Nyquist Bit Rate Formula Shannon Capacity Wave Forms Guided & Unguided Media Difference Between UTP and STP Different Modes of Fiber Time Division Multiplexing Frequency-Division Multiplexing PSTN & POTS ETC

1. 11.NyquistBit Rate Formula
In signal processing,the Nyquistrate,namedafterHarryNyquist,istwice the bandwidthof a
bandlimitedfunctionora bandlimitedchannel.Thistermmeanstwodifferentthingsundertwo
differentcircumstances:asalowerboundforthe sample rate for alias-freesignal sampling(nottobe
confusedwiththe Nyquistfrequency,whichishalf the samplingrate of a discrete-time system)andas
an upperboundforthe symbol rate across a bandwidth-limitedbasebandchannelsuchasa telegraph
lienorpassbandchannel suchasa limitedradiofrequencybandora frequencydivisionmultiplex
channel
C=12log2(1+PN) C=12log2(1+PN) bits per sample
12.Shannon Capacity
 The Shannonlimitiswhenall issaidindone exceptionallyhardtoascertain(Primakov etal.
2000). Truth be told,the Shannonlimitof the cycle diagramC_5 was notdecidedasTheta(C_5)
=sqrt (5) until 1979 (Lovász1979), and the Shannonlimitof C_7 is maybe a standoutamongst
the most infamousopenissuesin
extremal combinatorics(Bohman
2003).
 Lovász(1979) demonstratedthatthe
Shannonlimitof the (n,r)- Kinserchart
is(n-1; r-1),that of a vertex-transitive
self-reciprocal diagram(which
incorporatesall Paleycharts) Gis
sqrt(|V(G)|),andthatof the Petersen
chart is 4.
 All charts whose Shannonlimitisknownaccomplishtheirabilityeitheratk=1 (i.e.,attheir
autonomynumber;e.g.,consummate diagrams),k=2(e.g.,self-correlativevertex-transitive
charts includingthe Paleydiagrams),orelse don'tachieve itatany estimationof k(e.g.,the
diagramunionof the cycle chart C_5 witha singletondiagram) (Alonand Lubezki2006).

2. 13.Impairments of Signal
A transmission impairment is a property of a transmission medium which causes the signal to
be degraded, reduced in amplitude, distorted or contaminated. Impairment can introduce
errors into digital signals. Examples of transmission impairments are attenuation, delay
distortion, and several sources of noise including, interference, thermal noise, impulse noise,
and intermodulation noise.
1. Attenuation
 Attenuation is a property of the transmission medium. It measures how much
energy is absorbed and/or radiated from the traveling signal due to its
interaction with the transmission medium. Attenuation is measured as a
function of the distance traveled through the transmission medium. A wire or
cable may radiate energy when a signal travels through it. Energy is radiated at a
constant rate (much smaller rate if the cable is shielded) so the longer the
transmission medium the longer the signal is travelling through it and the more
attenuation occurs. When a signal is transmitted through the air the signal
travels in all directions (or some subset of directions with a well-designed
antenna).
2. Dispersion
 Dispersion is also a property of the transmission medium. Signals with different
frequencies will travel through a transmission medium with slightly different
velocities. Therefore, the signal will be smeared or distorted when it reaches the
destination.
3. Noise
 Noise of different types will affect a transmitting signal. Thermal noise, low
amplitude random noise at predictable low amplitude (amplitude related to the
temperature of the transmission medium), is caused by the thermal vibration of
the molecules within the transmission medium. The difference between signal
levels in a transmitted signal will generally be much larger than the amplitude of
the thermal noise. Thermal noise sets a limit of how close different signal levels
can be at the receiver (larger than the 2X amplitude of the thermal noise).
Thermal noise will not usually be of high enough amplitude to cause the
introduction of bit errors in an encoded signal (unless attenuation has been
excessive)

3. 14.Wave Forms
A waveform is the shape and form of a signal such as a wave moving in a physical medium or an
abstract representation. In many cases, the medium in which the wave propagates does not
permit a direct observation of the true form.
Examples
 Most programs show waveforms to give the user a visual aid of what has been recorded.
If the waveform is of low or high height (with respect to the {display style x} x axis), the
recording was most likely conducted under conditions with a low or high input volume,
respectively.
Sine Wave
 A sine wave or sinusoid is a mathematical curve that describes a smooth repetitive
oscillation. A sine wave is a continuous wave.
Square Wave
 Square waves are universally encountered in digital switching circuits and are naturally
generated by binary (two-level) logic devices. They are used as timing references or
"clock signals", because their fast transitions are suitable for triggering synchronous
logic circuits at precisely determined intervals.
Triangle Wave
 A triangle wave is a non-sinusoidal waveform named for its triangular shape. It is a
periodic, piecewise linear, continuous real function. Like a square wave, the triangle
wave contains only odd harmonics. However, the higher harmonics roll off much faster
than in a square wave (proportional to the inverse square of the harmonic number as
opposed to just the inverse).
SawtoothWave
 The sawtooth wave (or saw wave) is a kind of non-sinusoidal waveform. It is so named
based on its resemblance to the teeth of a plain-toothed saw with a zero rake angle.

4. 15.Encoding Digital Data to Digital Signals
 NRZ- It refers to a variety of digital information transmission within which the binary low
and high states, painted by numerals zero and one.
 NRZ-I- it's an information recording and transmission methodology that ensures clock
synchronization.
 Bipolar- Here, zero is painted by no signal line and one represent positive or negative
pulse.
 Pseudo ternary- A variation of Bipolar AMI is termed Pseudo ternary, here, one is
painted no line signal and zero is positive and negative.
 Manchester- it's a way of transmittal bits that permits the receiver to simply
synchronize with the sender. this is often a unique coding methodology from alternative
strategies.
 Differential Manchester- it's NRZ. It modifications its sign state only if there's a change in
information that differs from the previous bit.

5. 16.Digital to Analog
 Amplitude shift keying- it's a variety of AM that represents digital knowledge as
variations within the amplitude of a radio radiation. it's linear and sensitive.
 Frequency shift keying- Here, the modification in frequency outline in several digits.
The carrier is switched between two frequencies, 1 and 0.
 Phase Shift Keying- it's the digital modulation technique within which the part of the
carrier signal is modified by varied the circular function and cos inputs at a specific
time.
17.Analog to Analog
Analog-to-analog conversion, or analog modulation, is the representation of analog information
by an analog signal. Modulation is needed if the medium is bandpass in nature or if only a
bandpass channel is available to us.
There are three ways of modulation
1. Amplitude Modulation (AM)
2.Frequency Modulation (FM)
3.Phase Modulation (PM)

6. 1. Amplitude Modulation (AM)
 In AM transmission, the carrier
signal is modulated so that its
amplitude varies with the changing
amplitudes of the modulating signal.
The frequency and phase of the
carrier remain the same.
 The modulation creates a bandwidth
that is twice the bandwidth of the
modulating signal and covers a
range centered on the carrier
frequency.
 The bandwidth of an audio signal (speech and music) is usually 5 kHz. Therefore, an AM
radio station needs a bandwidth of 10kHz. In fact, the Federal Communications
Commission (FCC) allows 10 kHz for each AM station.
2. Frequency Modulation (FM)
 In FM transmission, the frequency of
the carrier signal is modulated to
follow the changing voltage level
(amplitude) of the modulating signal.
The peak amplitude and phase of the
carrier signal remain constant, but as
the amplitude of the information signal
changes, the frequency of the carrier
changes correspondingly.
 he actual bandwidth is difficult to
determine exactly, but it can be shown
empirically that it is several times that
of the analog signal or 2(1 β)B where β
is a factor depends on modulation
technique with a common value of 4.
 The bandwidth of an audio signal (speech and music) broadcast in stereo is almost 15
kHz. The FCC allows 200 kHz (0.2 MHz) for each station. This mean β = 4 with some extra
guard band.

7. 3.Phase Modulation (PM)
 PM transmission, the phase of the carrier
signal is modulated to follow the changing
voltage level (amplitude) of the
modulating signal. The peak amplitude
and frequency of the carrier signal remain
constant, but as the amplitude of the
information signal changes, the phase of
the carrier changes correspondingly.
 The actual bandwidth is difficult to
determine exactly, but it can be shown
empirically that it is several times that of the analog signal.
18.Difference BetweenPAM, PWM & PPM
PAM PWM PPM
Pulse amplitude is
variable
constant constant
Pulse width is
constant
variable constant
Bandwidth is less high high
Power of the
transmitter varies
Varies Remains constant
Noise interface is
high
minimum Minimum
Complex system Simpleto implement Simpleto implement

8. 19.Guided & Unguided Media
Telecommunication links can broadly be classed into two categories, namely, guided media
(wired) and unguided media(wireless).
Guided Media
 Electrical/Optical signals are passed
through a solid medium (different types
of cables/wires) As the path traversed
by the signals is guided by the size,
shape and length of the wire, this type
of media is called guided media.
 E.g., Copper Unshielded Twisted Pair
(UTP), Copper Shielded Twisted Pair (STP), Copper Co-axial cables, Fiber Optic Cables.
Unguided Media
 Here information is transmitted by sending electromagnetic signals through free space
and hence the name unguided
media, as the signals are not
guided in any specific direction
or inside any specific medium.
1.Distance separating the end
stations
2.Frequency spectrum used
by the electromagnetic signals
3.Line Encoding technique
used
 Based on these attributes, a
wide variety of wireless PHYs and different types of antennas are used in wireless
communication. The diagram given below illustrates different types of antennas
typically used in wireless communication As illustrated in the diagram, antennas can be
of many sizes and shapes.
 Wi-Fi, Wi-Max. 3G are example wireless networks used for internet communication.

9. 20.Difference BetweenUTP and STP
 Twisted pair cables are widely used in transmitting information, especially across great
distances. The twist in the wire cancels out any magnetic interference that may develop
in the wiring. There are two common types of twisted pair cabling, STP and UTP. The S
stands for Shielded, the U stands for Unshielded, and the TP stands for twisted pair for
both.
UTP STP
It doesn’t have a metal foil cover It does
Its less expensive thanSTP It is expensive thanUTP
Grounding isnot possible It is possible
Very Easy to install Easy to install
Segment length is 500m 100m
Very Easy Maintenance Easy Maintenance

10. 21.DifferentModes of Fiber
Fiber Optics is sending signals down hair-thin strands of
glass or plastic fiber. The light is "guided" down the
center of the fiber called the "core". The core is
surrounded by a optical material called the "cladding"
that traps the light in the core using an optical
technique called "total internal reflection."
1.Single Mode Cable
 Single Mode fiber optic cable has a small diametral core
that allows only one mode of light to propagate. Because of
this, the number of light reflections created as the light
passes through the core decreases, lowering attenuation
and creating the ability for the signal to travel further.
2.Multi Mode Cable
 Multimode fiber optic cable has
a large diametral core that
allows multiple modes of light
to propagate. Because of this,
the number of light reflections
created as the light passes
through the core increases,
creating the ability for more
data to pass through at a given
time. Because of the high dispersion and attenuation rate with this type of fiber, the
quality of the signal is reduced over long distances.
22.Time DivisionMultiplexing
Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals
over a common signal path by means of synchronized switches at each end of the transmission
line so that each signal appears on the line only a fraction of time in an alternating pattern.
History
 Time-division multiplexing was first developed for applications in telegraphy to
route multiple transmissions simultaneously over a single transmission line. In

11. the 1870s, Émile Baudot developed a time-multiplexing system of multiple
Hughes telegraph machines. In 1953 a 24-channel TDM was placed in
commercial operation by RCA Communications to send audio information
between RCA's facility on Broad Street, New York, their transmitting station at
Rocky Point and the receiving station at Riverhead, Long Island, New York.
Multiplexed Digital Transmission
 In circuit-switched networks, such as the public switched telephone network
(PSTN), it is desirable to transmit multiple subscriber calls over the same
transmission medium to effectively utilize the bandwidth of the medium. TDM
allows transmitting and receiving telephone switches to create channels
(tributaries) within a transmission stream. A standard DS0 voice signal has a data
bit rate of 64 kbit/s. A TDM circuit runs at a much higher signal bandwidth,
permitting the bandwidth to be divided into time frames (time slots) for each
voice signal which is multiplexed onto the line by the transmitter.
Statistical Time-Division Multiplexing
 Statistical time-division multiplexing (STDM) is an advanced version of TDM in
which both the address of the terminal and the data itself are transmitted
together for better routing. Using STDM allows bandwidth to be split over one
line.
Telecommunication Multiplexing
 There are three types of synchronous TDM: T1, SONET/SDH, and ISDN.
Plesiochronous digital hierarchy (PDH) was developed as a standard for
multiplexing higher order frames. PDH created larger numbers of channels by
multiplexing the standard Europeans 30 channel TDM frames.

12. 23.Frequency-DivisionMultiplexing
Frequency-division multiplexing (FDM) is a scheme in which numerous signals are combined for
transmission on a single communications line or channel. Each signal is assigned a different
frequency (subchannel) within the main channel. A typical analog Internet connection via a
twisted pair telephone line requires approximately three kilohertz (3 kHz) of bandwidth for
accurate and reliable data transfer. Twisted-pair lines are common in households and small
businesses. Suppose a long-distance cable is available with a bandwidth allotment of three
megahertz (3 MHz). When FDM is used in a communications network, each input signal is sent
and received at maximum speed at all times. This is its chief asset. However, if many signals
must be sent along a single long-distance line, the necessary bandwidth is large, and careful
engineering is required to ensure that the system will perform properly. In some systems, a
different scheme, known as time-division multiplexing, is used instead.

13. 24.PSTN & POTS
 PSTN
 PSTN (public switched telephone network) is the world's collection of
interconnected voice-
oriented public telephone
networks, both commercial
and government-owned. It's
also referred to as the Plain
Old Telephone Service
(POTS). It's the aggregation
of circuit-switching
telephone networks that has
evolved from the days of
Alexander Graham Bell
("Doctor Watson, come here!").
 POTS
 Plain Old Telephone Service or POTS is the name given to the telephone system
and service used during the late 19th century. It is a predecessor to more
advanced telephony technologies like Public Switched Telephone Network
(PSTN) and Integrated Services Digital Network (ISDN) that are used today. In this
article, we will have brief
look at the Plain Old
Telephone Service, its
general working including
advantages and
disadvantages of this
service. What is a Plain Old
Telephone Service? Now, if
there are more then one
Telephone User than we
need more lines. Moreover,
due to the analogue usage of communication in Plain Old Telephone Service
(POTS), Quality of Service (QoS) is poor. Although the equipment used in Plain
Old Telephone Service is simple and easy to design but the QoS and support for
number of subscriber in POTS makes it a poor choice for today’s system. Thats
why we moved to Public Swtiched Networks (PSTN ) and Integrated Services
Digital Network (ISDN).

14. 25. Wave DivisionMultiplexing (WDM)
 Wavelength-division multiplexing (WDM) is a method of combining multiple
signals on laser beams at various infared (IR) wavelengths for transmission along
fiber optic media. Each laser is modulated by an independent set of signals.
Wavelength-sensitive filters, the IR analog of visible-light color filters, are used at
the receiving end. WDM is similar to frequency-division multiplexing (FDM). In
early WDM systems, there were two IR channels per fiber. At the destination,
the IR channels were demultiplexed by a dichroic (two-wavelength) filter with a
cutoff wavelength approximately midway between the wavelengths of the two
channels. The use of WDM can multiply the effective bandwidth of a fiber optic
communications system by a large factor, but its cost must be weighed against
the alternative of using multiple fibers bundled into a cable. A fiber optic
repeater device called the erbium amplifier can make WDM a cost-effective
long-term solution.