Additional Information Bits Research Articles

Ultrasonic Indexed Modulation and Multiple Access for Intra-Body Networks

Intra-body communication (IBC) plays a significant role in future health care systems. This article proposes a pulse-based ultrasonic index modulation (UsIM) to enable high data rate and low power IBCs. Two grouping-based UsIM strategies, namely ultrasonic grouped-chip indexed modulation (UsCIM) and ultrasonic chip-group indexed modulation (UsGIM), are proposed to implement multiple access for intra-body networks (IBNs). UsCIM uses the chip indices in a group to convey additional information bits for a biosensor node, while UsGIM uses the group indices and each node occupies one chip in a group. Three receivers, including the maximum likelihood (ML), the maximum ratio combination (MRC), and the energy detection (ED) receivers, are then proposed and studied. The theoretical bit-error rate (BER) upper bound for the ML receiver, and theoretical BER expressions for the MRC and ED receivers are derived. The system performance metrics in terms of complexity, throughput and energy efficiency are analyzed. The analytical and simulation results reveal that UsGIM achieves a lower BER than UsCIM under channel fading and multipath effect. Both UsCIM and UsGIM achieve higher throughput and energy efficiency than the existing IBC systems, and both strategies are important for energy-constrained implanted IBNs.

C‐MRC–based cooperative spatial modulation with antenna selection

SummaryA new high‐performance low‐complexity cooperative maximal ratio combining (C‐MRC)‐based cooperative relaying scheme, which is called antenna selection‐aided cooperative spatial modulation scheme with C‐MRC (AS‐CSM), is proposed for decode and forward (DF)‐based cooperative relaying networks operating over independent but non‐identically distributed (i.n.d.) Rayleigh fading channels. The AS‐CSM scheme is formed with the combination of cooperative SM with the high‐performance low‐complexity coherent demodulator C‐MRC and antenna selection techniques. In the AS‐CSM scheme, the information is transmitted from the source terminal (ST) to the relay terminal (RT) and the destination terminal (DT) in the form of not only modulated symbols but also antenna indices, which carry additional information bits in the spatial domain. Therefore, a high spectral efficiency is obtained by the proposed scheme for cooperative relaying networks. In this scheme, first, the index of the activated antenna of ST is estimated, and the best antenna selection at RT is investigated considering the received instantaneous equivalent to signal‐to‐noise values acquired at DT. The transmitted symbols are estimated with low‐complexity coherent demodulator C‐MRC at DT by using the noisy signals from ST and RT. An exact closed‐form expression for the bit error probability (BEP) of the AS‐CSM scheme is derived, and the theoretical results are validated with Monte‐Carlo simulation results.

Space-Time Mapping for Equiprobable Antenna Activation in Spatial Modulation

Spatial modulation (SM) conveys additional information bits via the index of an activated transmit antenna. When the number of antennas is not an integer power of two, the antenna activation becomes challenging. In such a case, only a subset of the available transmit antennas whose cardinality is an integer power of two is used. This leads to antenna activation with unequal probability, which causes high error rates and losses in the spectral efficiency. The same limitations and performance losses equally exist in quadrature spatial modulation (QSM) and generalized spatial modulation (GSM), the two prominent variants of SM. In this contribution, in contrast to the conventional approach of antenna activation within each symbol period, a space-time bit-mapping method in which the antenna selection procedure is extended to multiple symbol periods is proposed. Use of the proposed method in SM, QSM, and GSM techniques, is shown to achieve performances close to their full potential for any given number of transmit antennas, with only a marginal increment in detection complexity.

Sparse-Encoded Codebook Index Modulation

Ultra-reliable and low-latency communications (URLLC) partakes a major role in 5 G networks for mission-critical applications. Sparse vector coding (SVC) appears as a strong candidate for future URLLC networks by enabling superior performance in terms of bit error rate (BER). SVC exploits the virtual digital domain (VDD) and compressed sensing (CS) algorithms to encode and decode its information through active symbol indices. In this paper, first, a clever encoding/decoding algorithm is proposed for the SVC scheme, which allows the use of all possible activation patterns (APs) resulting in increasing spectral efficiency. Second, a novel solution is proposed to convey additional information bits by further exploiting index modulation (IM) for the codebooks of the SVC scheme. Computer simulation results reveal that our low-complexity algorithm and novel IM solution provide not only a superior BER performance but also an increase in the number of bits conveyed by IM compared to the ordinary SVC approach.

Space-Frequency Increment Index Modulation Approach for Fifth Generation and Beyond Wireless Communication Systems

Unlike the classical modulation, for instance, quadrature amplitude modulation (QAM) and others, where bits are transmitted via symbols particularly from modulation alphabets, in index modulation (IM), extra information bits can be conveyed via the indices of a particular transmit entities during the transmission process. Transmit antenna elements are example of transmit entities in multi-antenna systems which can be used to convey extra information bits. Recently, frequency diverse array (FDA), as a new type of transmit antenna array which differs from the traditional phased-array has been proposed in the literature. In FDA, the element indices has small frequency increment across them. In this paper, space-frequency increment IM is proposed. The proposed scheme utilizes the indices of the activated transmit FDA antennas and their respective corresponding frequency increments $\Delta f$ to convey additional information bits. The proposed scheme is inspired by the principle of quadrature spatial modulation (QSM) and no additional antenna activation is required. Compared with spatial modulation (SM) and QSM, it is shown that, the proposed scheme achieved higher spectral efficiency. Further, the average bit error rate (ABER), secrecy sum rate (SSR) and system capacity are derived and evaluated. Moreover, a low-complexity decoding algorithm is examined. Finally, via numerical results, the proposed scheme shows to be better than the comparative alternatives (QSM/SM), and may offer promising properties in various contexts.

Secure Single-Input-Multiple-Output Media-Based Modulation

The media-based modulation (MBM) system, which varies its channel state by controlling the on/off status of the radio frequency (RF) mirrors, and embeds additional information bits into the mirror activation pattern, is capable of achieving significant throughput and desirable bit-error-rate (BER) performance. Hence, it has attracted increasing attention from researchers of wireless communication community. In this paper <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> , the information secrecy issue for MBM is investigated, and a secure single-input-multiple-output MBM (SIMO-MBM) system is proposed utilizing physical-layer security techniques. By considering the time-division duplexing (TDD) mode with channel reciprocity property, the legitimate channel state information (CSI) is applied to secure the data transmission of SIMO-MBM. More specifically, on one hand, adaptive phase rotation is imposed on the transmitted signals, where the rotation angle is determined by the phase of legitimate CSI; on the other hand, the mapping rule between the mirror activation pattern and binary bits is changed according to the amplitude of legitimate CSI. The BER performance of the eavesdropper is investigated via theoretical derivations, and the system secrecy mutual information is also derived, based on which the optimal design of the adaptive phase rotation strategy is provided. Theoretical and simulative results demonstrate that the proposed secure SIMO-MBM system is capable of enhancing the data confidentiality whilst keeping reliable data transmission.

Precoding-Aided Spatial Modulation With Dual-Polarized Antennas Over Correlated Channels

In this letter, we propose a dual-polarized precoding-aided spatial modulation (DPPSM) scheme, which introduces the polarization dimension into conventional precoding-aided spatial modulation (PSM) to transmit an additional information bit, avoiding the occupation of additional physical space while offering extra transmit diversity. We obtain an upper bound on the average bit error probability (ABEP) of the proposed DPPSM scheme over correlated fading channels. We also derive an approximate upper bound on the ABEP to show the diversity order. Simulation results show that the upper bound is tight for a high signal-to-noise ratio (SNR) range, and the bit error rate (BER) performance of the proposed DPPSM scheme is better than that of the conventional PSM scheme at the same spectral efficiency when equipped with an equal amount of antennas. Furthermore, the proposed DPPSM scheme is more robust to Gaussian channel error when the channel estimation imperfection is considered.

Cognitive Radio Network Assisted by OFDM With Index Modulation

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) transmits additional information bits through the indices of active subcarriers. In this paper, we explore the potential of an improvement of OFDM-IM by reusing inactive subcarriers to transmit signals for a secondary system. We consider a cognitive radio network assisted by OFDM-IM, where the primary user (PU) transmits its signal to the primary receiver, and the secondary user (SU) senses the idle spectrum and transmits its own signal to the secondary receiver via those idle subcarriers. By either combining the signal transmitted from SU or not, we propose two different detection strategies with different trade-offs between the computational complexity and system performance. An asymptotically tight upper bound on the bit error rate is derived to evaluate the error performance.

OFDM With Hybrid Number and Index Modulation

A novel transmission scheme is introduced for efficient data transmission by conveying additional information bits through jointly changing the index and number of active subcarriers within each orthogonal frequency division multiplexing (OFDM) subblock. The proposed scheme is different from the conventional OFDM-subcarrier number modulation (OFDM-SNM) and OFDM-index modulation (OFDM-IM), in which data bits are transmitted using either number or index of active subcarriers. The proposed modulation technique offers superior spectral and energy efficiency compared to its counterparts OFDM-SNM and OFDM-IM, especially at low modulation orders such as binary phase shift keying (BPSK) that can provide high reliability and low complexity, making it suitable for Internet of Things (IoT) applications that require better spectral and energy efficiency while enjoying high reliability and low complexity. Bit error rate (BER) performance analysis is provided for the proposed scheme, and Monte Carlo simulations are presented to prove the consistency of simulated BER with the analyzed one.

Multi-Carrier $M$-ary DCSK System With Code Index Modulation: An Efficient Solution for Chaotic Communications

A new multi-carrier $M$ -ary differential chaos shift keying system with code index modulation, referred to as CIM-MC- $M$ -DCSK , is proposed in this paper. In the proposed CIM-MC- $M$ -DCSK system, the reference and information-bearing signals for each subcarrier can be transmitted simultaneously by using the orthogonal sinusoidal carriers, where the information-bearing signal adopts the $M$ -DCSK modulation to further increase the data rate. With an aim to making full use of the system energy resources, the reference signals in all subcarriers are coded by a Walsh code to carry additional information bits. The analytical bit-error-rate (BER) expressions of the proposed CIM-MC- $M$ -DCSK system are derived over additive white Gaussian noise as well as multipath Rayleigh fading channels. Furthermore, a noise-reduction scheme and a hierarchical-modulation scheme are designed for the proposed system. In particular, the former scheme can significantly improve the BER performance while the latter scheme can provide different quality of service for the transmitted bits according to their different levels of importance. Simulation results verify the accuracy of the analytical expressions and the superiority of the proposed systems.

Permutation index-quadrature spatial modulation: A spectral efficient spatial modulation for next generation networks

Spatial Modulation techniques (SMTs) offer an exceptional trade-off between spectral and energy efficiencies. In this work, we propose a new SMT termed as permutation index-quadrature spatial modulation (PI-QSM), aiming for enhanced spectral efficiency and better average bit error rate (ABER) performance compared to rival SMTs. To enhance spectral efficiency, PI-QSM exploits permutations of active transmit antennas by conveying additional information bits innovatively through indices of active antenna permutations. PI-QSM also alleviates the major constraint in some of the SMTs, where the total number of transmit antennas need to be a power of two. At any time instance, PI-QSM transmits real and imaginary parts of two complex modulated symbols separately using four different active antennas. To avoid any ambiguities at the receiver and to improve the error performance of the overall system, a rotation angle is introduced between the two modulated symbols before transmission. The rotation angle is optimized for different M-quadrature amplitude modulation (QAM) constellations using extensive Monte Carlo simulations. Performance of PI-QSM scheme is analyzed by deriving closed-form expressions for upper bound and asymptotic average bit error probability (ABEP) over Rayleigh fading channels. The Simulation results substantiate the accuracy of analytical analysis and also indicate that the proposed PI-QSM scheme offers better ABER performance than rival SMTs such as QSM and generalized QSM (GQSM).

Enhanced Subband Index Carrierless Amplitude and Phase Modulation in Visible Light Communications

An enhanced subband index carrierless amplitude and phase modulation (eSI-CAP) scheme is developed to improve the spectral efficiency of the multiband CAP ( $m$ -CAP) in visible light communication (VLC) systems. Using indexing technique and a dual distinguishable constellations, the eSI-CAP carries information bits by modulating symbols on the subbands of $m$ -CAP. It also encodes additional information bits on the selection of the subband indices that is modulated with the dual constellation symbols. The performance advantage of eSI-CAP is demonstrated through theoretical analysis, computer simulations and VLC experimental validations. In addition, a novel maximum likelihood detector is developed for eSI-CAP with the same order of complexity as the conventional $m$ -CAP detector. On comparison with $m$ -CAP, eSI-CAP requires lower signal-to-noise ratio (SNR) per bit ( $\gamma _b$ ) to reach a fixed data rate ( $R_\text{b}$ ). Alternatively, when the $\gamma _b$ is fixed, it achieves a higher $R_\text{b}$ for a target BER. The results show that eSI-CAP is very attractive for VLC systems due to its flexible configuration and its improvement of the power efficiency of the conventional $m$ -CAP modulation scheme.

Constellation Design for Quadrature Spatial Modulation

Quadrature space modulation (QSM) was proposed recently as a viable multiple-input multiple-output (MIMO) communication technique for next generation wireless system. QSM achieves the more spatial gain than spatial modulation (SM) due to transmitting more additional information bits by the freedom of transmit antennas. In this paper, without increasing the complexity of detection at the receiver, an improved M-ary quadrature amplititude modulation (I-MQAM) signal constellation for the QSM system is proposed to further increasd the squared Minimum Euclidean distance (MED) between the transmitted spatial vectors (TSVs). Then an upper bound on the average bit error probability (ABEP) is elaborately analyzed. Simulation results using Monte Carlo demonstrate that the QSM system with the proposed I-MQAM has better bit error ratio (BER) performance than the QSM system with M-QAM/PSK in wireless network.

Selective Mapping Technique Based on an Adaptive Phase-Generation Mechanism to Reduce Peak-to-Average Power Ratio in Orthogonal Frequency Division Multiplexing Systems

This paper aimed to investigate how to construct a phase-generation mechanism with a systematic structure and without diminishing the peak-to-average power ratio (PAPR) reduction performance of a conventional selective mapping (SLM) technique. The SLM is a prevalent technique for reducing the PAPR and is often applied in orthogonal frequency division multiplexing (OFDM) systems. Despite effectively reducing the PAPR, the SLM generates phase sequences randomly, creating a lack of systematic structure and increased system complexity. Therefore, this paper sets an adaptive threshold value to evaluate the characteristics of input signals. On the basis of the evaluated characteristics, this paper selected the optimal phase-generation mechanism to produce phase sequences. In the proposed method, the phase-generation mechanism was established according to the structure of Reed–Muller codes, thereby achieving a systematic structure that the random generation technique lacks. Compared with the conventional SLM techniques, the proposed method required an additional bit of side information for each transmitted signal but could approximate the PAPR reduction performance of the conventional SLM technique according to the simulation results.

Experimental Demonstration of Subband Index Techniques for &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$m$ &lt;/tex-math&gt; &lt;/inline-formula&gt;-CAP in Short-Range SI-POF Links

In this letter, novel spectrally efficient subband index (SI) techniques have been developed for multiband carrierless amplitude and phase modulation ( $m$ -CAP). The SI techniques transmit additional information bit on the index of the conventional $m$ -CAP subbands. Experimental demonstrations are performed in a short-range optical data link using step-index plastic optical fiber. The demonstrations show that the proposed techniques enable flexibility in design and significantly improve the power/spectral efficiency of the conventional $m$ -CAP.

Joint channel estimation and turbo equalisation for MIMO-OFDM-IM systems

ABSTRACTMultiple-Input Multiple-Output (MIMO) communications are frequently employed to improve the transmitted data rate and the link quality. Index modulated orthogonal frequency division multiplexing (OFDM-IM) improves the error rate performance and the peak-to-average power ratio (PAPR) compared with those of the conventional OFDM system due to the activation of partial subcarriers. The MIMO OFDM-IM can transmit additional information bits via the indices of active subcarriers. Also, in order to reduce the transmission power of the OFDM system, the MIMO OFDM-IM scheme can be employed to approach the demanded data transmission rate and the error rate performance. Multiple-input multiple-output orthogonal frequency division multiplexing index modulation (MIMO-OFDM-IM) is an effective multicarrier transmission scheme and can be proposed as an alternative to conventional MIMO-OFDM system. In this scheme, OFDM-IM is combined with MIMO transmission to take the benefits of these two techniques. In this paper, we propose a joint channel estimation and turbo equalisation receiver for MIMO-OFDM-IM system. Some simulation examples are given to demonstrate the effectiveness of the proposed receiver.

A Multilevel Code Shifted Differential Chaos Shift Keying Scheme With Code Index Modulation

In this brief, a code index modulated multilevel code shifted differential chaos shift keying, which combines multilevel code shifted differential chaos shift keying (MCS-DCSK) with code index modulation, is proposed. In the proposed scheme, the reference chaos signal is the same with MCS-DCSK, and the multiple information bearing signals are simultaneously modulated by information symbols and selected Walsh codes with specified indices which are determined by additional information bits via the natural number to k-combination mapping method. The proposed scheme achieves higher spectrum efficiency compared to MCS-DCSK since additional bits are carried by code indexes. The analytical bit error rate of the proposed system is derived and confirmed by simulation. Finally, advantages of the proposed scheme over MCS-DCSK are verified by numerical results.

A unified performance analysis of decode‐and‐forward dual‐hop relaying‐based wireless energy harvesting with space modulation

AbstractSpace modulation techniques (SMTs) are a group of multiple‐input–multiple‐output wireless systems in which the spatial indexes of transmit antennas are utilized to convey additional information bits. The SMTs promise significant enhancements in terms of spectral and energy efficiencies and attract significant research interest in literature. Several SMTs have been proposed including spatial modulation (SM) and quadrature SM. In this study, the performance of dual‐hop decode‐and‐forward relaying SM and quadrature SM in the presence of wireless power transfer is analyzed and thoroughly discussed. Specifically, we derive exact closed‐form expressions for the pairwise error probability (PEP). In addition, we derive simple and accurate asymptotic expressions for the PEP at high signal‐to‐noise ratio, which provides insight into the influence of different system parameters. The obtained PEP expressions are then employed to evaluate the overall average bit error rate (BER). It is worth highlighting that the derived expressions are unified in the sense that they are valid for the aforementioned SMTs and for two well‐known practical energy harvesting protocols, namely, power‐splitting receiver and time‐switching receiver. In addition, we derive a unified closed‐form expressions for the outage probability and achievable throughput at the destination node. The impact of diverse system parameters, such as the power‐splitting factor, the energy‐harvesting time factor, and the distance between the source and the relay nodes, on the overall system performance is studied. The accuracy of the analytical derivations is validated through Monte Carlo simulations results.

IEEE Access Special Section Editorial: Index Modulation Techniques for Next-Generation Wireless Networks

Index modulation (IM) techniques appear as competitive candidates for next-generation (5G and beyond) wireless networks due to the attractive advantages they offer in terms of spectral and energy efficiency as well as hardware simplicity. IM is a highly spectrum- and energy-efficient yet simple digital modulation technique, which utilizes the indices of the building blocks of the corresponding communication systems to convey additional information bits. IM systems provide alternative ways to transmit information in contrast to traditional digital modulation schemes that rely on the modulation of the amplitude/phase/frequency of a sinusoidal carrier signal for transmission, as widely considered in the field of communications over the past 50 years. Radically, IM schemes have the ability to map information bits by altering the on/off status of their transmission entities such as transmit antennas, subcarriers, radio frequency (RF) mirrors, transmit light emitting diodes, relays, modulation types, time slots, precoder matrices, dispersion matrices, spreading codes, signal powers, loads and so on. In other words, IM creates completely new dimensions for data transmission. Since the initial skepticism of both academia and industry on the potential and applicability of IM technologies has now gone away, we strongly believe that IM is not another simple digital modulation alternative, but rather can be a game-changing communication paradigm whose time has come!

Quadrature Channel Modulation

In this letter, we propose the concept of quadrature channel modulation (QCM) by combining quadrature spatial modulation (QSM) and media-based modulation (MBM) transmission principles. The proposed QCM schemes exploit not only the in-phase and quadrature components of complex data symbols for antenna indexing but also channel states for the transmission of additional information bits through index modulation by employing a single radio frequency (RF) chain. It is shown via numerical studies that the proposed QCM schemes can outperform the existing emerging schemes such as QSM, plain MBM, and spatial modulation-based MBM, which also employ a single RF chain at their transmitters.