Transmitted Information Bits Research Articles

A novel differential chaos shift keying system based on joint time slot and code index of carrier phase modulation

This paper proposes a novel differential chaos shift keying (DCSK) system that utilizes carrier phase modulation in combination with time slot and code index modulation, referred to as CP-TCIM-DCSK system, to achieve high data rate transmission. In the proposed CP-TCIM-DCSK system, the carrier modulated by the carrier phase is used to transmit the information-bearing signal. In addition to physically transmitted information bits, extra information bits are conveyed through time slot and Walsh code modulation, as well as carrier phase modulation, making full use of the benefits of multidimensional modulation. To successfully estimate carrier phase bits and code index bits, an effective joint detection algorithm for carrier phase and code index tailored for the CP-TCIM-DCSK system is introduced. The theoretical Bit Error Rate (BER) expressions for the CP-TCIM-DCSK scheme are derived for both Additive White Gaussian Noise (AWGN) and multipath Rayleigh fading channels. Furthermore, a comparison of data rates, energy efficiency, and complexity between the CP-TCIM-DCSK system and the most advanced systems in the same category at present is conducted. The results validate the accuracy of theoretical analysis through simulation and demonstrate that the proposed scheme outperforms its competitive systems in terms of BER performance.

Toward Chaotic Secure Communications: An RIS Enabled M-Ary Differential Chaos Shift Keying System With Block Interleaving

Chaotic secure communication systems using chaotic waveforms as their spreading carriers can hide the transmitted information bits over a wide frequency range of chaotic waveform, which disguises the transmitted information waveform as noise. In this paper, a reconfigurable intelligent surface (RIS) enabled <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary differential chaos shift keying with block interleaving (RIS-MDCSK-BI) system is proposed for chaotic secure communications, where an RIS is deployed at the transmitter to assist communications and a pair of block interleaving patterns are used to interleave <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary information-bearing signals to enhance security performance. Moreover, we propose a chaotic merging sort algorithm to generate different block interleaving patterns, where these interleaving patterns are encrypted by using the non-periodic and noise-like properties of chaotic signals. To estimate information bits at the legitimate receiver, we propose a sequential detection algorithm and a joint detection algorithm. Then, theoretical bit error rate (BER) performances of the proposed RIS-MDCSK-BI system with the legitimate receiver and the eavesdropping receiver are derived. The security performance metrics, including information leakage and secrecy outage probability, are also analyzed. Monte Carlo simulations are performed to verify the superior BER performance and security performance of the proposed RIS-MDCSK-BI system compared to benchmark systems.

Index Modulation Multiple Access for Unsourced Random Access

In this letter, a novel index modulation multiple access (IMMA) scheme is proposed in the quasi-static MIMO channel. In the proposed scheme, the transmit information bits are divided into two parts, IMMA bits and coded bits. The IMMA bits are employed to select the active compressed sensing codeword transmitted in the first phase, and determine the IMMA pattern. The encoding bits are LDPC encoded, modulated, and transmitted in the second phase through IMMA. In the multiuser detection, the IMMA patterns and active channels are first estimated by approximate message passing (MP) algorithm. Then, the encoding bits are decoded by MP algorithm based on the joint LDPC and IMMA factor graph. Finally, computer simulations are given to demonstrate the performance of the proposed scheme.

Beam Direction-Based Modulation for Millimeter-Wave Communication Systems: Design and Optimization

In this paper, we investigate a novel beam direction-based modulation transmit scheme for millimeter-wave (mmWave) communication systems equipped with distributed antennas, and propose an enhanced space-domain index modulation (ESDIM) scheme, in which the number of beamforming directions (BDs) for transmitting information bits can be one or two. The ESDIM system jointly utilizes the combination of the index of BDs and signal constellations to transmit information bits, in which one or two beam directions are considered. In addition, we propose power allocation (PA) aided schemes for ESDIM to further improve the system reliability by reducing the system symbol error rate (SER), where three constraints to the transmit power for beamforming are investigated. To be specific, a total transmit power constraint (TTPC) and two per-beamforming power constraints (PBPC) are considered. We first propose a suboptimal PA algorithm for the TTPC-PA aided ESDIM scheme using a powerful solver based on advanced algebra theories, which only considers the PA aspects for a given selected beamforming pair. Then, we extend the TTPC-PA aided scheme to the average per-beamforming power constraint (APBPC)-PA aided scheme and the strict per-beamforming power constraint (SPBPC)-PA aided scheme. Simulation results show that the proposed schemes improve the system SER performance compared to other existing counterparts.

Communication by means of modulated Johnson noise

We present the design of a passive wireless communication method that does not rely on ambient or generated RF sources. Instead, the method modulates the Johnson (thermal) noise of a resistor to transmit information bits wirelessly. By selectively connecting or disconnecting a matched resistor to an antenna, the system can achieve data rates of up to 26 bps and distances of up to 7.3 m. This communication method operates at very low power, similar to that of an RFID tag, with the advantage of not requiring a preexisting RF signal to reflect.

Multi-User Successive-Coded Spatial Modulation Scheme Based on Beamforming

By combining an existing successive-coded spatial shift keying (SC-SSK) modulation scheme with a modulation scheme that uses the traditional constellation, we propose a new successive coded spatial modulation (SC-SM) scheme. This scheme uses spatial domain and constellation domain to jointly transmit information bits, which increases the achievable rate of the system. In order to extend the SC-SM scheme to multi-user scenario, a multi-user SC-SM (MU-SC-SM) scheme based on beamforming is proposed. The proposed MU-SC-SM scheme not only eliminates the inter-user interference (IUI) and enhances the received signal-to-noise ratio (SNR) of the served user, but also resolves the conflict between beamforming and spatial modulation. The achievable rate, the bit-error-rate (BER) performance and computational complexity of the proposed MU-SC-SM scheme are analyzed in detail. The impacts of the imperfect channel state information on the BER performance are also analyzed. Simulations are carried out to verify that the proposed MU-SC-SM scheme is superior to existing multi-user spatial modulation schemes in BER performance.

Spatial time index non‐orthogonal multiple access for beyond 5G wireless networks

AbstractMultiple input multiple output (MIMO) based non‐orthogonal multiple access (NOMA) has been an evolving technique for 5G and beyond 5G wireless networks in the last decade. The goal of the proposed technique is to achieve improved spectral efficiency, with reduced complexity in the transceiver design. A novel time‐based spatial modulation‐MIMO based NOMA (SM‐MIMO‐NOMA) known as space time index‐based NOMA (STIN) has been proposed, which brings down the number of RF chains used at the transmitter end and improves the spectral efficiency in terms of bits per channel use. In the STIN algorithm, Joint GPS enabled channel estimation and threshold rate‐based power allocation are performed for user clustering and enhancing capacity. The transmit information bits are conveyed by the active antenna index as well as amplitude phase modulation by incorporating the block user‐symbol ratio at the base station. On the receiver side, user‐timeslot‐based successive interference cancellation with a maximum likelihood detector is implemented in the user equipment. STIN improves the bits per channel use with increasing modulation order and number of users by 33%. This novel algorithm has shown better performance in comparison with the existing NOMA‐based spatial modulation techniques in terms of average bit error rate, spectral efficiency, and complexity.

Multi-carrier DCSK With Hybrid Index Modulation: A New Perspective on Frequency-Index-Aided Chaotic Communication

To realize high energy-efficient, high spectrum-efficient, and high-throughput data transmission, a multi-carrier differential chaos shift keying communication system with hybrid index modulation, referred to as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">HIM-MC-DCSK system</i> , is proposed in this paper. In the HIM-MC-DCSK system, we intelligently integrate the carrier-number-index technique and carrier-index technique into the MC-DCSK modulation in order to significantly boost the transmission efficiency in wireless communication systems. Especially, we use a pair of orthogonal signals to represent the active and inactive subcarriers in the HIM-MC-DCSK system so as to exploit all the subcarriers to transmit information bits. In addition, the theoretical bit-error-rate (BER) expressions of the HIM-MC-DCSK system are derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. Also, the data rate, spectrum efficiency, energy efficiency, and complexity of the proposed system are carefully analyzed. Monte-Carlo simulations not only verify the accuracy of the theoretical analysis but also illustrate the superiority of the proposed system.

The Achievable Rate Analysis of Generalized Quadrature Spatial Modulation and a Pair of Low-Complexity Detectors

Generalized quadrature spatial modulation (GQSM) seamlessly amalgamates the generalized spatial modulation (GSM), quadrature spatial modulation (QSM) and vertical Bell Laboratories layered space-time (V-BLAST) techniques. In contrast to traditional multiple-input multiple-output (MIMO) schemes transmitting information bits only through the constellation defined on the complex plane, GQSM transmits additional information bits implicitly by selecting the transmit antenna (TA) activation pattern. The philosophy of QSM is that of separating the indices of the real and the imaginary parts of the transmit symbols, which increases the attainable throughput. In this paper, we analyze the inherent benefits of GQSM in terms of throughput. More specifically, we first derive the achievable rate expression of the recent GQSM scheme and unveil the condition for GQSM to approach the maximum rate. Furthermore, we compare the rate of the GQSM scheme to that of other transmission schemes and reveal the conditions for the GQSM&#x2019;s maximum throughput to exceed that of the benchmark schemes. Simulation results show that when the number of TAs is 40 and quadrature phase shift keying (QPSK) is adopted, the rate of the GQSM scheme may reach 150&#x0025; of that of V-BLAST. Additionally, a pair of low-complexity detectors are conceived-one based on ordered successive interference cancellation (OSIC) and another one on the orthogonal matching pursuit (OMP) algorithm.

A Novel SR-DCSK-Based Ambient Backscatter Communication System

In order to expand the application of differential chaos shift keying (DCSK) technology in Internet of Things, a novel ambient backscatter communication system is proposed. In this system, the ambient short reference DCSK (SR-DCSK) signal is ultilized as radio frequency (RF) source, and the modulation waveform design can be easily generated by the state transition of the SR-DCSK modulation symbol according to the transmitted information bit, so as to eliminate strong direct-link interference. Furthermore, a noise reduction method based on averaging operation at the detector is designed for enhancing the bit error rate (BER) performance. Theoretical BER expression over Rayleigh fading channel is derived and validated via simulation. Moreover, the performance of the proposed system is compared with those of other DCSK-based systems.

Performance analysis of CIM‐STSK system

Code-index modulation (CIM) uses the index of spreading code to convey information, which can be integrated with different kinds of MIMO systems to achieve higher throughput. This paper proposes a novel CIM-integrated space time shift keying scheme called CIM-STSK. The CIM-STSK system employs three types of resources to transmit information bits, which are Hadamard codes, dispersion matrix indexes and QAM constellation symbols. The mathematical expression of the bit error rate of the CIM-STSK system is derived, and the theoretical analysis is validated with Monte Carlo simulation results. Compared with the corresponding CIM-SS, STSK, CIM-SM, and CIM-QSM systems, CIM-STSK scheme can not only improve spectrum efficiency, but also achieve a better error performance.

Anonymous communication scheme based on quantum walk on Cayley graph

Information security is the cornerstone and lifeblood of national security in the information society, and anonymous quantum communication is one of the important ways to protect information security. Using quantum walk randomness to effectively solve sensitive problems such as leakage of identity information. In this paper, an anonymous communication scheme based on quantum walks on the Cayley graph is proposed. First, both parties in the communication hide their identity information, and the sender Alice anonymously selects the receiver Bob through logic or operation. Secondly, the trusted third party and the communicating parties use the BB84 protocol to generate and distribute the security key. Alice encrypts the information sequence according to the security key to obtain the blind information; Bob uses the joint Bell state measurement and security key to sign and the trusted third party verifies the signature information. Third, the trusted third party calculates the position probability distribution function of Bob’s quantum walk via the Fourier transform, converts the position information corresponding to the maximum probability into a confirmation frame and sends it to Alice; Alice uses the quantum compression algorithm by decreasing dimensions to reduce the number of transmitted information bits(the length of the information bit can be reduced by up to 37.5%) and uses the security key to complete the information encryption and then transmit the information to the location indicated by the confirmation frame. Bob uses quantum walks to search the location node to obtain the transmission information and complete the anonymous quantum communication. Finally, the security analysis of the scheme is carried out, and the numerical simulation results of the Cayley graph of 200 nodes are given. At the 10-step walk, the maximal probability of the 6th node is 45.31%. According to the simulation results, the probability that Bob is eavesdropped on the specific location at his 10-step walk during the communication of this scheme is approximately 6 × 10&lt;sup&gt;–7&lt;/sup&gt;%, so the receiver can avoid the identity information from the eavesdropping with a high probability, and the quantum network anonymity protocol is not broken.

Adaptive transmit array sidelobe control using FDA-MIMO for tracking in joint radar-communications

In this paper, we present an adaptive closed–loop range-angle dependent sidelobe control using frequency diverse array (FDA) multiple-input multiple-output (MIMO) design for joint radar-communications. The system carries out tracking of the target and the communication receiver, while transmitting information bits towards the intended communication receiver using a flexible sidelobe control, i.e., controlling the power emitted at a certain angle-range position. The range-angle dependent sidelobe control utilizing an overlapped-FDA generated uncoupled beampattern with the proposed Blackman window based non-uniform frequency offsets enables the communication links to use the same radar spectrum. Moreover, we adaptively design two transmit weight vectors and finally compute a beamspace matrix that facilitates to generate the range-angle dependent beam patterns with a same radar main lobe, but distinct sidelobe levels (in accordance with the binary bit to be transmitted) for the moving target and communication receiver, respectively. Furthermore, we propose a cognitive algorithm to discriminate the target and communication receiver positions. Finally, the information bits can be efficiently detected by the intended communication receiver, merely, due to the power difference in sidelobe levels of the directed range-angle dependent radiated patterns without affecting the radar performance. The improved performance of the proposed design is verified in terms of bit error rate and inherent security for the communication functionality, while target detection, target tracking and parameter estimation are considered for the radar application.

Reliability feedback–aided low‐complexity detection in uplink massive MIMO systems

SummaryMassive multiple‐input multiple‐output (MIMO) plays a crucial role in realizing the demand for higher data rates and improved quality of service for 5G and beyond communication systems. Reliable detection of transmitted information bits from all the users is one of the challenging tasks for practical implementation of massive‐MIMO systems. The conventional linear detectors such as zero forcing (ZF) and minimum mean square error (MMSE) achieve near‐optimal bit error rate (BER) performance. However, ZF and MMSE require large dimensional matrix inversion which induces high computational complexity for symbol detection in such systems. This motivates for devising alternate low‐complexity near‐optimal detection algorithms for uplink massive‐MIMO systems. In this work, we propose an ordered sequential detection algorithm that exploits the concept of reliability feedback for achieving near‐optimal performance in uplink massive‐MIMO systems. In the proposed algorithm, symbol corresponding to each user is detected in an ordered sequence by canceling the interference from all the other users, followed by reliability feedback‐based decision. Incorporation of the sequence ordering and the reliability feedback‐based decision enhances the interference cancellation, which reduces the error propagation in sequential detection, and thus, improves the BER performance. Simulation results show that the proposed algorithm significantly outperforms recently reported massive‐MIMO detection techniques in terms of BER performance. In addition, the computational complexity of the proposed algorithm is substantially lower than that of the existing algorithms for the same BER. This indicates that the proposed algorithm exhibits a desirable trade‐off between the complexity and the performance for massive‐MIMO systems.

On The Classification of Binary Space Shift Keying Modulation

Blind and non-cooperative classification of the modulation employed in signals originating from unknown or partly known sources has widespread applications in civilian and military contexts. One of the most recent and interesting approaches to digital modulation which has been enabled by multiantenna transceivers is the spatial modulation, where the indices of the transmit antennas activated in a given symbol period are utilized to transmit information bits. Clearly, existing modulation classification methods, designed for the identification of conventional modulation types, are not capable of classifying the family of spatially modulated signals that make use of the space dimension. In this letter, for the first time in the literature, a modulation classification method is proposed for a modulation type belonging to the family of spatial modulations: the binary space shift keying modulation.

Improved spectral efficiency of SM-OFDM using a set of rotated constellations

Spatial Modulation (SM) is a technique that targets to achieve a compromise between the two conflicting objectives in multiple-input multiple-output (MIMO) networks, namely the simultaneous enhancements of data reliability and data rate, by adjusting the index of the operational transmit antenna in the transmitted information bits. Orthogonal frequency division multiplexing (OFDM) has become a widely accepted technique to combat inter-symbol interference (ISI) present in frequency selective channels, such as the ones conveying very high data rates. In this paper, a new SM-OFDM-based scheme is proposed, which adds another element of information in the transmitted SM-data block consisting of a chosen constellation among the available rotated set. To attain this, an additional index is used to select the specific constellation. At the receiver, a set of detectors is proposed to jointly estimate the transmitted symbol, as well as the used constellation and the active transmit antenna indices. The comparison of the performance of this new scheme against the conventional SM-OFDM shows an increased spectral efficiency at the price of a slight degradation in bit error rate. The proposed scheme permits a trade-off between the quality of the communication and the achieved spectral efficiency.

Transmit Signal Designs for Spatial Modulation With Analog Phase Shifters

In this paper, we study transmit codebook designs for spatial modulation with analog phase shifters. The proposed spatial modulation with analog phase shifters can send more spatial symbols than conventional spatial modulation, while reserving the low complexity of single RF-chain MIMO structure. The main idea is to transmit $N_{t}$ different phase-shifted copies of a digitally modulated signal through $N_{t}$ transmit antennas. In each time slot, the transmitted information bits are divided into two groups. The first group of the bits is mapped to the digitally modulated signal symbol. The second group of the bits is mapped to the spatial symbol, which determines the phase shift of each antenna. The transmit signal designs are carried out in open loop and closed loop scenarios, respectively. In open loop scenario, the transmit codebook is designed in two steps, i.e., generate the optimal spatial codebook according to Grassmannian line packing criterion, and find the optimal tradeoff between the cardinality of spatial codebook and the modulation order of signal symbol. In the closed loop scenario, the transmit codebook is designed according to the structure of Huffman tree. Extensive simulation results are given to validate the effectiveness of the proposed scheme in open loop scenario and close loop scenario, respectively.

Space shift keying for multi-hop multi-branch networks

In this paper, we propose two different multi-hop multiple-input multiple-output (MIMO) space shift keying (SSK) schemes and investigate their error performance. In the first scheme, we consider a multi-hop multi-branch SSK system, in which the source and destination are equipped with multiple transmit and receive antennas, respectively. In this scheme, SSK is applied by using the source transmit antennas. Moreover, in each branch, single-antenna relays are used to amplify the transmitted signal from the source and forward it to the next relay until it reaches to the destination. In the second scheme, we consider a multi-hop MIMO-SSK system with path selection. In this scheme, the best path is selected among multiple branches and a multiple-antenna source communicates with a multiple-antenna destination via the relays of the selected path. Each relay is equipped with multiple transmit and receive antennas. Moreover, the source and all relays employ SSK modulation to transmit information bits and each relay in each path follows the decode-and-forward protocol. Approximate theoretical error probability expressions are derived for both schemes. Furthermore, an asymptotic symbol error probability performance analysis is also performed for the multi-hop MIMO-SSK system with path selection. It is shown that the proposed multi-hop SSK systems outperform conventional multi-hop M-PSK systems in terms of the error performance for especially high data rates and sufficient number of receive antennas at the receiving nodes.

Spatial Modulation via 3-D Mapping

This letter proposes a jointly mapped spatial modulation (JM-SM) scheme to break through the constraint on the number of transmit antennas in traditional SM systems. It is realized via jointly mapping the transmit information bits to 3-D constellation points. A 3-D constellation design scheme for a JM-SM is analyzed and established by minimizing the system average bit error probability (ABEP). In addition, the extension of the joint 3-D mapping to generalized spatial modulation is discussed. The simulation results show that the proposed schemes can be adapted to multiple-input multiple-output systems with an arbitrary number of transmit antennas and offer better ABEP performance than those existing schemes.

Layered Space Shift Keying Modulation over MIMO Channels

Space shift keying (SSK) modulation is an emerging transmission technique for multiple-input multiple-output (MIMO) wireless channels, which exploits the spatial domain to convey information. In this paper, we present a layered space shift keying (LSSK) modulation scheme to fully exploit the spatial domain to transmit information bits, where a layered architecture is developed to achieve spatial multiplexing transmission in an SSK system. Specifically, LSSK leverages the rotated signals predetermined at the transceiver to identify different layers and improve the bit-error-rate (BER) performance. The layered signals are directly generated by the proposed LSSK modulation method with a low computational overhead. Furthermore, we propose a layered-and-joint (LJ) near-optimal detection algorithm based on the layered architecture of LSSK to reduce the detection complexity. In LJ detection, layered detection is performed to find a set of detection candidates for each layer, and then, joint detection is performed with these candidates. We show that the performance of LJ detection is quite close to that of optimal maximum-likelihood detection with significantly reduced detection complexity for high-spectrum-efficiency scenarios. Results demonstrate that the proposed LSSK scheme substantially improves the spectrum efficiency of an SSK system and outperforms other existing MIMO schemes.