Internship Report on “Technical Specification of Television System” based on ‘Channel i’ Bangladesh

RAB 8 Barisal

Channel i

 

Introduction (about Channel I) :

Channel i is the first digital Bangla channel. It runs 24 hours a day since launching in October 1, 1999. Channel i with the slogan “Hridoya Bangladesh” (means Bangladesh in it’s heart) has been acclaimed as one of the leading educational and entertainment Bangla channels. The channel is using C band space segment from Telstar 10 at 76.5° E geo-stationary orbital location. More than 84 countries including part of Australia, Asia and Pacific Islands, Middle East, Africa and part of Europe are covered by the global C-band beam Telstar 10, where Channel i is available.

Channel i is being distributed across the USA since 2004 through Dish Network on 24 x 7 basis with the slogan of Probashey-O-Bangladesh (means Bangladesh in overseas).

The target viewers of Channel i are all over Bangla speaking people and it is a general entertainment exclusive Bangla channel, suitable for all members of a family.

 

At a glance : Channel I is a privately owned Television network in Bangladesh and the country’s first digital channel .It is owned by Impress Group,among the largest conglomerates in Bangladesh with interests in textiles,pharmaceuticals and media.

It currently broadcasts satellite transmissions using panAm sat,which covers most of Asia and parts of Australia and Europe where it has started broadcasting in October,2007 on sky EPG channel 826.

Channel I started transmissions on October 1,1999.

 

Digital/Data Transmission:

Data transmission, digital transmission, or digital communications is the physical transfer of data (a digital bit stream) over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibres, wireless communication channels, and storage media. The data is represented as an electromagnetic signal, such as an electrical voltage, radiowave, microwave, or infrared signal.

While analog communications is the transfer of continuously varying information signal, digital communications is the transfer of discrete messages. The messages are either represented by a sequence of pulses by means of a line code (baseband transmission), or by a limited set of continuously varying wave forms (passband transmission), using a digital modulation method. The passband modulation and corresponding demodulation (also known as detection) is carried out by modem equipment. According to the most common definition of digital signal, both baseband and passband signals representing bit-streams are considered as digital transmission, while an alternative definition only considers the baseband signal as digital, and passband transmission of digital data as a form of digital-to-analog conversion.

Data transmitted may be digital messages originating from a data source, for example a computer or a keyboard. It may also be an analog signal such as a phone call or a video signal, digitized into a bit-stream for example using pulse-code modulation (PCM) or more advanced source coding (analog-to-digital conversion and data compression) schemes. This source coding and decoding is carried out by codec equipment.

 

Digital Television Systems: Digital television (DTV) is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV. Many countries are replacing over-the-air broadcast analog television with digital television to allow other uses of the radio spectrum formerly used for analog TV broadcast.

To decode DTV signals into watchable television, a digital television adapter is required, either built into a television set, as a separate device (a “set-top box”) connected to a television set, or as an electronic card, a built-in module, or a separate device connected to a personal computer or similar device.

Comprehensive tuning information of Channel I:                                               

 To watch Channel i from a supported location please collect a C Band TVRO unit with a Digital Receiver and tune with following information :

Satellite :BskyB(UK) Channel 826

Dish Network (USA) Channel 806

 

Cable :UCS BD Channel 15

Prisma Digital BD Channel 10

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Satellite television:

Satellite television is television programming delivered by the means of communications satellite and received by an outdoor antenna, usually a parabolic mirror generally referred to as a satellite dish, and as far as household usage is concerned, a satellite receiver either in the form of an external set-top box or a satellite tuner module built into a TV set. Satellite TV tuners are also available as a card or a USB stick to be attached to a personal computer. In many areas of the world satellite television provides a wide range of channels and services, often to areas that are not serviced by terrestrial or cable providers.

Direct broadcast satellite television comes to the general public in two distinct flavors – analog and digital. This necessitates either having an analog satellite receiver or a digital satellite receiver. Analog satellite television is being replaced by digital satellite television and the latter is becoming available in a better quality known as high-definition television.

Direct broadcast via satellite

Direct broadcast satellite, (DBS) also known as “Direct-To-Home” can either refer to the communications satellites themselves that deliver DBS service or the actual television service. DBS systems are commonly referred to as “mini-dish” systems. DBS uses the upper portion of the Ku band, as well as portions of the Ka b .Modified DBS systems can also run on C-band satellites and have been used by some networks in the past to get around legislation by some countries against reception of Ku-band transmissions.

Most of the DBS systems use the DVB-S standard for transmission. With Pay-TV services, the datastream is encrypted and requires proprietary reception equipment. While the underlying reception technology is similar, the Pay-TV technology is proprietary, often consisting of a Conditional Access Module and smart card.

This measure assures satellite television providers that only authorised, paying subscribers have access to Pay TV content but at the same time can allow free-to-air (FTA) channels to be viewed even by the people with standard equipment (DBS receivers without the Conditional Access Modules) available in the market.

Television receive-only

The term Television receive-only, or TVRO, arose during the early days of satellite television reception to differentiate it from commercial satellite television uplink and downlink operations (transmit and receive). This was before there was a DTH satellite television broadcast industry. Satellite television channels at that time were intended to be used by cable television networks

rather than received by home viewers. Satellite TV receiver systems were largely constructed by hobbyists and engineers. In 1978 Microcomm, a small company founded by radio amateur and microwave engineer H. Paul Shuch, introduced the first commercial home satellite TV receiver. These early TVRO systems operated mainly on the C band frequencies and the dishes required were large; typically over 3 meters (10 ft) in diameter. Consequently TVRO is often referred to as “big dish” or “Big Ugly Dish” (BUD) satellite television.

TVRO systems are designed to receive analog and digital satellite feeds of both television or audio from both C-band and Ku-band transponders on FSS-type satellites. The higher frequency Ku-band systems tend to be Direct To Home systems and can use a smaller dish antenna because of the higher power transmissions and greater antenna gain.

TVRO systems tend to use larger rather than smaller satellite dish antennas, since it is more likely that the owner of a TVRO system would have a C-band-only setup rather than a Ku band-only setup. Additional receiver boxes allow for different types of digital satellite signal reception, such as DVB/MPEG-2 and 4DTV.

The narrow beam width of a normal parabolic satellite antenna means it can only receive signals from a single satellite at a time. Simulsat or the Vertex-RSI TORUS, is a quasi-parabolic satellite earthstation antenna that is capable of receiving satellite transmissions from 35 or more C- and Ku-band satellites simultaneously.

 Direct to Home television

Many satellite TV customers in developed television markets get their programming through a direct broadcast satellite (DBS) provider. The provider selects programs and broadcasts them to subscribers as a set package. Basically, the provider’s goal is to bring dozens or even hundreds of channels to the customers television in a form that approximates the competition from Cable TV. Unlike earlier programming, the provider’s broadcast is completely digital, which means it has high picture and stereo sound quality. Early satellite television services broadcast in C-band – radio in the 3.7 GigaHertz (GHz) to 4.2 GHz frequency range. Digital broadcast satellite transmits programming in the Ku frequency range (10 GHz to 14 GHz )

Programming sources are simply the channels that provide programming for broadcast. The provider (the DTH platform) doesn’t create original programming itself. The broadcast center is the central hub of the system. At the broadcast center, the television provider receives signals from various programming sources, compresses these signals using digital compression (encryption if necessary), and sends a broadcast signal to the proper satellite.

                                                                                                                              

Technical Information:

Digital television supports many different picture formats defined by the combination of size, aspect ratio (width to height ratio) and interlacing. With digital terrestrial television (DTV) broadcasting, the range of formats can be broadly divided into two categories: HDTV and SDTV. These terms by themselves are not very precise, and many subtle intermediate cases exist.

High-definition television (HDTV), one of several different formats that can be transmitted over DTV, uses different formats, amongst which: 1280 × 720 pixels in progressive scan mode (abbreviated 720p) or 1920 × 1080 pixels in interlace mode (1080i). Each of these utilizes a 16:9 aspect ratio. (Some televisions are capable of receiving an HD resolution of 1920 × 1080 at a 60 Hz progressive scan frame rate — known as 1080p.) HDTV cannot be transmitted over current analog channels.

Standard definition TV (SDTV), by comparison, may use one of several different formats taking the form of various aspect ratios depending on the technology used in the country of broadcast. For 4:3 aspect-ratio broadcasts, the 640 × 480 format is used in NTSC countries, while 720 × 576 is used in PAL countries. For 16:9 broadcasts, the 704 × 480 format is used in NTSC countries, while 720 × 576 is used in PAL countries. However, broadcasters may choose to reduce these resolutions to save bandwidth (e.g., many DVB-T channels in the United Kingdom use a horizontal resolution of 544 or 704 pixels per line).

Each commercial broadcasting terrestrial television DTV channel in North America is permitted to be broadcast at a bit rate up to 19 megabits per second, or 2.375 megabytes per second. However, the broadcaster does not need to use this entire bandwidth for just one broadcast

channel. Instead the broadcast can be subdivided across several video subchannels (aka feeds) of varying quality and compression rates, including non-video datacasting services that allow one-way high-bandwidth streaming of data to computers.

A broadcaster may opt to use a standard-definition (SDTV) digital signal instead of an HDTV signal, because current convention allows the bandwidth of a DTV channel (or “multiplex”) to be subdivided into multiple digital subchannels, (similar to what most FM radio stations offer with HD Radio), providing multiple feeds of entirely different television programming on the same channel. This ability to provide either a single HDTV feed or multiple lower-resolution feeds is often referred to as distributing one’s “bit budget” or multicasting. This can sometimes be arranged automatically, using a statistical multiplexer (or “stat-mux”). With some implementations, image resolution may be less directly limited by bandwidth; for example in DVB-T, broadcasters can choose from several different modulation schemes, giving them the

option to reduce the transmission bitrate and make reception easier for more distant or mobile viewers.

Reception:

There are a number of different ways to receive digital television. One of the oldest means of receiving DTV (and TV in general) is using an antenna (known as an aerial in some countries). This way is known as Digital Terrestrial Television (DTT). With DTT, viewers are limited to whatever channels the antenna picks up. Signal quality will also vary.

Other ways have been devised to receive digital television. Among the most familiar to people are digital cable and digital satellite. In some countries where transmissions of TV signals are normally achieved by microwaves, digital MMDS is used. Other standards, such as DMB and DVB-H, have been devised to allow handheld devices such as mobile phones to receive TV signals. Another way is IPTV, that is receiving TV via Internet Protocol, relying on DSL or optical cable line. Finally, an alternative way is to receive digital TV signals via the open Internet. For example, there is P2P (peer-to-peer) Internet television software that can be used to watch TV on a computer.

Some signals carry encryption and specify use conditions (such as “may not be recorded” or “may not be viewed on displays larger than 1 m in diagonal measure”) backed up with the force of law under the WIPO Copyright Treaty and national legislation implementing it, such as the U.S. Digital Millennium Copyright Act. Access to encrypted channels can be controlled by a removable smart card, for example via the Common Interface (DVB-CI) standard for Europe and via Point Of Deployment (POD) for IS or named differently CableCard.

Interaction

Interaction happens between the TV watcher and the DTV system. It can be understood in different ways, depending on which part of the DTV system is concerned. It can also be an interaction with the STB only (to tune to another TV channel or to browse the EPG).

Modern DTV systems are able to provide interaction between the end-user and the broadcaster through the use of a return path. With the exceptions of coaxial and fiber optic cable, which can be bidirectional, a dialup modem, Internet connection, or other method is typically used for the return path with unidirectional networks such as satellite or antenna broadcast.

In addition to not needing a separate return path, cable also has the advantage of a communication channel localized to a neighborhood rather than a city (terrestrial) or an even larger area (satellite). This provides enough customizable bandwidth to allow true video on demand.

 

                              Broadcasting:

“1-segment broadcasting”

1seg (1-segment) is a special form of ISDB. Each channel is further divided into 13 segments. The 12 segments of them are allocated for HDTV and remaining segment, the 13th, is used for narrowband receivers such as mobile television or cell phone.

Main article: 1seg

Converting from one TV system to another

Main article: Television standards conversion

Converting between different numbers of lines and different frequencies of fields/frames in video pictures is not an easy task. Perhaps the most technically challenging conversion to make is from any of the 625-line, 25-frame/s systems to system M, which has 525 lines at 29.97 frames per second. Historically this required a frame store to hold those parts of the picture not actually being output (since the scanning of any point was not time coincident). In more recent times, conversion of standards is a relatively easy task for a computer.

Aside from the line count being different, it’s easy to see that generating 60 fields every second from a format that has only 50 fields might pose some interesting problems. Every second, an additional 10 fields must be generated seemingly from nothing. The conversion has to create new frames (from the existing input) in real time.

There are several methods used to do this, depending on the desired cost and conversion quality. The simplest possible converters simply drop every 5th line from every frame (when converting

from 625 to 525) or duplicate every 4th line (when converting from 525 to 625), and then duplicate or drop some of those frames to make up the difference in frame rate. More complex systems include inter-field interpolation, adaptive interpolation, and phase correlation

Digital TV :

The situation with worldwide digital television is much simpler by comparison. Most current digital television systems are based on the MPEG transport stream standard, and use the H.262/MPEG-2 Part 2 video codec. They differ significantly in the details of how the transport stream is converted into a broadcast signal, in the video format prior to encoding (or alternatively, after decoding), and in the audio format. This has not prevented the creation of an international standard that includes both major systems, even though they are incompatible in almost every respect.

The two principal digital broadcasting systems are ATSC, developed by the Advanced Television Systems Committee and adopted as a standard in the United States and Canada, and DVB-T, the Digital Video Broadcast – Terrestrial system used in most of the rest of the world. DVB-T was designed for format compatibility with existing direct broadcast satellite services in Europe (which use the DVB-S standard, and also sees some use in direct-to-home satellite dish providers in North America), and there is also a DVB-C version for cable television. While the ATSC standard also includes support for satellite and cable television systems, operators of those systems have chosen other technologies (principally DVB-S or proprietary systems for satellite and 256QAM replacing VSB for cable). Japan uses a third system, closely related to DVB-T, called ISDB-T, which is compatible with Brazil’s SBTVD. The People’s Republic of China has developed a fourth system, named DMB-T/H.

ATSC

The terrestrial ATSC system (unofficially ATSC-T) uses a proprietary Zenith-developed modulation called 8-VSB; as the name implies, it is a vestigial sideband technique. Essentially, analog VSB is to regular amplitude modulation as 8VSB is to eight-way quadrature amplitude modulation. This system was chosen specifically to provide for maximum spectral compatibility between existing analog TV and new digital stations in the United States’ already-crowded television allocations system, although it is inferior to the other digital systems in dealing with multipath interference; however, it is better at dealing with impulse noise which is especially present on the VHF bands that other countries have discontinued from TV use, but are still used in the U.S. There is also no hierarchical modulation. After demodulation and error-correction, the 8-VSB modulation supports a digital data stream of about 19.39 Mbit/s, enough for one high-

definition video stream or several standard-definition services. See Digital subchannel#Technical considerations for more information.

On cable, ATSC usually uses 256QAM, although some use 16VSB. Both of these double the throughput to 38.78 Mbit/s within the same 6 MHz bandwidth. ATSC is also used over satellite. While these are logically called ATSC-C and ATSC-S, these terms were never officially defined. ATSC was never designed for mobile use, but the ATSC group is currently (as of 2008[update]) considering how this can be done through its ATSC-M/H.

DMB-T/H

DMB-T/H is the digital television broadcasting standard of the People’s Republic of China, Hong Kong and Macau. This is a fusion system, which is a compromise of different competing proposing standards from different Chinese Universities, which incorporates elements from DVB-T, ADTB-T and TiMi 3.

DVB

DVB-T uses coded orthogonal frequency division multiplexing (COFDM), which uses as many as 8000 independent carriers, each transmitting data at a comparatively low rate. This system was designed to provide superior immunity from multipath interference, and has a choice of system variants which allow data rates from 4 MBit/s up to 24 MBit/s. One U.S. broadcaster, Sinclair Broadcasting, petitioned the Federal Communications Commission to permit the use of COFDM instead of 8-VSB, on the theory that this would improve prospects for digital TV reception by households without outside antennas (a majority in the U.S.), but this request was denied. (However, one U.S. digital station, WNYE-DT in New York, was temporarily converted to COFDM modulation on an emergency basis for datacasting information to emergency services personnel in lower Manhattan in the aftermath of the September 11 terrorist attacks).

DVB-S is the original Digital Video Broadcasting forward error coding and modulation standard for satellite television and dates from 1995. It is used via satellites serving every continent of the world, this is even true in North America. DVB-S is used in both MCPC and SCPC modes for broadcast network feeds, as well as for direct broadcast satellite services like Sky Digital (UK & Ireland) via Astra in Europe, Dish Network in the U.S., and Bell TV in Canada. The MPEG transport stream delivered by DVB-S is mandated as MPEG-2.

DVB-C stands for Digital Video Broadcasting – Cable and it is the DVB European consortium standard for the broadcast transmission of digital television over cable. This system transmits an MPEG-2 family digital audio/video stream, using a QAM modulation with channel coding.

ISDB: 

ISDB is very similar to DVB, however it is broken into 13 subchannels. Twelve are used for TV, while the last serves either as a guard band, or for the 1seg (ISDB-H) service. Like the other DTV systems, the ISDB types differ mainly in the modulations used, due to the requirements of different frequency bands. The 12 GHz band ISDB-S uses PSK modulation, 2.6 GHz band digital sound broadcasting uses CDM and ISDB-T (in VHF and/or UHF band) uses COFDM with PSK/QAM. It was developed in Japan with MPEG-2, and is now used in Brazil with MPEG-4. Unlike other digital broadcast systems, ISDB includes digital rights management to restrict recording of programming.

MPEG :     Short for Moving Picture Experts Group, and pronounced m-peg, is a working  group of the ISO. The term also refers to the family of digital video compression standards and file formats developed by the group. MPEG generally produces better-quality video than competing formats, such as Video for Windows, Indeo and QuickTime. MPEG files previously on PCs needed hardware decoders (codecs) for MPEG processing. Today, however, PCs can use software-only codecs including products from RealNetworks, QuickTime or Windows Media Player.

MPEG algorithms compress data to form small bits that can be easily transmitted and then decompressed. MPEG achieves its high compression rate by storing only the changes from one frame to another, instead of each entire frame. The video information is then encoded using a technique called Discrete Cosine Transform (DCT). MPEG uses a type of lossy compression, since some data is removed. But the diminishment of data is generally imperceptible to the human eye.

The major MPEG standards include the following;

  • MPEG-1: The most common implementations of the MPEG-1 standard provide a video resolution of 352-by-240 at 30 frames per second (fps). This produces video quality slightly below the quality of conventional VCR videos.
  • MPEG-2: Offers resolutions of 720×480 and 1280×720 at 60 fps, with full CD-quality audio. This is sufficient for all the major TV standards, including NTSC, and even HDTV. MPEG-2 is used by DVD-ROMs. MPEG-2 can compress a 2 hour video into a few gigabytes. While decompressing an MPEG-2 data stream requires only modest computing power, encoding video in MPEG-2 format requires significantly more processing power.
  • MPEG-3: Was designed for HDTV but was abandoned in place of using MPEG-2 for HDTV.
  • MPEG-4: A graphics and video compression algorithm standard that is based on MPEG-1 and MPEG-2 and Apple QuickTime technology. Wavelet-based MPEG-4 files are smaller than JPEG or QuickTime files, so they are designed to transmit video and images over a narrower bandwidth

and can mix video with text, graphics and 2-D and 3-D animation layers. MPEG-4 was          standardized in October 1998 in the ISO/IEC document 14496.

  • MPEG-7: Formally called the Multimedia Content Description Interface, MPEG-7 provides a tool set for completely describing multimedia content. MPEG-7 is designed to be generic and not targeted to a specific application.
  • MPEG-21: Includes a Rights Expression Language (REL) and a Rights Data Dictionary.

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MPEG1 vs MPEG2 :

                                                                                     

MPEG1 and MPEG2 are both standards for the generic coding of moving pictures and associated audio information. These standards describe the combined lossy compression of audio and video procedure which allows the storage and transmission of moving pictures with audio.

The compression standard for VHS quality digital video with a CD audio down to 1.5 Megabits per second is MPEG-1. In MPEG-1, the compression ratio of video without losing too much quality is 26:1 and the ratio or audio is 6:1. This type of compression makes it viable for digital audio and TV broadcasting as well as the creation of video CDs. As a consequence, this lossy audio and video format has become hugely popular due to its wide compatibility. Various products and applications use the MPEG-1 standard especially the audio format it introduced, the extremely popular MP3.

Then again, the older MPEG1 has some weaknesses that were addressed by its successor, the MPEG2. These said weaknesses are:

-The audio compression is limited to two channels.

– There is no standardized support for interlaced video with poor compression when used for interlaced video

– It has a limited standardized profile — Constrained Parameters Bitstream — which was incompatible for video with higher resolutions. MPEG1 might support 4k video but there was no

practical way to encode video for higher resolutions. Identification of hardware capable of support is also limited.

– It supports only one color space — 4:2:0.

MPEG 2 can be considered as an enhanced MPEG1 in terms of quality as it is used for DVD productions. MPEG2 can capture audio/video in higher resolutions and use higher bitrates, however, one won’t see much difference if the source is from a VHS type of movie quality. If one is concerned with high quality output, then, MPEG2 standard is likely to be the choice.

Officially, the MPEG2 standard adds a number of features over the older MPEG1, including Variable quantization and VBR. It is quite obvious that MPEG2 has a more complex algorithm in its encoding. MPEG2 can’t be played with MPEG1 players since MPEG2 streams are incompatible with those of MPEG1.

 

Basically, one may consider MPEG2 as an MPEG1 that supports higher resolutions and capable of using higher and variable bitrates. However, one can argue that MPEG1 performs better in lower bitrates than MPEG2.

Summary:

1. MPEG2 succeeded the MPEG1 to address some of the older standard’s weaknesses.

2. MPEG2 has better quality than MPEG1.

3. MPEG1 is used for VCD while MPEG2 is used for DVD.

4. One may consider MPEG2 as MPEG1 that supports higher resolutions and capable of using higher and variable bitrates.

5. MPEG1 is older than MPEG2 but the former is arguably better in lower bitrates.

6. MPEG2 has a more complex encoding algorithme

 Transmission:              

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Antenna used for transmission of radio signal

Transmission (in telecommunications) is the process of sending, propagating and receiving 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, or a phone call.

TV Transmission Basics:

  • Television transmissions are signals that come into your home to display an image on your TV. These signals can be sent over the air, through an antenna or satellite dish, or through a network of cables, as with cable television. These signals are converted to images before they are displayed on your screen.

3:2:1 Differences in Over the Air Transmissions

  • Over the air transmissions are usually radio signals. Antenna signals, such as UHF and VHF, and satellite signals are sent over different parts of the broadcasting spectrum, which is also used by cell phones, AM and FM frequencies and walkie-talkies. The difference between antenna and satellite signals is the frequency they transmit on, and the technology used to send them.
  • Antenna signals are sent from a radio broadcast tower, just like AM or FM signals. This is why many handheld radios can intercept antenna TV signals and play the sound. Antennas must be within range of the closest broadcast tower to receive a signal strong enough for display.
  • Satellite signals are transmitted from the broadcaster to the satellite, where they are blanket broadcast to any satellite dish capable of receiving them. Satellites are not limited by range, but by line sight, so a receiving dish must have a clear view of the satellite in the sky.
  • Cable transmissions are converted to electrical impulses. The impulses can travel much further than antenna signals, but will lose integrity after long distances.

 Antenna Signals

 

Satellite Signals

 

Cable Signals

They are over intercepted by stations that will strengthen the signal before retransmitting it to your home.

Conversion

  • Once the signal has reached your home, it is converted so you can view it on your screen. Satellite signals require special devices, known as receivers, to do this conversion. Analog cable signals sometimes need a special receiving unit, but nearly all modern TVs are considered “cable ready,” meaning they have the receiving unit built in. Any analog antenna signal can be displayed without special equipment, and TVs that are not “digital ready” will require a digital to analog converter box to properly display.                                                                

Downlink and Uplink :

These terms should not be confused with downstream and upstream.

In satellite telecommunication, a downlink is the link from a satellite down to one or more ground stations or receivers, and an uplink is the link from a ground station up to a satellite. Some companies.

sell uplink and downlink services to television stations, corporations, and to other telecommunication carriers. A company can specialize in providing uplinks, downlinks, or both.

The following table shows the main frequency bands used for satellite links.

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The C band is the most frequently used. The Ka and Ku bands are reserved exclusively for                       satellite communication but are subject to rain attenuation. Some satellites carry transponders for both C and Ku bands. Channel I uses C Band .

Fixed Uplink/Downlink Services

Türksat provides uplink/downlink for TV and Radio broadcasts with most advanced systems according to current standards, in a fully backed-up, high-quality and uninterrupted manner. Many national and international TV and radio broadcasts are packed through statistical multiplexing method, and transmitted to satellites via Türksat uplink stations within or outside Turkey.

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TV Signals Uplink and Downlink Policy

The government has formulated a policy on Uplink and Downlink of Satellite Television Signals setting provisions that every channel whether that be free or paying should annually pay Rs. 500 thousand as license fee to downlink their programme in Nepal.

According to the new arrangement, the authorized distributors of foreign signals or foreign transmitters shall take approval for downlink their programme within 90 days from the date of enforcement of policy. Likewise, the government reserves right to withdraw or to ban partially or to suspend the approval/license for a time being if the directives frequently issued by the government were not abided by.

The move has increased the government’s control on content, crushed open culture and right to criticism and added financial burden to users
“The government is trying to go for controlling policy which directly reduces Nepali people’s free access to the worldwide television channels such as BBC, CNN. It will help promote monopoly of the government and cable operators bringing added financial burden to users”, said

Different types of Monitor Using in TV  :                    

Multiscanning monitor:

A type of monitor that automatically adjusts to the signal frequency of the video display board to which it is connected. Consequently, multiscanning monitors can display images based on almost any graphics display system, including MDA, Hercules, EGA, VGA, and SVGA.

In contrast, fixed-frequency monitors respond to only one, or a few, frequencies, so they can connect to a limited number of video display boards. However, fixed-frequency monitors are less expensive than multiscanning monitors and sometimes produce sharper images.

Multiscanning monitors are also called multisync, multifrequency, and variable-frequency monitors. Increasingly, however, the term multifrequency monitor is reserved for monitors that support a fixed number of video frequencies. In contrast, multiscanning monitors scan the incoming signals and set themselves to whatever frequency range they are receiving. In practice, there is little difference between the two types of monitors because most video signals conform to one of a handful of video standards.

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TTL monitor

TTL stands for transistor-transistor logic and refers to a special type of digital circuit. More commonly, however, TTL is used to designate any type of digital input or device. A TTL monitor, therefore, is a monitor that accepts digital input. TTL monitors are consistent with older graphics standards such as MDA, but all newer graphics standards, including VGA, require analog signals.

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TP monitor:

Short for transaction processing monitor, a program that monitors a transaction as it passes from one stage in a process to another. The TP monitor’s purpose is to ensure that the transaction processes completely or, if an error occurs, to take appropriate actions.

TP monitors are especially important in three-tier architectures that employ load balancing because a transaction may be forwarded to any of several servers. In fact, many TP monitors

 

handle all the load balancing operations, forwarding transactions to different servers based on their availability.

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Wireless Monitor

There are so many new things coming out which are really great but the consumer doesn’t recognize them. One of them is the Wireless Monitor. They are really the next step to clear up your office and enjoy a complete new way of office management. Here you will find everything you have to know about them. The pros and the cons of a Wireless Monitor. So let’s jump right into the content below.

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Feed horn:

Dual Polarity Feed Horn

In satellite dish and antenna design parlance, a feedhorn (or feed horn) is a horn antenna used to convey radio waves between the transceiver (transmitter and/or receiver) and the reflector.

The feedhorn also selects the polarization of the waves to be received, which helps to attenuate unwanted signals from adjacent channels and transponders, and from other communications satellites at nearby orbital positions. On a satellite dish, the feedhorn is what is mounted at the end of a mast from the center of the dish, or on tripod legs mounted to the edge of the dish.

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Earth station:

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The Raisting Satellite Earth Station is the largest satellite communications facility in Germany.

An earth station, ground station, or earth terminal is a terrestrial terminal station designed for extraplanetary telecommunication with spacecraft, and/or reception of radio waves from an astronomical radio source. Earth stations are located either on the surface of the Earth, or within Earth’s atmosphere. Earth stations communicate with spacecraft by transmitting and receiving radio waves in the super high frequency or extremely high frequency bands (e.g., microwaves). When an earth station successfully transmits radio waves to a spacecraft (or vice versa), it establishes a telecommunications link.

Earth stations may occupy either a fixed or itinerant position. Article 1 § III of the ITU Radio Regulations describes various types of earth stations, stationary and mobile, and their interrelationships.

Specialized satellite earth stations are used to telecommunicate with satellites—chiefly communications satellites. Other earth stations communicate with manned space stations or unmanned space probes. An earth station that primarily receives telemetry data, or that follows a satellite not in geostationary orbit, is called a tracking station.

Transmission Systems:

In transmission Systems there are consists of five racks.

Rack 5:  Receiving section.

Rack4: Monitoring.

Rack3: Monitoring,

Distribution,

Cable distribution system ,

Integrating receving decoder(IRD 1 andIRD 2),

4way splitter (Horizaontal and vertical),

RC1000A antenna controller.

Rack2: Clock

Trilogy for internal communication

Control network and video router

Analog and digital converter

Video router (v1616)

Audio router(v1616)

Patching(Signal Connection)

Video Isolators.

 

Rack1:  Main Transmission section (LR -7 Processor),LR1-Dehydrator.

Information Technology(IT)

Information technology (IT) is the acquisition, processing, storage and dissemination of vocal, pictorial, textual and numerical information by a microelectronics-based combination of computing and telecommunications.The term in its modern sense first appeared in a 1958 article published in the Harvard Business Review, in which authors Leavitt and Whisler commented that “the new technology does not yet have a single established name. We shall call it information technology (IT).”

 

General information

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Information and communication technology spending in 2005

IT is the area of managing technology and spans wide variety of areas that include but are not limited to things such as processes, computer software, information systems, computer hardware, programming languages, and data constructs. In short, anything that render data, information or perceived knowledge in any visual format whatsoever, via any multimedia distribution mechanism, is considered part of the domain space known as Information Technology (IT). IT provides businesses with four sets of core services to help execute the business strategy. These four core services are broken into business process automation, providing information, connecting with customers, and productivity tools.

IT professionals perform a variety of functions (IT Disciplines/Competencies) that ranges from installing applications to designing complex computer networks and information databases. A few of the duties that IT professionals perform may include data management, networking, engineering computer hardware, database and software design, as well as management and administration of entire systems. Information technology is starting to spread further than the conventional personal computer and network technologies, and more into integrations of other

technologies such as the use of cell phones, televisions, automobiles, and more, which is increasing the demand for such jobs.

In the recent past, the Accreditation Board for Engineering and Technology and the Association for Computing Machinery have collaborated to form accreditation and curriculum standardsfor degrees in Information Technology as a distinct field of study as compared to Computer Science and Information Systems today. SIGITE (Special Interest Group for IT Education) is the ACM working group for defining these standards. The Worldwide IT services revenue totaled $763 billion in 2009.

IT setup Equipements :

  • Ø Computer
  • Ø IP address
  • Ø Cable
  • Ø Connector
  • Ø Switch
  • Ø Lan Card.

What  We should Know for IT system administration properly ???

v  Topology

v  Networking

v  Routing

v  Data link.

4:3  Network topology: 

pic

Diagram of different network topologies.

 

Topology mainly two types:

  • Physical Topology
  • Logical Topology .

Network topology is the layout pattern of interconnections of the various elements (links, nodes, etc.) of a computeror biological network.Network topologies may be physical or logical. Physical topology refers to the the physical design of a network including the devices, location and cable installation. Logical topology refers to how data is actually transferred in a network as opposed to its physical design. In general physical topology relates to a core network whereas logical topology relates to basic network.

Topology can be understood as the shape or structure of a network. This shape does not necessarily correspond to the actual physical design of the devices on the computer network. The computers on a home network can be arranged in a circle but it does not necessarily mean that it represents a ring topology.

Any particular network topology is determined only by the graphical mapping of the configuration of physical and/or logical connections between nodes. The study of network topology uses graph theory. Distances between nodes, physical interconnections, transmission rates, and/or signal types may differ in two networks and yet their topologies may be identical.

A local area network (LAN) is one example of a network that exhibits both a physical topology and a logical topology. Any given node in the LAN has one or more links to one or more nodes in the network and the mapping of these links and nodes in a graph results in a shape that may be used to describe the physical topology of the network. Likewise, the mapping data  flow .

Classification of Topology:

     The study of network topology recognizes seven basic topologies:

  • Point-to-point
  • Bus
  • Star
  • Ring
  • Mesh
  • Tree
  • Hybrid
  • Daisy chain

Point-to-point

The simplest topology is a permanent link between two endpoints. Switched point-to-point topologies are the basic model of conventional telephony. The value of a permanent point-to-point network is unimpeded communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers, and has been expressed as Metcalfe’s Law.

Permanent (dedicated)

Easiest to understand, of the variations of point-to-point topology, is a point-to-point communications channel that appears, to the user, to be permanently associated with the two endpoints. A children’s tin can telephone is one example of a physical dedicated channel.

Within many switched telecommunications systems, it is possible to establish a permanent circuit. One example might be a telephone in the lobby of a public building, which is programmed to ring only the number of a telephone dispatcher. “Nailing down” a switched connection saves the cost of running a physical circuit between the two points. The resources in such a connection can be released when no longer needed, for example, a television circuit from a parade route back to the studio.

Switched:

Using circuit-switching or packet-switching technologies, a point-to-point circuit can be set up dynamically, and dropped when no longer needed. This is the basic mode of conventional telephony.

 Bus

Main article: Bus network

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Bus network topology

In local area networks where bus topology is used, each node is connected to a single cable. Each computer or server is connected to the single bus cable. A signal from the source travels in both directions to all machines connected on the bus cable until it finds the intended recipient. If the machine address does not match the intended address for the data, the machine ignores the data. Alternatively, if the data does match the machine address, the data is accepted. Since the bus topology consists of only one wire, it is rather inexpensive to implement when compared to other topologies. However, the low cost of implementing the technology is offset by the high cost of managing the network. Additionally, since only one cable is utilized, it can be the single point of failure. If the network cable breaks, the entire network will be down.

 

Linear bus

The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has exactly two endpoints (this is the ‘bus’, which is also commonly referred to as the backbone, or trunk) – all data that is transmitted between nodes in the network is transmitted over this common transmission medium and is able to be received by all nodes in the network simultaneously.

Distributed bus

The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has more than two endpoints that are created by adding branches to the main section of the transmission medium – the physical distributed bus topology functions in exactly the same fashion as the physical linear bus topology (i.e., all nodes share a common transmission medium).

 Star

Main article: Star networkpic

Star network topology

In local area networks with a star topology, each network host is connected to a central hub with a point-to-point connection. All traffic that traverses the network passes through the central hub. The hub acts as a signal repeater. The star topology is considered the easiest topology to design and implement. An advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure.

Extended star

A type of network topology in which a network that is based upon the physical star topology has one or more repeaters between the central node (the ‘hub’ of the star) and the peripheral or ‘spoke’ nodes, the repeaters being used to extend the maximum transmission distance of the point-to-point links between the central node and the peripheral nodes beyond that which is supported by the transmitter power of the central node or beyond that which is supported by the standard upon which the physical layer of the physical star network is based.

If the repeaters in a network that is based upon the physical extended star topology are replaced with hubs or switches, then a hybrid network topology is created that is referred to as a physical hierarchical star topology, although some texts make no distinction between the two topologies.

Distributed Star

A type of network topology that is composed of individual networks that are based upon the physical star topology connected together in a linear fashion – i.e., ‘daisy-chained’ – with no central or top level connection point (e.g., two or more ‘stacked’ hubs, along with their associated star connected nodes or ‘spokes’).

 Ring                                                                                                                                        

Main article: Ring networkpic

Ring network topology

A network topology that is set up in a circular fashion in which data travels around the ring in one direction and each device on the right acts as a repeater to keep the signal strong as it travels. Each device incorporates a receiver for the incoming signal and a transmitter to send the data on to the next device in the ring. The network is dependent on the ability of the signal to travel around the ring.

Mesh

Main article: Mesh networking

The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints, is approximated by Reed’s Law.

Fully connected

pic

Fully connected mesh topology

The number of connections in a full mesh = n(n – 1) / 2.

Note: The physical fully connected mesh topology is generally too costly and complex for practical networks, although the topology is used when there are only a small number of nodes to be interconnected.

Partially connected

pic

Partially connected mesh topology

The type of network topology in which some of the nodes of the network are connected to more than one other node in the network with a point-to-point link – this makes it possible to take advantage of some of the redundancy that is provided by a physical fully connected mesh topology without the expense and complexity required for a connection between every node in the network.

Note: In most practical networks that are based upon the partially connected mesh topology, all of the data that is transmitted between nodes in the network takes the shortest path between nodes,except in the case of a failure or break in one of the links, in which case the data takes an

alternative path to the destination. This requires that the nodes of the network possess some type of logical ‘routing’ algorithm to determine the correct path to use at any particular time

Tree:

 

Main article: Tree networkpic

 

Tree network topology

This section may be confusing or unclear to readers. Please help clarify the section; suggestions may be found on the talk page. (June 2011)

Networking :

A network is a group of two or more computer systems linked together. There are many types of computer networks, including:

 Data Link :

In telecommunication a data link is the means of connecting one location to another for the purpose of transmitting and receiving information. It can also refer to a set of electronics assemblies, consisting of a transmitter and a receiver (two pieces of data terminal equipment) and the interconnecting data telecommunication circuit. These are governed by a link protocol enabling digital data to be transferred from a data source to a data sink.

There are at least three types of basic data-link configurations that can be conceived of and used:

In terms of Channel I :

Channel I uses star toplogy .Here,every switch consists of 24 pc/computer connection.

There are 7 switches in the channel I server( rack).

So,in channel I runs 7*24=168pc.in a network.

Each switch also consists of extra 4 GB webview ports,those are here for checking the  internet status.

pic

LAN :

A local area network (LAN) is a computer network that connects computers and devices in a limited geographical area such as home, school, computer laboratory or office building.[1] The defining characteristics of LANs, in contrast to wide area networks (WANs), include their usually higher data-transfer rates, smaller geographic area, and lack of a need for leased telecommunication lines.

ARCNET, Token Ring and other technology standards have been used in the past, but Ethernet over twisted pair cabling, and Wi-Fi are the two most common technologies currently in use.

pic

 Router:

A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP??s network. Routers are located at gateways, the places where two or more networks connect.

Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.

pic

Very little filtering of data is done through routers.

Transmission Control Protocol:

The Transmission Control Protocol (TCP), sometimes called the Transfer Control Protocol, is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol (IP), and therefore the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered delivery of a stream of bytes from a program on one computer to another program on another computer. TCP is the protocol that major Internet applications such as the World Wide Web, email, remote administration and file transfer rely on. Other applications, which do not require reliable data stream service, may use the User Datagram Protocol (UDP), which provides a datagram service that emphasizes reduced latency over reliability.

pic

Protocol:

In information technology, a protocol (from the Greek protocollon, which was a leaf of paper glued to a manuscript volume, describing its contents) is the special set of rules that end points in a telecommunication connection use when they communicate. Protocols exist at several levels in

a telecommunication connection. For example, there are protocols for the data interchange at the hardware device level and protocols for data interchange at the application program level. I

standard model known as Open Systems Interconnection (OSI), there are one or more protocols at each layer in the telecommunication exchange that both ends of the exchange must recognize and observe. Protocols are often described in an industry or international standard.

On the Internet, there are the TCP/IP protocols, consisting of:

  • Transmission Control Protocol (TCP), which uses a set of rules to exchange messages with other Internet points at the information packet level
  • Internet Protocol (IP), which uses a set of rules to send and receive messages at the Internet address level
  • Additional protocols that include the Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP), each with defined sets of rules to use with corresponding programs elsewhere on the Internet

There are many other Internet protocols, such as the Border Gateway Protocol (BGP) and the Dynamic Host Configuration Protocol (DHCP).

pic

                   

 

Conclusion :

                                          One of the main types of broadcast media in Bangladesh is TV. Channel i is the highly-acclaimed Bangladesh channel that offers quality educational and entertainment content. Its well-received programming includes local Bangladesh news, dramas, movies, English films, magazine programs and documentaries. Channel i is the ideal source of entertainment and information for the entire family.

Channel i runs 24 hours a day and launched the first digital Bangla channel in 1999. Since then it has grown in popularity as one of the best educational and entertainment TV channels in Bangladesh. This live Bangladeshi TV channel is mainly aimed at Bangla speaking individuals and provides programming that the entire family can enjoy.

 

This piece celebrates television in Bangladesh by discussing the role TV has played in shaping our culture, how commercial TV can act as an agent for positive social change and the interaction between TV, politics and business.

 

Referrences  :

 

1.Simon Haykin, “Digital Communications”, John Wiley & Sons, 1988. ISBN 978-0-471-62947Proceedings of the IEEE, VOL. 94, NO. 1, JANUARY 2006 (University of Texas at San Antonio)

2.Robertson, Lloyd (1972-11-09). “Anik A1 launching: bridging the gap”. CBC English TV. http://archives.cbc.ca/500f.asp?id=1-75-92-594. Retrieved 2007-01-25

3. THE VANGUARD OF TELEVISION BROADCASTING http://www.fcc.gov/oet/faqs/dtvfaqs.html

4.G. Lu, B. Krishnamachari, and C. Raghavendra, “Performance Evaluation of the IEEE 802.15.4 MAC for Low-Rate Low-Power Wireless Networks,” Proc. Workshop Energy-Efficient Wireless Comm. and Networks (EWCN ’04), Apr. 2004.

5 J. Mišic, S. Shafi, and V.B. Mišic, “Performance of 802.15.4 Beacon Enabled PAN with Uplink Transmissions in Non-Saturation Mode— Access Delay for Finite Buffers” Proc. BroadNets 2004, pp. 416-425, Oct. 2004.

6.www.webopedia.com/TERM/E/earth_station.html

7.ATIS committee PRQC. “network topology”. ATIS Telecom Glossary 2007

8.Groth, David; Toby Skandier (2005). Network+ Study Guide, Fourth Edition’. Sybex, Inc.. ISBN 0-7821-4406

9.”Basic Components of a Local Area Network (LAN)”. NetworkBits.net. http://networkbits.net/lan-components/local-area-network-lan-basic-components/. Retrieved 2008-04-08.Peterson, Larry (2003). Computer Networks. Morgan Kaufmann. pp. 401. ISBN 155860832X.

10. http://www.gont.com.ar/talks/hacklu2009/fgont-hacklu2009-tcp-security.pdf Some insights about the recent TCP DoS (Denial of Service) vulnerabilities

11. Muhammad Adeel & Ahmad Ali Iqbal (2004). “TCP Congestion Window Optimization for CDMA2000 Packet Data Networks”. International Conference on Information Technology (ITNG’07): 31–35. doi:10.1109/ITNG.2007.190. ISBN 978-0-7695-2776-5. http://www.computer.org/portal/web/csdl/doi/10.1109/ITNG.2007.190.

12. Vinton G. Cerf, Robert E. Kahn, A Protocol for Packet Network Intercommunication, IEEE Transactions on Communications, Vol. 22, No. 5, May 1974 pp. 637-648

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