Every wire, radio link, or fibre has a physical limit on how fast it can carry data. Channel capacity tells us that maximum speed, and multiplexing tells us how to pack many signals onto one link so we do not waste that capacity. This topic is one of the most frequently and predictably tested areas in BCS, Bank IT-officer, and other government IT exams, because it mixes two things examiners love: a small set of clean formulas and a lot of quick numerical problems. If you master the Nyquist and Shannon formulas and the four multiplexing schemes, you can reliably score every mark this chapter offers.
Learning objectives
- Recall and correctly apply the Nyquist bit rate formula for noiseless channels: C = 2B log₂(L)
- Recall and correctly apply the Shannon capacity formula for noisy channels: C = B log₂(1 + SNR)
- Convert between SNR (a ratio) and SNR in decibels (dB) using SNR(dB) = 10 log₁₀(SNR)
- Solve for any unknown (capacity C, bandwidth B, number of levels L, or SNR) in these formulas
- Distinguish clearly between bandwidth, data rate (bit rate), and baud rate (signal rate)
- List and explain the 5 components of a data communication system
- Explain and compute examples for FDM, TDM, WDM, and CDM multiplexing
- Compare synchronous vs asynchronous transmission