Multiple-input Multiple-output Code Research Articles

Multidomain Narrowband Interference Intelligent Suppression Method Based on Cognitive Radio and MIMO in UAV Data Link.

In this paper, a kind of antinarrowband interference intelligent method based on cognitive MIMO (multiple-input multiple-output) airspace, time domain, frequency domain, and code domain is proposed. This method combines perceptual technology, spread spectrum code, MIMO space-time coding, and so on. Through coordinating space, time, frequency, and code element diversity, the narrowband interference in the UAV (unmanned aerial vehicle) monitoring and control link is effectively countered. The input and output model of MIMO monitoring and control link of UAV with natural interference are described. Then, the realization principle of the multidomain antinarrowband interference method based on CR-MIMO is presented, and the corresponding models of receiving and transmitting are also given. Finally, the anti-interference performance of the proposed method is analyzed theoretically and validated through simulation experiments, and the effectiveness of the proposed method is verified.

Performance Comparison of Repetition Coding MIMO Optical Wireless Communications with Distinct Light Beams.

In current optical wireless communications (OWC) oriented research works, the various multiple input multiple output (MIMO) techniques are introduced and utilized to enhance the coverage performance. Objectively, this Lambertian light beam based MIMO research paradigm neglects the light beam diversity and the potential performance gains. In this work, the distinct non-Lambertian light beams of commercially available light emitting diodes (LEDs) were adopted to configure MIMO OWC links. Specifically, the homogenous and heterogeneous non-Lambertian MIMO configurations were constituted in typical indoor scenarios. Moreover, applying the repetition coding (RC) MIMO algorithm with low complexity, a spatial coverage performance comparison was made between the several above mentioned non-Lambertian configurations and the well-discussed Lambertian MIMO configuration. Numerical results illustrate that the homogeneous NSPW light beam configuration could provide a more than 30 dB average signal to noise ratio (SNR), while the achievable average SNR of the heterogeneous light beam configuration was up to 28.77 dB. On the other side, the counterpart of the Lambertian configuration achieved just about 27.00 dB. Objectively, this work paves the fundamental and essential way for the further design and optimization of MIMO OWC in this novel light beam dimension.

Gallager Exponent Analysis of Coherent MIMO FSO Systems over Gamma-Gamma Turbulence Channels.

This paper studies the Gallager’s exponent for coherent multiple-input multiple-output (MIMO) free space optical (FSO) communication systems over gamma–gamma turbulence channels. We assume that the perfect channel state information (CSI) is known at the receiver, while the transmitter has no CSI and equal power is allocated to all of the transmit apertures. Through the use of Hadamard inequality, the upper bound of the random coding exponent, the ergodic capacity and the expurgated exponent are derived over gamma–gamma fading channels. In the high signal-to-noise ratio (SNR) regime, simpler closed-form upper bound expressions are presented to obtain further insights into the effects of the system parameters. In particular, we found that the effects of small and large-scale fading are decoupled for the ergodic capacity upper bound in the high SNR regime. Finally, a detailed analysis of Gallager’s exponents for space-time block code (STBC) MIMO systems is discussed. Monte Carlo simulation results are provided to verify the tightness of the proposed bounds.

Semi-Blind Receivers for UAV M-KRST Coding MIMO Systems Based on Nested Tensor Models

In this letter, we consider the dual-hop and three-hop multiple-input multiple-output (MIMO) sensor systems using multiple Khatri-Rao space-time (M-KRST) coding at the unmanned aerial vehicles and sensor nodes. According to the tensor structure of the communication links, the signals received at the fusion center form two separate nested tensors, which satisfy a nested parallel factor (PARAFAC) model and a nested parallel Tucker2 (PARATUCK2) model. Exploiting this nested structure, two semi-blind receivers based on an alternating least squares algorithm are formulated for a joint estimation of symbols and channels. Compared with the two-stage training method, simulation results demonstrate the superiority of the proposed semi-blind receivers in terms of normalized mean square error and bit error rate.

Effect of Wiring and Cabling Topologies on the Performance of Distributed MIMO OFDM VLC Systems

Since most indoor spaces have multiple luminaires for illumination, for visible light communication (VLC) systems, multiple-input multiple-output (MIMO) communication emerges as a natural solution to improve the data rates and/or the link reliability. The existing works on MIMO VLC systems, however, overlook the characteristics of the lighting infrastructure and the luminaire design, which might have implications for the VLC system design. A luminaire typically consists of multiple LED chips. The wiring topology refers to how the LED chips are connected within the luminaire. The cabling topology, on the other hand, refers to how the luminaires are connected to the communication access point (AP). Based on the type and length of cabling and wiring, significant delays can be introduced, which should be taken into account in channel modeling. In this paper, we adopt the non-sequential ray tracing to model the distributed MIMO VLC channels for various practical wiring and cabling topologies. Based on the developed channel models, we provide a comparative performance analysis of repetition coding (RC), spatial multiplexing (SMUX), and spatial modulation (SMOD) MIMO modes. Our results quantify the effect of wiring/cabling delays and provide insights into the optimized design of lighting infrastructure and luminaires for the support of VLC as an add-on service.

Fast Symbol Detection for Massive G-STBC MIMO Systems

In this paper, a group-based fast symbol detection scheme is proposed for massive Group-wise Space–Time Block Code Multiple-Input Multiple-Output systems. The proposed scheme first chooses a number G, (e.g. $$G=4,6,8$$ ) as the size of each group and then conducts the Minimum Mean Square Error (MMSE) detectors to facilitate symbol detection group by group. In particular, instead of directly using huge computational complexity to compute the MMSE detectors, the proposed scheme recursively finds the corresponding assistant matrices to determine the groups and calculate the MMSE detectors. As a result, the transmitted symbols can be recursively estimated group by group. Finally, simulation results and complexity analysis show the proposed scheme performs very close to the existing methods, while using lower computational complexity.

Distance Hardening in Large MIMO Systems

Asymptotic analysis plays an important role in the performance evaluation and technology design of large multiple-input multiple-output (MIMO) systems. This paper investigates an asymptotic property of large MIMO systems, called distance hardening . It involves distance metrics defined in terms of many factors, such as the channel matrix and the difference matrix of two arbitrary transmitted codewords. The asymptotic property is revealed by the use of the Chernoff bounding method and expressed in an analogous way to the well-known channel hardening. More specifically, we first derive Chernoff bounds on the tail probabilities of distance metrics, in which we are interested. Then, we formulate the asymptotic property based on a generalized definition of the hardening phenomena by referring to a formal definition of the channel hardening. The distance hardening is shown to have implications for space-time code design, MIMO detection, and millimeter wave MIMO systems. Numerical simulations are conducted to verify our theoretical development.

Array Gain Analysis in Molecular MIMO Communications

In this paper, spatial transmission techniques in the area of multiple-input multiple-output (MIMO) diffusion-based molecular communications (DBMC) are investigated. For transmitter-side spatial coding, Alamouti-type coding and repetition MIMO coding are analyzed. At the receiver-side, selection diversity and equal-gain combining are studied as combining strategies. Throughout the numerical analysis, a symmetrical $2\!\times \! 2$ MIMO-DBMC system is assumed. Furthermore, a trained artificial neural network is utilized to acquire the channel impulse responses. The numerical analysis demonstrates that there is no spatial diversity gain in the DBMC system under investigation, but that it is possible to achieve an array gain instead. In addition, it is shown that for MIMO-DBMC systems repetition MIMO coding is superior to Alamouti-type coding.

Coded MIMO With Asymmetric Constellation Sizes

An asymmetric constellation scheme for coded multiple-input–multiple-output (MIMO) transmission is proposed, which applies different constellation mappings to different transmit streams and carefully selects the coding rates for different transmit streams. An improved power allocation is derived to naturally incorporate with the coding rate selection and to further enhance the achievable performance. The proposed scheme provides more flexible choices of data rate selection, and by employing fixed-complexity sphere decoding (FSD) detection, it achieves better performance with reduced detection complexity in comparison with the conventional MIMO using the FSD-based detection with the same constellation set for all streams.

Towards the Next Generation Video Broadcasting: Improved Performance Using Distributed MIMO

Distributed multiple-input multiple-output (MIMO) is a promising technique for the future terrestrial TV broadcasting systems due to its higher efficiency over the traditional single-antenna transmission scheme. In this article, we investigate the application of distributed MIMO technique in the future broadcasting systems. We first show the advantage of the distributed MIMO from the channel capacity perspective. Then different space-time block codes (STBCs) that can be applied in the distributed MIMO broadcasting scenarios are discussed and compared with real system configurations and channel conditions. It is shown that the simple and sophisticated STBCs have mutually complementary application scenarios. Particularly, short 3D MIMO code is a good performance versus decoding complexity compromise among different application scenarios.

IJARCCE - Computer and Communication Engineering

A new technology which we call as Long term evolution (LTE) has brought blazingly fast services to our mobile equipment. LTE, considered as representative of fourth generation wireless systems or the next generation wireless communication, is developed by 3GPP and is specified in release-8 to fulfill the necessities of this era. As LTE inherits a lot from previous 3GPP standards, it is simply the organic evolution of 3G predecessors.LTE has mainly four enabling technologies i.e. OFDM (Orthogonal Frequency Division Multiplexing), MIMO (Multiple Input Multiple Output), Link Adaptation and Turbo Coding. These technologies together contribute and help LTE to meet its requirements and accomplish its goals including high peak data rates, low latency, flexibility in bandwidth, improved capacity, better coverage, multi-antenna support, seamless integration with other open standards and so on. This paper represents a survey on performance bounds in terms of QoS parameters of these four technologies. Different parameters have been considered with respect to different techniques. On the basis of survey bounds that ultimately become bottleneck have been mentioned.

Power Allocation Optimization: Linear Precoding Adapted to NB-LDPC Coded MIMO Transmission

In multiple-input multiple-output (MIMO) transmission systems, the channel state information (CSI) at the transmitter can be used to add linear precoding to the transmitted signals in order to improve the performance and the reliability of the transmission system. This paper investigates how to properly join precoded closed-loop MIMO systems and nonbinary low density parity check (NB-LDPC). Theqelements in the Galois field, GF(q), are directly mapped toqtransmit symbol vectors. This allows NB-LDPC codes to perfectly fit with a MIMO precoding scheme, unlike binary LDPC codes. The new transmission model is detailed and studied for several linear precoders and various designed LDPC codes. We show that NB-LDPC codes are particularly well suited to be jointly used with precoding schemes based on the maximization of the minimum Euclidean distance (max-dmin) criterion. These results are theoretically supported by extrinsic information transfer (EXIT) analysis and are confirmed by numerical simulations.

Progressive edge-growth algorithm for low-density MIMO codes

In low-density parity-check (LDPC) coded multiple-input multiple-output (MIMO) communication systems, probabilistic information are exchanged between an LDPC decoder and a MIMO detector. The MIMO detector has to calculate probabilistic values for each bit which can be very complex. In [1], the authors presented a class of linear block codes named low-density MIMO codes (LDMC) which can reduce the complexity of MIMO detector. However, this code only supports the outer-iterations between the MIMO detector and decoder, but does not support the inner-iterations inside the LDPC decoder. In this paper, a new approach to construct LDMC codes is introduced. The new LDMC codes can be encoded efficiently at the transmitter side and support both of the inner-iterations and outer-iterations at the receiver side. Furthermore they can achieve the design rates and perform very well over MIMO channels.

Block-Wise QR-Decomposition for the Layered and Hybrid Alamouti STBC MIMO Systems: Algorithms and Hardware Architectures

Unlike the channel matrix in the spatial division multiplexing (SDM) multiple-input multiple-output (MIMO) communication system, the equivalent channel matrix in the layered Alamouti space-time block coding (STBC) MIMO system comprised 2-by-2 Alamouti sub-blocks. One novel property, found by Sayed about the QR-decomposition (QRD) of this equivalent channel matrix is that the produced Q- and R-matrices are also matrices with Alamouti sub-blocks. Taking advantage of this property, we propose a new block-wise complex Givens rotation (BCGR) based algorithm and a triangular systolic array (TSA) to compute the QRD of the equivalent channel matrix in an Alamouti block by block manner. Implementation results reveal that our new TSA can compute QRDs of 4-by-4 equivalent channel matrices faster than any architecture that has been developed for the SDM MIMO system. This property of fast QRD makes our TSA very attractive for the layered Alamouti STBC MIMO system combined with the orthogonal frequency division multiplexing. Our new BCGR based approach can also be applied to the hybrid Alamouti STBC MIMO system, which is also a system with equivalent channel matrix consisting of Alamouti sub-blocks.

Performance Comparison of Space Time Block Coding with Code Rate ½ and ¾ for Turbo Coded Multiple Input Multiple Output System

This paper compares the performance of Space Time Block Coding with code rate ½ and ¾ for a Turbo Coded Multiple Input Multiple Output (MIMO) system and uncoded MIMO system. Turbo encoder encodes the input information bits and sends to a QPSK or 16 QAM or 64 QAM modulator. Modulated symbols are mapped by STBC. Outputs of STBC split into n streams which are simultaneously transmitted using n transmit antennas. The Rayleigh fading effected received signal at receiver is a linear superposition of the transmitted signals. It is observed that t here is around 7-11 db coding gain for using code rate ½ compared to code rate ¾ of a TC coded MIMO system and there is around 8-10 db coding gain for using code rate ½ compared to code rate ¾ of a uncoded MIMO system.

Achieving low-complexity maximum-likelihood detection for the 3D MIMO code

Abstract The 3D Multiple-input multiple-output (MIMO) code is a robust and efficient space-time block code (STBC) for the distributed MIMO broadcasting but suffers from high maximum-likelihood (ML) decoding complexity. In this paper, we first analyze some properties of the 3D MIMO code to show that the 3D MIMO code is fast decodable. It is proven that the ML decoding performance can be achieved with a complexity of O(M 4.5) instead of O(M 8) in quasi-static channel with M-ary square QAM modulations. Consequently, we propose a simplified ML decoder exploiting the unique properties of the 3D MIMO code. Simulation results show that the proposed simplified ML decoder can achieve much lower processing time latency compared to the classical sphere decoder with Schnorr-Euchner enumeration.

Improved K-Best Sphere Detection for Uncoded and Coded MIMO Systems

The conventional K-best sphere decoder (KSD) keeps the best K nodes at each level of the search tree. In addition to retaining the best K nodes, we also consider all the nodes whose costs are within a certain margin of the cost of the Kth best node. The resulting algorithm is called improved K-best sphere decoder (IKSD). Three IKSD variants are considered in this letter, which are fixed threshold, normalized threshold and adaptive threshold IKSD. The proposed IKSD requires a smaller K (indicating lower complexity) while still achieving a better and near optimal performance compared to the conventional KSD. These gains are confirmed by the simulation results. For example, for the fixed threshold IKSD in a 4 x 4 16-QAM multiple-input multiple-output (MIMO) system, with K=2, it achieves the same performance as the conventional KSD (K=16), yielding about 80% complexity savings. For coded MIMO systems, the IKSD is also extended as a list sphere decoder for joint iterative detection and decoding.

Peak-to-Average Power Ratio Analysis for Golden Coded MIMO Systems

combination of the orthogonal frequency-division multiplexing (OFDM) technique and the multiple-input multiple-output (MIMO) architecture has emerged as a promising candidate for future wireless communications. The Space-time block coding (STBC) technique permits to fully take advantage of MIMO-OFDM systems and to effectively improve the channel capacity and the spatial diversity. The Golden Code (GC) is a full-rate and full-diversity, space-time code for 2 × 2 MIMO systems. Thanks to its algebraic construction, the GC achieves Diversity-Multiplexing gain trade-off and preserves the mutual information. However, it is well known that STBC-MIMO-OFDM systems are sensitive to the high Peak-to-Average-Power Ratio (PAPR) of the transmitted signals. The purpose of this paper is to analyze the PAPR of golden coded MIMO-OFDM systems. We investigate the effect of the roll-off factor on the PAPR characteristics and analyze the system performances. KeywordsOFDM, PAPR, Golden Code.

Enhancing the Performance of the SIC-MMSE Iterative Receiver for Coded MIMO Systems via Companding

Iterative detection and decoding (IDD) method based on soft interference cancellation and minimum-mean squared-error filtering (SIC-MMSE) has received considerable attention in recent years due to its good performance-complexity tradeoff for coded multiple-input multiple-output (MIMO) systems. The Gaussianity of the a priori and a posteriori log-likelihood ratios (LLRs) computed at the constitute stages of the SIC-MMSE iterative receiver is a presumption for IDD to work. In this letter, the Gaussianity assumption is first shown to be not tight for high rate coded MIMO systems and thus leads to poor performance (for high rate coded MIMO systems). Then a non-linear companding based transformation method is incorporated into the SIC-MMSE iterative receiver to alleviate the non-Gaussianity of the a priori and a posteriori LLRs due to the imperfection of the (high-rate) code and per-stream approximation. Analytical and numerical results show that the proposed transformed SIC-MMSE iterative receiver achieves significant performances gains over the conventional one for coded MIMO systems, in particular, high rate coded ones with even lower computational complexity.

Double-Layer Low-Density Parity-Check Codes over Multiple-Input Multiple-Output Channels

We introduce a double-layer code based on the combination of a low-density parity-check (LDPC) code with the multiple-input multiple-output (MIMO) system, where the decoding can be done in both inner-iteration and outer-iteration manners. The present code, called low-density MIMO code (LDMC), has a double-layer structure, that is, one layer defines subcodes that are embedded in each transmission vector and another glues these subcodes together. It supports inner iterations inside the LDPC decoder and outeriterations between detectors and decoders, simultaneously. It can also achieve the desired design rates due to the full rank of the deployed parity-check matrix. Simulations show that the LDMC performs favorably over the MIMO systems.