Tools4SDR : The "hello world !" of the communication with two USRPs, matlab and windows

Tutorial : Using the USRP with Matlab and Windows
1. Install the USRP (Windows) 2. USRP interface with Matlab and Windows 3. Test the installation of the Tools4SDR toolbox 4. The "hello world !" of the communication with two USRPs, matlab and windows

Tutorial : Transmission of a linearly modulated sequence of symbols

1. The "hello world !" of the communication with two USRPs, matlab and windows
2. Transmission of linearly modulation of sequences of QPSK and 16-QAM symbols. The received constellation.
3. Frequency offset estimation with linearly modulated sequence of symbols
4. Channel impulse response estimation with a linearly modulated sequence of symbols
5. Transmission of a binary signal with a linearly modulated sequence of symbols
6. Transmission of an image with the USRP (matlab/windows)

Discussion
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Structure of this article
1 Objectives of the scripts 2 Signal generation and transmission 3 Signal reception

More about GNU Radio & USRP >> USRP & Matlab
Test the installation of the Tools4SDR toolbox USRP interface with Matlab and Windows Estimation of the RF impairments of the USRP throught channel impulse response estimation Symbol rate estimation of linearly modulated sequence of symbols

See also
GNU Radio & USRP >> Generalities GNU Radio & USRP >> Tutorials GNU Radio & USRP >> USRP & Matlab GNU Radio & USRP >> SDR4All tools

The "hello world !" of the communication with two USRPs, matlab and windows

1. Objectives of the scripts

The objectives of the script is to transmit a simple signal from a PC connected to an USRP running Matlab (windows) to another PC connected to a second USRP running Matlab (windows).

The signal to transmit is a square signal of period T=3Te where Te is the sampling frequency (or the inverse of the transmitted signal bandwidth), and equals to 1us:

the received signal

2. Signal generation and transmission

The following commands have been used to generate the signal

y = kron(ones(100000,1),[ones(3,1);-ones(3,1)]);
t = (0:length(y)-1)*1e-6;

Then the USRP has been initialized:

USRP_Init();

And the signal has been transmitted. We use a bandwidth of 1MHz (second parameters) and the signal has been modulated around the frequency 2422MHz (3e WiFi channel)

USRP_SendSignal(y,1,2422e6);

This last command prints some information:

Preparing the signal for transmission
The transmission begins
The signal has been sent

The acquisition script on the second PC has to be launched after the transmission has began and should be over before the end of the transmission.

3. Signal reception

On the second PC that runs matlab, the following commands are used. The USRP is first initialized:

USRP_Init();

When the transmission begins on the first PC, the acquisition script is launch. It records a signal around the frequency 2422MHz over a bandwidth equal to 1 MHz:

[t,y] = USRP_ReceiveSignal(5,1,2422e6);

The signal is then plotted:

plot(t,real(y));

The received signal is composed of delayed bursts, each one being a replica of the transmitted signal. If you zoom on one of this burst, you should observe a signal like the following one:

the received signal

To go further and study the RF impairments of the USRP, you can estimate the channel impulse response of the channel when 2 USRPs are separated by a Gaussian channel.