Centralized control of relay operation
Techniques for centralized control of relay operation are described. In an aspect, a designated network entity (e.g., a base station or a network controller) may control the operation of relay stations within its coverage area. The network entity may select certain user equipments (UEs) to be relay UEs that can serve as relay stations for other UEs, e.g., based on pathloss between the UEs and a base station, the locations of the UEs, battery power levels of the UEs, fairness considerations, etc. The network entity may also select a specific relay UE to serve as a relay station for a client UE desiring to communicate with a base station, e.g., based on pilot measurements from relay UEs for the client UE. The network entity may also control transmission of discovery pilots by relay UEs and/or client UEs for relay detection.
1. A method for wireless communication, comprising:
transmitting, from a first user equipment (UE) to a second UE, a pilot indicating that the first UE outside a coverage area of a base station desires to communicate with the base station that currently serves the second UE, the pilot being used for at least a pilot measurement between the first UE and the second UE, and the pilot being used to detect the first UE;
determining, at the first UE, that the second UE will serve as a relay station between the base station and the first UE based at least in part on the pilot measurement, and the base station being unaware of the first UE prior to receiving the pilot measurement from the second UE; and
transmitting data, from the first UE to the second UE, for subsequent transmission to the base station.
2. The method of claim 1 , wherein the determining comprises receiving, at the first UE, an indication that the second UE will serve as a relay station for the first UE.
3. The method of claim 1 , wherein the data is transmitted from the first UE to the second UE after determining that the second UE will serve as the relay station.
4. The method of claim 1 , wherein the pilot comprises at least a synchronization signal, a reference signal, a transmission sent on at least one physical channel, or a combination thereof.
5. An apparatus for wireless communication, comprising:
means for transmitting, from a first user equipment (UE) to a second UE, a pilot indicating that the first UE outside a coverage area of a base station desires to communicate with the base station that currently serves the second UE, the pilot being used for at least a pilot measurement between the first UE and the second UE, and the pilot being used to detect the first UE;
means for determining, at the first UE, that the second UE will serve as a relay station between the base station and the first UE based at least in part on the pilot measurement, and the base station being unaware of the first UE prior to receiving the pilot measurement from the second UE; and
means for transmitting data, from the first UE to the second UE, for subsequent transmission to the base station.
6. The apparatus of claim 5 , wherein the means for determining comprises means for receiving, at the first UE, an indication that the second UE will serve as the relay station for the first UE.
7. A first user equipment (UE) for wireless communication, comprising:
at least one processor configured:
to transmit, to a second UE, a pilot indicating that the first UE outside a coverage area of a base station desires to communicate with the base station that currently serves the second UE, the pilot being used for at least a pilot measurement between the first UE and the second UE, and the pilot being used to detect the first UE;
to determine that the second UE will serve as a relay station between the base station and the first UE based at least in part on the pilot measurement, and the base station being unaware of the first UE prior to receiving the pilot measurement from the second UE, and
to transmit data, to the second UE, for subsequent transmission to the base station.
8. The first UE of claim 7 , wherein the at least one processor is further configured to determine based on a received indication that the second UE will serve as the relay station for the first UE.
9. A non-transitory computer-readable medium encoded with program code, the program code comprising:
code to transmit, from a first user equipment (UE) to a second UE, a pilot indicating that the first UE outside a coverage area of a base station desires to communicate with the base station that currently serves the second UE, the pilot being used for at least a pilot measurement between the first UE and the second UE, and the pilot being used to detect the first UE;
code to determine, at the first UE, that the second UE will serve as a relay station between the base station and the first UE based at least in part on the pilot measurement, and the base station being unaware of the first UE prior to receiving the pilot measurement from the second UE, and
code to transmit data, from the first UE to the second UE, for subsequent transmission to the base station.
10. A method for wireless communication, comprising:
receiving, at a second user equipment (UE) from a first UE, a pilot indicating that the first UE outside a coverage area of a base station desires to communicate with the base station that currently serves the second UE, the pilot being used for at least a pilot measurement between the first UE and the second UE, and the pilot being used to detect the first UE;
determining, at the second UE, that the second UE is selected to serve as a relay station between the base station and the first UE based at least in part on the pilot measurement, and the base station being unaware of the first UE prior to receiving the pilot measurement from the second UE; and
relaying, by the second UE, data from the first UE to the base station.
11. The method of claim 10 , wherein the determining comprises:
transmitting the pilot measurement to the base station, and
receiving, from the base station, an indication that the second UE is selected as the relay station.
12. The method of claim 10 , further comprising transmitting, to the first UE, an indication that the second UE is selected as the relay station.
13. The method of claim 10 , wherein the pilot is received on a low duty cycle.
14. An apparatus for wireless communication, comprising:
means for receiving, at a second user equipment (UE) from a first UE, a pilot indicating that the first UE outside a coverage area of a base station desires to communicate with the base station that currently serves the second UE, the pilot being used for at least a pilot measurement between the first UE and the second UE, and the pilot being used to detect the first UE;
means for determining, at the second UE, that the second UE is selected to serve as a relay station between the base station and the first UE based at least in part on the pilot measurement, and the base station being unaware of the first UE prior to receiving the pilot measurement from the second UE; and
means for relaying, by the second UE, data from the first UE to the base station.
15. The apparatus of claim 14 , wherein the means for determining comprises:
means for transmitting the pilot measurement to the base station, and
means for receiving, from the base station, an indication that the second UE is selected as the relay station.
16. A method for wireless communication, comprising:
receiving a pilot measurement for a pilot transmitted from a second user equipment (UE) to a first UE, the pilot indicating that the second UE outside a coverage area of a base station desires to communicate with the base station that currently serves the first UE, the base station being unaware of the second UE prior to receiving the pilot measurement, and the pilot being used to detect the second UE;
determining that the first UE is capable of serving as a relay station between the second UE and the base station based on pre-determined criteria;
selecting the first UE to serve as the relay station for the second UE based at least in part on the pilot measurement; and
controlling the first UE to support communication between the second UE and the base station.
17. The method of claim 16 , in which the pre-determined criteria comprises at least channel conditions between the first UE and the base station, a geographic location of the first UE, a geographic location of the second UE, a power supply level of the first UE, fairness considerations, or a combination thereof.
18. The method of claim 16 , further comprising transmitting an indication that the first UE is selected as the relay station for the second UE.
19. The method of claim 16 , further comprising:
transmitting data to the first UE so that the data is transmitted to the second UE.
20. An apparatus for wireless communication, comprising:
means for receiving a pilot measurement for a pilot transmitted from a second user equipment (UE) to a first UE, the pilot indicating that the second UE outside a coverage area of a base station desires to communicate with the base station that currently serves the first UE, the base station being unaware of the second UE prior to receiving the pilot measurement, and the pilot being used to detect the second UE;
means for determining that the first UE is capable of serving as a relay station between the second UE and the base station based on pre-determined criteria;
means for selecting the first UE to serve as the relay station for the second UE based at least in part on the pilot measurement; and
means for controlling the first UE to support communication between the second UE and the base station.
21. The apparatus of claim 20 ,
further comprising means for transmitting an indication that the first UE is selected as the relay station for the second UE.
22. The apparatus of claim 20 , further comprising:
means for transmitting data to the first UE so that the data is transmitted to the second UE.