The meaning of the word “coexistence” is, according to one definition, “the act of living or existing together at the same time or in the same place” and is a perfect metaphor to describe the ideal end state of RF coexistence, in which RF signals utilize or exist in the same frequency bands, emanating from different transmitters and intended for different recipients and carrying different information. As our world becomes increasingly reliant on wireless communications, the congestion and contention for RF spectrum causes friction between incumbent users and newer, bandwidth intensive applications such as cellular communications.
Coexistence can be viewed as a set of metrics that define the level of performance of an RF device among other devices. A useful analogy is how well you can hear a person talking in a crowded room where lots of other people are also talking. Even when everyone is following the rules (i.e. not shouting or using a loudhailer), you may still be impacted by the other people present.