This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

CC3220: NWP behavior in case of multiple AP

Part Number: CC3220

Hello Team,

Could you please advise me how the NWP behavior for the following scenarios:

the customer used CC3220 AT command layer without any profiles, he using AT+WlanConnect to specific SSID name (not MAC address) than sending a few bytes and goes to sleep.

what happens in case of multiple routers with the same SSID (different MAC).

since the customer does not control which router (AP) the device (cc3220) decided to connect, what would happen in that case?

will the device select the strongest AP signal (RSSI) and then connect or will select one AP randomly, for example, if we got 2 AP one -50 dBm and the second with -60 dBm what the devices choose to connect to.

According the customer it turns out that after a lot of tests he, when the cc3220 connected to a certain AP, is constantly repeating to connect to the same AP even if the specif AP is shut down for while (and there are other AP with the same SSID are online) it will try every time connect to the same AP. only after RESET, the device managed to select another working AP to connect to.

there is a way to add a threshold which limits via certain RSSI level to connect AP? or reach to a situation that every time the device tries to connect to SSID the RSSI will take into account for the selection of which AP to connect to?

I'll greatly appreciate any suggestion, Thanks.

Sincerely,

Shai

  • Hello Shai,

    1. It depends on the connection policy you are using. For instance, in the "Auto" connection policy, the device selects the highest priority profile. If several profiles are within the same priority, the decision is made based on the security type (WPA \WPA2 > WEP > OPEN). If the security type is also the same, the selection is based on the received signal strength. To get more information on the device's connection policies, please refer to CC3120, CC3220 SimpleLink™ Wi-Fi® and Internet of Things Network Processor section 3.3.3.1 - Connection Policies

    2. Again, it depends on the connection policy. However, having multiple routers with the same SSID shouldn't be a problem as long as you leave the BSSID field null when you add the profile.

    You can double check this using the  "sl_WlanProfileGet" API

    3. Yes, the device lets users set an RSSI threshold as a scan parameter. For more information on how to do this, you can refer to CC3120, CC3220 SimpleLink™ Wi-Fi® and Internet of Things Network Processor section 3.7.2 - Setting Scan Parameters

    Thanks,

    Alexis

  • Alexis Hello,

    Sorry I did not mention that the full routine that I perform on every time that the device wakes up from hibernate, please find it below.
    again I'm working with AT command without any profiles or policy and I have 4 AP (Reuters) with the same SSID with security type OPEN to all of them.

    CmdWlanConnection request
    CmdGetWlan request
    + eventwlan: connect, SSIDWifi, 0x18: 0xf: 0x76: 0x1: 0x81: 0x54
    + eventnetapp: ipv4_acquired, xxx.xxx.xxx.xxx,xxx.xxx.xxx.xxx,xxx.xxx.xxx.xxx (cc3220 select 1 of 4 AP available
    in the area)
    +get: wlan_sta_connected (answer that module connected to AP)
    socket request
    + connect: 23101,xxx.xxx.xxx.xxx
    module connected to the host
    send data
    set of policy to none
    profile del = 0
    disconnect the AP
    request for stop = 2
    get into hibernate
    after 15 min of sleeping the routine get to act again over and over again.

    As I mentioned my problem occurs when the device wakes up and for some unknown reason it connects every time to the same AP although in my routine I do reset the policy to NONE and I delete all the profiles.

    But it seems to be these operations that I do are not delete the backend memory (when saved when it connects for the first time to one of AP in the area).
    What happens is that sometimes the device is trying to connect to the AP which is farther than others and the connection failed (even I got another 3 AP working properly)

    please advise how I can overcome this issue, maybe there is a way to delete all the back memory.
    just to let you know once I do RESET to the device, it starts work properly and connects to AP.
    This is an urgent case, we'll greatly appreciate your fast response here.
    Thanks

    Kind regards,
    Shai
  • Alexis, there is an update?
    Can you please advise if the customer using AT command lib, can we implanted the RSSI threshold in direct connection approach (without profiles).

    Looking forward to your reply!
    Thanks in advance.
    Shai
  • Alexis hello,

    I'm not a master at wifi connection protocol, but mine are thought are maybe could be a situation where my router (AP) blocks our device after a certain time because of an irregular connection behavior (our device have cycles of 15 minutes of hibernate and then wake up and connect to host and again goes to hibernate during 24/7 operation)
    Could you please advise back, thanks in advance.

    Kind regards,
    Shai
  • Hello Shai,

    There's really no guarantee that it won't connect to the same AP as long as they're all over the RSSI threshold. If you want to connect to the AP with the highest RSSI, i would recommend doing a scan, checking to see which has the highest RSSI value, and connecting based on that specific AP's MAC address.

    Thanks,
    Alexis
  • Alexis, Thanks for your inputs.
    But according to my client's working approach, he can not base his product on the MAC address, because he doe does not have control on the routers (expect SSID) of his end-customer this way he choose to work only with SSID approach.
    Thanks anyway.

    Kind regards,
    Shai
  • Shai,

    Performing a scan should return the BSSID, which is the MAC address.

    Thanks,
    Alexis