This paper reports on a study of the interference effects from 2 types of ultra wideband (UWB) sources on a QPSK transmission system by simulation. The culprit UWB sources were: multi-band orthogonal frequency-division multiple-access (MB-OFDM) and direct-sequence UWB (DS-UWB), which were modeled on the proposal specifications in the IEEE 802.15.3a to standardize high-speed wireless personal area networks. Average bit error rate (BER) degradation of the victim system was evaluated under in-band interference from the UWB signals. The proposed modified equivalent baseband system was employed in the simulation in order to reduce the simulation costs. Interference effects from the UWB sources were also examined under a Rayleigh fading channel.

UWB pulse radars that offer target shape estimation are promising as imaging techniques for household or rescue robots. We have already proposed an efficient algorithm for a shape estimation method SEABED which is a fast algorithm based on a reversible transform. SEABED extracts quasi wavefronts from received signals with the filter that matches the transmitted waveform. However, the scattered waveform is, in general, different from the transmitted one depending on the shape of targets. This difference causes estimation errors in SEABED. In this paper, we propose an accurate algorithm for a polygonal-target based on scattered waveform estimation. The proposed method is presented first, followed by results of numerical simulations and experiments that show the efficiency of the proposed method.

In this letter, we propose a symbol repetition technique combined with parallel channel encoding for multiband orthogonal frequency division multiplexing systems with ultra wideband channels. It can resolve timing asynchronous cochannel interference from another simultaneously operating piconet. Our simulation results demonstrate that the proposed scheme can effectively reduce the effect of the interference.

Coexisting with many concurrent narrowband services, the performance of UWB systems will be affected considerably by them. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals will interfere with UWB systems significantly. In this paper, a novel narrow-band interferences (NBI) suppression technique based on singular value decomposition (SVD) algorithm for a direct sequence ultra-wideband (DS-UWB) communication system is presented. SVD is used to approximate the interferences which then are subtracted from the received signals. The proposed technique is simple and robust. Simulation results show that the proposed new technique is very effective.

In this letter, we evaluate the M-BOK based DS-UWB system that uses a space-time block code (STBC) with Rake receivers in the WPAN environment. The conventional DS-UWB system doesn't ensure receiver reliability for the WPAN envrionment due to multipath fading, while the proposed M-BOK based DS-UWB system employing a STBC can overcome multipath fading causing attenuation of receiver reliability in the WPAN environment. In addition, a simple diversity combining receiver, called PRake receiver, shows the performance similar to that of a ARake receiver using the ideal diversity combining and reduces the receiver complexity.

In this paper, the impact of timing jitter in direct sequence ultra wideband (DS-UWB) system is investigated over multipath fading channel. Also, a novel hybrid direct sequence multiband UWB (DS-MB-UWB) system is proposed to mitigate the impact of timing jitter. We analyze and compare the system performance for conventional DS-UWB and hybrid DS-MB-UWB with Rake receiver in the presence of timing jitter over additive white Gaussian noise (AWGN) and multipath channel. Theoretical framework is developed to calculate the amount of average energy captured in the multipath profiles and symbol error rate (SER) considering the presence of timing jitter. It is found that DS-MB-UWB system, which employs multiple sub-bands is more jitter-robust than conventional DS-UWB systems. Besides, timing jitter is found to have different impacts on DS-UWB and DS-MB-UWB systems corresponding to different parameters such as number of sub-bands employed, pulse shape, center frequency, bandwidth, number of combined paths in Rake receiver and channel power delay profile (PDP). These different impacts are analyzed and discussed in the paper.

In this letter, we provide a performance evaluation of a Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) with adaptive modulation in a multipath fading channel. The MB-OFDM system in conjunction with adaptive modulation technique can be considered as one of the solutions for severely degraded channels such as those common in frequency selective fading environments.

This letter describes experiments conducted to measure the interference effects of two kinds of UWB sources, which are OFDM UWB source and pulse radio UWB source, to broadcasting relay system and SDMB system. The received power degradation of a broadcasting system is presented. experimental results show that UWB system can coexist 35 m distance as close as to in-band broadcasting network and can also coexist 1.8 m as close as with the SDMB terminal without causing any dangerous interference.

In this letter, we propose a novel packet detection and symbol timing synchronization algorithm for MB-OFDM UWB system over multi-path channel. To find more reliable and exact symbol timing, we utilize the merits of the auto- and cross-correlation at the same time. The auto-correlator can gather the energy of the received signal which is distorted by multipath fading. And, the cross-correlator can estimate symbol timing to sample level precision. We define the detection and symbol timing metric as the moving sum of autocorrelation of the pre-computed cross-correlated signals over zero pad duration. Simulation results show that the proposed algorithm can detect the presence of a signal with less than -4 dB SNR and find DFT window with at most 0.1 dB SNR reduction upon the receipt of two symbols.

In this paper, two new modulation schemes, Multi-Pulse Modulation (MPM) and Differential Multi-Pulse Modulation (DMPM) have been proposed in order to increase the total data rate and improve the error performance. By these schemes, the modulated pulse that had been used for transmitting only one data bit in each pulse-pair in conventional TR-UWB system, can be used for transmitting more than one bit data depending on the level of modulation. Moreover, the error performance has been improved by these new modulation schemes because for the same Eb/N0, the energy per pulse has increased. In addition, these new modulation schemes are applied to a multiple access system. The simulation results show that the total throughput performance of the proposed system has been improved, nearly 2-4 times when compared to the conventional TR-UWB communication system.

In this letter, we suggest two new efficient hardware structures of correlators for packet and frame synchronization of MB-OFDM UWB. In the proposed structure 1, we suggest a hierarchical structure composed of 8 and 16 tap sub-correlators instead of ordinary 128 tap correlators. In the proposed structure 2, we suggest a structure which uses quantized coefficients and simplified multipliers. Results of simulations indicates that the hardware complexities of proposed structures are reduced to about 54% and 31% with minor performance loss, compared with a conventional method.

In this letter, we propose a multi-user detection scheme based on a hidden training sequence for DS-UWB systems. The hidden training sequence, which uses a fraction of the informative sequence's transmitting power as training information, is utilized for the receiver filter adaptation and channel estimation. By using this, the proposed scheme offers increased bandwidth efficiency (no period dedicated for training) and also shows reasonably good performance and near-far resistance in single and multiple-access UWB indoor multipath channel environment.

This paper presents a high performance wideband CMOS direct down-conversion mixer for UWB based on 0.18 µm CMOS technology. The proposed mixer uses the current bleeding technique and an extra resonant inductor to improve the conversion gain, noise figure (NF) and linearity. Also, with an extra inductor and the careful choosing of transistor sizes, the mixer has a very low flicker noise. The shunt resistor matching is applied to have a 528 MHz bandwidth matching at 50 Ohm. The simulation results show the voltage conversion gain of 20.5 dB, the double-side band NF of 5.6 dB. Two-tone test result indicates 11.25 dBm of IIP3 and higher than 70 dBm of IIP2. The circuit operates at the supply voltage of 1.8 V, and dissipates 11.5 mW.

The interference imposed on conventional narrow-band systems by impulse radio UWB (IR-UWB) signals is examined by simulations. The Dirac delta function is employed to model the IR-UWB signal to reduce simulation costs. The simulation results show that the statistical characteristics of this interference deviate from Gaussian noise when the frequency band of the narrow-band system includes a half multiple of the data symbol rate of the IR-UWB system. In the case of pulse-position-modulation UWB signals and biorthogonal-coded bipolar-modulation UWB signals, the performance degradation of the narrow-band system depends on the number of pulse positions and the number of orthogonal codes, respectively.

A sampling frequency offset estimation scheme for MB-OFDM UWB systems is proposed based on technical specification and multi-band utilization of the MB-OFDM. An estimation scheme using simple weighting factor based on the received signal power of each sub-channel is also introduced to efficiently combine estimates obtained from all the sub-carriers and to improve the estimation performance.

In this study, the new signal model suitable for ultrawide band (UWB) indoor environments with random angle spread is proposed to estimate the angle-of-arrivals (AOAs) of clusters in a UWB wireless communication. The subspace based estimation technique adopted for this model is investigated and the estimates of the AOA and distribution parameter on the received clusters are obtained. The proposed model and estimation technique are verified using computer simulations, and the performance of the estimation error is analyzed.

In this letter, we compare a Multiple-Input Single-Output (MISO)-Ultra WideBand (UWB)- Impulse Radio (IR) system and a Single-Input Single-Output (SISO)-UWB-IR system at high transmission rates. We evaluate the Bit Error Rate (BER) of the two systems with some RAKE receivers under heavy multipath environments. From the results of our computer simulation, we show that the SISO-UWB-IR system with Minimum Mean Square Error (MMSE)-RAKE receiver is a good candidate to achieve high transmission rates.

This paper introduces a state-of-art on an ultra-wideband (UWB) technology in intelligent transport systems (ITS). To examine the detection performance of a UWB short-range radar for vehicular applications, we developed a 26-GHz band short-range UWB radar system with an embedded compact MMIC-based RF module. In this paper, we briefly comment on the current regulatory environment for UWB radar systems by outlining the structure of an international organization involved in examining the regulatory status of these systems. We then describe the principles of detection and system design for impulse radar, the radar system that we developed, and a MMIC-based RF module as well as the performance of these devices. We measured their performance in a series of laboratory experiments and also measured UWB radar cross sections of an automobile. The results of our experiments suggest that our radar system is capable of detecting targets with a range resolution of around 9 cm.

This paper describes the measurement techniques of emissions from UWB devices discussed in ITU-R task group (TG) 1/8 to study the compatibility between ultra-wideband (UWB) devices and radiocommunication services. This paper also provides the background idea behind the measurement methods, as the final output of the discussion, i.e. ITU-R Recommendation, will not contain any citations to the references, nor any "educational" description of the theoretical background.

In this paper, we evaluate the computational complexity and the performance of the RAKE receivers for the Direct Sequence--Ultra Wideband (DS-UWB) with considering the accuracy of channel estimation in a multipath channel. As RAKE receivers for DS-UWB, we consider the maximal-ratio combining (MRC)-RAKE, the minimum mean square error (MMSE)-RAKE, and the MRC-RAKE-Equalizer that is the MRC-RAKE followed by a liner equalizer. Generally, if the channel estimation is perfect, as the number of fingers or taps increases, the performance of each receiver is improved, however the computational complexity of each receiver increases. In practice, the channel estimation is not perfect. The channel estimation error makes their performances degraded. Therefore, the performances of the RAKE receivers depend on the accuracy of channel estimation. Consequently, we evaluate the computational complexities and the Bit Error Rates (BERs) of MRC-RAKE, MMSE-RAKE, and MRC-RAKE-Equalizer with considering the accuracy of channel estimation for DS-UWB. We show that the accuracy of channel estimation affects the BER of each receiver significantly. We also show that when the accuracy of channel estimation is high, MRC-RAKE-Equalizer can achieve the better BER than MMSE-RAKE with less computational complexity, while MMSE-RAKE can achieve the better BER than MRC-RAKE-Equalizer when the accuracy of channel estimation is low.