Direct Sequence Ultra Wideband Research Articles

Pulse-Shaped Walsh–Hadamard Orthogonal Signaling for Multiuser DS-UWB Systems

This article presents signaling schemes for direct-sequence ultrawideband (DS-UWB) multiuser communication with pulse shaping and orthogonal Walsh–Hadamard (WH) modulation. A waveform design approach is applied to obtain novel UWB pulses with strict spectral emission compliance and improved multiaccess capability. WH codeword sequences are then combined with optimally shaped DS-UWB signals, yielding orthogonal modulation formats that can be scaled to variable order while retaining the desired spectral characteristics and achieving robust performance in multiuser, multipath-impaired environments. Interference analysis with a random spreading model is used to derive decision statistics with MRC over frequency-selective Nakagami fading channels, and analytical expressions are obtained for outage and bit error probabilities. Comparative numerical results and sensitivity analysis with respect to waveform selection, modulation order, and channel parameters are given to demonstrate the merits of the proposed orthogonal WH-based DS-UWB schemes in terms of improved outage and error performance, and increased multiuser capacity.

A new insightful exploration into a low profile ultra-wide-band (UWB) microstrip antenna for DS-UWB applications

Designing a simple and planar antenna for high speed short distance ultra-wideband (UWB) communication has become a buzzword over the last few years. There are two very different categories of UWB technologies of vital relevance, i.e. (i) carrier-free direct sequence UWB (DS-UWB), and (ii) the Multi-Band orthogonal frequency division multiplexing UWB (OFDM UWB) technology. In, Multi-Band OFDM UWB technology, multi narrowband UWB antennas with frequency notches are required. However, in DS-UWB technology, the frequency spectrum of very short duration transmitted pulses occupies wide bandwidth, and hence to transmit it, the antenna should be fully matched over the entire bandwidth without the presence of any frequency notch. In this paper, a novel, small and completely planar air gap and defected ground slot integrated rectangular microstrip antenna with dual shorting posts have been thoroughly investigated to yield UWB, i.e. (109%) bandwidth without the presence of any frequency notch.

A Novel Multiuser Detector for LDPC-Coded DS-UWB Space Formation Flying

Space formation flying has attracted a lot of attention recently. In this paper, we using direct-sequence ultra-wideband (DS-UWB) as the physical layer of inter-spacecraft communications. The traditional multiuser detection method like soft-input soft-output (SISO) cost too much computation. The proposed multiuser detector no longer uses interleaving, and the computational complexity has a linear relationship with the number of users. The bit error ratio (BER) simulation result shows that the proposed method approaches the single-user system with increasing signal-to-noise ratios (SNRs).

A FPGA implementation of GMM MUD algorithm for space formation aircraft communication system

Space formation aircraft communication system needs to meet strong anti-interference ability, low power consumption and high transmission rate performance. Ultra-wideband (UWB) has high data transfer rate, low device complexity, high interference resistance and confidentiality. Therefore, UWB technology is used in space formation aircraft communication system, which is direct sequence ultra-wideband (DS-UWB) space formation aircraft communication system. This paper, we put forward a multi-user detection (MUD) algorithm based on Gaussian Mixture Model (GMM) in DS-UWB communication system and its field-programmable gate array (FPGA) implementation. We adopt a way which based on MATLAB and FPGA platform, and results show that MUD algorithm based on GMM has better bit error rate (BER) performance compared to classical multi-user detection algorithm.

Виокремлення корисної інформації з над широкосмугової хвилі у ближній зоні випромінювання

The authors study the dependence of the shape of electromagnetic pulse received in near radiation zone of the antenna on the observation point. The paper discusses negative and positive effects of this phenomenon on the wireless impulse communication and presents a new method of information extraction form ultrawideband electromagnetic pulse, comparing it to the traditional way of signal processing. The method is based on modern deep learning technics and recurrent neural networks, namely physical long short-term memory. Moreover, the paper presents a concept of direct sequence ultrawideband (DS-UWB) impulse radio receiver based on a physical neural network. It is proposed to change the traditional way of radio signal processing and use a single neural network instead of a matched filter, a magnitude amplifier and a FPGA processor. The architecture of the physical neural network was designed with an intention to study the behavior of ultrawideband short pulse (UWB-SP) radio signal in near and far radiation zones. The applicability of the neural radio concept is proved by simulation of AWGN communication channel for multiuser environment and real time RX signal processing by the designed neural network. The paper contains the results of a numerical modeling of the radiation-reception process and illustrations of the neural network training process. The lens impulse radiation antenna is considered as radiator of transient electromagnetic field for simulation. The radiation process is modeled with the help of the antenna’s transient response obtained using the evolution approach and the superposition principle in the form of Duhamel integral. The prospects of using the proposed methodology in the problems of the Internet of Things are analyzed. The study shows that using the proposed method allows solving multipathing and multiuser problems even in near radiation zone.

GMM-MUD: An Effective Multiuser Detection Algorithm for DS-UWB-Based Space Formation Flying Systems

In this paper, an effective multiuser detection (MUD) is proposed for direct sequence ultrawideband- (DS-UWB-) based space formation flying systems. The proposed method called GMM-MUD is based on Gaussian mixture models (GMMs) to suppress multiple access interference. The GMM describes probability distributions of the hypothesis testing problem which is used for bit classification. To reveal the difference between correct bits and error bits, the preprocessing operation applies a mapping function based on optimal multiuser detection. The parameters of GMM are estimated by using expectation-maximization (EM) algorithm. EM algorithm employs iterative operation to simplify the complexity of maximum likelihood estimation method and considers the mapping values of received bits as the observations. Simulation results demonstrate that the proposed GMM-MUD algorithm achieves good performances in terms of bit error rate performance, user capacity, and near-far resistance. Moreover, the computational complexity is low enough for space formation flying applications.

HSBCS framework based performance detection for DS-UWB Systems

Multi-users interference in direct sequence ultra wideband (DS-UWB) communication is the hotspot research for wireless communication. In this paper, using the wavelet coefficient transform signal in DS-UWB communication, we establish the tree-based hierarchy shrinkage Bayesian compressive sensing (HSBCS) framework for multi-users interference models and noise model generalization. The Markov chain Monte Carlo (MCMC) multi-user interference algorithm by use of HSBCS framework is proposed to suppress noise in the presence of multi-user interference in the DS-UWB communications. The target of this paper is to detect the noise suppression performance of multi-user interference in the DS-UWB communications including normal mean square error (NMSE) performance and peak signal-to-noise-ratio (PSNR) performance using HSBCS framework. Simulation results show that NMSE and PSNR performance of tree-based HSBCS algorithm is better than that of the other algorithms with no tree structure. Otherwise, with more users increasing, the error probability performance of MCMC multiuser interference algorithm in the presence of multiuser interference by use of HSBCS framework is lowest and gradually approach zero.

Photonic generation of bipolar direct-sequence UWB signals based on optical spectral shaping and incoherent frequency-to-time conversion

A novel technology to obtain binary phase-coded ultrawideband (UWB) signals for direct-sequence spread-spectrum communication systems is investigated by using a cost-effective incoherent source. The bipolar encoding is performed based on an all-fiber spectrum shaper composed of two FBG arrays to tailor the optical spectrum, and a section of single-mode fiber to achieve incoherent frequency-to-time conversion. We demonstrate a 1.325-Gb/s UWB encoding system by the use of binary spreading codes of 4-chip length via computer simulations. The proposed bipolar UWB encoding technology can be applied to high-speed UWB-over-fiber communication systems.

Efficient DS-UWB MUD Algorithm Using Code Mapping and RVM

A hybrid multiuser detection (MUD) using code mapping and a wrong code recognition based on relevance vector machine (RVM) for direct sequence ultra wide band (DS-UWB) system is developed to cope with the multiple access interference (MAI) and the computational efficiency. A new MAI suppression mechanism is studied in the following steps: firstly, code mapping, an optimal decision function, is constructed and the output candidate code of the matched filter is mapped to a feature space by the function. In the feature space, simulation results show that the error codes caused by MAI and the single user mapped codes can be classified by a threshold which is related to SNR of the receiver. Then, on the base of code mapping, use RVM to distinguish the wrong codes from the right ones and finally correct them. Compared with the traditional MUD approaches, the proposed method can considerably improve the bit error ratio (BER) performance due to its special MAI suppression mechanism. Simulation results also show that the proposed method can approximately achieve the BER performance of optimal multiuser detection (OMD) and the computational complexity approximately equals the matched filter. Moreover, the proposed method is less sensitive to the number of users.

DS-UWB pulse design in IEEE802.15.3a multipath fading channel for cognitive radio applications

This paper presents a novel spectrum shaping technique in direct sequence ultra-wideband (DS-UWB) communication systems. This proposed pulse introduces spectral nulls to limit the interference impact of high power coexisting narrowband signals and to elevate the applications of cognitive radio. The idea depends on the addition and subtraction of several UWB Gaussian derivative pulses in order to design a new pulse that has spectral null at the operating frequency of the narrowband interference (NBI) signal. The use of the Gaussian derivative ensures that the UWB spectrum mask established by the Federal Communications Commission (FCC) is met. The NBI signals are modelled as either the wireless local area network (WLAN) IEEE802.11n which operates in the 5 GHz frequency band or multi tone signals. The power spectral density of the proposed transmitted UWB pulse is derived analytically. The bit error rate performance of the proposed pulse is derived in the multi-path IEEE802.15.3a UWB fading channel models and validated with simulations. Results show that the impact of either the IEEE802.11n interference signal or the multi tone interference signals can be effectively suppressed by transmitting and matched filtering the new pulse with a single or multiple spectral nulls at the interference operating frequencies.

Multilead ECG data compression using SVD in multiresolution domain

Abstract In this paper, multilead electrocardiogram (MECG) data compression using singular value decomposition in multiresolution domain is proposed. It ensures a high compression ratio by exploiting both intra-beat and inter-lead correlations. A new thresholding technique based on multiscale root fractional energy contribution is proposed. It selects the singular values depending on the clinical importance of the wavelet subbands. The proposed method is evaluated with the PTB Diagnostic ECG database. This compression method is embedded with a pulse amplitude modulated direct sequence-ultra wideband technology for transmission of the MECG data. This may be useful in telemonitoring services for the wireless body sensor network. A comparative study of computational time complexity has also been carried out. The results show that the proposed method can be executed at least three times faster than the existing methods. The storage efficiency is enhanced by 19 times using this method.

Signal Design for Improved Multiple Access Capacity in DS-UWB Communication

The paper addresses the signal design and performance analysis of direct-sequence ultra-wideband (DS-UWB) multiuser communication employing offset quadrature-spread phase shit keying (OQPSK) modulation with novel chip waveforms. Analytical bit error rate (BER) performance analysis is derived for different receiver structures, emphasizing the impact of the chip mean-squared auto-correlation function (MS-ACF) on BER performance in multiuser and multipath environments. A low-complexity flexible algorithm for designing chip pulses that maximize multiuser system capacity by minimizing the chip MS-ACF is proposed. The optimized waveforms are based on the use of prolate spheroidal wave function (PSWF) expansions. The proposed schemes also provide increased spectrum placement flexibility and minimized phase jumps compared to carrier-less pulse amplitude modulation (PAM) UWB schemes. Several design examples and numerical results are presented to illustrate the relative performance of the novel pulses compared to UWB schemes employing Gaussian monocycle derivatives and modified Hermite polynomials, and it is shown that a clear improvement in multiple access capacity can be achieved by the proposed PSWF-based pulses, particularly with maximum ratio combining receivers.

FPGA implementation of rapid PN code acquisition using iterative message passing algorithms

Spread-spectrum (SS) techniques are widely used in many military communication systems because they have many advantages, such as ranging capabilities, antijam protection, low probability of detection or interception, and multiple access capability. There are many forms of SS, such as a direct sequence spread spectrum (DS/SS), frequency hopping (FH), hybrid DS-FH, and ultrawideband (UWB). In all cases, pseudorandom or pseudonoise (PN) sequences play important roles. They are periodic sequences with a long period in practical systems. The long PN sequences are desirable to reduce the probability of detection by an unintended receiver over a short time interval. But it is also a challenge for a receiver to detect and acquire the signal.

Adaptive Frequency-Domain Group-Based Shrinkage Estimators for UWB Systems

In this work, we propose low-complexity adaptive biased estimation algorithms, called group-based shrinkage estimators (GSEs), for parameter estimation and interference suppression scenarios with mechanisms to automatically adjust the shrinkage factors. The proposed estimation algorithms divide the target parameter vector into a number of groups and adaptively calculate one shrinkage factor for each group. GSE schemes improve the performance of the conventional least squares (LS) estimator in terms of the mean-squared error (MSE), while requiring a very modest increase in complexity. An MSE analysis is presented which indicates the lower bounds of the GSE schemes with different group sizes. We prove that our proposed schemes outperform the biased estimation with only one shrinkage factor and the best performance of GSE can be obtained with the maximum number of groups. Then, we consider an application of the proposed algorithms to single-carrier frequency-domain equalization (SC-FDE) of direct-sequence ultra-wideband (DS-UWB) systems, in which the structured channel estimation (SCE) algorithm and the frequency domain receiver employ the GSE. The simulation results show that the proposed algorithms significantly outperform the conventional unbiased estimator in the analyzed scenarios.

Distance Estimation for Radar Systems Using DS-UWB Signals

In this paper, we propose a distance estimation scheme for radar systems using direct sequence ultra wideband (DS-UWB) signals. The proposed distance estimation scheme averages out the noise by accumulating the correlator outputs of the radar, and thus, helps the radar to employ a short-length DS-UWB signal reducing the correlation processing time. Numerical results confirm that the proposed distance estimation scheme provides a better estimation performance and a reduced correlation processing time compared with those of the conventional DS-UWB radars. Keywords—Radar, DS-UWB, distance estimation, correlation accumulation.

DS-UWB indoor positioning system implementation based on FPGAs

In Ultra-Wideband (UWB) Local Positioning Systems (LPS), Inter-Symbol Interference (ISI), Multiple-Access Interference (MAI) and near-far effect are significant issues that can limit system performance. This paper presents a DS-UWB (Direct Sequence UWB) LPS based on FPGAs (Field-Programmable Gate Array) and on commercially available Radio-Frequency (RF) modules. In contrast to other DS-UWB LPS, which uses TDMA (Time Division Multiple Access) and base-band pulses with low-repetition frequency rates, the proposal uses QS-CDMA (Quasi-Synchronous Code Division Multiple Access) techniques with Loosely Synchronized (LS) spreading sequences. This allows to deal with ISI, MAI and near-far effect, as well as to use very large spreading sequences to increase the processing gain.

Performance of multiuser detectors based on EM-like method for ultra-wideband communications systems in multipath fading channel

An adaptive multiuser detector (MUD) is proposed for direct-sequence ultra-wideband (DS-UWB) multiple access communication systems to suppress both multiple access interference (MAI) and inter-symbol interference (ISI). In this contribution, considering the MUD from a combination viewpoint, we proposed a MUD based on electromagnetism-like (EM) method, which applied the concept of EM search to Hopfield neural network (EMHNN) for solving optimization problems. We analyze the performance of the EMHNN MUD in multipath fading channel, and compare it with the optimum detector and several suboptimum schemes such as conventional, decorrelator detector (DD), minimum-mean-squared error (MMSE) and HNN MUD. Simulation results will demonstrate that the proposed EMHNN MUD, which alleviates the detrimental effects of the MAI problem, can significantly improve the system performance.

상관값 누적 기반 DS-UWB 레이더 시스템

본 논문에서는 선박 접안 유도 시스템 등 정밀한 거리 추정을 요하는 안전항해운항, 선박트래픽관리 등의 분야에 알맞은 상관값 누적 기반 직접 수열 초광대역 (direct sequence ultra wideband: DS-UWB) 레이더 시스템을 제안한다. 제안하는 DS-UWB 레이더 시스템은 상관기 출력들을 누적하여 잡음을 평균냄으로써 잡음 성분의 영향을 줄이며, 기존의 DS-UWB 레이더 시스템들에 비해 더 빠른 시간에 신뢰성 있는 거리 추정을 수행한다. 모의실험 결과를 통해 제안하는 DS-UWB 레이더 시스템이 기존의 DS-UWB 레이더 시스템들에 비해 평균 상관 처리 시간이 더 짧을 뿐 아니라, 더 좋은 거리 추정 성능을 보임을 확인한다. In this paper, we propose a direct sequence ultra wideband (DS-UWB) radar system based on correlation accumulation in the fields of the ship traffic control and the safe ship operation including docking guidance systems. The proposed DS-UWB radar system averages out the noise by accumulating correlator outputs, and thus, provides a reliable distance estimation performance with a shorter estimation time compared with conventional DS-UWB radar systems. From numerical results, it is confirmed that the proposed DS-UWB radar system has not only a shorter average correlation processing time, but also a better distance estimation performance.

A Multiuser Detector Based on Artificial Bee Colony Algorithm for DS-UWB Systems

Artificial Bee Colony (ABC) algorithm is an optimization algorithm based on the intelligent behavior of honey bee swarm. The ABC algorithm was developed to solve optimizing numerical problems and revealed premising results in processing time and solution quality. In ABC, a colony of artificial bees search for rich artificial food sources; the optimizing numerical problems are converted to the problem of finding the best parameter which minimizes an objective function. Then, the artificial bees randomly discover a population of initial solutions and then iteratively improve them by employing the behavior: moving towards better solutions by means of a neighbor search mechanism while abandoning poor solutions. In this paper, an efficient multiuser detector based on a suboptimal code mapping multiuser detector and artificial bee colony algorithm (SCM-ABC-MUD) is proposed and implemented in direct-sequence ultra-wideband (DS-UWB) systems under the additive white Gaussian noise (AWGN) channel. The simulation results demonstrate that the BER and the near-far effect resistance performances of this proposed algorithm are quite close to those of the optimum multiuser detector (OMD) while its computational complexity is much lower than that of OMD. Furthermore, the BER performance of SCM-ABC-MUD is not sensitive to the number of active users and can obtain a large system capacity.

Swarm Intelligence and Its Applications

Swarm Intelligence and Its Applications