We have been working to add support for 3GPP Layer 3 binary messages into ASN1C.  These message types are not described using ASN.1 but rather by a tabular notation with complex bit patterns described using Concrete Syntax Notation 1 (CSN.1).  We have found, however, that it is possible to create a reasonable approximation of the formats using ASN.1.  We then added new configuration directives as well as the capability to substitute custom code into an ASN1C compilation to handle what could not be modeled directly with ASN.1.  The result is generated and run-time code to support these message types that fits within our framework  for supporting ASN.1.

We released a white paper earlier this summer which describes this methodology.  It is available on our web-site at https://www.obj-sys.com/docs/UsingASNtoDescribe3GPPMessages.pdf.   A reference implementation is also now available for the core layer 3 specifications (3GPP TS 24.007, 24.008, and 24.011) at https://www.obj-sys.com/lte_3gpp_apis.php.  Our plan is to have the full capability available in ASN1C v6.6 which is planned for release in January 2013.