= OFDM Physical Layer =
We have chosen OFDM as the underlying physical layer for our research. Currently a SISO OFDM transceiver is fully implemented and tested in hardware. 

== OFDM Models Overview ==
Our SISO OFDM transceiver is implemented as two Simulink models built using Xilinx's System Generator for DSP. Both models are designed from scratch for real-time, wideband operation on the WARP hardware. The models have top-level interfaces to the WARP radio board's Tx/Rx analog converters. They also utilize an OPB interface for data exchange and control by the embedded PowerPC in the WARP FPGA. Both models are available in the [source:ResearchApps/PHY/SISO_OFDM repository].

== Features & Performance ==
Some basic performance paramters are listed below. This page will be updated as we further verify and extend the models in hardware.

'''Moduation:'''
  Both models support flexible modulation schemes, allowing individual subcarriers to carry [0, 1, 2, 4, 6, 8] bits. In other words, any combination of 0, BPSK, QPSK, 16/64/256 QAM can be used per packet. We have fully tested a QPSK-only system in hardware, loading 48 of 64 subcarriers with user data.

'''Bandwidth:'''
  The effective bandwidth is currently 10 MHz. The ADC/DAC sampling rate is actually 50 MHz; interpolation/decimation filters are included in the models to achieve this rate change.

'''Data rate:'''
  We have tested a 12 Mbps PHY configuration over-the-air (10 MHz bandwidth with 48 data-bearing subcarriers using QPSK modulation). We have also tested a 16 QAM system in hardware (running at 24 Mbps) and are in the process of fully verifying its operation now. 

'''Checksum calculation:'''
  Both the Tx and Rx models include hardware checksum calculation blocks. These blocks calculate a 32-bit CRC over each packet's payload in real-time. The Tx model appends the 4-byte checksum to each transmitted packet. The Rx model automatically notifies user code of a received packet's checksum status.