Wednesday, July 18, 2012

What Is GSM?

GSM, or Global System for Mobile Communications, is a cellular phone protocol that is standard in most parts of the world. Technology experts created the protocol in the 1980s and ’90s to standardize cellular phone service between countries in Europe. GSM phones use subscriber identity module (SIM) cards, which is essential to their function and enable the user to change phones easily. It is a chief competitor to the Code Division Multiple Access (CDMA) protocol.

Technology

Technically, the term GSM refers to second-generation (2G) voice networks that operate based on a combination of time division multiple access (TDMA) and frequency division multiple access (FDMA). TDMA takes the frequency channel the phone uses and divides it into individual bits of time that are assigned to each user. FDMA divides the frequency band into sections and assigns one to each cell phone tower. Towers are typically spread far enough apart so that those using the same frequency do not overlap their areas of coverage.

The term “GSM” is also used to refer to third-generation (3G) technology put into place by the same companies and using the same underlying network. This is actually called Universal Mobile Telecommunications System (UMTS), and uses the Wideband CDMA (W-CDMA) air interface standard in most places. Although they are both spread spectrum technologies, W-CDMA and the standard used by competing CDMA phones (usually CDMA2000) are not compatable.

GSM and CDMA

Although both refer to cellular phone networks, GSM and CDMA differ in the technology that they use. CDMA uses a system in which all signals are sent at the same time, but each is spread across multiple frequencies. Servers assign an individual code to each transmission so that the signals don’t interfere with each other and can be matched up between the sender and receiver.

Originally, the two protocols differed in signal quality, consistency, and voice distortion, among other features. Both methods have been improved, however, and there are few significant differences between the two in terms of call quality. GSM phones are slightly more likely to drop calls as a user moves between cell towers, but they have better coverage in places with a lot of mountains. This technology also allows for voice and data transmission at the same time, which most CDMA phones cannot do.

In some parts of the world, both services are available, but one tends to be more common than the other. Most cellular service providers only use one type of network because it’s very expensive to maintain both types of service. GSM is the older service, and is found in most places around the world, while CDMA is most common in the US and Asia.

SIM Cards

GSM phones use a SIM card, which is a small card with an embedded integrated circuit that stores personal data, the user’s phone number, account information, and contacts. When a user switches phones, exchanging the SIM card from one phone to the other transfers the cell service and phone number, and activates the new phone. The contact list, calendar, and other personal data is usually easily moved between handsets.

Data Transfer Information

The 2G system is capable of data transmission speeds of up to 14.4 kilobits per second (kbps). Originally, not all networks had this capability, but continued advances and improvements in the system have raised speeds. 3G systems, which are designed specifically for mobile Internet and video, can transfer data much more quickly; depending on the interface, theoretical download speeds range from 2 megabits per second (Mbps) to 56 Mbps.

Frequencies

The frequency band used by these phones depends on several factors, including the location and technological changes. For example, in Europe, 2G GSM networks operate in the ranges of 900MHz and 1,800MHz and 3G networks use the 2,100 MHz band. The United States operates on frequencies in the range of 850MHz and 1,900MHz. Many other countries, including Australia and some places in South America, use the 850 MHz range. Most phones are designed for the countries where they are used most often, but a quad-band handset will handle 850, 900, 1,800, and 1,900MHz, and usually work in most areas.

Coverage

As of 2011, most countries from the Arctic region to Antarctica use the GSM protocol. It’s particularly common in Europe, where it originated, and most of the Eastern hemisphere generally, including many developing countries. In the Western hemisphere, the CDMA protocol is more common in the United States and a few other countries. However, many countries, including Canada and Brazil, use GSM.

History

The European Telecommunications Standards Institute (ETSI) created GSM to standardizemobile phone communications among European nations; before this, each country had its own protocol. Standardizing the technology created a large, growing pool of users, and the protocol spread throughout the world. In 2002, approximately 70% of cellular phone clients worldwide used GSM services, while about 12% used CDMA. By early 2010, the GSM Association stated that there were over 4 billion users, and they estimate that there will be over 6 billion by 2015.

Monday, July 16, 2012

Vaio Logo

Do u know the hidden meaning of the Vaio logo.????

Sony Vaio is a well known brand of laptops. But did you know that the name Vaio logo also had a hidden meaning? 

VAIO Originally an acronym of Video Audio Integrated Operation , this was amended to Visual Audio Intelligent Organizer in 2008. the first two letters represent the basic analogue signal. The last two letters look like a 1 and 0, representing the digital signal.

Sunday, March 11, 2012

differentiation formulas

Maths differentiation formulas

Algebric Function

Product Rule And Quotient Rule

Trignomatric Function And Inverse Trignomatric Function

Thanks..

Friday, March 9, 2012

arfa-kareem-arfa-abdul-karim-randhawa

Arfa Kareem

Arfa Abdul Karim Randhawa (Urduارفع کریم رندهاوا‎, 2 February 1995 – 14 January 2012) was a Pakistani student and computer prodigy, who in 2004 at the age of nine years becameMicrosoft Certified Professional (MCP), the youngest in the world until 2008. She was invited by Bill Gates to visit the Microsoft Headquarters in the USA. A science park in Lahore was named after her, the Arfa Software Technology Park.

Arfa Abdul Karim has represented Pakistan on various international forums, and was invited by the Pakistan Information Technology Professionals Forum for a stay of two weeks in Dubai. A dinner reception was hosted for her there, which was attended by the dignitaries of Dubai including the Ambassador of Pakistan. During that trip, Arfa was presented with various awards and gifts including a laptop. In November 2006, Arfa attended the Tech-Ed Developers conference themed Get ahead of the game held in Barcelona on an invitation from Microsoft. She was the only Pakistani among over 5000 developers in that conference



In 2011, at the age of 16, Arfa Abdul Karim was studying at the Lahore Grammar School Paragon Campus in her second year of A-levels. On 22 December 2011 she suffered a cardiac arrest after an epileptic seizure that damaged her brain, and was admitted to Lahore's Combined Military Hospital (CMH) in critical condition.
On 9 January 2012, Bill Gates, chairman of Microsoft, contacted Arfa's parents and directed his doctors to adopt "every kind of measure" for her treatment. Gates set up a special panel of international doctors who remained in contact with her local doctors through teleconference. The panel received details about her illness and provided assistance in diagnosis and treatment. Local doctors dismissed the option of moving Arfa to another hospital owing to her being on a ventilator and in critical condition. Members of Arfa's family have lauded Bill Gates for offering to bear her treatment expenses.
On 13 January 2012, Arfa Abdul Karim started to improve and some parts of her brain showed signs of improvement. Her father, Amjad Abdul Karim Randhawa, said Microsoft had raised the possibility of flying Arfa to the US for care.

On 14 January 2012, 16-year-old Arfa Abdul Karim died at 9:50 PM (Pakistan Standard Time) at Combined Military Hospital (CMH) Lahore.

Wednesday, March 7, 2012

Latest GK India, March 2012

Latest GK India, March 2012


According to 2011 Annual Report of the International Narcotics Control Board (INCB) released globally in Vienna, which country figures high in online dope trade?
- India ( 151 Kg illicit drugs recovered from 152 parcels in 2011)


What are the harsher punishments for traffic violations according to the amended Motor Vehicle Act approved on 1st March, 2012 by government?
For drunken driving the increased fine will range from Rs 2000 to 10,000 and imprisonment from six months to four years. For using mobile phones while driving fine raised to Rs 500 for first offence and Rs 2000 to Rs 5000 for subsequent offences.

India and which other country with long coastline have agreed to hold first ever maritime talks?
- China


Who is appointed new Air Officer Commanding-in-Chief, Training Command, IAF in Bangalore on 1st March,2012?
- Air Marshal Rajinder Singh ( Born in 1953 at Palampur, H.P)


Recently a pin shaped device suspected to be a remote electronic listening device was found in whose office?
- In the office of Defence Minister AK Antony on 16th Feb, 2012


Who has been appointed as the chairman of the monitoring authority that is supervising the investigations into 22 alleged fake encounter killings in Gujarat during 2002-06 by the Supreme Court on 2nd March,2012?
- Retired judge HS Bedi


Who will be Pakistan's new cricket coach? 
- Former Australian batsman Dav Whatmore


Who will be the next Army Chief after General VK Singh, retiring from service on 31st May,2012?
- Lieutenant General Bikram Singh (second-ever Sikh, after General JJ Singh (retd.) to command the 1.3 million strong Indian Army)


When did the Army successfully test fired the 290 Km range BrahMos supersonic cruise missile at the Pokharan range to operationalize the second regiment of the weapon system in service?
- On 4th March, 2012 ( One regiment of the 290 Km range BrahMos consists around 65 missiles, five mobile autonomous launchers on Tatra vehicles and two mobile command posts, among other equipments.) 

Who clinched the first women's Kabaddi World Cup championship title after defeating Iran?
- India