1. A method for triggering a Buffer Status Reporting (BSR), the method comprising:determining, by a user equipment, the size of padding resources when the user equipment composes a D2N MAC PDU, wherein the D2N MAC PDU is a device to network media access control protocol data unit; and
deciding, by the user equipment, whether to trigger a D2D padding BSR, according to the size of the padding resources, and the priority of D2D padding BSR MAC CE, wherein the D2D padding BSR MAC CE is a media access control layer control element for carrying a device to device communication padding buffer status reporting, and the D2D padding BSR is a device to device communication padding buffer status reporting;
wherein determining the size of the padding resources comprises:
subtracting resources from uplink resources of the user equipment in a sub-frame where the D2N MAC PDU is located, wherein the resources include:
resources occupied by an D2N MAC CE other than D2N MAC CE for carrying a D2N padding BSR, wherein the occupied resources comprise resources occupied by a first MAC sub-header and a first payload;
resources occupied by logical channel data over a D2N link other than an Uplink Common Control Channel (UL-CCCH), wherein the occupied resources comprise resources occupied by a second MAC sub-header and a second payload; and
resources occupied by an D2D MAC CE other than D2D MAC CE for carrying a D2D padding BSR, wherein the occupied resources comprise resources occupied by a third MAC sub-header and a third payload.