2 Replies Latest reply on Mar 20, 2019 11:50 PM by ZhengbaoZ_96

    Does someone know the details of roam scan?


      I am trying wifi roaming function on cyw43340.

      As we konw,when roaming works,it will scan channels.

      I want to konw which channels will be scaned and can I set up these channels?



        • 1. Re: Does someone know the details of roam scan?



            According previous reply in another thread, we have two setting for scan act.


          For example we have found same ssid "roaming AP" but in different channel with channel 6(associated) and 11(roaming target), but not trigger the switch mechanism.

          The roam function will scan based on channel 11 buffered in last scan every 10s.

          if we can't find any APs in the area, will start a full scan with 120s period.


          please correct me if I am wrong.

          dhd_conf_read_roam_params: roam_scan_period = 10

          //  scan the AP info on the channel every 10s  which is resulted in the previous scan results.


          dhd_conf_read_roam_params: fullroamperiod = 120

          //  if in scan_period sta failed to find useful AP,  starts a full channel scan, the period is 120.

          • 2. Re: Does someone know the details of roam scan?

            add more info:


            Roam Trigger (dBm):
            Optional value: -50, -55, -60, -65, -70, -75, -80, -85, -90, or Custom
            Preset value: -70! M3 B' T/ f- B4 k3 n, Y9 ]2 q9 d9
            Influence: high value will cause frequent roam scan


                    Roam Delta (dB):
                    Optional value: 5, 10, 15, 20, 25, 30, 35, or Custom o( y6 d" M6 _% R# p1
            Preset value: 10& g" `" [" m2 {5 I+ h
            Influence:  small delta will cause more roaming act happen.
                    Roam Period (second):
                    Optional value: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, or Custom
            Preset value: 10

            Influence: low value will cause more scan if roam is triggered.

            For instance: Roam Trigger = -65dBm
            Roam Delta = 5dBRoam Period = 5 second, when average RSSI value is -66dBm, at that time the station finds a AP its RSSI equals > -61dBmand station already was in association status for more than 5 seconds, the station will leave current AP and join the one with stronger signals.


              If in the same area one channel has more than two access points running, we need to set “Aggressive Scan” to OFF
            Aggressive Scan :
                    Optional value: On Off" h6 I# w9 a; @+ [3 ]& s
            Preset value: On7 M& m! a! i# S1 s3 V
               In addition if all the access points are set to channel 1, 6, 11,  we can preset the scan channels into 1, 6, 11 instead of all the 2.4G channels or 5G channels.  It will give a much quicker scan speed and improve the ratio of the roam. 
               BG Channel Set:
            Optional value: Full (all channels); 1,6,11 ; 1,7,13; or Custom 
                Preset value: Full

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