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An approach for solving real-time and synchronization issues in heterogeneous multi-processor software defined systems

: Troll, P.; Buchin, B.; Fazel, K.; Adrat, M.

Pucker, L. ; The Wireless Innovation Forum:
WInnComm-Europe 2019, Wireless Innovation Summit on Wireless Communications Technologies. Proceedings : 15-15 May 2019, Berlin, Germany
Rome: Wireless Innovation Forum, 2019
Wireless Innovation Summit on Wireless Communications Technologies (WInnComm-Europe) <2019, Berlin>
Conference Paper
Fraunhofer FKIE ()

Real-time and synchronization issues have been subject to deliberation – and a source of potential confusion – since the invention of computers and their application in technical systems. They also are core issues of Software Defined Systems (SDS) and Software Defined Radio (SDR) as they are distributed real-time systems requiring a precise measurement of time and time-exact execution of commands. Taking into consideration that waveform portability is one of the primary objectives of SDR, the use of universal, simple and easy-to-use concepts is paramount which allow the provision of waveform agnostic Application Programming Interfaces (APIs) by the host environment. Waveform specific solutions can then be designed employing the APIs and the universal concepts they encapsulate. Due to further objectives like scalability and broad applicability in various fields, numerous standards have evolved over the years, that address real-time and synchronization issues in the SDR-ecosystem, e.g. IEEE/OMG POSIX, SCA, the JTRS/JTNC standards and the WINNF specifications. They allow for diverse approaches to synchronization and in some cases orthogonal solutions, e.g. “Absolute Time” vs. “Relative Time” within the WINNF Transceiver Facility PIM specification. In this contribution, we will sketch how through the systematic combination of well-established concepts from these standards a comprehensive – but nevertheless simple – strategy to support real-time and synchronization issues in SDS is possible. The strategy is applicable both to SCA as well as to non-SCA host environments. To give an example that relates to practice, we will exemplify the application of the strategy to a common hardware architecture that includes an FPGA and a DSP or GPP as computational elements (CE) and we will look into the specific real-time aspects of the different types of CEs. The central ideas the strategy is based on are:
- Consequent application of the concept of a “system-wide monotonic clock”.
- Utilisation of the real-time capabilities of FPGAs in combination with APIs that allow real-time capable implementations, like the JTRS Modem Hardware Abstraction Layer (MHAL) on Chip Bus (MOCB) API.
- Fostering waveform portability by provision of a “lean platform” that features a clear separation between universal functionality of the host environment and waveform specific functionality in the applications. This paper is about synchronization in SDS in general, with focus on SDR system’s core challenge of how the host environment can enable an application to synchronize on the air interface.