A method for multiplexing data implemented by a wireless transmit/receive unit, WTRU, the method comprising: receiving a serving grant, wherein the serving grant is a grant for scheduled data transmission receiving at least one non-scheduled grant, wherein the non-scheduled grant is a grant for non-scheduled data transmission determining an available payload amount for a medium access control for enhanced uplink, MAC-e, protocol data unit, PDU, wherein the available payload amount is the smaller of: a maximum supported payload amount and a first amount of data, wherein the first amount of data is based on the serving grant and the at least one non-scheduled grant; and multiplexing bits from a medium access control for dedicated channel, MAC-d, flow into the MAC-e PDU; wherein the multiplexing is based on logical channel priority, wherein a higher priority logical channel is selected before a lower priority logical channel; wherein on a condition that the selected logical channel is associated with a non-scheduled MAC-d flow, the MAC-e PDU is filled with bits from the non-scheduled MAC-d flow up to the smaller of: an amount of data allowed by the non-scheduled grant for the non-scheduled MAC-d flow, an amount of data available for the selected logical channel, and the available payload amount; and wherein on a condition that the selected logical channel is associated with a scheduled MAC-d flow, the MAC-e PDU is filled with bits from the scheduled MAC-d flow up to the smaller of: an amount of data allowed by the serving grant, an amount of data available for the selected logical channel, and the available payload amount reduced by a quantization amount. receiving a serving grant, wherein the serving grant is a grant for scheduled data transmission receiving at least one non-scheduled grant, wherein the non-scheduled grant is a grant for non-scheduled data transmission determining an available payload amount for a medium access control for enhanced uplink, MAC-e, protocol data unit, PDU, wherein the available payload amount is the smaller of: a maximum supported payload amount and a first amount of data, wherein the first amount of data is based on the serving grant and the at least one non-scheduled grant; and multiplexing bits from a medium access control for dedicated channel, MAC-d, flow into the MAC-e PDU; wherein the multiplexing is based on logical channel priority, wherein a higher priority logical channel is selected before a lower priority logical channel; wherein on a condition that the selected logical channel is associated with a non-scheduled MAC-d flow, the MAC-e PDU is filled with bits from the non-scheduled MAC-d flow up to the smaller of: an amount of data allowed by the non-scheduled grant for the non-scheduled MAC-d flow, an amount of data available for the selected logical channel, and the available payload amount; and wherein on a condition that the selected logical channel is associated with a scheduled MAC-d flow, the MAC-e PDU is filled with bits from the scheduled MAC-d flow up to the smaller of: an amount of data allowed by the serving grant, an amount of data available for the selected logical channel, and the available payload amount reduced by a quantization amount. wherein the multiplexing is based on logical channel priority, wherein a higher priority logical channel is selected before a lower priority logical channel; wherein on a condition that the selected logical channel is associated with a non-scheduled MAC-d flow, the MAC-e PDU is filled with bits from the non-scheduled MAC-d flow up to the smaller of: an amount of data allowed by the non-scheduled grant for the non-scheduled MAC-d flow, an amount of data available for the selected logical channel, and the available payload amount; and wherein on a condition that the selected logical channel is associated with a scheduled MAC-d flow, the MAC-e PDU is filled with bits from the scheduled MAC-d flow up to the smaller of: an amount of data allowed by the serving grant, an amount of data available for the selected logical channel, and the available payload amount reduced by a quantization amount.