Meaning
The ability of wireless devices to transmit on the same frequency at the same time by using power control and distance creates higher overall capacity in a dense network area. Effective spatial reuse depends on the radio identifying which signals are far enough away to be ignored without causing a collision. This process is a departure from older protocols where any detected energy would stop a device from talking.
It applies to both indoor and outdoor deployments where multiple access points cover the same geographic space. The technique defines the boundary between a network limited by interference and one limited by physical space.
Power Regulation
The management of transmit levels is the primary tool for enabling multiple simultaneous conversations in a single area. For spatial reuse to work, every device in the network must use the lowest power necessary to reach its intended recipient. This reduction in signal footprint prevents a single device from occupying a large volume of the radio environment.
If every station transmits at maximum power, the channel remains busy for everyone and the benefits of the technique are lost. The system uses feedback from the receiver to adjust the power level in real time. This behavior ensures that the signal stays strong enough for high data rates but weak enough to stay out of the way of others.
This regulation is a requirement for the operation of dense cellular and wifi systems.
Interference Handling
Modern wireless chips include advanced algorithms for distinguishing between a local signal and a distant interfering source. When spatial reuse is active, the radio compares the signal strength of an incoming frame to a threshold that determines if the medium is truly busy. If the energy is below this level, the station can choose to transmit its own data anyway, assuming the collision will be avoided.
This decision making is complex because it must account for the possibility that the other transmission might also increase its power or change its modulation. The hardware must be able to handle a high level of background noise while still decoding its own data correctly. This capability is a direct result of improvements in digital signal processing and receiver design.
It allows for a more efficient use of the air in crowded urban environments.
Capacity Increase
The cumulative effect of many devices talking at once is a dramatic improvement in the total amount of data the network can move. Through the application of spatial reuse, a single office building can support hundreds of high speed connections on a small number of channels. This increase in capacity is measured as the total throughput per square meter of floor space.
Without this ability, the network would collapse as soon as more than a few people tried to use it at the same time. The technique is particularly important for the deployment of small cells in cellular networks and high density access points in wifi networks. It represents a shift in focus from the performance of a single link to the performance of the entire system.
The final capacity of the spectrum is determined by how well the hardware can reuse the same frequencies in close proximity.
