Power control in OFDM and OFDMA wireless communication networks

• US 7,826,435 B1
• Filed: 03/03/2005
• Issued: 11/02/2010
• Est. Priority Date: 03/05/2004
• Status: Active Grant

• Current Assignee: Yarnton Technologies LLC
• Original Assignee: ZTE Corporation
• Inventors: Zhu, Keqiang, Wu, Jun, Fang, Yonggang
• Primary Examiner(s): Hoang; Thai D
• Application Number:
  US11/072,741
• Time in Patent Office: 2,070 Days
• Field of Search: 370/282, 370/335, 370/342, 375/130, 375260-264, 455/69
• US Class Current: 370/342
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

Methods and systems are described for implementing power control in OFDM and OFDMA wireless communication systems.

Claims

1. A method, comprising:

measuring power levels of orthogonal frequency division multiplexing (OFDM) subcarriers that are generated from a transmitter and are received at a receiver in a wireless communication system using OFDM subcarriers;

providing a time division duplex (TDD) in an air link between the transmitter and the receiver;

estimating a signal amplitude of a signal carrying the OFDM subcarriers to pre-compensate the signal at the transmitter, wherein the pre-compensated signal includes the OFDM subcarriers, is transmitted by the transmitter, and is received at the receiver; and

controlling transmitting power levels of the OFDM subcarriers at the transmitter in response to the measured power levels and the estimated signal amplitude to make the power levels of subcarriers received at the receiver approximately equal to one another.

2. The method as in claim 1, further comprising:

separating the OFDM subcarriers into different OFDM subcarrier groups where each OFDM subcarrier group comprises a plurality of OFDM subcarriers that are different from OFDM subcarriers in another OFDM subcarrier group; and

controlling an averaged power of the OFDM subcarriers group received at the receiver so that received averaged power levels of different OFDM subcarrier groups are approximately equal.

3. The method as in claim 1, wherein the wireless communication system additionally uses a frequency division duplex (FDD) in an air link between the transmitter and the receiver, the method further comprising:

measuring the power levels of OFDM subcarriers at the receiver;

sending information on measured power levels of the OFDM subcarriers at the receiver to the transmitter; and

controlling the transmitter in response to the information.

4. The method as in claim 3, wherein each received OFDM subcarrier is measured at the receiver and data for measured power in each OFDM subcarrier is sent to the transmitter.

5. The method as in claim 3, wherein the received OFDM subcarriers at the receiver from the transmitter are divided into a plurality of groups each having a set of OFDM subcarriers, and wherein received averaged power levels of the groups are measured and information on measured averaged power levels of the groups is sent to the transmitter.

6. The method as in claim 1 further comprising performing both the measuring and the controlling at the transmitter.

7. The method as in claim 1, wherein the system is an orthogonal frequency division multiple access (OFDMA) system.

8. The method of claim 1, wherein measuring power levels of orthogonal frequency division multiplexing (OFDM) subcarriers includes measuring a respective power level of each OFDM subcarrier.

9. The method of claim 8, wherein controlling transmitting power levels of the OFDM subcarriers at the transmitter in response to the measured power levels includes controlling the respective power level of each OFDM subcarrier to be approximately equal to a respective power level of another OFDM subcarrier.

10. A communication system, comprising:

a plurality of base stations spatially distributed to wirelessly communicate with subscriber stations via radio links that comprise orthogonal frequency division multiplexing (OFDM) subcarriers;

a plurality of base station controllers, each coupled to control and communicate with two or more base stations within the plurality of base stations;

a first power control mechanism to measure power levels of OFDM subcarriers in a signal that is either (1) generated at a transmitting subscriber station and received at a receiving base station, or (2) generated at a transmitting base station and received at a receiving subscriber station;

a second power control mechanism to control an averaged power level of a signal measured at a receiving base station and generated from a transmitting subscriber station to be approximately equal to averaged power levels of signals received at said receiving base station that are generated from other subscriber stations;

a mechanism that provides a time division duplex (TDD) in an air link between a transmitter and a receiver, wherein the first and the second power control mechanisms are implemented at the transmitter, wherein, in the TDD, the transmitter transmits a pre-compensated signal to the receiver, wherein the pre-compensated signal includes the OFDM subcarriers,

wherein the second power control mechanism is configured to control transmitting power levels of the OFDM subcarriers at the transmitter in response to the measured power levels and an estimated signal amplitude of the signal carrying the OFDM subcarriers to make the power levels of subcarriers received at the receiver approximately equal to one another.

11. The system as in claim 10, wherein the second power control mechanism operates without a feedback from the receiver to the transmitter.

12. The system as in claim 10, further comprising:

a mechanism that provides a frequency division duplex (FDD) in an air link between the transmitter and the receiver, wherein the first power control mechanism measures the power levels of OFDM subcarriers at the receiver; and

a mechanism that feeds information on measured power levels of the OFDM subcarriers at the receiver to the transmitter, wherein the second power control mechanism controls the transmitter in response to the information.

13. The system of claim 12, wherein the second power control mechanism controls the transmitter to transmit a signal to said receiving base station having a power level approximately equal to the averaged power levels of signals received at said receiving base station.

14. A method, comprising:

transmitting orthogonal frequency division multiplexing (OFDM) subcarriers from a transmitter to a receiver in a wireless communication system that uses OFDM subcarriers and frequency division duplex (FDD) in an air link between the transmitter and the receiver;

separating the OFDM subcarriers into different OFDM subcarrier groups where each OFDM subcarrier group comprises a plurality of OFDM subcarriers that are different from OFDM subcarriers in another OFDM subcarrier group;

measuring an averaged power level of OFDM subcarriers in each of the OFDM subcarrier groups received at the receiver;

communicating the measured averaged power level of each of the OFDM subcarrier groups to the transmitter;

estimating a signal amplitude of a signal carrying the OFDM subcarriers to pre-compensate the signal at the transmitter, wherein the pre-compensated signal includes the OFDM subcarriers, is transmitted by the transmitter, and is received at the receiver; and

controlling the transmitting power levels of the OFDM subcarriers at the transmitter, based on the measured averaged power levels and the estimated signal amplitude, to make averaged power levels of different OFDM subcarrier groups approximately equal at the receiver.

15. The method as in claim 14, wherein the wireless communication system is an orthogonal frequency division multiplexing (OFDM) system.

16. The method as in claim 14, wherein the system is an orthogonal frequency division multiple access (OFDMA) system.

17. The method of claim 14, wherein the receiver is a mobile wireless phone.