COMMUNICATIONS SYSTEM, METHODS AND APPARATUS

• US 20060285481A1
• Filed: 07/18/2005
• Published: 12/21/2006
• 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.
• Granted Patent: US 7,403,470 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• 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. (canceled)

2. 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; and

wherein the second base station is during said second period of time, 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.

13. The method of claim 2, 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.

14. The method of claim 2, 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.

15. The method of claim 14, 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.

16. The method of claim 15, 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.

3. (canceled)

4. (canceled)

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 said second peak to average power ratio is lower than said first peak to average power ratio; and

wherein said second peak to average power ratio is at least 4 db lower than said first peak to average power ratio.

6. (canceled)

7. 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, and wherein said first base station is a terrestrial base station and said second base station is a satellite base station;

wherein transmitting at least some user data during said first period of time includes transmitting user data at a rate of at least 4.8 Kbits/sec; and

wherein transmitting at least some user data during said second period of time includes transmitting user data at a rate of at least 4.8 Kbits/sec.

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, 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.

9. The method of claim 8, 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.

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, 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.

11. 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;

hopping, during said first period of time, the multiple OFDM tones used simultaneously to transmit at least some user data during said first period of time at a first rate; and

hopping, during said second period of time, the single OFDM tone used to transmit at least some user data during said second period of time at said first rate.

12. The method of claim 11, wherein said first rate is a rate which is a multiple of a symbol transmission time period, said hopping rate resulting in the same physical tones being used for a plurality of consecutive symbol transmission time periods in each of said first and second time period.

17. 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.

18. The method of claim 17, 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.

19. (canceled)

20. 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.

21. The method of claim 20, 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.

22. The method of claim 21, 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.

23. (canceled)

24. 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;

wherein transmitting during said multi-tone OFDM uplink mode of operation includes transmitting signals during a first period of time using a first peak to average power ratio; and

wherein transmitting during said multi-tone OFDM uplink mode of operation includes transmitting signals during a second period of time having the same duration as said first period of time using a second peak to average power ratio, the second peak to average power ratio being at least 4 dB smaller than the first peak to average power ratio.

25. (canceled)

26. 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.

27. 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.

28. The OFDM communications method of claim 27, wherein switching between the first and second modes of operation includes ceasing to transmit requests for traffic channel segment assignments.

29. 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.

30. The method of claim 29 wherein the wireless terminal transmits to said base station using at most 1 tone at a time.

31. The method of claim 30, 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.

32. The method of claim 31, wherein said one logical tone corresponds to a physical tone which is determined over time according to a predetermined hopping sequence.

33. The method of claim 29, further comprising operating the wireless terminal to communicate with a terrestrial base station using multiple OFDM tones simultaneously for uplink communications to the terrestrial base station.

34. The method of claim 33, further comprising:

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.

35. The method of claim 34, 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.

36. The method of claim 35, wherein said same frequency band is a 1500 MHz frequency band, the band including frequencies in the range of 1500 to 1599 MHz.

37. (canceled)

38. 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; and

a power transmission control module for controlling transmission power during said single tone uplink mode of operation to maintain an average peak to average power ratio which is at least 4 dB lower than a peak to average power ratio maintained during said multi-tone uplink mode of operation.

39. 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; and

wherein said control module 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.

40. The wireless terminal of claim 39, wherein 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.

41. The wireless terminal of claim 40, wherein the wireless terminal includes 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.

42. The wireless terminal of claim 41,

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

and

wherein the wireless terminal 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.

43. (canceled)

44. 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.

46. The OFDM communications system of claim 44, 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.

45. (canceled)