(bit/s)/Hz
Spectral efficiency is obtained by (maximum throughput achieved/bandwidth).
It is the amount of information that can be transmitted over a given bandwidth.
Sampling theorem:
If a signal is bandlimited from -B to B.
In order to completely construct the signal, the sampling frequency should be larger than 2B.
Motivation:
The impulse of delta trains with Ts in time domain (sampling) results in delta trains with Fs.
Ts is inversely proportional to Fs.
Thus, to avoid aliasing effect, Fs should be distant more than 2 [...]
Bit is a fundamental information unit to be transmitted.
Symbol is a unit of transmission energy, sinusoidal or wave transform.
M-ary waveforms: group of k bits sent per symbol M=2^k
For example, QPSK, 2 bits per symbol
bit rate = k*symbol rate= k/T where T is a symbol duration
Q: What is a matched filter?
Q: Why is matched filter also called correlator ?
A matched filter is used to detect the presence of some known signal.
Its impulse response is the timer reversed version of the template signal.
Basic fact: mathematical operation of a filter is convolution with its impulse response;
The output signal is obtained by convolving [...]
source coding:
reduce redundancy in source (e.g., zip file, H.264 video coding etc), digitalization of analog message signals and data compression
channel coding:
adding redundancy for reliable transimission (e.g., turbo coding, R-S coding etc.) forward error correction, bit interleaving
For high data rate, simply send fast.
Which one is high data rate ? 2 bits for 1 second vs. 2 bits for 6 seconds.
So, if you want a high data rate, your sending rate should be fast.
Time and frequency relationship is reverse. Short time duration means wide bandwidth.
That’s why wide bandwidth is need for faster [...]
