Impulse Radio Systems Research Articles

An Antijamming Method Based on Multichannel Singular Spectrum Analysis and Affinity Propagation for UWB Ranging Sensors

Ultra-wideband impulse radio system has received extensive attention due to their high resolution and poor interception possibility. But the specific electromagnetic threat posed by its complex work environment cannot be ignored. In all kinds of active jamming signals, smart noise jamming plays an important role in modern radar electronic warfare, and most traditional anti-jamming methods have less suppression effect. In this paper, the mechanism of smart noise jamming on the UWB ranging sensor is discussed first. On this basis, an anti-smart noise jamming method based on multichannel singular spectrum analysis and kurtosis characteristic is proposed. Experiments show that smart noise jamming is more threatening to the UWB system than other noise modulation jamming. And the improved algorithm proposed in this paper can suppress the jamming better. After the anti-jamming processing, the average detection probability can reach more than 95%. Meanwhile, the method is improved by adding the affinity propagation (AP) clustering algorithm to solve the underdetermined signal separation problem in the case of compound jamming. The advantage is that it does not have to estimate the number of signals first. Even if the SJR is -10 dB, the waveform similarity between the separation signal and the source signal can reach 0.7 or more.

Avoidance of narrowband interference in UWB wireless sensor device using square low technology

Impulse radio ultra-wideband system has been adopted in wireless sensor networks research due to its high performance in conditions of active influence of various noises and interferences, the presence of reflections, etc. In this paper, this system represents a transmitter based on the controller STM32 and a receiver implemented using blocks of analog and digital processing based on FPGA. This paper focuses on a realisation of an additional device that can provide the avoidance of narrowband interference in ultra-wideband wireless sensor network system to improve a value of bit error rate. For this purpose, a real device with using square low technique has been developed. According to the results of experiments this approach enables to improve a dependence of the bit error rate on the signal-to-noise ratio.

Wireless Control of Robotic Artificial Hand Using Myoelectric Signal Based on Wideband Human Body Communication

A Myoelectric hand is a robotic artificial hand controlled by myoelectric signals and driven by motors. The myoelectric signals are detected on the arm and sent to the motor controller by wire for driving the artificial hand. However, from the point of view of convenience, wireless connection between the myoelectric signal detector and the motor controller is strongly desired. In this paper, we developed a human body communication-based wireless transmitter and receiver for transmitting the myoelectric signals from the arm to the motor controller of the myoelectric hand. The transmitter and the receiver employed a wideband impulse radio system at about 10-50-MHz extremely weak radio power band and were implemented on a field programmable gate array, respectively. The feasibility of the wireless myoelectric hand was confirmed by a wireless transmission experiment of myoelectric signals and an operation experiment of the myoelectric hand. The wireless transmission experiment achieved a correlation coefficient as high as 0.999 between the transmitted and received myoelectric signals, and the operation experiment demonstrated a normal movement of the myoelectric hand controlled by the wireless myoelectric signals. This result should be the first realization example of wireless control of a robotic artificial hand based on human body communication technology.

Detection of breathing and heartrate using a simple vital radio system

Proposed is a detection technique utilised for the physiological monitoring of heart rate and breathing rate. This new methodology is better than the other conventional systems that utilise either continuous waves or impulse radio systems for detecting remote vital signs that either suffers from non-stationary clutters or anomalies in accuracy. Vital Radio which operates on wireless technology can sense and monitor the breathing rate and the heart beat rate of the concerned person. This device is designed in such a manner that it can be installed in the walls so that it can capture and maintain a health record of a person dwelling in smart homes. It has the prime advantage of revealing high level of accuracy in the detection of the required vital signs.

Pulse‐preserving characteristics and effective isotropically radiated power spectra of a new ultrawideband dielectric resonator antenna

A dielectric resonator antenna (DRA) with a full ground plane and an ultrawideband (UWB) operating bandwidth of 3.1–11.6 GHz is presented. Good return loss over a wide bandwidth is achieved, while the full ground plane directs most of the radiation into the upper hemisphere, significantly reducing undesirable radiation to the lower hemisphere. The measured results confirm a 10-dB return-loss bandwidth of 115%. Time-domain characteristics and effective isotropically radiated power (EIRP) spectra of the antenna are investigated for several types of UWB input pulses. The correlations between the input pulses and the radiated pulses in many directions were found to be excellent when the antenna is excited by a linearly chirped Gaussian pulse or a fifth-order Gaussian pulse. Nevertheless, EIRP spectrum calculations indicate that none of those pulses efficiently fill the Federal Communication Commission UWB mask when applied to this DRA. Hence, a third-order Rayleigh pulse is introduced and tuned to make efficient use of the allowed spectrum limits. Further improvement of pulse performance is investigated by varying antenna design parameters. This DRA is suitable for both impulse radio UWB systems and carrier-based UWB systems.

Dual-Band Skin-Adhesive Repeater Antenna for Continuous Body Signals Monitoring

We present a 35-mm diameter skin-adhesive antenna intended to operate as a gateway to relay the low power signals from a sensor implanted in the body to an external base station (BS). Such a device would be useful in the context of body area networks (BANs) for continuous body-signal monitoring. The proposed adhesive repeater is of very low profile, and it is designed for dual-band operation at the ISM band (2.4 GHz) and in the ultrawideband (UWB) spectrum (4–10.6 GHz) using a single excitation port. The ISM band is used for in-body communication with the implants and the UWB band for off-body burst communication with the BS. The antenna consists of three layers that grant it compactness and performance robustness. We assess the in-body link between the repeater and a custom-designed miniaturized implantable probe antenna. The study is performed in the frequency domain with results showing adequate input impedance matching ( s 11 ≤ −10 dB) and robustness to different body parts. We extend the analysis to time domain by transmitting a synthetized medical signal between the two antennas. In addition, we evaluate the feasibility of an off-body link for burst communication. Again, the results indicate very good performance by the repeater antenna both in terms of impedance matching ( s 11 ≤ −10 dB) and preservation of time signals (fidelity ≥ 75%), which is relevant in impulse radio systems. To the authors’ best knowledge, this is the first time this kind of dual-band adhesive antenna is being proposed for BANs, complete with performance tests using frequency- and time-domain figures-of-merit.

Improved quantisation mechanisms in impulse radio ultra wideband systems based on compressed sensing

To reduce the impact of quantisation noise during low-rate sampling of Impulse Radio Ultra-Wideband (IR-UWB) under compressed sensing framework and also considering the equal information carrying of compressed measurements and characteristics of Gaussian distribution, three modified quantisation mechanisms are designed in this study: overload uniform quantisation, non-uniform quantisation, and overload non-uniform quantisation. Also, the influencing elements of overload factor in overload mechanism are mentioned to obtain the optimisation scheme close to the optimal overload by fitting. The simulation results show that all the three modified mechanisms, especially the overload non-uniform quantisation mechanism, have wrought great improvement in performance when compared to the uniform quantisation. What's more, the performance of the overload uniform quantisation mechanism featured with low complexity is better than that of the non-uniform quantisation mechanism with high complexity, thus providing a practical quantisation method for the IR-UWB system under the compressed sensing framework.

Improved quantisation mechanisms in impulse radio ultra wideband systems based on compressed sensing

To reduce the impact of quantisation noise during low-rate sampling of Impulse Radio Ultra-Wideband (IR-UWB) under compressed sensing framework and also considering the equal information carrying of compressed measurements and characteristics of Gaussian distribution, three modified quantisation mechanisms are designed in this study: overload uniform quantisation, non-uniform quantisation, and overload non-uniform quantisation. Also, the influencing elements of overload factor in overload mechanism are mentioned to obtain the optimisation scheme close to the optimal overload by fitting. The simulation results show that all the three modified mechanisms, especially the overload non-uniform quantisation mechanism, have wrought great improvement in performance when compared to the uniform quantisation. What's more, the performance of the overload uniform quantisation mechanism featured with low complexity is better than that of the non-uniform quantisation mechanism with high complexity, thus providing a practical quantisation method for the IR-UWB system under the compressed sensing framework.

Energy Consumption Models For MISO-UWB and TR-MISO-UWB Systems

Abstractthis paper, an energy consumption model is developed and exploited to evaluate the electrical energy consumption of ultra-wideband impulse radio (UWB-IR) systems. We develop the energy consumption models and our comparative study, on the one hand, for a system based single-input singleoutput (SISO) configuration and a multiple-input single-output (MISO) and, on the other hand, for a time reversal TR-MISO configuration and for MISO alone configuration. We consider an indoor propagation environment based on the 802.15.4a channel model. The results show very different behaviors depending on the propagation conditions, the number of antennas used, or on the number of transmitted symbols. Using such a model, a radiofrequency designer can obtain significant inputs to optimally select an adequate configuration to design an adaptive energyaware UWB-IR system.

Use of UWB Impulse Radio Technology in In-Car Communications: Power Limits and Optimization

In-car wireless data communications systems require a short-range unlicensed radio communications technology that causes a very low level of interference in the other, already deployed radio links and networks, offers low and medium data rate, can reuse the already occupied radio-frequency (RF) bands, and assures low probability of message collisions. Ultrawide band (UWB) impulse radio employs RF pulses with very short duration to carry the information; consequently, it is an optimal candidate for the in-car wireless communications and intravehicular wireless sensor networks. Data rate and shape of RF carrier pulse determine the performance of a UWB radio link. To limit the interference caused, the maximum power radiated by an UWB device is restricted by the Federal Communications Commission (FCC) in the U.S. Introducing a new mathematical model and starting from the FCC regulations, analytical expressions for the calculation of FCC power limits are derived here. It is shown that the low- and high-rate UWB impulse radio systems are peak and average power limited, respectively. The relationship between the mathematical model and the parameters of an UWB carrier pulse used in a built UWB radio is established. The performances of RF carrier pulses known from the literature are evaluated and compared. All expressions derived are verified by measurements.

Joint Multiple Symbol Differential Detection and Channel Decoding for Noncoherent UWB Impulse Radio by Belief Propagation

This paper proposes a belief propagation (BP) message passing algorithm-based joint multiple symbol differential detection (MSDD) and channel decoding scheme for noncoherent differential ultra-wideband impulse radio (UWB-IR) systems. MSDD is an effective means to improving the performance of noncoherent differential UWB-IR systems. To optimize the overall detection and decoding performance, this paper proposes a novel soft-in soft-out (SISO) MSDD scheme for noncoherent differential UWB-IR. We first propose a new sampling mechanism for the noncoherent auto-correlation receiver to sample the received UWB-IR signal. The proposed sampling mechanism can exploit the dependences (imposed by the differential modulation) among data symbols throughout the whole packet. The signal probabilistic model has a hidden Markov chain structure. We use a factor graph to represent this hidden Markov chain. Then, we apply BP message passing algorithm on the factor graph to develop an SISO MSDD scheme, which is easy to integrate with SISO channel decoding to form a joint MSDD and channel decoding scheme. Performance results of bit error rate simulations and EXIT chart analyses indicate the performance advantages of our scheme over the previous MSDD scheme.

Performance evaluation of intra-vehicle wireless sensor network systems

Intra-vehicle wireless sensor networks (IVWSNs) enable sensor technologies to be integrated into vehicles and provide part-cost, assembly, and maintenance savings, as well as fuel efficiency through the elimination of wires. Ultra-wide band (UWB) communication is considered a competitive candidate for IVWSNs. Extensive analysis has been done for indoor and outdoor propagation, but the analysis of IVWSNs environments has rarely been studied. In this paper, the error-rate performance of UWB propagation for these IVWSNs is investigated and compared under different transmission schemes. And we also study the effects of some parameters on communication performance, such as the number of rake fingers and direct sequence spread factor of an impulse radio system, the cyclic prefix size of a single carrier block transmission with frequency domain equalisation system, and the delay line time of a transmitted reference pulse cluster autocorrelation receiver. Study results offer valuable insight for the realistic IVWSNs.

A Belief Propagation-Based Framework for Soft Multiple-Symbol Differential Detection

Soft noncoherent detection, which relies on calculating the \textit{a posteriori} probabilities (APPs) of the bits transmitted with no channel estimation, is imperative for achieving excellent detection performance in high-dimensional wireless communications. In this paper, a high-performance belief propagation (BP)-based soft multiple-symbol differential detection (MSDD) framework, dubbed BP-MSDD, is proposed with its illustrative application in differential space-time block-code (DSTBC)-aided ultra-wideband impulse radio (UWB-IR) systems. Firstly, we revisit the signal sampling with the aid of a trellis structure and decompose the trellis into multiple subtrellises. Furthermore, we derive an APP calculation algorithm, in which the forward-and-backward message passing mechanism of BP operates on the subtrellises. The proposed BP-MSDD is capable of significantly outperforming the conventional hard-decision MSDDs. However, the computational complexity of the BP-MSDD increases exponentially with the number of MSDD trellis states. To circumvent this excessive complexity for practical implementations, we reformulate the BP-MSDD, and additionally propose a Viterbi algorithm (VA)-based hard-decision MSDD (VA-HMSDD) and a VA-based soft-decision MSDD (VA-SMSDD). Moreover, both the proposed BP-MSDD and VA-SMSDD can be exploited in conjunction with soft channel decoding to obtain powerful iterative detection and decoding based receivers. Simulation results demonstrate the effectiveness of the proposed algorithms in DSTBC-aided UWB-IR systems.

Spectrum sensing in cognitive UWB impulse radio communication system

This paper emphasizes on the issue of spectrum sensing or awareness in cognitive UWB impulse radio (CUWB). Three spectrum sensing schemes are proposed in this paper: The first scheme is based on frame-level block processing, while the second scheme aims at real time chip-level processing. Analytical results show that scheme 1 outperforms scheme 2 in terms of the probability of detection and false-alarm, nevertheless, high detection delay may render the applicability of scheme 1 in CUWB. Employing the low duty cycle characteristics of the UWB IR signal, we propose a chip-level based sequential processing and diversity detection scheme (scheme 3). Through extensive simulations, the results demonstrate that scheme 3 has the best receiver operating characteristic (ROC) curve that can attain the design goal of high probability of detection and low probability of false alarm. Both analytical and numerical results in terms of the “mean detection delay” and the “average false alarm run length” have also been presented in this paper. It is verified that by employing the diversity combining, scheme 3 outperforms scheme 1 in that it requires much less detection time for spectrum sensing.

Multi-Human Detection Algorithm Based on an Impulse Radio Ultra-Wideband Radar System

In this paper, we propose a multi-human detection algorithm based on impulse radio ultra-wideband radar system. With our proposed algorithm, the multi-human detection can be performed by repeatedly performing clustering and detecting processes. More specifically, the system detects an effective peak of the first single cluster which is composed of peaks adjacent to each other and then repeat this process until effective peaks of clusters caused by multiple people are successfully detected sequentially. As our performance metrics, we take into account the performance analysis in terms of the error probability based on the results of the statistical analysis. More specifically, we first cross-verify that the empirical result theoretically follows the Log-normal distribution by comparing the theoretical and empirical results obtained through laboratory experiments. Then, we statistically analyze the received signals under the Log-normal distribution assumption. After that, this statistical result is adopted to the performance analysis of the error probability in terms of the total error probability. Note that the performance of our proposed algorithm is affected by the threshold value. Based on it, the optimal threshold is analyzed and we provide the sample guidelines for optimally adjusting the threshold value under given various environment factors. Finally, some selected experimental results are presented to show the validity of our proposed algorithm by comparing the performance between the proposed algorithm and the conventional algorithm.

Adaptive mitigation of narrowband interference in impulse radio UWB systems using time-hopping sequence design

The coexistence among different systems is a major problem in communications. Mutual interference between different systems should be analyzed and mitigated before their deployment. The paper focuses on two aspects that have an impact on the system performance. First, the coexistence analysis, i.e. evaluating the mutual interference. Second aspect is the coexistence techniques, i.e. appropriate system modifications that guarantee the simultaneous use of the spectrum by different technologies. In particular, the coexistence problem is analyzed between ultra-wide bandwidth (UWB) and narrow bandwidth (NB) systems emphasizing the role of spectrum sensing to identify and classify the NB interferers that mostly affect the performance of UWB system. A direct sequence (DS)-time hopping (TH) code design technique is used to mitigate the identified NB interference. Due to the severe effect of Narrowband Interference on UWB communications, we propose an UWB transceiver that utilizes spectrum-sensing techniques together with mitigation techniques. The proposed transceiver improves both the UWB and NB systems performance by adaptively reducing the mutual interference. Detection and avoidance method is used where spectrum is sensed every time duration to detect the NB interferer's frequency location and power avoiding it's effect by using the appropriate mitigation technique. Two scenarios are presented to identify, classify, and mitigate NB interferers.

무선광대역 시스템을 위한 블록 부호화 상관기 기반의 효율적인 수신기 설계 기법

Noncoherent receivers are favored for block-code-modulated ultrawideband impulse radio (UWB-IR) systems because of their low implementation complexity compared with coherent rake receivers. However, existing noncoherent schemes, such as transmitted reference (TR) systems and averaged differential receivers (ADR), suffer from performance degradation and energy efficiency loss. Codeword matching and signal aggregation (CMSA) is a low complexity noncoherent receiver for UWB-IR. As the frame/symbol duration is shortened to boost data rate, interframe interference (IFI) or intersymbol interference (ISI) occurs and degrades the detection performance of CMSA. In this paper, block coded correlator which consists of the delay components and the reference signal is proposed to improve the performance of the receiver. Simulation results show that the proposed system leads to the better performance compared to the conventional CMSA receiver.

A statistical analysis of multipath interference for impulse radio UWB systems

In this paper, we develop a statistical characterization of the multipath interference in an Impulse Radio (IR)-UWB system, considering the standardized IEEE 802.15.4a channel model. In such systems, the chip length has to be carefully tuned as all the propagation paths located beyond this limit can cause interframe/intersymbol interferences (IFI/ISI). Our approach aims at computing the probability density function (PDF) of the power of all multipath components with delays larger than the chip time, so as to prevent such interferences. Exact analytical expressions are derived first for the probability that the chip length falls into a particular cluster of the multipath propagation model and for the statistics of the number of paths spread over several contiguous clusters. A power delay profile (PDP) approximation is then used to evaluate the total interference power as the problem appears to be mathematically intractable. Using the proposed closed-form expressions, and assuming minimal prior information on the channel state, a rapid update of the chip time value is enabled so as to control the signal to interference plus noise ratio.

Soft-Input Soft-Output Non-Coherent Detection for Differential Space-Time Block Code Systems

A soft-input soft-output non-coherent detection algorithm is proposed for multi-antenna systems, where differential space-time block code is employed. The proposed algorithm aims to calculate a posteriori probabilities of the information bits by means of forward and backward message passing of the BCJR approach. The proposed algorithm can exploit the soft information effectively with the aid of the bidirectional message passing mechanism. In addition, the proposed algorithm can be exploited in conjunction with channel decoding to obtain an effective iterative detection and decoding approach. In view of low implementation complexity, the application of the proposed scheme is instantiated with the ultra-wideband impulse radio (UWB-IR) systems. Simulations show that the proposed approaches improve detection performance for UWB-IR systems.

Accurate heartbeat monitoring using ultra-wideband radar

We demonstrate an accurate remote measurement of heartbeats using an ultra-wideband radar system. Although most conventional systems use either continuous waves or impulse-radio systems for remote vital monitoring, continuous waves suffer from non-stationary clutters, while impulse-radio systems cannot detect heartbeats. Our ultra-wideband radar system has a moderate fractional bandwidth intermediate of these systems, resulting in both the suppression of clutters and high sensitivity in measuring accurate heart rates even in a dynamic environment. A simultaneous measurement of the vital signal of a participant employing the ultra-wideband radar and electrocardiography reveals the high accuracy of the radar system in measuring the heart rate varying over time.