Hi Panda,
If you want to have Skype for Business Server functionality on mobile device, you need to deploy Mobility feature. Once it's deployed, your users can
connect to your Skype for Business Server deployment using supported iOS, Android and Windows Phone mobile devices.
The following diagram illustrates the flow of mobile application web requests for the Mobility Service and for the Autodiscover Service when using
an internal and external DNS configuration.

There are four services that comprise Mobility.
* Unified Communications Web API (UCWA)
* Mobility service (MCX)
* Autodiscover service
* Push notification service
You can learn more about how to plan, deploy and configure mobility for Skype for Business server as the following links:
https://docs.microsoft.com/en-us/skypeforbusiness/plan-your-deployment/mobility
https://docs.microsoft.com/en-us/skypeforbusiness/deploy/deploy-and-configure-mobility
Best Regards,
Sharon Zhao
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