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QPSK & QAM Decoding In Simulink

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Junior Member level 3
Apr 27, 2008
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Hi there,

I need to design a QPSK and QAM receiver in Simulink based on the provided transmitter design. It is meant to simulate transmission of data through a wireless channel. In this case an image is the data to be transmitted and my receiver has to receive the data with the highest possible efficiency. This is done by comparing the sent and received data with respect to time. I have attached the related transmitter implementation/ the m file used to convert the image into the relevant data format and also my attempt at designing the QPSK receiver. The specifications i have been given are as follows:

Study the example design of a QPSK transmitter implemented in MATLAB and SIMULINK and then complete the communication system with your own
receiver implementation. Based on your working QPSK system, design and implement a working QAM system operating at the same data rate achieving the highest possible spectral efficiency. The two completed systems should demonstrate the ability to transmit files correctly, i.e., the file produced by your
receiver should be the same as the original file read by the transmitter. Your systems will be tested using the test image file “test.jpg” under fixed ratio of bit energy to noise power spectral density (Eb/N0) that was defined by the “AWGN channel” block in the example design.

I have attempted to design my QPSK receiver using information gathered from books etc but my output seems to be a whole bunch of random binary numbers and there is no timing associated with it when compared to the transmitter. I would really appreciate it if someone could have a look at the file and tell me where I have gone wrong, suggest a solution for the problem as well as giving me an idea of how to implement the QAM receiver (ie. the difference between the two receivers etc). Thanks and please feel free to ask any questions if anything is unclear.

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