Using RF Analysis on SonicPoint(s) RFA uses scores, graphs, and numbers to assist users to discover and identify potential or existing wireless problems. Although the best case scenario is to have the smallest number of APs working in the same channel at any given time, in the real world it is difficult to maintain that especially when deploying large amount of APs. Also, since the ISM band is free to the public, there may be other devices operating that are out of immediate control of the network administrator. Topics: • Channel Utilization Graphs and Information • Making Sense of the RF Score • Viewing Overloaded Channels • RFA Highly Interfered Channels Channel Utilization Graphs and Information Searching for a way to show how a channel is utilized for all connected SonicPoints resulted in channel utilization graphs as shown below. There are two color bars for each channel. The number on the top of each color bar indicates the number of SonicPoints that detects the particular issue in that channel. SonicPoints perform an IDS scan on all available channels upon boot-up, and RFA analyzes these scan results to decide on issues for each channel. For example: if there are 10 SonicPoints connected, and 6 of these decide that channel 11 is overloaded, the number on the top of purple color bar is 6; if 8 SonicPoints decide that channel 6 is highly interfered, the number on the top of the cyan color bar is 8. Zero is shown for channels no issues. NOTE: Channels 12, 13, 14 are shown, but in some countries these channels are not used. These channels are still monitored, however, because it is possible for a wireless cracker to set up a wireless jammer in channel 12, 13, or 14 to launch a denial-of-service attack to lower channels. Making Sense of the RF Score RF Score is a calculated number on a scale of 1-10 which is used to represent the overall condition for a channel. The higher the score, the better the RF environment is. Low scores indicate that attention is needed. SonicWALL wireless driver report signal strength in RSSI, this number is used in the below equation to get a raw score on a scale of 1 to 100. Preliminary RF Score Formula: • rfaScore100 = 100-((rssiTotal-50)*7/10)) simplified: rfaScore100 = -0.7*rssiTotal + 135; A final score is based on this rfaScore100: • If the RFA score is greater than 96, it is reported as 10. • If the RFA score is less than 15, it is reported as 1. • All other scores are divided by 10 in order to fall into the 1-10 scale. In the SonicOS interface, the RF Score is displayed for the channel that is being used by the SonicPoints. NOTE: This feature depends on the knowledge of what channel SonicPoint is operating in. If the channel number is unknown, RF Score is going to be not available. Viewing Overloaded Channels RFA will give a warning when it detects more than four active APs in the same channel. No matter how strong its signal strength is, RFA will mark the channel as overloaded, as shown in the following figure. Figure 10. Overloaded channels Information about each discovered AP includes: SSID, MAC, signal strength, and channel. Two values are shown for signal strength: dBm and percentage value. RFA Highly Interfered Channels Not only APs working in the same channel will create interference, APs working in adjacent channels (channel number less than 5 apart) will also interfere with each other. RFA delivers a warning when it detects that around a certain SonicPoint, there are more than five active APs in the channels that are less than five apart. No matter how strong their signal strength is, RFA will mark the channel as highly interfered. Figure 11. Highly interfered channels Information about each discovered AP includes: SSID, MAC, signal strength, and channel. Two values are shown for signal strength: dBm and percentage value.
