Abstract
In this paper, we investigate new signal constellation pairs for mapping active subcarriers of the zero-padded trimode orthogonal frequency division multiplexing with index modulation (ZTM-OFDM-IM) systems. In the presented system, one of a constellation pair is the same as the one used in the previous work, and the other is a constellation larger than the one used in the previous work. It increases the minimum Euclidean distance between the subblocks of the ZTM-OFDM-IM system with new constellation pairs under the constraint of the same spectral efficiency. Computer simulation in AWGN and frequency-selective fading channels shows that the new ZTM-OFDM-IM system has a much lower bit error rate than OFDM-IM and dual-mode OFDM-IM and slightly outperforms the system with conventional constellation pairs. Since the proposed constellation pairs prove the error performance improvement of the system, it is considered that a further study on generalized design of the constellation pair for the ZTM-OFDM-IM system is necessary in the future.
Highlights
Due to its large capacity, high spectral efficiency, and robustness against frequency-selective fading [1], orthogonal frequency division multiplexing (OFDM), a multicarrier modulation technique, has been widely adopted in various wireless communication systems and standards such as wireless fidelity (Wi-Fi) [2], long-term evolution (LTE) [3], and world interoperability for microwave access (WiMAX) [4] for next-generation wireless communications
We introduce new constellation pairs to improve error performance of the ZTM-OFDM-index modulation (IM) system
This paper introduces new signal constellation pairs which improve the error performance of the ZTM-OFDM with IM (OFDM-IM) system
Summary
Due to its large capacity, high spectral efficiency, and robustness against frequency-selective fading [1], orthogonal frequency division multiplexing (OFDM), a multicarrier modulation technique, has been widely adopted in various wireless communication systems and standards such as wireless fidelity (Wi-Fi) [2], long-term evolution (LTE) [3], and world interoperability for microwave access (WiMAX) [4] for next-generation wireless communications. The spectral efficiency of both systems is very low compared to the conventional OFDM scheme To mitigate this problem, OFDM with IM (OFDM-IM) has been proposed to flexibly transmit IM bits by controlling the index of active subcarriers [10, 11]. To improve the spectral efficiency of the OFDM-IM system, dual-mode OFDM-IM (DM-OFDM-IM) has been proposed, where all subcarriers of a subblock are activated and mapped with two different constellations [13]. We introduce new constellation pairs to improve error performance of the ZTM-OFDM-IM system. One of the two mappers used to map active subcarriers uses the same signal constellation as the one used in the previous work, while the other uses a larger constellation than the one used in [14] This increases the minimum Euclidean distance (MED) between the subblocks of the ZTM-OFDMIM system with new constellation pairs under the constraints of the same spectral efficiency.
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