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## MULTIPLEXING TYPES

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**1. **MULTIPLEXING TYPES
Frequency Division Multiplexing
Time Division Multiplexing
Wavelength Division Multiplexing

**11. **PCM PROCESSES Filtering
Sampling
Quantization
Encoding
Line coding

**12. **SAMPLING

**13. **SAMPLING THEOREM “ If a band limited signal is sampled at regular intervals of time and at a rate equal to or more than twice the highest signal frequency in the band, then the sample contains all the information of the original signal”
Fs= >2fH

**14. **PULSE CODE MODULATION
Voice Frequency range 0- 4 Khz
Sampling the Voice Signal @ 8 Khz
(Double the Max. Frequency as per sampling theorem) i.e. 8000s/sec
Sampling time period Ts=1sec/8000
Ts= 125 microsec
Time available for sampling each channel, when we have N total channels=125/N
In PCM, Time frame=125microsec ;time available per chl=125/32 =3.9microsec.

**15. **QUANTIZING The process of measuring the numerical values of the samples and giving them a table value in a suitable scale
The finite number of amplitude intervals is called the ‘quantizing interval’ like quantizing interval no.1 is 10-20mV; 2 is 20-30mV etc. in a case of 1V signal.
Linear quantizing is where the quantizing intervals are of the same size

**16. **QUANTIZING LEVELS

**17. **QUANTIZING (one side)

**18. **QUANTIZING Quantization intervals are coded in binary form, and so the quantization intervals will be in powers of 2.
In PCM, 8 bit code is used and so we have 256 intervals for quantizing (128 levels in the positive direction and 128 levels in negative direction)

**19. **QUANTIZING (both sides)

**20. **QUANTIZATION DISTORTION The deviation between the amplitude of samples at the transmitter and receiving ends
In linear quantization, the distortion is more and to decrease the distortion, the no. of steps in the given amplitude range has to be increased.
Due to BW limitations, more quantum levels in small amplitude region are planned results to Non linear (uniform) quantization

**21. **COMPANDING Is the process where non uniform quantization is achieved using segmented quantization
In companding, to specify the location of sample value, the following are necessary…sign of the sample, the segment no., the quantum level within the segment.

**22. **SEGMENTATION

**23. **PCM ENCODING

**24. **FRAME STRUCTURE In PCM we have 32 Ts and Ts 0 (FAW) carries the synchronization signals and FAW digit value is X 0 0 1 1 0 1 1 . FAW transmitted in alternate frame. In FAW unused frames, supervisory and alarm signals are transmitted
Ts 16 carries the signalling information (for 2 channels)

**25. **FAW/ALARM DIGIT CODES

**26. **FRAME STRUCTURE For carrying the signalling for all 30 chls and for carrying sync. Data for all frames, in PCM 16 frame pattern is used and it is known as multi frame
Duration of multi frame is 2msecs.

**27. **PCM Standards THERE ARE TWO STANDARDS OF PCM NAMELY
1) THE EUROPEAN 2 ) THE AMERICAN.
THEY DIFFER SLIGHTLY IN THE DETAIL OF THEIR WORKING BUT THE PRINCIPLES ARE THE SAME.
EUROPEAN PCM = 30 CHANNELS
NORTH AMERICAN PCM = 24 CHANNELS
JAPANESE PCM = 24 CHANNELS
IN INDIA WE FOLLOW THE EUROPEAN PCM OF 30 CHANNELS SYSTEM WORKING.

**28. **EUROPEAN PDH HIERARCHY WITH BIT RATES

**29. **Dig. Hier based on 24chl PCM

**30. **MULTIPLEXING OF ASYNCHRONOUS SIGNAL in order to move multiple ASYNCHRONOUS 2 mbps data streams from one place to another, they are combined together or “multiplexed” in groups of four.
this is done by taking 1 bit/word from stream #1, followed by 1 bit/word from #2, then #3, then #4.
the transmitting multiplexer also adds additional bits in order to EQUAL or synchronise the bits in the multiplexer and the process adopted for such synchronization is called “justification” bits or
“ pulse stuffing ”

**31. **JUSTIFICATION TYPES Positive justification: Common synchronization bit rate offered at each tributary is higher than the bit rate of individual tributary.
Positive-negative justification
Negative justification

**32. **DIGITAL MUX CONCEPTS BYTE INTERLEAVING
WORD / BYTE / BLOCK INTERLEAVING:
IF THE CHANNEL TIME SLOT IS LONG ENOUGH TO ACCOMMODATE A GROUP OF BITS THEN THE MULTIPLEXED SIGNAL IS CALLED A “ BYTE INTERLEAVED OR WORD INTERLEAVED SIGNAL”.

**33. **DIGITAL MUX CONCEPTS BIT INTERLEAVING:
ALTERNATELY EACH CHANNEL CODE CAN BE SCANNED ONE DIGIT AT A TIME. THE MULTIPLEXED SIGNAL IS CALLED A “BIT INTERLEAVED SIGNAL”.
“BIT INTERLEAVING” IS USED IN HIGHER ORDER MULTIPLEXING.

**34. **Encoded FDM USA&canada

**35. **Encoded TDM Japanese

**36. **Dig Hier based on 30chl PCM-Encoded TDM European