Alvarion SW VERSION 5.1 system manual Avoiding Frequencies with Radar Activity

Chapter 4 - Operation and Administration

available. The SU should be configured with a minimal set of parameters to ensure that it will be able to automatically detect and use the frequency/bandwidth used by the AU, including possible changes in this frequency (Automatic Sub Band Select feature).

To simplify the installation process the SU scans a definable frequencies subset after power-up. The defined frequencies subsets may include frequencies from more than one Sub-Band, enabling automatic detection of both frequency and bandwidth. If the Best AU feature is enabled, the SU will scan the defined subset and the operating frequency/bandwidth will be determined by the Best AU mechanism (including the optional use of the Preferred AU feature). Otherwise the SU will try to associate with the first AU it finds. If no AU is found, the SU will start another scanning cycle.

4.2.6.2.3.2 Avoiding Frequencies with Radar Activity

In some regions, it is important to ensure that wireless access equipment does not interfere with certain radar systems in the 5 GHz band. If radar is being detected, the wireless access network should move automatically to a frequency that does not interfere with the radar system.

The country dependent set of parameters includes also an indication whether DFS (Dynamic Frequency Selection) should be used. The DFS algorithm is designed to detect and avoid operation in channels with radar activity. If the current sub-band does not support DFS, then the DFS parameters configuration submenu is not available.

When DFS is enabled, the AU monitors the spectrum continuously, searching for signals with a specific pattern indication radar activity. Upon detecting radar activity, the AU immediately stops transmitting on this frequency and starts looking for another radar-free frequency. The subset of viable frequencies is configurable.

The AU maintains a continuously updated database of all applicable frequencies, where each frequency is marked as Radar Free, Radar Detected or Adjacent to Radar. The AU attempts to check a new frequency only if it is marked as Radar Free. If a radar activity was detected on a certain frequency, it will be marked in the database as a Radar Detected frequency. The AU will not attempt to check for radar activity in frequencies marked as Radar Detected. A certain time after detecting radar activity on a frequency, it will be removed from the list of Radar Detected frequencies and will be marked as Radar Free. If radar activity was detected on a certain frequency, adjacent channels should not be used as well, according to the bandwidth. For instance, if the bandwidth is 20 MHz, then if radar activity was detected in 5800 MHz, frequencies 5790 MHz and 5810 MHz should not be used as well. These frequencies are marked in the database as Adjacent to Radar, and will be treated the same as Radar Detected frequencies.

BreezeACCESS VL System Manual

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