Wi-Fi module (802.11 WLAN): bands, MIMO streams and host interface

01

Pick bands, streams and the host interface

Fn-Link's 6252M-PUB shows a high-throughput module: a Realtek RTL8852BE-based 802.11a/b/g/n/ac/ax (Wi-Fi 6) and Bluetooth 5.2 module with 2T2R MIMO, a 1,200 Mbps data rate, 20/40 MHz channels at 2.4 GHz and 20/40/80 MHz at 5 GHz, a PCIe interface for WLAN and USB for Bluetooth, external antennas, 3.3 V supply, 22 × 30 × 2.2 mm, 0 to 70 °C operation, and drivers listed for Android, Linux and Windows. [2]

Qiyang's RTL8188CUS module shows a basic one: an 802.11b/g/n, 2.4 GHz-only USB 2.0 module with an external antenna interface, up to 150 Mbps, 3.3 to 5 V DC and 95–140 mA operating current. [3] Between them, Beijing Jia An's TA3301NA-C is a 2.4 GHz Wi-Fi 6 and Bluetooth LE 5.4 system-in-package module on TI's CC3301, 1×1 802.11b/g/n/ax, with WLAN connected to the host processor over SDIO and Bluetooth over UART. [4]

Editorial calculation: 1,200 Mbps over two streams is 600 Mbps per stream, eight times the 150 Mbps headline rate of the single-band USB module. A link rate is not a measured throughput, so ask the supplier for measured TCP throughput on your host and channel width.

Give the supplier the bands, 802.11 generation, MIMO chains, channel widths, host processor and OS, host interface, antenna arrangement (onboard or connectors, gain), required certifications and markets, operating temperature, and the throughput and range you need.

02

Check the 5 and 6 GHz power and DFS rules

In the US, 47 CFR 15.407 sets U-NII limits by band. In 5.15–5.25 GHz an access point may conduct up to 1 W with up to 6 dBi antenna gain and 17 dBm per MHz, while a client device is limited to 250 mW and 11 dBm per MHz. In 5.25–5.35 and 5.47–5.725 GHz the limit is the lesser of 250 mW or 11 dBm + 10 log B (B being the 26 dB emission bandwidth in MHz), with 11 dBm per MHz, and above 6 dBi the power must be cut by the excess gain. [1]

Devices in 5.25–5.35 and 5.47–5.725 GHz must use transmit power control (able to run 6 dB below 30 dBm mean e.i.r.p., unless below 500 mW e.i.r.p.) and radar detection (DFS): after radar is detected they must stop transmitting on the channel within 10 seconds, sending normal traffic for at most 200 ms, and keep off it for at least 30 minutes. [1] Editorial calculation: for a 20 MHz bandwidth, 11 + 10 log 20 ≈ 24 dBm, which equals the 250 mW cap (24 dBm), so wider channels gain no extra conducted power in these bands.

In 5.925–7.125 GHz an indoor access point, and a client under its control, is limited to 5 dBm e.i.r.p. per MHz and 30 dBm in total; standard-power access points in 5.925–6.425 and 6.525–6.875 GHz may reach 23 dBm per MHz and 36 dBm. [1] Editorial calculation: at 5 dBm per MHz a 160 MHz channel reaches 5 + 10 log 160 ≈ 27 dBm, below the 30 dBm cap. Note that the 6252M-PUB lists 5 GHz coverage only up to 5.845 GHz and no 6 GHz band, so 6 GHz needs a module that lists it. [2]

03

Read transmit power and sensitivity per rate

Qiyang lists the RTL8188CUS module's transmit power by mode, below 18 dBm for 11b, 14 dBm for 11g and 13 dBm for 11n, and receive sensitivity by rate: −86 dBm at 11 Mbps, −73 dBm at 54 Mbps and −66 dBm at 130 Mbps. [3]

Editorial calculation: from 11 to 130 Mbps the module needs 20 dB more signal (−86 to −66 dBm). Ask for the power and sensitivity table at the rates and channel widths you will use, and for each band separately on dual-band modules.

04

Chipset, bands, MIMO chains, drivers and certified antennas to confirm per module

Ask each supplier for the chipset, bands, MIMO chains, host interface, driver and OS support, transmit power and sensitivity tables, and the certifications held with which antennas.

05

WLAN chipset, RF front end, antenna connectors, host interface, shield can and Bluetooth

06

Bands, data rate, transmit power, sensitivity and antenna gain for an 802.11 module

Put the antenna gain in the order data: US U-NII rules cut the permitted power by the amount the antenna gain exceeds 6 dBi. [1]

07

Send the band, host and certification data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Bands: [2.4, 5, 6 GHz; 802.11 generation]
MIMO: [1T1R, 2T2R; channel widths]
Host: [processor; OS; PCIe, SDIO or USB]
Antenna: [onboard or connectors; gain]
RF: [power and sensitivity tables needed]
Certification: [markets; DFS; antennas]
Environment: [temperature; supply]
Throughput: [target; test method]

See manufacturer records Send an enquiry through CNFX