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802.11, Spectrum Stuff

Is a guard interval just dead air?

The purpose of a guard interval is to reduce data corruption caused by multipath. Multipath occurs when a transmission reaches an antenna using multiple paths. This is often caused by reflection, refraction etc.

The delay between receiving the first transmission, and the second is referred to as delay spread. When the delay spread coincides with a second transmission of data, it can cause data corruption to the first. This is the reason why guard intervals are used within wireless communication.

With OFDM, the guard interval can be inserted in two different ways. It can either be padded with zero´s, or it can be the inverse of the last few symbols in a transmission.

More information on Guard Intervals for OFDM > Here

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