A control circuit of a wireless user equipment includes: a PDCP layer computing circuit for reading a PDCP SDU from a PDCP SDU buffer of a memory device of the wireless user equipment, and for generating a ciphered data based on the PDCP SDU; a RLC layer computing circuit for generating a RLC PDU based on the ciphered data; a MAC layer computing circuit for generating a MAC PDU based on the RLC PDU; and a channel encoding circuit for encoding the MAC PDU. The PDCP layer computing circuit directly transmits the ciphered data to the RLC layer computing circuit, the RLC layer computing circuit directly transmits the RLC PDU to the MAC layer computing circuit, and the MAC layer computing circuit directly transmits the MAC PDU to the channel encoding circuit, without buffering above data in any buffering circuit outside the control circuit.