A Throttle Announced in Advance: Recording 30 Minutes of Northern Taiwan's Mobile Networks on 13 August

On Thursday 13 August, from 14:30 to 15:00 Taipei time (UTC+8), mobile networks in Keelung, Taipei, New Taipei, Taoyuan, Hsinchu City, Hsinchu County, and Yilan will be throttled for thirty minutes. The throttle is part of Taiwan's Urban Resilience Exercise, executed simultaneously by all three major carriers. Official announcements state that voice calls, SMS, and cell broadcast continue to work, and that high-bandwidth services degrade: video streaming, video calls, mobile payments, cloud sync.1 The NCC's advice for the window is to prepare in advance for going offline.2
Officials have described the depth of the throttle twice. On 20 July, Defence Minister Wellington Koo told the Legislative Yuan that speeds would drop to one percent of 4G and 5G capacity. After the central Taiwan drill on 10 August, the Executive Yuan described the method: carriers apply rate limiting in the core network, capping mobile download speeds at 256KB. The two statements are of the same order, and either one gives a figure to expect when the measurements come in.
The date, the window, the seven counties, the three carriers: every boundary of this throttle is public before it runs. Studies of network throttling rarely get that. In most cases users notice slowness first and researchers reconstruct the timeline afterwards, leaving the edges fuzzy. Pre-announced shutdowns are not new elsewhere, exam-period national shutdowns being the familiar example.6 On the publicly documented record, a pre-announced throttle is less common, particularly one with per-carrier granularity.
During the same window at the central Taiwan drill on 10 August, Taiwan's OONI observations contained no performance measurement from a mobile network at all. The northern drill is the last of this year's exercise, so after 13 August the opportunity does not come round again.
If you are in one of those seven counties, your phone is going to slow down for that half hour regardless. Rather than just waiting it out, you might as well leave a record behind.
