In RF link design, which statement is true?

• A. Peak rate alone determines capacity
• B. Sustained rate alone determines capacity
• C. BER is the only metric that matters
• D. Both peak and sustained data rates should be considered in link planning to ensure margin

Answer: (D)

Planning capacity in RF links means looking at how the link will actually be used, not just how fast it could transmit in ideal moments. The peak rate represents the maximum instantaneous throughput during short bursts, but traffic varies and often doesn’t sit at that level. If you design only for peak, you risk congestion and dropped data when bursts occur. Conversely, focusing only on the sustained rate ignores those short-term spikes and can lead to underutilization or unexpected delays during busy periods. Real systems require a margin to absorb variability from fading, interference, and scheduling, so you plan for both the highest expected bursts and the typical long-term load. BER and error protection matter for data integrity, but they don’t alone set how much useful data you can carry; capacity must be assessed with the expected traffic pattern and the available margin under changing conditions. For reliable link planning, both peak and sustained data rates should be considered to ensure adequate margin.