Signal Strength and Distance

A signal does not stay at full strength as it travels: wireless signals in the air and electrical signals in copper cable both lose strength, so the further data has to travel, the weaker the signal that arrives.

Wireless signals

The greater the distance between a device and the wireless access point it uses, the weaker the signal that reaches it. Strength drops with distance even in an open room, and drops much faster when the signal has to pass through walls, floors and other solid obstacles, which absorb part of the radio energy.

A weaker signal cannot carry data as quickly without errors, so the bandwidth available to that device falls and the same amount of data takes longer to arrive. If the signal drops below the minimum the device needs, the device cannot join the network, may not list the network as available, or may keep disconnecting.

For example, a referee's tablet at the far touchline of a school playing field, well away from the access point inside the sports hall, may take a few seconds to show the new score, while the same update appears almost instantly on a laptop in the sports hall. The weaker signal supports a lower bandwidth, so the update takes longer to arrive.

Copper and fibre optic cable

Wireless is not the only medium that loses signal. Copper Ethernet cable carries data as electrical signals, and these weaken over long distances, so the signal arriving at the far end of a long cable run is weaker than the one that was sent.

Fibre optic cable carries data as pulses of light and offers very high bandwidth. Light in the fibre weakens very little, so fibre signals travel much further than copper signals before they weaken significantly.