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245U-E Wireless Ethernet Modem User Manual
89
Rev Version 2.24
Channel Utilization on a Live System
Channel utilization can be used on a live system to get an indication of how much spare capacity the
channel has for additional data transfer. To identify possible interference on the current channel, observe
the Percent Busy and Percent Rx on the Custom Survey page. If possible, also temporarily disable all data
transfer on the system. If the channel utilization remains high it will confirm the presence of interference.
Channel Utilization for Channel Selection
or RF Path Testing
When used on an inactive system, channel utilization will indicate how quiet the current channel is, and
therefore indicate how much interference is present. To select the quietest channel, configure the radio as
an access point with no data transfer, and on each channel of interest record the channel utilization over a
period of time. The channel with the lowest utilization will be the quietest channel and therefore is likely
to provide the best performance. This procedure, in addition to a throughput test, is recommended for
complete radio path testing.
Diagnosing Low Throughput
When Iperf throughput testing has given poor results, channel utilization can be used to confirm whether
or not the poor results were due to interference. If the channel utilization (excluding the time period while
Iperf was running) is seen to be high, then this will confirm that the poor throughput was due to other RF
interference. Alternatively, if the channel utilization is seen to be low (indicating little interference), the
poor throughput is more likely to be attributed to poor RSSI, which could be confirmed on the Connectivity
page.
Solutions for High Channel Utilization
When substantial interference has been identified using Channel Survey or Custom Survey, the simplest
solution is to change to another channel that appears to have lower channel utilization. If a better channel
is not available, configuring a fixed noise floor can often greatly improve performance. Configuring a fixed
noise floor can be performed on the Advanced Radio Configuration page. The fixed noise floor should be
at least 8 dB greater than the weakest RSSI of any connected modem, otherwise communications could be
lost. After configuring the fixed noise floor, confirm that the channel utilization has dropped to a desirable
level, and where possible perform a throughput test to confirm acceptable performance.
The Channel Survey screen displays a graph showing the percentage of time that a channel is being utilized
by any of the following causes:
• The connected modem is transmitting.
• The connected modem is receiving valid data from another modem.
• The connected modem has detected RF noise or interference.
The Channel Survey shows the channel utilization and noise floor graph with 1-second, 1-minute and
1-hour periods.
Figure 80 shows a percent of the overall radio traffic on the channel that is currently being used.
