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Packet Transmission and Reception

We model packet transmission over the air-interface by a timer that keeps track of how long the radio transmission should take and signals when the transmission is over. The packet transmit timer (TxPktGprsTimer) is started at the begining of the appropriate slot by tx_onto_PHY(). On expiry of the transmit timer, the sendHandler() is called, which frees the packet, switches off the radio, and unlocks the IFQ.

If a MS or the BS senses a packet destined for it at the air-interface, it calls rx_from_PHY(). This starts a receive timer ( RxPktGprsTimer) to model the actual radio reception and also checks for collisions. On expiry of the receive timer, the recvHandler() is called, which checks whether the packet is in error or can be received, and sends it on to be processed by fwd_DATA_to_LL() and forwarded to the RLC.

Since we take propagation delay to be zero, the transmit and receive timers effectively start (and end) together.



Richa Jain (96D07007)
Tue Jul 24 22:29:53 IST 2001