In data communication, what is the main difference between baseband transmission and broadband transmission over a physical medium?

Introduction / Context:
Baseband and broadband are two fundamental approaches to transmitting data over a communication medium such as copper cable or fiber. Many networking and communication questions test whether you can clearly differentiate between these two concepts, especially in the context of Ethernet, cable television networks, and internet access technologies.

Given Data / Assumptions:

• The physical medium can carry signals over a certain frequency range.
• Baseband and broadband refer to how the signal uses that frequency range.
• We are comparing how data is encoded and how many channels can exist at once.
• We assume standard textbook definitions for baseband and broadband.

Concept / Approach:
Baseband transmission sends digital signals directly on the medium, using the entire bandwidth of the channel for a single data stream. Classic Ethernet over twisted pair is an example. There is no carrier modulation; the medium carries the original digital pulses. Broadband transmission, by contrast, uses analog modulation techniques and divides the available frequency range into multiple channels using frequency division multiplexing. Cable internet, where one coaxial cable carries many television channels plus data channels, is a typical broadband example. The correct answer must highlight direct digital signalling for baseband and modulated, multi-channel operation for broadband.

Step-by-Step Solution:
1. Remember that baseband typically means a single channel using the full frequency range for digital pulses.2. Broadband typically means multiple analog channels using different frequency bands on the same medium, often with separate upstream and downstream bands.3. Option A states that baseband uses the entire channel to send digital signals without modulation, while broadband uses analog modulation and multiple frequency channels, which matches standard definitions.4. Option B incorrectly ties baseband to wireless and broadband to copper, which is not conceptually accurate; both approaches can use multiple media.5. Option C reverses distances and topologies and does not reflect actual technology usage.6. Option D claims baseband requires frequency division multiplexing, which is false; frequency division is actually characteristic of broadband.7. Therefore, Option A correctly explains the key difference.

Verification / Alternative check:
Consider Ethernet on twisted pair, which is typically baseband and labelled with BASE in standards names like 100BASE-TX. This indicates baseband signalling. By contrast, cable modems use DOCSIS standards that define upstream and downstream channels as modulated carriers at different frequencies on the same coaxial cable, a clear example of broadband transmission. These real-world examples verify the conceptual difference described in Option A.

Why Other Options Are Wrong:
Option B is wrong because both baseband and broadband can be implemented on copper, fiber, or even wireless media; the distinction is about signalling and channelization, not the physical medium alone.Option C is wrong because baseband is common on local area networks, not exclusively long distance WAN links, and broadband technologies can also operate over large distances.Option D is wrong because baseband generally does not use frequency division multiplexing, whereas broadband often does exactly that.

Common Pitfalls:
Students sometimes confuse broadband in the engineering sense with the marketing term used for high-speed internet, assuming any fast connection is broadband even if it uses baseband signalling. Another pitfall is overlooking that Ethernet standards explicitly label baseband systems with BASE, which is a helpful memory aid. Keeping the distinction of digital single-channel versus modulated multi-channel in mind will help you answer similar exam questions.

Final Answer:
Baseband uses the entire channel to send digital signals without modulation, while broadband uses analog modulation and multiple frequency channels.