Showing posts with label Technology. Show all posts
Showing posts with label Technology. Show all posts

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.

Sunday, May 1, 2011

Computer & Internet General Awareness Solved Questions March 2011


Technology Questions With Answers March 2011

Here you can download computer Technology  & Internet based  Questions
1 -What is part of a database that holds only one type of information?
A.    Report    B.    Field
C.    Record    D.    File
Answer:  B
2 – ‘OS’ computer abbreviation usually means ?
A.    Order of Significance
B.    Open Software
C.    Operating System
D.    Optical Sensor
Answer-  C
3 – In which decade with the first transatlantic radio broadcast occur?
A.    1850s    B.    1860s
C.    1870s    D.    1900s
Answer: D
4 – Most modern TV’s draw power even if turned off. The circuit the power is used in does what function?
A.    Sound
B.    Remote control
C.    Color balance
D.    High voltage
Answer: B

5 – Which is a type of Electrically-Erasable Programmable Read-Only Memory?
A.    Flash    B.    Flange
C.    Fury    D.    FRAM
Answer:  A
6- ‘.MPG’ extension refers usually to what kind of file?
A.    WordPerfect Document file
B.    MS Office document
C.    Animation/movie file
D.    Image file
Answer: C
7 – Who developed Yahoo?
A.    Dennis Ritchie & Ken Thompson
B.    David Filo & Jerry Yang
C.    Vint Cerf & Robert Kahn
D.    Steve Case & Jeff Bezos
Answer:  B
8 – The most common format for a home video recorder is VHS. VHS stands for…?
A.    Video Home System
B.    Very high speed
C.    Video horizontal standard
D.    Voltage house standard
Answer:  A
9 – What frequency range is the High Frequency band?
A.    100 kHz
B.    1 GHz
C.    30 to 300 MHz
D.    3 to 30 MHz
Answer:  D
10 – In which year was MIDI(dress) introduced?
A.    1987    B.    1983
C.    1973    D.    1977
Answer: B
11 – ‘DB’ computer abbreviation usually means ?
A.    Database
B.    Double Byte
C.    Data Block
D.    Driver Boot
Answer:  A
12 – Who created Pretty Good Privacy (PGP)?
A.    Paul Zimmerman
B.    Tim Berners-Lee
C.    Marc Andreessen
D.    Ken Thompson
Answer:  A
13 – What do we call a network whose elements may be separated by some distance? It usually involves two or more small networks and dedicated high-speed telephone lines.
A.    URL (Universal Resource Locator)
B.    LAN (Local Area Network)
C.    WAN (Wide Area Network)
D.    World Wide Web
Answer:  C
14 – In a color television set using a picture tube a high voltage is used to accelerate electron beams to light the screen. That voltage is about…?
A.    500 volts
B.    5 thousand volts
C.    25 thousand volts
D.    100 thousand volts
Answer:  C
15 – What do we call a collection of two or more computers that are located within a limited distance of each other and that are connected to each other directly or indirectly?
A.    Inernet
B.    Interanet
C.    Local Area Network
D.    Wide Area Network
Answer:  C

Tuesday, April 19, 2011

The Top 100 Most Innovative Companies Ranking


The World’s Most Innovative Companies.
2006 Rank
Company
Margin Growth
1995-2005
%
Stock Returns
1995-2005
%
1Apple7.124.6
2GoogleNA**NA**
33M3.411.2
4Toyota10.711.8
5Microsoft2.018.5
6General Electric5.713.4
7Procter & Gamble4.412.6
8Nokia0.034.6
9Starbucks2.227.6
10IBM-0.714.4
11VirginNA**NA**
12Samsung-4.5***22.7
13Sony-11.05.1
14Dell2.039.4
15IDEONA**NA**
16BMW9.114.2
17Intel-0.313.8
18eBay13.0***NA**
19IKEANA**NA**
20Wal-Mart1.916.2
21Amazon25.0***NA**
22Target7.425.2
23Honda8.012.9
24Research In Motion57.0***NA**
25Southwest-0.113.9
26PorscheNA**33.1
27Genentech5.729.3
28Cisco-2.215.2
29Nike0.010.7
30Motorola0.73.8
31DaimlerChrysler4.8***-1.8
32Infosys3.0***73.6
33Ryanair2.728.4
34Pixar24.213.8
35SonyEricssonNA**NA**
36WWhole Foods4.136.6
37Capital One-2.127.4
38Tesco-0.316.2
39Danone4.713.3
40BP-0.212.3
41PepsiCo4.910.2
42Hewlett Packard-6.67.1
43Disney-3.72.9
44jetBlueNA**0.9
45Gore & AssociatesNA**NA**
46Skype TechnologiesNA**NA**
47FedEx4.318.9
48Bang & Olufsen2.416.3
49Renault23.714.8
50L’Oreal2.314.2
51ExxonMobil5.813.6
52Siemens2.0***12.6
53Johnson & Johnson3.612.6
54Shell2.411.0
55Pfizer1.89.9
56Singapore Airlines-5.87.7
57Nissan30.25.4
58DuPont-1.84.9
59ZaraNA**NA**
60TiVoNA**-24.6
61Yahoo!NA**42.9
62Macquarie BankNA**35.0
63Audi9.230.1
64Harley Davidson7.122.3
65Progressive Insurance1.122.0
66Volvo-2.717.1
67Philips Electronics3***16.2
68ING Bank3.015.7
69Nestle1.2***13.9
70Boeing0.17.6
71Matsushita Electric Industrial-1.43.9
72easyJet0.0***3.7
73UPS3.43.6
74KO” Coca-Cola1.32.4
75Cirque du Soleil (tied)NA**NA**
75McKinsey (tied)NA**NA**
75Woolworths (tied)5.6***NA**
78Hutchison TelecommunicationsNA**88.1
79Salesforce.comNA**58.4
80ACSNA**35.1
81ITCNA**25.4
82Time Warner8.122.3
83Danaher2.721.7
84Costco Wholesale1.720.7
85LG ElectronicsNA**19.1
86bankinterNA**18.3
87Amgen-0.318.2
88Caterpillar0.317.5
89AccentureNA**16.3
90SAP1.315.7
91SK Telecom1.515.7
92Home Depot4.314.9
93LVMH-2.6***12.3
94Gap-1.711.6
95Unilever5.0***11.2
96Goldman Sachs-4.9***10.9
97John Deere & Co.-1.18.9
98Whirlpool2.07.2
99EntelNA**6.2
100McDonald’s-2.45.2