Wireless transceiver with reduced transmit emissions

• US 9,178,539 B2
• Filed: 09/14/2012
• Issued: 11/03/2015
• Est. Priority Date: 01/19/2007
• Status: Expired due to Fees

• Current Assignee: Monument Bank of Intellectual Property, LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Inventors: Sutton, Todd, Gummadi, Srikanth, Hosseini, Walid, Wang, Lei
• Primary Examiner(s): Sorowar, Golam
• Application Number:
  US13/618,102
• Publication Number:
  US 20130065623A1
• Time in Patent Office: 1,145 Days
• Field of Search: 455/76, 455/403, 455/452.2, 455/450, 455/452.1, 455/522, 455/423, 455/424, 455/67.11, 370/208, 370/468, 370/352, 370/328, 370/493
• US Class Current: 1/1
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/003 Arrangements for allocating sub-channels of the transmission path
• CPC Class Codes: H04L 5/0066 Requirements on out-of-channel emissions

Abstract

Methods and apparatus for reducing transmit emissions are described herein. The transmit out of band emissions in an adjacent band can be reduced while complying with existing wireless communication standards through utilization of one or more of reduced transmit bandwidth, transmit operating band offset, and channel index remapping. The transceiver can support a receive operating band substantially adjacent to a band edge. The transmit operating band can be offset from an adjacent frequency band, and can use a narrower operating band than is supported by the receiver. The transmit baseband signal can have a reduced bandwidth to reduce the amount of noise. The frequency offset can introduce a larger transition band between the transmit operating band edges and the adjacent frequency band of interest. The transceiver can remap channel assignments to compensate for the frequency offset such that the frequency offset introduced in the transmitter is transparent to channel allocation.

Claims

1. A method of reducing out-of-band emissions in an adjacent cell of a cellular communications system, performed by a subscriber station, the method comprising:

transmitting a resource allocation request;

receiving a resource allocation message based at least in part on the resource allocation request, the resource allocation message including an indication of a newly allocated radio frequency (RF) band that is a subset of an RF band otherwise fully available to the subscriber station for uplink transmissions, the newly allocated RF band being dynamically selected to be biased away from at least one band of interest associated with the adjacent cell to reduce out-of-band emissions in the adjacent cell;

generating a transmit signal; and

filtering the transmit signal to a signal band that is based on the newly allocated RF band.

2. The method of claim 1, further comprising the subscriber station offsetting a frequency of a Local Oscillator (LO) of the subscriber station from a first LO frequency to a second LO frequency.

3. The method of claim 2, wherein a magnitude of a difference between the first LO frequency and the second LO frequency is fixed.

4. The method of claim 2, wherein a magnitude of a difference between the first LO frequency and the second LO frequency is determined based on a width of the newly allocated RF band.

5. The method of claim 2, wherein the second LO frequency is further from a band edge of a band of interest of the at least one band of interest than the first LO frequency.

6. The method of claim 2, wherein the first LO frequency comprises a receive LO frequency.

7. The method of claim 2, further comprising remapping at least a portion of the newly allocated RF band to compensate for offsetting the frequency of the LO.

8. The method of claim 7, wherein the remapping comprises remapping at least one subcarrier index assigned in the newly allocated RF band to compensate for offsetting the frequency of the LO.

9. The method of claim 7, further comprising nulling a subcarrier based in part on offsetting the frequency of the LO.

10. The method of claim 9, wherein the subcarrier comprises a direct current (DC) subcarrier.

11. The method of claim 1, wherein receiving the indication of the newly allocated RF band comprises receiving an Adaptive Modulation and Coding resource allocation restricted to a predetermined number of bins in the RF band otherwise fully available to the subscriber station for uplink transmissions.

12. The method of claim 1, wherein receiving the indication of the newly allocated RF band comprises receiving at least one index value identifying a subcarrier allocated in an uplink Orthogonal Frequency Division Multiplex (OFDM) symbol.

13. The method of claim 1, wherein generating the transmit signal comprises generating an Orthogonal Frequency Division Multiplex (OFDM) symbol based at least in part on the indication of the newly allocated RF band.

14. The method of claim 1, further comprising nulling a subcarrier in the signal band.

15. The method of claim 1, wherein the resource allocation message is received in an uplink-MAP (UL-MAP) message.

16. The method of claim 1, further comprising:

transmitting a power metric prior to receiving the resource allocation message, wherein the newly allocated RF band is based at least in part on the power metric.

17. A subscriber station configured to reduce out-of-band emissions in an adjacent cell of a cellular communications system, the subscriber station comprising:

a transmitter configured to transmit a resource allocation request;

a receiver configured to receive a resource allocation message based at least in part on the resource allocation request, the resource allocation message including an indication of a newly allocated radio frequency (RF) band that is a subset of an RF band otherwise fully available to the subscriber station for uplink transmissions, the newly allocated RF band being dynamically selected to be biased away from at least one band of interest associated with the adjacent cell to reduce out-of-band emissions in the adjacent cell;

the transmitter configured to generate a transmit signal; and

a variable filter configured to filter the transmit signal to a signal band that is based on the newly allocated RF band.

18. The subscriber station of claim 17, further comprising:

a controller configured to offset a frequency of a Local Oscillator (LO) of the subscriber station from a first LO frequency to a second LO frequency.

19. The subscriber station of claim 18, wherein a magnitude of a difference between the first LO frequency and the second LO frequency is fixed.

20. The subscriber station of claim 18, wherein a magnitude of a difference between the first LO frequency and the second LO frequency is determined based on a width of the newly allocated RF band.

21. The subscriber station of claim 18, wherein the second LO frequency is further from a band edge of a band of interest of the at least one band of interest than the first LO frequency.

22. The subscriber station of claim 18, wherein the first LO frequency comprises a receive LO frequency.

23. The subscriber station of claim 18, further comprising:

a signal mapper configured to remap at least a portion of the newly allocated RF band to compensate for offsetting the frequency of the LO.

24. The subscriber station of claim 23, wherein the signal mapper is configured to remap at least a portion of the newly allocated RF band by remapping at least one subcarrier index assigned in the newly allocated RF band to compensate for offsetting the frequency of the LO.

25. The subscriber station of claim 23, wherein the signal mapper is further configured to null a subcarrier based in part on offsetting the frequency of the LO.

26. The subscriber station of claim 25, wherein the subcarrier comprises a direct current (DC) subcarrier.

27. The subscriber station of claim 17, wherein the receiver is configured to receive the resource allocation message including the indication of the newly allocated RF band by receiving an Adaptive Modulation and Coding resource allocation restricted to a predetermined number of bins in the RF band otherwise fully available to the subscriber station for uplink transmissions.

28. The subscriber station of claim 17, wherein the receiver is configured to receive the resource allocation message including the indication of the newly allocated RF band by receiving at least one index value identifying a subcarrier allocated in an uplink Orthogonal Frequency Division Multiplex (OFDM) symbol.

29. The subscriber station of claim 17, wherein the transmitter is configured to generate the transmit signal by generating an Orthogonal Frequency Division Multiplex (OFDM) symbol based at least in part on the indication of the newly allocated RF band.

30. The subscriber station of claim 17, further comprising:

a signal mapper configured to null a subcarrier in the signal band.

31. The subscriber station of claim 17, wherein the receiver is configured to receive the resource allocation message in an uplink-MAP (UL-MAP) message.

32. The subscriber station of claim 17, wherein the transmitter is further configured to transmit a power metric prior to the receiver receiving the resource allocation message, wherein the newly allocated RF band is based at least in part on the power metric.