- Wireless troubleshooting can be divided into:
- Physical layer issues with signal strength or interference
- configuration issues
- when measuring wireless performances, distinguish between:
- bit rate
- the amount of total amount of data transferred per second established at the Physical and Data Link layers
- nominal link bit rate is determined by:
- standards support
- use of bonded channels
- optimizations
- if sender and receiver are far apart, or subject to interference
- a lower rate will be negotiated to make the link more reliable
- throughput
- is the amount of data that can be transferred at the Network layer
- disregarding overhead from layers 1 and 2
- goodput is used to describe data transfer achieved at the Application layer
- accounting for overhead from header fields and packet loss/retransmission
- radio frequency (RF) attenuation is the degradation of a signal as the distance between a radio transmitter and receiver increases
- aka free space path loss
- strength of signal decreases per the inverse-square rule
- e.g., doubling the distances decreases the signal strength by a factor of four
- interference sources collectively overlay a competing background signal
- loss of power/signal strength is measured in dB units
- e.g.,
- if
- transmit power is 14 dBm (~25 mW)
- antenna gain is 3 dBi
- free space loss over 30 meters is 70 dB
- then received signal strength is:
- if noise is -80 dBm
- signal-to-noise ratio (SNR) = 27 dB
- most sites aim for a margin of 20+ dB
- so there is enough margin for signal loss through typical indoor environmental obstacles
- e.g., budget 5 dB loss per internal wall
- signal strength and noise can be measured using a Wi-Fi analyzer
- can be installed to a laptop or smartphone
- records statistics for the AP that the client is currently associated with
- detects any other access points in the vicinity
- are dedicated Wi-Fi tester hardware devices