time connections requiring a short transmission delay and the second one to cater for non realtime connections having a higher tolerance for transmission delay the rt mode employs power control and link adaptation mechanisms the nrt mode uses power control and retransmission procedures in the rt mode the source rlc is in charge of splitting the llc flow to the traffic channels tchs allocated to the radio bearer the rlc deals with link adaptation and therefore signals resource change requests to macs in order to adapt to traffic or radio link quality variations the transmission format channel coding interleaving and modulation for the bearer is selected from among a limited set of options the actual coding rate can however be adjusted separately for each tch the rlc segments the llc data into rlc pdus in accordance with the transmission format optionally computes a crc cyclic redundancy code and then delivers the pdu to the physical layer for transmission the receiving rlc checks the crc if there is one and signals the crc check result to the mac the rlc assembles the pdus received and delivers the resulting sdu to the llc in the nrt mode the source rlc indicates the size of the data to be transmitted to the mac layer the transmission format to be used is agreed on at the bearer set up the rlc deduces from this format the adapted segmentation and delivers protocol data units pdu to layer 1 when requested by the mac i e when resources are allocated to the radio bearer by the network the sink rlc checks the crc and alerts the mac when a corrupted pdu is received it assembles the correct pdus and delivers sdu to llc one mac entity per mobile manages all the radio bearers established by the.