= OFDM Reference Design v14 - CSMA Benchmarks =


== Timing ==
The 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.

[[Image(OFDMReferenceDesign/Applications/CSMA/Benchmarks/Files:csma_pktExchangeTiming.png)]]

This figure assumes the following parameters:
 * SISO antenna configuration
 * 2 OFDM symbols for channel training per packet
 * 24 byte MAC header at QPSK (2 OFDM symbols)
 * Full rate modulation of QPSK (12 bytes per OFDM symbol) or 16-QAM (24 bytes per OFDM symbol)
 * 1484 byte payloads (1470 byte IP datagram + 14 byte Ethernet header)

This 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].

Given 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.

== Performance Tests ==

=== Peak Throughput ===

'''Methodology''': two WARP Kits (SISO Kit v1), with radios connected via a cable and 60dB attenuation, FPGA boards each connected via Ethernet to a MacBook laptop. One MacBook runs an iperf server, the other runs the iperf client, using one of the following calls:
{{{
#!sh
#For UDP tests:
iperf -c 10.0.0.1 -u -b 20M -l 1470 -t 30

#For TCP tests:
iperf -c 10.0.0.1 -l 1470 -t 30
}}}

'''Results:'''
|| Full Rate || TCP || UDP ||
|| QPSK || XX || XX ||
|| 16-QAM || XX || XX ||

== Packet Error Rate ==

== Bit Error Rate ==