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CC3200: probe request packet and SCAN question

Jo Chen
Intellectual 2895 points
Part Number: CC3200

Hi Team,

my customer has questions regarding Probe request packets and SCAN channel question.

1. Probe request

my customer stored a SSID profile in cc3200 named IOT-Wireless, and perform Scan, he found the cc3200 sent out two probe packets at the same time on channel 5, one packet is with SSID=Broadcast; and another one is SSID=IOT-Wireless. (see below figure)

Note: Wistron_xx:xx:xx is the cc3200 device and “Aerohive_xx:xx:xx” is the AP .

the customer wants to know why there are two packets and to avoid sending the SSID=Broadcast packet because in his application, there are up to 100 cc3200 devices in one AP coverage and too many probe packets lead to congestion.

2. Scan channel

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/968/172.30.211.16-iot-2.4G.pcapng.7z

the Scan process should send probe packets on every channel (1-11), but in the sniffer log as attached, he can only find the packets on some specific channel like CH5. Is that because the stored SSID profile ever existed on CH5 or the Wi-Fi sniffer is not powerful enough to cover each channel?

Regards,

Jo

  • 0
    TI__Mastermind 38980 points
    Hi Jo,

    1. By default, a scan will look for all available SSIDs (Broadcast). What is looks like here is your customer also has Auto or Fast connection enabled, which at the same time is scanning for the specific SSID in your stored profile/last connected (IOT_Wireless). Can you confirm?

    2. What is your setup for sniffing multiple channels? As above, if you are using Auto or Fast connection, the NWP might start scanning on the last known channel and just move on to connect if it finds the stored SSID.

    Best regards,
    Sarah
  • 0 in reply to Sarah P
    TI__Intellectual 2895 points
    Hi Sarah,
    1. Yes, they used Auto connection.
    2. after clarification from them, they didn't use sniffer dongle, the log was from the Aerohive AP130/AP121 router managing tool. That's why there's only CH5 traffics, sorry for misleading.

    it is still not clear why the APs cannot handle over 10 cc3200 devices probe request packets, once happened, the AP is no longer connectable. But changing APs is not an option for the end-customer. Now the work around is they try to not use Auto connect and use manual connect instead.
    By the way, does cc32 support passive scan?
    regards,
    Jo