Realtime power control in OFDM systems

• US 6,795,426 B1
• Filed: 06/23/2000
• Issued: 09/21/2004
• Est. Priority Date: 07/06/1999
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Raleigh, Gregory G., Pollack, Michael, Jones, Vincent K. IV, Raissinia, Ali
• Primary Examiner(s): Pezzlo, John
• Application Number:
  US09/603,237
• Time in Patent Office: 1,551 Days
• Field of Search: 370/331, 370/345, 370/241, 370/280, 370/329, 370/252, 370/448, 370/210, 725/129, 725/124, 324/620, 324/76.21, 375/224, 455/69, 455/423, 455/455, 341/139
• US Class Current: 370/345
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/54 Signalisation aspects of the TPC commands, e.g. frame structure
• CPC Class Codes: H04W 80/02 Data link layer protocols

Abstract

Systems and methods for efficiently transmitting power level information in a point to multipoint wireless system. Multiple subscriber units may transmit indications of their power level within a shared burst where one or more subchannels are allocated to each subscriber unit. The burst holding the power level information may be understood by the MAC layer to be a data burst. In this way, a wireline MAC protocol may be applied to wireless applications.

Claims

1. In a communication system, a method for operating a selected node of said communication system, said method comprising:

receiving from a central access point a transmission comprising a MAC layer identifier to be used to request transmission of a power measurement burst;

receiving a MAC management message comprising said MAC layer identifier;

developing a burst of L frequency domain symbols wherein L-k frequency domain symbols are given a zero value to allow for transmission by other nodes and one or more of said k of said L frequency domain symbols are set to facilitate measurement of power level;

converting said burst of frequency domain symbols into a time domain burst of symbols;

in response to said MAC management message, transmitting said time domain burst of symbols from said selected node as said power measurement burst;

receiving power adjustment information that was developed based on measurement of said power measurement burst; and

adjusting transmission power based on said power adjustment information.

2. The method of claim 1 wherein said at least one or more of said L-k frequency domain symbols are reserved for transmission of power measurement information by said other nodes.

3. The method of claim 1 wherein said MAC layer management message identifies said k frequency domain symbols within said burst.

4. The method of claim 1 wherein said MAC layer identifier is used to request transmission from multiple subscriber units.

5. In a communication system, a method for operating a central access point of a point to multipoint communication system, said method comprising:

transmitting a MAC layer management message to first and second subscriber units to request transmission of a time domain power measurement burst, said MAC layer management message comprising MAC layer identifiers referring to said first and second subscriber units;

receiving said time domain power measurement burst at said central access point, said time domain power measurement burst having been transmitted in response to said MAC layer management message;

converting said time domain power measurement burst to a frequency domain burst of frequency domain symbols;

using a first set of one or more frequency domain symbols of said burst to measure power transmitted by said first subscriber unit and using a second set of one or more frequency domain symbols to measure power transmitted by said second subscriber unit;

developing power adjustment information for said first subscriber unit based on measured power of said first subscriber unit;

developing power adjustment information for said second subscriber unit based on measured power of said second subscriber unit;

transmitting said power adjustment information for said first subscriber unit to said first subscriber unit; and

transmitting said power adjustment information for said second subscriber unit to said second subscriber unit.

6. The method of claim 5 wherein said MAC layer management message further comprises:

information identifying positions of said first set of one or more frequency domain symbols within said frequency domain burst.

7. The method of claim 5 wherein sending comprises broadcasting to both said first subscriber unit and said second subscriber unit.

8. In a communication system, apparatus for operating a selected node of said communication system, said apparatus comprising:

a power measurement burst generator that develops a burst of L frequency domain symbols wherein L-k frequency domain symbols are given a zero value to allow transmission by other nodes and one or more of said k of said L frequency domain symbols are set to facilitate measurement of power level;

a transform block that converts said burst of frequency domain symbols into a time domain burst of symbols;

a transmitter system that transmits said time domain burst of symbols from said selected node as a power measurement burst;

a receiver system that receives power adjustment information developed based on said power measurement burst;

a physical layer control block that adjust transmission power of said transmitter system based on said power adjustment information; and

a central processing unit that receives from a central access point a registration message comprising a MAC layer identifier to be used to request transmission of said power transmission burst, said MAC layer identifier identifying said selected node and other nodes of said communication system;

said central processing unit directing transmission of said power transmission burst in response to a MAC management message comprising said MAC layer identifier.

9. The apparatus of claim 8 wherein said at least one or more of said L-k frequency domain symbols are reserved for transmission of power measurement information by said other nodes.

10. The apparatus of claim 8 wherein a transmission received by said selected node identifies said k frequency domain symbols within said burst.

11. The apparatus of claim 8 wherein at least one of said k frequency domain symbols is set to a predetermined value to facilitate measurement of power level.

12. In a communication system, apparatus for operating a central access point of a point to multipoint communication system, said apparatus comprising:

a receiver system that receives a time domain power measurement burst;

a transform block that converts said time domain power measurement burst to a frequency domain burst of frequency domain symbols;

a power measurement processor that uses a first set of one or more frequency domain symbols of said burst to measure power transmitted by a first subscriber unit and uses a second set of one or more frequency domain symbols to measure power transmitted by a second subscriber unit;

a physical layer control processor that determines first power adjustment information based on said measured power of said first subscriber unit and second power adjustment information based on said measured power of said second subscriber unit; and

a transmitter system that sends a MAC layer management message to first and second subscriber units to request transmission of said time domain power measurement burst, said MAC layer management message comprising MAC layer identifiers referring to said first and second subscriber units and sends said first power adjustment information to said first subscriber unit and said second power adjustment information to said second subscriber unit.

13. The apparatus of claim 12 wherein said MAC layer management message comprises:

information identifying positions of said first set of one or more frequency domain symbols within said frequency domain burst.

14. In a communication system, apparatus for operating a selected node of said communication system, said apparatus comprising:

means for receiving from a central access point a transmission comprising a MAC layer identifier to be used to request transmission of a power measurement burst;

means for receiving a MAC management message comprising said MAC layer identifier;

means for developing a burst of L frequency domain symbols wherein L-k frequency domain symbols are given a zero value to allow transmission by other nodes and one or more of said k of said L frequency domain symbols are set to facilitate measurement of power level;

means for converting said burst of frequency domain symbols into a time domain burst of symbols;

means for, in response to said MAC management message, transmitting said time domain burst of symbols from said selected node as a power measurement burst;

means for receiving power adjustment information that was developed based on measurement of said power measurement burst; and

means for adjusting transmission power based on said power adjustment information.

15. In a communication system, apparatus for operating a central access point of a point to multipoint communication system, said apparatus comprising:

means for transmitting a MAC layer management message to first and second subscriber units to request transmission of a time domain power measurement burst, said MAC layer management message comprising MAC layer identifiers referring to said first and second subscriber units;

means for receiving said time domain power measurement burst at said central access point, said time domain power measurement burst having been sent in response to said MAC layer management message;

means for converting said time domain power measurement burst to a frequency domain burst of frequency domain symbols;

means for using a first set of one or more frequency domain symbols of said burst to measure power transmitted by said first subscriber unit and using a second set of one or more frequency domain symbols to measure power transmitted by said second subscriber unit; and

means for developing power adjustment information for said first subscriber unit based on measured power of said first subscriber unit;

means for developing power adjustment information for said second subscriber unit based on measured power of said second subscriber unit;

means for transmitting said power adjustment information for said first subscriber unit to said first subscriber unit; and

means for transmitting said power adjustment information for said second subscriber unit to said second subscriber unit.