Multiple access wireless communications system using a multisector configuration

• US 20040095880A1
• Filed: 08/13/2003
• Published: 05/20/2004
• Est. Priority Date: 08/26/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Lane, Frank A.
• Granted Patent: US 7,388,845 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04B 7/12 Frequency diversity
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

Power control methods and apparatus for use in a sectorized cell of an OFDM communications system are described. Each sector of a cell uses the same frequencies and transmission times and is synchronized with the other sectors in the cell in terms of tone frequencies used at any given time and symbol transmission times. Tones are allocated to channels in each cell in the same manner so that each channel in a sector has a corresponding channel in another sector. Power differences between channels in different sectors are maintained to be within a pre-selected power difference. Different channels in a cell are assigned different power levels. Wireless terminals are assigned to channels based on channel feedback information. Wireless terminals with poor channel conditions are allocated to higher power channels than wireless terminals with good channel conditions. Lower power channels often include more tones per symbol time than high power channels.

Claims

1. A method of operating a transmitter in a cell which uses a set of tones to transmit into a first sector of said cell over a plurality of symbol times using tones from said set of tones, the cell including a second sector adjoining said first sector, said transmitter transmitting into said second sector on first and second communications channels, the first communications channel including a first subset of said set of tones during each of a first subset of said plurality of symbol times, the second communications channel including a second subset of said set of tones during each of said first subset of said plurality of times, said first subset of said set of tones and said second subset of said set of tones being different from each other during each symbol time, the method comprising:

operating the transmitter to transmit on said first and second channels into said first sector in a synchronous manner with transmissions made by said transmitter into said second sector; and

controlling a total transmission power of the tones corresponding to the first channel in the first sector during said first subset of said plurality of symbol times to be greater than 20% and less than 500% of a total power of the tones corresponding to the first channel transmitted into the second sector, during said first subset of said plurality of symbol times.

2. The method of claim 1, wherein controlling the total transmission power of the tones corresponding to the first channel includes limiting the total power used in said first subset of symbol times to be no more than a fixed fraction of a maximum average total transmission power used by said transmitter in the first sector during any 1 hour period, said fixed fraction also being used to limit the total transmission power of the tones corresponding to the first channel in the second sector during the first subset of symbol times to be no more than said fixed fraction of a maximum average total transmission power used by said transmitter in the second sector during any 1 hour period, said fixed fraction being less than 100%.

3. The method of claim 1, wherein said symbol times are orthogonal frequency division multiplexed symbol transmission time periods and wherein said tones are orthogonal frequency division tones.

4. The method of claim 1, wherein said set of tones is different during at least two symbol times in said first subset of said plurality of symbol tones.

5. The method of claim 1, wherein said transmitter transmits into said first sector symbols corresponding to a first constellation on said first channel during said first subset of said plurality of symbol times and transmits symbols corresponding to a second constellation during a second subset of said plurality of symbol times, the second constellation including more symbols than the first constellation, the method further comprising:

controlling a total transmission power of the tones corresponding to the first channel in the first sector during the second subset of said plurality of symbol times to be greater than 50% and less than 200% of a total power of the tones transmitted in the second sector corresponding to the first channel during said second subset of said plurality of symbol times.

6. The method of claim 1, wherein said transmitter transmits into said first sector symbols at a first channel coding rate on said first channel during said first subset of said plurality of symbol times and transmits symbols at a second channel coding rate during a second subset of said plurality of symbol times, said second channel coding rate being higher than said first channel coding rate, the method further comprising:

controlling a total transmission power of the tones corresponding to the first channel in the first sector during the second subset of said plurality of symbol times to be greater than 50% and less than 200% of a total power of the tones transmitted in the second sector corresponding to the first channel during said second subset of said plurality of symbol times.

7. The method of claim 1, wherein the total transmission power of the transmitted tones corresponding to the first channel in the first sector during the first subset of said plurality of symbol times is equal to the total transmission power of the transmitted tones in the first channel in the second sector during said first subset of said plurality of symbol times.

8. The method of claim 1, wherein the first subset of said plurality of symbol times includes at least 14 consecutive symbol times.

9. The method of claim 1, further comprising:

controlling the total power of the tones transmitted in the first sector corresponding to the first channel during a fourth subset of said plurality of symbol times to be one of greater than 200% and less than 50% of the total power of the tones transmitted in said first sector corresponding to the second channel during said fourth subset of said plurality of symbol times.

10. The method of claim 9, wherein the fourth subset of said plurality of symbol times includes at least 14 consecutive symbol times.

11. The method of claim 10, wherein the first and fourth subsets of said plurality of symbol times are the same.

12. The method of claim 1, wherein said first and second sectors use a third communications channel during a second subset of said plurality of symbol times, the third communications channel including a third subset of said set of tones during each of said second subset of said plurality of symbol times, the method further comprising:

controlling said transmitter during said second subset of said plurality of symbol times, to limit the total transmission power on tones corresponding to said third communications channel transmitted by said transmitter to be less than 10% of the total transmission power used by said transmitter to transmit tones into said second sector corresponding to the third channel during said second subset of said plurality of symbol times.

13. The method of claim 1, wherein said first and second sectors use a third communications channel during a second subset of said plurality of symbol times, the third communications channel including a third subset of said set of tones during each of said second subset of said plurality of symbol times, the method further comprising:

controlling said transmitter during said second subset of said plurality of symbol times, to limit total transmission power on tones corresponding to said third communications channel transmitted by said transmitter to be zero.

14. The method of claim 12, wherein the method is further directed to controlling the allocation of resources corresponding to said third communications channel to wireless terminals, the method further comprising:

identifying wireless terminals in a boundary area which corresponds to a boundary between said first and second sectors; and

allocating said resources corresponding to the said third channel to at least one of said identified wireless terminals.

15. The method of claim 14, further comprising:

receiving from a wireless terminal first information indicating an amount of intersector interference measured by said wireless terminal and second information indicating an amount of background interference measured by said wireless terminal.

16. The method of claim 14, wherein identifying wireless terminals in the boundary area includes:

receiving a signal from a wireless terminal in said boundary area a signal indicating that said wireless terminal is in said boundary area.

17. The method of claim 16, wherein said signal indicating that a wireless terminal is in said boundary area is a location information signal.

18. The method of claim 12, wherein said first and second sector use said third communications channel during a third subset of said plurality of symbol times, said third subset of said plurality of symbol times being different from said second subset of said plurality of symbol times, the method further comprising:

controlling said transmitter during said third subset of said plurality of symbol times, to use a total transmission power on tones corresponding to said third communications channel transmitted by said transmitter into the first sector to be at least 1000% used by said second sector to transmit tones corresponding to the third channel into the second sector during said third subset of said plurality of symbol times.

19. The method of claim 18, wherein the second and third subsets of said plurality of symbol times are interspersed according to a fixed pattern.

20. A base station for use in a communications cell including first and second sectors, the second sector adjoining the first sector, the base station comprising:

a transmitter which uses a set of tones to transmit into a first sector of said cell over a plurality of symbol times using tones from a set of tones, said transmitter transmitting into said second sector on first and second communications channels, the first communications channel including a first subset of said set of tones during each of a first subset of said plurality of symbol times, the second communications channel including a second subset of said set of tones during each of said first subset of said plurality of times, said first subset of said set of tones and said second subset of said set of tones being different from each other during each symbol time;

means for controlling the transmitter to transmit on said first and second channels into 11 said first sector in a synchronous manner with transmissions made by said transmitter into said second sector; and

power control means for controlling a total transmission power of the tones corresponding to the first channel in the first sector during said first subset of said plurality of symbol times to be greater than 20% and less than 500% of a total power of the tones corresponding to the first channel transmitted into the second sector, during said first subset of said plurality of symbol times.

21. The base station of claim 20, wherein said means for controlling the total transmission power of the tones corresponding to the first channel includes means for limiting the total power used in said first subset of symbol times to be no more than a fixed fraction of a maximum average total transmission power used by said transmitter in the first sector during any 1 hour period, said fixed fraction also being used to limit the total transmission power of the tones corresponding to the first channel in the second sector during the first subset of symbol times to be no more than said fixed fraction of a maximum average total transmission power used by said transmitter in the second sector during any 1 hour period, said fixed fraction being less than 100%.

22. The base station of claim 20, wherein said symbol times are orthogonal frequency division multiplexed symbol transmission time periods and wherein said tones are orthogonal frequency division tones.

23. The base station of claim 20, wherein said set of tones is different during at least two symbol times in said first subset of said plurality of symbol tones.

24. The base station of claim 20, wherein said transmitter transmits into said first sector symbols corresponding to a first constellation on said first channel during said first subset of said plurality of symbol times and transmits symbols corresponding to a second constellation during a second subset of said plurality of symbol times, the second constellation including more symbols than the first constellation, the method further comprising:

means for controlling a total transmission power of the tones corresponding to the first channel in the first sector during the second subset of said plurality of symbol times to be greater than 50% and less than 200% of a total power of the tones transmitted in the second sector corresponding to the first channel during said second subset of said plurality of symbol times.

25. The base station of claim 20, wherein said transmitter transmits into said first sector symbols at a first channel coding rate on said first channel during said first subset of said plurality of symbol times and transmits symbols at a second channel coding rate during a second subset of said plurality of symbol times, said second channel coding rate being higher than said first channel coding rate, the method further comprising:

means for controlling a total transmission power of the tones corresponding to the first channel in the first sector during the second subset of said plurality of symbol times to be greater than 50% and less than 200% of a total power of the tones transmitted in the second sector corresponding to the first channel during said second subset of said plurality of symbol times.

26. The base station of claim 20, further comprising:

means for controlling the total power of the tones transmitted in the first sector corresponding to the first channel during a fourth subset of said plurality of symbol times to be one of greater than 200% and less than 50% of the total power of the tones transmitted in said first sector corresponding to the second channel during said fourth subset of said plurality of symbol times.

27. The base station of claim 20, wherein said first and second sectors use a third communications channel during a second subset of said plurality of symbol times, the third communications channel including a third subset of said set of tones during each of said second subset of said plurality of symbol times, the base station further comprising:

means for controlling said transmitter during said second subset of said plurality of symbol times, to limit the total transmission power on tones corresponding to said third communications channel transmitted by said transmitter to be less than 10% of the total transmission power used by said transmitter to transmit tones into said second sector corresponding to the third channel during said second subset of said plurality of symbol times.

28. The base station of claim 20, wherein said first and second sectors use a third communications channel during a second subset of said plurality of symbol times, the third communications channel including a third subset of said set of tones during each of said second subset of said plurality of symbol times, the base station further comprising:

means for controlling said transmitter during said second subset of said plurality of symbol times, to limit total transmission power on tones corresponding to said third communications channel transmitted by said transmitter to be zero.

29. The base station of claim 27, further comprising:

means for identifying wireless terminals in a boundary area which corresponds to a boundary between said first and second sectors; and

means for allocating said resources corresponding to the said third channel to at least one of said identified wireless terminals.

30. The base station of claim 29, further comprising:

a receiver for receiving from a wireless terminal first information indicating an amount of intersector interference measured by said wireless terminal and second information indicating an amount of background interference measured by said wireless terminal.

31. The base station of claim 29, further comprising:

a receiver for receiving a signal from a wireless terminal in said boundary area a signal indicating that said wireless terminal is in said boundary area.