Tuesday, June 4, 2013

AAJ tech news

Online travel ticketing in India has gotten mature and more Indians are making their travel plans online, says a latest research. Whether it is air tickets, bus tickets or rail tickets, people have begun to trust online booking systems like IRCTC, MakeMyTrip, RedBus and many others. In online travel, the Indian Railways has a significant contribution and IRCTC (Indian Railway Catering & Tourism Corporation), a subsidiary of the Indian Railways, handles online ticketing among other things. However, unlike other e-ticketing sites, it has often faced consumer ire for sluggish and laggy performance. Needless to say, the number of people accessing the IRCTC site is much higher than the others, especially during the two hours of tatkal or last minute bookings. The reason is simple – tatkal online booking window opens a day in advance before the date of your journey just for two hours, and all the tickets are sold within an hour. The site almost breaks down at 10 AM as it is unable to handle the load. The site has to handle 10.7 million (and growing, according to the comScore report for April 2013) unique visitors per month and it is capable of handling about 40-45,000 tatkal railway tickets during the 2-hour tatkal window. Needless to say, this isn’t enough. We are a huge population and the number of seats available could be small compared to the number of seats required (each ticket has four people trying to book it), but let’s not dwell on that. Technology cannot resolve this issue. However, the overload that the site suffers at 10 AM everyday can be resolved. During the Union Budget this year, spruced e-ticketing and server capabilities were promised with an estimated budget of Rs 10 crore. The site was to be improved to handle 60-65,000 tickets with the help of servers upgraded to 64GB RAM. This would allow 80 lakh concurrent connections compared to the current 10 lakh. While all this sounds good, we think with the growing popularity and feasibility of online booking, the number of people opting for online booking will increase year by year. IRCTC can currently handle 2000 tatkal bookings per minute while the latest proposed improvement is around 7,200 tickets per minute. Now, it isn't clear what upgrades IRCTC has planned for its servers, but here are a few things that could help resolve the long waiting hours for IRCTC tatkal consumers and prepare other e-ticketing sites for future. Role of servers and why they cannot handle the load In general, e-ticketing has two main aspects – one part includes networking, interconnectivity and servers while the other part includes convenient billing system made available to consumers. While the technical aspect has to ensure that complete operation or process is smooth and swift, there should also be ample of easy payment options given to users. The server helps to form secure connection for each consumer who logs into the site. e-ticketing companies design these servers to handle a particular number of connections, but in the past couple of years, this number has been growing with each passing day. During the tatkal booking 2-hour window, the server has to handle multiple times the number of connections than it can manage. So, if you are disconnected, you have to wait until there is room for you, which is possible only if someone else gets disconnected. Moreover, a failure at one step means the person has to begin right from the start. Once disconnected, start right from login Raj Jadhav, VP Solutions Consulting, Tech-support and IT, D-Link, tell us that one also has to understand the Indian consumer behaviour as there are many people accessing the site just to check the rates, view the ticketing process or likewise; the server capability has been designed considering such bogus connections too. So while designing the server, it is important to consider these additional connections that your server will have to handle. He explains, “The machine won’t understand if you are there to genuinely buy the ticket or simply view the process or check rates. As soon as you log into the e-ticketing site, a secure connection is formed, genuine or not. So, if the site is capable of handling for instance 1 lakh connections then, maybe some percent of connections are not genuine but the site has to still maintain them.” According to him, another aspect that should be considered is the kind of relationship these e-ticketing companies have with banks or telecom companies to provide the right communication infrastructure and banking response so that the transaction is completed on time. The system understands technicalities and it has certain wait time after which it will get disconnected. Improving server infrastructure Raj Jadhav says that e-ticketing companies like IRCTC can spruce up the server capability by deploying L4 to L7 (Layer 4 to Layer 7) infrastructure. This infrastructure allows to instantly add new servers. For instance, if a server experiences a surge in traffic, then immediately one will be able to add another server, which will take care of the extra load. With this system in place, the IT team manager can decide and share the load on multiple servers, i.e., server load balancing. A job can be allocated per server; for instance, one server can handle only 300 tickets. If the server is overloaded, then one can add another server that can handle 200-300 transactions per minute. This is something that sites like Facbeook and Twitter are doing – the only difference is e-ticketing is done over a secure connection. This is one reason why we don’t see these sites complaining about overloaded servers. One should have the feasibility or capability to keep on adding servers. Flexible booking timings A little flexibility in the tatkal booking timings can also help. For instance, there can be a 1-hour tatkal window for trains leaving before 2 AM, while another 1-hour window for trains leaving after 2 PM. This way the concentration of the load will be distributed over two hours. Cloud server comes to the rescue In case of IRCTC, overcrowded servers are the biggest challenge they are facing. Amazon may sell 13.5 million items worldwide on a record-breaking day, while Indian Railways consistently sells more than 1 lakh tickets everyday. Another possible issue could be all their servers are concentrated in one region. For instance, a person from western India is booking the ticket, but the main server is in Delhi - this could also cause delays. The key solution these days is cloud computing. If they have cloud computing infrastructure in place, then Delhi customers can connect to Delhi servers and Mumbai customers can connect to the western server, wherever it is placed.

Monday, December 12, 2011

Tech Disappointments HTC Flyer




The Flyer was HTC’s first ever foray into the tablet segment, but they messed it up by pricing it ridiculously high. But that wasn’t the only issue, the tablet as powerful as it was on paper, failed to translate that power in the real world due to which it suffered in video playback. When we tested it, the Sense UI ran super smooth, but the Flyer seemed to struggle with video playback. The stock player couldn’t playback bog standard SD files smoothly, let alone 720p. This was fixable by a third party app, but then you’d lose the SRS sound enhancements, which made a big difference in the audio quality. You’d think a 1.5GHz processor would be able to playback HD files with ease, but sadly that’s not the case.

It's back to the drawing board for HTC



Now, with the recent price drop and the Honeycomb update rolling out, perhaps it does seem a bit more appealing.

Monday, July 4, 2011

New Android-powered set by Spice mi270


Spice introduced the new Mi270 mobile phone in India. The phone is a dual SIM compatible device and is powered by Android 2.2 Froyo OS.
The phone features 2.8 inches of TFT touch screen display in the phone that supports 240 X 320 pixel resolution for clear and bright content viewing. The microSD card slot in Spice Mi270 enables the user to expand the external memory space by up to 16G so that there is enough storage space for all your needed data.
For connectivity the mobile comes packed with variety of options including GPRS, EDGE, WiFi, Bluetooth 2.1 with A2DP+EDR and USB. The 2 MP camera of the phone is capable of capturing acceptable quality images and videos as well.
Additional specifications that comes packed with Spice Mi270 include Push Mail Facility, FM Radio, access to social networking sites, multi format music player, 1000 mAh battery and others.

Specifications:
Dual Sim (GSM+GSM)
3G/HSDPA, GSM/EDGE
3.7” inch Touchscreen Display
MediaTek 600 Mhz Processor
up to 32GB Memory Card Slot
3MP or 5MP Front Camera + Rear VGA Camera
Wi-Fi, Bluetooth
Multimedia Players (Audio / Video)
Price:
The mobile is available for the price of Rs 9000/- in leading mobile stores.

Know Tech in hindi-www.hindi2tech.com

Hindi Tech - तकनीक हिंदी में

Monday, January 10, 2011

A play station by SONY Ericsson - Centric Handset


Sony has recently made an announcement about the launch of its latest handset called Sony Ericsson Xperia Play which will be a Sony PlayStation gaming centric handset with impressive list of features. This upcoming handset will surely prove to be a treat for all the gaming lovers.

It is expected that the handset will run on Android 2.3 Gingerbread OS, will be powered by 1GHz of Qualcomm CPU and will feature Adreno 205 GPU with 512MB of RAM. The 4 inches of LCD touch screen display in the phone will be capable of delivering FWVGA resolution of 854 X 480 pixels for bright and clear contents.

The external memory of the handset can be expanded through microSD card slot for providing enough storage space for all your needed data. A 5MP camera will come packed in the body of the handset that will be capable of capturing 720p videos along with good quality images.

Other features that are expected to come loaded in Sony Ericsson Xperia Play include 1500 mAh battery, microUSB port, 3.5mm audio jack, noise cancellation second microphone, music player, video player, Bluetooth, WiFi and 3G.

The availability and the price of the phone are not yet known.

Tuesday, May 18, 2010

Some basic terms to Know

3
3G:Third-generation mobile communication system. Generic name for mobile network/ service based on the IMT-2000 family of global standards. [ITU(1)]

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A

ADSL:Asynchronous Digital Subscriber Line. ADSL variant in which traffic is transmitted at different rates in different directions (upstream and downstream). [TMG]
Amplifier:A device used to increase the strength of electronic signals Telecommons
Analogue:Communications signal represented by the pitch and the volume of a voice. [ITU(1)]
Antena: The device that concentrates a beam of electromagnetic waves to a focal point so as to send /receive signals. [Telecommons]
Aperture: The effective cross sectional area of the antenna. The larger the aperture, the stronger the signal the antenna receives or transmits. [Telecommons]
ATM: "Asynchronous Transfer Mode. A very fast data transmission methods. It dramatically allocates bandwidth and uses a fix-ed size packet." [ITU(1)]

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B

Backbone: The main line that ties networks, phone systems or computers together. It's like the human skeleton, with many small connections (called nodes or terminals), Branching off from the backbone. [Telecommons]
Bandwidth: The range of frequencies available to be occupied by signals. In analogue systems it is measured in terms of Hertz (Hz) and in digital systems in bit/s per second (bit/s). The higher the bandwidth, the greater the amount of information that can be transmitted in a given time. High bandwidth channels are referred to as broadband which typically means 1.5/2.0 Mbit/s or higher. [ITU(2)]
Bit rate: The speed at which bits are transmitted usually expressed in bits per second (bps). [Telecommons]
Broadband: Transmission capacity with sufficient bandwidth to permit combined provision of voice, data and video. According to ITU report, it refers to DSL and cable modem services with band width greater than 128kbps in at least one direction. [ITU(1)]

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C

Cable: A cable is one or more insulated wires inside a common protective wrapper. [Telecommons]
Carrier: A company that owns a transmission medium and rents, leases or sells portions for a set tariff. [Telecommons]
CATV: The transmission, usually for a fee, of television signals, including signals that originate at over-the- air television stations, to consumers on a wired network. [Telecommons]
CDMA: Code Division Multiple Access. A technology for digital transmission of radio signals based on spread spectrum techniques where each voice or data call uses the whole radio band and is assigned a unique code. [ITU(3)]
Channel: An electrical transmission path between two or more stations. Channels may be furnished by wire, radio, fiber or a combination of all three. [Telecommons]
Circuit: A physical transmission path between two or more points. [Telecommons]
Communication satellite: A device sent up into space used to relay telecommunications signals between two or more points. The main advantage of satellites is the relatively low cost of the earth station equipment needed to link up with satellites compared to stringing wire or fiber optic cable over very long distances. [Telecommons]
Competition: Refers to a situation in a market in which firms or sellers independently strive for the patronage of buyers in order to achieve a particular business objective, e.g., profits, sales and/or market share. [OECD]
Convergence: Refers to two different trends: - convergence between the broadcasting and telecommunications sectors. Advances in technology make it possible to use different media (cable networks, terrestrial and satellite radio relay systems, computer terminals and television sets) to carry and process all kinds of information and services, including sound, images and data. This type of convergence is due to a revolution in technology (digitisation). It has economic and regulatory implications. - fixed/mobile convergence. Increasingly similar technologies are used and services provided by fixed telephone and mobile telephone systems. This type of convergence opens up prospects for operators to propose the same services to all users, regardless of the technology or networks they use. [Autorie de regulation des telecommunications]
Cost-based pricing: "The general principle of charging for services in relation to the cost of providing these services. [WTO]
Coverage: Refers to the area on earth capable of effectively receiving transmission of network. Often use for cellular or satellite network. [ITU(1)]

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D

Dark fiber: A bare capacity and does not involve any of the electronics necessary to transmit or receive signals over that capacity. [FCC]
Demodulation: Demodulation converts data back and forth between digital and analogue. [Telecommons]
Digital: Any type of information that can be output, transmitted and interpreted as individual bits of binary information (the use of the numbers 0 and 1), using electrical or electromagnetic signals that can be modulated to convey their specific content. A TV picture will be more like a rectangle and have up to 1,080 lines of resolution, producing a crisper picture. [FCC]
Digital divide: "Refers to the gap between individuals, households, businesses and geographic areas at different socio-economic levels with regard to both their opportunities to access information and communication technologies (ICTs) and to their use of the Internet for a wide variety of activities. The digital divide reflects various differences among and within countries. [OECD]
Digital switched network (DSN): A high-speed digital switched public network allows access to a wide range of services such as telecommuting, video conferencing, telemedicine, distance learning, etc. Telecommons
Download: To receive data from another computer into your computer. The opposite is called "Upload". [FCC]
DSL: "Digital Subscriber Line. A high-speed Internet connection using telephone lines." [ITU(1)]
Duplex Transmission : Simultaneous two-way(transmit and receive) independent transmission. [Telecommons]

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E

Earth station: The antenna, receivers, transmitters and other equipment needed on the ground to transmit and receive satellite communication signals. [Telecommons]
E-Commerce: "Electronic commerce. Refers to commercial transactions occurring over open networks, such as the Internet. Both business-to-business and business-to-consumer transactions are included." [OECD]
E-Government: Refers to the use of new information and communication technologies (ICTs) by governments as applied to the full range of government functions. In particular, the networking potential offered by the Internet and related technologies has the potential to transform the structures and operation of government. [OECD]
Electronic data interchange (EDI): "Electronic Data Interchange. Transmission of information between computers using standardized electronic versions of common business documents." [ITU(1)]
EMS: Enhanced Messaging Service. EMS is a text service allowing mobile users to send and receive short text messages from other mobile and PC users. Compared to SMS, EMS includes additional features such the transmission of simple melodies, graphics, sounds, animations and modified text as an integrated message. [ITU(2)]
E-strategies: The national information infrastructure strategies arise from the Internet and the convergence of telecommunications ,computing and broadcasting. [The World Bank]
Exchange: A basic unit for the administration of telephone service, which generally includes everyone in one town plus adjacent areas. There can be more than one exchange within a larger town or city. The territory served by an exchange, within which local rates apply, is known as the exchange area or local service area. [Telecommons]

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F

Fiber optics transmission system (FOTS): A system which uses glass fibers the size of human hairs through which light is transmitted. By changing the patterns of light sent through the lines, information is transmitted. These signals are read by light-sensitive devices. Fiber optics generally allow for a much greater speed and bandwidth than transmitting over regular wires, microwaves or satellite. [Telecommons]
Firewall: A hardware- and/or software-based system that is used as an interface between the internet and a computer system to monitor and filter incoming and outgoing communications. [OECD]
Frame Relay: A high-speed data service. Telecommons
Frequency: The rate at which an electrical current alternates, usually measured in Hertz. It is also used to refer to a location on the radio frequency spectrum, such as 800, 900 or 1800 Mhz. [ITU(1)]

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G

Gateway: An interface between some external source of information and a World Wide Web server. In this instance a gateway is a web enabled search mechanism which allows users to search a distributed network of directory nodes. [OECD]
Geographical Information Systems (GIS): A geographical information system (GIS) can be seen as a system of hardware, software and procedures designed to support the capture, management, manipulation, analysis, modeling and display of spatially referenced data. [OECD]
GSM: "Global Systems for Mobile communications. European-developed digital mobile cellular standard." [ITU(3)]

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H

High speed: Usually refers to data communications systems operating at speeds above 9,600 bps. [Telecommons]
Host: Internet access provider's computer. You may use one of its hard- wired terminals, if you are at an institution with a mainframe computer connected directly to the Internet, or you may dial up via modem to connect with the Internet access provider's host computer. [FCC]
Hub: Central point for the collection, sorting, transshipment and distribution of goods for a particular area. [FCC]
Hyper-Text Mark-Up Language(HTML): The programming language used to design and present computer sites on the Internet in a graphical user interface fashion. HTML is the language used by programmers on the Internet as part of the World Wide Web project. [OECD]
Hyper-Text Transport Protocol(HTTP): The method for moving "hypertext" files across the Internet. Requires an HTTP program at one end and a server at the other. [FCC]

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I

ICT Applications: Hardware and software solutions that utilize ICT to meet business, public administration, social and other goals; there are also sometimes referred to as informatics. [The World Bank]
IMT 2000: Worldwide standards for third generation mobile systems which enable mobility services to be improved. [Autorie de regulation des telecommunications]
IMT 2001: International Mobile Telecommunications-2000. The International Telecommunications Union (ITU) recommendation for 3G networks. [TMG]
Informatics: It deals with ICT as a theme, a way of doing things (e.g. ICT in Education, e-government). [The World Bank]
Information and Communication Infrastructure (ICI): Refers to physical telecommunications systems and networks (cellar, broadcast, cable, satellite, postal) and the services that utilize them (Internet, voice, mail, radio, and television). [The World Bank]
Information and Communication Technologies (ICT): Consists of the hardware, software, networks, and media for the collection, storage, processing, transmission and presentation of information (voice, data, text, images), as well as related services. ICT can be split into ICI and IT. [The World Bank]
Information Technology (IT): Refers to the hardware and software of information collection, storage, processing, and presentation. [The World Bank]
Interconnection: The physical connection of telecommunication networks owned by two different operators. [ITU(1)]
Interconnection charge: A charge levied by network operators on other service providers to recover the costs of the interconnection facilities (including the hardware and software for routing, signaling, and other basic service functions) provided by the network operators. [WTO]
Interface: The point at which two systems or pieces of equipment are connected.[Telecommons]
IP: Internet Protocol.[ ITU(1)]
IP address: Address identifying a terminal connected to the Internet network. [Autorie de regulation des telecommunications]
IP telephony: The use of IP technology to transfer voice and data. [Autorie de regulation des telecommunications]
ISDN: Integrated Services Digital Network. A digital switched network supporting transmission of voice, data and images over conventional telephone lines. [ITU(1)]
ISP: Internet Service Provider. [ITU(1)]

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K

Knowledge economy: Refers to the use of knowledge to produce economic benefits. The phrase came to prominence in New Zealand in the mid-to late-1990s as a way of referring to the manner in which various high-technology businesses, especially computer software, telecommunications and virtual services, as well as educational and research institutions, can contribute to a country's economy. [The World Bank]
Knowledge management: A concept in which an enterprise gathers, organizes, shares, and analyzes its knowledge in terms of resources, documents, and people skills. Knowledge management involves data mining and some method of operation to push information to users. [The World Bank]

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L

Leased line: A telecommunications channel leased between two or more points at a flat monthly rate. Also called dedicated or private line. [Telecommons]
Local Area Network (LAN): The electronic linking, by cable or infrared beams, of several or all computer workstations within a specific physical area to a file server or storage and processing device. It allows all users connected to the network to access the server's software and data files and to exchange electronic messages via an electronic mail system. Frequently includes printers, scanners, and other related equipment. [OECD]
Local loop: The connection that runs from the subscriber's telephone exchange equipment. This term is synonymous with the term fixed line. [ITU(1)]

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M

Microwave transmission system: A high-capacity transmission system that sends information using high-frequency radio signals called microwaves. Originally, microwaves systems offered only analogue transmission, but today they are commonly digital. [Telecommons]
Modem: Computers generate data in digital form. To send this, this digital stuff over an analogue phone line, the data has not be converted. [Telecommons]
Multiplexing: Techniques that allow a number of simultaneous transmissions over a single circuit so as to accommodate multiple users or uses. [Telecommons]
Multipoint: A line or channel connecting more than two specific service points. [Telecommons]

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N

Network: Combination of telecommunications resources, for example, exchanges, wire links (copper cable, optical fiber) and terrestrial or satellite radio transmission links. [Autorie de regulation des telecommunications]
Number portability: Possibility for subscribers to retain their telephone number when changing local loop operator or when changing geographic location or local loop operator, or both. [Autorie de regulation des telecommunications]

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P

Packet: A group of digital bits put together in a bundle or packet to make transmission faster. One little packet includes not only your data but also control information such as a source and destination address and an identification number. [Telecommons]
Packet Switching: Technique where bit grouped packets are specifically routed to their destinations based on the availability of transmission paths. [Telecommons]
Penetration: A measurement of access to telecommunications. It is usually calculated by dividing the number of subscribers by the population, and multiplying by 100. Also referred to as density. [TMG]
Portals: A portal is the term given to that part of a Website which acts as a gateway, or launch point, through which users navigate the World Wide Web. [OECD]
Private Branch Exchanger (PBX): A private telephone switch that establishes voice-grade circuits over tie-lines between individual users and the switched network. [Telecommons]
Private Line Service: Dedicated telecommunications channels provided between two points or switched among multiple points. Privately leased for high-volume voice, data, audio, or video transmissions. [FCC]
Private Networks: Any network used to communicate within an organization (as distinct from providing service to the public) or to supply such communications to organizations, based on a configuration of own or leased facilities. The term includes networks used by private companies, state enterprises, or government entities. [OECD]
Protocol: A formal set of conventions governing how communication systems can talk to each other. [Telecommons]
Publicly Switched Telephone Network (PSTN): The world-wide dial-up telephone network or portion of that network. Whatever system you own should be linked somehow to the PSTN so you can make long distance phone calls, or go on the Internet. [ITU(3)]

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R

Reach: Refers to the availability of a service in the community. It is the number of homes to which the services is available regardless of whether or not residents choose to subscribe. [FCC]
Router: A special switching system in space that receives radio communication signs, from earth stations on earth and then retransmits them to earth location. [Telecommons]

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S

Server: A computer that has been set up to provide certain services to other computers (clients), for instance, a Web server is a central repository of data, software or client for the World Wide Web. [OECD]
Signal: The combination of waves that travel along a transmission channel and act on the receiving unit. [Telecommons]
SMS: Short message Service. A service available on digital networks, typically enabling messages with up to 160 characters to be sent or received via the message center of a network operator to a subscriber's mobile phone. [ITU(2)]
Spectrum Management: The spectrum or range of radio frequencies available for communication, industrial, and other uses. Frequency bands or segments are assigned to various categories of users for specific purposes, such as commercial radio and television, terrestrial microwave links, satellites, and police. At the international level this is done by the International Frequency Registration Board (IFRB) of the International Telecommunication Union (ITU). Individual national regulatory agencies monitor the occupancy of the radio spectrum and allocate frequencies to individual users or a groups of users so as to enable a large number of services to operate within specified limits of interference. [WTO]
Spectrum(Radio): The radio frequency spectrum of hertzian waves used as a transmission medium for cellular radio, radiopaging, satellite communication, over-the-air broadcasting and other services. [ITU(1)]
SSL: Secure Socket Layer. A programmed layer created by Netscape for managing the security of message transmissions in a network. SSL uses a public-and -private key encryption system, which also includes the use of a digital certificate. [ITU(2])
Subscription: A licensing agreement in which the licensee makes a payment to the service provider for access to ICTs. [TMG]

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T

Tariff / Unbundled tariff: Tariffs are the schedule of rates and regulations governing the provision of telecommunications services. Unbundling of tariffs is where each component of a communications service or product is priced separately, so that customers may select only those components needed and be charged accordingly." [WTO]
TCP/IP: Transmission control protocol/ Internet protocol. [ITU(1)]
Transmission system Local exchange carrier: A system to transfer information from one location to another. It could be copper wire, fiber optic lines, or radio waves.[Telecommons]
Transponder: An electronic device on a satellite used to boost or amplify signals before sending them back to earth. It can receives an uplinks signal at one frequency, convert its frequency, amplifies it, and transmits it to the ground. Satellites generally have 10-40 transponders. [Telecommons]

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U

Universal Access: Refers to reasonable access to ICTs for all. Includes universal service for those that can afford individual ICT service and widespread provision of ICTs within a reasonable distance for others. Stastically measured as the percentage of the population covered by information and communication technologies. [ITU(1)]
Universal Service: Refers to availability and widespread affordability of ICTs. The level of universal services is statistically measured as the percentage of households with ICTs. [ITU(1)]
Uplink: The transmission of signals from an earth station to a satellite. [Telecommons]

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V

Very Small Aperture Terminal: An earth station with a small antenna of usually 0.9-1.8 meter (3-6 foot) diameter. Typically used in point-to-multipoint data networks.[Telecommons]

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W

Wide Area Network (WAN): A computer network that connects computers over large distances by means of high-speed communications links or satellites. [OECD]
Wireless communication: Sending signals without a physical connection using technologies such as cordless telephones, cellular telephones or microwaves. [Telecommons]
WWW: World Wide Web. The World Wide Web is a part of the Internet designed to allow easier navigation of the network through the use of graphical user interfaces and hypertext links between different addresses. [OECD]

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X

XML: extensible markup language. [OECD]

What is SDH

SDH (Synchronous Digital Hierarchy) is an international standard for high speed
telecommunication over optical/electical networks which can transport digital signals
in variable capacities. It is a synchronous system which intend to provide a more flexible , yet simple
network infrastructure.

SDH (and its American variant- SONET) emerged from standard bodies somewhere around 1990.
these two standards create a revolution in the communication networks based on optical fibers ,
in their cost and performance.


before SDH

The development of digital transmission systems started In the early 70s , and was based on
the Pulse Code Modulation (PCM) method.

In the early 80's digital systems became more and more complex , yet there was huge
demand for some features that were not supported by the existing systems.
The demand was mainly to high order multiplexing through a hierarchy of increasing bit
rates up to 140 Mbps or 565 Mbps in Europe.
The problem was the high cost of bandwidth and digital devices. The solution that was
created then , was a multiplexing technique , allowed for the combining of slightly
non synchronous rates, referred to as plesiochronous*, which lead to the term plesiochronous digital hierarchy (PDH).

*plesiochronous - "almost synchronous , because bits are stuffed into the frames as padding and the
calls location varies slightly - jitters - from frame to frame".

multiplexing with PDH


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why using SDH ?

Although PDH was A breakthrough in the digital transmission systems , it has a lot of
weaknesses :

  • No world standard on digital format (three incompatible regional standards - European, North american and Japanese).
  • No world standard for optical interfaces. Networking is impossible at the optical level.
  • Rigid asynchronous multiplexing structure.
  • Limited management capability.
Because of PDH disadvantages, It was obvious That a new multiplexing method is needed.
The new method was called SDH.


multiplexing with SDH








SDH has a lot of advantages:

  • First world standard in digital format.
  • First optical Interfaces.
  • Transversal compatibility reduces networking cost. Multivendor environment drives price down
  • Flexible synchronous multiplexing structure .
  • Easy and cost-efficient traffic add-and-drop and cross connect capability.
  • Reduced number of back-to-back interfaces improve network reliability and serviceability.
  • Powerful management capability.
  • New network architecture. Highly flexible and survivable self healing rings available.
  • Backward and forward compatibility: Backward compatibility to existing PDH
    Forward compatibility to future B-ISDN, etc.
The following Graph Shows the differences between PDH and SDH Prices:








SDH is based on byte interleaving and not bit interleaving , as PDH was based on.
The bit rate increased from 64 Kbps in PDH to 1.5 - 2 Mbps in SDH.

SDH/SONET Vs. PDH rates


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when do we use SDH ?

  • When networks need to increase capacity , SDH simply acts as a means of increasing transmission capacity.
  • When networks need to improve flexibility , to provide services quickly or to respond to new change more rapidly.
  • when networks need to improve survivability for important user services.
  • when networks need to reduce operation costs , which are becoming a heavy burden .


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layers model of SDH

the following scheme describes the different layers of SDH , according to the OSI model :




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standards

  • SDH has been standardized by ITU-T in 1988.
  • In November 1988 the first SDH standards were approved.
  • In 1989 , the CCITT (International Consultative Committee on Telephony & Telegraphy) had published in its "Blue book" recommendations G.707 , G.708 & G.709 covering the SDH standards.
G.702 - Digital Hierarchy Bit Rates
G.703 - Physical/Electrical Characteristics of Hierarchical Digital
Interfaces
G.707 - SDH Bit Rates
G.708 - Network Node Interface for the SDH
G.709 - Synchronous Multiplexing Structure
G.773 - Protocol Suites for Q Interfaces for Management of
Transmission Systems
G.781 - (Formerly G.smux-1) Structure of Recommendations on
Multiplexing Equipment for the SDH
G.782 - (Formerly G.smux-2) Types and General Characteristics
of SDH Multiplexing Equipment
G.783 - (Formerly G.smux-3) Characteristics of SDH Multiplexing
Equipment Functional Blocks
G.784 - (Formerly Gsmux-4) SDH Management

SDH Elements

The most common SDH elements are :


The terminal multiplexer is used to multiplex local tributaries (low rate)
to the stm-N (high rate) aggregate. The terminal is used in the chain
topology as an end element.


The regenerator is used to regenerate the (high rate) stm-N in case that the
distance between two sites is longer than the transmitter can carry.

The Add And Drop Multiplexer (ADM) passes the (high rate) stm-N through
from his one side to the other and has the ability to drop or add any (low rate)
tributary. The ADM used in all topologies.


The synchronous digital cross connect receives several (high rate) stm-N and switches
any of their (low rate) tributaries between them. It is used to connect between
several topologies.

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SDH Topologies


The linear bus (chain) topology used when there is no need for protection
and the demography of the sites is linear.


The ring topology is the most common and known of the sdh topologies
it allows great network flexibility and protection.


The mesh topology allows even the most paranoid network manager
to sleep well at nights because of the flexibility and redundancy that it
gives.


The Star topology is used for connecting far and less important sites
to the network.

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Usage of SDH elements in SDH Topologies


The Terminal multiplexer can be used to connect two sites in a high rate
connection .


The Add And Drop Multiplexer (ADM) is used to build the chain topologies in the above picture.
At the ends of the chain usually a Terminal Multiplexer is connected.


The Add And Drop Multiplexer (ADM) is used to build the ring topology.
At each site we have the ability to add & drop certain tributaries.

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SDH Protection

The SDH gives the ability to create topologies with protection for the data transferred.
Following are some examples for protected ring topologies.


At this picture we can see Dual Unidirectional Ring . The normal data flow is
according to ring A (red). Ring B (blue) carries unprotected data which is lost in
case of breakdown or it carries no data at all.


In case of breakdown rings A & B become one ring without the broken segment.


The Bi-directional Ring allows data flow in both directions. For example if data from one
of the sites has to reach a site which is next to the left of the origin site it will flow to the left
instead of doing a whole cycle to the right.


In case of breakdown some of the data is lost and the important data is
switched. For example if data from a site should flow to its destination through
the broken segment, it will be switched to the other side instead.

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SDH Management

SDH has enhanced management capabilities :

  • Alarm/Event Management
  • Configuration Management
  • Performance Management
  • Access and Security Management

Depicted above is a Management Station connected to a SDH ring through site 1 which contains the
gateway element. The Gateway elements receives the status of all the other elements in the net through
the special fields that exists in the SDH protocol (in band).

SDH vs. PDH

Few years ago the common way to build a backbone network that supplies broadband communication
to the suppliers (BT, Bezeq etc.) was a PDH network. The topology of a PDH network is the Mesh
topology where every multiplexer in each site worked with its own clock. In order to synchronize between two multiplexers that works together, usually the transmission was made according to the local clock and the reception was made according to the recovered clock that was recovered from the received data.
The PDH contains 4 basic bit rates:

  • E1 - 2.048 Mbit/Sec
  • E2 - 8.448 Mbit/Sec
  • E3 - 34.368 Mbit/Sec
  • E4 - 139.264 Mbit/Sec
The En is the result of multiplextion of 4 En-1.

The fact that each of the multiplexers transmits according to its own clock creates a problem when we need to multiplex several transmitted data streams, the problem is that we can't decide which clock to choose for the multiplexing. If we will choose a fast clock we will not have enough data to put in the frame from a slower incoming data stream (we will get empty spaces in the frame), from the other hand if we will choose a slow clock the data at the faster incoming stream will be lost.

This problem was solved with a stuffing algorithm, which is implemented by using a fast clock, that allows transmission of indication bits and stuff bits. In case that the data is slower then "expected", the indication bits indicate that the following stuff bits are "garbage" and if the data is faster then "expected" the indication bits indicate that the following stuff bits are data. This is the reason why 4 * En-1 <>

There are two common ways to connect between two PDH sites. The first is by Radio Frequency (RF)
and the other is by Electrical Signal over copper cable. since we cant afford to many cables or frequencies
usually E3 or E4 is used.
In order to transmit E1 (a very common data rate) we need 2 or 3 levels of multiplexing, this means that
in a full E4 constellation 1+4+16=25 multiplexers are needed.
Further more there is no inband management in the PDH protocol if we need to know the status of 1 of the multiplexers, or if we need to change the route of 1 of the trails we have to go to the site or build an
outside network that allows us to manage the PDH network.

In the latest years a new protocol was defined, this new protocol was aimed to provide all the PDH
capabilities and solve some of the PDH weaknesses that are mentioned above. This new protocol is the SDH.
The SDH network works with a single central clock that synchronizes all the elements in the network.
The SDH contains the following bit rates:

  • STM1 - 155 Mbit/Sec
  • STM4 - 622 Mbit/Sec
  • STM16 - 2.5 Gbit/Sec
  • STM64 - 10 Gbit/Sec
  • Etc.
In order to have the ability to connect a low rate PDH stream (E1, E3 etc.), an improved stuffing algorithm is used.
The SDH protocol enables transmitting any of the PDH bit rates directly by mapping it to the STM-n frame, that gives the user the flexibility to transmit any configuration of tributary rates using only one multiplexing element, depicted bellow the difference between the SDH network element and the PDH network elements that need to transmit different tributary rates.

PDH network elements.

The inband management functionality enables the SDH network manager to receive information about
the quality of service, the damaged elements (if there are any) and gives the manager the option to change the network configuration from a remote site. In order to be able to do the same things with the PDH network, one should build another separated network for the management and the remote control.

The ability to multiplex any of the standard bit rates into the STM-n frame is possible due to the complicated containers structure of the STM-n frame as depicted bellow.

In order to map an E1(2.048 Mbit/Sec) into the STM-n frame we have to create a TU-12 stream which is a low rate stream that is synchronized to the SDH network clock. The TU-12 is composed of the E1 data, indication bits, stuffing bits, management bits and a direct pointer to the E1 frame.
The TUG-2 is a structure that can be composed of 3 TU-12s (3 E1s), or 4 TU-11s (4 T1s), or 1 TU-2 (1 T2). This structure gives the STM frame its flexibility to multiplex different rates directly into the STM-n frame (impossible in the PDH protocol). The next stage is mapping 7 TUG-2s into 1 VC-3 or into 1 TUG-3 and so on according to the flow chart.

This method of multiplexing allow us to directly map the T1, T2, T3 (American standards) and the E1, E2, E3, E4 (European standards) into the STM-n frame.

Each time we map lower rate streams into a higher rate structure we add pointers to a fixed point in the lower rate streams, so we can directly extract the relevant information with out demultiplexing the all high rate stream.

When stuffing is needed the pointer to the fixed location is changed according to the direction of the stuffing, this is the improvement of stuffing algorithm used in the PDH .



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SDH Frame Structure

The STM-n frame structure is best represented as a rectangle of 9 x 270xN.
The 9xN first columns are the frame header and the rest of the frame is the inner structure data (including the data, indication bits, stuff bits, pointers and management).

The STM-n frame is usually transmitted over an optical fiber. The frame is transmitted row by row (first is transmitted the first row then the second and so on). At the beginning of each frame a synchronized bytes A1A2 are transmitted .


The multiplexing method of 4 STM-n streams into a STM-nx4 is an interleaving of the STM-n streams to produce the STM-nx4 stream. The method is shown in the next picture for producing STM-4 from 4 STM-1 streams.

After interleaving we get a higher order stream that in its rectangular form all the low order STM streams are placed as its columns which makes it easier to find each of them in the bigger frame.





SDH - In the future
The modern lifestyle requires high speed communication applications.
SDH provides large bandwidth that can meet the needs of this applications.
Here are some of the needs and there solutions.

Future of the private circuits

Demands:

  • In the future there will be an increasment in the demand for private circuits (leased line traffic) and the associated capacity increase in the trunk network.
  • Mega stream services will be available for end users.
SDH solution:
  • SDH networks have flexible routing ability for circuit protection thus allowing rapid circuit reallocation and high circuit availability.
Future of the Broadband ISDN

Demands:

  • Growing demand for non voice broadband services which require a variable bandwidth such as video signal transmission, video conferencing, remote data base access and high speed multimedia file transfer.
SDH solution:
  • ATM has been chosen by CCITT to be the target transfer mode for B-ISDN services, ATM cells can be easily transported in the SDH frame.
The Aothers :
  1. Galit Rozenboim
  2. Hay Shaul
  3. Shay Turel
  4. Arik Litinsky
  5. Jacob Rutstein
  6. Itsik Shalom


Sunday, November 15, 2009

Now u can Transfer ur money vi ur cellphone


Tata Indicom, in association with Corporation Bank and PayMate, has launched 'Green Money Transfer'- a person-to-person mobile money transfer service. The transfer of funds via mobile will be facilitated by PayMate's technology, Corporation Bank's banking system and Tata's PCO and True Value Shop (TVS) network.

Customers can register for this service at a Green TATA PCO, TVS or with Corporation Bank. Upon registration, they will receive an mPIN to enable them to authorise the transaction.

Example:

1. A sender in Mumbai goes to a Green Tata PCO or TVS and places a request of transferring Rs. 5,000 to his parents in Pune
2. The sender hands over the cash to the Green Tata PCO or TVS. The PCO or TVS triggers an IVR call to the sender
3. The sender enters his mPIN to authorize the transaction and gets a Transaction code on his mobile to be conveyed to the recipient.
4. The recipient goes to the nearest registered Tata PCO or TVS and shares the transaction code.
5. The PCO or TVS triggers an IVR call to the receiver who enters his/her mPIN to verify the transaction
6. Once the verification is done the cash is handed over to recipient

The companies say Green Money transfer service is primarily targeted at the un-banked population of the country by providing them a branchless
banking service to send and receive money effortlessly.

Corporation Bank says this facility is being proposed as an additional service to the rural masses who can now receive remittance in their Bank account instantaneously and draw through Business Correspondents at their own place. This will enable the Bank to augment customer acquisition as well.

This facility has been launched on a pilot basis in Kerala and will later spread to other areas.


Thursday, October 8, 2009

Latest Xtreme Router by D-Link's Shows Pictures


A mere nine months after being announced at CES 2009 in Las Vegas, D-Link is today shipping the Xtreme N Storage router (model DIR-685), probably the first router to incorporate a digital photo frame on the front.

It's only a 3.2-inch color LCD, and not the first router to have a screen, but it is the first that's going to be powered by FrameChannel (which aggregates images from your Flickr, Picasa and Facebook accounts) to display not just pictures but also streaming digital video. The screen will also display the status of the router, Internet connection, and the weather.

A 2.5-inch, 1-terabyte external drive can plug into the side and make the 685 into instant network attached storage (NAS), which can be used to automatically store downloads from BitTorrent. It'll even do FTP file transfers. Or you can plug USB external drives into either of the ports on the router. Or plug in printers or scanners to share them across the network. Plus integrates D-Link's Green tech to use less energy.

What about the actual router part? It's a Wi-Fi Certified, single-band (2.4GHz) 802.11n access point coupled with a four-port Gigabit switch, the usual NAT/SPI firewalls, and Wi-Fi Protected Setup button. It won't come cheap to watch pics or video on a routers, as the 685 costs $299.99 list, but is already selling at Amazon for $249.88.

No. 2 Mobile OS Will be Android (Analyst: Android to become #2 mobile OS by 2012)

According to Gartner analyst Ken Dulaney, Google’s fledgling Android OS has the potential to become the number two mobile operating system (behind Symbian OS) by 2012.

This certainly sounds like a bit of a stretch considering that currently Android is operating on less than 2% of the world’s smartphones. However, in a recent interview with Computerworld, Dulaney said that he sees Google’s open mobile platform expanding to upwards of 14% market penetration over the next 24 months.

gartner-091008

He supports his claim by citing the fact that some 40 new Android-powered devices are expected to be launched over the next year alone.

“Android rises to number two simply because, unlike Apple, they license their OS to multiple OEMs,” Dulaney said. “They have the number 2 OEM, Samsung, and strong players like LG, Motorola, HTC and now Dell. There are others in the works.”

Combine all the new handsets with the enormous draw that Google itself brings to the table, not to mention the anticipated release of Android 2.0, and the fact that Android is open source and has slowly but surely become more attractive to developers, and Dulaney may be on to something here.

Thursday, October 1, 2009

Checkout future technology in coming cells in market

There’s a lot that going on right now in the Mobile world. Nokia World and IFA had some pretty interesting things to showcase in terms of future technology and what to expect. So here’s the latest list on what we can hope to see soon in terms of mobile tech.

Nokia N900
At the top of the list is Nokia’s new mobile computing solution - the N900. This is not like the N800 Series tablets that we’ve seen before. The N900 somehow manages to take things in a new direction. The company has decided to go with an open source Linux-based platform called Maemo. Its ARM Cortex-A8 processor should make it quite a speedy device and OpenGL ES 2.0 graphics acceleration should really make the visual experience pop.


The Nokia N900 will feature –
- a 3.5-inch touch-sensitive widescreen display with an 800 × 480 pixel resolution
- Slide-out QWERTY keyboard and on-screen virtual keyboard as well
- 3G (HSDPA, HSUPA), EDGE/GPRS
- Wi-Fi
- Bluetooth 2.1 with A2DP, USB 2.0 (Micro)
- Integrated GPS with A-GPS support (Ovi Maps preloaded)
- Maemo browser powered by Mozilla technology and Adobe Flash9.4 support
- 32GB of storage, which is expandable up to 48GB via a microSD card
- 3.5mm earphone and handsfree socket (AV out)
- 5 megapixel autofocus camera (Carl Zeiss optics and a Tessar lens) with a Dual LED flash
- Video playback includes XviD support (FINALLY)
- Built-in FM transmitter and radio

LG BL40 Chocolate
LG’s latest in their previous popular chocolate series is the new uber sleek BL40. It’s a large handset with extreme widescreen capabilities. LG has gone with a slightly varied version of their S-Class UI that features multitouch. It appears to be quite a feature rich fashion phone that has a lot to offer users looking for multimedia provisions as well as good looks.


The long and slim (sorry, but there’s no other way to describe it) BL40 comes with -
- a 4.01-inch touchscreen with a widescreen resolution of 345 x 800 pixels
- 3G (HSDPA), EDGE/GPRS
- Wi-Fi
- Bluetooth 2.1 with A2DP, USB 2.0 (Micro)
- Integrated GPS with A-GPS support
- 1GB of storage, which is expandable via a microSD cards
- 3.5mm earphone and handsfree socket (AV out)
- 5 megapixel autofocus camera (Schneider-Kreuznach optics) with an LED flash
- DivX and XviD video support
- Built-in FM transmitter and radio
- Dolby Mobile sound engine


Sony Ericsson Xperia X2
SE’s Xperia 2 or X2, is definitely a better looking version that the previous. It has a slightly more refined and sleeker look, especially draped in black. Hopefully the QWERTY keypad will prove to be a little more comfortable as well. The layout of the handset does seem a little better as well especially with the larger optical trackpad for navigation. This upgrade will be released with Windows Mobile 6.5 (Professional) so we’re looking at a better looking UI as well.


Other features that the X2 will have will include -
- a 3.2-inch touchscreen with resolution of 800 x 480 pixels
- Slide out QWERTY keyboard and Optical trackpad
- 3G (HSDPA, HSUPA), EDGE/GPRS
- Wi-Fi
- Bluetooth 2.1 with A2DP, USB 2.0 (Micro)
- Integrated GPS with A-GPS support
- microSD card support
- 3.5mm earphone and handsfree socket (AV out)
- 8 megapixel autofocus camera with an LED flash
- XviD video support

Samsung Corby
Samsung’s Corby is a cute little handset that is slated to be in the low end touchscreen category. In fact the approximate pricing is about Rs. 10,000 (non-confirmed) which could easily make it one of the cheapest. The TouchWiz UI’s themes are light and colorful just like the handset itself. It has replaceable rear panels and honestly it seems like it’s directed at the female of our species considering the variety of the colors themselves. This is the cheapest handset on the list but it’s something that a market like ours can really look forward to.


The handset will feature -
- a 2.8 inch touchscreen with a 240 × 320 pixel resolution and 256K colors
- EDGE/GPRS
- Bluetooth v2.1 with A2DP
- MicroSD card support
- 2 megapixel camera
- FM radio

HTC Tattoo
In the Android Section, HTC is still the leader in terms of handsets, with a new model being announced on what seems to be a monthly basis. Their latest is the Tattoo, so called because of the interchangeable and customizable panels. The Tattoo is also being marketed as a lower end Android handset directed at the younger segment simply because of this customization option. It’s not going give the Corby a run for its money but for those looking to experience a new OS and the new HTC Sense UI, the Tattoo Android powered handset should fit the bill.


The handset will also feature -
- a 2.8 inch touchscreen with a 240 × 320 pixel resolution and 65K colors
- 3G support EDGE/GPRS
- Wi-Fi
- Bluetooth v2.0 with A2DP, USB 2.0 (mini)
- GPS with A-GPS support
- 3.5mm handsfree socket
- MicroSD card support
- 3 megapixel camera
- FM radio

Motorola CLIQ
It seems like Motorola has risen from the ashes with the announcement of their first Android powered handset the MOTOBLUR. The handset is going to be marketed with today’s fad, Social Networking, as its key element with features that will allow users to always be connected and sync information between their favorite Social Networking sources like Facebook, Twitter, MySpace, Gmail et al. This feature is what the company is calling MOTOBLUR.


This touchscreen handset also features –
- a 3.1-inch touchscreen with resolution of 320 x 480 pixels
- Slide out QWERTY keyboard
- 3G, EDGE/GPRS
- Wi-Fi
- Bluetooth 2.0 with A2DP, USB 2.0 (Micro)
- Integrated GPS with A-GPS support
- microSD card support
- 3.5mm earphone and handsfree socket (AV out)
- 5 megapixel autofocus camera with an LED flash

There’s plenty more that we can expect to see soon, as mobile technology is only getting better with time. I can say much for the designs of some handsets but this sentiment may not be shared with everyone. To each his own. At least we can be assured that there will be something for everyone and that manufacturers have decided that not everyone has the monetary capacity to pay for what they claim to be the best they can offer. So we can finally look forward to seeing some pretty good handsets in the mid range segment equipped with enough features to keep most users satisfied.

Coming soon Samsung's New 12MP camera phone


we were talking about Samsung’s latest 12MP camera phone the SCH-W880 that’s been fitted with a 3X optical zoom lens. More news today says that it’s going to be around the South Korean market for awhile in a CDMA state.

The handset features -
  • 3.3-inch AMOLED touchscreen display (capacitive)
  • 3G capabilities
  • Wi-Fi
  • GPS
  • Bluetooth, USB (micro)
  • 4GB internal memory with microSD card support
The camera is of course the central feature of this handset. It also allows for HD video recording (720p at 30fps). The camera will come with variable aperture settings a Xenon as well as an LED flash. Aside form this being the first ever 12MP camera phone with optical zoom functionality the fact that it records video at the resolution it does is also a first. It seems like it's even designed to look and feel like a digicam with a dial selector for various modes placed on one side.

The European version of the same handset with maybe a few adjustments here and there to suit the crowd will be called the M8920. No word on availability yet.