Hi all,
found the answer myself. If I want to use the ANT+ network I have to use the corresponding ANT+ network key. This is not an identification but rather a security messure and access control.
I found the following description in the document ANT Message Protocol and Usage the following paragraph:
5.2.5.2 Network Key
The network key is an 8-byte number that uniquely identifies a network and can provide a measure of security and access control. (...) Only channels with identical valid network keys may communicate with each other. (...)