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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"><!--Converted with LaTeX2HTML 96.1 (Feb 5, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds --><HTML><HEAD><TITLE>Packet Transmission and Reception</TITLE><META NAME="description" CONTENT="Packet Transmission and Reception"><META NAME="keywords" CONTENT="gprs"><META NAME="resource-type" CONTENT="document"><META NAME="distribution" CONTENT="global"><LINK REL=STYLESHEET HREF="gprs.css"></HEAD><BODY LANG="EN"> <A NAME="tex2html185" HREF="node8.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="http://cbl.leeds.ac.uk/nikos/figs/next_motif.gif"></A> <A NAME="tex2html183" HREF="node3.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="http://cbl.leeds.ac.uk/nikos/figs/up_motif.gif"></A> <A NAME="tex2html177" HREF="node6.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="http://cbl.leeds.ac.uk/nikos/figs/previous_motif.gif"></A> <BR><B> Next:</B> <A NAME="tex2html186" HREF="node8.html">Call Set-up and Handling</A><B>Up:</B> <A NAME="tex2html184" HREF="node3.html">MAC Implementation Details</A><B> Previous:</B> <A NAME="tex2html178" HREF="node6.html">Timing Advance</A><BR> <P><H2><A NAME="SECTION00123000000000000000">Packet Transmission and Reception</A></H2><P>We model packet transmission over the air-interface by a timer that keepstrack of how long the radio transmission should take and signals when thetransmission is over. The packet transmit timer (<EM>TxPktGprsTimer</EM>) isstarted at the begining of the appropriate slot by <EM>tx_onto_PHY()</EM>.On expiry of the transmit timer, the <EM>sendHandler()</EM> is called, whichfrees the packet, switches off the radio, and unlocks the IFQ.<P>If a MS or the BS senses a packet destined for it at the air-interface, itcalls <EM>rx_from_PHY()</EM>. This starts a receive timer (<EM>RxPktGprsTimer</EM>) to model the actual radio reception and also checks forcollisions. On expiry of the receive timer, the <EM>recvHandler()</EM> iscalled, which checks whether the packet is in error or can be received,and sends it on to be processed by <EM>fwd_DATA_to_LL()</EM> and forwardedto the RLC.<P>Since we take propagation delay to be zero, the transmit and receivetimers effectively start (and end) together.<P><BR> <HR><P><ADDRESS><I>Richa Jain (96D07007) <BR>Tue Jul 24 22:29:53 IST 2001</I></ADDRESS></BODY></HTML>⌨️ 快捷键说明
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