AN ILLUSTRATED SURVEY ON BASIC COMMUNICATION LABORATORIES

PRABHAKAR, SUNIL KUMAR

AN ILLUSTRATED SURVEY ON BASIC COMMUNICATION LABORATORIES

Summary

This book has been written to initiate the newcomers to the Basic Communication Laboratory Concepts which is one of the fastest growing fields in the engineering world. A short Description about Technical laboratory concepts which are at the core of design, implementation, research, and invention of communication systems are presented in this text. This book will be useful for the practicing engineers, as well for researchers, graduate students, and undergraduate students.

Excerpt

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.

Fig. 2. BROADBAND LAB (Photo Courtesy., RGMTTC, Meenambakkam, Chennai)

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,

CDMA belongs to two basic categories: synchronous (orthogonal codes) and

asynchronous (pseudorandom codes).

Fig. 3. CDMA LAB (Photo Courtesy., RGMTTC, Meenambakkam, Chennai)

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

Fig.4. C-DOT LAB (Photo Courtesy., RGMTTC, Meenambakkam, Chennai)

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.

Fig. 5.,Cor DECT Lab (Photo Courtesy., RGMTTC, Meenambakkam, Chennai

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

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.

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

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.

· 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

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)

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

· 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).

· 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)

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:

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.

Fig 10,Managed Leased Line Network (MLLN) Lab.. (Photo Courtesy., RGMTTC,

Meenambakkam, Chennai)

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.

Fig. 11., Transmission lab (Photo Courtesy., RGMTTC, Meenambakkam, Chennai)

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Pages
Type of Edition: Originalausgabe
Year: 2014
ISBN (PDF): 9783954898824
File size: 2.5 MB
Language: English
Publication date: 2015 (February)
Keywords: basic communication laboratory concepts engineering world

Author

SUNIL KUMAR PRABHAKAR (Author)

AN ILLUSTRATED SURVEY ON BASIC COMMUNICATION LABORATORIES

Summary

Excerpt

Table Of Contents

Details

Author

SUNIL KUMAR PRABHAKAR (Author)