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Chapter 1: Introduction
The concept of global village in today’s world is based on computer
networking system. Today, we can never imagine our lives without computer
networking. In computer networking system, data communication or the process
of sending data from one location to another location is done electronically.
Again, we can never imagine our surroundings at homes or offices without
the installation of AC power lines. Because, we all use different electronic and
electrical appliances and instruments for the requirements of our modern life –
styles. Modern life-styles and business world heavily depend upon electrical
and electronic services utilizing different electrical/electronic instruments/
devices. For the operation of these electrical/electronic instruments/devices,
installation of power lines and power supplies are needed. This implies that
today we are surrounded by power lines at our homes, schools/colleges and
offices for smooth running of our daily lives and services. Again, for computer
networking which has become a fundamental fact of today’s life, installation of
networking cable is also essential. Therefore, at our homes or office buildings
there are two types of cable installations- one is power line or power cable
installation and the other is network cable installation.
Currently, Unshielded Twisted Pair (UTP) cable is the most popularly used
copper-based cable for networking supporting 10G Ethernet. Ethernet is the
most commonly used LAN technology. Although UTP is widely used for
networking, the main disadvantage with UTP cable is that it is the most
sensitive cable to Electromagnetic Interference (EMI) than any other networking
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cables, such as shielded twisted pair (STP) or co-axial cables. The reason
behind it is UTP cable offers low cost, ease of installation and supports high
speed of data transmission with high bandwidth, low attenuation, low cross-talk.
Electromagnetic Interference (EMI) is an undesirable phenomenon, which
creates electromagnetic disturbance in the response of electrical or electronic
systems. EMI degrades the performance of a system due to the
electromagnetic fields making up an electromagnetic environment. Since all
electric signals are electromagnetic waves, we are living in an electromagnetic
environment. Effect of electromagnetic interference or noise has become an
exceptionally crucial issue in the design of modern electronic system. Some of
the very common examples of EMI sources are-different types of lightings,
electric hand drill, Transceiver set, Fluorescent light, Microwave oven,
generators, elevator motors, different medical equipments. Generally most
electronic equipments are associated with EMI filters on the front end of their
power supplies, which are used to prevent interference or noise conducted from
power lines through the power supplies. But noise can couple into the system
through the metallic enclosures or through the data lines. UTP cable is very
much prone to electromagnetic interference. The probability to be effected by
EMI becomes high, when the cable run close to the source of EMI or grounding
system is inadequate. The EMI from the source can go through the unshielded
cable very easily and can affect the data transmission quality, which may result
in shutting down the communication system also. Shielded cables are basically
designed to protect the signal transmission through it from sources of EMI
powerful enough to generate Electromagnetic Interference. The basic functions
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of the shield are to prevent signal loss due to interference and to prevent
electromagnetic radiations to interfere with devices. In modern day building
structure, some very basic sources of EMI are found close to communication
cables. It is not always possible to avoid networking cables from running close
to EMI affected area produced by those sources. In this case, shielded cables
are advised to use instead of unshielded cables. Shielded cables are costlier
than unshielded cables. Therefore, if UTP is the first choice to be used by the
users, the first point to note is to maintain an appreciable separation gap
between UTP cable and sources of EMI to avoid interference, which may not be
always possible. Then the only option is to use shielded cables.
High speed data transmission supported by modern computer systems is
getting faster and faster day by day. Therefore, design of computer systems are
becoming harder and harder. During the process of computer design the things
to be considered are power dissipation, data transmission speed, memory
capacity and off course, protection against effect of electromagnetic
interference which may result in even failure of computer operations for
excessive effect of EMI. During the last 15-20 years, there has been a rapid
increase in the number of electromagnetic emissive sources. Our life is quite
comfortable with the uses of cellular phones, digital pagers, fax machine and
different medical instruments. Power line, which we found at our surroundings
for the operations of different electronic and electrical systems/ devices, is a
source of Electromagnetic Interference (EMI) also. Distance between the EMI
source and the victim plays an important role in the intensity of effects of EMI.
During installation of unshielded cable with the installation of AC power lines
Introduction
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within the same building structure, careful consideration has to be taken
regarding all factors, which may affect the data transmission through the
networking cable.
1.1 Networking
When two or more individual systems with data are interconnected to share
services and to interact with each other by means of a shared communication
link, a network is created. For example, suppose three computers are
connected together with a network cable and each of them are also connected
to a laser printer to use. Therefore, they create a network and each of them are
a part of the network. The size of a network depends upon the need and the
necessity of the users. To form networks, all networks must have the following
[1]:
• Data to share
• A physical pathway, called transmission medium
• Rules of communication, called protocols
1.1.1 Advantages of networking
The following are the advantages of computer networks:
• Sharing of files, resources and programs.
• Enhanced Communication between users through e-mail and groupware
applications.
• Ease of Connectivity of computers throughout the whole world
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• Improved price and performance ratios because of rapidly decreasing
cost of personal computers and related hardware.
• Improved person-to-person communication through E-mail, On-line
discussion and video conferencing.
1.1.2 Disadvantages of networking
Computer networking has some disadvantages also. They include:
• Lack of data security and privacy because of unauthorized users or
multiuser.
• High-speed network connection is expensive and has complex wiring.
• New developed reliable network software are complicated and costly.
• Crashing of the server on a server-based network because of irregular
backups.
1.1.3 Basic Components of Networking
The key Network Components with examples are:
• Media: Examples are- Twisted pair wire, coaxial cable, fiber optic cable,
microwave satellites, Cellular radio and transceivers.
• Processors: Examples are-Modems, multiplexers, concentrators,
routers, bridges, Gateways, Front-end processors and client and server
computers.
• Software: Examples are- Communication software, network operating
system, Netware, Point-to-Point Protocol (PPP), Post Office Protocol
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(POP), Simple Mail Transfer Protocol (SMTP), Internet Explorer or
Netscape Navigator and middleware.
• Channels: Examples are -Analog/ digital, switched/non-switched,
circuit/massage/Packet switching, simplex / duplex,
synchronous/asynchronous.
• Topology: Examples are- Bus, star, ring, mesh and Ethernet.
• Architecture: Examples are- OSI, Institute of Electrical and Electric
Appliances (IEEE), Integrated Services Digital Network (ISDN) and
Public Switched Telephone Network (PSTN).
1.1.4 Network Topology
In a network, each computer or device, say printer is called a node.
Network topology defines how nodes are connected to each other. It is the
geometrical arrangement of nodes and cable links in a LAN [1, 2]. Following are
the different network topologies:
• Bus Network
Bus network provides the connectivity of each computer to other computers
through a single communication cable, so that every computer can directly
communicate with every other computer or device in the network (fig 1.1).
Fig 1.1: Bus Network.
computer computer
computer computer
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• Ring Network
In a ring network, a single communication cable is used to connect several
computers or devices in a closed loop (fig 1.2).
Fig 1.2: Ring Network
• Star Network
In a star network, all the devices or computers are connected to one
common central computer. Information exchange is done by first sending to the
central computer from the source computer, which in turn sends them to the
destination computer (fig 1.3).
Fig 1.3: Star Network
computer
computer computer
computer
computer
computer
computer
central
computer
computer
computer
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• Tree Network
In a tree network, all the computers and devices are linked in a hierarchical
fashion as shown in the fig 1.4.
Fig 1.4: Tree Network
• Mesh Network
In a mesh network, every computer or device has point-to-point connections
between them (fig 1.5).
Fig 1.5: Mesh Network
computer
computer computer
computer computer
computer
Mainframe
computer
computer computer
computer computer computer computer
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1.1.5 Network Protocols
A network protocol is a set of rules and standards for communication
between computers [1]. Without protocols, the computers can only be
connected but there will be no communication between them. Because,
protocols govern the format of data, the timing, sequencing and error control.
1.1.6 Network Models
A network model is a computer network architecture. Network models are
classified into three categories:
• The peer-to-peer network where, each computer of a group is equal
in terms of authority and usage (fig 1.6). Each computer is called a
peer, which can share its resources on the net work. Each peer is both
a client and a server. There is no specialized servers exist.
Fig 1.6: Peer-to-peer network.
• The client/server network, where communication takes place
between the client and the server computers (fig 1.7). The client
requests for services and the server responds to these requests from
the client.
peer
peer
peer peer
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.
Fig 1.7: Client/server network .
• The Hybrid Network, which is a combination of two or more networks
topologies. For example, several star LANs can be connected by a bus
or a ring, or a bus that connects several ring networks (fig1.8).
Combinations of server-based and peer-to-peer networking models
constitute many networking environments.
Fig 1.8: Hybrid network.
1.1.7 Hardware and Software of Networks
Different hardware and software are needed for establishment of a network.
The hardware includes the network interface card (NIC), networking cables and
HUB HUB
compute
r
computer compute
r
computer
compute compute
r
computer compute
r
server
client client client client
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network devices. The software includes the protocols and the network operating
system.
1.1.8 The Network Interface Card (NIC)
A NIC is a device which is integrated into the system motherboard. It
enables a computer to send and receive data across the network by providing
an interface between the data bus and the networking medium. Every NIC has
a 48-bit long binary address called Media Access Control Address (MAC) and
which is used uniquely to identify each node of a computer.
1.1.9 Networking Devices
Different networking devices are
• Hubs
A hub is used to connect multiple computers together. A hub has a number
of ports and the different computers can be connected to these ports to form a
network (fig1.9).
Fig: 1.9: Hub.
HUB
computer
computer
computer
computer
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• Switches
A switch is used to join multiple computers in a network. A switch and a hub
are identical, but a switch is much more efficient. Switches are more suitable for
use in areas of high network traffic (fig1.10).
Fig 1.10: Switch
• Repeaters
A repeater is a networking hardware device, which regenerates the
transmitted attenuated information carrying signal to its original strength.
• Bridges
A bridge is a network hardware device, whose function is to regenerate the
weak signals it receives and to check the physical address of the source and
destination nodes (fig 1.11).
Fig 1.11: Bridge
SWITCH
computer computer
computer computer
Bridge
computer computer computer
computer computer computer
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• Routers
A router (fig1.12) is used to connect LANS and WANs on the internet. It
contains a routing table which takes decision about the route of a data packet.
The router, when receives a data packet from a source network, checks for the
Internet Protocol address of the destination and transfers the data packet to its
appropriate destination.
Fig 1.12: Router.
1.1.10 Networking Cables
Networking cables are the transmission media which carry data from a
source to the destination. The data is transmitted though the networking cables
in the form of electrical signals or optical signals. Different types of networking
cables are:
* The twisted pair cable
* The coaxial cable
* The fiber optical cable
1.1.11 Types of Networks
The different types of network available are: LAN, WAN and MAN.
Network 1 Router
Network 2
Network 3
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• Local Area Network (LAN)
A LAN is used to connect two or more computers within a small area [1, 2].
The area may be a room, an office building or a campus. The range of a LAN is
limited to a few kilometers only. Use of LAN enables the users to have a shared
access to devices and applications, file exchange between connected users
and communication between users. Main benefit of a LAN is that it reduces
hardware and software costs because users can share several computers and
peripheral devices.
A LAN generally consists of two or more computers, different peripheral
devices like modems, printers, plotters etc, networking cables, required
software for the operation of the computers and a plug-in board to handle the
data transmissions.
Characteristics of LAN are:
• high speed data transfer
• limited range
• less expensive technology than MAN and WAN.
Although LAN works over limited distance, it allows a large number and a
variety of computing devices to exchange information among them at high
speeds. The number of computers in LAN varies widely from small LANs to
large LANs. A small LAN can connect 2 to 25 computers while a large LAN can
connect more than 10,000 computers. The data transmission rate for LAN
technologies is up to 10Gbit/s.
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• Wide Area Network (WAN)
A WAN is used to connect computers with communication facilities covering
a wide geographical area [1, 2]. WAN connects different metropolitans,
countries and national boundaries. WANs can be interconnected with LANs. A
WAN connection may be entirely within a state or country or it may have
interconnection around the world.
Different available Protocols for WAN are X.25, TCP/IP, Frame Relay. The
transfer rate of these protocols is around 1Mbit/s or less. WAN is involved with a
public telecommunication authority. The use of WAN is limited by the large
organizations and government agencies.
Characteristics of WAN are:
• WAN interconnects multiple LANs, covers an unlimited geographical
area, but susceptible to errors due to the distances involved.
• WAN technology is expensive, more sophisticated and complex than
LANs.
Categories of WANs are:
• Enterprise WANs: Used to connect all LANs of a single organization
those are located at great distances.
• Global WANs: Used to interconnect the networks of several corporations
and organizations.
Internet is the most common example of WAN.
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• Metropolitan Area Network (MAN)
MANs technology is similar to LAN but it is a bigger version of LAN [1, 2].
Its network coverage is between LAN and WAN. MAN generally connects two
or more LANs or Campus Area Networks (CANs). MAN acts as a backbone to
connect several LANs of an organization.
Apart from these three main types of networks namely, some other types of
networks are also available. They are Personal Area Network (PAN), Campus
Area Network (CAN), Global Area Network (GAN), Value Added Network
(VAN), Virtual Private Network (VPN), Wireless /Mobile Network.
1.1.12 LAN Technologies
Various existing LAN technologies to help to establish LAN are Ethernet,
Token Ring, Token Bus and FDDI.
• Ethernet
Today, the most widely accepted and commonly used LAN technology is
Ethernet [1, 3]. Ethernet is developed by DIX (Dec, Intel and Xerox corporation)
and is a registered trademark name with Xerox corporation. Ethernet is
standardized as IEEE 802.3. Ethernet transmission data rate is million bits per
second or Mbps. Ethernet has gone through four generations based on the
speed of data transfer. They are: Standard Ethernet, Fast Ethernet, Gigabit
Ethernet and Ten-Gigabit Ethernet.
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Standard Ethernet
The data transfer rate of Standard Ethernet is 10Mbps. The original
Standard Ethernet is divided into following types:
• 10Base5: Thick Ethernet or Thicknet .
• 10Base2: Thin Ethernet or Chipernet. It is more economical than
10Base5.
• 10Base-T: Twisted Pair Ethernet. It grows in popularity because of its
reliability and flexibility and easy installation than the previous two.
• 10Base-F: Fiber Ethernet. It consists of three types, namely, 10BaseFL,
10BaseFB and 10BaseFP.
The following table1.1 shows Standard Ethernet implementations with
media and lengths.
Table 1.1: Standard Ethernet implementations
Characteristics 10Base5 10Base2 10Base-T 10Base-F
Media Thick coaxial
cable
Thin coaxial
cable
2 UTP 2 Fiber
Maximum
length
500 m 185 m 100 m 2000m
Fast Ethernet
Fast Ethernet transfers data 10 times faster than the Standard Ethernet. Its
data transfer rate is 100Mbps. Fast Ethernet is divided into following types:
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• 100BaseT4: It uses all the four pairs of wires in the cable. It was the first
type to be introduced as of Fast Ethernet.
• 100BaseTX: It uses two pairs of twisted pairs of cable. It is generally
used in office networks.
• 100BaseFX: It uses two pairs of optical fiber cable. It is generally used
as a backbone for computer networks.
The following table1.2 shows Fast Ethernet implementations with media and
lengths.
Table 1.2: Fast Ethernet implementations
Gigabit Ethernet
The data transfer rate of the Gigabit Ethernet is 1Gbps or 1000Mbps which
is 100 times faster than the original Standard Ethernet. Gigabit Ethernet is
divided into following different types:
• 1000Base-T: Refers to a standard type of four-wire implementation of
Gigabit Ethernet .Uses UTP CAT5 cable, but CAT5e or CAT6 is
preferred.
Characteristics 100Base-T4 100Base-TX 100Base-FX
Media Cat 4 UTP Optical Fiber Cat 5 UTP or STP
Number of wires 4 2 2
Maximum length 100m 100m 100m
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• 1000Base-SX: Refers to a type of Gigabit Ethernet using optical fiber. It
is a short wave two-wire implementation.
• 1000Base-LX: Refers to a type of Gigabit Ethernet using optical fiber. It
is a long wave two-wire implementation.
• 1000Base-CX: Refers to a type of Gigabit Ethernet using STP cable. It is
a two wire implementation.
The following table 1.3 shows Gigabit Ethernet implementations with media
and lengths.
Table 1.3: Gigabit Ethernet implementations
Ten-Gigabit Ethernet
Ten-Gigabit Ethernet is called as Standard 802.3ae created by IEEE
committee. It is designed to upgrade the data rate to 10Gbps. It is designed
Characteristics 1000Base-T 1000Base-
SX
1000Base-
LX
1000Base-
CX
Media Cat 5 UTP Fiber short
wave
Fiber long
wave
STP
Number of
wires
4 2 2 2
Maximum
length
100m 550m 5000m 25m
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using fiber optic cable over long distances. The most common implementations
are: 10GBase-S, 10GBase-L and 10GBase-E.
The following table 1.4 shows Ten-Gigabit Ethernet implementations with
media and lengths.
Table1.4: Ten-Gigabit Ethernet implementations.
• Token Ring
Token Ring is a LAN technology based on ring topology (fig1.13). It is
developed by International Business Machines (IBM) and is standardized as
IEEE 802.5. Token Ring transfers data at a rate from 4Mbps to 16Mbps. It uses
UTP cable and two of four pairs of cable wires.
• Token Bus
Token Bus is another type of LAN technology based on bus topology (fig
1.14). It is standardized as IEEE802.4 and is designed for large organizations.
Characteristics 10GBase-S 10GBase-L 10GBase-E
Media Short-wave
850-nm
multimode
Long-wave
1310-nm
Single mode
Extended 1550-nm
single mode
Maximum
length
300 m 10 km 40 km
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Fig 1.13: Token Ring
Fig 1.14: Token Bus
• Fiber Distributed Data Interface
Fiber Distributed Data Interface (FDDI) is a standard LAN technology using
fiber optic cable. Its data transfer rate is 100Mbps. FDDI is based on the ring
topology. It uses a dual ring model of a primary ring and a secondary ring. The
flow of data in primary ring and secondary ring are in opposite directions.
computer computer computer
computer computer
computer computer computer
computer computer
computer
Token ring
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1.1.13 Basic model of Ethernet
The fig 1.15 shows a very simple model of Ethernet network design for a
small office consisting of UTP cabling that runs from a file server to several
workstations with a printer. For UTP cabling the combined cable length
connecting workstations and printer should not exceed 100 meters.
Fig 1.15: A simple Ethernet network with a printer.
1.2 Cabling
Cabling can be classified into following types [4]:
• Campus cabling: Campus cabling is used to connect and integrate the
network within an overall area containing more than one building.
Campus cabling is usually optical fiber based and connects the main
wiring closets on different buildings.
• Riser/Backbone cabling: Riser or backbone cabling uses screened or
unscreened pair cables and used for data and telephones. It connects
computer computer computer
printer
computer computer
S
E
R
V
E
R
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the house central wiring closet to wiring closets on different building
floors.
• Horizontal cables: Horizontal twisted pair (UTP and FTP) cables
provide the communication link between and into specific work areas for
high speed networks. These cables can be used in lengths of up to 90
meters. 24AWG is the most commonly used thickness for fixed wiring.
• Work area cabling: High performance flexible work area cables are
available unscreened or Foil Screened and used for localized linking
from a wall connection to networked equipment.
• Patch cables: Patch cables are generally available unscreened or foil
screened. These cables are used to interconnect different
communication equipment.
1.2.1Types of Networking Cables
Data with information moves from one network device to another device
through networking cable. Networking cable is the transmission medium to
transmit data from one end to another end. Different types of cables are
available, which are commonly used with LANs. Selection of the type of cable
for a network depends upon the network’s topology, size, protocol and
expenditure also.
Networking cables are broadly divided into two types – copper and fiber.
Different types of networking cables offer different levels of performance. They
are:
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• Twisted Pair (TP) cable
• Co-axial cable
• Fiber Optic cable
Twisted Pair (TP) and co-axial cables are copper based cables. Copper
cabling has been used for decades to provide communication. Copper is a good
conductor of electricity. The signals through copper cable are electric signals.
Fiber optic cables are made of glass or plastic. The signals through fiber cables
are optical signals.
1.2.2 Twisted Pair Cables
A Twisted Pair (TP) consists of two copper wires, twisted together, each
with its own plastic insulation [4-8]. When electric current flows through a
copper wire, a small circular magnetic field is created around the wire. When
two current carrying wires of an electrical circuit are in close proximity, the two
magnetic fields are the exact opposite of each other. Hence they cancel each
other out. They also cancel out any outside magnetic fields. This cancellation
effect is enhanced when the two wires are twisted. Cable designers provide a
self-shielding technique against signal noise and cross-talk for wire pairs using
the cancellation effects together with twisting the wires. There are two types TP
cables. They are:
• Unshielded Twisted Pair (UTP) cable
• Shielded Twisted Pair (STP) cable.
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Unshielded Twisted Pair (UTP) Cabling
Types of UTP cable vary from telephone wire cable to extremely high speed
data supporting cable.UTP cable contains 8 wires, each 2 wires twisted
together into 4 pairs with a plastic jacket. The characteristic impedance of each
pair is 100 Ohms +/- 15%. Copper conductors of 24 gauge (0.5106-mm-
diameter) or optionally 22 gauge (0.6438 mm diameter) are used. Depending on
the number of twisted pairs and the application, each pair of UTP cable
performs different function.
EIA/TIA-568 standard specifies the electrical and physical requirements for
all types of cables. This standard also specifies the color coding, cable diameter
and electrical characteristics for cables. UTP cable must follow precise
specifications about the number of twists permitted per meter of cable.
Categories of UTP Cabling
EIA/TIA-586 has categorized 6 different categories of UTP cables by the
number of twists/foot. UTP cable with higher category number has more
twists/foot with better signal quality. Higher category number UTP cables are
technically more advanced than lower category number UTP cables. Table 1.5
shows different categories of UTP cable with their data rates, transmission
frequency and uses.
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Table1.5: Different categories of UTP cable
CAT5, CAT5e, CAT6 cables are popularly utilized for structured cabling
system in the modern building’s communication infrastructure. They can support
any voice, imaging and data applications. Performance of UTP cables are
guaranteed up to 100 meters between devices. Technically, the distance
limitation is 90 meters for structured cabling and a total of 10 meters for patch
cords on either end.
Category of UTP cable Data Rate, Frequency Uses
Category 1(CAT1) Up to 1Mbps Traditional Telephone and
ISDN-Modem
Category 2(CAT2) Up to 4Mbps Token Ring, ARCnet
Category 3(CAT3) Up to 10Mbps,16MHz Token Ring and 10Base-T
Category 4(CAT4) Up to 16 Mbps, 20MHz Token Ring
Category 5(CAT5) Up to 100 Mbps,100MHz Ethernet (10Mbps), Token
Ring (16Mbps) and
Fast Ethernet (100Mbps)
Category 5e(CAT5e) Up to 1000
Mbps,100MHz
Gigabit Ethernet
Category 6(CAT6) Up to
1000Mbps,250MHz
Gigabit Ethernet
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UTP Connector
The most common UTP connector is RJ-45 (RJ stands for registered jack)
[9]. It is an 8-position, 8-contact (8P8C) modulator plug and jack. The RJ-45 is a
keyed connector, meaning the connector can be inserted in only one way.
RJ-45 was originally patented in 1975 by Western Electric Company. Since
that time, RJ-45 has gone through many technical improvements to overcome
cross-talk as data rates have evolved from 16MHz for CAT3 to 500MHz for the
latest Category 6a standard.
Advantages of UTP cable
Advantages of UTP cable system are:
• UTP cable is a thin, flexible cable which is easy to string between walls.
Again, since UTP is small, it does not quickly fill up wiring ducts.
• UTP uses two wires rather than one for each signal. Use of two wires
allows the use of differential signaling. Differential signaling is more
immune to the effects of external electrical noise.
• In UTP cable, each pair is twisted. Twisting keeps the wires of a signal’s
pair as close as possible and hence periodically exposes the opposite
side of the pair to the noise which helps to cancel out the effects of
outside interference. Again, each pair has a different twist pitch and
therefore the pairs also appear twisted to each other which helps to
reduce cross talk between the pairs.
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• Since UTP cable is with no shielding, it reduces the cost, size and
installation time of the cable and connectors. It also eliminates the
possibility of ground loops.
Disadvantages of UTP cable
• UTP cable is more prone to electrical noise and interference than other
types of networking media.
• The distance between signal boosts is shorter for UTP than it is for
coaxial and fiber optic cable.
Shielded Twisted Pair (STP) Cable
STP is a version of the twisted pair cable created by IBM. It is an insulated
cable which includes bundled pairs wrapped in a foil shield. This type shielding
protects the cables from external electromagnetic interferences and crosstalk
[2, 3, 8]. STP is more difficult to install than UTP or coaxial cable.STP costs
more than UTP but is less expensive than thick coaxial cable or fiber optic
cable. The biggest difference between UTP and STP is the reduction of
interference of EMI provided by STP’s shielding. However, STP still suffers from
relatively low immunity from interference.
STP suffers from attenuation at a rate similar to UTP. Current technology
restricts the effective range of STP to 100 meters for supporting Fast Ethernet
(100 Base TX). But when used to support 10G Ethernet (1000 Base CX), the
effective range is limited to 25m only.
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New Generation Cabling
Category7 (Cat7) is the new generation cabling supporting 10G Ethernet
Standard [5]. Cat7 is also called SSTP (Shielded Screen Twisted Pair). It also
consists of 4pairs of twisted wires like UTP cable, each pair of wires is
individually wrapped in a helical metallic foil followed by a metallic foil shield in
addition to the outside sheath. Use of shielding reduces the effect of crosstalk
and supports a data rate up to 600MHz.
1.2.3 Co-axial cable
A coaxial cable consists of two concentric conductors. The inner conductor
is of solid copper, which is also called the core conductor. The outer conductor,
which serves as a second conductor, also serves as a shield against noise.
Between the two conductors, there is an insulating material and the whole cable
is covered with a cable jacket. The cover shields the cable from electromagnetic
interference as well as from physical danger [2, 3].
Coaxial cables bandwidth potential increases with the diameter of the inner
conductors. The cost of coaxial cable also increases with the diameter and
composition of the conductors. The cost of thin coaxial cable is less than UTP
and STP and the cost of thick coaxial cable is more than UTP and STP cable.
Coaxial cable suffers from high attenuation, but at a much lower rate than
twisted pair cables. While copper wire generally is a poor resistor to EMI, the
shielding provided by coaxial cable greatly reduces its effects.
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A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 31
Categories of Co-axial Cables
The RG (radio government) ratings are used to categorize the co-axial
cables. Different RG ratings denote different set of physical specifications and
are used for different specialized function.
The following table 1.6 shows different categories of co-axial cable.
Table 1.6: Different categories of co-axial cable
Category Impedance Use
RG-59 75Ω Cable TV
RG-58 50Ω Thin Ethernet
(10Base 2)
RG-11 50Ω Thick Ethernet
(10 Base 5)
Co-axial Cable Connectors
The most common type co-axial cable connector is the BNC (Bayone-Neill-
Concelman) connector. There are 3 types of BNC connectors: the BNC
connectors, the BNC T connectors and the BNC terminator. For connection in
Ethernet networking, the BNC T connector is used.
1.2.4 Other copper cables
There are two main types of other copper cables. They are twinaxial
(“twinax”) and single –pair full-duplex [10].
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A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 32
• Twinaxial copper cable
Twinaxial cable is similar to co-axial cable, but it has two parallel
conductors instead of one. It is an excellent choice for high speed data
transmission, but is relatively expensive. Twinaxial copper cable has not been
specified for deployment by the LAN or WAN standards bodies. It is used
primarily in mainframe computer rooms to connect various peripherals to the
computer or front-end processor. It provides a BER better than 10-18 according
to Cisco.
• Single-pair full duplex (POTS) cable
POTS cable is an UTP cable with full-duplex (simultaneous transmit and
receive) capability over a single pair of wires. Its use has been limited primarily
to analog voice-band service applications.
1.2.5 Fiber Optical Cable
In a fiber optical cable, the signal propagates in the form of light [1-3, 11] .It
has two concentric layers. The inner one is called the core, which is made up of
glass or plastic. The outer one is called the cladding, which is also made up of
glass or plastic, but it is less dense than the core. If the cladding is made of
glass, then there is also a plastic protective jacket.
The fiber optic cable has greater bandwidth than the copper cables. Due to
greater bandwidth, current technology supports data rates from 100 Mbps to
over 2Gbps, at distances from 2kms to 25kms. The supporting data rate of a
fiber optic system depends upon the composition of the used fiber, the mode
Introduction
A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 33
supported by the system and the wavelength of the transmitted light. Optical
fiber transmits data at very high speed without errors. The transmitted signals
through the optical fiber are in the form of light. Therefore, they are not
subjected to electromagnetic interference (EMI). Fiber optic cables attenuate
much less than any copper cable. They have extremely low attenuation rates.
The transmitted light signal is well confined within the optical fiber cable, so no
loss or leakage of light signal occurs. Optical fiber cable is ideal for hazardous,
high voltage or eavesdropping-sensitive environments.
Advantages of Optical Fiber cables are:
• Low cost
• Small size and light weight
• Immunity to interference
• Signal security
• Electrical isolation
• Low transmission loss and wide bandwidth
There are two types of optical fibers: single mode fiber and multimode fiber.
Light signal can transverse the multimode fiber in many modes. But single
mode fiber allows only one mode of light propagation. The fiber diameter is 8.5
microns for single mode and 50 or 62.5 microns for multimode fiber. There are
three operating wavelengths for fiber-optic systems: 850nm, 1300nm or
1550nm. The transmitted light signals are commonly referred to by their
wavelength, expressed in nanometers (nm). Optical fiber signals are in the
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A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 34
infrared portion of the spectrum, 850nm and 1300nm are the most common
wavelengths.
The following table 1.7 gives [13] the specifications for optical fiber cable
by type.
Table 1.7: Specifications for optical fiber cable
Installation of fiber optic cable is comparatively much more expensive than
any type of copper cable. Special care has to be taken to ensure that the light
path is not obstructed, at every fiber junction or connection. During installation,
the optical fiber should not be excessively stretched or bended.
1.2.6 Comparison between all types of cables
The following table 1.8 gives a comparison between all types of cable.
Cable Type Cable Type
Wavelength
Maximum
Attenuation
Minimum
Bandwidth
62.5 µm MM 850 nm 3.5 dB/km 500 MHz-km
1300 nm 1.5 dB/km 500 MHz-km
50 µm MM 850 nm 3.5 dB/km 160 MHz-km
1300 nm 1.5 dB/km 500 MHz-km
8.3 µm SM 1300 nm 1.0 dB/km n/a
1550 nm 0.5 dB/km n/a
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Table 1.8: A comparison between all types of cable
Cable
type
Cost Installation Capacity Range EMI
Co-axial
Thinnet
Less than
STP
Inexpensive/
Easy
10Mbps
typical
185 m Less
sensitive
than UTP
Co-axial
Thicknet
Greater than
STP,less than
fiber
Easy 10Mbps
typical
500 m Less
sensitive
than UTP
STP Greater than
UTP, less
Than thicknet
Fairly easy 16Mbps
typical to
500Mbps
100m
typical
Less
sensitive
than UTP
UTP Lowest Inexpensive/
Easy
10Mbps
typical to
100Mbps
100m
typical
Most
sensitive
Fiber
Optic
Highest Expensive/
difficult
100Mps
typical to as
high as
200,00Mbps
10s of
Km
Insensitive
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1.2.7 Cable Parameters of Interest
There are six parameters of interest for twisted-pair cable [10], which can be
determined from measurements using some special-purpose instruments. They
are namely:
• Z0, the characteristic impedance
• Length, the physical length of the cable
• Crosstalk, the coupling between adjacent pairs in the cable
• Resistance, the dc resistance of the copper conductors
• Attenuation, the signal loss at a specified frequency
• Wire map, the connector-to-connector wiring by pin numbers
The measurements for coaxial cable are the same for twisted-pair cable
except crosstalk and wire mapping.
1.2.8 Network Cabling Troubles
One of the most common source of problems on a network is the network
cabling. Cabling problems may result in many problems, such as disconnecting
workstations, slow network services, packet errors and unreliable data
transmission [3]. There are several things related to cabling structure resulting
problems on a network. Some of them are as follows:
• Cable length: If a cable segment is overly long, that is if a network
segment is extended beyond the IEEE specification, there will be
communication problems affecting all nodes on that segment.
• Cable type: Use of non-standard cabling.
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• Terminator: A defective or missing terminator on a network segment
may result like a network segment that is too long.
• Distance between Connectors: Two nearby workstations may face
network communication problems, if the distance between their
connectors is less than the minimum distance according to the IEEE
specifications.
• Grounding: Proper grounding is an important criteria during network
cabling installation. Lack of proper grounding may result in network
packet transmission with many Cyclic Redundancy (CRC) errors.
Grounding problems can be dangerous for network analysts and users
also.
• Cable impedance: Cable impedance must meet the required IEEE
specifications on Ethernet cable. Use of inexpensive or non standard
cable may cause data transmission problems.
• Opens and Shorts: An intermittent open or short on a cable segment
may cause intermittent problems on that segment causing network errors
and disconnection problems.
• RFI and EMI: Effect of RFI and EMI may result in noise on the data
transmission of network cable. This problem arises when the cable is run
close to the electrical field of an electric or electronic system.
• Connectors: A faulty connector may create problems causing a short or
open on the cable.
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1.2.9 Network Troubleshooting Equipments
Network troubleshooting equipments help to find the network problems and
its solutions. Some of the commonly used network test equipments are listed
below:
• Voltmeter, multimeter and optical power meter
• Transceiver monitor
• Cable scanner
• MAU analyzer
• Time domain reflectometer
• Protocol analyzer
• Remote network monitoring
A voltmeter is used to measure the voltage on a network cable or to test
signal strength on any network equipment. The multimeter has both a voltmeter
and an ohm meter. Using multimeter, the cable resistance can also be
determined as well as the voltage. An optical power meter is used to measure
the signal strength on a fiber optic cable run.
Transceivers are small devices, which are a part of the Attachment Unit
Interface (AUI). The transceiver monitor is used to detect different transceiver
problems which are related to power, signal reception and collision handing.
Cable scanners are designed to test the different network cabling plants.
Cable scanner can provide more information than a voltmeter or a multimeter.
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Multimeters are able to indicate only the presence of a short or open circuit.
But scanners are able to show the location of problems also. Scanners can find
out whether the cable is too long for IEEE specifications or not. A scanner can
also indicate that whether the cable has radio frequency interference or
electromagnetic interference or not.
A MAU analyzer functions similar to a cable scanner. It is used in Token
Ring networks.
A Time Domain Reflectometer (TDR) functions similar to an oscilloscope. It
can test various things of a network. They are line impedance, open, shorts,
electrical interference, cable distances and connector and terminator problems.
Protocol analyzers are the most comprehensive network monitoring
devices. They are expensive and contain software that is designed to interpret
specific protocol. Generally they are used in large network.
1.3 Current Trend of Cabling
1.3.1 Structured Cabling System
The term “Structured Cabling System” refers to all of the cabling and cabling
components installed in a logical, hierarchical way [4]. Previously, each of the
different data communications technology required its own type of wiring.
Today, structured cabling system which is a single wiring technology, can
support all the major existing data networking technologies. The design of
structured cabling is relatively independent of the used network, so that it can
be updated with a minimum of rework in future.
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Benefits of structured UTP cabling include:
• UTP cabling permits many communication protocols including voice,
data, CCTV video and control to reside in the same wire bundle.
• UTP cabling is a Color-coded cabling.
• UTP cable is less expensive than co-axial or fiber cable.
• UTP cable is physically smaller than co-axial and other types of cables
• UTP cabling is very easy media to install, terminate and reconfigure.
• A good properly installed UTP system gives better interference rejection
than co-axial cable system
1.3.2 Unshielded Twisted Pair Cabling
Unshielded Twisted Pair (UTP) cable is the most common cable used in
networking. Ethernet, the most common data networking standard utilizes UTP
cable. Despite of the disadvantage that UTP is the most sensitive cable to
Electromagnetic Interference (EMI) than any other type of cable, it grows in
popularity in networking world. Today, it is considered as the fastest copper
based medium for most of the major networking architectures. The reason
behind it is UTP cable offers low cost, ease of installation and supports high
speed of data transmission with high bandwidth, low attenuation, low cross-talk.
Therefore, today UTP is the most widely used networking cable for most of the
structured cabling systems. During installation of UTP cable, careful
considerations are taken to minimize the effect of EMI, by maintaining a proper
separation gap between UTP cabling and the possible EMI sources.
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A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 41
UTP is a type of cable with twisted pairs of conductors and no shield [4-8].
Types of UTP cable vary from telephone wire cable to extremely high speed
data supporting cable. Alexander Graham Bell first used UTP cable in his
telephone system in 1881. The term “UTP” is specified in the EIA/TIA-568
Commercial Building Telecommunication Wiring Standard as ‘Unshielded
Twisted Pair’ cable. This standard specifies the electrical and physical
requirements for all types of cables (UTP, STP, co-axial and optical fiber
cables). EIA/TIA-568 standard also specifies the color coding, cable diameter
and other electrical characteristics, such as cross-talk, attenuation etc for
cables. The first EIA/TIA-568 specifications were released in 1991and revised
time to time with being added to new defined categories.
To limit the signal degradation caused by EMI and RFI effects, UTP cable
designers rely solely on the cancellation effect produced by the twisted wire
pairs. The number of twists in the wire pairs also varies for further reduction of
cross talk between the pairs in UTP cable. UTP cable must follow precise
specifications about the number of twists permitted per meter of cable.
UTP cable contains 8 wires, each 2 wires twisted together into 4 pairs with a
plastic jacket. The two wires of each twisted pair represent the negative and
positive paths of a complete circuit. Each wire consists of stranded copper with
own plastic color coded cover. The two wires of each twisted pair are called the
tip wire and the ring wire. Depending on the number of twisted pairs and the
application, each pair of UTP cable performs different function. Irrespective of
the type of function, the cables carry only electrical signals between networking
devices allowing communication.
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A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 42
1.3.3 Self noise reduction technique of UTP cable
In a twisted –pair cable, the two conductor wires are twisted around each
other. The transmitted signal is the difference voltage between the two
conductor wires [12]. The directions of current flow in each wire of a pair are
opposite to each other as shown in the fig 1.16 (a).
Fig 1.16 (a): Current flow in a twisted-pair cable
Since the two currents in a twisted pair are equal and opposite, the two
magnetic fields produced by the two currents cancel each other. They cancel
out any magnetic interference caused by outside noise sources. The twisted-
pair cable is therefore less prone to interference exhibiting a self –shielding
property fig 1.16 (b).
Fig 1.16 (b): Shielding of twisted pair cables
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A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 43
Twisting of the wires in a pair reduces crosstalk between pairs to minimum.
Twisting helps to reduce EMI and RFI. It also helps in balancing the mutual
capacitance of the cable pair. The twist rate (also called pitch of the twist,
usually defined in twists per meter) makes up part of the specification for a
given type of cable.
1.3.4 Requirements of UTP
The following are the main requirements of UTP cable [5]:
• UTP has four individually twisted pairs per cable.
• The characteristic impedance of each pair is 100 Ohms +/- 15%.
• Copper conductors of 24 Gauge (0.5106-mm-diameter) or optionally 22
Gauge (0.6438 mm diameter) are used.
UTP cables are used for Ethernet, Token Ring, CDDI, ATM, ISDN, analog
telephone and other types of communication. UTP cable is frequently referred
to as ‘Ethernet Cable’ also. Performance of UTP cables are guaranteed up to
100 meters between devices. Technically, the distance limitation is 90 meters
for structured cabling and a total of 10 meters for patch cords on either end.
1.3.5 Most popularly used cables
Different most popularly used UTP cables [13-17] are described below in
brief:
• CAT5: CAT5 is a cable standard supporting Fast Ethernet speed. Its
cable types, connector types and cabling topologies are defined
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byTIA/EIA-568-B. CAT5 is most commonly used for 100 Base-TX and
1000 Base-T.
CAT5 usually comprises of 4 pairs of copper conductors, but Fast Ethernet
utilizes only 2 pairs. Cable runs are limited to a maximum recommended length
of 100m (328 feet).
• CAT5e: CAT5e is an Enhanced version of CAT5. It supports Gigabit
Ethernet (speed up to 1000Mbps) operation over short distances. It
utilizes all the 4 twisted pairs of the cable and it is backward compatible
with ordinary CAT5. Both CAT5 and CAT5e have the same bandwidth
specifications, 100MHz. The difference between CAT5 and CAT5e are in
their transmission performance. CAT5e is with additional electrical
characteristics such as power sum NEXT, equal level far-end cross –talk,
power sum equal level far-end cross-talk and return loss.
• CAT6: Cat6 is a cable standard for Gigabit Ethernet and other network
protocols that are backward compatible with CAT5 and CAT5e. CAT6
specifications are more stringent for cross-talk and noise than CAT5/5e.
CAT6 provides a performance up to 250MHz. It is an excellent choice for
10Base-T,100Base-Tx(Fast Ethernet),1000 Base-T/1000 Base-
TX(Gigabit Ethernet) and 10GBase-T(10Gigabit Ethernet).CAT6 cable
contains 4 twisted pairs, made of 22 to 24 AWG copper conductors to
meet ANSI/TIA-568-B.2-1 performance specifications. CAT6 patch
cables are normally terminated in 8P8C modular connectors (often
referred as RJ-45). For CAT6 cable and connectors, the characteristics
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Attenuation, NEXT and PSNEXT are significantly lower than CAT5 and
CAT5e.
• CAT6a: CAT6a cable or Augmented Category 6 provides a
performance up to 500MHz, which is twice that of CAT6. CAT6a
standard was defined in 2008 in ANSI/TIA/EIA-568-B-2-10 for enhanced
performance standards for twisted pair cable. When compared with
CAT6, CAT6a performs at improved specifications, especially for alien
cross-talk. CAT6 exhibits high alien noise at high frequencies. Table 1.9
shows UTP cable specifications.
Table 1.9: UTP cable specifications
CAT5 CAT5e CAT6
Ratified 1991 1999 2002
Frequency 100MHz 100MHz 250MHz
Attenuation 22dB 22dB 19.8dB
Characteristic
impedance
100Ω±15% 100Ω±15% 100Ω±15%
NEXT 32.3dB 35.3dB 44.3dB
PS-NEXT - 32.3dB 42.3dB
FLEXT - 23.8dB 27.8dB
PS-ELFEXT - 20.8dB 24.8dB
Return Loss - 20.1dB 20.1dB
Delay skew - 45ns 45ns
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A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 46
1.3.6 Technical Specification of UTP cables
• CAT5e: Technical specifications of CAT5e cable [18] are given below:
Cable Construction
Cable Properties
Conductor Bare Cu Wire
Insulated Material PE
Number of twisted pair 4
Sheath Material PVC or OHLS
Outside diameter of conductor 0.50mm
Outside diameter of insulation 0.90mm
Outside diameter of sheath 4.75mm
Min installation bend Radius 8×Dia
Min installed bending radius 4×Dia
Max installation Tension 100N
Max Installed Tension Zero
Installation Temp range 0 to 500C
Operating Temp Range -200 to 600
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Electrical Characteristics @ 200C
Characteristic impedance (1-10 & 20-
100MHz)
100±15Ω
Characteristic impedance (10-20MHz) 100±12Ω
DC Conductor Loop Resistance 19Ω/100m
Max Resistance unbalance ≤ 2%
Nominal velocity of propagation 66%
Nominal Capacitance 50pF/m
Max Capacitance unbalance 1600pF/Km
Insulation Resistance (500V) ≥2000MΩ,Km
• CAT6: Technical specifications of CAT5e cable [19] are given below:
Cable Construction
Conductor Bare Cu Wire
Insulator Material PE
Number of twisted pair 4
Spline Material PVC or LSOH
Sheath Material PVC or LSOH
Outside Diameter of Conductor(AWG) 0.59mm(23)
Outside Diameter of Insulation 1.045mM
Outside Diameter of Sheath PVC (OHLS) 5.8(5.3)mm
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Cable Properties
Electrical Characteristics @ 200C
Min. Installation Bend Radius 8×Dia
Min. Installed Bending Radius 4×Dia
Max. Installation Tension 100N
Max. Installed Tension Zero
Installation Temp. Range (Installed) 0 to 500C
Operating Temp. Range -200 to 600C
Characteristic impedance (1-100MHz) 100±15Ω
Characteristic impedance (100-
250MHz)
100±18Ω
DC Conductor Loop Resistance 15Ω/100m
Max Resistance unbalance ≤ 2%
Nominal Velocity of Propagation 66%
Nominal Capacitance 50pF/m
Max Capacitance unbalance 1600pF/Km
Insulation Resistance (500V) ≥2000MΩ,km
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1.3.7 Some guidelines for cabling installation
Recommended Cabling Practices
The followings are some recommended Cabling Practices [4]:
1. The connecting hardware should be compatible with the installed cable.
Any connecting hardware that is of a lower category than the cable being
used, should not be used.
2. Each horizontal cable should be terminated on a dedicated network
output. No cable should be leaved without termination.
3. The main cross-connect should be located near the centre of the
building. Cross-connect should not be located where the cable distance
will exceed the maximum allowed distance.
4. The twist of horizontal and backbone cable pairs should be maintained
up to the point of terminations.
5. The minimum bending radius of horizontal cables should be 4 times the
cable diameter. Making of sharp bends with cables are not
recommended.
6. Cabling should be placed at a sufficient distance from a source of EMI.
Electric wires (power line), fluorescent light are the examples of sources
of EMI.
When running cable, a few rules of thumb are advised to follow:
1. Use of more cable than need.
2. Testing of every part of an installed network.
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A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 50
3. Keeping a distance of at least 3 feet away from fluorescent light boxes
and other sources of EMI.
4. When the cable is run across the floor, the cable should be covered with
cable protectors.
5. Cable ties (not tape) should be used to keep cables in the same location
together.
6. There should be room within the conduit or casing for future expansion
of cabling.
Minimum bending radius for cables
According to EIA/TIA SP-280A the minimum bending radius for UTP is 4
times the cable outside diameter [4]. For multi-pair cable, the minimum bending
radius is 10 times the cable outside diameter.
For fiber optic cables not in tension, the minimum bend radius is 10 times of
diameter. Fiber optic cables loaded in tension may not be bent at less than 20
times of diameter. According to SP-2840A no fiber optic will be bent on a radius
less than 3cm.
Minimum for pulling during installation is 8 times the cable diameter,
minimum installed radius is 6 times the cable diameter for riser cable, 4 times
the cable diameter for horizontal cable.
UTP cabling installation practices
Followings are some common UTP cabling installation practices [4]:
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A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 51
• To avoid stretching, pulling tension should not exceed 110N or (25 lb f)
for 4-pair cables.
• Installed bend radii shall not exceed 4 times the cable diameter for
horizontal UTP cables and 10 times the cable diameter for multi-pair
backbone UTP cables.
• Avoid cable stress, as caused by cable twist during pulling or installation
– tension in suspended cable runs – tightly clinched cable ties or staples
– tight bend radii.
• Horizontal cables should be used with connecting hardware and patch
cords (or jumpers) of the same performance category or higher.
References
[1] Vikas Gupta, ‘Hardware and Networking’, Dreamtech Press, 2009.
[2] D.P. Nagpal, ‘Data Communication and Networking’, S. Chand, 2011.
[3] Behrouz A Forouzan, ‘Data Communications and Networking’, Tata
McGraw-Hill, 2008.
[4] ‘Introduction to Structured Cabling’, Division of Information Technology, Sept
2000.
[5] ‘Unshielded Twisted Pair (UTP) Cabling’. Sydnet, Firefox Document.
[6] ‘Twisted Pair Cable’, www.epanorama.net/documents/wiring/twisted
pair.html.
[7] ‘Extron Electronics-UTP Technology’, www.extron.com.
Introduction
A Study on Effect of AC Power Lines on UTP cable: A Thesis Page 52
[8] ‘Principles of Unshielded Vs. Shielded Network Cabling’ www.mohawk-
cable.com.
[9] Betsy Ziobron, ‘Twisted pair connectors continue technological evaluations’
HYPERLINE.
[10] Clyde F. Coombs. Jr.,Catherine Ann Coombs, ‘Communication Network
Test and Measurement Handbook’, Mc Graw- Hill, 1998.
[11] Subir Kumar Sarkar, ‘Optical Fibres and Fibre Optic Communication
Systems’, S. Chand & Company LTD. , 2ND edition 2001.
[12] Bdwin Wright, Deon Reynders, ‘Practical Telecommunications and
Wireless Communications for Business and Industry’, IDC Technology, 2004.
[13] ‘Cable Characteristics’, http://www.iphelp.ru/faq/36/cho7levl1sec4.html
[14] ‘Cabling’, MHTML Document.
[15] ‘Understanding CAT-5 Cables’, [email protected]
[16] ‘Cat5e UTP 4 Pair PVC Cable’, Technical Information, ultima-
comms.com
[17] ‘Category 5e UTP Cable, 25 pair’, www.ampnet connect.com
[18] ‘UTP Data Cable,Cat5e’, Datasheet, Hellerman Tyton Data Ltd., Cornwell
Business Park. www.htdata.co.uk.
[19] ‘UTP Data Cable,Cat6’, Datasheet, Hellerman Tyton Data Ltd., Cornwell
Business Park. www.htdata.co.uk.