按课件顺序整理的历年题的考点，需要拿着课件看。
Question1:
解释为什么要按Nyquist滤波 Using diagram to explain general sampling…
求bit rate, sample rate(用Nyquist), baud (symbol) rate.
【注】
题目说了binary coded, binary signaling is used: bit rate=baud (symbol) rate, 即R=D,此时minimum bandwidth=D/2; 题目中提到3 bit to each symbol, Multilevel coded, level, 并且没说binary coded: bit rate=(symbol rate)*(bits/symbol).
这两种情况，minimum bandwidth for channel=D/2!!! 这个求的是channel bandwidth, 题目给的一般都是signal bandwidth.
SQNR, Shannon’s formula-Channel capacity-> SNR: 三个概念以及公式
SQNR: （week 1 P60）
C=Wlog(1+SNR), SNR还有很多种表达->>>spectral efficiency->>>Eb/N0
Question 1 b):
Information content；Entropy (H) ；Maximum entropy:
Information content不用乘概率p；除此之外这三个公式都一样，是log2哦。
Coding efficiency, Source efficiency: 区别：前者分母是bits required, 后者分母是maximum entropy. 两者分子都是entropy.
Huffman coding 会画
H(X|Y); I(X;Y) ; I(X;Y)max=channel capacity!!!
Question 2:
Linear block code
【一道怪怪的题】(15/16 Question 2)
A digital information source produces binary sequences at a rate of 5 kbps.
Based on the parity check matrix H, determine the length of the input information sequences and the length of the code words. Calculate the code rate of this Hamming code and the resulting transmission rate.
这里，注意code rate =k/n; transmission rate*code rate=5kbps 记住就好
另外，week 1 老师补充的课件里有说 transmission rate=baud(symbol) rate，真是复杂
Question 3,4:
Power spectral density(PSD): 应该只考Unipolar NRZ, polar NRZ 推导
Slow/fast FHSS using MFSK画图，一个一个小格子：
PN sequence决定symbol在哪个信道->Tc; period的PN sequence可以数出来
Symbol rate-> Ts; 每个symbol有k bits,分布在2^k个不同的frequency.
Tc < Ts: Fast Tc > Ts: Slow
ISI
各种画图解释ISI传输
EX1: (Sample paper 14/15)Using diagrams to explain the Intersymbol interference in a baseband pulse-transmission system by sketching an ideal input waveforms of 1000 and sampling points of 1011 at transmitter and its individual pulse response and sum of pulse responses at the receiver.
EX2: （15/16 paper B）Using diagrams to illustrate ideal filtering, filtering with ISI and noise plus ISI polar NRZ waveforms and corresponding eye patterns.
两个消除ISI的方法List two methods to improve the inter-symbol interference (ISI):
increase bandwidth
reshape the pulse from transmitter.
OFDM
画图解释OFDM modulate & demodulate (week 4 P61-64)
画图解释single carrier, multi carrier, OFDM.（week 4 P51,52)
Week 4 后面的一些概念，公式：
Antenna gain
Thermal Noise->>>Eb/N0:
Thermal noise density: N0=KT Thermal noise in watt: N=KTB (B is bandwidth)
频率复用frequency reuse:
两个cluster的距离：Ru=r √3N
Bigger cluster的后果：less interference and lower capacity for each cluster.
历年题只考了3-cell cluster 和 7-cell cluster received power 作比较，算reduced capacity in dB.
最后，考试别忘带计算器和直尺。一个是算log2要用，一个是画图要用。
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