TRANSMISSION POWER CONTROL SCHEMES FOR D2D COMMUNICATIONS

• US 20140198694A1
• Filed: 01/17/2013
• Published: 07/17/2014
• Est. Priority Date: 01/17/2013
• Status: Active Grant

• Current Assignee: Apple Inc., Intel Corporation
• Original Assignee: Intel Deutschland GmbH (Intel Corporation)
• Inventors: Yang, Rongzhen, Yin, Hujun, Schmidt, Andreas, Chen, Feng, Fwu, Jong-Kae
• Granted Patent: US 9,030,984 B2
• Time in Patent Office: Days
• US Class Current: 370/311
• CPC Class Codes: H04W 52/06 TPC algorithms
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/10 Open loop power control
• CPC Class Codes: H04W 52/242 taking into account path loss
• CPC Class Codes: H04W 52/367 Power values between minimum and maximum limits, e.g. dynamic range
• CPC Class Codes: H04W 52/383 power control in peer-to-peer links
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames

Abstract

Power control schemes for D2D communications are described. The schemes control the transmission power of a UE during D2D communications in a manner that reduces interference while maintaining the D2D communications link and the cellular link with the eNB. Open-loop and/or closed-loop techniques are employed.

Claims

1. A user equipment (UE) device, comprising:

a radio transceiver for providing an air interface for communicating with an evolved node B (eNB) and for device-to-device (D2D) communications; and

processing circuitry connected to the radio transceiver to;

receive allocations of time-frequency resources for D2D communications from the eNB;

establish a D2D communications session with a second UE and exchange D2D power control parameters with the second UE that include a closed-loop power control function P_D2D,CLPC;

receive an open-loop power control function P_{D2D, OLPC} via the air interface for controlling transmission power during D2D communications;

maintain a transmission power during D2D transmissions as a function of the open-loop and closed-loop power control functions.

2. The device of claim 1 wherein the processing circuitry is further to:

maintain the transmission power during D2D transmissions as the value of a function P_D2D calculated for each subframe i as;

P_D2D(i)=min(P_D2D,MAX,P_D2D,OLPC(i)+P_D2D,CLPC(i))

where P_D2D,MAX is a maximum allowed transmission power during D2D communications.

3. The device of claim 2 wherein the closed-loop power control function P_D2D,CLPC (i)) is defined as:

P_D2D,CLPC(i))=f_D2D(i)

where f_D2D (i) is a function of a value transmitted by the second UE.

4. The device of claim 3 wherein:

f_D2D(i)=Δ

_D2D(i)

where Δ

_D2D (i) is an absolute transmission power value transmitted by the second UE.

5. The device of claim 3 wherein:

f_D2D(i)=f_D2D(i−

1)+Δ

_D2D(i)

where Δ

_D2D (i) is a positive or negative incremental power control command transmitted by the second UE and where f_D2D (i) is initialized to zero.

6. The device of claim 2 wherein the closed-loop power control function P_D2D,CLPC (i)) is defined as:

P_D2D,CLPC(i))=f_D2D(i)+f_eNB(i)

where f_D2D (i) is a function of a value transmitted by the second UE and f_eNB (i) is a function of a value transmitted by the eNB.

7. The device of claim 6 wherein:

f_eNB(i)=Δ

_eNB(i)

where Δ

_eNB (i) is an absolute transmission power value transmitted by the eNB.

8. The device of claim 6 wherein:

f_eNB(i)=f_eNB(i−

1)+Δ

_eNB(i)

where Δ

_eNB (i) is a positive or negative incremental power control command transmitted by the eNB and where f_eNB (i) is initialized to zero.

9. The device of claim 3 wherein the open-loop power control function P_{D2D, OLPC} is set to a constant zero value.

10. The device of claim 6 wherein the open-loop power control function P_{D2D, OLPC} is set to a constant zero value.

11. The device of claim 3 wherein the open-loop power control function P_{D2D, OLPC} is defined as:

P_D2D,OLPC(i)=P_0,eNB+α

(L_eNB)

where P_0,eNB is a base power setting for communicating with the eNB, α

is a fractional power control parameter between 0 and 1, and L_eNB is a measured path loss value for the communications path between the device and the eNB.

12. The device of claim 6 wherein the open-loop power control function P_{D2D, OLPC} is defined as:

P_D2D,OLPC(i)=P_0,eNB+α

(L_eNB)

where P_0,eNB is a base power setting for communicating with the eNB, α

is a fractional power control parameter between 0 and 1, and L_eNB is a measured path loss value for the communications path between the device and the eNB.

13. The device of claim 3 wherein the open-loop power control function P_{D2D, OLPC} is defined as:

P_D2D,OLPC(i)=P_0,D2D+L_D2D+SINR_target

where P_0,eD2D is a base power setting for D2D communications, SINR_target is a target signal to interference and noise ratio set for D2D communications, and L_D2D is a measured path loss value for the communications path between the device and the second UE.

14. The device of claim 6 wherein the open-loop power control function P_{D2D, OLPC} is defined as:

P_D2D,OLPC(i)=P_0,D2D+L_D2D+SINR_target

where P_0,D2D is a base power setting for D2D communications, SINR_target is a target signal to interference and noise ratio set for D2D communications, and L_D2D is a measured path loss value for the communications path between the device and the second UE.

15. The device of claim 3 wherein the open-loop power control function P_{D2D, OLPC} is defined as:

P_D2D,OLPC(i)=min(P_0,eNB+α

(L_eNB),P_0,D2D+L_D2D+SINR_target)

where P_0,eNB is a base power setting for communicating with the eNB, α

is a fractional power control parameter between 0 and 1, L_eNB is a measured path loss value for the communications path between the device and the eNB, P_0,D2D is a base power setting for D2D communications, SINR_target is a target signal to interference and noise ratio set for D2D communications, and L_D2D is a measured path loss value for the communications path between the device and the second UE.

16. The device of claim 6 wherein the open-loop power control function P_{D2D, OLPC} is defined as:

P_D2D,OLPC(i)=min(P_0,eNB+α

(L_eNB),P_0,D2D+L_D2D+SINR_target)

where P_0,eNB is a base power setting for communicating with the eNB, α

is a fractional power control parameter between 0 and 1, L_eNB is a measured path loss value for the communications path between the device and the eNB, P_0,D2D is a base power setting for D2D communications, SINR_target is a target signal to interference and noise ratio set for D2D communications, and L_D2D is a measured path loss value for the communications path between the device and the second UE.

17. A method for operating user equipment (UE) in a Long Term Evolution (LTE) cell served by an eNB, comprising:

establishing a communication link with the eNB and establishing a D2D communications link with a second UE;

receiving a closed-loop power control signal from the second UE designed to maintain the D2D link with reduced interference;

receiving an open-loop power control signal from the eNB designed to maintain the eNB link with reduced interference;

maintaining the transmission power level during D2D transmission in accordance with the open-loop and closed-loop power control signals.

18. The method of claim 17 further comprising:

exchanging D2D power control parameters with the second UE that include a closed-loop power control function P_D2D,CLPC;

receiving an open-loop power control function P_{D2D, OLPC} via the air interface for controlling transmission power during D2D communications;

maintaining the transmission power during D2D transmissions as a function of the open-loop and closed-loop power control functions.

19. The method of claim 18 further comprising:

maintaining the transmission power during D2D transmissions as the value of a function P_D2D calculated for each subframe i as;

P_D2D(i)=min(P_D2D,MAX,P_D2D,OLPC(i)+P_D2D,CLPC(i))

where P_D2D,MAX is a maximum allowed transmission power during D2D communications.

20. The method of claim 19 wherein the open-loop power control function P_{D2D, OLPC} is defined as:

P_D2D,OLPC(i)=P_0,eNB+α

(L_eNB)

where P_0,eNB is a base power setting for communicating with the eNB, α

is a fractional power control parameter between 0 and 1, and L_eNB is a measured path loss value for the communications path between the device and the eNB.

21. A user equipment (UE) device, comprising:

a radio transceiver for communicating with an evolved node B (eNB) and for device-to-device (D2D) communications;

processing circuitry connected to the radio transceiver to;

establish a D2D communications link with a second UE;

adjust a transmission power during D2D communications in accordance with a power control command received from the second UE and in accordance with a a measured path loss parameter received from the eNB.

22. The device of claim 21 wherein the processing circuitry is further to increment or decrement the transmission power in accordance with a power control command received from the second UE.

23. The device of claim 21 wherein the processing circuitry is further to set the transmission power at a value indicated by a power control command received from the second UE.

24. The device of claim 21 wherein the processing circuitry is further to increment or decrement the transmission power in accordance with a power control command received from the eNB.

25. The device of claim 21 wherein the processing circuitry is further to set the transmission power at a value indicated by a power control command received from the eNB.