Wireless Networks: Performance and Measurement

Performance Variability

• Performance varies based on:
  • Location relative to the access point
  • Environmental variables

Measuring Performance

• Throughput: Amount of data transferred at any time
• Connection Speed: Affected by proximity to the access point

Received Signal Strength Indication (RSSI)

• RSSI: Measures signal strength on a device
• Measured in decibels per milliwatt (dBm)
• Scale:
  • Closer to 0 is better
  • Excellent: -50 dBm and higher
  • Good: -70 dBm
  • Low signal: -80 dBm and smaller
• Tools: Wireless survey tools to collect RSSI and noise values
• Interference: High noise values indicate potential interference

Transmitting Signal

• Effective Isotropic Radiated Power (EIRP): Measures transmitted signal strength
  • Calculated by transmit strength, antenna gain, minus cable loss
• Regulations:
  • FCC limits for 2.4 GHz access point is 36 dBm (~4 watts)
• Control: Owner can adjust signal output on access points

Antenna Types

• Omnidirectional Antennas:
  • Even signal distribution
  • Effective for central positioning
• Directional Antennas:
  • Focus signal direction, increase distance
  • Types include Yagi and Parabolic antennas
  • Gain increase, e.g., 3 dB gain doubles power

Antenna Polarization

• Polarization: Orientation relative to earth (horizontal or vertical)
• Must match between transmitting and receiving antennas for efficiency

Access Point Association

• Association Time: Time taken for devices to connect to an access point
• Factors Affecting Association:
  • Distance from access point
  • Connection to wireless controller
  • Firmware issues
  • Number of users on the access point

Frequency and Interference Management

• Frequency Limits: Limited availability can cause delays with high user numbers
• Settings Optimization:
  • Disable legacy or low-speed modes
  • Adjust access point frequencies
  • Modify output power to manage interference

Site Surveys

• Identifies signal strengths across different building areas
• Helps manage interference from third-party access points
• Ongoing surveys advised to track changes
• Heat Maps: Created with third-party software to visualize signal strengths