Time Synchronization in Software-Defined Radio Subsystems
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Solution Overview
Problem
Current software-defined radio systems face challenges in accurately synchronizing the time of day between multiple processors and processes due to limitations in message exchange accuracy, particularly with interrupt latency and timing variability.
Innovation Solution
Implementing a system where a real-time clock is used to determine the time of day, distributed via a global hardware timing pulse, with each processor having a free-running timer and registers that increment in unison, using a Common Object Request Broker Architecture (CORBA) for synchronization, ensuring accurate time synchronization across radio subsystems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If message exchange between processing elements is used for time synchronization, then the system can achieve basic timing coordination, but the synchronization accuracy is limited due to interrupt latency and timing variability
Solution Approach 1:
A dedicated hardware timestamp counter serves as an intermediary between the external time source and multiple processing elements. This counter receives time information from an external source (such as GPS or network time protocol) and simultaneously provides synchronized timestamps to all processing elements through hardware connections, eliminating the need for message exchange and associated interrupt latency.
Solution Approach 2:
The patent replaces the software-based message exchange mechanism with a hardware-based timestamp distribution system. By using dedicated hardware timestamp counters and direct hardware connections to distribute time information, the system eliminates the software interrupt overhead and timing variability inherent in message-based synchronization approaches.
2Measurement precision
If software-based time synchronization is implemented, then the system structure remains simple, but the timing precision cannot meet the less than one microsecond requirement
Solution Approach 1:
The time synchronization function is segmented into dedicated hardware timestamp counters in each processing element, rather than using a centralized software timekeeper. Each processing element has its own hardware counter that independently receives and records time information, distributing the synchronization function across multiple independent hardware units.
Solution Approach 2:
The patent combines the time reception and time distribution functions into a unified hardware timestamp counter system. The same hardware counter that receives time from external sources also directly provides timestamps to all processing elements, merging what could be separate functions into a single integrated hardware solution.
Data Source
AI summary
A software-defined radio includes a pair of radio subsystems such as a red (command) and black (data) radio subsystem having an operating environment conforming to the Software Communications Architecture (SCA) specification, for example, as used for Joint Tactical Radio System (JTRS). A clock is read by at least one of the radio subsystems for determining time of day. A processor of the radio subsystem is operative for distributing the time of day to the radio subsystems using a global hardware timing pulse. Each processor can include a free-running timer to which any time sources within the pair of radio subsystems are set.