A communication device (1100, 1200) configured to operate in an acknowledged mode, AM, to transmit a data unit in a 3GPP based communication system, the communication device comprising: a transceiver (1113, 1213); at least one processor (1111, 1211); and at least one computer memory (1112, 1212) that is operably connectable to the at least one processor and that has stored thereon instructions which, when executed, cause the at least one processor to perform operations comprising: constructing M radio link control, RLC, protocol data units, PDUs, comprising M RLC service data units, SDUs, respectively, where M is larger than 1, wherein while constructing the M RLC PDUs, each RLC PDU is assigned a sequence number, SN, at the RLC layer equal to the SN of the corresponding RLC SDU, based on constructing the M RLC PDUs, submitting, to a medium access control, MAC, layer of the communication device and for a transmission opportunity, only L RLC PDUs, among the M RLC PDUs, corresponding to L RLC SDUs having the lowest L sequence numbers, SNs, among the M RLC SDUs, where the L RLC PDUs comprise a first RLC PDU having a poll to trigger status reporting at a receiving device; starting a poll retransmission timer based on submitting, to the MAC layer of the communication device, the first RLC PDU having the poll; controlling the transceiver to transmit the L RLC PDUs to the receiving device; based on (i) expiration of the poll retransmission timer, and (ii) a state in which no new RLC SDU can be transmitted due to window stalling: selecting, for retransmission, a second RLC SDU having the highest SN among the SNs of RLC SDUs contained in the L RLC PDUs submitted to the MAC layer, where L<M; constructing a second RLC PDU that comprises the second RLC SDU, based on selecting the second RLC SDU for retransmission; and controlling the transceiver to transmit the second RLC PDU comprising the second RLC SDU. a transceiver (1113, 1213); at least one processor (1111, 1211); and at least one computer memory (1112, 1212) that is operably connectable to the at least one processor and that has stored thereon instructions which, when executed, cause the at least one processor to perform operations comprising: constructing M radio link control, RLC, protocol data units, PDUs, comprising M RLC service data units, SDUs, respectively, where M is larger than 1, wherein while constructing the M RLC PDUs, each RLC PDU is assigned a sequence number, SN, at the RLC layer equal to the SN of the corresponding RLC SDU, based on constructing the M RLC PDUs, submitting, to a medium access control, MAC, layer of the communication device and for a transmission opportunity, only L RLC PDUs, among the M RLC PDUs, corresponding to L RLC SDUs having the lowest L sequence numbers, SNs, among the M RLC SDUs, where the L RLC PDUs comprise a first RLC PDU having a poll to trigger status reporting at a receiving device; starting a poll retransmission timer based on submitting, to the MAC layer of the communication device, the first RLC PDU having the poll; controlling the transceiver to transmit the L RLC PDUs to the receiving device; based on (i) expiration of the poll retransmission timer, and (ii) a state in which no new RLC SDU can be transmitted due to window stalling: selecting, for retransmission, a second RLC SDU having the highest SN among the SNs of RLC SDUs contained in the L RLC PDUs submitted to the MAC layer, where L<M; constructing a second RLC PDU that comprises the second RLC SDU, based on selecting the second RLC SDU for retransmission; and controlling the transceiver to transmit the second RLC PDU comprising the second RLC SDU. constructing M radio link control, RLC, protocol data units, PDUs, comprising M RLC service data units, SDUs, respectively, where M is larger than 1, wherein while constructing the M RLC PDUs, each RLC PDU is assigned a sequence number, SN, at the RLC layer equal to the SN of the corresponding RLC SDU, based on constructing the M RLC PDUs, submitting, to a medium access control, MAC, layer of the communication device and for a transmission opportunity, only L RLC PDUs, among the M RLC PDUs, corresponding to L RLC SDUs having the lowest L sequence numbers, SNs, among the M RLC SDUs, where the L RLC PDUs comprise a first RLC PDU having a poll to trigger status reporting at a receiving device; starting a poll retransmission timer based on submitting, to the MAC layer of the communication device, the first RLC PDU having the poll; controlling the transceiver to transmit the L RLC PDUs to the receiving device; based on (i) expiration of the poll retransmission timer, and (ii) a state in which no new RLC SDU can be transmitted due to window stalling: selecting, for retransmission, a second RLC SDU having the highest SN among the SNs of RLC SDUs contained in the L RLC PDUs submitted to the MAC layer, where L<M; constructing a second RLC PDU that comprises the second RLC SDU, based on selecting the second RLC SDU for retransmission; and controlling the transceiver to transmit the second RLC PDU comprising the second RLC SDU.