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Banner's Site Survey Feature

All Gateway devices are capable of running a Site Survey on the wireless sensor network. Site Surveys are conducted between the Gateway and each Node to analyze the radio signal strength and data transfer reliability between the two devices. DX70 devices report Site Survey results using the LEDs, with the flash rate indicating the radio signal strength. DX80 and DX9x Gateways report Site Survey results using the alphanumeric LCD display.

Interpreting the Site Survey Results

Site Survey results are listed as a percentage of data packets received and indicate the signal strength of the received signal.

Result	Description
	Packets received at a strong signal strength. A strong signal strength is greater than −90 dBm at the receiver.
	Packets received at a good signal strength. A good signal is between −90 and −100 dBm at the receiver.
	Packets received at a weak signal strength. A weak signal is less than −100 dBm at the receiver.
	Packets not received.

Judging if the reliability of a network’s signal meets the needs of the application is not simply a matter of green, yellow, and red packets received. In normal operating mode, when data packets are not received, the transmitter re-sends the packet until all data is received.

For slow monitoring applications such as a tank farm, where data is required in terms of seconds or minutes, receiving most of the data in the ‘red’ range, indicating a weak but reliable signal, transmits enough data for accurate monitoring. Nodes positioned near the outside range of the radio signal may have 90% of the data packets received in the red zone, again indicating a weak, but reliable signal.

A good guideline is to keep the missed packets average to less than 40%. When the network misses more than 40% of the data packets, the signal is usually too unreliable or obstacles may be interfering with the signal. When Site Survey reports the missed packets are 40% or higher, improve the radio system performance by:

• Mounting the network’s antennas higher,
• Using higher gain antennas, or
• Adding data radios to the network.

Mounting the devices’ antennas higher allows the radio signal to clear obstacles in the area and improves the line of sight between SureCross™ devices. Higher gain antennas will focus the energy of the radio signal in a specific direction and extend the signal’s range. Using data radios is another option to consider when trying to extend the range of a radio network.

Download Conducting a Site Survey and Interpreting the Results for a printable version of this information.