equation:

9. The method of claim 3, further comprising:

assigning a plurality of data symbols to data subcarriers in the AMC subchannel according to a scrambling sequence.

10. The method of claim 9, wherein the scrambling sequence is defined by a Galois field and an offset.

11. The method of claim 9, wherein the scrambling sequence is unique to a particular cell and/or sector of a wireless communications system.

12. A method of transmitting a plurality of communications signals over a plurality of discontiguous bandwidth segments in a frequency band, comprising:

defining a plurality (N_FFT) of orthogonal subcarriers across the frequency band;

defining a plurality (N) of available physical subcarriers from among the orthogonal subcarriers, wherein N<

N_FFT, and wherein the available physical subcarriers are distributed among the plurality of discontiguous bandwidth segments; and

multiplexing the plurality of communications signals onto the plurality of available physical subcarriers;

wherein multiplexing the plurality of communications signals onto the plurality of available physical subcarriers comprises;

spreading the plurality of communications signals using a plurality of corresponding spreading codes;

combining the plurality of spread communications signals to form a combined communications signal;

converting the combined communications signal to parallel communications signals

assigning the parallel communications signals to respective ones of a plurality (N) of logical subcarriers;

mapping the plurality of logical subcarriers to corresponding ones of the plurality of available physical subcarriers;

assigning at least one pilot signal to at least one of the plurality of logical subcarriers; and

modulating each of the available physical subcarriers with data from a corresponding logical subcarrier, the method further comprising;

defining a plurality (N_FFT-N) of unavailable physical subcarriers within the frequency band; and

setting an input data signal corresponding to each of the plurality of unavailable physical subcarriers to zero;

wherein the parallel communications signals and the at least one pilot signal comprise N information signals corresponding to the available physical subcarriers; and

wherein modulating each of the available physical subcarriers with data from a corresponding logical subcarrier comprises performing an N_FFT-point inverse fourier transform of the N information signals corresponding to the available physical subcarriers and the N_FFT-N input data signals corresponding to each of the plurality of unavailable physical subcarriers.

13. The method of claim 12, further comprising

converting an output of the N_FFT-point inverse fourier transform to a serial data stream;

and

transmitting the serial data stream.

14. The method of claim 12, further comprising:

defining a plurality of clusters in the discontiguous bandwidth segments, each of the clusters comprising a plurality contiguous subcarriers;

defining an adaptive modulation and coding (AMC) subchannel comprising a plurality of contiguous clusters extending over a plurality of contiguous symbols; and

allocating a plurality of subcarriers within the AMC subchannel as pilot subcarriers, such that the pilot subcarriers are distributed uniformly across the AMC subchannel.

15. The method of claim 14, wherein the pilot subcarriers for an AMC subchannel are allocated at locations determined by the indices of logical subcarriers.

16. The method of claim 15, wherein pilot subcarriers in adjacent symbols of an AMC channel are offset by two subcarriers.

17. The method of claim 15, wherein the pilot subcarriers for an AMC channel including nine subcarriers per cluster are determined according to the equation: