User equipment, a network node and methods therein for performing and enabling device-to-device (d2d) communication in a radio communications network

Abstract

A user equipment, a network node and method therein for enabling D2D communications between user equipments in a radio communications network are also provided.

1 . A method performed by a first user equipment for performing a Device-to-Device, D2D, communication with a second user equipment, wherein the first user equipment does not have a valid timing reference because it is in an idle mode, in which idle mode the first user equipment is not connected to a cell in a radio communications network, the method comprising:
 obtaining a preconfigured timing advance value for the D2D communication; and   transmitting a D2D signal to the second user equipment with a timing using the preconfigured timing advance value in the D2D communication.   
     
     
         2 . The method according to  claim 1 , wherein the obtaining further comprises determining that the preconfigured timing advance value can be used when received signal strength measurements in the first user equipment are above a threshold. 
     
     
         3 . The method according to  claim 1 , wherein the obtaining of the preconfigured timing advance value is based on information received in a broadcast message from a network node. 
     
     
         4 . The method according to  claim 3 , wherein the obtaining further comprises determining that the preconfigured timing advance value can be used when received signal strength measurements in the first user equipment are above a threshold. 
     
     
         5 . The method according to  claim 3 , wherein the information comprises one or more of:
 a list indicating in which cells the preconfigured timing advance value is used;   a cell size;   an Information Element, IE, indicating whether the preconfigured timing advance value is used;   a subframe format allocated to a D2D communication indicating that an extended cyclic prefix is used; and   the preconfigured timing advance value.   
     
     
         6 . The method according to  claim 5 , wherein the obtaining further comprises determining that the preconfigured timing advance value can be used when received signal strength measurements in the first user equipment are above a threshold. 
     
     
         7 . The method according to  claim 1 , wherein the transmitting is performed on a channel for D2D operation. 
     
     
         8 . A first user equipment for performing Device-to-Device, D2D, communications with a second user equipment, wherein the first user equipment does not have a valid timing reference because it is in an idle mode, in which idle mode the first user equipment is not connected to a cell in a radio communications network and wherein the first user equipment is configured to:
 obtain a preconfigured timing advance value for the D2D communication; and   transmit a D2D signal to the second user equipment with a timing using the preconfigured timing advance value to perform the D2D communication.   
     
     
         9 . The first user equipment according to  claim 8 , further configured to transmit the D2D signal to the second user equipment with a timing using the preconfigured timing advance value in order to perform the D2D communication on a channel for D2D operation. 
     
     
         10 . The first user equipment according to  claim 8 , further configured to determine that the preconfigured timing advance value can be used when received signal strength measurements in the first user equipment are above a threshold. 
     
     
         11 . The first user equipment according to  claim 10 , further configured to transmit the D2D signal to the second user equipment with a timing using the preconfigured timing advance value in order to perform the D2D communication on a channel for D2D operation. 
     
     
         12 . The first user equipment according to  claim 8 , further configured to base the obtained preconfigured timing advance value on information received in a broadcast message from a network node. 
     
     
         13 . The first user equipment according to  claim 12  further configured to transmit the D2D signal to the second user equipment with a timing using the preconfigured timing advance value in order to perform the D2D communication on a channel for D2D operation. 
     
     
         14 . The first user equipment according to  claim 12 , further configured to determine that the preconfigured timing advance value can be used when received signal strength measurements in the first user equipment are above a threshold. 
     
     
         15 . The first user equipment according to  claim 14 , further configured to transmit the D2D signal to the second user equipment with a timing using the preconfigured timing advance value in order to perform the D2D communication on a channel for D2D operation. 
     
     
         16 . The first user equipment according to  claim 12 , wherein the information comprises one or more of:
 a list indicating in which cells the preconfigured timing advance value is used;   a cell size;   an Information Element, IE, indicating whether the preconfigured timing advance value is used;   a subframe format allocated to a D2D communication indicating that an extended cyclic prefix is used; and   the preconfigured timing advance value.   
     
     
         17 . The first user equipment according to  claim 16 , further configured to transmit the D2D signal to the second user equipment with a timing using the preconfigured timing advance value in order to perform the D2D communication on a channel for D2D operation. 
     
     
         18 . The first user equipment according to  claim 16 , further configured to determine that the preconfigured timing advance value can be used when received signal strength measurements in the first user equipment are above a threshold. 
     
     
         19 . The first user equipment according to  claim 18 , further configured to transmit the D2D signal to the second user equipment with a timing using the preconfigured timing advance value in order to perform the D2D communication on a channel for D2D operation.