A generic encoding/decoding methodology for UMTS L3 messages based on ASN.1 and ECN

In the 3GPP UMTS specifications, different encoding/decoding rules are specified for different layer 3 (L3) protocol modules when transmitting/receiving message PDUs. For example, RRC messages are represented in ASN.1 format, whereas the messages of other L3 protocol modules (i.e. CC, MM, SM, GMM, SMS and SS) are represented in tabular formats. Also, some GMM IEs are represented in CSN.1 format and some SS IEs are represented in ASN.1 format. There is no generic encoding/decoding solution available that provides a standardized method for all L3 message PDUs. In this paper, we propose such a method by extending the use of ASN.1 enhanced with ECN for L3 protocol messages. The result is a generic and optimal encoding/decoding methodology, which is applicable to all L3 messages of the 3GPP protocol stack.