Ultra-wideband Radio Systems Research Articles

Joint Power Allocation and Path Selection for Multi-Hop Noncoherent Decode and Forward UWB Communications

With the aim of extending the coverage and improving the performance of impulse radio ultra-wideband (UWB) systems, this paper focuses on developing a novel single differential encoded decode and forward (DF) non-cooperative relaying scheme (NCR). To favor simple receiver structures, differential noncoherent detection is employed which enables effective energy capture without any channel estimation. Putting emphasis on the general case of multi-hop relaying, we illustrate an original algorithm for the joint power allocation and path selection (JPAPS), minimizing an approximate expression of the overall bit error rate (BER). In particular, after deriving a closed-form power allocation strategy, the optimal path selection is reduced to a shortest path problem on a connected graph, which can be solved without any topology information with complexity O(N3), N being the number of available relays of the network. An approximate scheme is also presented, which reduces the complexity to O(N2) while showing a negligible performance loss, and for benchmarking purposes, an exhaustive-search based multi-hop DF cooperative strategy is derived. Simulation results for various network setups corroborate the effectiveness of the proposed low-complexity JPAPS algorithm, which favorably compares to existing AF and DF relaying methods.

An Enhanced 3D Positioning Scheme Exploiting Adaptive Pulse Selection for Indoor LOS Environments

In this paper, an enhanced 3D positioning scheme exploiting adaptive pulse selection is proposed for indoor environments. The proposed scheme is based on the time-of-arrival and angle-of-arrival estimation with multiple orthogonal pulses and uniform linear arrays antenna in impulse radio ultra-wideband systems. Since the ranging and the angle estimation performances are different from pulse shape and received SNR, the performance of 3D position estimation can be enhanced by adaptively selecting a pulse from received multiple pulses. Based on the orthogonal property, orthogonal pulses can be distinguished at the receiver and thus the optimal pulse is selected from the multiple pulses for ranging, azimuth and elevation angle estimation, respectively. Since the optimal pulse is selected for each estimation, enhanced performance for 3D position estimation can be achieved. The performance of the proposed scheme is evaluated by computer simulations over the IEEE 802.15.4a channel model. Results show that the performance of the proposed scheme is enhanced compared to that of the conventional scheme.

Two-Step Beveled UWB Printed Monopole Antenna with Band Notch

This paper presents a novel compact printed monopole ultra-wideband (UWB) antenna featured with the band notch. The proposed antenna consists of a two-step beveled radiant patch and a truncated ground plane, which can provide a good impedance matching from 3.1 GHz to 10.6 GHz. In order to generate the band-notched characteristics, two symmetrical slots are embedded along with the microstrip feeding line, resulting in a band notch from 5.05 GHz to 5.85 GHz. Accordingly, the mutual electromagnetic interference between the UWB and wireless local area network (WLAN) radio communication systems can be eliminated. In addition, it is shown how the slots integrated on the ground plane improve the radiation patterns. The experimental measurements are found to be in good agreement with the numerical simulations.

PRINTED EGG CURVED SLOT ANTENNAS FOR WIDEBAND APPLICATIONS

This paper presents a novel design of an egg curve based wide-slot antenna for various wideband applications. The proposed printed antenna consists of an egg curved slot with a similar tuning stub. The egg curve is obtained by introducing an egg shaping parameter into standard elliptic curve equation. The efiect on the impedance bandwidth through the variations in antenna design parameters has been investigated and analysed in detail. To validate the theoretical design, various egg curved slot antennas were designed, fabricated and measured. Good agreement between the simulated results and the measured ones is observed. An empirical formula is also proposed to approximately determine the frequency corresponding to the lower edge of i10dB operating bandwidth. The results demonstrate that the proposed egg curved slot antenna (ECSA) can obtain a measured bandwidth (BW) of 164.46% (1.95{20.0GHz) for jS11j • i10dB. A stable realised gain of about 4.1{5.1dBi with consistent radiation patterns are measured over more than the entire ultrawideband (UWB) bandwidth (3.1{10.6GHz) which makes it a suitable candidate for wideband and UWB wireless system applications.

The Fractal Characteristics of Signals in IR-UWB Communication System

In this paper the fractal characteristics of the received multipath signals of impulse radio ultra-wideband communication system are analyzed and proved using over-value function. The scale-invaria...

Optimal receiver antenna location in indoor environment using dynamic differential evolution and genetic algorithm

Abstract Using the impulse responses of these multipath channels, the bit error rate (BER) performance for binary pulse amplitude modulation impulse radio ultra-wideband communication system is calculated. The optimization location of receiving antenna is investigated by dynamic differential evolution (DDE) and genetic algorithm (GA) to minimize the outage probability. Numerical results show that the performance for reducing BER and outage probability by DDE algorithm is better than that by GA.

Active UWB Reflector for RFID and Wireless Sensor Networks

In this paper, we present an active ultra-wideband (UWB) reflector for radio frequency identification (RFID) and wireless sensor applications. The tag is composed of a receiver UWB antenna connected to a broadband amplifier. Its output is connected to a cross-polarized transmit antenna. In order to increase the battery lifetime, an UHF link is used to wake up the microcontroller. It modulates the radar cross section of the tag by turning the amplifier bias on and off. The amplitude of the reflected UWB pulse sent by the UWB reader is modulated as a result. The basic theory of operation of ultra-wideband radio identification systems is explained in this paper. A proof of concept using commercial components and experimental results obtained with an ultra-wideband radar are presented.

Low-complexity synchronization algorithms for orthogonally modulated IR-UWB systems

Timing synchronization is a major issue for any communication system since it is essential to ensure its stable operation and reliable performance. In this paper, we compare two low-complexity synchronization algorithms for impulse radio ultra-wideband (IR-UWB) system, employing orthogonal pulse shape modulation (PSM). The two widely adopted modulation schemes for IR-UWB systems are binary pulse amplitude modulation and binary pulse position modulation. However, the possibility of generating orthogonal UWB pulses in recent years has motivated the use of orthogonal PSM which is particularly attractive as high-order modulation and also due to its possible robustness against ISI, and therefore is the focus of this paper. Relying on the unique signal format, the first algorithm applies simple overlap-add operation followed by energy detection to achieve synchronization. This approach is semi non-data-aided (NDA) because a part of the signal is specifically reserved to help enable synchronization. The other algorithm, on the other hand, exploits the discriminating nature of well-designed polarity codes and employs a series of code word matching and averaging operations to achieve synchronization. This approach is full NDA as there is no need to interrupt the data transmission. Based on the judicious change in the phase of transmitted signal applied for synchronization purposes, the second algorithm can also be used to extract synchronized aggregate templates. These templates are then used in demodulation, resulting in a low-complexity non-coherent alternative to complex Rake receivers. The two compared timing algorithms rely on simple overlap-add operations and thus remain operational under practical UWB settings. Simulation results are provided to demonstrate the efficient performance of proposed timing estimators.

Semi-Passive Time-Domain UWB RFID System

This paper presents a semi-passive time-domain ultra-wideband (UWB) radio identification system. The reader consists of a commercial, low-cost, and integrated impulse-radio radar. The tag is composed of a UWB antenna loaded with a transmission line, which is in turn terminated with a PIN diode. The tag answers to the interrogator by backscattering, modulating the amplitude of the time-domain reflected pulses sent by the radar. A 2.4-GHz downlink channel is used to wake up the tag, in order to increase the lifetime of the battery. The wake-up circuit is based on a diode rectifier and the internal comparator within the tag chip (a microcontroller) without needing additional active devices. Experimental results obtained with a proof-of-concept tag show that read-ranges up to 8.5 m can be achieved.

Performance Analysis of Rake Receivers in IR–UWB System

Suppression of interference in time domain equalizers is attempted for high data rate impulse radio (IR) ultra wideband communication system. The narrow band systems may cause interference with UWB devices as it is having very low transmission power and the large bandwidth. SRAKE receiver improves system performance by equalizing signals from different paths. This enables the use of SRAKE receiver techniques in IR UWB systems A semi analytical approach is used to investigate the BER performance of SRAKE receiver on IEEE 802.15.3a UWB channel models. Study on non-line of sight indoor channel models (both CM3 and CM4) illustrates that bit error rate performance of SRake receiver with NBI performs better than that of Rake receiver without NBI

Spectrum Sensing Time Optimization Algorithm for Spectrum Efficiency Maximization in the Low-power Cognitive Radio Ultra Wideband System

For energy detection in a cognitive radio (CR) system, the spectrum sensing time required to successfully detect a primary user (PU) is inversely proportional to the PU's signal strength. When the PU operates in low-SNR regime, the effective transmission time of the CR system with a fixed transmission window can be extremely short for the CR system to fully utilize the spectrum. This paper presents a sensing time optimization algorithm aiming at maximizing the spectral efficiency of the Ultra Wideband (UWB) based CR system by finding the optimal tradeoff between the length of the sensing window and the detection probability in low-SNR regime. Compared with the time fixed sensing methods, the optimization algorithm can produce a significantly longer transmission time for the UWB based CR system to effectively utilize the detected spectrum band while guaranteeing protection to the PUs.

Compact LTCC-based Multilayer Ultrawideband(UWB) Bandpass Filter Composed of Broadside-Coupled E-shaped Electrodes

Ultra-wideband (UWB) wireless communication systems, utilizing a huge frequency range from 3.1 ㎓ to 10.6 ㎓, are one of the key technologies to meet tremendous demands for up-coming high-speed wireless data communications. The hardware of such systems requires to be made very compact and highly functional. In this paper, research history of our planar-type UWB band-pass filters composed of capacitively couped E-shaped electrodes is outlined first. After that, a super-compact multi-layered UWB bandpass filter is newly developed by using the E-shaped electrode architecture. The designed filter, with overall dimensions of 5.0 x 5.0 x 0.95 mm3, has a UWB passband from 3.3 ㎓ to 10.7 ㎓ in simulation (a fractional bandwidth of 106 %) and from 3.5 ㎓ to 10.7 ㎓ in experiment (a fractional bandwidth of 100%). In addition, the filter has attractive transmission zeros just below and above the passband, whose creation mechanism is studied theoretically. Also, useful design procedure is introduced for this filter.

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A joint timing synchronization, channel estimation, and SFD detection for IR-UWB systems

This paper proposes a joint timing synchronization, channel estimation, and data detection for the impulse radio ultrawideband systems. The proposed timing synchronizer consists of coarse and fine timing estimation. The synchronizer discovers synchronization points in two stages and performs adaptive threshold based on the maximum pulse averaging and maximum (MAX-PA) method for more precise synchronization. Then, iterative channel estimation is performed based on the discovered synchronization points, and data are detected using the selective rake (S-RAKE) detector employing maximal ratio combining. The proposed synchronizer produces two signals-the start signal for channel estimation and the start signal for start frame delimiter (SFD) detection that detects the packet synchronization signal. With the proposed synchronization, channel estimation, and SFD detection, an S-RAKE receiver with binary pulse position modulation binary phase-shift keying modulation was constructed. In addition, an IEEE 802.15.4a channel model was used for performance comparison. The comparison results show that the constructed receiver yields high performance close to perfect synchronization.

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.

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).

Joint IR-UWB Power Spectral Lines and Interference Suppression Based on Coded Auxiliary Independent Signaling in Presence of Pulse Attenuation and Timing Jitter

This paper deals with spectral shaping problem in impulse radio ultra-wideband systems based on coded auxiliary independent signaling (AIS), as a modified version of transmitted-reference approach. In this manuscript, the main contribution includes a unified theoretical framework for spectral analysis which is, not only able to address all effective parameters in the emergence of spectral lines and coexistence issues, but also provides a convex optimization based method. This can produce AIS-aided signals using random process characteristics as optimization variables. In particular, the specific novelty insights of this paper are as follows: (i) to propose a new signal model, where each transmitted symbol is represented by a preamble AIS pulse followed by a set of transmitted data pulses that are synthesized in accordance with a codeword design and within this context, the preamble signal is designed to eliminate spectral lines via an adaptive monitoring of data-stream statistics as the optimal policy; (ii) to exploit the proposed spectral optimization strategies to maximize spectral flexibility.

Ultra-wideband outdoor communication characteristics with and without traffic

The BER performance for ultra-wideband (UWB) outdoor communication in LOS and NLOS environments with and without traffic is investigated. We obtain the impulse responses of the UWB outdoor environment by both 2.5D SBR-Image method and inverse Fourier transform techniques. The 2.5D SBR-Image method is first considered for two-dimensional environment simulated without heights of obstacles by ray tubes. Then, heights of the obstacles are taken into consideration between the transmitters and receivers. If the height of ray is lower than that of obstacles, the ray is neglected for the receivers. This effectively reduces the simulating time. By using the impulse response of multipath channels, the BER performance for binary pulse amplitude modulation communications over the radio UWB system is evaluated. We have performed computer simulations in LOS and NLOS environments with and without traffic in dense building areas. Numerical results have shown that the multipath effect caused by moving vehicles in the outdoor LOS and NLOS environments has a great impact on BER performance. Rake receivers are used to improve the outage probability. The relationship between traffic and BER performance is investigated; meanwhile, the characteristics of LOS and NLOS outdoor UWB environments are analyzed. Our investigation results can help improve planning and design of the UWB system.

Investigation of blind detection mechanism for chaotic UWB system based on generalized negentrogy

A non-coherent blind detection method based on the generalized negative entropy mechanism for chaotic ultra-wideband system is proposed in this paper. In the case without knowing the transmission channel information, the chaotic impulse signals can be detected. The proposed method can overcome the practical application problem existing in the direct chaotic communication (DCC) scheme for impulse radio ultra-wideband (IR-UWB) communication system. Also, this method can overcome the complicated and unknown multipath channel effect. Analysis of simulation results show that the proposed approach has a good separating and detection performance in the case without the channel information. A new way for the noncoherent blind detection of chaotic UWB system under non-ideal unknown channel is established.

Performance of constrained blind adaptive DS-CDMA UWB multiuser detector in multipath channel with IEEE 802.11a interference

Ultra wideband wireless systems are supposed to coexist with other spectrally overlapping narrowband wireless systems especially IEEE 802.11a wireless LAN. Presence of narrowband interference degrades the performance of UWB. In this paper we study bit error probability performance of the constrained blind DS-CDMA UWB multi-user detection algorithms in the presence of IEEE 802.11a OFDM narrowband interference. The constrained blind adaptive algorithm is implemented using both least mean square and recursive least square algorithm and the bit error probability performance is compared with Rake matched filter receiver. The constrained blind receiver does not require spreading code knowledge of all users other than that of the user of interest. Simulation results show that the constrained blind detector cancels IEEE 802.11a interference significantly in comparison with that of the Rake matched filter in the UWB multipath channel.