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EEE6431 EEE6431 1 DEPARTMENT OF ELECTRONIC AND ELECTRICAL ENGINEERING Mock Graded Assessment 2020-21
EEE6431 Broadband Wireless Techniques Answer All parts of the question.
The numbers given after each section of a question indicate the percentage weighting of that section.
Q1 a. What is the optimum power adaptation policy to maximise the capacity of a discrete-time channel
that has stationary and ergodic time-varying channel power gains [] at discrete times . (15)
b. Consider a narrowband discrete-time channel with independent and identically distributed channel power gains [], = 1, 2, 3,
which can take on the 3 possible values: [1] = 0.2 with probability ! = 0.2; [2] = 1.5 with probability " = 0.5;
[3] = 0.9 with probability # = 0.3. If a transmitter and receiver have knowledge of the instantaneous values of [],
find the ergodic capacity of the channel when the average transmit power is 200 mW, the 1-sided noise
PSD is 10-9 W/Hz and the channel bandwidth is 20 MHz. (35) c. Compare your answer in Part 1(b) with: i.
The ergodic capacity when the channel power gains are only known at the receiver, and; ii.
The Shannon capacity of an SNR equivalent, additive white Gaussian noise (AWGN) channel. Comment on your answers. (30)
d. Calculate the optimal power allocations that achieve the ergodic capacity in Part 1(b). (20)