Tahmidmc.blogspot.com Website Review

This past semester (my last one during my undergrad years!), I was enrolled in ECE4670 -- Intro to Digital Communication with Professor Aaron Wagner. The final project required constructing the encoder and decoder (in Matlab) to send data over an existing channel (Cornell’s commcloud server). The project was done in groups of 2 and I had worked with my friend Balazs Szegletes. It was a fun learning experience, and I wanted to share the details of the project here! The communication channel is effectively a DAC that outputs the results of the encoder, X, a low-pas* filter, and then an ADC that samples this and sends data, Y, to the decoder. The means for sending data to the channel involves writing the data to a wav file, which is then pas*ed as an input parameter to a program called ccplay that is provided for the clas*. The program handles the DAC and ADC and saves the sampled output as another wav file. The goal is to be able to push data through the channel as quick as possible with few number of bit N is the number of bit errors Po is the average transmitted power The channel properties can be modeled by the Toeplitz matrix H, such that: Y = HX + Z, where Z is iid (independent, identically distributed) Gaussian noise. The commcloud server has two such channels, audio0 and channel. This scheme achieved a data rate of about 14,000 bits per second with zero errors, resulting in a figure of merit of about 14,000. The high performance design utilizes orthogonal frequency division multiplexing (OFDM) and quadrature amplitude modulation (QAM) to achieve a figure of merit much higher than the previous lab. The overall OFDM system block diagram is shown below (taken from Professor Wagner’s course’s Scribe notes The big gain in performance stems from the use of QAM, which allows encoding multiple bits per sample, in the complex plane. A modulation order (M) of 5 was selected for the design, ie 32-QAM. This was experimentally determined to be the optimal modulation order, which