Saturday, January 7, 2012


                Today I am going to discuss about something which you are really familiar. If you are using any wireless modem or mobile phone you may have used these words. But most of the people don’t have a clear idea what those technical acronyms stand for even though they frequently use it.

Global System for Mobile Communications (GSM) is a digital cellular phone technology. This includes set of standers to support the 2G digital cellular networks. 2G is the replacement of first generation analog cellular networks. GSM operates with TDMA (Time Division Multiple Access) technology based on circuit switching network. TDMA technology interleaves multiple digital signals on to high speed data channel. GSM supports voice calls and data transfer (SMS) speed up to 9.6kbit/s. Today GSM networks have spread over 218 countries worldwide and it allows the international roaming capability.
Mobile phone or any device which supports GSM technology includes a SIM (Subscriber Identity Module) card. This smart card has programmed so that it contains the details of the user account information.

General Packet Radio Service (GPRS) is an improved data service in GSM networks. GPRS added a packet data transfer capability to circuit switched GSM networks. GPRS enables data rate up to 40 kbit/s. MMS, instant messaging and WAP are few services are offered by GPRS technology. 2G cellular technology together with GPRS is sometimes called 2.5G which described as a transition of 2G to 3G mobile telephony.

Enhanced Data rates for GSM Evolution (EDGE) is a further enhancement of GPRS and GSM network technologies. EDGE is four times efficient than GPRS technology. GPRS uses four coding schemes (CS-1 to 4) while EDGE uses nine modulation and coding schemes (MCS-1 to 9). The normal data rate of EDGE is 40-50 kbps per timeslot and maximum is 40-50 kbps per timeslot. EDGE technology supports both circuit and packet switching techniques. EDGE technology can provides all the capabilities of the GPRS and directly map with the structure of the GSM network. Therefore EDGE is called backward compatible technology. No any changes are required for the existing GSM network for use of EDGE except the installation of EDGE transceiver at base stations. EDGE is only a software upgrade with GSM technology. EDGE cannot work without GSM technology, because EDGE networks are built upon the GSM networks. EDGE has all the requirement for the 3G standers and it is accepted as a 3G network technology.

Wideband Code Division Multiple Access (WCDMA) is a third generation (3G) cellular network technology. This technology has much higher data speed than the previous technologies which has described above. The data rates of the WCDMA technology are 2 Mbps for local area networks and 384 kbps for wide area networks. Even though it uses the same cored network as the GSM/GPRS/EDGE, WCDMA transmits on a pair of 5 MHz wide radio channels. WCDMA works with both frequency division duplex (FDD) and time division duplex (TDD). WCDMA provides mobile multimedia services such as music, tv/video image and internet access in addition to the voice, text and MMS services.

High Speed Packet Access (HSPA) is a mobile wireless technology which represents the 3.5G family. HSPA is a combination of HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access)  technologies. HSPA uses FDD transmission scheme. HSPA rates are 1 to 4 Mbps and HSPA uplink speeds are 500 kbps to 2 Mbps. But theoretically peak speed of downlink is 14 Mbps and the peak speed of uplink is 5.8 Mbps in a 5 MHz channel. HSPA is backward-compatible with UMTS, EDGE and GPRS. Besides the speed the advantage of the HSPA is the low cost of transmission for a data unit.