Interference Issues
- interference is likely when
- signal is weak
- cannot get a connection
- yet device is in range
- sources of interference:
- CCI
- ACI
- reflection/bounce (multipath interference)
- mirrors or shiny surfaces cause signals to reflect
- introduces a variable delay
- causes packets to be lost and data rate to drop
- Wi-Fi 4/5/6 use bounce as a means of optimizing throughput and range via MIMO
- refraction
- glass or water can cause radio waves to bend and take a different path to receiver
- causes data rate to drop
- absorption
- refers to the degree to which walls, windows, and people will reduce signal strength
- some radio wave energy is lost as heat when passing through construction material or human bodies
- internal wall may cost 3-15 dB
- 2.4 GHz frequency has better penetration than 5 GHz
- use ceiling mounted AP to minimize absorption from furniture
- electromagnetic interference (EMI)
- interference from a radio or electromagnetic source in same frequency band
- e.g., bluetooth, cordless phone, microwave
- detect EMI with spectrum analyzer
- must use a special radio receiver
- Wi-Fi adapters filter out all non-Wi-Fi signals
- usually are handheld units with a directional antenna
- 6 dB change in level of a source represents a halving or doubling of the distance between the analyzer and RF source
- network attacks