Comment résoudre le chevauchement des canaux WiFi

How to Fix WiFi Channel Overlap — A Purple WiFi Intelligence Briefing [INTRODUCTION — approximately 1 minute] Welcome to the Purple WiFi Intelligence Briefing. I'm your host, and today we're cutting straight to one of the most persistent and costly problems in enterprise wireless networking: WiFi channel overlap. If you're managing connectivity across a hotel, a retail estate, a conference centre, or a stadium, the chances are that channel interference is quietly degrading your network performance right now — even if your dashboard shows all APs as green. We're going to cover exactly what's happening at the radio layer, why it matters commercially, and what your team should be doing about it this quarter. This isn't a theoretical exercise. By the end of this briefing, you'll have a clear implementation framework and the decision criteria to take back to your network team. Let's get into it. [TECHNICAL DEEP-DIVE — approximately 5 minutes] First, let's establish the problem clearly. WiFi operates in shared, unlicensed spectrum. Unlike mobile networks where operators have licensed, exclusive frequency allocations, WiFi APs have to coexist. That coexistence is governed by a set of rules — and when those rules are broken, or simply not well understood, you get interference. There are two distinct types of interference you need to understand: co-channel interference, which we call CCI, and adjacent channel interference, or ACI. Co-channel interference happens when two or more access points are operating on exactly the same channel and their coverage cells overlap. Because they're on the same channel, they can hear each other. The 802.11 MAC protocol — the medium access control layer — requires that devices wait for the channel to be clear before transmitting. This is the CSMA/CA mechanism: Carrier Sense Multiple Access with Collision Avoidance. When multiple APs are competing on the same channel, every device in that overlap zone has to queue up and wait its turn. The result is dramatically reduced throughput, increased latency, and a degraded client experience. In a high-density environment — think a conference hall with 500 delegates, or a hotel corridor with APs every fifteen metres — CCI is the single biggest performance killer. Adjacent channel interference is arguably worse, because it's less intuitive. ACI occurs when APs are configured on channels that are close together in frequency but not identical. In the 2.4 GHz band, each channel is 22 MHz wide, but the channels are only spaced 5 MHz apart. So if you put AP-1 on channel 1 and AP-2 on channel 3, their signals overlap in frequency. The problem is that the 802.11 protocol doesn't recognise this as the same channel — so the CSMA/CA backoff mechanism doesn't kick in. The two APs transmit simultaneously, their signals collide in the RF domain, and clients experience corrupted frames, retransmissions, and severe throughput degradation. ACI is often harder to diagnose because standard monitoring tools won't flag it as interference — the APs look fine individually. Now, the 2.4 GHz band only gives you three genuinely non-overlapping channels in most regulatory domains: channels 1, 6, and 11. That's it. Three channels for potentially dozens of APs across a floor. This is why dense 2.4 GHz deployments are so problematic, and why the industry has been pushing hard toward 5 GHz and now 6 GHz. The 5 GHz band is a fundamentally different proposition. Depending on your regulatory domain — and in the UK and EU, ETSI regulations govern this — you have access to up to 23 non-overlapping 20 MHz channels. With channel bonding at 40 MHz, that drops to around 11, and at 80 MHz you're looking at five or six. But even so, the spectrum is far less congested, and the shorter range of 5 GHz signals actually helps in dense deployments because it naturally limits the interference radius. The 6 GHz band, introduced under Wi-Fi 6E and now Wi-Fi 7, opens up an additional 1200 MHz of spectrum. In the UK, Ofcom has licensed the lower 6 GHz band for indoor use, giving you up to 24 non-overlapping 80 MHz channels. For new deployments in high-density venues, 6 GHz is the right architectural choice — but you'll still need to manage the 2.4 and 5 GHz bands for legacy device compatibility. So how do you fix this in practice? There are three layers to the solution. Layer one is channel planning. For 2.4 GHz, enforce a strict 1-6-11 channel plan across your AP estate. No exceptions. If you have more APs than you can fit into three non-overlapping channels without CCI, the answer is not to use channels 2, 3, or 4 — the answer is to reduce transmit power so that coverage cells don't overlap, or to migrate clients to 5 GHz. Layer two is transmit power management. This is where most deployments go wrong. Engineers install APs and leave transmit power at maximum, assuming more power means better coverage. In a dense deployment, the opposite is true. High transmit power extends the coverage cell, increases the overlap zone between adjacent APs, and amplifies CCI. The target is a received signal strength — RSSI — of around minus 67 dBm at the cell edge, with a cell overlap of no more than 15 to 20 percent. Most enterprise wireless controllers support automatic power control — Cisco's TPC, Aruba's ARM, Ruckus's ChannelFly — but these need to be tuned correctly and monitored. Layer three is Radio Resource Management, or RRM. Modern enterprise wireless systems include centralised RRM engines that continuously monitor the RF environment, detect interference, and dynamically adjust channel and power assignments. When configured correctly, RRM can handle the day-to-day optimisation automatically. But it's not a set-and-forget solution — you need to define the right thresholds, understand the scanning intervals, and validate that the system is making sensible decisions. Blind trust in RRM automation has caused more than a few outages. [IMPLEMENTATION RECOMMENDATIONS AND PITFALLS — approximately 2 minutes] Let me give you the implementation framework we use at Purple when onboarding a new venue. Start with a pre-deployment RF survey. Before you mount a single AP, walk the space with a spectrum analyser and identify existing interference sources — neighbouring networks, Bluetooth devices, microwave ovens in catering areas, DECT phones. In a retail environment, you'll often find interference from electronic shelf labels and RFID readers. In a hotel, the biggest culprits are neighbouring guest networks and poorly configured back-of-house systems. Next, design your channel plan on paper before you configure anything. For 2.4 GHz, map out which APs will use channels 1, 6, and 11, ensuring no two adjacent APs share a channel. For 5 GHz, use a wider channel plan — channels 36 through 64 for the lower UNII-1 and UNII-2A bands, avoiding DFS channels where possible in environments where radar detection could cause channel changes at inopportune moments — during a conference keynote, for example. Set transmit power conservatively. Start at 11 dBm for 5 GHz and 8 dBm for 2.4 GHz in dense deployments, then adjust based on post-deployment validation. Use your wireless controller's heat map tools to verify coverage. Enable band steering and load balancing. Modern clients support 5 GHz, and there's no reason to let them associate to 2.4 GHz if 5 GHz is available. Band steering pushes capable clients to the less congested band. Combined with client load balancing across APs, this significantly reduces the effective density on any single channel. Now, the pitfalls. The most common mistake I see is over-reliance on automatic channel assignment without validation. RRM systems are good, but they can make locally optimal decisions that create globally suboptimal outcomes — particularly in multi-floor deployments where APs on different floors share channels and interfere vertically. Always validate RRM decisions with a post-deployment survey. The second pitfall is ignoring the client side. A poorly performing client — an old IoT device, a legacy POS terminal — can consume disproportionate airtime and degrade performance for everyone on that channel. Implement minimum data rate policies to force low-rate clients off the network or onto a dedicated SSID. Third: don't forget about non-WiFi interference. Bluetooth, Zigbee, and other 2.4 GHz devices can cause significant degradation. If you're deploying BLE beacons for proximity marketing or asset tracking — which is increasingly common in retail and hospitality — make sure your WiFi channel plan accounts for BLE coexistence. Our guide on BLE Low Energy for enterprise covers this in detail. [RAPID-FIRE Q&A — approximately 1 minute] Right, let's do a few rapid-fire questions. "Should I use 40 MHz channels on 2.4 GHz?" — Absolutely not. With only three non-overlapping 20 MHz channels available, using 40 MHz channels on 2.4 GHz is guaranteed to cause ACI. Keep 2.4 GHz at 20 MHz. "Is Wi-Fi 6 enough to solve channel overlap?" — Wi-Fi 6 introduces OFDMA and BSS Colouring, which significantly improve performance in dense environments, but they don't eliminate the need for proper channel planning. BSS Colouring helps APs identify and deprioritise transmissions from other BSSs on the same channel, reducing CCI impact — but it's a mitigation, not a fix. "How often should I re-survey?" — In a static environment, annually. In a dynamic environment — a retail store that rearranges fixtures, a conference centre with changing room configurations — quarterly, or after any significant physical change. "What about the 6 GHz band?" — If you're deploying new hardware, prioritise Wi-Fi 6E or Wi-Fi 7 APs with 6 GHz radios. The spectrum is clean, uncongested, and the regulatory framework in the UK is now settled. It's the right long-term investment. [SUMMARY AND NEXT STEPS — approximately 1 minute] To wrap up: WiFi channel overlap is not a minor inconvenience — it's a fundamental architectural problem that directly impacts throughput, latency, client experience, and ultimately the commercial performance of your venue. The fix requires three things: a disciplined channel plan using only non-overlapping channels, conservative transmit power management to limit cell overlap, and properly configured RRM with ongoing validation. For your next steps: run a spectrum analysis of your current deployment this week. If you're seeing channels 2, 3, 4, 7, 8, or 9 in use on 2.4 GHz, that's your first remediation priority. If your 5 GHz APs are running at maximum power with 80 MHz channel widths in a dense environment, pull that back. Purple's WiFi analytics platform gives you continuous visibility into your RF environment, client distribution, and interference patterns — so you're not flying blind between surveys. Thanks for joining the briefing. If you want to go deeper on any of these topics, the full technical guide is available on the Purple website, along with our implementation checklists and case studies from hospitality, retail, and events deployments. Until next time.