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Wireless LAN Network Requirements

A BE4000 customer site requires Wireless Local Area Network (WLAN) configurations for provisioning the wireless IP phones. We recommend that a Cisco certified partner with advanced wireless LAN specialization performs a customer site survey. During the survey, the Cisco certified partner should analyze the following:

  • RF spectrum to determine which channels are usable in the desired band (5 or 2.4 GHz)

  • Heat maps showing the intended coverage plan for the location

  • The access point platform type, antenna type, access point configuration (channel and transmit power). We recommend you to select an access point with integrated antennas for non-rugged environments (for example, office, healthcare, education, hospitality) and an access point platform requiring external antennas for rugged environments (for example, manufacturing, warehouse, retail)

Signal

The cell edge should be designed to -67 dBm where there is a 20-30% overlap of adjacent access points at that signal level. This ensures that the wireless IP phones always have adequate signal and can hold a signal long enough in order to roam seamlessly where signal based triggers are utilized verses packet loss triggers.

Also, ensure that the upstream signal from the wireless IP phones meet the access point’s receiver sensitivity for the transmitted data rate. Ensure that the received signal at the access point is -67 dBm or higher.

We recommend you to design the cell size to ensure that the wireless IP phones can hold a signal for at least 5 seconds.

Chanel Utilization

Channel Utilization levels should be kept under 40%.

Noise

Noise levels should not exceed -92 dBm, which allows for a Signal to Noise Ratio (SNR) of 25 dB where a -67 dBm signal should be maintained.

Also ensure that the upstream signal from the wireless phone meets the access point’s signal to noise ratio for the transmitted data rate.

Packet Loss or Delay

As per voice guidelines, packet loss should not exceed 1% packet loss; otherwise voice quality can be degraded significantly. Jitter should be kept minimal (< 100 ms).

Retries

802.11 retransmissions should be less than 20%.

Multipath

Multipath should be kept minimal as it can create nulls and reduce signal levels.