GPRS - Mobile Station Classes
Mobile Station Classes talk about the globally-known equipment handset which is also known as Mobile Station (MS) and its three different classes. This equipment, more popular as handset, is used to make phone calls and access data services. The MS comprises of Terminal Equipment (TE) and Mobile Terminal (MT).
TE is the equipment that accommodates the applications and the user interaction, while the MT is the part that connects to the network.
In the following example, Palm Pilot is TE and Mobile phone is MT.
In order to take advantage of the new GPRS services, we need new GPRS enabled handsets. There are three different classes of GPRS terminal equipments:
Class A terminals can manage both packet data and voice simultaneously. Which means, one needs two transceivers, as the handset has to send or receive data and voice at the same time.This is the main reason why class A terminals are high-priced to manufacture than class B and C terminals.
Class B terminals do not play the same role like Class A. These terminals can manage either packet data or voice at a time. One can use a single transceiver for both, resulting in the low cost of terminals.
For example, If a user is using the GPRS session (like WAP browsing, file transfer, etc.) then this session is halted if he or she receives a call. This terminal does not allow both the sessions active in one go. This backlog needs rectification thereby giving the user a facility of both receiving a call and maintaining the data session.
Class C terminals can manage either only packet data or only voice. Examples of class C terminals are GPRS PCM/CIA cards, embedded modules in vending machines, and so on.
Due to the high cost of class A handsets, most handset manufacturers have announced that their first handsets will be class B. Currently, work is going on in 3GPP to standardize a lightweight class A in order to make handsets with simultaneous voice and data available at a reasonable cost.