====== WiFi Regulatory Requirements ======

There is a very large body of regulatory and standards requirements which need to be met by any shipping product.

This page is meant to be a non-exhaustive introduction into the topic. This must not be treated as authoritative - any company or organisation wishing to create and ship a wireless device must engage the relevant regulatory bodies and create a suitable testing/certification plan.

===== General Overview =====

There is a lot of uncertainty around what exactly is required for any given wireless device. Although the rules vary from country to country, here are some general guidelines:

(TBD: flesh out with examples to specific regulatory requirements):

  * When an access point, laptop or other device is certified, the entire device is certified - this includes the laptop itself, the NIC and the antenna choice/configuration.
  * Certification may involved BOTH the hardware AND software.
  * Choosing an already certified NIC from a vendor does not bypass the requirement to certify the entire solution - if you place it in your own enclosure, with your own antenna configuration and customised firmware, you will have to re-certify the entire device.

===== NIC certification =====

Getting a NIC certified is a complicated task. The regulatory bodies require many things to be tested before certification is given. The following is not a complete, exhaustive list:

  * The NIC must be able to emit RF at the correct centre frequency. This is typically tested using a continuous TX tone test, using a calibrated spectrum analyser to check the centre frequency.
  * The NIC must meet some spectral emission mask - the requirements here may be different to the IEEE 802.11 spectral mask requirements. Typically this means the NIC must not distort transmissions and leak into adjacent channels; that the TX side has good TX filtering to meet these spectral mask requirements.
  * When utilising MIMO antennas, the total radiated power will be not necessarily be the straight sum of the per-chain TX power level. There may be other effects at play (eg STBC) which can change the power density of the signal at each antenna.
  * Since higher CCK/OFDM/MCS encoding rates have increasing power density, the total transmission power tends to be lower for each higher rate in order to meet the spectrum emission requirements.

===== Device certification =====

In addition to the NIC requirements, there are typically device requirements. The following is not an exhaustive list.

  * There are generally transmission power limits in different frequency bands - these may be specified across an entire transmission bandwidth (eg a dBi across a 20MHz channel) along with a spectral mask; others may specify a per-MHz maximum emission limit.
  * The transmission power limits tend to be effective radation (EIRP) rather than the output from the NIC (in dBm.) This means the antenna choice and configuration will play a part in the certification process.
  * When transmitting using multiple antennas (eg MIMO, phased array/smart antennas), the output radiated power is going to be a complex combination of both the per-chain transmission power and the antenna configuration/elements selected.

===== DFS device certification =====

When operating in the DFS bands in 5GHz, there are also strict regulatory requirements on a number of behaviours, including:

  * Implementing CAC (Channel access check) correctly - not transmitting anything during CAC, which includes probe responses and ACK frames;
  * Being able to accurately detect radar;
  * Being able to cease transmissions quickly upon detecting radar, and only emitting CSA IE's in the next few beacons (which advertise the new channel to move to);
  * Implementing some kind of channel spectrum management to "spread" 802.11 emissions across the whole band, rather than simply always using the lowest available channel number or some other non-fair mechanism.

This requires a separate certification for DFS compliance and again the entire device is tested and certified - including the processor board, wireless NICs, cabling, antenna selection, enclosure AND software.

===== Other reasons for transmission power limitations =====

There are three main reasons for limiting TX power:

  * There's a specific limitation for that particular channel and TX rate. Transmitting at higher TX rates does increase the power density and can lead to distortion at higher TX powers.
  * There may be an electronic reason for limiting TX power at higher rates - for example, the NIC may draw too much transient power and cause TX distortion or instability, or the output amplifier/filtering circuitry doesn't behave in quite as linear a fashion as the designers would have liked.
  * There are requirements at band edges ("CTL" edges) for more stricter spectral masks (so the 802.11 emissions at these band edges don't "leak" into the adjacent, non-802.11 licenced channel.) Typically this results in a lower TX power at the band edge in order to ensure the spectral mask at said band edge is below the required emission level into the adjacent band.

===== WiFi standards certification =====

(TBD)

===== Country specific regulatory requirements =====

==== Australia ====

The Australian regulatory body is the ACMA ([[http://www.acma.gov.au]]).
There may also be some requirements for antenna configuration and radiation patterns for fixed microwave services (TBD).