Android如何选择wifi AP

Question

I am currently working on a indoor location paper using wifi systems. The problem is that some devices are not working as expected. So i have 2 questions

1) How really factory default android select the AP and how it decides to change to another AP, does it has any trigger threshold?.

2) This process is for all android distributions or it will depend of vendor.

Best regards. Also if you have some docummentation, books, etc will be usefull.

Answer 1

This is not programming related question! Off topic.

But sharing my knowledge just to ease your situation-

1) How really factory default android select the AP and how it decides to change to another AP, does it has any trigger threshold?.

Initial Ap selection -

1. RSSI(Recieved signal strength Information) based. But this is not strict. There can/cannot be overridden by join band preference (2.4G, 5G) in wifi firmware. Depends on vendor implementation.
2. In case of passpoint enabled APs- IEEE 802.11u provides network discovery and selection algorithms for discovery of suitable networks (preassociation) through the advertisement of access network type, location information.

Roam from AP to AP

This is again based on various factors and cannot say strictly because different vendors can have different algorithm to choose better available AP.

1. RSSI based- if station RSSI is less than RSSI roam trigger value in wifi driver.(means do roam at a low signal strength)

2. Beacon Loss- If station is missing beacons from current AP. out of range, turn off AP etc.

3. In case of enterprise networks- This can be managed by enterprise network controller administrators.

For your second question- yes , Definitely different vendors(wifi vendors as well as device vendors) can have their own implementation.

This is just basic idea. May be you need to study more about this.