Logical channel prioritization procedure for sidelink logical channels

1. A user equipment operable in a wireless communications system supporting direct communication between user equipments, comprising:

a storage including information indicative of one or more sidelink destination groups (ProSe destinations); and

circuitry, which is coupled to the storage and which, in operation:

selects a sidelink destination group associated with a sidelink logical channel having sidelink data available for transmission, the selected sidelink logical channel having a highest logical channel priority among sidelink logical channels having data available for transmission in a sidelink control period (SC period) and not previously selected in the same sidelink control period, wherein each of the sidelink logical channels belongs to a sidelink destination group, each of the sidelink logical channels is allocated to a logical channel group (LCG) depending on a priority of said each sidelink logical channel and on a priority of the logical channel group, and the logical channel group is defined per sidelink destination group; and

allocates radio resources to sidelink logical channels belonging to the selected sidelink destination group in decreasing priority order; and

a transmitter, which, in operation, transmits the sidelink data using the allocated radio resources.

2. The user equipment according to claim 1 , wherein the logical channel priority depends on at least one factor chosen from:

a destination group priority associated with a destination group of the sidelink data destination;

a logical channel group priority associated with a group of logical channels, grouped according to the type of data carried;

a geographical location of the user equipment;

an emergency level in which the user equipment is operating; and

a user equipment identifier.

3. The user equipment according to claim 1 , further comprising:

a receiver, which, in operation, receives an indication of the logical channel priorities for the respective logical channels determined by a ProSe (proximity services) function in a ProSe entity of the wireless communications system, and stores the logical priorities.

4. The user equipment according to claim 1 , wherein the circuitry, in operation, determines a logical channel priority for a logical channel.

5. The user equipment according to claim 1 , further comprising:

a buffer, which, in operation, stores data to be transmitted for a logical channel; wherein,

the circuitry, in operation, modifies a current priority for said logical channel into a modified priority either based on own recalculation of the priority or based on a command received from a ProSe function.

6. The user equipment according to claim 5 , wherein the data stored in the buffer before modification are either flushed or transmitted with the current priority depending on at least one factor chosen from:

a comparative determination of whether the current priority is higher than the modified priority;

the level of the modified priority; and

the cause of modification.

7. The user equipment according to claim 1 ,

wherein the circuitry, in operation:

determines that the user equipment is selected or not selected to transmit data among the user equipments of the wireless communications system;

responsive to determining that the user equipment is not selected, suspends sidelink logical channels associated with the user equipment and does not select or allocate resources to the suspended sidelink logical channels; and

responsive to determining that the user equipment is selected, resumes the sidelink logical channels which were previously suspended.

8. The user equipment according to claim 7 , wherein the circuitry, in operation:

determines that the user equipment is not to transmit data, according to messages exchanged in the wireless communications system between the user equipments and/or a proximity service entity in a layer above MAC (medium access control), and

responsive to determining that the user equipment is not to transmit data, stops transmission of own data and/or sidelink control information.

9. The user equipment according to claim 7 , wherein the circuitry, in operation:

extracts, from sidelink control information on physical layer or a MAC (medium access control) PDU (protocol data unit), received from another user equipment, a user equipment priority indicator;

compares the extracted user equipment priority indicator with an own user equipment priority stored in the user equipment or a priority of the data to be transmitted; and

when the own user equipment priority is lower than the extracted user equipment priority indicator, determines that the user equipment is not selected to transmit the data.

10. The user equipment according to claim 9 , wherein, when the user equipment has a floor and receives sidelink control information from another user equipment with a higher user equipment priority, the circuitry stops transmission of the data.

11. The user equipment according to claim 9 , wherein the user equipment priority indicator is carried within a MAC header of the MAC PDU and is configured by a ProSe (proximity services) entity of the wireless communications system.

12. The user equipment according to claim 1 ,

wherein the circuitry, in operation, reports to a network node of the wireless communications system the status of a buffer associated with the logical channel priority.

13. The user equipment according to claim 1 , wherein the circuitry, in operation, selects the radio resources to be allocated from a resource pool, and selects the resource pool among a plurality of resource pools according to the destination group priority or a logical channel priority associated with a logical channel from which the sidelink data is to be transmitted.

14. A network node operable in a wireless communications system supporting direct communication between user equipments, comprising:

a storage including information indicative of one or more sidelink destination groups (ProSe destinations); and

circuitry, which is coupled to the storage and which, in operation:

selects a sidelink destination group associated with a sidelink logical channel having sidelink data available for transmission, the selected sidelink logical channel having a highest logical channel priority among sidelink logical channels having data available for transmission in a sidelink control period (SC period) and not previously selected in the same sidelink control period, wherein each of the sidelink logical channels belongs to a sidelink destination group, each of the sidelink logical channels is allocated to a logical channel group (LCG) depending on a priority of said each sidelink logical channel and on a priority of the logical channel group, and the logical channel group is defined per sidelink destination group; and

allocates radio resources to a user equipment in the selected sidelink destination group among the user equipments.

15. A method to be performed at a user equipment operable in a wireless communications system supporting direct communication between user equipments, the method comprising:

storing information indicative of one or more sidelink destination groups (ProSe destinations);

selecting a sidelink destination group associated with a sidelink logical channel having sidelink data available for transmission, the selected sidelink logical channel having a highest logical channel priority among sidelink logical channels having data available for transmission in a sidelink control period (SC period) and not previously selected in the same sidelink control period, wherein each of the sidelink logical channels belongs to a sidelink destination group, each of the sidelink logical channels is allocated to a logical channel group (LCG) depending on a priority of said each sidelink logical channel and on a priority of the logical channel group, and the logical channel group is defined per sidelink destination group;

allocating radio resources to sidelink logical channels belonging to the selected sidelink destination group in decreasing priority order; and

transmitting the sidelink data using the allocated radio resources.