Latency is defined as the time it takes for a command to be instructed by Bob to be transmitted to Alice or vice versa.
This is critical for many applications like Video Chat, Remote Control, Video Games, and other applications. Typical latency for 4G is around 50-70ms
For remote surgery we need less than 1ms of latency, which is one of the critcal advances in 5G radio systems.
In Data Transfer
Two factors impact latency for data transfer
- The time packets spend in queues within the network
- Impact of TCP congestion control algorithm
- ECN to signal congestion before queues overflow
Propagation Delay
- The time packets spend propagating down the links between routers
- Speed at which light propagates through an optical fiber
- Speed at which electrical signals propagate down a wire
- Speed at which radio signals propagate through the air
How are people trying to combat propagation delay?
- Starlink uses signals through vacuum, i.e. to satellite, giving 47% reduction in latency