Power control in point-to-multipoint systems

• US 6,308,080 B1
• Filed: 05/15/1998
• Issued: 10/23/2001
• Est. Priority Date: 05/16/1997
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Burt, Donald G., Marin, James Scott, Myers, William K., Langston, J. Leland, Darbe, Kevin B.
• Primary Examiner(s): MAUNG, NAY AUNG
• Application Number:
  US09/079,472
• Time in Patent Office: 1,257 Days
• Field of Search: 455/522, 455/403, 455/422, 455/67.1, 455/67.3, 455/127, 455/63, 455/62, 455/296, 455/69, 455/126, 455/561, 455/562
• US Class Current: 455/522
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 distributing total power among users or channels
• CPC Class Codes: H04W 84/14 WLL [Wireless Local Loop]; RLL [Radio Local Loop]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

The invention provides methods and systems for power control in point-to-multipoint communications systems. Methods are described for both downstream and upstream control. Subscriber signals received at the base station 11 are level detected at receiver 77 and power adjust processing 79 and a control signal is sent to control output from the subscriber transmitter 65. The invention maximizes the signal-to-noise ratio and signal-to-interference ratio for subscribers (CPE) while minimizing transmitted power. The invention is ideal for use in local multipoint distribution service (LMDS) systems.

Claims

1. A point to multipoint communications system comprising:

a plurality of two way subscribers in a given area;

a base station providing two way service to said subscribers in said given area; and

a power control system coupled to both said subscribers and said base station for controlling both upstream and down stream power;

said base station has a node receiver for receiving multiple carrier frequencies from multiple subscribers and said power control system controls the upstream power level, a beacon, pilot or calibration generator coupled to the input of said base station node receiver to determine the gain of said node receiver for received signals from said subscribers.

2. The system of claim 1 wherein power from said base station is controlled by maintaining output power levels of one or more transmitters of said base station.

3. The system of claim 2 having at least one ALC loop between the input and output of said base station transmitters.

4. The system of claim 2 including an off-the-air monitor and pickup antenna located in a given area for detecting power transmitted by said one or more base station transmitters and generating and providing control signals to said one or more transmitters of said base station for controlling the power from said base station.

5. The system of claim 4 wherein said monitor senses the composite power level and said control signal sets the power level of the output from said base station.

6. The system of claim 4 wherein said monitor senses the power of any individual channel and said monitor provides a gain control signal proportional to the sensed power level for each channel to control the transmitter power corresponding to that sensed at each channel.

7. The system of claim 1 wherein said subscriber signals received at the base station are level detected and the detected level from the subscribers are used to control the output from the subscriber transmitters.

8. The system of claim 7 including means at said base station for providing a communications message protocol for communicating to said subscriber to change the transmit power level from the subscribers.

9. The system of claim 1 including means for adjusting remote station transmit power so the received signal levels from all subscribers at the receiver of the base station are equal.

11. The system of claim 7 wherein said base station includes means coupled to said base station receiver for determining received signal level or signal to noise from each subscriber and means for generating and providing a signal to said subscriber representing said signal strength and said subscriber includes means for calculating a power change and for controlling said subscriber transmitter.

12. The system of claim 1 wherein a receiver of said subscriber includes an AGC loop in a tuner/demodulator thereof to detect the signal level and a gain control amplifier at the input to adjust the gain at the input in response to detected gain level to maintain substantially constant level to a network interface unit.

13. The system of claim 1 wherein said calibration tone signal is controllable in amplitude and/or frequency.

14. The system of claim 1 wherein said node receiver includes a frequency selective spectrum analyzer to monitor said subscriber signals.

15. The system of claim 1 wherein said subscriber includes detector means for determining set point and a computer means to automatically increment, decrement or calculate the subscriber transmitter power.

16. The system of claim 1 including means for determining path loss by radiating a beacon signal from a region near said subscribers and receiving said beacon signals at said base station and computing loss change.

17. The system of claim 1 including a subscriber (CPE) power adjustment and propagation processing means at said base station which determines the desired power for each subscriber.

18. The system of claim 1 wherein said node receiver comprises a plurality of subsystem receivers and said system includes a calibration tone generator for injecting a calibration tone to one of said subsystem node receivers to calibrate the gain of the node subsystem receivers.

19. The system of claim 18 wherein the system includes means for detecting said calibration tone signal and comparing the received signal strength at said calibration subsystem receiver to that in the other subsystem receivers.

10. The system of claim 91 including a processor which determines a desired power for each subscriber and provides a signal representing a changes to each subscriber.

20. A point to multipoint communications system comprising a plurality of two way subscribers in a given area, a base station providing two way service to said subscribers in said given area, and a power control system coupled to both said subscribers and said base station for controlling both upstream and downstream power;

said base station has a node receiver for receiving multiple carrier frequencies from multiple subscribers and said power control system controls the upstream power level, said node receiver comprises a base station tower receiver and a base station base receiver with a fiber optic coupler therebetween.