ADAPTIVE TRANSMISSION METHOD AND A BASE STATION USING THE METHOD

• US 20090227249A1
• Filed: 03/10/2008
• Published: 09/10/2009
• Est. Priority Date: 03/10/2008
• Status: Active Grant

• Current Assignee: Elektrobit Wireless Communications OY (Bittium Oyj)
• Original Assignee: Elektrobit Wireless Communications OY (Bittium Oyj)
• Inventors: Ylitalo, Juha
• Granted Patent: US 8,085,721 B2
• Time in Patent Office: Days
• US Class Current: 455/424
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0689 using different transmission schemes, at least one of them being a diversity transmission scheme

Abstract

The invention relates to a method, a base station and a computer program for selecting a spatial transmission method for a next downlink transmission in a base station. The base station can be a WiMAX, a UMTS or a 3GPP LTE base station. According to the invention the base station makes a selection between beamforming (BF), space-time coding (STC) or MIMO for a next downlink frame. The selection is based on uplink measurements and feedback information from a particular mobile station whereto the next downlink frame is to be transmitted.

Claims

1. A method for selecting a downlink spatial transmission mode from a multi-antenna base station to a mobile terminal, the method comprising:

estimating uplink channel powers of utilized antenna beams;

comparing the uplink channel powers of the antenna beams to each other;

estimating a reception signal quality measure for the mobile terminal;

comparing the estimated reception signal quality measure to at least one threshold value; and

selecting a spatial transmission mode for a next downlink frame to the mobile terminal by utilizing at least one of the comparison results.

2. The method according to claim 1, wherein estimation of the channel uplink powers comprises:

estimating in the base station at base band uplink channel impulse responses of the utilized antenna beams; and

calculating uplink channel powers of the antenna beams by utilizing the estimated uplink channel impulse responses.

3. The method according to claim 1, wherein utilized downlink spatial transmission mode is one of the following:

beamforming (BF), space-time coding (STC) or multiple input multiple output scheme (MIMO).

4. The method according to claim 1, wherein the reception signal quality measure is at least one of the following:

Signal-to-Interference-and-Noise Ratio (SINR), Signal-to-Noise Ratio (SNR), Carrier to-Interference-plus-Noise Ratio (CINR) or Received Signal Strength Indicator (RSSI).

5. The method according to claim 3, wherein beamforming (BF) is selected when the calculated uplink channel powers differ from each other more than a first threshold value.

6. The method according to claim 4, wherein space-time coding (STC) is selected when the calculated uplink channel powers differ from each other less than a first threshold value and when the reception signal quality measure is a signal-to-interference-and-noise ratio (SINR) and it is below a second threshold value.

7. The method according to claim 4, wherein multiple input multiple output scheme (MIMO) is selected when the uplink calculated channel powers differ from each other less than a first threshold value and when the reception signal quality measure is a signal-to-interference-and-noise ratio (SINR) and it is above a second threshold value.

8. The method according to claim 3, wherein space-time coding (STC) is selected when the calculated uplink channel powers differ from each other less than a first threshold value but the channel power difference is more than 5 dB.

9. The method according to claim 4, wherein multiple input multiple output scheme (MIMO) is selected when the calculated uplink channel powers differs from each other less than a first threshold and the channel power difference is less than 5 dB and when the reception signal quality measure is a signal-to-interference-and-noise ratio (SINR) and it is above a second threshold value.

10. The method according to claim 1, wherein a value of the reception quality measure is feedback information of the mobile terminal.

11. The method according to claim 1, wherein a value of the reception quality measure is an uplink signal measurement at the base station.

12. A base station comprising:

a transceiver;

a beamformer;

a multi-antenna array; and

a processor unit which is configured to;

estimate uplink channel powers of utilized antenna beams;

compare the uplink channel powers of the antenna beams to each other;

estimate a reception signal quality measure for a mobile terminal;

compare the estimated reception signal quality measure to at least one threshold value; and

select a spatial transmission mode for a next downlink frame to the mobile terminal by utilizing at least one of the comparison results.

13. The base station according to claim 12, wherein for estimating the uplink channel powers the processor unit is configured to:

estimate at base band uplink channel impulse responses of the utilized antenna beams; and

calculate uplink channel powers of the antenna beams by utilizing the estimated uplink channel impulse responses.

14. The base station according to claim 13, wherein the processor unit is configured to select one of the following to the downlink spatial transmission mode:

beamforming (BF), space-time coding (STC) or multiple input multiple output scheme (MIMO).

15. The base station according to claim 13, wherein the processor unit is configured to utilize as the reception signal quality measure at least one of the following:

Signal-to-Interference-and-Noise Ratio (SINR), Signal-to-Noise Ratio (SNR), Carrier to-Interference-plus Noise Ratio (CINR) or Received Signal Strength Indicator (RSSI).

16. The base station according to claim 14, wherein the processor unit is configured to select beamforming (BF) when the calculated uplink channel powers differs from each other more than a first threshold value.

17. The base station according to claim 15, wherein the processor unit is configured to select space-time coding (STC) when the calculated uplink channel powers differs from each other less than a first threshold value and when the reception signal quality measure is a signal-to-interference-and-noise ratio (SINR) and it is below a second threshold value.

18. The base station according to claim 15, wherein the processor unit is configured to select multiple input multiple output scheme (MIMO) when the calculated uplink channel powers differ from each other less than a first threshold value and when the reception signal quality measure is a signal-to-interference-and-noise ratio level (SINR) and it is above a second threshold value.

19. The base station according to claim 14, wherein the processor unit is configured to select space-time coding (STC) when the calculated uplink channel powers differ from each other less than a first threshold value but the channel power difference is more than 5 dB.

20. The base station according to claim 15, wherein the processor unit is configured to select multiple input multiple output scheme (MIMO) when the calculated uplink channel powers differ from each other less than a first threshold and the channel power difference is less than 5 dB and when the reception signal quality measure is a signal-to-interference-and-noise ratio (SINR) and it is above a second threshold value.

21. The base station according to claim 13, wherein the processor unit is configured to obtain the second quality measure from feedback information of a mobile terminal.

22. The base station according to claim 13, wherein the processor unit is configured to estimate the second quality measure at a mobile terminal by uplink power level measurements at the base station.

23. The base station according to claim 12, wherein the base station is one of the following:

a WiMAX base station, an UMTS base station or a 3GPP LTE base station.

24. A computer readable medium encoded with software readable by a data processing device for selecting a spatial transmission mode comprising:

computer readable code for estimating uplink channel powers of utilized antenna beams;

computer readable code for comparing the channel powers of the antenna beams to each other;

computer readable code for estimating a reception signal quality measure for the mobile terminal;

computer readable code for comparing the estimated reception signal quality measure to at least one threshold value; and

computer readable code for selecting a spatial transmission mode for a downlink frame to the mobile terminal by utilizing the comparison results.

25. The computer readable medium according to claim 24, comprising for estimating the uplink channel powers:

computer readable code for estimating channel impulse responses of utilized antenna beams utilizing an uplink subframe from a mobile terminal; and

computer readable code for calculating uplink channel powers of the received antenna beams by utilizing the estimated channel impulse responses.

26. The computer readable medium according to claim 25, comprising computer readable code for selecting one of the following as the spatial transmission mode:

beamforming (BF), space-time coding (STC) or multiple input multiple output scheme (MIMO).

27. The computer readable medium according to claim 25, comprising computer readable code for utilizing as the reception signal quality measure at least one of the following:

Signal-to-Interference-and-Noise Ratio (SINR), Signal-to-Noise Ratio (SNR), Carrier to-Interference-plus-Noise Ratio (CINR) or Received Signal Strength Indicator (RSSI).

28. The computer readable medium according to claim 26 comprising computer readable code for selecting beamforming (BF) when the calculated uplink channel powers differ from each other more than a first threshold value.

29. The computer readable medium according to claim 27 comprising computer readable code for selecting space-time coding (STC) when the calculated uplink channel powers differ from each other less than a first threshold value and when the reception signal quality measure is a signal-to-interference-and-noise ratio (SINR) and it is below a second threshold value.

30. The computer readable medium according to claim 27 comprising computer readable code for selecting multiple input multiple output scheme (MIMO) when the uplink calculated channel powers differ from each other less than a first threshold value and when the reception signal quality measure is a signal-to-interference-and-noise ratio level (SINR) and it is above a second threshold value.

31. The computer readable medium according to claim 27 comprising computer readable code for selecting space-time coding (STC) when the calculated uplink channel powers differ from each other less than a first threshold value but the channel power difference is more than 5 dB.

32. The computer readable medium according to claim 27 comprising computer readable code for selecting multiple input multiple output scheme (MIMO) when the calculated uplink channel powers differ from each other less than a first threshold and the channel power difference is less than 5 dB and when the reception signal quality measure is signal-to-interference-and-noise ratio level (SINR) and it is above a second threshold value.

33. The computer readable medium according to claim 24 comprising computer readable code for obtaining the second quality measure from feedback information of a mobile terminal.

34. The computer readable medium according to claim 24 comprising computer readable code for estimating a value of the reception quality measure of the mobile station utilizing an uplink signal measurement.