Mobile phone basics

PTT also known as Press-to-Transmit, is a method of conversing on half-duplex communication lines by making use of a momentary button to switch from voice reception mode to transmission mode. Some mobile operators offer the PPT service on mobile phones; it allows voice signals to be transmitted from one user to another on the system without the need of an established existing connection.

CDMA is a form of multiplexing and a method of multiple accesses that does not divide up the channel by time, or frequency, but instead encodes data with a special code associated with each channel and uses the constructive interference properties of the special codes which can perform the multiplexing. CDMA also refers to digital cellular telephony systems that use this multiple access scheme. CDMA phones usually do not need a SIM card.

GPRS is a mobile data service available to subscribers of GSM mobile phones. GPRS data transfer is mostly charged per kilobyte (KB) of transferred data to and from the cell phone. GPRS is utilized for services such as Internet and MMS. In the future, it is still anticipated that low cost voice over IP will be made available in mobile phones.

SIM is a removable smart card that is used in the cell phone and was available in two standard sizes. Initially it was the size of a credit card, while its more popular and widely used mini version has a width of 25 mm. This has been adopted by most cell phone manufacturers. The SIM card securely stores a key code which identifies a mobile phone to its service provider.

EDGE is an enhancement to the GSM networks which makes use of theTDMA (Time Division Multiple Access) frame structure, logic channel and 200 KHz carrier bandwidth. EDGE is not only capable of providing three times the data capacity of GPRS but also has improved data transmission reliability. EDGE is employed for advanced mobile services that require high data transmission rate such as downloading of audio and video clips, high speed and quality Internet access etc, EDGE is classified as a 2.75G network technology.