2. MOBILE SERVICES
3. SYSTEM ARCHITECTURE
4. RADIO INTERFACE
5. LOCALIZATION AND CALLING
6. HANDOVER
7. SECURITY
8. NEW DATA SERVICES
INTRODUCTION
As the wired communication was facing many problems and was thought to be costly. Therefore it was desired by the users as well as by the service providers that the wireless communication must be brought in to use in order to provides some additional facilities to its users with lesser cost and difficulty. The complete mobile communication is divided into three generations…. …
1. First Generation(1980-1990)
2. Second Generation(1991-2005)
3. Third Generation(2002-onward)
In the first generation we were using analog modulation. It was completely based on analog communication. The important technology were given below
1. AMPS (824 –849mhz (uplink) 869-894mhz(down link))
2. TACS (890 –905mhz (uplink) 935-960mhz(down link))
3. NMT (890 –905mhz (uplink) 935-960mhz(down link))
NTT(860 –885mhz (uplink) 915-940mhz(down link))
Second generation of mobile communication is based on digital communication. It is mostly divided into two part GSM and CDMA.
GSM stands for Global System for Mobile Communication.
GSM is the most popular digital system with approximately 70% market share. GSM is the most successful digital system of second generation in the world today. In past it was known as GROUP SPECIAL MOBILE (GSM). GSM is initially deployed in EUROPE using 890-915mhz for uplink and 935-960 MHz for downlink this system is also called GSM 900. GSM 1800(1710 –1785mhz (uplink) 1805-1880mhz(down link)) also called DCS (digital cellular system). GSM 1900(1850 –1910mhz (uplink) 1930-1990mhz(down link)) also called PCS (personal communication system). A GSM system that has been introduced in several European countries for rail-board is GSM –rail. Today many providers all over the world use GSM (more than 184 countries in Asia, Africa, Europe, Australia, and America)
GSM has defined three different type of services………
1. BEARER SERVICESS
2. TELE SERVICESS
3. SUPPLEMENTRY SERVICESS
A mobile station MS is connected to the GSM public land mobile network (PLMN) via the Um interface .This network is connected to transit network ISDN or PSTN.
1.BEARER SERVICESS
Bearer services permit transparent and non-transparent ,synchronous or asynchronous data transmission. Transparent bearer services only use the function of the physical layer. Data transmission has a constant delay throughput if no transmission errors occur. The only mechanism to increase the Transmission quality is the use of forward error correction (FEC).
Non- Transparent bearer services use protocols of layers two and three to implement error correction and flow control. The services use the transparent bearer services, adding radio link protocol (RLP). This protocol comprises mechanism of high-level data link protocol (HDLC).
· data service (circuit switched)
· synchronous: 2.4, 4.8 or 9.6 kbit/s
· asynchronous: 300 - 1200 bit/s
· data service (packet switched)
· synchronous: 2.4, 4.8 or 9.6 kbit/s
· asynchronous: 300 – 9600 bit/s
TELE SERVICES
GSM mainly focuses on voice-oriented Tele services. These comprise encrypted voice transmission, message services, and basic data communication with terminals known as from PSTN or ISDN. The primary goal of GSM was the provision of high-quality digital voice transmission, offering at least the typical bandwidth of 3.1khz of analog phone. Another services offered by GSM are the emergency number. A useful service offered by GSM is short message service (SMS) with transmission upto 160 characters. SMS message do not use the standard data channels of GSM but exploit unused capacity in the signaling channels. The successor of SMS is EMS with capacity upto 760 characters and used for transmission of animated picture, images ring tones. Multimedia message services (MMS) is available for transmission of large picture, short video clips. Another non-voice available service is group 3 fax.
SUPPLEMENTARY SERVICES
GSM can offer supplementary services like identification, call redirection or forwarding of ongoing call. Standard ISDN feature like closed user group and multiparty communication may be available.
· identification: forwarding of caller number
· suppression of number forwarding
· automatic call-back
· conferencing with up to 7 participants
· Locking of the mobile terminal (incoming or outgoing calls
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