Index Modulation Assisted DCT-OFDM with Enhanced Transceiver Design

An index modulation (IM) assisted Discrete Cosine Transform based Orthogonal Frequency Division Multiplexing (DCT-OFDM) with Enhanced Transmitter Design (termed as EDCT-OFDM-IM) is proposed. It amalgamates the concept of Discrete Cosine Transform assisted Orthogonal Frequency Division Multiplexing (DCT-OFDM) and Index Modulation (IM) to exploit the design freedom provided by the double number of available subcarrier under the same bandwidth. In the proposed EDCT-OFDM-IM scheme, the maximum likelihood (ML) detector used for symbol bits and index bits recovering is derived and the sophisticated designing guidelines for EDCT-OFDM-IM are provided. Based on the derived pairwise error event probability, a theoretical upper bound on the average bit-error probability (ABEP) of EDCT-OFDM-IM is provided over multipath fading channels. Furthermore, the maximum peak-to-average power ratio (PAPR) of our proposed EDCT-OFDM-IM scheme is derived and compared to than the general Discrete Fourier Transform (DFT) based OFDM-IM counterpart

Enhanced DCT-OFDM system with index modulation

Discrete cosine transform (DCT) based orthogonal frequency division multiplexing (OFDM), which has double number of subcarrier compared to the classic discrete fourier transform (DFT) based OFDM (DFT-OFDM) at the same bandwidth, is a promising high spectral efficiency multicarrier techniques for future wireless communication. In this paper, an enhanced DCT-OFDM with index modulation (IM) (EDCT-OFDM-IM) is proposed to further exploit the benefits of the DCT-OFDM and IM techniques. To be more specific, a pre-filtering method based DCT-OFDM-IM transmitter is first designed and the non-linear maximum likelihood (ML) is developed for our EDCT-OFDM-IM system. Moreover, the average bit error probability (ABEP) of the proposed EDCT-OFDM-IM system is derived, which is confirmed by our simulation results. Both simulation and theoretical results are shown that the proposed EDCT-OFDM-IM system exhibits better bit error rate (BER) performance over the conventional DFT-OFDM-IM and DCT-OFDM-IM counterparts

Maximum likelihood based estimation of frequency and phase offset in DCT OFDM systems under non-circular transmissions: algorithms, analysis and comparisons

Recently, the advantages of the discrete cosine transform (DCT) based orthogonal frequency-division multiplexing (OFDM) have come to the light. We thus consider DCT- OFDM with non-circular transmission (our results cover circular transmission as well) and present two blind joint maximum- likelihood frequency offset and phase offset estimators. Both our theoretical analysis and numerical comparisons reveal new advantages of DCT-OFDM over the traditional discrete Fourier transform (DFT) based OFDM. These advantages, as well as those already uncovered in the early works on DCT-OFDM, support the belief that DCT-OFDM is a promising multi-carrier modulation scheme

Efficient DCT-MCM Detection for Single and Multi-Antenna Wireless Systems

The discrete cosine transform (DCT) based multicarrier modulation (MCM) system is regarded as one of the promising transmission techniques for future wireless communications. By employing cosine basis as orthogonal functions for multiplexing each real-valued symbol with symbol period of T, it is able to maintain the subcarrier orthogonality while reducing frequency spacing to 1/(2T) Hz, which is only half of that compared to discrete Fourier transform (DFT) based multicarrier systems. In this paper, following one of the effective transmission models by which zeros are inserted as guard sequence and the DCT operation at the receiver is replaced by DFT of double length, we reformulate and evaluate three classic detection methods by appropriately processing the post-DFT signals both for single antenna and multiple-input multiple-output (MIMO) DCT-MCM systems. In all cases, we show that with our reformulated detection approaches, DCT-MCM schemes can outperform, in terms of error-rate, conventional OFDM-based systems

Performance analysis and optimization of DCT-based multicarrier system on frequency-selective fading channels

Regarded as one of the most promising transmission techniques for future wireless communications, the discrete cosine transform (DCT) based multicarrier modulation (MCM) system employs cosine basis as orthogonal functions for real-modulated symbols multiplexing, by which the minimum orthogonal frequency spacing can be reduced by half compared to discrete Fourier transform (DFT) based one. With a time-reversed pre-filter employed at the front of the receiver, interference-free one-tap equalization is achievable for the DCT-based systems. However, due to the correlated pre-filtering operation in time domain, the signal-to-noise ratio (SNR) is enhanced as a result at the output. This leads to reformulated detection criterion to compensate for such filtering effect, rendering minimum-mean-square-error (MMSE) and maximum likelihood (ML) detections applicable to the DCT-based multicarrier system. In this paper, following on the pre-filtering based DCT-MCM model that build in the literature work, we extend the overall system by considering both transceiver perfections and imperfections, where frequency offset, time offset and insufficient guard sequence are included. In the presence of those imperfection errors, the DCT-MCM systems are analysed in terms of desired signal power, inter-carrier interference (ICI) and inter-symbol interference (ISI). Thereafter, new detection algorithms based on zero forcing (ZF) iterative results are proposed to mitigate the imperfection effect. Numerical results show that the theoretical analysis match the simulation results, and the proposed iterative detection algorithms are able to improve the overall system performance significantly

A selective control information detection scheme for OFDM receivers

In wireless communications, both control information and payload (user-data) are concurrently transmitted and required to be successfully recovered. This paper focuses on block-level detection, which is applicable for detecting transmitted control information, particularly when this information is selected or chosen from a finite set of information that are known at both transmitting and receiving devices. Using an orthogonal frequency division multiplexing architecture, this paper investigates and evaluates the performance of a time-domain decision criterion in comparison with a form of Maximum Likelihood (ML) estimation method. Unlike the ML method, the proposed time-domain detection technique requires no channel estimation as it uses the correlation (in the time-domain) that exists between the received and the transmitted selective information as a means of detection. In comparison with the ML method, results show that the proposed method offers improved detection performance, particularly when the control information consists of at least 16. However, the implementation of the proposed method requires a slightly increased number of mathematical computations

Constant Envelope DCT- and FFT- based Multicarrier Systems

Discrete Cosine Transform (DCT)- and Fast Fourier Transform (FFT)- based Orthogonal Frequency Division Multiplexing (OFDM) systems with a variety of angle modulations are considered for data transmission. These modulations are used with the purpose of achieving Constant Envelope (CE) transmitted signals, for superior power efficiency with nonlinear High Power Amplifier (HPA), typically used at the transmitter in OFDM systems. Specifically, four angle modulations are considered: i) Phase Modulation (PM); ii) Frequency Modulation (FM); iii) Continuous Phase Modulation (CPM); and iv) Continuous Phase Chirp Modulation (CPCM). Descriptions of DCT- and FFT- based OFDM systems with M-ary Pulse Amplitude Modulation (MPAM) mapper, with these modulations, are given and expressions for transmitted signals are developed. The detection of these signals in Additive White Gaussian Noise (AWGN) and multipath fading channels is addressed. The receiver structure consists of arctangent demodulator followed by the optimum OFDM receiver for memoryless PM and FM modulations. However, for CPM and CPCM modulations that have inherent memory, arctangent demodulator followed by correction with oversampling technique is used prior to the optimum OFDM receiver. Closed-form expressions for Bit Error Rate (BER) have been derived and are function of: i) Signal-to-Noise Ratio, (Eb/N0); ii) Modulation parameters; iii) Number of amplitude levels of M-PAM mapper; and iv) parameters of multipath fading environment. It is shown that, in general, BER performance of CE-DCT-OFDM system is superior compared to that of conventional DCT-OFDM system, when the effect of HPA in the system is taken into account. Also, it is observed that CE-DCT-OFDM system outperforms CE-FFT-OFDM system by nearly 3 dB. The DCT- and FFT- OFDM systems with CPM and CPCM modulations are superior in BER performance compared to PM and FM modulations in these systems. The use of CPCM in OFDM systems can provide attractive trade off between bandwidth and BER performance. The performance of CE-DCT-OFDM and CE-FFT-OFDM systems over Rayleigh and Rician frequency non-selective slowly-varying fading channels are illustrated as a function of channel parameters and the penalty in SNR that must be paid as consequence of the fading is determined