Field notes
Choosing thresholds for cell-site capacity charts in dense districts
Why copying vendor default alerts fails in packed urban cells, and how to set amber and red lines from your own weekly peaks.
Vendor default thresholds assume average density. Hong Kong’s packed cells, especially along harbour corridors and industrial estates like Chai Wan, peak differently. An amber line that fires all afternoon trains the floor to ignore colour.
Build thresholds from your own weekly peak distribution. Take thirteen weeks of utilisation for each feeder class, mark the 80th and 95th percentiles, and use those as amber and red starting points. Adjust per district if inland sites behave differently from harbour-facing ones.
Document who may change a threshold. Unowned colour rules drift after every major event. A short change log next to the chart — date, reason, author — keeps trust intact.
Separate planning thresholds from alarm thresholds when possible. Planners need early warning for capacity projects; the ops floor needs fewer, louder signals. Mixing both on one panel creates noise.
Revisit the lines after festival weeks and typhoon preparations. Seasonal load shifts are normal; frozen thresholds are not.