High-Density Auditorium: Clients Associate but Throughput Collapses
A 1,200-seat auditorium is fitted with 24 APs on 5 GHz and 12 on 2.4 GHz, all with default power and channel settings. During a lecture with about 900 devices (many phones and laptops), clients associate but experience very low throughput and frequent retries. A spectrum sweep shows the 2.4 GHz band heavily overlapped and the 5 GHz band with several APs on the same channel. The venue wants to support live video streaming to attendees and asks whether adding more APs will fix it.
1. Assess whether adding APs will solve the problem and propose an RF design change.
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Adding APs will likely worsen the problem: more APs at default power increases co-channel interference and raises the number of overlapping cells, which drives retries and lowers per-client airtime. The sweep already shows 2.4 GHz overlap and 5 GHz channel reuse - the issue is channel plan and power, not AP count.
Recommended changes:
- Disable or minimize 2.4 GHz for the high-density SSID; force clients to 5 GHz.
- Set a clean 5 GHz channel plan using non-overlapping channels (e.g., 36/40/44/48, 52–64, 100–144 as permitted) and enable DFS where appropriate.
- Lower transmit power and use band steering / load balancing so cells are smaller and denser but non-overlapping.
- Enable 802.11k/v/r to improve steering and roaming.
- Validate with a post-change survey and client throughput test.
Only after the channel/power plan is optimized should AP count be reconsidered, and then only with a design that accounts for co-channel reuse.
2. The customer insists on keeping 2.4 GHz for legacy devices. How do you reconcile that with the density requirement?
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Keep 2.4 GHz but isolate and constrain it:
- Put legacy devices on a separate SSID mapped only to 2.4 GHz radios, and keep the high-density streaming SSID on 5 GHz only.
- On the 2.4 GHz radios, use minimum power and a 1/6/11-only channel plan to reduce overlap.
- Apply band steering on dual-band SSIDs so capable clients prefer 5 GHz.
- Cap or rate-limit the legacy SSID so it cannot consume airtime needed for streaming.
- Monitor retry rates and client counts per band; if 2.4 GHz overlap persists, reduce the number of 2.4 GHz-enabled APs rather than adding more.
This satisfies the legacy requirement without letting 2.4 GHz contention degrade the primary service.