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Answer
One of the new features in Wi-Fi 6 is a longer guard interval. The guard interval is used to help mitigate multipath or overlapping transmissions. This is done by adding a delay between symbols (set of 0s and 1s). The shorter the guard interval theoretically the faster the throughput but you are more susceptible to multipath due to metal and other reflective surfaces.
Wi-Fi 4 and 5 supported two guard intervals:
- Short - 0.4 microseconds
- Long - 0.8 microseconds
Wi-Fi 6 supports 3 guard intervals:
- Normal - 0.8 microseconds
- Double - 1.6 microseconds
- Quadruple - 3.2 microseconds
In Wi-Fi 6 the 1024-QAM allows up to a 4x longer symbol duration than in Wi-Fi 5, so the efficiency is still similar to Wi-Fi 5 even with Quadruple guard interval.
What guard interval should I use for various use cases?
A general rule of thumb should be:
- Normal - Use this in a clean open area without a lot of metal. This would also best be used outdoors. Normal Guard Interval is the best choice when throughput is of the utmost importance.
- Double - This is a good compromise between Normal and Quadruple. It will not provide as good of throughput as Normal but will reduce the likelihood of multipath in areas that are smaller or have some metal.
- Quadruple - This would be used in small areas or areas with a lot of metal. This would also be the best choice in areas with a lot of clients to reduce the overhead of retrying packets.