D-Link Wireless Broadband Router DWR-921
Support 4G SIM Card
Commonly, Internet Service Provider (ISP) does not give Dynamic Public IP to wireless broadband to the subscriber. But certain ISP will give Dynamic Public IP upon request. So you are required to clarify with your local ISP.
Here is the step to confirm your existing Wireless Broadband has come with Dynamic Public IP or not.
First, log in to the router configuration page (main page). And open http://yougetsignal.com > Port Forwarding Tester. As see below.
Comparing the WAN IP as see on the DLINK router and the WAN IP from Port Forwarding Tester, If it is different, meaning you are getting "Private IP address" from your Wireless Broadband ISP.
Proceed to configure Port Forwarding if it is Dynamic Public IP address