Changes between Version 2 and Version 3 of OFDMReferenceDesign/Applications/CSMA


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Timestamp:
Dec 1, 2009, 1:11:49 PM (14 years ago)
Author:
murphpo
Comment:

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  • OFDMReferenceDesign/Applications/CSMA

    v2 v3  
    2121== Code ==
    2222The code for this application is provided in [source:/ResearchApps/MAC/CSMAMAC csmaMac.c]. The default OFDM Reference Design project includes CSMAMAC as a software project.
     23
     24== Protocol ==
     25This application uses our CSMA implementation. See the [wiki:CSMAMAC CSMAMAC] page for a full description of the state machine and overview of the code.
     26
     27== Timing ==
     28''The values below correspond to OFDM Reference Design v14''[[BR]]
     29
     30The basic packet exchange which defines the maximum throughput for CSMA is DATA-ACK-DATA. The timing of this exchange is our implementation is illustrated below. Please note the figure is ''not'' drawn to scale.
     31
     32[[Image(OFDMReferenceDesign/Applications/CSMA/Benchmarks/Files:csma_pktExchangeTiming.png)]]
     33
     34This figure assumes the following parameters:
     35 * SISO antenna configuration
     36 * 2 OFDM symbols for channel training per packet
     37 * 24 byte MAC header at QPSK (2 OFDM symbols)
     38 * Full rate modulation of QPSK (12 bytes per OFDM symbol) or 16-QAM (24 bytes per OFDM symbol)
     39 * 1484 byte payloads (1470 byte IP datagram + 14 byte Ethernet header)
     40
     41This figure includes a random backoff period imposed after a node receives an ACK. This period is designed to prevent two fully-backlogged nodes from simultaneously attempting to transmit a new packet immediately after the previous DATA-ACK exchange completes. The backoff imposes a wait of an integral number of slot durations (a slot is 22µs in v14), with the slot count drawn randomly from ![0,7].
     42
     43Given this timing, the average minimum period for transmitting a new DATA packet is 1263µs (for QPSK full rate) or 775µs (for 16-QAM full rate), implying a peak data throughput of 9.31Mbps for QPSK and 15.2Mbps for 16-QAM.
     44
     45== Benchmarks ==
     46Detailed [wiki:OFDMReferenceDesign/Applications/CSMA/Benchmarks/v14 benchmarks] are available for the latest (v14) reference design's CSMA implementation.