Changes between Version 3 and Version 4 of WARPLab/Examples/MIMO_OFDM

Timestamp:

Aug 25, 2015, 4:02:46 PM (9 years ago)

Author:

chunter

Comment:

--

WARPLab/Examples/MIMO_OFDM

@@ -3 +3 @@
 File: [source:/ResearchApps/PHY/WARPLAB/WARPLab7/M_Code_Examples/wl_example_mimo_ofdm_txrx.m wl_example_mimo_ofdm_txrx.m] 
 
-This WARPLab example implements a simple 2x2 MIMO OFDM transmitter and receiver. The script can run with or without WARP hardware in the loop and does not require any extra MATLAB toolboxes.
+This WARPLab example implements a simple 2x2 MIMO OFDM transmitter and receiver. The script can run with or without WARP hardware in the loop and does not require any extra MATLAB toolboxes. This example extends the [wiki:WARPLab/Examples/OFDM SISO OFDM example]. Users are encouraged to read and test that example before moving on to this MIMO variant.
 
-This example extends the [wiki:WARPLab/Examples/OFDM SISO OFDM example]. Users are encouraged to read and test that example before moving on to this MIMO variant.
+There are many different techniques that full under the term "MIMO." This specific example implements a specific type of MIMO known as spatial multiplexing. We use 2 antennas at a transmitter to send two independent spatial "streams" of data at the same time and in the same frequency band. We then use 2 antennas at the receiver to disentangle the two spatial streams.
+
+[[Image(mimo_ofdm_preamble.png, width=800)]]
+
+To accomplish this, explicit MIMO channel training must be added to the preamble of the transmission. The above figure demonstrates the structure of the waveform that is transmitted in the example. The preamble begins with a "legacy" portion that is predominantly SISO. The 2nd antenna does transmit during the first burst of Short Training Symbols (STS) in order to ensure that proper gains are selected at the receive node radio interfaces. To avoid accidentally beamforming the transmission to an arbitrary direction, the STS symbols transmitted from the 2nd antenna are cyclically shifted by a user-changeable number of samples.
+
+From there, the rest of the legacy preamble is identical to that seen in the [wiki:WARPLab/Examples/OFDM SISO OFDM example]. These Long Training Symbols (LTS) are used by the receiver to estimate and correct for Carrier Frequency Offset (CFO) as well as timing alignment via a cross correlator.
+
 
 == Running the Example ==