The SCA is defined at PSM level using CORBA interfaces and XML DTDs. In contrast, the OMG PIM and PSM for SR components defines UML profiles for modeling SR concepts and PIM facilities that can be transformed into any technology.

The DTDs defined in the OMG specification are backward compatible with existing SCA DTDs but have been extended. These extensions allow component implementations to be decomposed into component assemblies and to express collocation semantics for components in an assembly. Also, some enumeration types were made string types for greater flexibility for industry usage and implementations.

The core framework (CF) and PortTypes CORBA module interface definition language (IDL) in the OMG specification are also broken into multiple files instead of condensed into one monolithic file (as in the SCA). This allows implementations of these interfaces to remain smaller in memory size as only the required interfaces are found in the executable software images.

The OMG specification, based upon lessons learned from several SCA core framework implementations, has also introduced changes to further optimize the following areas:

• Deployment optimizations — The meaning of property definitions and values for component definition, implementation and instantiation was simplified thus making installation and deployment much simpler and more understandable. Component connections were also simplified.

• Teardown optimization — The process of disconnecting component connections during an application release was simplified. In the SCA, disconnect call is on all application's deployed component and radio services. In the OMG, disconnections are only necessary for radio services not for deployed components since this is now handled by the component release behavior.

To address industry concern regarding the processing and memory overhead introduced by the SCA architecture, several interfaces and components were modified. These modifications have minimal impact on compatibility with the SCA as they continue to support existing SCA implementations seamlessly but allow for lighter-weight component definitions for other SR domains.

A LwAEP was added to the OMG software radio specification. This definition is lighter weight than one defined in the SCA 3.0 specification and corresponds to the recommended change proposal against SCA 3.0 that was supposed to make it lighter weight. SCA 2.2.2 did not include the LwAEP in its revisions but did reference a later POSIX specification (2003) for its profile definition.

In summary, the OMG PIM and PMS for SR components allows SDR developers to capture waveform and platform designs of SCA conformant systems in a manner that is independent of implementation technology. This allows SDR manufacturers to leverage existing SCA investments, provides a cost-effective mechanism for SCA evolution and enables SR technology insertion.

At the same time, the OMG PIM and PSM for SR components is flexible enough to accommodate commercial SDR domains since conformance is defined at the level of component and interface usage.

Author Note: Based on a paper presented at the SDR Forum's annual technical conference — SDR ‘06.

Dominick Paniscotti is VP and general manager, SDR Products at PrismTech. He has been involved in the design and development of software-defined radios since 1998. He is recognized as an industry leader in software communication architectures for SDR and is a co-founder of the Object Management Group Software Radio DSIG (recently renamed the Software Based Communication Task Force). He supports the commercial standardization of SDR technologies via groups such as the OMG and the SDR Forum. Paniscotti is responsible for PrismTech's SDR product strategy and the Spectra line of OEM developer tools and operating environments. He is an electrical engineering graduate from Fairleigh Dickinson University.

Jerry Bickle is chief scientist, SDR Products, PrismTech. He has been involved in the design and development of SDRs since 1997. He is leading the effort on the usage of CORBA, UML, MDA, XML and C++/C in developing an open architecture for software-programmable radios. He was the technical lead, and co-author with Dominick Paniscotti, for the JTRS Software SCA 2.2 specification. He has served as a member of the JTRS Technical Architecture Group that resolved SCA issues and created the initial set of SCA tutorial material. Along with Paniscotti, Bickle has helped lead the adoption of the SCA in the SDR Forum and the formation of the OMG Software Radio Domain Special Interest Group. He has been a main contributor on the evolution of the SCA as commercial standard within the OMG. Bickle is a graduate of Northern Illinois University.

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