is the most popular standard for mobile phones in the world. GSM is used by over three billion people across more than 212 countries. The ubiquity of the GSM standard makes the international roaming very common between mobile phone operators, enabling subscribers to use their phones in many areas of the world.
GSM differs significantly from its predecessors in that both signaling and speech channels are digital, (considered as second generation (2G) mobile phone system). Data communication was built into the system from the 3rd Generation Partnership Project(3GPP).From the point of view of the consumers, the key advantage of GSM systems has been higher digital voice quality and low cost alternatives to making text messaging. The advantage for network operators has been the ability to deploy equipment from different vendors because the open standard allows easy interoperability.
CELL PHONES-AMAZON.COM
GSM is a cellular network, which means that mobile phones connect to it by searching for cells in the immediate vicinity. GSM networks operate in four different frequency ranges. Most GSM networks operate in the 900 MHz or 1800 MHz bands. Some countries in the Americas (including Canada and the United States) use the 850 MHz and 1900 MHz bands because the 900 and 1800 MHz frequency bands were already allocated.Network structure
The network behind the GSM system seen by the customer is large and complicated in order to provide all of the services which are required. It is divided into a number of sections and these are each covered in separate articles.
• the Base Station Subsystem (the base stations and their controllers).
• the Network and Switching Subsystem (the part of the network most similar to a fixed network). This is sometimes also just called the core network.
• the GPRS Core Network (the optional part which allows packet based Internet connections).
• all of the elements in the system combine to produce many GSM services such as voice calls and SMS.
One of the key features of GSM is the Subscriber Identity Module (SIM), commonly known as a SIM card. The SIM is a detachable smart card containing the user's subscription information and phone book. This allows the user to retain his or her information after switching handsets. Alternatively, the user can also change operators while retaining the handset simply by changing the SIM. Some operators will block this by allowing the phone to use only a single SIM, or only a SIM issued by them; this practice is known as SIM locking, and is illegal in some countries.
In Australia, North America and Europe many operators lock the mobiles they sell. This is done because the price of the mobile phone is typically subsidized with revenue from subscriptions, and operators want to try to avoid subsidizing competitor's mobiles. A subscriber can usually contact the provider to remove the lock for a fee, utilize private services to remove the lock, or make use of ample software and websites available on the Internet to unlock the handset themselves. While most web sites offer the unlocking for a fee, some do it for free. The locking applies to the handset, identified by its International Mobile Equipment Identity (IMEI) number, not to the account (which is identified by the SIM card).
In some countries such as Belgium, Costa Rica, India, Indonesia, Pakistan, and Malaysia, all phones are sold unlocked. However, in Belgium, it is unlawful for operators there to offer any form of subsidy on the phone's price. This was also the case in Finland until April 1, 2006, when selling subsidized combinations of handsets and accounts became legal, though operators have to unlock phones free of charge after a certain period (at most 24 months)
BLUETOOTH
Bluetooth is an industrial specification for wireless personal area network (PANs). Bluetooth provides a way to connect and exchange information between devices such us mobile phones, laptops, PCs, printers, digital cameras, and video game consoles via secure, globally unlicensed short-range radio frequency.
Bluetooth is a radio standard and communication protocol primarily designed for low power consumption, with a short range (power class dependent: 1metre, 10metres, 100metres) based around low cost transceiver microchips in each device .
Class Maximum Permitted Power
(mW)
Maximum Permitted Power (dBm) Range
(approximate)
Class 1 100 mW 20 dBm 100 meters
Class 2 2.0 mW 4 dBm 10 meters
Class 3 1 mW 0 dBm 1 meter
Bluetooth lets these devices communicate with each other when they are in range. The devices uses a radio communications system, so they do not have to be in line of sight of each other, and can even be in other rooms, so long as the received transmission is powerful enough
List of applications
More prevalent applications of Bluetooth include:
• Wireless control of and communication between a mobile phone and a hands-free headset. This was one of the earliest applications to become popular.
• Wireless networking between PCs in a confined space and where little bandwidth is required.
• Wireless communication with PC input and output devices, the most common being the mouse, keyboard and printer.
• Transfer of files between devices with OBEX.
• Transfer of contact details, calendar appointments, and reminders between devices with OBEX.
• Replacement of traditional wired serial communications in test equipment, GPS receivers, medical equipment, bar code scanners, and traffic control devices.
• For controls where infrared was traditionally used.
• Sending small advertisements from Bluetooth enabled advertising hoardings to other, discoverable, Bluetooth devices.
• Two seventh-generation game consoles, Nintendo and Sony's PlayStation 3, use Bluetooth for their respective wireless controllers.
• Dial-up internet access on personal computers or PDAs using a data-capable mobile phone as a modem.
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