Technicalities
Currently in Bangladesh, five mobile operators - GrameenPhone, Banglalink, AKTEL, Warid and Teletalk use the GSM (Global System for Mobile communications) technology and only CityCell uses the CDMAOne technology.

GSM is a cellular network, which means that mobile phones connect to its network by searching for cells in the nearest surrounding area. GSM networks operate in four different frequency ranges namely 850/900/1800/1900 MHz. Most GSM networks operate in the 900/1800 MHz bands.

Lets take a look at how the GSM network system works for 2G networks. The network can be divided into three sections.

One is the Base Station Subsystem (BSS) which consists of Base Transceiver Station (BTS), Base Station Controller (BSC), and Packet Control Unit (PCU).

The next section is Network Switching Subsystem (NSS) which consists of Mobile Switching Center (MSC), Home Location Register (HLR), Visitor Location Register (VLR), Authentication Center (AUC) and Equipment Identity Register (EIR).

The last segment is the GPRS Core Network, which consists of Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN).

All GSM operators more or less, have these common elements for its 2G/2.5G networks.

Difference between 2G and 3G
The basic difference between 2G and 3G networks is the Radio Network Controller (RNC), which works for 3G as the BSC of 2G, and the Node B, which works as the BTS.

Compared to GSM, UMTS networks initially required a higher base station density. For a full-fledged UMTS incorporating video on demand features, one base station needed to be set up every 1km to 1.5 km.

This was the case when only the 2100 MHz band was being used, however the problem has been solved by using lower-frequency bands (such as 850 and 900 MHz).

Ericsson is conducting its 3G trial by using the site and transmission networks of three