We propose a new index-modulation-aided differential chaos shift keying (DCSK) system using frequency-and-time resources, referred to as CTIM-DCSK system, to achieve highdata-rate transmissions. In the proposed system, the orthogonal sinusoidal carriers are used to transmit both the reference-chaotic and the information-bearing signals. Moreover, the frequencyand-time resources are considered as indices to carry additional information bits. To simultaneously boost the bit error rate (BER) performance and reduce the system complexity, this paper proposes a new CTIM-DCSK signal based on the frequencyand-time resources, in which the time slots used by the selected subcarriers convey the same index bits. We employ a noisereduction method at the receiver to further improve the BER performance of the proposed CTIM-DCSK system. We also derive the theoretical BER expressions of the CTIM-DCSK system over two different channels, i.e., additive white Gaussian noise (AWGN) channel and multipath Rayleigh fading channel. We analyze the data rate, complexity and spectral efficiency of the CTIM-DCSK system in comparison with the state-ofthe-art counterparts. Analytical and simulation results verify the accuracy of the theoretical analysis and the advantage of the proposed CTIM-DCSK system. Consequently, the proposed CTIM-DCSK system appears to be a competitive candidate for low-complexity Internet-of-Things applications.Index Terms-Frequency-and-time index, differential chaos shift keying (DCSK), multipath Rayleigh fading channel, noise reduction. I. INTRODUCTIONChaotic signal has been widely used in spread-spectrum communication systems, because of its easy generation and excellent auto-correlation properties [1], [2]. In the past few decades, chaotic communication has gained widespread attention from academia and industry. It has been proven to be one of the best candidates for wireless communications, e.g.,

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