In a GPRS based mobile data service, what type of signals are primarily transferred over the network?

Introduction / Context:
General Packet Radio Service, or GPRS, is often described as a 2.5G technology that adds packet switched data capabilities on top of existing GSM networks. Instead of reserving a dedicated circuit for each user, GPRS sends data in packets that share radio resources among multiple users. Understanding what type of signals are actually transferred in GPRS helps clarify why it is suited for bursty data applications such as web browsing and email.

Given Data / Assumptions:

• GPRS operates on top of GSM radio channels.
• It is designed primarily for data services rather than traditional circuit switched voice.
• The focus is on the nature of traffic: packet switched versus analogue or circuit switched signals.

Concept / Approach:
In GPRS, both user data and control information are organised into packets. These packets are sent over the air interface using dynamically allocated time slots. When a user has data to send, the network assigns one or more time slots temporarily; when there is no data, resources can be used by other users. The content of these packets is typically IP based traffic for internet access, along with signalling messages that set up and manage these data sessions. Voice calls, in classic GSM, still use circuit switched channels separate from pure GPRS data.

Step-by-Step Solution:
Step 1: Recognise that GPRS is described as a packet switched data service on GSM networks.Step 2: Therefore, the signals transferred are digital packets carrying user data (such as IP packets) and signalling information.Step 3: Option A states that packet switched user data and signalling packets are transferred, which fits this description.Step 4: Option B mentions only analogue voice signals, which belong to earlier voice services rather than GPRS data.Step 5: Options C and D describe video only broadcast signals or power line signals, which do not match GPRS operation, so option A is correct.

Verification / Alternative check:
Technical documentation for GPRS explains that it uses a packet data protocol such as IP or X.25, encapsulated over GSM radio channels. The network includes new nodes, such as the Serving GPRS Support Node, dedicated to handling packet switched traffic. The presence of these elements confirms that the primary traffic is packet data, not circuit switched voice. Voice calls continue to be handled by the traditional GSM core, whereas GPRS focuses on data packets.

Why Other Options Are Wrong:
Option B is incorrect because GPRS was introduced specifically to support packet data, not to carry analogue voice. Option C restricts the service to video broadcasting, which is not the main purpose of GPRS. Option D refers to electrical power transmission, which is outside the scope of mobile communication protocols.

Common Pitfalls:
Students occasionally confuse GPRS with general GSM voice services and think all traffic is the same. Another misunderstanding is to assume that any mobile data technology must be tied to a specific application such as video streaming. In reality, GPRS provides a general packet switched bearer for many types of data, including web, email and messaging services. Always emphasise the packet switched nature of the signals when describing GPRS.

Final Answer:
Packet switched user data and signalling packets that carry internet and multimedia traffic over the radio interface.