The Spectrum Analyzer is used to scan the spectrum to select a channel with the least interference during a link setup. The spectrum is scanned to compute maximum and minimum Received Signal Strength Indication (RSSI) on each channel. (RSSI is a measurement of the power present in a received radio signal). The Max and Min RSSI values on each channel are calculated by considering the channel noise. The Spectrum Analyzer scans only the channels configured based on country while considering regional regulations.
The antennas of the transmitter/receiver radios need to be physically aligned to have the best possible link between them. Proxim provides three options for the most accurate alignment:
- Audible Antenna Alignment
- Using CLI
- Using Link Test
Audible antenna alignment tool can be activated by plugging in the supplied serial dongle or by issuing the CLI command for antenna alignment. The CLI command enables both audible and numerical feedback as the CLI shows the running Signal-to-Noise Ratio (SNR) values twice a second.
The output from the beeper for antenna alignment consists of short beeps with a variable interval. The interval changes with the SNR level to assist in correctly aligning the antenna. An increase in signal level is indicated by a shorter interval between beeps; a reduction in signal level results in beeps further apart. . When a higher SNR is received, the beep period is made shorter, dependent upon the difference to the average. A lower SNR results in a longer period between beeps. When the antenna is aimed, the beep intuitively represents whether the SNR is rising (shorter period, higher frequency) or falling (longer period). Aiming is complete if moving in any direction results in a falling SNR value, which can be heard as longer periods between beeps.
While using CLI for antenna alignment, CLI commands need to be used to enable the display of the local and remote SNR. Local SNR is the SNR measured by the receiver at the near end and Remote SNR is the SNR as measured by the receiver at the far end.
The WORP® Link Test is another option to align the antennas. WORP® Link Test is part of the management tools that comes with the radio unit to analyze the radio link quality. Link Test shows, in graphical form, Signal and Noise levels at which packets are received at local and remote unit. The Link Test option displays the radio signal strength in relation to the noise in the signal path. These metrics can be used to optimize the antenna alignment by making modifications in the antenna orientation.
Dynamic Data Rate Selection (DDRS) feature allows the BSU or SU to monitor the remote average signal-to-noise ratio (SNR) and the number of retransmissions between the BSU and SU or vice versa. The BSU or SU adjusts the transmission data rate to an optimal value to provide the best possible throughput according to the current communication conditions and link quality. The BSU or SU runs the DDRS Algorithm separately based on their local DDRS Status configuration. When DDRS Status is enabled on the SU, it monitors the remote SNR and number of retransmissions for BSU and can adjust the transmission rate according to the link condition.