Impulse Radio Research Articles

Design and Performance Evaluation of IR-UWB Tapered Slot Antenna for Optimum Impulse Radio Radiation

In this paper, design and performance evaluation of Tapered Slot Antenna for IR-UWB which propagates impulse radio is performed. TSA which has directional characteristic in UWB band should have low radiation loss and minimized impulse radiation distortion. In order to achieve these objectives, the paper designed wide band Impedance transformer and microstrip-slotline transit region structured TSA feeder line. By using the fabricated TSA, the radiation pattern was measured in the radio anechoic chamber. Pulse fidelity and distortion equation was induced to evaluate time domain characteristics according to the impulse radiation. Pulse fidelity of Impulse radiation show favorable results more than 93% within beam width.

Indoor Positioning Using UWB-IR Signals in the Presence of Dense Multipath with Path Overlapping

This paper presents a method for positioning using ultra-wideband impulse radio (UWB-IR) signals that is robust in indoor environments characterized by dense multipath channel with path overlapping. Path overlapping effects arising from multipath in dense cluttered environments decrease the direct path resolution in time domain, and hence induce time-of-arrival (TOA) and angle-of-arrival (AOA) based positioning inaccuracy. To mitigate this problem, system design that is capable of resolving the closely-spaced multipath at low cost is of value. Our method yields the least-squares estimation of joint TOA and AOA with low computational cost. It is based on the spectral observation of beam forming, in which the path overlapping effect is mitigated using multipath-aided acquisition. The computational cost is reduced using in-band power spectrum and accurate initial estimations. The performance is verified both in IEEE 802.15.4a CM3 channel model and in a real environment. Simulation results in CM3 channel model show that the TOA and AOA estimation improvements on average are 2.4cm and 13.1° in the dense multipath scenario. Measurement in an indoor open hall environment shows that the AOA error decreases from 10.6° to 7.2°, and the TOA error decreases from 2.1cm to 1.9cm when the path overlapping effects are mitigated in the range of 21m.

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Reconfigurable ultra-wideband transmitter for generation of arbitrary impulse shapes and modulation schemes

Abstract. In this paper a reconfigurable ultra-wideband (UWB) impulse radio (IR) transmitter is presented. The IR signal is synthesized at an intermediate frequency (IF) by employing a multi-Nyquist digital-to-analog converter (DAC) with 12 bit resolution and an update rate of 2.3 GHz. Digital generation of signals in a field programmable gate array (FPGA) guarantees very high flexibility of the reconfigurable design. For upconversion to the radio frequency (RF) band, a first order bandpass (BP) sampling concept and an alternative conventional concept with mixer stages, have been realized. The system enables to generate signals with arbitrary modulation schemes and techniques at an external host personal computer (PC) employing MATLAB. Different measurements using a digitizing oscilloscope have been conducted to demonstrate the performance of the transmitter.

高速脉冲超宽带系统和芯片设计

Impulse radio (IR) ultra-wideband (UWB) wireless communication system has the advantages of low power consumption and low complexity. However, its transmission rate is usually limited. This paper proposes a high-speed IR-UWB system scheme. By using high sampling rate, low resolution quantization, and digital processing, the proposed scheme achieves more than 100 Mbps wireless transmission rate with reasonable power consumption and complexity. The system scheme, core algorithms, key implementations in the chip design, and simulation results are given in the paper. As a core algorithm, a joint synchronization and channel estimation (JSCE) algorithm is proposed. The JSCE algorithm conducts synchronization and channel estimation at the same time. It has the advantage of low complexity and is feasible to real-time implementation. The implementation issues in the chip design, including the digital baseband chip structure, the state transform of the receiver, and the implementation of the JSCE algorithm are introduced. Based on the proposed system scheme, a digital baseband chip is designed and fabricated. The core power consumption of the chip is less than 100 mW. An experimental system is also implemented which uses the baseband chip as a core processor. The system is capable of real-time high de nition video transmission. Experimental results on the experimental system validate the proposed system scheme.

Location-Aware UWB Communication with Generalized Energy Detection Receivers

Future wireless networks based on Ultra-Wideband (UWB) will offer localization capabilities with centimeter accuracy. We propose to use this inherently obtainable location knowledge to adapt the transceiver to the multipath channel conditions. This saves overhead for channel estimation and dissemination and enables low cost, low complexity and low power data transmission. In particular, we study the location-aware adaptation of generalized energy detection receivers for UWB impulse radio communication with binary pulse position modulation. Conventionally, these receivers are very vulnerable to narrowband interference. Therefore, we derive transmitter and receiver optimization schemes based on the Signal-to-Interference-plus-Noise-Ratio (SINR): First, we present the SINR optimization based on full channel knowledge. The location knowledge is then incorporated by means of a statistical channel model, which depends on the position of the nodes. Performance evaluation based on a simple channel model is used to give insight about the fundamental behavior of the derived optimization schemes. Moreover, an extensive measurement campaign in a rich scattering environment proves that location information can improve the data transmission and helps to successfully suppress narrowband interference. Performance gains of 2 to 5 dB compared to conventional energy detection can be obtained.

Photonic ultrawideband impulse radio generation and modulation over a fiber link using a phase modulator and a delay interferometer

We propose and experimentally demonstrate a simple and flexible photonic scheme for generation and modulation of ultrawideband (UWB) using a phase modulator and a fiber delay interferometer (DI)-based multichannel frequency discrimination. By introducing a Gaussian signal to the phase modulator, the UWB polarity-switchable doublet pulses can be achieved by combining the pair of UWB monocycle pulses with inverted polarities at the DI outputs under proper time delay. Furthermore, the pulse shape modulation, pulse position modulation, and on-off keying can be performed by coding the electrical data patterns and adjusting the time delay between the two monocycle pulses. Only a laser source introduced in the architecture guarantees the excellent dispersion tolerance over 75 km optical fiber link for UWB pulse sequence, which has potential application in future high-speed UWB impulse radio over optical fiber access networks.

A Hybrid TOA-Fingerprinting Based Localization of Mobile Nodes Using UWB Signaling for Non Line-Of-Sight Conditions

Recently, Impulse Radio Ultra Wideband (IR-UWB) signaling has become popular for providing precise location accuracy for mobile and wireless sensor node localization in the indoor environment due to its large bandwidth and high time resolution while providing ultra-high transmission capacity. However, the Non-line-of-sight (NLOS) error mitigation has considerable importance in localization of wireless nodes. In order to mitigate NLOS errors in indoor localization this paper proposes and investigates a novel approach which creates a hybrid combination of channel impulse response (CIR)-based fingerprinting (FP) positioning and an iterative Time of Arrival (TOA) real time positioning method using Ultra Wideband (UWB) signaling. Besides, to reduce the calculation complexities in FP method, this paper also introduces a unique idea for the arrangement of reference nodes (or tags) to create a fingerprinting database. The simulation results confirm that the proposed hybrid method yields better positioning accuracies and is much more robust in NLOS error mitigation than TOA only and FP only and a conventional iterative positioning method.

A Non-Data-Aided Rapid Synchronization Method for UWB Impulse Radio

Timing synchronization is a critical as well a challenging issue in ultra-wideband impulse radio (UWB-IR) due to their particular transmission characteristics. This letter proposes a rapid synchronization algorithm which can achieve frame-level synchronization in non-data-aided (NDA) mode. Relying on a unique transmit signal pattern based on orthogonal pulses and asymmetric modulation, synchronization is achieved without the need to search among thousands of bins, thereby significantly reducing the mean synchronization time. Simulation results prove that the proposed synchronization algorithm is efficient in single as well as in multi-user scenarios.

Pedestrian Tracking Solution Combining an Impulse Radio Handset Transmitter with an Ankle-Mounted Inertial Measurement Unit

We address the indoor tracking problem by combining an Impulse Radio-Ultra-Wideband handset with an ankle-mounted Inertial Measurement Unit embedding an accelerometer and a gyroscope. The latter unit makes possible the detection of the stance phases to overcome velocity drifts. Regarding radiolocation, a time-of-arrival estimator adapted to energy-based receivers is applied to mitigate the effects of dense multipath profiles. A novel quality factor associated with this estimator is also provided as a function of the received signal-to-noise ratio, enabling us to identify outliers corresponding to obstructed radio links and to scale the covariance matrix of radiolocation measurements. Finally, both radio and inertial subsystems are loosely-coupled into one single navigation solution relying on a specific extended Kalman filter. In the proposed fusion strategy, processed inertial data control the filter state prediction whereas Combined Time Differences Of Arrival are formed as input observations. These combinations offer low computational complexity as well as a unique filter structure over time, even after removing outliers. Experimental results obtained in a representatively harsh indoor environment emphasize the complementarity of the two technologies and the relevance of the chosen fusion method while operating with low-cost, noncollocated, asynchronous, and heterogeneous sensors.

Expurgated PPM Using Symmetric Balanced Incomplete Block Designs

In this letter, we propose a new pulse position modulation (PPM) scheme, called expurgated PPM (EPPM), for application in peak power limited communication systems, such as impulse radio (IR) ultra wide band (UWB) systems and free space optical (FSO) communications. Using the proposed scheme, the constellation size and the bit-rate can be increased significantly in these systems. The symbols are obtained using symmetric balanced incomplete block designs (BIBD), forming a set of pair-wise equidistant symbols. The performance of Q-ary EPPM is better than any Q-ary pulse position-based modulation scheme with the same symbol length. Since the code is cyclic, the receiver for EPPM is simpler compared to multipulse PPM (MPPM).

Si/Ge Avalanche Photodiodes-Based Electrical Comb-Line Generators and Photoreceivers for Very-Fast Impulse Radio Wireless Linking

We demonstrate the novel operation of a Si/Ge-based avalanche photodiode (APD) for the direct generation of ultra-wideband (UWB) frequency comb lines for impulse radio (IR) wireless communication. By applying a dc bias (Vbias) over the breakdown voltage (Vbr) of the APD, the device can exhibit a significant resonant frequency without any optical signal illumination, and function as an impact ionization avalanche transit time diode-based oscillator. Under an additional electrical intermediate frequency (IF) injection, several frequency comb lines, with a spacing equal to the IF frequency, can be derived from the second harmonic of the oscillating frequency. By mixing the output pulse train from the APD-based UWB generator with the data signal from another Si/Ge APD (on the same chip) operated in the linear mode (Vbias <; Vbr), which can perform high-sensitivity optical data detection, error-free IR wireless-linking with data rate as high as 3.0 Gbit/s has been successfully achieved.

Gigabit/s Photonic Generation, Modulation, and Transmission for a Reconfigurable Impulse Radio UWB Over Fiber System

We propose and demonstrate a flexible and high-speed impulse radio ultrawideband (IR-UWB) over fiber system using various modulation schemes. Two kinds of fully Federal Communication Commission (FCC) compliant UWB pulses are produced, which is based on the incoherent summation of multiple monocycle pulses with inverse polarities, proper time delays, and different weights. Theoretically, their spectral power efficiency can achieve 33.9% and 47.4%, respectively, which is much higher than that of the conventional monocycle and doublet pulses. A good agreement between the theoretical and experimental results for the generation of designed UWB pulses is also observed. Moreover, electrically reconfigurable multiple modulation formats such as on-off keying (OOK) modulation, binary phase shift keying (BPSK) modulation, pulse shape modulation (PSM), and pulse position modulation (PPM) are implemented experimentally. Furthermore, the UWB signals with OOK, BPSK, and PPM are transmitted over a combined wired (single-mode fiber) and wireless link. The transmission performance of the newly generated UWB pulses is then evaluated by electrical spectra, eye diagrams, and bit-error-rate measurements. For all the modulation formats, a forward-error-correction (FEC)-limit error-free operation is obtained, and the power penalties of transmission are less than 1 dB.

Cross-layer architecture of impulse-based ultra wideband to support the integration of Radio Frequency Identification and wireless sensor network infrastructures

Many research studies have recently proposed the use of Impulse Radio based ultra-wideband technology for passive and active radio frequency identification systems as well as for wireless sensor networks because of its numerous advantages. To harness these advantages at the physical-layer level of design, cross-layer architecture can be used to integrate different wireless short-range requirements into a smart wireless-tagged architecture. Adaptive transmission algorithm has been studied to show the trade-off flexibility between different specific quality of service requirements and transmission rate parameters at the physical-layer level in varied distance scenarios. This type of dynamic optimization and reconfiguration leads to the cross-layer design proposal introduced in this paper. The results of the theoretical and simulated analyses as well as the dedicated experimental design and implementations prove the validity of the proposed architecture.

IFI and ISI Premitigation for Block-Code-Modulated Noncoherent UWB Impulse Radio: A Code Optimization Approach

Codeword matching and signal aggregation (CMSA) is a recently proposed low-complexity noncoherent receiver for block-code-modulated ultrawideband impulse radio (UWB-IR) systems. 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, an effective IFI/ISI premitigation scheme is proposed for CMSA through a code optimization approach. By employing a tailored interference model that highlights the codeword properties, the system performance in the presence of moderate IFI/ISI is evaluated, and the average collected channel gain is introduced as the metric for code optimization. With the primary focus on binary modulation, the following two IFI/ISI-robust code properties are generalized: 1) shifted orthogonality and 2) shifted repetition. Based on these properties, the optimal code is constructed. It is observed that, when the optimal code occurs, the leaked signal energy or the interference can partially be used to enhance the detection performance of CMSA in the presence of IFI/ISI. Unlike most of the existing IFI/ISI mitigation schemes for noncoherent UWB-IR, which mainly focus on signal processing after the nonlinear detector, the optimized code is exploited to aggregate the leaked signal energy, along with the linear predetection operation already involved in the CMSA receiver. Both analysis and simulation show that a distinct performance improvement is achieved.

Synchronization for IR-UWB System Using a Switching Phase Detector-Based Impulse Phase-Locked Loop

Conventional synchronization algorithms for impulse radio require high-speed sampling and a precise local clock. Here, a phase-locked loop (PLL) scheme is introduced to acquire and track periodical impulses. The proposed impulse PLL (iPLL) is analyzed under an ideal Gaussian noise channel and multipath environment. The timing synchronization can be recovered directly from the locked frequency and phase. To make full use of the high harmonics of the received impulses efficiently in synchronization, the switching phase detector is applied in iPLL. It is capable of obtaining higher loop gain without a rise in timing errors. In different environments, simulations verify our analysis and show about one-tenth of the root mean square errors of conventional impulse synchronizations. The developed iPLL prototype applied in a high-speed ultra-wideband transceiver shows its feasibility, low complexity, and high precision.

Synchronization for IR-UWB System Using a Switching Phase Detector-Based Impulse Phase-Locked Loop

Conventional synchronization algorithms for impulse radio require high-speed sampling and a precise local clock. Here, a phase-locked loop (PLL) scheme is introduced to acquire and track periodical impulses. The proposed impulse PLL (iPLL) is analyzed under an ideal Gaussian noise channel and multipath environment. The timing synchronization can be recovered directly from the locked frequency and phase. To make full use of the high harmonics of the received impulses efficiently in synchronization, the switching phase detector is applied in iPLL. It is capable of obtaining higher loop gain without a rise in timing errors. In different environments, simulations verify our analysis and show about one-tenth of the root mean square errors of conventional impulse synchronizations. The developed iPLL prototype applied in a high-speed ultra-wideband transceiver shows its feasibility, low complexity, and high precision.

On the performance of a rapid synchronization algorithm for IR‐UWB receivers

ABSTRACTBecause of the very low signal duty cycles, synchronization is the most critical issue in ultra wideband (UWB) impulse radio (IR) systems. Some effective synchronization schemes like a symbol‐differential (SD) IR‐UWB receiver have been proposed to synchronize received signals rapidly. Yet, SD IR‐UWB receiver is unsuitable for operation in multi‐user environment because of multiple access interference (MAI). By taking advantage of frame‐differential IR‐UWB receivers, we propose a parallel frame‐differential (PFD) IR‐UWB receiver to do so. Our proposed PFD IR‐UWB receiver manifests better immunity against message passing interface and MAI than the SD IR‐UWB. Based on this PFD IR‐UWB receiver, uncertain (search) regions are limited to one frame duration without any symbol‐level synchronization process. Performance of PFD and SD receivers are compared by computer simulations, showing that the proposed PFD receiver not only achieves significant bit error rate performance but also better and more robust results than the SD receiver in this literature. Copyright © 2012 John Wiley &amp; Sons, Ltd.

IR-UWB 시스템 응용을 위한 시간- 및 주파수-영역에서의 앤티포달 비발디 안테나 성능 평가

본 논문에서는 IR-UWB(Impulse Radio Ultra Wideband) 시스템 응용을 위한 앤티포달 비발디 안테나를 설계하고, 시간 및 주파수 영역에서 나노 초 단위의 초광대역 임펄스 신호 전송을 위한 IR-UWB 안테나 성능 평가를 수행하였다. 설계된 앤티포달 비발디 안테나는 저가 생산이 가능한 두께 1.6 mm, 유전율 <TEX>${\epsilon}_r=4.7$</TEX>, <TEX>$tan{\delta}=0.002$</TEX>인 FR-4 기판을 이용하여 제작하였다. 제작된 안테나는 무반사실에서 주파수 영역 파라메타인 반사 손실, Far 필드방사 패턴을 측정하였다. 또한, 시간 영역에서 나노 초 단위의 임펄스 신호 전송에 따른 펄스 충실도 분석을 수행하여 UWB 대역에서 안정적으로 초광대역 신호 전송이 가능함을 증명하였다. 본 논문에서 설계/제작된 앤티포달 비발디 안테나는 낮은 왜곡과 양호한 방사 특성을 갖고, 나노 초 단위의 초광대역 임펄스를 방사 또는 수신할 수 있다. In this paper, we designed the antipodal vivaldi antenna for IR-UWB systems application and evaluated IR-UWB antenna performance for the ultra wideband impulse signal transmission in the time- and frequency-domain. The designed antipodal vivaldi antenna was fabricated using FR-4 substrate which thickness 1.6 mm, dielectric constant <TEX>${\epsilon}_r=4.7$</TEX> and <TEX>$tan{\delta}=0.002$</TEX>. We measured the return loss, far filed radiation pattern at the anechoic chamber in the frequency-domain. We also performed the pulse fidelity analysis in the time-domain using nano-second impulse signal transmission and demonstrated the feasibility of ultra wideband signal stable transmission in the UWB band. The designed and fabricated antipodal vivaldi antenna could be emitting and receiving the IR-UWB signal while preserving low pulse distortion and good radiation pattern in time- and frequency-domain.

A novel low complexity data demodulation algorithm for pulse position modulation

In this paper, a low complexity data demodulation algorithm is proposed that requires time of arrival information of the received signal exclusively. As an application example, the algorithm is applied to an ultra-wideband impulse radio communication system with pulse position modulation. The algorithm is insensitive to a common time delay for all pulses, that means, it does not require an accurate synchronization between the transmitter and the receiver. For the performance estimation, only a symbol synchronization is assumed, i.e., that there is a priori knowledge which pulse marks the beginning of a received data symbol. The performance of the proposed algorithm is evaluated for straightforward time of arrivals estimators, such as a maximum detector or a threshold detector. It is shown that the proposed algorithm outperforms a least squares algorithm in all considered scenarios. In particular, an increased robustness against additive white Gaussian noise, impulse like noise, and multiuser interference is demonstrated as well as an improved performance for multipath propagation channels.