TRANSMIT EMISSION CONTROL IN A WIRELESS TRANSCEIVER

• US 20090274073A1
• Filed: 05/02/2008
• Published: 11/05/2009
• Est. Priority Date: 05/02/2008
• Status: Active Grant

• Current Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Original Assignee: Nextwave Broadband Incorporated (AT&T, Inc.)
• Inventors: Sutton, Todd R.
• Granted Patent: US 8,125,974 B2
• Time in Patent Office: Days
• US Class Current: 370/280
• CPC Class Codes: H04L 5/0066 Requirements on out-of-channel emissions
• CPC Class Codes: H04W 4/20 Services signaling; Auxiliary data signalling, i.e. transmitting data via a non-traffic channel

Abstract

Methods and apparatus for control of uplink resource allocation and undesirable transmit emissions from a wireless transceiver in a frequency division duplex (FDD) or hybrid frequency division duplex (H-FDD) wireless system. The bandwidths spanned by the receive band and the transmit band may be symmetric or asymmetric. Additionally, each of the receive band or the transmit band may be contiguous or may be an aggregate of multiple discontinuous frequency bands. The wireless transceiver can control undesirable transmit emissions from occurring in a predetermined frequency band by using an offset LO frequency and restricting transmit signals to frequencies away from the predetermined frequency band. Alternatively, in an asymmetric FDD system where a receive band is larger than a transmit band, the transceiver can limit transmit signal allocation to the transmit band. The transceiver can further limit out of band transmit emissions using an offset LO frequency.

Claims

1. A method of transmit emission control in a wireless transceiver, the method comprising:

receiving wireless downlink signals in a downlink frequency band;

determining a virtual uplink resource allocation within a virtual uplink frequency band that is distinct from the downlink frequency band and that has a substantially identical bandwidth as the downlink frequency band;

remapping the virtual uplink resource allocation to an uplink resource allocation in an uplink frequency band that is narrower than the virtual uplink frequency band; and

transmitting an uplink signal on the uplink resource allocation.

2. The method of claim 1, wherein receiving the wireless downlink signals comprises receiving downlink signals in a first time period exclusive of a second time period for transmitting the uplink signal.

3. The method of claim 1, wherein receiving the wireless downlink signals comprises receiving an uplink control message having the virtual uplink channel allocation.

4. The method of claim 1, further comprising filtering the uplink signal based on a bandwidth of the uplink resource allocation.

5. The method of claim 3, wherein the virtual uplink resource allocation is restricted to a portion of the virtual uplink frequency band corresponding to the uplink frequency band.

6. The method of claim 1, wherein a number and a spacing of subcarriers in the downlink frequency band coincide with a number and a spacing of subcarriers in the virtual uplink frequency band.

7. The method of claim 1, wherein remapping the virtual uplink resource allocation comprises:

configuring a Local Oscillator (LO) frequency at a frequency offset from a nominal LO frequency for the virtual uplink band; and

remapping the virtual uplink resource allocation based on the frequency offset.

8. The method of claim 1, wherein remapping the virtual uplink resource allocation comprises remapping a virtual uplink subcarrier index based in part on a difference between a number of subcarriers in the uplink frequency band and a number of subcarriers in the virtual uplink band.

9. The method of claim 1, further comprising nulling a predetermined subcarrier.

10. The method of claim 9, wherein the predetermined subcarrier comprises a DC subcarrier in the uplink frequency band.

11. The method of claim 9, wherein nulling the predetermined subcarrier comprises omitting symbols that map to a DC subcarrier in the uplink frequency band.

12. A method of transmit emission control in a wireless transceiver, the method comprising:

receiving wireless downlink signals in a downlink frequency band, wherein the downlink frequency band is distinct from an uplink frequency band;

determining an uplink resource allocation based on a control message received in the downlink frequency band, the uplink resource allocation restricted to a portion of the uplink frequency band;

remapping the uplink resource allocation based on a frequency offset that is based in part on a difference between the uplink frequency band and the portion of the uplink frequency band to which the uplink resource allocation is restricted; and

transmitting an uplink signal over the uplink resource allocation.

13. The method of claim 12, wherein receiving wireless downlink signals comprises receiving the downlink signals in a receive time period that is distinct from a transmit time period.

14. The method of claim 12, further comprising filtering the uplink signal based in part on a bandwidth of the portion of the uplink frequency band to which the uplink resource allocation is restricted.

15. The method of claim 12, wherein remapping the uplink resource allocation based on the frequency offset comprises remapping the uplink bandwidth allocation based on a frequency offset that positions a center frequency of the uplink frequency band away from a constrained emissions band.

16. A method of transmit emission control in a wireless transceiver, the method comprising:

receiving wireless downlink signals in a downlink frequency band having a first set of subcarriers;

determining an uplink resource allocation within an uplink frequency band that is distinct from the downlink frequency band, wherein the uplink frequency band has a second set of subcarriers distinct from the first set of subcarriers, and wherein the uplink frequency band has a second bandwidth distinct from a first bandwidth of the downlink frequency band; and

transmitting an uplink signal in the uplink resource allocation.

17. The method of claim 16, wherein receiving the wireless downlink signals comprises receiving downlink Orthogonal Frequency Division Multiplex (OFDM) symbols over the first set of subcarriers.

18. The method of claim 16, wherein receiving the wireless downlink signals comprises receiving the wireless downlink signals in a downlink time period exclusive of an uplink time period.

19. The method of claim 16, wherein determining the uplink resource allocation comprises determining a subcarrier allocation in at least one uplink Orthogonal Frequency Division Multiplex (OFDM) symbol, the at least one uplink OFDM symbol having a distinct number of subcarriers from a downlink OFDM symbol.

20. The method of claim 16, wherein transmitting the uplink signal comprises transmitting an Orthogonal Frequency Division Multiplex (OFDM) symbol occupying an uplink bandwidth distinct from a downlink bandwidth.

21. A method of transmit emission control in a wireless transceiver, the method comprising:

receiving a downlink Orthogonal Frequency Division Multiplex (OFDM) symbol in a downlink frequency band; and

determining an uplink allocation in an uplink OFDM symbol of an uplink frequency band wherein the uplink frequency band is distinct from the downlink frequency band and wherein the uplink OFDM symbol includes a number of uplink subcarriers distinct from a number of downlink subcarriers in the downlink OFDM symbol.

22. The method of claim 21, further comprising:

remapping the uplink allocation to a remapped allocation in a reduced uplink frequency band that is narrower than the uplink frequency band;

generating the uplink OFDM symbol based on the remapped allocation; and

transmitting the uplink OFDM symbol.

23. A wireless apparatus with transmit emission control, the apparatus comprising:

a receiver configured to receive wireless downlink signals in a downlink frequency band, the wireless signals including a virtual uplink resource allocation;

a channel index remapper coupled to the receiver and configured to remap the virtual uplink resource allocation to an uplink resource allocation;

a signal mapper configured to map uplink information to a plurality of uplink subcarriers based on the uplink resource allocation; and

a transmitter configured to transmit the plurality of uplink subcarriers in an uplink frequency band distinct from the downlink frequency band.

24. The apparatus of claim 23, further comprising a filter configured to filter a signal mapper output based on a bandwidth of the uplink resource allocation, and couple a filtered uplink signal to the transmitter.

25. The apparatus of claim 24, wherein the filter comprises a programmable digital filter.

26. The apparatus of claim 24, wherein the filter comprises an analog variable filter.

27. The apparatus of claim 24, further comprising a bandwidth controller configured to vary a bandwidth of the filter based on the uplink resource allocation.

28. The apparatus of claim 23, wherein the receiver is configured to receive the wireless downlink signals during a downlink subframe that is time division duplexed with an uplink subframe during which the transmitter transmits the plurality of uplink subcarriers.

29. The apparatus of claim 23, wherein the receiver is configured to receive the wireless downlink signals in a plurality of OFDM symbols having a downlink subcarrier spacing that is substantially the same as an uplink subcarrier spacing.

30. The apparatus of claim 29, wherein a number of downlink subcarriers is the same as a number of subcarriers in a virtual uplink bandwidth.

31. The apparatus of claim 29, wherein a number of downlink subcarriers is the greater than a number of subcarriers in the uplink frequency band.

32. The apparatus of claim 24, further comprising a local oscillator (LO) and wherein the channel index remapper is configured to program a LO frequency at a frequency offset from a nominal LO frequency for a virtual uplink band, and remapping the virtual uplink resource allocation based on the frequency offset.

33. A wireless apparatus with transmit emission control, the apparatus comprising:

a receiver configured to receive in a downlink frequency band a plurality of downlink Orthogonal Frequency Division Multiplex (OFDM) symbols including a virtual uplink resource allocation; and

a transmitter configured to transmit a plurality of uplink OFDM symbols based on the virtual uplink resource allocation and in an uplink frequency band distinct from the downlink frequency band, wherein the uplink frequency band has a second bandwidth distinct from a first bandwidth of the downlink frequency band.

34. The apparatus of claim 33, wherein the second bandwidth is narrower than the first bandwidth.

35. The apparatus of claim 33, wherein a downlink subcarrier spacing is substantially identical to a virtual uplink subcarrier spacing.

36. The apparatus of claim 33, wherein the receiver receives the OFDM symbols in a downlink subframe that is time division duplexed with an uplink subframe during which the transmitter is configured to transmit.

37. The apparatus of claim 33, further comprising a channel index remapper coupled to the receiver and configured to remap the virtual uplink resource allocation to an uplink resource allocation in the uplink frequency band.

38. The apparatus of claim 37, wherein the channel index remapper remaps the virtual uplink resource allocation based in part on a difference in a number of subcarriers in a virtual uplink frequency band and a number of subcarriers in the uplink frequency band.

39. The apparatus of claim 33, further comprising:

a local oscillator (LO) common to the receiver and the transmitter; and

a LO controller configured to control a frequency of the LO based on a time division duplexed transmit and receive timing.

40. The apparatus of claim 39, wherein the LO controller is further configured to control a frequency of the LO based on a state of a reduced emissions mode.