The company is a 60-person e-commerce operation in Haizhu District: 500 sqm in total: office space, an 80 sqm warehouse and two meeting rooms. Its wireless network was three home routers, one at the front desk, one in the middle of the floor, one in the warehouse. Each dialed or bridged on its own, and each broadcast a different SSID: company, company-2, warehouse.
Open a video call in a meeting room and the connection drops. The warehouse barcode scanner often would not associate at all. Walking from a desk to the pantry kept the phone online but forced a manual Wi-Fi switch.
The owner asked whether he needed a more expensive router. He did not; the problem was the design, not the price of the box.
Diagnosis: three causes
We spent 40 minutes on site with NetSpot on a laptop and a channel-scanning adapter.
| Cause | What we measured | What it did to users |
|---|---|---|
| Co-channel interference | All three routers sat on 2.4 GHz channel 6, and 11 neighboring APs in the surrounding office towers were on the same channel | 2.4 GHz throughput fell to 8 Mbps, and the scanner, which is 2.4 GHz only, dropped packets constantly |
| No roaming | Three separate SSIDs left handover to each client, which clung on until -85 dBm | Phones clung to a distant AP while the user walked; video calls cut out mid-sentence |
| Placement and walls | The warehouse AP sat behind shelving with two load-bearing walls and metal racks in the path, measured at -87 dBm. The meeting rooms had no AP of their own and depended on penetration from the floor: -78 dBm | The two busiest areas were effectively offline |
Wi-Fi 6 handsets are already common here, and most staff phones support 6 or 6E. But a home router parked on a crowded 2.4 GHz channel cannot deliver speed no matter what connects to it. The equipment was never the weak link; the planning was.
The design: one AC, one SSID, eight APs
A single controller manages every AP. The floor broadcasts one SSID, and the APs hand clients off cooperatively, so the nearest AP serves whoever walks past and the change goes unnoticed.
AP placement came out of the survey, not out of a neat grid on paper:
- Office floor, 5 APs. Laid out in a staggered cellular pattern over the workstation area, each covering a 12-15 m radius, with 15-20% overlap between neighbors. Less overlap and roaming breaks; more and the APs interfere with each other.
- Meeting rooms, 1 AP. Independent coverage, so video calls do not fight wall attenuation. A meeting room also concentrates load, with 10 to 15 devices connected at once, and a dedicated AP protects that capacity.
- Warehouse, 2 APs. Metal racking is brutal on both 2.4 and 5 GHz, so these are aimed directionally, and the scanner stations get priority.
Channel planning: the step everyone skips
2.4 GHz offers three non-overlapping channels, 1, 6 and 11. 5 GHz offers far more, from 36 to 165. Our allocation:
| Band | Assigned to | Channel plan |
|---|---|---|
| 2.4 GHz | Barcode scanners, legacy printers and IoT devices only, compatibility first | Neighboring APs staggered across 1/6/11, with transmit power cut to 50% to limit cross-cell interference |
| 5 GHz | Every phone, laptop and video call | Channels outside the DFS range, such as 36/44/149/157, with at least two channels between neighbors; 80 MHz width enabled, narrowed to 40 MHz in dense areas |
| Band steering | Pushes dual-band clients onto 5 GHz first | Enabled globally on the controller; 2.4 GHz keeps only low-rate access |
Two more settings mattered. We disabled the legacy rates, 1, 2, 5.5 and 11 Mbps, so one old device cannot consume airtime for an entire AP. And we capped each AP at 30 clients, above which the controller steers new associations to a neighbor.
Equipment and what it actually cost
| Item | Model | Qty | Unit price | Subtotal |
|---|---|---|---|---|
| Wireless controller | H3C WX2540H, license included, manages 32 APs | 1 | RMB 3,800 | RMB 3,800 |
| Ceiling AP, Wi-Fi 6 | H3C WA6320, AX3000, dual-band | 8 | RMB 680 | RMB 5,440 |
| PoE switch | H3C S5130S-28P-PWR, 24-port gigabit PoE+, 370 W total | 1 | RMB 3,200 | RMB 3,200 |
| Egress gateway | Existing enterprise router retained; performance was adequate | - | RMB 0 | RMB 0 |
| Cable and consumables | Cat6A UTP, 305 m box × 2, PVC trunking, RJ45 plugs, faceplates | - | - | RMB 2,100 |
| Installation and commissioning | Cabling, 4 technicians x 2 days; AP mounting, controller configuration, channel tuning, acceptance report | - | - | RMB 4,800 |
| Total | - | - | - | RMB 19,340 |
The line item customers most want to cut is the installation, and it decides whether the project works. Cable routing, mounting height and angle, channel tuning and acceptance testing account for about 60% of the quality you end up with. The same hardware, installed well and installed badly, can differ by 20 dB at the same spot.
Before and after: the acceptance numbers
| Location | Before | After | Measured throughput (5 GHz) |
|---|---|---|---|
| Center of the workstation area | -58 dBm, channel 6 congested | -45 dBm | 620 Mbps |
| Meeting room, 10 people | -78 dBm, video dropped | -48 dBm | 540 Mbps; a one-hour call ran without stutter |
| Warehouse scanner station | -87 dBm, frequent disconnects | -56 dBm | 180 Mbps, scanner latency under 10 ms |
| Pantry and corridor roaming | Manual Wi-Fi switching | Seamless, handoff measured under 50 ms | - |
Remember two numbers: -60 dBm or better is excellent, and -70 dBm is the usable floor. Below -75 dBm you get obvious slowdowns and dropped connections. Test at every place people actually work, with a phone or an analyzer, not just under an AP.
Installation details that decide the outcome
- Mount on the ceiling, not the wall. A ceiling AP radiates downward and covers most efficiently; a wall-mounted unit gets blocked by furniture and by people. Aim for 2.8-3.5 m above the floor.
- Keep clear of metal and mains. Stay at least 1 m from metal ceiling grids, HVAC ducts and power cable trays. Metal reflects the signal and creates multipath fading.
- Size the PoE budget properly. A Wi-Fi 6 AP peaks at 20-25 W under 802.3at, so eight units need 200 W. Leave 30% headroom in the switch's total output; do not buy a "24-port PoE switch" that supplies only 150 W.
- Survey before you quote. A proposal written without visiting the site is either under-built, which shows as bad coverage, or over-built, which shows as a bigger invoice. We survey on site, draw the layout and quote anywhere in Guangzhou. The survey fee is RMB 500, credited against the contract.
- Wire everything that does not move. Fixed workstations, the meeting-room display host and the checkout counter all get copper; Wi-Fi serves mobile devices only. Taking the static devices off the air cuts airtime pressure roughly in half.
ACCPC runs enterprise wireless projects across Guangzhou: site survey, AP layout design, structured cabling, AC+AP installation and commissioning, channel optimization, and an acceptance report with measured signal and throughput at every measurement point, followed by annual warranty inspections. We also wholesale computers and components in Guangzhou, and networking procurement can be bundled. Call 020-39029800.