Combined power control and space-time diversity in mobile cellular communications

• US 6,377,812 B1
• Filed: 11/20/1998
• Issued: 04/23/2002
• Est. Priority Date: 11/20/1997
• Status: Expired due to Fees

• Current Assignee: University of Maryland
• Original Assignee: University of Maryland
• Inventors: Tassiulas, Leandros, Liu, K. J. Ray, Rashid-Farrokhi, Farrokh
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US09/196,226
• Time in Patent Office: 1,250 Days
• Field of Search: 455/450, 455/501, 455/506, 455/522, 455/63, 455/67.3, 455/68, 455/13.3, 455/69, 455/513, 455/277.2, 455/278.1, 455/523, 455/422, 455/133, 455/134, 455/135, 455/561, 455/275, 455/283, 455/3.3, 455/562, 370/335, 370/342, 370/431, 375/206, 375/341, 375/348, 375/347, 375/324, 375/232
• US Class Current: 455/522
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

In a mobile cellular communications system power control and space-time diversity are applied in combination to the uplink and downlink. In the uplink, mobile powers and equalization/diversity combining vectors at base stations are, calculated jointly, with the result that the mobile transmitted power is minimized, while the Signal to Noise Ratio (SNR) at each link is maintained above a threshold. In the downlink, a multitap transmit diversity strategy adjusts the transmit weight vectors with the result that the SNR at each mobile is set to a specified value. The combination of power control and space-time diversity apply to networks with fading channels, including networks in which the number of cochannels and multipaths are larger than the number of antenna elements. The invention achieves the optimal solution for the uplink that minimizes the mobile power, and achieves a feasible solution for the downlink if there exists any.

Claims

1. A method for adaptive receiver beamforming and transmitter power control in a cellular radio network having communications links between base stations and mobile stations, the network employing base station receiver diversity and mobile station power control, the method comprising the following steps:

determining a refined base station receive diversity weight vector for which a first quality measure is highest; and

using the refined base station receive diversity weight vector to determine a refined set of mobile transmitter powers for which a second quality measure is highest.

2. The method of claim 1 wherein the first quality measure is the minimum value in the set of base station receiver signal to noise ratios.

3. The method of claim 1 wherein the second quality measure is the reciprocal of the sum of the mobile station transmitter powers.

4. The method of claim 1 wherein the receive signals at the base stations are oversampled.

5. A method for adaptive receiver beamforming and transmitter power control in a cellular radio network having communications links between base stations and mobile stations, the network employing base station receiver diversity and mobile station power control, the method comprising the steps of:

determining a refined base station receive diversity weight vector for which a first quality measure is highest; and

using the refined base station receive diversity weight vector to determine a refined set of mobile transmitter powers for which a second quality measure is highest, such that total power transmission is minimized while maintaining a selected minimum transmission quality.

6. The method of claim 5 wherein the total transmitted power is defined as:

$\min <br><br>\underset{i}{\sum <br><br>}<br><br>P<br><br>\text{\hspace{1em}<br><br>}<br><br>i$$A<br><br>\text{\hspace{1em}<br><br>}<br><br>P$$S,T,\mathrm{\Gamma <br><br>}\ge <br><br>\mathrm{\gamma <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>i.$

7. The method according to claim 5 including determining the joint power and control and combining vector.

8. The method according to claim 5 including performing optimal power control over the network based upon local information.

12. The method of claim 5, further comprising providing the one of the base stations with a channel response feedback pertaining to a respective one of the mobile stations for optimizing the respective one of the links therebetween.

13. The method of claim 5, further comprising providing the one of the base stations with interference feedback pertaining to a respective one of the mobile stations for optimizing the respective one of the links therebetween.

9. A method for adaptive transmitter beamforming and power control in a cellular radio network having communications links between base stations and mobile stations, the network employing transmitter diversity and power control in the base stations, the method comprising the step of

jointly determining a refined base station transmit diversity weight vector and a refined set of base station transmitter powers, for which a quality measure is satisfied.

10. The method of claim 9 wherein the quality measure is a set of predetermined values of the mobile receiver signal to noise ratios.

11. The method of claim 9 wherein the receive signals at the base stations are oversampled.