(i) Create a MATLAB Simulink model to implement the following modulation system.

y(t) = (1+mx(t)) . cos(32000.pi.t)

where x(t) is the 10000 samples (starting from the last 3 digits of your student number) of signal speech available in your Wireless Communication Module content folder in NOW. Hint: after you read the required 10000 data samples, normalise it to between -1 and +1; i.e.

xn(t) <--- x(t)/max(abs(x(t))

and use the command resample in Matlab to downsample the signal to 8000 samples/sec.

Provide a graph of the down sampled signal segment you used, Simulink simulation schematic, and the output y(t) for m = 0.3 and 0.9. What type of modulation is this? (ii) Use random binary source generator (such as Bernoulli) in Simulink to replace (1 + m x(t)) in the above equation with a binary signal varying between 0 and 1. Provide the input signal, Simulink schematic and the output. Which type of modulation is this?

(iii) For x(t), original 10000 samples of speech, use (a) linear and (b) suitable mew-law nonlinear 4- bit quantizers and calculate to quantisation error for both quantizers. Explain the differences and show the quantised waveforms.