For ns-2.1b7a1. The MAC implementation is more or less complete. It can be usedwith the default ns-mobilenode structure (ie with no RLC and defaultns-LL). It can be used for GPRS/GSM simulations. The only difference would bethat in GPRS, radio resources (slots) are released if left idle for awhile; whereas in GSM, the MS holds on to resources even during idle periodsof a call .When using this MAC with the default ns-mobilenode structure, a hackcan be made for the missing RLC. Limit the packet size for the TCPsource/sink to 50 bytes. Thus the MAC will receive and transmit onlyPDUs of 50 bytes per slot. 2. Work on the LL and RLC is still underway. The current code supportsacked mode and fragmentation/reassembly for only one traffic flow ieonly between one MS-BS pair. This is due to the nature of the variablesused to keep track of the sequencing of fragments. Will be correctedin a while.Out of sequence packets are stored till the appropriate order isachieved. A duplicate ack sent to indicate a missing packet in RLC acked mode. 3. The sample script here is for the modified mobilenode structure -iewith and RLC with 1 MS-BS pair. LL is used in unacked mode and RLC inacked mode along with a slot level error model. The trace file isgprs_err_acked.tr with the verbose MAC output in err_acked and theverbose RLC output in err_acked_rlc.Running the same script without the error model gives results as shownin gprs_acked.tr (trace file), acked (verbose MAC output), acked_rlc(verbose RLC output).For unacked mode, the results are shown inin gprs_unacked.tr (trace file), unacked (verbose MAC output), unacked_rlc(verbose RLC output).4. The MAC can be used to compare allocation mechanisms; study GSM vsGPRS system capacity; the effect of load on performance parameters;interaction of the ack mechanisms at the TCP-LL-RLC layers etc.5. Various other MAC algos were tried out and code is TDMA with uplink-downlink slots in a single frame ie half slots in a frame reserved for up-link and half-for downlink. TDMA with seperate uplink/downlink frames; simple; single channel; no signalling; slot_allotment according to mac-index.