Twelve Megabits in the Back Bedroom
Tom's flat has a 200 Mbit/s fibre connection. The router sits in a hallway cupboard. In the back bedroom his five-year-old laptop reports 12 Mbit/s on a speed test and video calls drop; carrying the same laptop to the hallway gives 190 Mbit/s. His phone, in the same bedroom at the same time, reports 90 Mbit/s on the 5 GHz band, while the laptop is connected on 2.4 GHz. The building has 14 visible neighbouring networks, six of them strong on channel 6. The laptop's Wi-Fi card supports 802.11n only. The router is supplied by the ISP and the fibre entry point cannot be moved. Tom works from that bedroom three days a week and needs reliable calls.
1. The phone and the laptop are in the same room on the same network, yet one gets 90 Mbit/s and the other 12. Explain the difference without blaming the broadband.
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The broadband is not the limit: the hallway test giving 190 Mbit/s rules it out. Three separate factors explain the gap.
- Band. The phone is on 5 GHz, which has many more channels and far fewer competing networks; the 2.4 GHz band has essentially three non-overlapping channels, and the building has fourteen networks with six strong ones on channel 6. The laptop is almost certainly sharing channel 6 with strong neighbours, so it spends much of its airtime waiting and retransmitting.
- Adapter. The laptop's card is 802.11n and, as described, cannot use 5 GHz at all. That caps its theoretical link rate well below what the phone negotiates, and caps it on the crowded band as well.
- Distance and walls. 5 GHz attenuates faster through walls, which is why the phone drops from 190 to 90 in the bedroom. But 90 is comfortably enough for calls, so the wall is not the main problem.
The 12 Mbit/s figure is therefore mostly contention on 2.4 GHz plus an older adapter, not a faulty line.
2. Rank the possible fixes by cost and likely effectiveness for Tom's situation, and recommend one.
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1. Change the router's 2.4 GHz channel to 1 or 11 (free, small gain). Worth doing first because it costs nothing, but six strong neighbours mean the 2.4 GHz band will still be crowded, so expect only partial improvement and do not rely on it.
2. Try to connect the laptop to 5 GHz (free, will fail). The setup states the card is 802.11n only, so it cannot see the 5 GHz network. This is worth confirming in the adapter settings, but it is not the fix.
3. USB Wi-Fi adapter supporting 5 GHz (roughly €25). This is the cheapest option that changes the underlying constraint rather than working around it. It gives the laptop the same band the phone is already using at 90 Mbit/s.
4. Powerline adapter or a long Ethernet cable (roughly €40–60). The most reliable option of all, and it removes radio entirely, but its performance depends on the flat's wiring, which Tom cannot predict before buying.
5. Wi-Fi extender or repeater (avoid). An extender halves throughput on the link it repeats and would repeat the already-congested 2.4 GHz band, so it is unlikely to reach the phone's 90 Mbit/s.
Recommendation: the 5 GHz USB adapter first, with the powerline kit as the fallback if it disappoints. A mesh system would solve the problem but costs far more than the situation justifies.
3. After fitting a 5 GHz adapter, the speed test in the bedroom reads 85 Mbit/s, yet some video calls still stutter. Why is bandwidth not the whole story?
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Because calls fail on latency and loss, not on average throughput.
- A video call needs perhaps 2 to 4 Mbit/s in each direction. 85 Mbit/s down is twenty times more than required, so raw capacity was never the binding constraint.
- Calls break when packets arrive late, arrive unevenly (jitter), or never arrive. A link can average 85 Mbit/s while dropping bursts of packets during a microwave oven cycle or a neighbour's traffic.
- The upload direction matters as much as the download and is often much smaller on a fibre package; a speed test quoted as a single number hides this.
- Bufferbloat is a common cause: when anyone else in the flat uploads a large file, the router queues the call's packets behind it and latency spikes from 20 ms to several hundred.
Diagnosis should therefore check latency and packet loss under load, and the test for upload speed separately, before concluding anything about the Wi-Fi.