Which of the following functions does the MAC sublayer mainly accomplish?

(2) Selecting the transmission format of the transmission channel according to the source rate, and improving the transmission efficiency of the transmission channel.

(3) Priority processing of a LIE data stream is achieved by mapping high priority and low priority data into a high rate and low rate transmission format, respectively.The multiplexing of dedicated channels can only be used for services with the same QoS parameters.

(4) measuring traffic on the logical channel and reporting to the RRC for determining whether to switch the transport channel type.

(5) Change the transport channel type according to the RRC indication.

(6) Encrypt real-time data transmitted in transparent RLC mode.