Differential Space-time Block Research Articles

A Hybrid Differential Detection Scheme for the Ultra-Wideband Orientational Beamforming System

Differential space-time coding methods have been investigated for ultra-wideband communication systems to avoid channel estimation. However, their performance in the line-of-sight (LOS) environment is worse than the recently proposed orientational beamforming (OBF) system under low signal-to-noise ratios (SNRs). On the other hand, the OBF system cannot work well in the non-LOS (NLOS) environment. To address these issues, a hybrid differential detection (HDD) scheme is proposed in this paper, which combines the OBF system with a proposed differential OBF (DOBF) system. First, the DOBF system with a fully differential detection scheme is proposed, whose performance is almost the same as the differential space-time block coding method. However, its detection complexity only linearly increases with the number of transmitting antennas. Then, the HDD scheme is proposed, with its decision statistic being a combination of a modified OBF decision statistic and the DOBF decision statistic. In the NLOS environment, the HDD scheme is reduced to the DOBF system. In the LOS environment, a combination coefficient is obtained by mapping an SNR-related factor through a sigmoid function. The optimal parameters for the sigmoid function are determined through simulations, with which the proposed HDD scheme can achieve overall better performance than the OBF and DOBF systems.

SDR DESIGN AND IMPLEMENTATION OF DIFFERENTIAL STBC TRANSMISSION

Multiple-input-multiple-output (MIMO) technology uses multiple antennas and advanced signal processing to increase the communication system capacity, reliability and data rate without sacrificing energy consumption or RF bandwidth. In some scenarios, the MIMO communication system need to be designed without knowledge of the channel state information. One possible solution is differential space–time block coding (DSTBC). Ettus USRPs (Universal Software Radio Peripherals) are used in this research work to prototype a DSTBC-based 2 × 1 MISO (multiple-input-single-output) communication system. The signal processing is performed by software with MATLAB. This software defined radio (SDR) approach allows a reconfigurable implementation of the Differential STBC algorithm with tuneable parameters.

Differential STBC-SM Scheme for Uplink Multi-User Massive MIMO Communications: System Design and Performance Analysis

In this paper, a novel differential space-time block coded spatial modulation (differential STBC-SM) is proposed for uplink multi-user massive multiple-input multiple-output (MIMO) communications, which combines the concept of differential coding and STBC-SM to enhance the diversity benefits in the absence of the channel state information (CSI). The transmission structure of the proposed system is on a block basis, where each block contains two sub-blocks. More specifically, the first sub-block only conveys amplitude and phase modulation (APM) symbol bits, since its transmit antennas (TAs) obey a pre-designed activation pattern, which do not carry any information bit. For the second sub-block, the input bits are modulated to STBC-SM matrices, which are then differentially coded between two adjacent sub-blocks. Moreover, a novel block-by-block based non-coherent detector is presented. Finally, we derive an upper bound on the average bit error probability (ABEP) by using the moment generating function (MGF). Our simulation results show that the proposed differential STBC-SM transmission structure is able to acquire considerable bit error rate (BER) performance improvements compared to both the conventional differential spatial modulation (DSM) and differential Alamouti schemes.

Blind frame synchronization in a transmission system with differential space-time block coding

Blind frame synchronization in a transmission system with differential space-time block coding

Low complexity decoding algorithm for differential space-time block coding transmission systems

Low complexity decoding algorithm for differential space-time block coding transmission systems

Energy efficient decision fusion for differential space-time block codes in wireless sensor networks

The non-coherent techniques that do not require the channel state information have gained significant interest especially when multiple transmitter and receiver nodes are involved in communication. In this paper, we analyze the energy efficiency of differential and coherent cooperative Multiple-input Multiple-output (MIMO) method using space-time block codes (STBC). We exploit the benefits of the extension of the observation interval of differential STBC to three blocks in Wireless sensor networks (WSNs). We propose an energy efficient decision fusion (EEDF) algorithm in WSNs which utilizes the benefits of Multiple symbol differential detection (MSDD) decision fusion by optimally selecting the ring amplitude of the differential amplitude phase shift keying (DAPSK) constellation. The simulation results show that processing differential multiple symbols provides significant energy saving compared to the conventional two-symbol processing. Furthermore, significant performance gain is achieved for the proposed algorithm compared to 16 DPSK MSDD decision fusions.

Development of blind frame synchronization for transfer system with differential space-time block coding

The object of this research is the methods and algorithms for frame synchronization used in multi-antenna radio systems (Multiple Input Multiple Output – MIMO). The implementation of radio communication systems and, in particular, MIMO, implies that the demodulator synchronizes the phase of the reference carrier and the time of signal processing processes. Time synchronization is divided into symbolic and frame synchronization. As for the synchronization of the reference carrier and symbol synchronization, these types of synchronization are provided by traditional methods and are not considered in this paper. The frame synchronization in the vast majority of cases is provided by the use of pilot signals (sync words). At their core, they are markers and are periodically embedded in the data stream to indicate the beginning of another new data block. The resources of the transmission system, spent on the transmission of pilot signals, are not used to transmit user information, as a result of which the efficiency of using the time-frequency resource of the system is degraded. To a lesser extent, there are so-called «blind» signal processing methods based on the redundancy properties of the transmitted signal. These methods have no drawbacks from the use of pilot signals and are divided into methods for assessing the state of the communication channel, signal identification, and synchronization. Based on this, such methods are of practical interest.In this work, let’s propose a frame synchronization method for demodulating differential space-time block coding signals using MIMO technology. The synchronization algorithm does not require the use of preambles and sync words, which ensure efficient use of the time-frequency resource. An analysis of the structure of the algorithm and the simulation results show its performance at low signal-to-noise ratios in the transmission system. The algorithm does not require knowledge of the state of the communication channel, has low computational complexity compared to existing analogues, and allows implementation with a different number of transmitting and receiving antennas.

Improvement of FER using Differential Space-Time Block Code

Over recent years, various modulation and coding techniques have been proposed in MIMO wireless communication systems. A MIMO system uses the concept of spatial diversity which is very successful and promising technique. When a coherent transmission system is considered, the estimation of radio channel impulse response is done precisely. In MIMO systems, the radio channel is estimated among every transmitting and receiving antennas such that the complexity can be increased. For this reason, in MIMO systems differential modulation schemes are estimated. A Differential Space-Time Block Code (DSTBC) is useful in the Raleigh fading channel as they do not require channel estimates. Space-time coding with MIMO antennas at transmitting and receiving reduces the consequences of fading in multiple paths and therefore the performance of digital transmission throughout wireless radio channel can be improved. So it has been presumed that perfect CSI is available at the receiver and coherent detection is employed. This paper presents improvement of Frame Error Rate (FER) for differential space-time block code using various Doppler spectra. When the channels estimates are not available the DSTBC system noticed that at SNR of 10 dB, for two transmitting and four receiving antennas the FER is 0.0067 for rounded Doppler spectrum. The differential schemes attains full transmit diversity owing to orthogonal designs. However, the receiver or the transmitter needs the channel state information so these differential schemes are 3 dB worse than the STBC with coherent detection.

Decision-Feedback Aided Multiple-Symbol Differential Detection in Two-Way Relay Transmission

In this paper, noncoherent transmission algorithms are proposed in a two-way relay transmission (TWRT), where differential space-time block codes based multiple-symbol differential detection (MSDD) is performed. Specifically, generalized likelihood ratio test aided MSDD (GLRT-MSDD) is developed with the exhaustive search in the TWRT. In order to solve the challenging problem of high complexity, the GLRT-MSDD model is reformulated and a decision-feedback aided MSDD (DF-MSDD) model is derived. Furthermore, performance analysis and the simulations confirm that the proposed DF-MSDD provides solid bit error-rate performance with a lower complexity than GLRT-MSDD in the TWRT.

Development of a differential block coding method for application in mobile radio communication systems using MIMO systems

The object of this research is the methods and algorithms of space-time block coding, which are also used in multi-antenna radio communication systems (Multiple Input Multiple Output – MIMO). The implementation of MIMO systems for coherent reception or precoding of data implies knowledge of information about the state of the communication channel and, accordingly, compensation for its impact. For channel estimation, together with information signals, pilot signals are transmitted, previously known at the receiving side. The frequency of sending these signals depends on factors that change the state of the communication channel, for example, one of which is the high speed of movement of mobile stations. But since the pilot signals do not carry user information, the resource of the system is consumed, which impedes the efficient use of the radio frequency spectrum.In the course of the study, a method was considered that admits the absence of the need for knowledge of the state of the communication channel – relative phase modulation, which was taken as a basis and distributed for use in MIMO systems. This method provides for incoherent reception, but, despite this, its use is fully justified, based on the results of the study. Effective tree coding and an algorithm for compensating the noise components of the received signal were also developed and integrated into the system. This, accordingly, allows to optimize the computational power of the system implementation and to approximate the proposed method of differential space-time block coding (DSTBC) to the methods of coherent reception.Using the MATLAB software package, the proposed DSTBC method is simulated for various options for the number of transmitting and receiving antennas and types of modulation. A comparison is made and the advantages of the DSTBC method are determined. The described method can find application in modern radio communication systems with rapidly changing communication channel parameters due to the high speed of movement of mobile stations.

Adaptive Coherent/Non-Coherent Single/Multiple-Antenna Aided Channel Coded Ground-to-Air Aeronautical Communication

In this treatise, first of all, we conceive a generic multiple-symbol differential sphere detection (MSDSD) solution for both single- and multiple-antenna-based noncoherent schemes in both uncoded and coded scenarios, where the high-mobility aeronautical Ricean fading features are taken into account. The bespoke design is the first MSDSD solution in the open literature that is applicable to the generic differential space-time modulation (DSTM) for transmission over Ricean fading. In the light of this development, the recently developed differential spatial modulation and its diversity counterpart of differential space-time block coding using index shift keying are specifically recommended for aeronautical applications owing to their low-complexity single-RF and finite-cardinality features. Moreover, we further devise a noncoherent decision-feedback differential detection and a channel-state information estimation aided coherent detection, which also take into account the same Ricean features. Finally, the advantages of the proposed techniques in different scenarios lead us to propose for the aeronautical systems to adaptively: 1) switch between coherent and non-coherent schemes; 2) switch between single- and multiple-antenna-based schemes as well as; and 3) switch between high-diversity and high-throughput DSTM schemes.

Finite-Cardinality Single-RF Differential Space-Time Modulation for Improving the Diversity-Throughput Tradeoff

The matrix-based differential encoding invoked by Differential Space-Time Modulation (DSTM) typically results in an infinite-cardinality of arbitrary signals, despite the fact that the transmit antennas (TAs) can only radiate a limited number of patterns. As a remedy, the recently developed differential spatial modulation (DSM) is capable of avoiding this problem by conceiving a beneficial sparse signal matrix design, which also facilitates low-complexity single-RF signal transmission. Inspired by this development, the differential space-time block code using index shift keying (DSTBC-ISK) further introduces a beneficial diversity gain without compromising the DSM’s appealingly low transceiver complexity. However, the DSTBC-ISK’s performance advantage tends to diminish as the throughput increases, especially when an increased number of Receive Antennas (RAs) is used. By contrast, the classic Differential Group Code (DGC) that actively maximizes its diversity gain for different multiple-input-multiple-output (MIMO) system setups is capable of achieving a superior performance, but its detection complexity grows exponentially with the throughput. Against this background, we propose the differential space-time shift keying using Diagonal Algebraic Space-Time scheme, which is the first DSTM that is capable of achieving the DGC’s superior diversity gain at high throughputs without compromising the DSM’s low transceiver complexity. As a further advance, we also conceive a new differential space-time shift keying using Threaded Algebraic Space-Time arrangement, which is capable of achieving an even further improved diversity gain at a substantially reduced signal detection complexity compared to the best DGCs. Furthermore, in order to strike a practical tradeoff, we develop a generic multi-element and multi-level-ring Amplitude Phase Shift Keying design, and we also arrange for multiple reduced-size DSTM sub-blocks to be transmitted in a permuted manner, which exhibits an improved diversity-throughput tradeoff.

Bandwidth Efficiency Improvement for Differential Alamouti Space-Time Block Codes Using M-QAM

We propose a technique that enhances the bandwidth efficiency of the two transmit antenna differential space-time block code (DSTBC) by use of space-time block code (STBC) expansion and trellis coding. STBC expansion is realized by expanding the conventional Alamouti STBC using unitary matrix transformation. This is followed by trellis code-aided mapping of additional bits to space-time codes of the expanded set. Trellis code-aided mapping of additional bits enhances the bandwidth efficiency of the proposed DSTBC scheme. The proposed scheme sends more information bits in each transmitted space-time code than the conventional differential detection-aided DSTBC (CDD-DSTBC) scheme, and yet retains the same error performance. For each additional bit sent with the transmitted space-time codeword, the proposed scheme using 16QAM achieves a 12.5% increase in bandwidth efficiency, while the scheme using 64QAM realises an 8.3% increase. Simulation results demonstrate that the error performance of the proposed scheme tightly matches that of CDD-DSTBC with improvement in bandwidth efficiency. The bandwidth efficiency is enhanced at the expense of a moderate increase of the computational complexity at the receiver.

Single-RF Index Shift Keying Aided Differential Space–Time Block Coding

We propose a new single-RF differential space–time block coding using index shift keying (DSTBC-ISK), which is the first differential space–time modulation (DSTM) scheme that can simultaneously achieve the following three imperative objectives: First, forming a finite-cardinality transmit-signals set; second, retaining a single-stream maximum-likelihood (ML) detection complexity; and third, offering a beneficial transmit diversity gain. In order to make a fair comparison, we also conceive a low-complexity single-stream detector for DSM. Furthermore, in order to improve the performance of finite-cardinality DSTM schemes at higher throughputs, we propose to generalize both differential amplitude shift keying (DASK) and amplitude shift keying (ASK), which subsume the existing two-/four-level-ring star quadratic–amplitude modulation (QAM) solutions as special cases. As a result of using star QAM signaling, the power of the DSTM's signal matrix becomes variable. Against this background, we further develop bespoke ML, minimum mean squared error, and least-square detectors for DSTM using DASK/ASK. Our simulation results demonstrate that the proposed DSTBC-ISK is capable of achieving substantial diversity gains over DSM without eroding its low transceiver complexity.

Performance Analysis and Compensation of Joint TX/RX I/Q Imbalance in Differential STBC-OFDM

Differential space time block coding (STBC) achieves full spatial diversity and avoids channel estimation overhead. Over highly frequency-selective channels, STBC is integrated with orthogonal frequency division multiplexing (OFDM) to efficiently mitigate intersymbol interference effects. However, low-cost implementation of STBC-OFDM with direct-conversion transceivers is sensitive to In-phase/Quadrature-phase imbalance (IQI). In this paper, we quantify the performance impact of IQI at both the transmitter and receiver radio frequency front-ends on differential STBC-OFDM systems which has not been investigated before in the literature. In addition, we propose a widely-linear compensation algorithm at the receiver to mitigate the performance degradation caused by the IQI at the transmitter and receiver ends. Moreover, a parameter-based generalized algorithm is proposed to extract the IQI parameters and improve the performance under high-mobility. The adaptive compensation algorithms are blind and work in a decision-directed manner without using known pilots or training sequences. Numerical results show that our proposed compensation algorithms can effectively mitigate IQI in differential STBC-OFDM.

Blind SLM for PAPR reduction of Alamouti DSFBC systems

The combination of differential space-time block codes and orthogonal frequency-division multiplexing (OFDM) as differential space-frequency block coded (DSFBC)-OFDM system is a good candidate to achieve maximum diversity without the need to channel estimation. High peak-to-average-power ratio (PAPR) is a major drawback in these systems. The available PAPR reduction methods are not directly applicable in DSFBC-OFDM system. In this study, the proper application of selected mapping (SLM) method for reducing PAPR in Alamouti DSFBC-OFDM system is investigated and two different schemes are presented: conventional SLM (C-SLM) and blind differential SLM (BD-SLM). In C-SLM technique, the index of the selected phase sequence must be sent to the receiver side as the side information (SI). In the proposed BD-SLM method, specific phase mask vectors are generated with one-to-one correspondence with the different phase rotation sequences. Then at the receiver side, a differential minimum Hamming distance decoder is introduced to detect the index of optimum phase mask vectors without SI. Simulation results show that the proposed BD-SLM scheme (without the need to SI) provides good performances of both the bit error rate and PAPR reduction compared with C-SLM method.

Food Communication System Evaluation of LDPC Codes Combined with Differential Space-time Block Codes

Food Communication System Evaluation of LDPC Codes Combined with Differential Space-time Block Codes

Differential Orthogonal Space-Time Block Coding Modulation for Time-Variant Underwater Acoustic Channels

Reliable underwater acoustic (UWA) communications are challenging since the channels are well known to be doubly selective in both time and frequency domains. The doubly-selective fading UWA channels, however, also provide double diversity gains. In addition, multiple transducers and/or hydrophones are often deployed, providing space diversity to combat channel fading. To exploit all these diversities, a differential multiple-input–multiple-output (MIMO) scheme for doubly-selective fading channels is presented in this paper. The proposed differential orthogonal space-time block coding (DOSTBC) approach adopts the basis expansion model (BEM) to capture the channel variation in time domain. Both analytical and simulated results show that the proposed BEM–DOSTBC approach is reliable by collecting 3-D diversity: space, multipath, and Doppler. The proposed approach was tested during the RACE08 sea experiment and its reliability was confirmed by the experiment results.

Non-Coherent Open-Loop MIMO Communications Over Temporally-Correlated Channels

This paper investigates the use of non-coherent communication techniques for open-loop transmission over temporally-correlated Rayleigh-fading MIMO channels. These techniques perform data detection without knowing the instantaneous channel coefficients. Three non-coherent Multiple Input Multiple Output (MIMO) schemes, namely, differential unitary space-time modulation, differential space-time block code, and Grassmannian signaling, are compared with several state-of-the-art training-based coherent schemes. This paper shows that the non-coherent schemes are meaningful alternatives to training-based communication, specially as the number of transmit antennas increases. In particular, for more than two transmit antennas, non-coherent communication provides a clear advantage in medium to high mobility scenarios.

Distributed Differential Quasi-Orthogonal Space-Time Block Coded System for Multiple-Relay Networks

In this paper, we present an efficient distributed differential quasi-orthogonal space-time block code (DD-QOSTBC) system for multiple relay networks. First, we propose the DD-QOSTBC transmission which considers two robust STBC-like subsystems in amplify-and-forward multiple relaying over flat fading channel. It is assumed that source has two antennas, and relays and destination have a single antenna. With robust STBC-like subsystem structure, we show that our robust subsystems can be used for an efficient joint suboptimal differential decoding based on a maximum likelihood criterion. Finally, we accomplish the performance evaluation on the proposed DD-QOSTBC system in terms of bit-error-rate.