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= 802.11 Reference Design: Channel Estimate Viewer = 

This example of the Experiments Framework translates OFDM Rx events from a node log to a MATLAB-compatible format, then displays the logged channel estimates in a MATLAB GUI.

This examples demonstrates how to:
 * Read raw log data from an HDF5 file
 * Process and filter the log data to construct an array of OFDM Rx events
 * Save the Rx events to a MATLAB-compatible HDF5 file
 * Load the Rx data into MATLAB
 * View the OFDM channel estimates in a MATLAB GUI

This example requires a log file that contains OFDM Rx events. You can generate your own log file (see the [wiki:../txrx_log Tx/Rx Log Example]) or use one of our [wiki:../ sample log files].

There are two steps for this example:
 * '''Python''': to convert raw log data to OFDM Rx data
 * '''MATLAB''': to read OFDM Rx data and display channel estimates

== Python ==

The first step is to use Python to create a MATLAB-compatible file of OFDM Rx events.

This process requires a raw log file from an 802.11 Reference Design node. You can generate your own log file, or use one of our sample log files. To use a sample log file you must first download the sample data files. Please refer to [wiki:../../sample_data the sample data] page of this guide for details.

The instructions below assume you are using the {{{raw_log_one_flow.hdf5}}} sample log file.

1. Open a terminal and CD to the {{{Python_Reference/examples/chan_est_viewer}}} directory in the expanded reference design archive
1. Run {{{python chan_ests_to_HDF5.py raw_log_one_flow.hdf5}}}

The {{{chan_ests_to_HDF5.py}}} script runs a simple processing flow:
 * Reads every OFDM Rx event from the log file
 * Counts the number of receptions from each unique MAC address
 * Identifies the MAC address with the most receptions
 * Creates a new NumPy array containing all the OFDM Rx events from that address
 * Saves this NumPy array to an HDF5 file

The script output will be similar to:
{{{
WLAN Exp Log Example: OFDM Rx Entry Exporter
Reading sample log file 'raw_log_one_flow.hdf5' (  5.0 MB)

Found 8519 receptions from fe:ff:ff:00:00:00
Genereating HDF5 file np_rx_ofdm_entries.hdf5
}}}

A new local file will be created named {{{np_rx_ofdm_entries.hdf5}}}. This is an HDF5 file suitable for import into MATLAB.

== MATLAB ==
The second phase of this example uses the HDF5 file containing OFDM Rx events which was generated by the Python script above. We have created a simple MATLAB GUI that reads this file, shows the list of OFDM Rx events and displays the OFDM channel estimates for selected packets.

To run the GUI:
1. Start MATLAB (tested with R2011b or later)
1. CD to the {{{Python_Reference/examples/chan_est_viewer}}} directory in the expanded reference design archive
1. Run the MATLAB script {{{ofdm_chan_est_viewer('np_rx_ofdm_entries.hdf5')}}}

This will read the data file {{{np_rx_ofdm_entries.hdf5}}} and display a GUI:

[[Image(chan_est_gui.png, width=800)]]

Click on any of the OFDM Rx events in the list to plot their channel estimate magnitudes and phase:

[[Image(chan_est_gui_sel.png, width=800)]]