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QPSK Acoustic Software Radio. Orr Srour & Naftali Zon Under the supervision of Ami Wiesel. The problem. RF Communication systems, and especially MIMO communication systems are: expensive have long development time require wide technological knowledge. The need.
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QPSK Acoustic Software Radio Orr Srour & Naftali Zon Under the supervision of Ami Wiesel
The problem RF Communication systems, and especially MIMO communication systems are: • expensive • have long development time • require wide technological knowledge
The need • Besides their public use, in the academic world communication systems are needed for vary of reasons, for example – new algorithms testing. • In many cases, making a real communication system is simply unreasonable.
The goal • Real time communication system. • Rapid development • Easy to construct, manipulate and upgrade • Modular
The solution • Using ACOUSTIC waves instead of electromagnetic. • Fully software implemented - Simple ordinary computer is enough We will use the computer as our processing unit (we use Matlab-Simulink), and ordinary speakers and microphones as our antennas.
Systems overview - TOC • Simple SISO receiver/transmitter system • Virtually linked SIMO antenna selection • Fully SIMO system running the Alamouti space-time algorithm
System Parameters • We use QPSK modulation • Data frequency: 50 symbols/sec = 100 bit/sec • Carrier frequency: 800Hz
Training Sequence Data Sequence Communication Protocol • We send data in packets. • Each packet is constructed as follows: 13 symbols 50 symbols
Training Packets • The training sequence are constant predefined series of symbols. • They allow us to distinguish actual data packet from random noise. • They allow us to estimate the propagation channel and reconstruct the data.
Alamouti Transmit Diversity Technique • The Alamouti diversity technique allows us to send data from two antennas to one with the highest theoretical SNR possible, without the need of a delay system or pre-knowledge of the channel. • To do that, the transmission is done using 2 antennas as follows:
Alamouti Transmit Diversity Technique • Where S0 and S1 are two data symbols after QPSK modulation.
Alamouti Transmit Diversity Technique • In order to reconstruct the data, the following mathematical function is preformed: • Here h0 and h1 are the two channels propagation factors estimated by the detectors (see below)
“Down to Top” overview – our basic building blocks We will now introduce our basic building blocks, which will later be shown inside the different type of systems.
Packets Creator • This unit simply receives bits and returns them in packets according to the mentioned protocol.
M-PSK Modulator/Demodulator • These units transform between complex phase symbols and integer symbols
Raised Cosine Filter • This unit both upsamples and filters the input signal, using raised consine filter.
Amplification Vector Creator • When the bits of data are being transmitted, each bit has a unique amplification factor that determines its amplitude. • These bits are sorted in a vector created in the "Amplification Vector Creator unit".
Up Mixer / Down Mixer • The up-mixer block is in charge of shifting the incoming (complex) data into a real carrier signal. • The down-mixer has the opposite functionality. Amp
Squaring Timing Recovery • The Squaring Timing Recovery block is in charge of sampling the incoming signal at the right time. It uses the knowledge of the number of constant phase samples in the incoming signal.
The Estimator • The estimator block uses the predefined reference training signal in order to estimate the free-air channel propagation factor. • We assume here that the channel can be modeled by a complex number, representing the attenuation, delay and noise the signal has suffered, and that this complex number will not change within the transmission of one data packet.
The Estimator – cont’ • All this is done by correlating the incoming signal with the training sequence. • This block: • rises a trigger flag representing the reference signal has been discovered and is now over. • samples and holds the conjugate phase of the correlation result • samples and holds the amplitude of the correlation result.
The Detector • The detector block is in charge of canceling the free-air channel effect of the incoming data.
The Signal Output block • This block is in charge of sampling the actual data and regrouping the different packets into one long vector.
Antenna Selection Amplification For the antenna selection system only • This block is in charge of the creation of the amplification vector for the two antennas, in accordance to the "antenna selection" parameter received from the receiver.
EstimatorFor the antenna selection system only • This block uses two ordinary estimators blocks (mentioned in the SISO system), each for different reference sequence. • In addition to the ordinary estimator outputs, it also outputs the ID of the antenna which had the strongest signal in the receiver.
To AlamoutiFor the Alamouti system only • This block is in charge of transforming the input data into 2 antennas input data, transformed by the Alamouti Diversity Technique mentioned before.
Solve by AlamoutiFor the Alamouti system only • This block has the opposite functionality to the previous mentioned "To Alamouti" block. Its purpose is to demodulate the input signal using the Alamouti Diversity Technique.
Putting it all togetherTheSIMO Receiver Demonstration
Putting it all togetherTheAntenna Selection Demonstration
Putting it all togetherTheAlamouti Receiver Demonstration
Future Applications • short-range communication system on a single chip (using ultrasound waves) • submarine communication systems • implementation of MIMO sonar system
