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CHAPTER 2
BROADBAND LABORATORY
· The term broadband refers to the wide bandwidth characteristics of a transmission
medium and its ability to transport multiple signals and traffic types simultaneously.
· The medium can be coax, optical fiber, twisted pair or wireless. In contrast, baseband
describes a communication system in which information is transported across a single
channel.
· Different criteria for broad have been applied in different contexts and at different
times. Its origin is in physics, acoustics and radio systems engineering, where it had been
used with a meaning similar to wideband.
· Later, with the advent of digital telecommunications, the term was mainly used for
transmission over multiple channels. Broadband refers to a communication bandwidth of
at least 256 Kbit/s. Each channel is 6 MHz wide and it uses an extensive range of
frequencies to effortlessly relay and receive data between networks.
· In telecommunications, a broadband signaling method is one that handles a wide band
of frequencies. Broadband is a relative term, understood according to its context. The
wider (or broader) the bandwidth of a channel, the greater the information-carrying
capacity, given the same channel quality.
· A television antenna may be described as broadband because it is capable of receiving
a wide range of channels; while a single-frequency or Lo-VHF antenna is narrowband
since it receives only 1 to 5 channels.
· However when that same line is converted to a non-loaded twisted-pair wire (no
telephone filters), it becomes hundreds of kilohertz wide (broadband) and can carry up to
60 megabits per second using very-high-bitrate digital subscriber line (VDSL or VHDSL)
techniques.
· In the late 1980s, the Broadband Integrated Services Digital Network (B-ISDN) used the
term to refer to a broad range of bit rates, independent of physical modulation details.
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Fig. 2. BROADBAND LAB (Photo Courtesy., RGMTTC, Meenambakkam, Chennai)
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CHAPTER 3
CODE DIVISION MULTIPLE ACCESS LABORATORY
· Code division multiple access (CDMA) is a channel access method used by various
radio communication technologies.
· CDMA is an example of multiple access, which is where several transmitters can send
information simultaneously over a single communication channel. This allows several
users to share a band of frequencies (see bandwidth).
· To permit this to be achieved without undue interference between the users CDMA
employs spread-spectrum technology and a special coding scheme (where each
transmitter is assigned a code).
· CDMA is used as the access method in many mobile phone standards such as cdmaOne,
CDMA2000 (the 3G evolution of cdmaOne), and WCDMA (the 3G standard used by
GSM carriers), which are often referred to as simply CDMA.
A CDMA2000 mobile phone has the following features:
·
One of the early applications for code division multiplexing is in GPS. This predates and
is distinct from its use in mobile phones.
·
The Qualcomm standard IS-95, marketed as cdmaOne.
·
The Qualcomm standard IS-2000, known as CDMA2000. This standard is used by
several mobile phone companies, including the Globalstar satellite phone network.
·
The UMTS 3G mobile phone standard, which uses W-CDMA.
·
CDMA has been used in the OmniTRACS satellite system for transportation logistics.
· CDMA is a spread spectrum multiple access technique. A spread spectrum technique
spreads the bandwidth of the data uniformly for the same transmitted power.
· A spreading code is a pseudo-random code that has a narrow ambiguity function, unlike
other narrow pulse codes.
· In CDMA a locally generated code runs at a much higher rate than the data to be
transmitted. Data for transmission is combined via bitwise XOR (exclusive OR) with the
faster code.
· An analogy to the problem of multiple access is a room (channel) in which people wish to
talk to each other simultaneously.
· To avoid confusion, people could take turns speaking (time division), speak at different
pitches (frequency division), or speak in different languages (code division).
· CDMA is analogous to the last example where people speaking the same language can
understand each other, but other languages are perceived as noise and rejected. Similarly,
in radio CDMA, each group of users is given a shared code. Many codes occupy the same
channel, but only users associated with a particular code can communicate. In general,
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CDMA belongs to two basic categories: synchronous (orthogonal codes) and
asynchronous (pseudorandom codes).
Fig. 3. CDMA LAB (Photo Courtesy., RGMTTC, Meenambakkam, Chennai)
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CHAPTER 4
CENTRE FOR DEVELOPMENT OF TELEMATICS LABORATORY
· The Centre for Development of Telematics (C-DOT) is an Indian Government owned
telecommunications technology development centre. It was established in 1984 with
initial mandate of designing and developing digital exchanges.
· C-DOT has expanded its to develop intelligent computer software applications. It has
offices in Delhi and Bangalore.
· The Centre for Development of Telematics (C-DOT) was established in August 1984 as
an autonomous body. Its goal was to develop telecommunication technology to meet the
needs of the Indian telecommunication network.
· Within a very short time, telecom switching products suited to Indian conditions
appeared in the form of small rural automatic exchanges (RAXs) and medium size
switches as SBMs for towns. This was followed by higher capacity digital switches
known as main automatic exchanges (MAXs). C-DOT technology spread across the
country through its licensed manufacturers.
· Beginning with digital switching systems, C-DOT developed products for optical,
satellite and wireless communication from circuit switching technology, ATM and next
generation networks. From a purely hardware development centre, it diversified into
development of telecom software like IN, NMS, Data Clearing House and from a
protected environment of closed market to an open and competitive market.
· While developing the RAX/MAX digital switches, C-DOT also evolved processes and
procedures for manufacturing the switches in Indian factories which set up an Indian
manufacturing vendor base. Later, C-DOT projects included central monitoring systems
for telecom security, for the Indian government.
Products of C-DOT:
·
RAX : Rural Automatic Exchange is a small 256 lines switch for landlines that helped
spread telecom to rural parts of India
·
MAX : Main automatic exchange
·
Transmission Equipment
·
TDMA Point to Multipoint Radio
·
GPON
·
SGRAN (under development)
·
LTE-A (under development)
·
Soft switch
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Fig.4. C-DOT LAB (Photo Courtesy., RGMTTC, Meenambakkam, Chennai)
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CHAPTER 5
CorDECT LABORATORY
· corDECT is a wireless local loop standard developed in India by IIT Madras and Midas
Communications (www.midascomm.com) at Chennai, under leadership of Prof Ashok
Jhunjhunwala, based on the DECT digital cordless phone standard.
· The technology is a Fixed Wireless Option, which has extremely low capital costs and is
ideal for small start ups to scale, as well as for sparse rural areas. It is very suitable for
ICT4D projects and India has one such organization, n-Logue Communications that has
aptly done this.
· The full form of DECT is Digital Enhanced Cordless Telecommunications, which is
useful in designing small capacity WLL (wireless in local loop) systems. These systems
are operative only on LOS Conditions and are very much affected by weather conditions.
· System is designed for rural and sub urban areas where subscriber density is medium or
low. corDECT system provides simultaneous voice and Internet access. Following are
the main parts of the system.
DECT Interface Unit (DIU)
This is a 1000 line exchange provides E1 interface to the PSTN. This can cater up to 20 base
stations. These base stations are interfaced through ISDN link which carries signals and power
feed for the base stations even up to 3 km.
Compact Base Station (CBS)
This is the radio fixed part of the DECT wireless local loop. CBSs are typically mounted on a
tower top which can cater up to 50 subscribers with 0.1 erlang traffic.
Base Station Distributor (BSD)
This is a traffic aggregator used to extend the range of the wireless local-loop where 4 CBS can
be connected to this.
Relay Base Station (RBS)
This another technique used to extend the range of the corDECT wireless local loop up to 25 km
by a radio chain.
Fixed Remote Station (FRS)
This is the subscriber-end equipment used the corDECT wireless local loop which provides
standard telephone instrument and Internet access up to 70kbit/s through Ethernet port.
The new generation corDECT technology is called Broadband corDECT which supports
provides broadband Internet access over wireless local loop.
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Fig. 5.,Cor DECT Lab (Photo Courtesy., RGMTTC, Meenambakkam, Chennai
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CHAPTER 6
PROGRAMMABLE LOGIC CONTROLLER LABORATORY
· A Programmable Logic Controller, PLC or Programmable Controller is a digital
computer used for automation of electromechanical processes, such as control of
machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in
many industries and machines.
· Unlike general-purpose computers, the PLC is designed for multiple inputs and output
arrangements, extended temperature ranges, immunity to electrical noise, and resistance
to vibration and impact. Programs to control machine operation are typically stored in
battery-backed-up or non-volatile memory.
Fig.6 Siemens Simatic S7-400 system at rack, left-to-right: power supply unit PS407 4A,CPU
416-3, interface module IM 460-0 and communication processor CP 443-1.
· A PLC is an example of a hard real time system since output results must be produced in
response to input conditions within a limited time, otherwise unintended operation will
result.
· Before the PLC, control, sequencing, and safety interlock logic for manufacturing
automobiles was mainly composed of relays, cam timers, drum sequencers, and dedicated
closed-loop controllers. Since these could number in the hundreds or even thousands, the
process for updating such facilities for the yearly model change-over was very time
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consuming and expensive, as electricians needed to individually rewire relays to change
the logic.
· Digital computers, being general-purpose programmable devices, were soon applied to
control of industrial processes. Early computers required specialist programmers, and
stringent operating environmental control for temperature, cleanliness, and power quality.
· Using a general-purpose computer for process control required protecting the computer
from the plant floor conditions. An industrial control computer would have several
attributes: it would tolerate the shop-floor environment, it would support discrete (bit-
form) input and output in an easily extensible manner, it would not require years of
training to use, and it would permit its operation to be monitored.
· The functionality of the PLC has evolved over the years to include sequential relay
control, motion control, process control, distributed control systems and networking. The
data handling, storage, processing power and communication capabilities of some
modern PLCs are approximately equivalent to desktop computers.
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CHAPTER 7
OMCR (Operations and Maintenance Centre)
In mobile networks, an Operations and Maintenance Center is the central location to operate and
maintain the network.
There are various types of OMCs depending on the functionality:
·
OMC-B (for maintaining Node B)
·
OMC-R (radio. for maintaining RNC)
·
UMTS OMC-U
·
GPRS OMC-G
·
OMC-DO
·
OMC-IP
Fig. 7. Rajiv Gandhi Telecom Training Centre, Meenambakkam, Chennai , OMCR lab
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CHAPTER 8
INTERNET SERVICE PROVIDER LABORATORY
· An Internet service provider (ISP, also called Internet access provider) is a business or
organization that offers users access to the Internet and related services. Many but not all
ISPs are telephone companies or other telecommunication providers.
· They provide services such as Internet access, Internet transit, domain name registration
and hosting, dial-up access, leased line access and co-location. Internet service providers
may be organized in various forms, such as commercial, community-owned, non-profit,
or otherwise privately owned.
Local ISP in Manhattan installing fiber for provisioning Internet access
· Access ISPs employ a range of technologies to enable consumers to connect to their
network. Over time, available technologies have ranged from acoustic couplers to
telephone lines, to cable, wi-fi, and fiber optics.
· For users and small businesses, traditional options include copper wires to provide dial-
up, DSL (typically asymmetric digital subscriber line, ADSL), cable modem or Integrated
Services Digital Network (ISDN) (typically basic rate interface). Using fiber-optics to
end users is called Fiber To The Home or similar names.
· For customers with more demanding requirements, such as medium-to-large businesses,
or other ISPs, higher-speed DSL (such as single-pair high-speed digital subscriber line ),
Ethernet, metropolitan Ethernet, gigabit Ethernet, Frame Relay, ISDN Primary Rate
Interface, ATM (Asynchronous Transfer Mode) and synchronous optical networking
(SONET) can be used. Wireless access is another option, including satellite Internet
access. Many access providers also provide hosting and email services.
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· A mailbox provider is a department or organization that provides email mailbox hosting
services. It provides email servers to send, receive, accept, and store email for other
organizations and/or end users, on their behalf and upon their explicit mandate.
Hosting ISPs
Hosting ISPs routinely provide email, FTP, and web-hosting services. Other services include
virtual machines, clouds, or entire physical servers where customers can run their own custom
software.
Transit ISPs
Just as their customers pay them for Internet access, ISPs themselves pay upstream ISPs
for Internet access. An upstream ISP usually has a larger network than the contracting ISP and/or
is able to provide the contracting ISP with access to parts of the Internet the contracting ISP by
itself has no access to. In the simplest case, a single connection is established to an upstream ISP
and is used to transmit data to or from areas of the Internet beyond the home network; this mode
of interconnection is often cascaded multiple times until reaching a Tier 1 carrier. In reality, the
situation is often more complex. ISPs with more than one point of presence (PoP) may have
separate connections to an upstream ISP at multiple PoPs, or they may be customers of multiple
upstream ISPs and may have connections to each one of them at one or more point of presence.
Transit ISPs provide large amounts of bandwidth for connecting hosting ISPs and access ISPs.
Virtual ISPs:
A virtual ISP (VISP) is an operation which purchases services from another ISP
(sometimes called a wholesale ISP in this context) which allow the VISP's customers to access
the Internet using services and infrastructure owned and operated by the wholesale ISP. It is akin
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to mobile virtual network operators and competitive local exchange carriers for voice
communications.
Free ISPs
Free ISPs are Internet service providers which provide service free of charge. Many free
ISPs display advertisements while the user is connected; like commercial television, in a sense
they are selling the users' attention to the advertiser. Other free ISPs, often called freenets, are
run on a nonprofit basis, usually with volunteer staff.
Fig 8. ISP LABORATORY (Photo Courtesy., RGMTTC, Meenambakkam, Chennai)
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CHAPTER 9
MICROWAVE LABORATORY
· The atmospheric attenuation of microwaves in dry air with a precipitable water vapor
level of 0.001 mm. The downward spikes in the graph correspond to frequencies at which
microwaves are absorbed more strongly.
· The right half of this graph includes the lower ranges of infrared by some
standards.Microwaves are a form of electromagnetic radiation with wavelengths ranging
from as long as one meter to as short as one millimeter, or equivalently, with frequencies
between 300 MHz (0.3 GHz) and 300 GHz.
A microwave telecommunications tower on Wrights Hill in Wellington, New Zealand
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· This broad definition includes both UHF and EHF (millimeter waves), and various
sources use different boundaries. In all cases, microwave includes the entire SHF band (3
to 30 GHz, or 10 to 1 cm) at minimum, with RF engineering often putting the lower
boundary at 1 GHz (30 cm), and the upper around 100 GHz (3 mm).
· The prefix micro- in microwave is not meant to suggest a wavelength in the
micrometer range. It indicates that microwaves are small compared to waves used in
typical radio broadcasting, in that they have shorter wavelengths.
· The boundaries between far infrared light, terahertz radiation, microwaves, and ultra-
high-frequency radio waves are fairly arbitrary and are used variously between different
fields of study.
· Microwave technology is extensively used for point-to-point telecommunications (i.e.,
non broadcast uses).
· Microwaves are especially suitable for this use since they are more easily focused into
narrow beams than radio waves, allowing frequency reuse; their comparatively higher
frequencies allow broad bandwidth and high data transmission rates, and antenna sizes
are smaller than at lower frequencies because antenna size is inversely proportional to
transmitted frequency.
· Microwaves are used in spacecraft communication, and much of the world's data, TV,
and telephone communications are transmitted long distances by microwaves between
ground stations and communications satellites. Microwaves are also employed in
microwave ovens and in radar technology.
· Beginning at about 40 GHz, the atmosphere becomes less transparent to microwaves, due
at lower frequencies to absorption from water vapor and at higher frequencies from
oxygen. A spectral band structure causes absorption peaks at specific frequencies (see
graph at right).
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· Above 100 GHz, the absorption of electromagnetic radiation by Earth's atmosphere is so
great that it is in effect opaque, until the atmosphere becomes transparent again in the so-
called infrared and optical window frequency ranges.
· The term microwave also has a more technical meaning in electromagnetics and circuit
theory. Apparatus and techniques may be described qualitatively as microwave when
the frequencies used are high enough that wavelengths of signals are roughly the same as
the dimensions of the equipment, so that lumped-element circuit theory is inaccurate.
Fig. 9, Microwave lab (Photo Courtesy., RGMTTC, Meenambakkam, Chennai)
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CHAPTER 10
MANAGED LEASED LINE NETWORK (MLLN) LABORATORY
· The MLLN is a Managed Leased Line Network system which is proposed to provide
Leased line connectivity.
· With the State-of-the-art technology equipment, MLLN is designed mainly for having
effective control and monitor on the leased line so that the down time is very much
minimized and the circuit efficiency is increased thus achieving more customer
satisfaction.
· This mainly deals with data circuits ranging from 64 KBPs to 2048 KBPs.
Features of MLLN
·
Control, Manage the leased line network
·
Bandwidth management as per the customer demand
·
Pro-active maintenance, without waiting for customer to book a complaint.
·
Self Diagnostic/software loops to check E1 connectivity to DXC, VMUX/software loops
for checking copper pair at NTU point for immediately identifying the faulty section for
trouble shooting .
·
Alternate routing in case of any route failure.
·
Generation of the periodic performance reports for self-analysis/customer.
Advantages to Customers
·
Bandwidth management as per customer requirement(64 Kbps and nx 64 Kbps up to to
2048 Kbps ).
·
Saving the cost of modems. NTU is provided by MTNL without any charges.
·
Proactive maintenance
MPLS VPN is a family of methods for harnessing the power of multiprotocol label switching
(MPLS) to create virtual private networks (VPNs). MPLS VPN gives network engineers the
flexibility to transport and route several types of network traffic using the technologies of a
MPLS backbone.
There are three types of MPLS VPNs deployed in networks today:
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·
Point-to-point (Pseudowire)
·
Layer 2 (VPLS)
·
Layer 3 (VPRN)
Point-to-point (pseudo wire)
Point-to-point MPLS VPNs employ VLLs (virtual leased lines) for providing Layer2
point-to-point connectivity between two sites. Ethernet, TDM, and ATM frames can be
encapsulated within these VLLs.
Some examples of how point-to-point VPNs might be used by utilities include:
·
encapsulating TDM T1 circuits attached to RTUs
·
forwarding non-routed DNP3 traffic across the backbone network to the SCADA master
controller.
Layer 2 VPN (VPLS)
Layer 2 MPLS VPNs, or VPLS (virtual private LAN service), offers a "switch in the
cloud" style VPLS service. VPLS provides the ability to span VLANs between sites. L2 VPNs
are typically used to route voice, video, and AMI traffic between substation and data center
locations.
Layer 3 VPN (VPRN)
Layer 3, or VPRN (virtual private routed network), utilizes layer 3 VRF (VPN/virtual
routing and forwarding) to segment routing tables for each "customer" utilizing the service. The
customer peers with the service provider router and the two exchange routes, which are placed
into a routing table specific to the customer. Multiprotocol BGP (MP-BGP) is required in the
cloud to utilize the service, which increases complexity of design and implementation. L3 VPNs
are typically not deployed on utility networks due to their complexity; however, a L3 VPN could
be used to route traffic between corporate or datacenter locations.
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Fig 10,Managed Leased Line Network (MLLN) Lab.. (Photo Courtesy., RGMTTC,
Meenambakkam, Chennai)
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CHAPTER 11
TRANSMISSION (TELECOMMUNICATIONS) LABORATORY
.
Antenna used for transmission of radio signal
· In telecommunications, transmission (abbreviation: Tx) is the process of sending and
propagating an analogue or digital information signal over a physical point-to-point or
point-to-multipoint transmission medium, either wired, optical fiber or wireless.
· Transmission technologies and schemes typically refer to physical layer protocol duties
such as modulation, demodulation, line coding, equalization, error control, bit
synchronization and multiplexing, but the term may also involve higher-layer protocol
duties, for example, digitizing an analog message signal, and source coding
(compression).
· Transmission of a digital message, or of a digitized analog signal, is known as data
transmission or digital communication. One transmission is the sending of a signal with
limited duration, for example a block or packet of data, a phone call, or an email.
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·
Fig. 11., Transmission lab (Photo Courtesy., RGMTTC, Meenambakkam, Chennai)
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