Communication system, primary station and method of transmit power control

• US 20070165577A1
• Filed: 05/05/2005
• Published: 07/19/2007
• Est. Priority Date: 05/06/2004
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Baker, Matthew, Moulsley, Timothy
• Granted Patent: US 9,078,222 B2
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04W 52/327 Power control of multicast channels

Abstract

A transmit power control scheme for use in point-to-multipoint communication uses a random access channel for power control signals transmitted by the receiving stations (200).

Claims

1. A method of transmit power control in a communication system (50) comprising a primary station (100) and a plurality of secondary stations (200), the method comprising at each secondary station (200):

receiving a first signal transmitted by the primary station (100);

measuring a parameter of the received first signal;

deriving a second signal from the measured parameter;

transmitting the second signal; and

at the primary station (100);

transmitting the first signal;

receiving the second signals;

deriving a power control signal from the received second signals;

controlling the transmit power of the first signal in accordance with the power control signal;

wherein the transmission of the second signals comprises a plurality of the secondary stations (200) transmitting common signals in a common time period in a common frequency allocation.

2. A method as claimed in claim 1, wherein at each secondary station (200) deriving the second signal comprises selecting a combination of code, time period and frequency allocation from a plurality of combinations, the selection being dependent on a value of the measured parameter.

3. A method as claimed in claim 2, wherein the plurality of combinations comprises different codes for transmission in a common time period.

4. A method as claimed in claim 2, wherein the plurality of combinations comprises a common code for transmission in different time periods.

5. A method as claimed in claim 2, wherein the plurality of combinations comprises a common code for transmission in a common time period using different frequency allocations.

6. A method as claimed in claim 1, wherein the transmitting of the second signal takes place with a sub-unity probability.

7. A method as claimed in claim 6, wherein the probability is dependent on the value of the measured parameter of the received first signal.

8. A method as claimed in claim 1, wherein each second signal comprises at least one of:

an indication to increase the transmit power;

an indication to decrease the transmit power;

an indication that the first signal was decoded successfully;

an indication that the first signal contained unrecoverable errors;

an indication that an error rate of the first signal exceeds a threshold value;

an indication of a quality level of the first signal.

9. A method as claimed in claim 8, wherein the indication of a quality level comprises at least one of:

an indication of an error rate;

an indication of a signal-to-interference ratio;

an indication of a signal-to-noise ratio;

an indication of a signal level.

10. A method as claimed in claim 1, comprising:

at each secondary station (200), increasing transmit power during the second signal;

at the primary station (100), in response to receiving a portion of the second signal, transmitting a third signal; and

at each secondary station (200), in response to receiving the third signal, ceasing the power increase.

11. A method as claimed in claim 10, wherein ceasing the power increase comprises ceasing transmission of the second signal.

12. A communication system (50) comprising a primary station (100) and a plurality of secondary stations (200), each secondary station (200) comprising:

means (240) for receiving a first signal transmitted by the primary station (100);

means (250) for measuring a parameter of the received first signal;

means (250) for deriving a second signal from the measured parameter;

means (210) for transmitting the second signal; and

the primary station (100) comprising;

means (110) for transmitting the first signal;

means (140) for receiving the second signals;

means (150) for deriving a power control signal from the received second signals;

means (160) for controlling the transmit power of the first signal in accordance with the power control signal;

wherein the means (210) for transmitting the second signals are adapted to transmit a common signal in a common time period in a common frequency allocation.

13. A communication system (50) as claimed in claim 12, wherein the means (250) for deriving the second signal is adapted to select a combination of code, time period and frequency allocation from a plurality of combinations, the selection being dependent on a value of the measured parameter.

14. A communication system (50) as claimed in claim 13, wherein the plurality of combinations comprises different codes for transmission in a common time period.

15. A communication system (50) as claimed in claim 13, wherein the plurality of combinations comprises a common code for transmission in different time periods.

16. A communication system (50) as claimed in claim 13, wherein the plurality of combinations comprises a common code for transmission in a common time period using different frequency allocations.

17. A communication system (50) as claimed in claim 12, wherein the means (210) for transmitting the second signal is adapted to transmit the second signal with a sub-unity probability.

18. A communication system (5) as claimed in claim 17, wherein the probability is dependent on the value of the measured parameter of the received first signal.

19. A communication system (50) as claimed in claim 12, wherein each second signal comprises at least one of:

an indication to increase the transmit power;

an indication to decrease the transmit power;

an indication that the first signal was decoded successfully;

an indication that the first signal contained unrecoverable errors;

an indication that an error rate of the first signal exceeds a threshold value;

an indication of a quality level of the first signal.

20. A communication system (50) as claimed in claim 19, wherein the indication of a quality level comprises at least one of:

an indication of an error rate;

an indication of a signal-to-interference ratio;

an indication of a signal-to-noise ratio;

an indication of a signal level.

21. A communication system (50) as claimed in claim 12, wherein:

the secondary station means (210) for transmitting is adapted to increase its transmit power during the second signal;

the primary station (100) comprises means (110, 140, 150), responsive to receiving a portion of the second signal, for transmitting a third signal; and

the secondary station means (210) for transmitting is further adapted to, responsive to receiving the third signal, cease the power increase.

22. A primary station (100) for use in a communication system (50) comprising a plurality of secondary stations (200), the primary station comprising:

means (110) for transmitting a first signal;

means (140) for receiving from secondary stations (200) second signals comprising a plurality of common signals received in a common time period in a common frequency allocation;

means (150) for deriving a power control signal from the received second signals;

means (160) for controlling the transmit power of the first signal in accordance with the power control signal.