Since the first gas-powered cars appeared in the 1880s, vehicles have steadily gained a range of new functionalities, from digital dashboards to sophisticated safety features. Despite these advances, their use of radio signals has remained rather inefficient.
Modern vehicles are often equipped with two or more separate radio frequency systems, and attempts to integrate their functions into unified hardware have typically led to trade-offs. The signals used for sensing the environment and for communicating with other devices— called Frequency-Modulated Continuous Wave (FMCW) and Orthogonal Frequency Division Multiplexing (OFDM), respectively—can interfere with each other when merged.
This motivated researchers from the A*STAR Institute of Advanced Intelligence and Computing (A*STAR IAIC) to develop a system that not only combines FMCW and OFDM using the same radio-frequency hardware, but also makes them work in tandem to improve their performance. Their project was supported by the National Research Foundation, Singapore and the Infocomm Media Development Authority under its Future Communications Research and Development Programme.
“We wanted to preserve the advantages of both technologies,” said Yuhong Wang, a Senior Scientist at A*STAR IAIC. “Our system, Co-FMCW-OFDM, allows the FMCW radar and the OFDM communication signal to be transmitted simultaneously, providing a practical path towards an integrated system design that can make greater use of existing hardware.”
To reduce interference and support more effective signal processing, the team synchronised the two signals by giving them the same duration to transmit individual data symbols. They also turned off FMCW during the cyclic prefix—a short guard interval designed to mitigate interference between consecutive OFDM symbols caused by multipath propagation—as the FMCW signal was not needed during this period.
Crucially, the team also leveraged the known FMCW signal for channel estimation and interference cancellation, facilitating the decoding of the underlying OFDM signal. Rather than serving solely as a sensor, the FMCW signal served as a reference, carrying information about how the signal changes as they travel from a transmitting device to a receiving device.
“It is somewhat like recognising one of two mixed voices, reconstructing what that person said and how the environment changed the sound, and then subtracting that voice so that the second voice becomes clearer,” said Yonghong Zeng, a Senior Principal Scientist at A*STAR IAIC.
Simulations showed that Co-FMCW-OFDM achieved lower bit-error rates than conventional OFDM systems. With the FMCW signal acting as a constantly available reference, the improvements to OFDM communication were particularly noticeable when environmental conditions changed rapidly. Meanwhile, the FMCW system’s sensing capabilities were not compromised by the addition of the OFDM signal and even improved under such rapidly changing environments.
Besides vehicles, Co-FMCW-OFDM could be applied in areas such as healthcare and industrial robots, where environmental awareness and reliable wireless communication are needed. The researchers are now extending their work to more complex and realistic scenarios, hoping to develop practically implementable technologies for wireless systems.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Advanced Intelligence and Computing (A*STAR IAIC).
