Channel Occupancy
Channel occupancy is the measure of how much of a given channel is filled with transmission over time. As the number of sets working on the same site rises, occupancy rises and packet collisions begin. In multi-set operation the real limit is not the number of device identities but this sharing of time.
Each transmitter occupies the channel only for as long as it transmits. Occupancy is roughly the sum of the times on air of the transmitters using the same channel. When occupancy rises, two packets overlap, both are corrupted and both sides retry; since the retries raise the occupancy further, the system can degrade quickly.
- Short packets: reducing the time on air directly lowers occupancy.
- Random backoff: adding randomness to the retry intervals breaks continuous collision.
- Frequency hopping: sets using different patterns rarely meet on the same channel over time.
- Listen before talk: deferring transmission when the channel is busy prevents collision.
On the AXI side, the dump data states support for multi-kit operation on the same site for the XRF protocol used in the HCT400 and HCT402 sets; its technical basis is the frequency hopping architecture and the unique pairing identity per device. Even so, if a large number of sets is to work in the same area, the layout and the antenna distances should be planned.
Context where this term is used: Wireless remote control installation: pairing, relay, safety