GPRS MS Classes
The handset is probably the most well-known piece of equipment, because this is the part we use to make phone calls and to access data services. When we talk about advanced services, the handset is commonly called an MS, which consists of terminal equipment (TE) and a mobile terminal (MT).
TE is the device that hosts 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 quipments:
Class A terminals can handle packet data and voice at the same time. In other words, we need two transceivers because the handset has to send and/or receive data and voice at the same time. This situation makes class A terminals significantly more expensive to manufacture than class B and C terminals.
Class B terminals can handle both packet data and voice, but not at the same time. In other words, you can use the same transceiver for both, keeping the cost of the terminals down.
In practice, the GPRS session (like WAP browsing, file transfer, and so on) is suspended when a GSM voice call is started. How this information is presented to the user is up to the device manufacturer, but one way is to give the user the choice between receiving an incoming call and maintaining the data session. That way, a user who is transferring money between his or her accounts by using a WAP service does not have to stop that transaction just because someone calls.
Class C terminals can only handle either voice or data. 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. There is currently work going on in 3GPP to standardize a lightweight A class in order to make handsets with simultaneous voice and data available at a reasonable cost.