CTA Broadband & Access Network Technologies 1 — Questions and Answers
Question 1: What is the maximum downstream speed supported by VDSL2 Profile 17a?
- 52 Mbps
- 100 Mbps (Correct answer)
- 250 Mbps
- 1 Gbps
Correct answer: 100 Mbps
VDSL2 Profile 17a operates up to 17.664 MHz and supports downstream speeds up to 100 Mbps over short copper loops.
Question 2: What does DOCSIS stand for?
- Data Over Cable Service Interface Specification (Correct answer)
- Digital Optical Cable Service Interface Standard
- Data Oriented Cable Signal Interface System
- Digital Over-the-air Cable Service Integration Standard
Correct answer: Data Over Cable Service Interface Specification
DOCSIS stands for Data Over Cable Service Interface Specification, the standard governing data transmission over cable TV networks.
Question 3: In DSL technology, what is referred to as the 'last mile'?
- The final mile of fiber backbone between ISPs
- The connection between the central office and the customer premises (Correct answer)
- The last segment of the internet backbone before a major hub
- The final link between a Tier 1 and Tier 2 provider
Correct answer: The connection between the central office and the customer premises
The 'last mile' refers to the final leg of the telecommunications network connecting the central office (CO) to the end customer's premises, typically over copper wire.
Question 4: Which multiplexing technique separates upstream and downstream signals on an HFC cable network?
- Time Division Multiplexing (TDM)
- Frequency Division Multiplexing (FDM) (Correct answer)
- Wavelength Division Multiplexing (WDM)
- Code Division Multiplexing (CDM)
Correct answer: Frequency Division Multiplexing (FDM)
HFC networks use Frequency Division Multiplexing to assign separate frequency bands for upstream (5–42 MHz) and downstream (54–1000+ MHz) transmissions.
Question 5: Which DOCSIS version introduced Full Duplex (FDX) operation, enabling symmetric multi-gigabit speeds?
- DOCSIS 2.0
- DOCSIS 3.0
- DOCSIS 3.1
- DOCSIS 4.0 (Correct answer)
Correct answer: DOCSIS 4.0
DOCSIS 4.0 introduced Full Duplex (FDX) technology, allowing the same spectrum to be used simultaneously for upstream and downstream, enabling symmetric multi-gigabit broadband over coaxial cable.
Question 6: What technology allows multiple DSL lines to be aggregated together to increase total bandwidth?
- DSL bonding (G.Bond / ITU G.998) (Correct answer)
- VLAN trunking (IEEE 802.1Q)
- Spanning Tree link aggregation
- Multilink PPP only
Correct answer: DSL bonding (G.Bond / ITU G.998)
DSL bonding, standardized as ITU-T G.998 (G.Bond), allows two or more DSL pairs to be combined, effectively multiplying available bandwidth for a single subscriber.
Question 7: What is the primary factor that limits ADSL performance compared to fiber optic broadband?
- Higher latency due to modulation overhead
- Signal attenuation increasing with loop distance from the CO (Correct answer)
- Incompatibility with IPv6 protocols
- Higher installation cost per subscriber
Correct answer: Signal attenuation increasing with loop distance from the CO
ADSL performance degrades significantly with distance because copper wire attenuates high-frequency signals, reducing both speed and signal-to-noise ratio the farther the customer is from the central office.
CTA Broadband & Access Network Technologies 1
What is the maximum downstream speed supported by VDSL2 Profile 17a?