Weighted open loop power control in a time division duplex communication system

• US 6,597,723 B1
• Filed: 03/21/2000
• Issued: 07/22/2003
• Est. Priority Date: 03/21/2000
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Shin, Sung-Hyuk, Zeira, Ariela
• Primary Examiner(s): GHEBRETINSAE, TEMESGHEN
• Application Number:
  US09/532,349
• Time in Patent Office: 1,218 Days
• Field of Search: 375/130, 375/140, 375/295, 455/522, 455/69, 370/342, 370/252
• US Class Current: 375/130
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04W 52/10 Open loop power control
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/242 taking into account path loss
• CPC Class Codes: H04W 52/246 where the output power of a terminal is based on a path parameter calculated in said terminal
• CPC Class Codes: H04W 52/248 where transmission power control commands are generated based on a path parameter

Abstract

The invention controls transmission power levels in a spread spectrum time division duplex communication station. A first communication station transmits a communication to a second communication station. The second station receives the communication and measures its received power level. Based on, in part, the received communication'"'"'s power level and the communication'"'"'s transmission power level, a path loss estimate is determined. A quality of the path loss estimate is also determined. The transmission power level for a communication from the second station to the first station is based on, in part, weighting the path loss estimate in response to the estimate'"'"'s quality.

Claims

1. A method for controlling transmission power levels in a spread spectrum time division duplex communication system having frames with time slots for communication, the method comprising:

transmitting a first communication having a transmission power level in a first time slot from a first communication station;

receiving at a second communication station the first communication and measuring a power level of the first communication as received;

determining a path loss estimate based on in part the measured received first communication power level and the first communication transmission power level;

setting a transmission power level for a second communication in a second time slot from the second station to the first station based on in part combining the path loss estimate weighted by a first factor with a long term path loss estimate weighted by a second factor, wherein the first and second factors are a function of a time separation of the first and second time slots; and

determining a quality, α

of the path loss estimate based on in part a number of time slots, D, between the first and second time slot; and

wherein the first factor is α and

the second factor is 1−

α

.

2. The method of claim 1 further comprising:

determining the long term path loss estimate based at least in part upon an average of path loss estimates of communications sent from the first station to the second station.

3. The method of claim 1 wherein a maximum time slot delay is D_max and the determined quality, α

, is determined by

4. The method of claim 1 wherein a maximum allowed time slot delay is D_max-allowed and the determined quality, α

, is determined by

5. The method of claim 1 wherein the set transmission power level compensates for differences in the uplink and downlink gains.

6. The method of claim 1 wherein the first station is a base station and the second station is a user equipment.

7. The method of claim 1 wherein the first station is a user equipment and the second station is a base station.

8. A spread spectrum time division duplex communication system having a first and second communication station, the system using frames with time slots for communication, the system comprising:

the first station comprising;

means for transmitting a first communication having a transmit power level in a first time slot; and

the second station comprising;

means for receiving the first communication and measuring a power level of the first communication as received;

means for determining a path loss estimate based on in part the measured received first communication power level and the first communication transmission power level;

means for setting a transmission power level for a second communication in a second time slot based on in part combining the path loss estimate weighted by a first factor with a long term path loss estimate weighted by a second factor, wherein the first and second factors are a function of a time separation of the first and second time slots;

means for transmitting the second communication in the second time slot at the set transmission power level; and

means for determining a quality, α

, of the path loss estimate based on in part a number of time slots, D, between the first and second time slot; and

wherein the first factor is α and

the second factor is 1−

α

.

9. The system of claim 8 wherein the second station further comprises:

means for determining the long term path loss estimate based at least in part upon an average of path loss estimates of communications sent from the first station to the second station.

10. The system of claim 8 wherein a maximum time slot delay is D_max and the determined quality, α

, is determined by

11. The system of claim 8 wherein a maximum allowed time slot delay is D_max-allowed and the determined quality, α

, is determined by

12. The system of claim 8 herein the setting means sets the transmission power level to compensate for differences in the uplink and downlink gains.

13. The system of claim 8 herein the first station is a base station and the second station is a user equipment.

14. The system of claim 8 wherein the first station is a user equipment and the second station is a base station.

15. A communication station having its transmission power level controlled in a spread spectrum time division duplex communication system, the system using frames with time slots for communication and having a second communication station transmitting a first communication in a first time slot, the communication station comprising:

at least one antenna for receiving the first communication and transmitting an amplified second communication in a second time slot;

a channel estimation device having an input configured to receive the received first communication for producing channel information;

a data estimation device having inputs configured to receive the received first communication and the channel information for producing interpreted data;

a power measurement device having an input configured to receive the channel information for producing a measurement of a received power level of the first communication;

a pathloss estimation device having an input configured to receive the measured received power level for producing a pathloss estimate for the first communication;

a quality measurement device for producing a quality measurement based at least in part upon a time separation of the first time slot and a second time slot;

a transmit power calculation device having inputs configured to receive the pathloss estimation and the quality measurement for producing a power control signal based at least in part upon combining the path loss estimate weighted by a first factor and a long term pathloss estimate weighted by a second factor, wherein the first and second factors are based on in part the quality measurement; and

an amplifier having inputs configured to receive the power control signal and a second communication to be transmitted in the second time slot for amplifying the second communication in response to the power control signal to produce the amplified second communication.

16. The communication station of claim 15 further comprising:

a data generator for producing communication data;

a spreading and training sequence insertion device having an input configured to receive the communication data for producing the second communication in the second time slot; and

a modulator having an input configured to receive the amplified second communication for modulating the amplified second communication to radio frequency prior to transmission.

17. The communication station of claim 15 further comprising:

a demodulator having an input configured to receive the received first communication for producing a baseband signal; and

wherein both the channel estimation device and the data estimation device have an input configured to receive the baseband signal.

18. The communication station of claim 15 wherein the quality measurement is in the range of zero to one and the first factor is the quality measurement and the second factor is one minus the quality measurement.

19. The communication station of claim 15 wherein the first station is a base station and the second station is a user equipment.

20. The communication station of claim 15 wherein the first station is a user equipment and the second station is a base station.