Communications system, methods and apparatus

• US 7,403,470 B2
• Filed: 07/18/2005
• Issued: 07/22/2008
• Est. Priority Date: 06/13/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Lane, Frank A.
• Primary Examiner(s): Orgad; Edan
• Assistant Examiner(s): Patel; Jay P.
• Application Number:
  US11/184,051
• Publication Number:
  US 20060285481A1
• Time in Patent Office: 1,100 Days
• Field of Search: 370/203, 370/310, 370/316, 370/319, 370/344, 370/343, 370/480, 370/482, 370/328, 375/260
• US Class Current: 370/203
• CPC Class Codes: H04B 7/1853 Satellite systems for providing telephony service to a mobile station, i.e. mobile satellite service for selecting H04W
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals
• CPC Class Codes: H04L 27/261 Details of reference signals
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601

Abstract

An OFDM wireless communications system includes terrestrial and satellite based base stations. Mobile nodes support two uplink modes of operation, multi-tone mode for terrestrial station interaction and single tone mode for satellite base station interaction. In single tone mode the peak to average power ratio is lower than in the multi-tone mode allowing the same power amplifier to transmit higher average power signals and thus extend range and reach a satellite in geostationary orbit. In multi-tone mode, the mobile node: is temporarily assigned a multi-tone uplink traffic channel segment for user data, is assigned a dedicated control channel for uplink control signals, and supports slaved Ack/Nak for traffic channels. In single tone mode, the mobile node: is assigned a single logical uplink dedicated tone to use for transmitting both user data and control data, and does not use a slaved Ack/Nak mechanism for traffic channels.

Claims

1. A method of operating a wireless terminal, comprising:

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

receiving user data from the first base station during said first period of time;

transmitting acknowledgements to the first base station according to a first predetermined acknowledgement scheme; and

receiving user data from the second base station during said second period of time without acknowledging receipt of said user data.

2. The method of claim 1, further comprising:

during said second period of time, requesting retransmission of user data in response to detection of an error in the received user data.

3. A method of operating a wireless terminal, comprising:

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

during said first mode of operation, prior to transmission of said user data during said first period of time, coding at least some of said user data to be transmitted during said first period of time in a code block separate from a code block used to communicate control information during said first period of time;

during said second mode of operation, prior to transmission of said user data during said second period of time, multiplexing the user data to be transmitted during said second period of time with control data which is also to be transmitted during said second period of time; and

coding said multiplexed control and user data in a single code block.

6. The method of claim 3, wherein during said first mode of operation, said wireless terminal uses at least one tone having a fixed one to one association with a base station assigned wireless terminal identifier assigned by said first base station for transmission of control signals to said first base station.

7. The method of claim 6, further comprising:

during said first mode of operation, receiving at least one traffic channel uplink segment assignment signal from said first base station;

determining which tones are to be used as some of said multiple OFDM tones used during said first period of time from said at least one traffic channel uplink segment assignment signal; and

determining said single tone used during said second mode of operation from a wireless terminal identifier assignment, without the use of a traffic channel uplink segment assignment signal.

4. A method of operating a wireless terminal, comprising:

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio;

wherein during said second period of time the second basxe station is at least 3 times further away from the wireless terminal than the first base station is from the wireless terminal during said first period of time; and

wherein said single tone used during said second mode of operation occupies a position in a logical uplink transmission timing structure which is dedicated during said first mode of operation to a dedicated control channel used during said first period of time exclusively for control signaling.

5. A method of operating a wireless terminal, comprising:

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio;

wherein during said second period of time the second base station is at least 3 times further away from the wireless terminal than the first base station is from the wireless terminal during said first period of time; and

wherein said single tone used during said second mode of operation has a fixed one to one association with a base station assigned wireless terminal identifier; and

wherein during said first mode of operation, said tones used to transmit user data do not have a fixed one to one association with a base station assigned wireless terminal identifier.

8. A method of operating a wireless terminal, comprising:

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio;

coding user data and control data into separate coded blocks during said second period of time; and

using the same single tone used to transmit coded blocks of user data to transmit coded blocks of control data

9. The method of claim 8, wherein during said second mode of operation, said single tone is allowed to go unused and no signal is transmitted on said single tone during periods of time dedicated to the transmission of user data when there is no user data to be transmitted.

10. A method of operating a wireless terminal, comprising:

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio;

selecting one of a plurality of supported different modulation methods to be used in transmitting said at least some user data during at least a portion of said first period of time; and

using a single supported modulation method during said second period of time.

11. The method of claim 10, wherein said supported different modulation methods include QAM 4 and QAM 16 modulation and wherein said single supported modulation method is a QPSK modulation method.

12. The method of claim 11, further comprising:

selecting between a plurality of coding rates which can be used to code user data for transmission during said first period of time;

and coding data at a single coding rate for transmission during said second period of time, the single coding rate being equal to or lower than the lowest coding rate in said plurality of coding rates which can be used to code user data for transmission during said first period of time.

13. An OFDM communications method, the method comprising:

operating a wireless terminal in a first, multi-tone OFDM uplink mode of operation, in which the wireless terminal uses multiple OFDM tones at the same time to transmit signals to a first base station;

operating a wireless terminal in a second, single tone OFDM uplink mode of operation, in which the wireless terminal uses a single OFDM tone to transmit signals to a second base station, said second base station having a minimum possible physical distance from said wireless terminal which is greater than the minimum possible physical distance which can occur between said wireless terminal and said first base station, where said second base station is a satellite base station and said first base station is a terrestrial base station;

switching from the first mode of operation to the second mode of operation when a handoff occurs from said first base station to said second base station; and

wherein switching between the first and second modes of operation includes ceasing to send acknowledgements in response to received user data.

14. An OFDM communications method, the method comprising:

operating a wireless terminal in a first, multi-tone OFDM uplink mode of operation, in which the wireless terminal uses multiple OFDM tones at the same time to transmit signals to a first base station;

operating a wireless terminal in a second, single tone OFDM uplink mode of operation, in which the wireless terminal uses a single OFDM tone to transmit signals to a second base station, said second base station having a minimum possible physical distance from said wireless terminal which is greater than the minimum possible physical distance which can occur between said wireless terminal and said first base station, where said second base station is a satellite base station and said first base station is a terrestrial base station;

switching from the first mode of operation to the second mode of operation when a handoff occurs from said first base station to said second base station; and

wherein switching between the first and second modes of operation includes reducing the frequency of uplink control signals which are transmitted from the wireless terminal.

15. The OFDM communications method of claim 14, wherein switching between the first and second modes of operation includes ceasing to transmit requests for traffic channel segment assignments.

16. A communications method, comprising:

operating a wireless terminal to transmit OFDM signals to a first base station, where the distance between the wireless terminal and base station exceeds 100 miles; and

wherein a cyclic prefix transmitted with an OFDM symbol to the base station has a duration which is less than the maximum round trip propagation delay between the wireless terminal and the base station;

wherein the wireless terminal transmits to said base station using at most 1 tone at a time; and

wherein said at most one tone is a logical tone dedicated to said wireless terminal by said base station for use in uplink signaling to the exclusion of use by other wireless terminals.

17. The method of claim 16, wherein said one logical tone corresponds to a physical tone which is determined over time according to a predetermined hopping sequence.

18. A communications method, comprising:

operating a wireless terminal to transmit OFDM signals to a first base station, where the distance between the wireless terminal and base station exceeds 100 miles; and

wherein a cyclic prefix transmitted with an OFDM symbol to the base station has a duration which is less than the maximum round trip propagation delay between the wireless terminal and the base station;

operating the wireless terminal to communicate with a terrestrial base station using multiple OFDM tones simultaneously for uplink communications to the terrestrial base station; and

using the same peak power constraint used for transmitting to the first base station for transmitting to the terrestrial base station but using a higher average power for transmitting signals to the first base station than is used for transmitting signals to the terrestrial base station.

19. The method of claim 18, wherein the first base station is a satellite base station, the method further comprising:

using the same frequency band for communications to the satellite base station and the terrestrial base station but different non-overlapping carrier frequencies for the terrestrial and satellite base stations.

20. The method of claim 19, wherein said same frequency band is a 1500 MHz frequency band, the band including frequencies in the range of 1500 to 1599 MHz.

21. A wireless communications terminal comprising:

control means for controlling switching between a first multi-tone OFDM uplink mode of operation in which the wireless terminal uses multiple OFDM tones at the same time to transmit signals to a base station, and a second single tone OFDM uplink mode of operation;

means for transmitting user data using a single OFDM tone during said single tone uplink mode of operation;

means for transmitting user data using multiple OFDM tones at the same time in said multi-tone uplink mode of operation;

wherein said control means includes means for switching from multi-tone uplink mode of operation to said single tone uplink mode of operation when said wireless terminal switches from communicating with a terrestrial base station to a satellite base station; and

means for reducing the frequency of uplink control signals which are transmitted from the wireless terminal when operation switches from said multi-tone uplink mode of operation to said single tone uplink mode of operation.

22. The wireless terminal of claim 21, wherein the wireless terminal includes an omni-directional antenna coupled to said means for transmitting user data using a single OFDM tone during said single tone uplink mode of operation.

23. The wireless terminal of claim 21,

wherein said user data includes at least some voice or text data;

and

wherein the wireless terminal further includes;

means for transmitting requests for uplink traffic channel segments during said multi-tone uplink mode of operation; and

means for ceasing the transmission of uplink traffic channel segments when said mode of operation is switched from said multi-tone mode of operation to said single tone mode of operation.

24. An OFDM communications system, the system comprising:

a plurality of terrestrial base stations;

at least one satellite base station;

a wireless terminal of a first type which transmits uplink signals using a first number of OFDM tones when communicating with a terrestrial base station and transmits uplink signals using a second number of tones when communicating with a satellite base station, the second number of tones being smaller than said first number of tones; and

a plurality of wireless terminals of a second type which only support a multi-tone uplink mode of operation.

25. The OFDM communications system of claim 24, further comprising additional wireless terminals of said first type and wherein said wireless terminals of said second type are limited to being able to communicate with terrestrial base stations while wireless terminals of the first type can communicate with both terrestrial base stations and satellite base stations using OFDM signals in both the uplink and downlink.

26. A wireless terminal, comprising:

a multi-tone mode transmission control module for controlling transmission during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a first mode of operation, said transmission during said first mode of operation being controlled to use multiple OFDM tones simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

a single-tone mode transmission control module for controlling transmission during a second period of time including a second plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

a receiver module for receiving user data from the first base station during said first period of time;

a communications module for acknowledging receipt of user data, received during said first period of time from the first base station, in accordance with a first predetermined acknowledgement scheme and for allowing user data from the second base station received during said second period of time to go unacknowledged.

27. The wireless terminal of claim 26, further comprising:

a switching control module for controlling switching between said first and second modes of operation, said switching control means controlling said wireless terminal to switch to said second mode of operation for satellite communications.

28. A wireless terminal, comprising:

multi-tone mode transmission control means for controlling transmission during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a first mode of operation, said transmission during said first mode of operation being controlled to use multiple OFDM tones simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

single-tone mode transmission control means for controlling transmission during a second period of time including a second plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

receiver means for receiving user data from the first base station during said first period of time;

communications means for acknowledging receipt of user data, received during said first period of time from the first base station, in accordance with a first predetermined acknowledgement scheme and for allowing user data from the second base station received during said second period of time to go unacknowledged.

29. The wireless terminal of claim 28, further comprising:

switching control means for controlling switching between said first and second modes of operation, said switching control means controlling said wireless terminal to switch to said second mode of operation for satellite communications.

30. A computer readable medium embodying machine executable instructions for controlling a communications device to implement a method, the method comprising:

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

receiving user data from the first base station during said first period of time;

transmitting acknowledgements to the first base station according to a first predetermined acknowledgement scheme; and

receiving user data from the second base station during said second period of time without acknowledging receipt of said user data.

31. A wireless terminal, comprising:

multi-tone mode transmission control means for controlling transmission during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a first mode of operation, said transmission during said first mode of operation being controlled to use multiple OFDM tones simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

single-tone mode transmission control means for controlling transmission during a second period of time including a second plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average tower ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

coding means for coding user data and control data into separate coded blocks during said second period of time; and

transmission means for transmitting coded blocks of control data using the same single tone used to transmit coded blocks of user data.

32. A wireless terminal, comprising:

a multi-tone mode transmission control module for controlling transmission during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a first mode of operation, said transmission during said first mode of operation being controlled to use multiple OFDM tones simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

a single-tone mode transmission control module for controlling transmission during a second period of time including a second plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

a coding module for coding user data and control data into separate coded blocks during said second period of time; and

an antenna for transmitting coded blocks of control data using the same single tone used to transmit coded blocks of user data.

33. A computer readable medium embodying machine executable instructions for controlling a communications device to implement a method, the method comprising:

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio;

coding user data and control data into separate coded blocks during said second period of time; and

using the same single tone used to transmit coded blocks of user data to transmit coded blocks of control data.

34. A wireless terminal, comprising:

a multi-tone mode transmission control module for controlling transmission during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a first mode of operation, said transmission during said first mode of operation being controlled to use multiple OFDM tones simultaneously to transmit at least some user data in a first upJ.ink signal to a first base station, the first signal having a first peak to average power ratio;

a single-tone mode transmission control module for controlling transmission during a second period of time including a second plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

a communications module for selecting one of a plurality of supported different modulation methods to be used in transmitting said at least some user data during at least a portion of said first period of time; and

a transmitter for transmitting user data modulated using a single modulation method supported during said second period of time.

35. The wireless terminal of claim 34, wherein said supported different modulation methods include QAIVI 4 and QAM 16 modulation and wherein said single supported modulation method is a QPSK modulation method.

36. A wireless terminal, comprising:

multi-tone mode transmission control means for controlling transmission during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a first mode of operation, said transmission during said first mode of operation being controlled to use multiple OFDM tones simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

single-tone mode transmission control means for controlling transmission during a second period of time including a second plurality of consecutive OFDM symbol transmission time periods in which said wireless terminal operates in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

communications means for selecting one of a plurality of supported different modulation methods to be used in transmitting said at least some user data during at least a portion of said first period of time; and

transmitter means for transmitting user data modulated using a single modulation method supported during said second period of time.

37. The wireless terminal of claim 36, wherein said supported different modulation methods include QAM 4 and QAN 16 modulation and wherein said single supported modulation method is a QPSK modulation method.

38. A computer readable medium embodying machine executable instructions for controlling a communications device to implement a method, the method comprising:

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio;

selecting one of a plurality of supported different modulation methods to be used in transmitting said at least some user data during at least a portion of said first period of time; and

using a single supported modulation method during said second period of time.

39. A wireless terminal comprising:

a multi-tone mode transmission control module for controlling transmission, during a first multi-tone OFDM uplink mode of operation, to use multiple OFDM tones at the same time to transmit signals to a first base station;

a single-tone mode transmission control module for controlling transmission, during a single tone OFDM uplink mode of operation, to use a single OFDM tone to transmit signals to a second base station, said second base station having a minimum possible physical distance from said wireless terminal which is greater than the minimum possible physical distance which can occur between said wireless terminal and said first base station, where said second base station is a satellite base station and said first base station is a terrestrial base station; and

a switching control module for controlling switching from the first mode of operation to the second mode of operation when a handoff occurs from said first base station to said second base station and to control the wireless terminal to cease sending acknowledgements in response to received user data as part of switching from the first mode to the second mode of operation.

40. A wireless terminal comprising:

multi-tone mode transmission control means for controlling transmission, during a first multi-tone OFDM uplink mode of operation, to use multiple OFDM tones at the same time to transmit signals to a first base station;

single-tone mode transmission control means for controlling transmission, during a single tone OFDM uplink mode of operation, to use a single OFDM tone to transmit signals to a second base station, said second base station having a minimum possible physical distance from said wireless terminal which is greater than the minimum possible physical distance. which can occur between said wireless terminal and said first base station, where said second base station is a satellite base station and said first base station is a terrestrial base station; and

switching control means for controlling switching from the first mode of operation to the second mode of operation when a handoff occurs from said first base station to said second base station and to control the wireless terminal to cease sending acknowledgements in response to received user data as part of switching from the first mode to the second mode of operation.

41. A computer readable medium embodying machine executable instructions for controlling a wireless terminal to implement a method, the method comprising:

operating a wireless terminal in a first, multi-tone OFDM uplink mode of operation, in which the wireless terminal uses multiple OFDM tones at the.same time to transmit signals to a first base station;

operating a wireless terminal in a second, single tone OFDM uplink mode of operation, in which the wireless terminal uses a single OFDM tone to transmit signals to a second base station, said second base station having a minimum possible physical distance from said wireless terminal which is greater than the minimum possible physical distance which can occur between said wireless terminal and said first base station, where said second base station is a satellite base station and said first base station is a terrestrial base station;

switching from the first mode of operation to the second mode of operation when a handoff occurs from said first base station to said second base station; and

wherein switching between the first and second modes of operation includes ceasing to send acknowledgements in response to received user data.

42. A wireless communications terminal comprising:

a switching control module for controlling switching between a first multi-tone OFDM uplink mode of operation in which the wireless terminal uses multiple OFDM tones at the same time to transmit signals to a base station, and a second single tone OFDM uplink mode of operation;

a transmitter for transmitting user data using a single OFDM tone during said single tone uplink mode of operation and for transmitting user data using multiple OFDM tones at the same time in said multi-tone uplink mode of operation;

wherein said control module switches from multi-tone uplink mode of operation to said single tone uplink mode of operation when said wireless terminal switches from communicating with a terrestrial base station to a satellite base station; and

an uplink signaling frequency control module for reducing the frequency of uplink control signals which are transmitted from the wireless terminal when operation switches from said multi-tone uplink mode of operation to said single tone uplink mode of operation.

43. A computer readable medium embodying machine executable instructions for controlling a wireless terminal to implement a method, the method comprising:

operating the wireless terminal in a first, multi-tone OFDM uplink mode of operation, in which the wireless terminal uses multiple OFDM tones at the same time to transmit signals to a first base station;

operating a wireless terminal in a second, single tone OFDM uplink mode of operation, in which the wireless terminal uses a single OFDM tone to transmit signals to a second base station, said second base station having a minimum possible physical distance from said wireless terminal which is greater than the minimum possible physical distance which can occur between said wireless terminal and said first base station, where said second base station is a satellite base station and said first base station is a terrestrial base station;

switching from the first mode of operation to the second mode of operation when a handoff occurs from said first base station to said second base station; and

wherein switching between the first and second modes of operation includes reducing the frequency of uplink control signals which are transmitted from the wireless terminal.

44. A device comprising:

a processor configured to control a wireless terminal to implement a communications method, the method comprising;

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

receiving user data from the first base station during said first period of time;

transmitting acknowledgements to the first base station according to a first predetermined acknowledgement scheme; and

receiving user data from the second base station during said second period of time without acknowledging receipt of said user data.

45. A device comprising:

a processor configured to control a wireless terminal to implement a communications method, the method comprising;

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio, wherein said second peak to average power ratio is lower than said first peak to average power ratio;

during said first mode of operation, prior to transmission of said user data during said first period of time, coding at least some of said user data to be transmitted during said first period of time in a code block separate from a code block used to communicate control information during said first period of time;

during said, second mode of operation, prior to transmission of said user data during said second period of time, multiplexing the user data to be transmitted during said second period of time with control data which is also to be transmitted during said second period of time; and

coding said multiplexed control and user data in a single code block.

46. A device comprising:

a processor configured to control a wireless terminal to implement a communications method, the method comprising;

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operating in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operating in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio; and

wherein during said second period of time the second base station is at least 3 times further away from the wireless terminal than the first base station is from the wireless terminal during said first period of time; and

wherein said single tone used during said second mode of operation occupies a position in a logical uplink transmission timing structure which is dedicated during said first mode of operation to a dedicated control channel used during said first period of time exclusively for control signaling.

47. A device comprising:

a processor configured to control a wireless terminal 3 to;

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operate in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a firstpeak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operate in a second mode of operation during which at most one oFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio;

wherein during said second period of time the second base station is at least 3 times further away from the wireless terminal than the first base station is from the wireless terminal during said first period of time; and

wherein said single tone used during said second mode of operation has a fixed one to one association with a base station assigned wireless terminal identifier; and

wherein during said first mode of operation, said tones used to transmit user data do not have a fixed one to one association with a base station assigned wireless terminal identifier.

48. A device comprising:

a processor configured to control a wireless terminal to;

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operate in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operate in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio;

encode user data and control data into separate coded blocks during said second period of time; and

use the same single tone used to transmit coded blocks of user data to transmit coded blocks of control data.

49. A device comprising:

a processor configured to control a wireless terminal to implement a communications method, the method comprising;

during a first period of time including a first plurality of consecutive OFDM symbol transmission time periods, operate in a first mode of operation during which multiple OFDM tones are used simultaneously to transmit at least some user data in a first uplink signal to a first base station, the first signal having a first peak to average power ratio;

during a second period of time, including a second plurality of consecutive OFDM symbol transmission time periods, operate in a second mode of operation during which at most one OFDM tone is used to transmit at least some user data in a second signal to a second base station, the second signal having a second peak to average power ratio which is different from said first peak to average power ratio;

select one of a plurality of supported different modulation methods to be used in transmitting said at least some user data during at least a portion of said first period of time; and

use a single supported modulation method during said second period of time.

50. A device comprising a processor configured to implement an OFDM communications method, the method comprising:

controlling a wireless terminal in a first, multi-tone OFDM uplink mode of operation, in which the wireless terminal uses multiple OFDM tones at the same time to transmit signals to a first base station;

controlling the wireless terminal in a second, single tone OFDM uplink mode of operation, in which the wireless terminal uses a single OFDM tone to transmit signals to a second base station, said second base station having a minimum possible physical distance from said wireless terminal which is greater than the minimum possible physical distance which can occur between said wireless terminal and said first base station, where said second base station is a satellite base station and said first base station isa terrestrial base station;

switching from the first mode of operation to the second mode of operation when a handoff occurs from said first base station to said second base station; and

wherein switching between the first and second modes of operation includes ceasing to send acknowledgements in response to received user data.

51. A device comprising:

a processor configured to implement an OFDM communications method, the method comprising;

controlling a wireless terminal in a first, multi-tone OFDM uplink mode of operation, in which the wireless terminal uses multiple OFDM tones at the same time to transmit signals to a first base station;

controlling the wireless terminal in a second, single tone OFDM uplink mode of operation, in which the wireless terminal uses a single OFDM tone to transmit signals to a second base station, said second base station having a minimum possible physical distance from said wireless terminal which is greater than the minimum possible physical distance which can occur between said wireless terminal and said first base station, where said second base station is a satellite base station and said first base station is a terrestrial base station;

switching from the first mode of operation to the second mode of operation when a handoff occurs from said first base station to said second base station; and

wherein switching between the first and second modes of operation includes reducing the frequency of uplink control signals which are transmitted from the wireless terminal.

52. A device comprising:

a processor configured to implement a communications method, the method comprising;

operating a wireless terminal to transmit OFDM signals to a first base station, where the distance between the wireless terminal and base station exceeds 100 miles;

wherein a cyclic prefix transmitted with an OFDM symbol to the base station has a duration which is less than the maximum round trip propagation delay between the wireless terminal and the base station;

wherein the wireless terminal transmits to said base station using at most 1 tone at a time; and

wherein said at most one tone is a logical tone dedicated to said wireless terminal by said base station for use in uplink signaling to the exclusion of use by other wireless terminals.

53. A device comprising:

a processor configured to implement a communications method, the method comprising;

operating a wireless terminal to transmit OFDM signals to a first base station, where the distance between the wireless terminal and base station exceeds 100 miles; and

wherein a cyclic prefix transmitted with an OFDM symbol to the base station has a duration which is less than the maximum round trip propagation delay between the wireless terminal and the base station;

operating the wireless terminal to communicate with a terrestrial base station using multiple OFDM tones simultaneously for. uplink communications to the terrestrial base station; and

using the same peak power constraint used for transmitting to the first base station for transmitting to the terrestrial base station but using a higher average power for transmitting signals to the first base station than is used for transmitting signals to the terrestrial base station.