basics of data communication,
TRANSCRIPT
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1. DATA COMMUNICATION NETWORKS1.1. INTRODUCTIONElectronic communications consist of telecommunication and data communication.
Telecommunication consists of telephone, teletype-writing, telegraph and radio or televisionfacilities to transmit information either directly or via-computer. Data communication is the
transfer of data or information between computer devices.
1.2. DATA COMMUNICATION: It refers to the exchange of data (represented as a bit pattern ora sequence of bits) between two devices via some transmission medium such as a wire
cable. The data communication system consists of five main components:
1.2.1. Message: It is the data or information to be communicated.1.2.2. Sender: It refers to the device which transmits or sends the data message.1.2.3. Receiver: It is the device that receives the message.1.2.4. Transmission medium: It is the medium or path through which the message
travels from sender to receiver.
1.2.5. Protocol: These are the set of rules that has to be followed while transmission ofdata and these rules governs data communication.
1.2.6. Network: It is a set of devices (or nodes) connected by communication links. Anode can be a computer, printer or any other device capable of sending or
receiving data generated by other nodes on the network.
The effectiveness of the data communication system depends on four factors:
1.2.7. Delivery: The system should deliver the data to the correct destination and datamust be received by the receiving device.
1.2.8. Accuracy: The data delivered at the destination must be accurate. Data should notbe altered in transmission and left uncorrected.
1.2.9. Timeliness: The system must be capable of delivering the data message in time.Data delivered late in case of real time application like video streaming, are
useless.
1.2.10. Jitter: It is the variation in the packet arrival time. It is the uneven delay in thedelivery of audio or video packets.
1.3. BASIC TERMINOLOGIES USED IN DATA COMMUNICATION:1.3.1. BAUD RATE: The rate at which the data transfers over the communication is called
communication rate or data rate. Baud is the number of signal level changes per
second in the signal line.
1.3.2. Bits Per Second (BPS): It is the rate of transfer of information bits. The ratio of BPSto baud rate entirely depends on the information coding scheme used.
1.3.3. Hartley-Shannon Theorem: It states that the maximum rate at which the data canbe transmitted error-free over a communication channel is the Channel Capacity,
which is given by,
C= B log2 (1+ (S/N))
Where B is bandwidth (in hertz), S/N is signal to noise ratio (in decibels) and C is the channel
capacity measured in bits/second.
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1.3.4. Parallel Interface: Interfaces are used to transfer data from one place to another.In parallel interface, 8 wires are used to transmit a byte (8 bits) of data. It is very
expensive and very fast as compared to serial interfaces. It is basically a
simultaneous transmission of data. It is used to transfer data on same sites i.e.
between one printer and one computer.
1.3.5. Serial Interface: It is a sequential transmission of data of eight bits of a data. Atransmitter breaks each byte into eight bits and sends it one by one sequentially;
the receiver reassembles all the eight bits into a single byte. It is slower than the
parallel since, each bit is transmitted one by one. It is used when data is
transferred between two computers.
1.4. Data Transmission techniques: For the communication between computers and line, thedigital data need to be converted into analog signal. The data at transmitter is converted
into analog, by modulation technique and similarly at receiver the data is again converted
into digital using demodulation technique. This is done by using MODEM at both the ends.1.5. Data Transmission methods: Data transmissions methods are divided into three
categories.
1.5.1. Synchronous Transmission: Synchronous is the method in which the data istransmitted in clock cycles. Each block of characters is marked with a
synchronisation character. The receiver will receive the data until the synchronous
character is detected. Timing errors are reduced and it can perform error detection
so that cyclic redundancy checks are performed on the data on both the sides.
(image)
1.5.2. Asynchronous Transmission: It is the method of transmission in which onecharacter is transmitted at a time. Each character is encapsulated with start and
stop bits which indicates the beginning and end of a data stream. A telephone
conversation is asynchronous because each party can talk whenever they like. If, it
would have been synchronous then one party has to wait for a period of time
before speaking again. (image)
1.5.3. Isochronous Transmission: Isochronous means basically time dependent. In this,the data is transferred within certain time frame. For example: ATM networks are
said to be isochronous because they guarantee a specified throughput. Even the
oscillations are produced by pendulum.
1.6. DATA TRANSMISSION MODES:
1.6.1. Simplex mode: In this mode of transmission, data is transferred in only onedirection. In this mode, a device can either send or receive data. For example: TVs
and radios.
1.6.2. Half Duplex mode: In this mode of transmission, data can be transmitted back toand fro between the two devices but at any instant of time, data can go only in one
direction. Only one end transmits at a time and the other end receives. For
example: Internet surfing.
1.6.3. Full Duplex mode: In this mode of transmission, the data can be transmitted inboth the direction simultaneously. This mode is fast as it avoids the delay caused
by the half duplex circuit each time. For example: Mobile communication.
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1.7. NETWORK TOPOLOGY: The topology of a network is the geometric representation ofthe relationship of all the links and linking devices to one another. There are mainly four
types of network topologies:-1.7.1. MESH TOPOLOGY: In this topology, every device (or nodes) has a dedicated point-
to-point link to every other device.
1. ADVANTAGES:-a) The use of dedicated links eliminates the traffic problems by
guarantying that each connection can carry its own load.
b) This topology is robust i.e. if one link becomes unusable, itdoes not incapacitate the entire system.
c) High security and privacy is maintained due to dedicatedpaths.
2. DISADVANTAGES:-a) Its major disadvantage is that the number of connections
grows quadratic ally with the number of nodes, per the
formula And so it is extremely impractical
for large networks.
b) Installation and reconnection are difficult because everydevice is connected to every other device.
c) Practical application e.g.:- connection of telephone regionaloffices.
1.7.2. STAR TOPOLOGY: - In this topology, every device (or nodes) has a dedicated point-to-point link only to a central controller, usually called a hub. The controller acts as
an exchange: if one device wants to send data to another, it sends the data to
controller which then relays the data to other connected device.
1. ADVANTAGE:-a) Less expensive compared to mesh topology.b) Easy to install and reconfigure.c) This topology also had robustness feature.
2. DISADVANTAGE:-a) Its major disadvantage is the dependency of the whole
topology on a single point, the hub.
b) If hub goes down then whole system is dead.c) Practical application:- used in Local Area Networks (LANs).
1.7.3. BUS TOPOLOGY: - This topology is a multi-point links. One long cable acts as thebackbone to link all the other devices in a network. Nodes are connected to the
bus cable by drop lines and taps. A tap is a connector that either splices or
punctures the sheathing to create a contact with metallic core.
1. ADVANTAGE:-a) Very easy to install and backbone cable is laid along the most
efficient path.
b) Uses less cabling and redundancies are eliminated.2. DISADVANTAGE:-
a) Difficult reconnection and fault isolation.
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b) Signal reflection at the taps can cause degradation in quality.1.7.4. RING TOPOLOGY: - In this topology, every device has a dedicated point-to-point
link with only the two devices on either side of it. A signal is passed along the ring
in one direction, from device to device, until it reaches its destination. Each devicein the ring incorporates a repeater.
1. ADVANTAGE:-a) To add or delete a device requires changes in only two
connections.
b) Fault isolation is simplified, if one device does not receive asignal within a specified time, it can issue an alarm which alerts
the operator.
2. DISADVANTAGES:-a) Traffic is unidirectional.b) A break in the ring can disable the entire network.
1.7.5.
HYBRID TOPOLOGY: - Hybrid networks use a combination of any two or moretopologies in such a way that the resulting network does not exhibit one of the
standard topologies (e.g., bus, star and ring).A hybrid topology is always produced
when two different basic network topologies are connected. Two common
examples for Hybrid network are: star ring networkand star bus network. A Star
ring network consists of two or more star topologies connected using a
multistation access unit (MAU) as a centralized hub. A Star Bus network consists of
two or more star topologies connected using a bus trunk (the bus trunk serves as
the network's backbone).
1.8. CATEGORIES OF NETWORKThe category of a network is determined by its size. Mainly the networks are divided into 3
types of categories:-
1.8.1. Local Area Network: - A LAN is a computer network that interconnects computersin a limited area such as a home, school, computer laboratory, or office building
using network media. Normally LAN covers an area up to 3km.LANs are designed
to allow resources to be shared between personal computers or workstations. The
resources to be shared can be hardware, software or data. The most common LAN
topologies are bus, ring and star. Speeds of data rate in LAN are 100 to
1000Mbps.It is normally privately owned.1.8.2. Wide Area Network: - A WAN provides long-distance transmission of data, image,
audio and video information over large geographical areas that may be a country,
continent or whole world using private or public network transports. Business and
government entities utilize WANs to relay data among employees, clients, buyers,
and suppliers from various geographical locations. In essence, this mode of
telecommunication allows a business to effectively carry out its daily function
regardless of location. The Internet can be considered a WAN as well, and is used
by businesses, governments, organizations, and individuals for almost any purpose
imaginable.1.8.3. Metropolitan Area Network: - A MAN is a network with a size between a LAN and
a WAN. It normally covers the area inside the town or a city. It is designed for the
customers who need a high-speed connectivity to the internet, and have endpointsspread over a city or part of a city. One of the examples is cable TV network that
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originally was designed for cable TV, but today can also be used for high-speed
data connection to the internet.
1.9. ANALOG, DIGITAL AND COMPOSITE SIGNALS1.9.1. ANALOG SIGNALS: An analog signal has infinitely many levels of intensity over a
period of time. The term analog data refers to information that is continuous.
Analog data are continuous and takes continuous values. For example, an analog
clock that has hour, minute, and second hands gives information in a continuous
form; the movement of the hands are continuous. These signals can be classified
as periodic and non-periodic signals:
1. Periodic Signals: A periodic signal completes a pattern within ameasurable time frame, called period and repeats the pattern over a
subsequent identical period. A periodic analog signal can be classified
as simple or complex. A simple periodic analog signal, sine wave
cannot be decomposed into simpler signals. A composite periodic
analog signal is composed of multiple sine waves.2. Non-periodic signals: A non-periodic signal changes without exhibiting
a pattern or cycle that repeats over time.
1.9.2. DIGITAL SIGNALS: Digital data have discrete states and take discrete values. Adigital signal canhave only a limited number of defined values. These times instant
need not be equidistant, but generally they are taken at equally spaced intervals
for convenience.
1.9.3. ADVANTAGES OF DIGITAL COMMUNICATION:1. Digital communication systems are cheaper and simpler than analog
communication.
2. Using data encryption, only permitted receivers are1.10. TRANSMISSION MEDIA
A TRANSMISSION MEDIUM is defined as anything that can carry information from a source
to a destination or a path over which a signal propagates. It is usually a free space, metallic
cable, or fibre-optic cable. In telecommunications, transmission media can be divided into
two broad categories:
a. Guided media- includes twisted pair cable, coaxial cable, and fibre-optic cableb. Unguided media- means free space
1.10.1. GUIDED MEDIA: Guided media are those which provides a conduit from onedevice to another, includes twisted-pair cable, coaxial cable and fibre -optic cable.
It can also be define as, in this media waves are guided along a solid medium such
as transmission line. A signal travelling along any of these media is directed and
contained by the physical limits of the medium.
1. Twisted-pair cable:-It consists of two conductors, each with its ownplastic insulation and twisted together. One wire is used to carry
signals and other acts as a ground reference. The difference between
two is used by the receiver. The number of twists per unit length has
some effect on the quality of the cable. Twisted pair are used in
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telephones to provide voice and data channels. These are of two
types:
2. Unshielded twisted-pair cable: This is commonly used for computernetworks within a building that is for Local area networks. Data rate of
LANs using twisted pair is 10Mbps to 100Mbps. The data rate depends
on the thickness of the cable and distance between the transmitter
and receiver. Two types of UTP are common in LANs: category 3 and
category 5. This is also used in telephones. The most common UTP
connector is RJ45 (RJ stands for registered jack); it is a keyed
connector, meaning the connector can be inserted in only one way.
3. Shielded twisted-pair cable: STP cable has a metal foil or braided-mesh covering that encases each pair of insulated conductors. Metal
casing improves the quality of cable by preventing the penetration of
noise or crosstalk; it is also bulkier and more expensive.4. Coaxial cable: - It carries signal of higher frequency ranges than those
in twisted-pair cable. It has a central core conductor of solid wire
enclosed in an insulating sheath, which is, in turn, encased in an outer
conductor of metal foil, braid, or a combination of the two. Coaxial
cables are categorized by their radio government ratings. Each cable
defined by an RG rating is adapted for a specialized function such as
a. RG-59 -75 ohm impedance - cable TVb. RG-58 -50 ohm impedance -Thin Ethernetc. RG-11 -50 ohm impedance -Thin Ethernet
The attenuation is much higher in coaxial cables than in twisted-
pair cable. It requires the frequent use of repeaters due to rapid
signal weakening. These are widely used in analog telephone networks
and also used in traditional Ethernet LANs. Cable TV networks also use
coaxial cables
5. Fibre-optic cable: - It is made of glass or plastic and transmits signals inthe form of light. Optical fibre uses reflection to guide light through a
channel. A glass or plastic core is surrounded by a cladding of less
dense glass or plastic. The difference in density of two materials mustbe such that a beam of light moving through the core is reflected off
the cladding instead of being refracted into it. It is often found in
backbone networks because its wide bandwidth is cost-effective.
Advantages and disadvantages of optical fibre:
a. Higher bandwidth and less signal attenuation.b. Immunity to electromagnetic interference and to tapping.c. Resistance to corrosive materials.d. Light weighte. Difficult to install and maintain.f. Unidirectional light propagation.
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1.10.2. UNGUIDED MEDIA: - (or WIRELESS) this media transport electromagnetic wavewithout using a physical conductor. Signals are broadcast through free space.
These signals can travel in several ways:1. GROUND PROPAGATION: - In this, radio waves travel through the
lowest portion of the atmosphere, or near the earths surface.
Distance of transmitting depends on the power of the signal.
2. SKY PROPAGATION: - In this, higher frequency radio waves radiateinto the ionosphere and get reflected back to the earth at destination.
It allows greater distance with lower output power.
3. LINE-OF-SIGHT PROPAGATION: - In this type of propagation, veryhigh-frequency signals are transmitted in straight lines directly from
antenna to antenna.
1.11. WIRELESS TRANSMISISSION WAVES:-1.11.1. RADIO WAVES: electromagnetic waves ranging between 3 KHz to 1GHz are called
radio waves. These are Omni-directional i.e. the sending and receiving antennas do
not have to be aligned but radio wave from one antenna may interfere another
antenna sending signal at same frequency.
The Omni directional characteristic of radio waves makes them useful for
Multicast communications (or multicasting). AM and FM radio, TV, cordless
phones, and paging are examples of multicasting.
1.11.2. MICROWAVES: Electromagnetic waves having frequencies between 300 MHz to300 GHz are called microwaves. These are unidirectional i.e. the sending andreceiving antennas need to be aligned. Microwave propagation is line-of-sight.
Very high-frequency microwaves cannot penetrate walls.
1.11.3. INFRARED WAVES: These waves with frequency 300GHz to 400THz can be used forshort range communication. Infrared waves, having high frequencies, cannot
penetrate walls. Infrared signals can be used for short-range communication in a
closed area using line of sight propagation.
1.12. SWITCHINGSWITCHED NETWORK: It is a network which consists of a series of interlinked nodes , called
switches. A switch is a telecommunication device which receives message from any device
connected to it and transmits it to the device for which it was meant. There are generally 2
types of switching networks:
1.12.1. Circuit switched networks:1. A circuit-switched network is a data transmission service requiring the
establishment of a circuit-switched connection before data can be
transferred.
2. It is made of a set of switches connected by physical links, in whicheach link is divided into n-channels.
3. Circuit switching takes place at physical layer.
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4. The resource must remain dedicated during the entire duration of datatransfer until the teardown phase.
5. Data transferred between the two stations are not packetized, itscontinuous flow.
6. No addressing is involved during the data transfer. The switches routethe data based on their occupied band (FDM) and time slot (TDM).
1.12.2. Packet switched networks:1. A packet-switched network is a digital communications network that
groups all transmitted data, irrespective of content, type, or structure
into suitably sized blocks, calledpackets.2. The network over which packets are transmitted is a shared network
which routes each packet independently from all others and allocates
transmission resources as needed.
3.
Data is divided into packets and then transmitted over the network.4. No resource allocation for a packet i.e. no reserved bandwidth on thelinks.
5. Main goal is to optimize utilization of available link capacity, minimizeresponse times and increase the robustness of communication.
1.12.3. Circuit Switching Technique in Telephone: The Circuit Switching Technique isused in telephones. A circuit switching telephone circuit is only 30-40% efficient as
most of the time is spent in listening mode. A synchronous Transfer Mode (STM)
uses circuit switching. In telephones also works like circuit switching:
1. First, before communicating, a dedicated path is established. Here, theconnection set up means creating dedicated channels between the
switches. The connection is established only when the
acknowledgement sent by a system is received by the other system.
2. After the connection set up, the data is transferred between the twocommunicating parties.
3. When a party needs to disconnect, a signal is sent to each switch torelease the resource and the call is disconnected.
Connection is established
before data transfer
Wired link
Wired link
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Figure: 1.1
1.12.4. DATAGRAM NETWORKS: In this technique, the data is divided into severaldatagram and then sent them independently into the network. This is also called
connectionless network. Main features of this network are:
1. Each packet is treated independently of all other packets.2. Datagram switching is done at the network layer.3. The switch does not keep information about the connection state.4. No teardown and setup phase is present.5. High efficiency for short exchanges.6. Its simple and robust property.7. Packet size is large because the address of source and destination is
present within the datagram.
1.12.5. VIRTUAL-CIRCUIT NETWORKS: These networks are a cross between circuit-switched network and datagram network. Its features are:
1. There are setup and teardown phase along with data transfer phase.2. The data is divided into several packets and resource can be allocated
during the setup phase.
3. All the packets follow the same path established during theconnection.
4. It is implemented normally in data link layer.5. Smaller packets and sequence number are allotted to each packet.6. Efficient for long transfers.
1.13. TELEPHONE AND CABLE NETWORK FOR DATA TRANSFERTELEPHONE NETWORKS: Telephone networks use circuit switching. The telephone
network is made of three major components:
Local loops: The local loop is a twisted pair cable that connects the subscriber telephone to
the nearest end office or local central office. The local loop, when used for voice, has a
bandwidth of 4000Hz.
Trunks: Trunks are the transmission media that can handle the communication between
offices. A trunk handles hundreds or thousands of connections through multiplexing.
Switching offices: Two avoid having a permanent physical link between any two
subscribers; the telephone company has switches located in switching offices.1.13.1. INTRODUCTION OF LATAs: In 1970 the U.S government sued the AT&T Bell System
believing that they are monopolizing the telephone service industry as it was
providing almost all local and long-distance services, resulting in the AT&T
divestiture of 1984, which divided the country into more than 200 LATAs; some
companies allowed to provide services inside the LATA (LECs) and other to provide
services between the LATAs (IXCs).
LATAs: It stands for Local-access transport areas. A LATA can be small or largemetropolitan area. These are divided into two categories:
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Intra-LATA services: The services offered by the common carriers inside a LATA are
called intra-LATA services. The carrier that handles these services is called a local
exchange carrier. Since 1996, there are two types of LECs: Incumbent local
exchange carriers, provides the main services and Competitive local exchange
carriers, which provides other services such as mobile telephone service, toll calls
inside a LATA.
Inter-LATA services: The services between LATAs are handled by Interexchange
carriers (IXCs).These carriers provide communication services between two
customers in different LATAs. Carriers providing inter-LATA services include AT&T,
MCI, WorldCom, Sprint and Verizon.
1.14. DIAL-UP MODEMS: The term modem refers to the two functional entities that make upthe device: a signal modulator and a signal demodulator. A modulator creates a band pass
analog signal from binary data and a demodulator recovers the binary data from the
modulated signal. These are used on both the ends of the communication system. Thedigital data sent from the sender is converted into analog signal by the modem at senders
end and this analog signal is then sent on the telephone lines and the modem at receiver
end converts the analog signal into digital data and delivers it to the receiver. Most popular
modems available are:
1.14.1. V.32 modem: This uses a combined modulation and encoding technique calledtrellis- coded modulation. The V.32 calls for 32-QAM with a baud rate of 2400.
Because only 4 bits of each pentabit represent data, the resulting data rate is
4*2400=9600. V.32bis has an automatic fall-back and fall-forward feature that
enables the modem to adjust its speed upward or downward depending on the
quality of the line or signal.
1.14.2. V.34bis: This modem provides a bit rate of 28,800 with a 960-point constellationand a bit rate of 33,600bps with a 1664-point constellation.
1.14.3. V.90: these modems with a bit rate of 56,000bps available; these are called 56Kmodems. These modems may be used only if one party is using digital signalling.
These are asymmetric.
1.14.4. V.92: The standard above V.90 is called V.92. These modems can adjust theirspeed, and if the noise allows, they can upload data at the rate of 48Kbps. The
downloading speed is still 56Kbps. This modem can interrupt the internet
connection when there is an incoming call.
1.15. DIGITAL SUBSCRIBER LINE: This technology supports high-speed digital communicationover the existing local loops. It is a set of technologies, each differing in the first letter,
these are:
1.15.1. ADSL: This technology is introduced first in DSL technology. It stands forasymmetric DSL. These lines provide higher speed (or bit rate) in the downward
direction than in the upward direction. Thats why they are called asymmetric.
ADSL uses the existing local loops (these loops can handle bandwidths up to
1.1MHz). This is an adaptive technology. The system uses a data rate based on the
condition of the local loop.
1.15.2. ADSL Lite: This is a new version of ADSL technology. This technology allows anADSL Lite modem to be plugged directly into a telephone jack and connected to
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the computer. The splitting id done at the telephone company. It uses 256DMT
carriers with 8-bit modulation. It provides a maximum downstream data rate of
1.5Mbps and an upstream data rate of 512Kbps.
1.15.3. HDSL: The high-bit-rate digital subscriber line was designed as an alternative to T-1 line. The T-1 line uses alternate mark inversion (AMI) encoding, which is very
susceptible to attenuate at high frequencies, whereas HDSL uses 2B1Q encoding
which is less susceptible to attenuation. It uses two twisted pairs to achieve full-
duplex transmission.
1.15.4. SDSL: The symmetric digital subscriber line is a one twisted-pair version of HDSL. Itprovides full-duplex symmetric communication supporting 768kbps data rate in
both the directions. It is not much suitable for businesses that send and receive
data in large volumes in both the directions.
1.15.5. VDSL: The very high -bit-rate digital subscriber line, an alternative for ADSL, usescoaxial, fibre-optic, or twisted pair cable for short distances. It uses DMTmodulating technique. It provides a range of bit rates 25 to 55Mbps for upstream
and 3.2mbps for downstream.
1.16. CABLE TV NETWORKS: The cable TV network started as a video service provider, but it hasmoved to the business of internet access.
1.16.1. TRADITIONAL VABLE NETWORKS: Cable TV started to broadcast video signals inlate 1940s. It was called community antenna TV because an antenna at the top of
a tall hill or building received the signals from the TV stations and distributed them,
via coaxial cables, to the community. The cable TV office receives video signals
from broadcasting stations and feeds to the coaxial cables. The signals became
weaker and weaker with distance, so amplifiers are installed through the network
to renew it. Communication in the traditional cable TV network is unidirectional.
1.16.2. HYBRID FIBER-COAXIAL NETWORK: This network uses a combination of fibre-opticand coaxial cable. The regional cable head serves up to 400,000 subscribers. The
distribution hub is responsible for modulation and demodulation of signals. The
signals are then fed to fibre nodes through fibre-optic cable. The use of fibre-optic
cable reduces the need for amplifiers. Communication in an HFC cable TV network
can be bidirectional.
1.17. CABLE TV FOR DATA TRANSFER:1.17.1. BANDWIDTH: The coaxial cable has a bandwidth that ranges from 5 to 750MHz.
To provide internet access , this bandwidth is divided into two bands:
1. Downstream Video Band: It occupies frequencies from 54 to 550MHz.Since each channel is of 6MHz, it can accommodate more than 80
channels.
2. Downstream Data Band: It occupies the upper band, from 550 to750MHz.Downstream data band uses the 64-QAM modulation
technique. There are 6 Bits/baud in 64-QAM. One bit is used for
forward error correction and other 5 bits for data. Downstream data
can be received at 30MHz.
3. Upstream Data Band: It occupies the lower band, from 5 to 42MHz.This band is also divided into 6MHz channels. Since it uses lower
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WEP QUIZ III
Telelabs Wireless Technologies Private Limited, Mumbai Hub, C-18, Gr. Floor, Kailash Esplanade, LBS Road,
Opp. Shreyas Cinema, Ghatkopar West, Mumbai 400086, Ph022 6448 0114 website: www.teleleabs.in
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frequencies that are more susceptible to noise and interference, QPSK
modulation technique is preferred. There are 2 bits/baud in QPSK,
therefore upstream data can be sent at 12MHz.
1.17.2. CM and CMTS:1. CM: The cable modem is installed on the subscriber premises. It is
similar to an ADSL modem.
2. CMTS: The cable modem transmission system is installed inside thedistribution hub by the cable company. It receives data from the
internet and passes them to the combiner, which sends them to the
subscriber. The CMTS also receives data from the subscriber and
passes them to the internet.
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WEP Module II
Telelabs Wireless Technologies Private Limited, Mumbai Hub, C-18, Gr. Floor, Kailash Esplanade, LBS Road,
Opp. Shreyas Cinema, Ghatkopar West, Mumbai 400086, Ph022 6448 0114 website: www.teleleabs.in
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WEP QUIZ III
Telelabs Wireless Technologies Private Limited, Mumbai Hub, C-18, Gr. Floor, Kailash Esplanade, LBS Road,
Opp. Shreyas Cinema, Ghatkopar West, Mumbai 400086, Ph022 6448 0114 website: www.teleleabs.in
14