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androidandroid-wifi

Wi-Fi Aware scan throttling

Google introduced a set of limitations in Android 8 or 9 regarding Wi-Fi scanning frequency. Apps are restricted in how frequently they're able to scan for Wi-Fi connections, including P2P Wi-Fi peers. What is the situation with Wi-Fi Aware? Does it have the same limitation? Is it easier to bypass it?

Solution

  • This answer is as per the latest comments by OP.

    One way to keep track of the RSSI of the network is to register for the intent RSSI_CHANGED_ACTION using a BroadcastReceiver and then extract the raw RSSI values from the Intent's extra values which are stored with the key Wi-FiManager.EXTRA_NEW_RSSI and obtain the threshold levels(usually the workable values) using calculateSignalLevel(). Some approximate code:

        } else if (action.equals(WifiManager.RSSI_CHANGED_ACTION)) {
        // Default to -200 as its below WifiManager.MIN_RSSI.
        int rawRssi = intent.getIntExtra(WifiManager.EXTRA_NEW_RSSI, -200);
        int rssiLevel = mWifiManager.calculateSignalLevel(rawRssi);
    }

    Also, to answer the previous question as to whether Wi-Fi aware is restricted by the same scan restrictions, the answer is 'no', not because it has a waiver vis-a-vis Wi-Fi-Direct but because it operates differently from a Wi-Fi-Direct connection. For a Wi-Fi Direct connection, one needs to make a request() to the WifiManager for initiating a scan and it is these scans that are throttled, with the duration of throttling varying based on whether the app is in foreground/background. This throttling can of course be overridden from the Developer Settings page.

    Wi-Fi-Aware works with a different paradigm. If this is regarding the usage of ranging, then one can leverage Wi-Fi-Aware technology between two devices as follows:

    1. Check whether ranging is supported using Wi-Fi-RTTI apis using context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_WIFI_RTT);

    2. Check whether Wi-Fi RTT is available by registering for the intent WifiRttManager.ACTION_WIFI_RTT_STATE_CHANGED and on its receipt, check for whether Wi-Fi RTT is available.

    3. Create a ranging request

    4. Start ranging

    5. Extract rssi from a successful ranging result.

    One thing to note is that the requests for ranging are limited to 20 from each UID as per this code from the framework.

    static final int MAX_QUEUED_PER_UID = 20;

    Note that if you're running as a regular application, your app would have its own UID.