Explain how Quadrature Amplitude Modulation (QAM) enhances modem performance over PSTN compared to basic amplitude modulation.
Why did PSTN-based Internet access become obsolete, and how does its schematic differ from modern broadband setups?
Analyze the scalability of star and mesh topologies for a network with 100 devices. Which is more practical and why?
How does a switch’s MAC address table improve performance in a star topology compared to a hub, and what happens during a table overflow?
Why is a bus topology simpler than an all-to-all topology, and what challenges does it introduce
Answers
Answer: QAM combines amplitude and phase variations to encode multiple bits per symbol (e.g., 64-QAM encodes 6 bits/symbol), increasing data rates compared to amplitude modulation’s 1 bit/symbol.
Description: QAM enabled higher-speed dial-up connections. Analyzing modulation techniques helps students understand legacy system optimizations and their relevance to modern broadband technologies.
Answer: PSTN’s low bandwidth (56 Kbps) and circuit-switching limited scalability. Its schematic shows modems and analog lines, while broadband uses routers and digital lines (e.g., DSL).
Description: Comparing PSTN to broadband highlights technological evolution. Schematic analysis reinforces understanding of network architectures, preparing students for modern connectivity designs.Answer: Star topology scales better with a central switch, requiring 100 cables. Mesh requires 4950 cables (n(n-1)/2), making it impractical. Star is preferred for cost and manageability.
Description: Scalability analysis teaches network planning. Star topology’s centralized design simplifies maintenance, while mesh offers redundancy but is costly, aiding students in practical design decisions.
Answer: Switches forward packets only to intended ports using a MAC table, reducing collisions. Hubs broadcast to all, increasing collisions. Table overflow causes flooding, acting like a hub.
Description: Switch efficiency is key to modern LANs. Analyzing table overflow scenarios helps students troubleshoot network congestion, applying knowledge to optimize performance.Answer: Bus topology uses a single shared medium, reducing wiring complexity compared to all-to-all’s excessive connections. Challenges include collisions, requiring media access control protocols like CSMA/CD.
Description: Bus topology simplifies design but needs collision management. Students learn trade-offs in topology selection, applying concepts to design efficient small-scale networks.