A time synchronization mechanism based on Software Defined Radio of general-purpose processor

In recent years, Software Defined Radio (SDR) has become one of the major research concerns in mobile communications for the advantages of flexibility and versatility. Most of the air-interface processes such as signal processing and data multiplexing are done on a programmable software environment. The latest SDR platforms utilize the power of general-purpose processor (GPP) to perform all of the real-time computations and several wideband communication systems are prototyped. Nevertheless, the lack of universal real-time timing control and synchronization process make implemented GPP-based SDR platforms difficult to simulate time crucial multi-user cellular communication scenarios. Focus on the problem of time synchronization on SDR platforms, this paper presents a software-based time synchronization mechanism, which is called software time synchronization (STS). On that basis, a real-time and high precision clock source is designed on GPP-based SDR platforms and the multi-user communication system is synchronized utilizing round-trip delay (RTD) algorithm. Long-term experiments showed that a SDR prototype using STS is able to simulate TDMA-based cellular communications. The results also indicate that the STS synchronization errors are within several microseconds.