Telsim GSM / GPRS Network Expansion, Turkey
A recent agreement between Motorola and Turkish GSM (Global System for Mobile Communications) operator Telsim looks to expand Turkey's countrywide GSM. The project includes the supply of GSM 900Mhz infrastructure equipment for the next three years and a full trial overlay general packet radio service (GPRS) core mobile data network.
Currently, 2.8 million subscribers are on the Telsim network, and the expansion will help enable service to over five million subscribers. GPRS handsets will be used in the data trial to allow easy and secure access to the internet and corporate intranets, so users have mobile access to email, train timetables, weather and traffic conditions wherever roaming agreements are in place. The GSM expansion contract will enable the network capacity and coverage to handle the expected increase in mobile data users, with the GPRS overlay delivering the content and services to the wireless devices. The expansion work will begin with immediate effect, with the GPRS trial scheduled for second quarter of 2000.
GSM 900 AND DCS 1800
The large subscriber growth and demand for cohesive coverage and service in Western Europe resulted in an unprecedented collaboration among many telecommunication organizations. This collaboration produced the Global System for Mobile Communication (GSM) - a Pan European cellular radio standard now used by operators around the world.
GSM and DCS 1800 systems use the Time Division Multiple Access (TDMA) technique. TDMA systems begin with a discrete part of the radio frequency spectrum referred to as one carrier. Each carrier is then divided into time slots and one user is assigned to each time slot. GSM and DCS 1800 systems divide a 200kHz carrier into 8 time slots. A time slot is referred to as a 'channel' in TDMA-based systems.
GSM defines a complete and integrated digital cellular network system. The development of GSM started in 1982 as the logical evolution of mobile radio within Europe to overcome the difficulties arising from the operation of numerous incompatible analogue cellular systems throughout the region. The meaning of the acronym GSM was changed by its operators from Groupe Spécial Mobile to Global System for Mobile Communications as a marketing decision to underline the international nature of the standard, with international roaming as a key selling feature.
As a packet-switched technology, GPRS supports the internet protocol (IP) and X.25, packet-switched standards currently used in wireline communications. As such, any service that is used on the fixed internet today will be able to be used over GPRS. Because GPRS uses the same protocols as the internet, the networks can be seen as subsets of the Internet, with GPRS devices as hosts, potentially with their own IP addresses.
GPRS is based on a modulation technique called Gaussian minimum-shift keying (GMSK). This is where the rectangular pulses corresponding to the bitstream are filtered using a Gaussian-shaped impulse response filter, producing lower sidelobes than would otherwise be the case. This modulation technique does not allow as high a bit rate across the air interfaces as eight-phase-shift keying (8 PSK) modulation, being introduced in EDGE (Enhanced Data GSM Environment) systems.
Enabling GPRS on a GSM or TDMA network requires the addition of two core modules, the Gateway GPRS Service Node (GGSN) and the Serving GPRS Service Node (SGSN). The GGSN acts as a gateway between the GPRS network and the Public Data Networks such as IP and X.25. They also connect to other GPRS networks to enable roaming. The SGSN provides packet routing to all users in its service area.