Get different IP each time I run http://checkip.dyndns.com:8245/

I'm using an EDIMAX 3G-6200n (mobile) router, and want to set-up an IP camera on a remote site where I have to use mobile Internet. I have set-up port-forwarding on the EDIMAX router, and set-up a (free) DynDNS domain from http://DynDNS.org with TTL=60sec. Connecting my HUAWEI K3520 UMTS stick to the router, I can log-on to the Internet etc, but I'm not able to log-on to the camera from the Internet (using different computers and providers). The (wireless) LAN with the IP camera works fine.

From TROUBLESHOOTING I sofar learned the following:

• Fixed Internet connection: When I connect the EDIMAX router to my ADLS modem, and run http://checkip.dyndns.com:8245/ several times in a row, it returns a stable IP address. I can log-on to the camera via the Internet from anywhere using my DynDNS domain name.

• Mobile Internet connection: With my Laptop wireless connectet via the EDIMAX and Hauawei stick to the Internet and running http://checkip.dyndns.com:8245/, each run I get a different IP. In general the returned IP's look like : 62.133.64.8, then 62.133.64.7, 62.133.64.6 etc. Sofar I was not able to run the checkip-program so fast that it returned two times the same IP! I'm not able to log on via the Internet with my Domain name to the router/camera.

On a web-site related to DDNS I have read a comment that for Mobile Internet – DDNS does not work well. The IP-Addresses may have lease times of seconds only. This has indeed been confirmed by my checkip runs.

What do I have to do to get access to my router/IP camera via mobile Internet when the IP-address seems to live for seconds only?