Digital Communications
(UESTC 4004)
Lab 4: Project Demo and Evaluations
The objective of this lab is to design a digital communication system by yourself according to some requirements. After designing, you should evaluate its performance and think about how to improve it.
SCENARIO AND REQUIREMENTS
Imagine that you are in the main building of the university, and you need to transmit a picture over the air to your roommate in the dormitory. The picture can be your profile picture, your selfie, or any other picture that you like. The signal will pass through a channel with additive white Gaussian noise. To receive the image with a low bit error rate (BER), you need to design an orthogonal frequency-division multiplexing (OFDM) based communication system.
Design the system using appropriate modulation scheme and FFT size N to ensure the system supports at least 100 Mbps data rate. You have 10 MHz bandwidth available to you. Please consider using 12 subcarriers as pilots for channel estimation. Also, add a cyclic prefix of 0.4µsec with each OFDM symbol to suppress Inter Symbol Interference (ISI).
Perform. the tasks and report the findings as advised below:
1.1 Draw the block diagram representing all the blocks of your proposed system.
1.2 Show your OFDM system design calculations.
1.3 Display the original image and the received image.
1.4 Draw the BER curve for Eb/No from 0 to 20 dB.
We want to improve the bit error rate performance using an appropriate channel coding scheme. The channel coding can cost in terms of data rate drop and increased bandwidth requirement. Given that the data rate must not drop below 100 Mbps, we would need to increase the bandwidth to accommodate channel coding cost.
Suppose the maximum available bandwidth is 20 MHz, perform. the tasks and report your findings as mentioned below:
1.5 Propose a suitable channel coding scheme for this scenario.
1.6 Repeat Step 1.3 and 1.4 for your proposed encoded OFDM system.
1.7 Critically evaluate your design choices and their impact on system performance.
1.8 Give the code of your project.
Hint 1: You may use some key methods, including but not limited to, what you have learned from previous labs and lectures, such as modulation, and channel coding.
Hint 2: You may require the skills to deal with images. Feel free to use search engines for support.