Impulse Radio Ultra-wide Bandwidth Research Articles

CNN-Based Regional People Counting Algorithm Exploiting Multi-Scale Range-Time Maps With an IR-UWB Radar

In this paper, we propose a novel people counting algorithm exploiting convolutional neural network (CNN) using a low radiation impulse radio ultra-wide bandwidth (IR-UWB) radar. Because of the ever-changing signals caused by the various cases of human motion scales, superposition and obstruction of signals as well as the attenuate of signal’s strength along the distance and the angle, it is not easy to handle the people counting task by directly detecting targets for each range bin. Thus, we hope to excavate the information of targets’ patterns, including their densities and forms of patterns’ distributions in the detecting region to execute the counting task. To achieve this, the multi-scale range-time maps are extracted from the received data and further used to classify the number of people using the CNN. Finally, the experiments are conducted to show the priority of the proposed 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.

On the Benefits of MAI-Plus-Noise Whitening in TH-BPSK IR-UWB Systems

Multiaccess interference (MAI)-plus-noise whitening for detecting impulse radio ultra-wide bandwidth (IR-UWB) signals transmitted over ideal free-space and the IEEE 802.15.3a channels is considered. IR-UWB signals are very sparse in time and, thus, MAI-plus-noise whitening cannot introduce intersymbol interference (ISI) in IR-UWB systems operating on an ideal free-space channel. In addition, ISI in UWB multipath fading channels can be eliminated by a proper choice of the frame duration. An analytical expression for the signal-to-interference-plus-noise ratio (SINR) of IR-UWB systems after MAI-plus-noise whitening is derived and the SINR improvement due to whitening is investigated. It is shown that whitening can improve the performance of a variety of the well-known IR-UWB receivers, viz., soft-limiting, P-order metric, optimal, and the conventional matched filter receivers. It is also observed that MAI-plus-noise whitening can improve the overall SINR of the system and, thus, decrease the complexity of Rake receivers through reducing the number of their processing branches.

Direct Sequence and Time-Hopping Sequence Designs for Narrowband Interference Mitigation in Impulse Radio UWB Systems

Direct sequence and time-hopping sequence designs are proposed for impulse radio ultra-wide bandwidth systems to suppress the mutual interference between ultra-wide bandwidth wireless and coexisting narrowband services. Notch frequencies are created in the ultra-wide bandwidth signal spectrum at bands where narrowband services operate. The direct sequence and the time-hopping sequence designs have low computational complexities and can be easily implemented in practical systems. When combined with the cognitive radio technique, these designs can adapt to channel conditions according to the spectral occupancy information provided by cognitive radio. Numerical results are provided to show that these designs can significantly suppress the mutual interference between ultra-wide bandwidth and narrowband services. Therefore, the integrity of both ultra-wide bandwidth and narrowband systems can be highly enhanced.

An analytical method for calculating the bit error rate performance of rake reception in UWB multipath fading channels

The bit error rate performance of Rake reception of impulse radio ultra-wide bandwidth signals over the IEEE 802.15.3a channel models is evaluated. Instead of using Gaussian approximation for the probability density function of the total disturbance which includes the multi-user interference and the background additive white Gaussian noise, two new models dubbed the "composite lognormal-Gaussian" and the "composite lognormal-Laplacian" are proposed for modeling the multi-user interference and shadowing in ultra-wide bandwidth multipath fading channels. Tractable formulae for bit error rate evaluation of Rake reception in ultra-wide bandwidth multipath channels are derived for both models. Numerical results indicate that these formulae predict the bit error rate performance with good accuracy, and can be rapidly and easily evaluated using commonplace computer resources.

SNR analysis for multi-rate UWB-IR

This letter is motivated by the need to design MAC protocols for impulse radio ultrawide bandwidth systems. It evaluates the signal-to-noise ratio (SNR) in such multi-rate systems in which the different users transmit with different rates and different power levels. The SNR is obtained for all combinations of pulse-position modulation or pulse-amplitude modulation, with time-hopping and/or direct-sequence spreading. We show that the SNR in a multi-rate time-hopping system is different from a single-rate system, and is highly affected by the low-rate users