Methods and device for performing device-to-device communication
View Patent ↗Disclosed are methods for carrying out device-to-device (“D2D”) communication. In one implementation, a user equipment (“UE”) communicates D2D with another UE using uplink radio resources. The first UE receives a downlink signal from a base station and determines the reception time. The first UE also receives a timing advance for uplink communication. Based on the reception time and the timing advance, the first UE determines an uplink transmission time. When transmitting to the second UE, however, the first UE does not transmit at the determined UL transmission time. Rather, the first UE delays its D2D transmission for a period of time that is based on the second UE's uplink timing advance.
1. In a wireless network that includes a base station, a method for a first UE to perform device-to-device communication with a second UE, the method comprising:
receiving a downlink signal from the base station;
determining the reception time of the downlink signal;
receiving an indication of a timing advance for uplink communications from the first UE to the base station;
based on the determined downlink signal reception time and the indicated timing advance, determining an uplink transmission time for the first UE for uplink communications to the base station; and
delaying, by a period of time relative to the determined uplink transmission time, device-to-device transmissions to the second UE, wherein the period of time is calculated, in part, by adding the timing advance for uplink communications from the first UE to the base station and a timing advance applied by the second UE for uplink communications to the base station.
2. The method of claim 1 wherein the period of time is received from the base station.
3. The method of claim 1 wherein the period of time is further based on the propagation delay between the first UE and second UE.
4. The method of claim 3 further comprising:
detecting the second UE's reference signal; and
determining the propagation delay based on the detected reference signal.
5. The method of claim 1 :
wherein the period of time is
max
(
0
,
TA
Tx
+
TA
Rx
2
-
T
Prop
,
D
2
D
)
;
wherein TA Tx is the timing advance for the first UE;
wherein TA Rx is the timing advance for the second UE; and
wherein T Prop,D2D is a propagation delay between the first UE and second UE.
6. The method of claim 1 :
wherein the period of time is
max
(
0
,
TA
Tx
+
TA
Rx
2
-
T
Prop
,
D
2
D
+
T
Rx
_
switch
)
;
wherein TA Tx is the timing advance for the first UE;
wherein TA Rx is the timing advance for the second UE;
wherein T Prop,D2D is a propagation delay between the first UE and second UE; and
wherein T Rx _ switch is a receiver retuning time.
7. The method of claim 1 further comprising:
receiving information regarding the second UE's timing advance from the base station.
8. The method of claim 1 further comprising:
exchanging timing advance information with the second UE.
9. The method of claim 1 further comprising:
receiving an indication of a new timing advance from the base station; and
updating the second UE regarding the new timing advance.
10. In a wireless network that includes a base station, a method for a first UE to perform device-to-device communication with a second UE, the method comprising:
receiving a downlink signal from the base station;
determining the reception time of the downlink signal;
receiving an indication of a first timing advance for uplink communications from the first UE to the base station;
applying the first timing advance to perform uplink transmissions to the base station, wherein the first timing advance is relative to the determined downlink signal reception time; and
applying a second timing advance for reception of device-to-device communication from the second UE;
wherein the second timing advance is relative to the determined downlink signal reception time; and
wherein the second timing advance is calculated, in part, by adding the timing advance for uplink communications from the first UE to the base station and a third timing advance used by the second UE for uplink communications to the base station.
11. The method of claim 10 wherein the second timing advance is based on the propagation delay between the first UE and a second UE.
12. The method of claim 10 further comprising:
detecting the second UE's reference signal; and
determining a propagation delay between the first UE and the second UE based on the detected reference signal.
13. The method of claim 10 further comprising:
receiving information regarding the second UE's timing advance from the base station.
14. A UE configured to perform device-to-device communication with a second UE in a wireless network that includes a base station, the UE comprising:
a processor;
an antenna; and
a transceiver configured to:
receive downlink signals from the base station via the antenna, wherein at least one of the downlink signals includes data indicating a timing advance for uplink communications from the first UE to the base station; and
provide the timing advance data to the processor;
wherein the processor is configured to:
determine the reception time of one or more of the downlink signals;
receive the timing advance data from the transceiver;
based on the determined downlink signal reception time and the indicated timing advance, determine an uplink transmission time for the first UE for uplink communications to the base station; and
delay, by a period of time relative to the determined uplink transmission time, device-to-device transmissions to the second UE, wherein the period of time is calculated, in part, by adding the timing advance for uplink communications from the first UE to the base station and a timing advance applied by the second UE for uplink communications to the base station.