Narrowband Wireless Research Articles

ITERATIVE SOLUTION TO THE NOTCHED WAVEFORM DESIGN IN COGNITIVE ULTRA-WIDEBAND RADIO SYSTEM

Cognitive Ultra Wideband Radio is proposed to exploit the advantages of combining Cognitive Radio with Ultra Wideband technologies, so as to solve the problems of coexistence and compatibility between UWB and other existing narrowband wireless systems. A novel adaptive UWB pulse shaping algorithm with low complexity, instead of notch filter, is presented for producing the expected spectral notches right in the frequency band occupied by the nearby wireless devices. Simulation results show that the proposed UWB waveform has better single-link BER performances in AWGN channel and stronger anti-jamming ability than other conventional waveforms such as Scholtz’s monocycle, etc. Besides, the power spectral density of UWB pulse does not need to be reduced over the whole frequency band. Therefore, it is possible to expand the communication range of UWB systems by increasing the transmitted power of UWB pulse.

Development of Bluewave: A Wireless Protocol for Industrial Automation

There is a growing trend in developing the wireless machine-to-machine (M2M) communication for factory automation. Currently, most wireless protocols for infrastructureless mobile ad-hoc networks focus on the mobility issue and are mainly suitable for narrowband radio devices. The mechanisms for route update and discovery that work well for wireless mobile ad-hoc networks prove to be redundant and instead add to processing overheads in a static wireless factory setting. This paper presents the development and implementation of a new wireless routing protocol, Bluewave, that caters specifically to wireless communication between machines in a factory setting. Bluewave utilizes features of Bluetooth technology when performing the route setup. The merits of the proposed protocol, in terms of shorter initialization time and route setup time, are duly discussed. A case study illustrating the application of Bluewave to an online condition-based maintenance scenario is presented. Experimental results obtained are furnished to show the viability of Bluewave in industrial automation

Ultrawideband as an Industrial Wireless Solution

Ultrawideband wireless technology is capable of transmitting data at very high rates, over a wide frequency spectrum, with very low power consumption. UWB also offers precision location positioning and tracking, significantly expanding its potential application. UWB technology's unique characteristics make it a more suitable solution than narrow-band wireless systems for meeting wireless needs in the industrial environment.

Performance Analysis of UWB Channels for Wireless Personal Area Networks

Ultra-wide band (UWB) communication is one of the most promising technology for high data rate networks over short-range communication. The ultra-wide bandwidth offers pulses with very short duration that provides frequency diversity and multipath resolution. Ultra-wide band (UWB) channels raise new effects in the receiver, the amplitude fading statistics being different compared to the conventional narrow band wireless channels. This review paper focuses on modeling of ultra-wide band channels, especially for simulation of personal area networks and also discusses the benefits, application potential and technical challenges in wideband communication. The concept of Orthogonal Frequency Division Multiplexing (OFDM) has recently been applied in wireless communication systems due to its high data rate transmission capability with high bandwidth efficiency and its robustness to multi-path delay. UWB OFDM communication was proposed for physical layer in the IEEE 802.15.3a standard which covers wideband communication in wireless personal area networks. Since the channel model for multicarrier UWB communication is different from that of plain ultra-wide band channel, a novel modification method in UWB channel model is proposed with specific center frequency and multipath resolution. Moreover, dynamic channel estimation is necessary before demodulation of UWB OFDM signals since the radio channel is time varying and frequency selective for wideband systems. The performance of the proposed method is statistically analyzed using LS and MMSE based channel estimation methods.

Efficient 2-D ray-tracing method for narrow and wideband channel characterisation in microcellular configurations

Channel characterisation is an essential step to the development of outdoor or indoor wireless networks. Indeed, for multimedia applications, new radio mobile systems must accurately take into account channel behaviour. An efficient 2-D ray-tracing method is proposed to characterise the narrowband and wideband radio channels for a very large number of receivers in microcellular configurations. It is based on a quick precalculation of an exact 2-D visibility graph. The proposed method follows an ITU recommendation, which advocates, for wideband characterisation, consideration only of the paths included in a 18-dB dynamic range of power impulse response. Contrary to the classical approach, which consists of thresholding the complete impulse response in a post-treatment, this method only computes the significant paths. The interest of the proposed method resides in its significant computation time reduction factor, in comparison with the classical approach, without any significant loss in accuracy. Received power and wideband parameter maps are computed for about 40 000 receivers in a dense urban environment, and are provided with an approximate reduction factor of four and 80% of the null estimation error in comparison to a classical approach.

Demonstration of reverse Doppler effect using a left-handed transmission line

ABSTRACT: A novel wideband crossed planar monopole antenna hav-ing the band-notched characteristic is presented. The proposed antennaconsist of a wideband crossed planar monopole and multiple U-shapedslots, producing band-notched characteristic. In order to generate theband-notched characteristic on a crossed planar monopole, we proposethat two or four U-shaped slots be required. This technique is suitablefor creating an ultra-wideband (UWB) antenna with a narrow frequencynotch or a multiband antenna. © 2006 Wiley Periodicals, Inc.Microwave Opt Technol Lett 48: 543–545, 2006; Published online inWiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21403 crossed planar monopole antenna; band-notched antenna;wideband antenna 1. INTRODUCTION The planar monopole has recently been investigated as an antennawith wideband properties. This kind of antenna exhibits goodimpedance matching and high efficiency. However, due to thenature of planar monopole antennas, with currents confined to thelower outer edges, a variation of the radiation pattern with changeof frequency is inevitable. To solve this problem, the crossedplanar monopole has recently been studied [1–3], and improvedomnidirectional radiation patterns for frequencies across a wideoperating bandwidth have been obtained.Due to collocation of the wideband system with frequencybands reserved for narrowband wireless technologies, there is aneed for the wideband device to provide filtering in those bands inorder to avoid causing interference from or to narrowband devices.In [4–6], a planar monopole was shown to exhibit a single-frequency notch band while maintaining wideband performance.However, there is no solution for a crossed planar monopoleantenna with the frequency band-notched characteristic.In this paper, we explore the ability to achieve the band-notchedcharacteristicinawidebandcrossedplanarmonopole.Theability to provide this function in the antenna can significantlyrelax the requirements imposed upon the filtering electronicswithin the wireless device. Two types of the crossed planar mono-pole antenna with the band-notched feature are presented. Theproposed antennas are fabricated and studied.

Measurement and Characterization of the Temporal Behavior of Fixed Wireless Links

We analyze the methodology and present the interpretation of results obtained in the measurement of the temporal Ricean K-factor and the time-autocovariance function of the received power for fixed narrowband wireless links in urban residential environments. Our main observation is that the time-autocovariance function (and thus both the temporal K-factor and the coherence time) fundamentally depends on a combination of the characterization of the transmit-receive path and whether the street-level moving objects are in the field of view of the antennas. In most practical cases the latter refers only to the customer premises antenna, as the base station is typically placed at a much greater distance from moving scatterers. No significant basis was found for the popular conjecture that the K-factor is mainly influenced by the excess path loss. However, a strong correlation between coherence times and temporal K-factor was observed over a wide range of link conditions. We also found that the time-autocovariance function can be quite accurately modeled by the weighted sum of two exponentially decaying functions: one with a time constant on the order of 1 s and the other typically slower by one order of magnitude. The results will be helpful in establishing design criteria for radio systems such as multiple input-multiple output that need to estimate the channel response and its persistence in time and for media access control (MAC) layer transmission protocols whose efficiency is affected by the depth and duration of channel outages.

Intercell radio interference studies in CDMA-based LMDS networks

Among the various alternatives investigated for enhancing the capacity of the millimeter wave segment of broadband wireless access (BWA) networks is the use of orthogonal direct sequence code division multiple access (DS-CDMA) instead of time division multiple access (TDMA), the dominant multiple access scheme to date. This paper aims at contributing to the ongoing research on the feasibility of CDMA-based Local Multipoint Distribution Service (LMDS) by presenting an analytical study of intercell interference, which is the major factor limiting capacity. The study is focused on the statistical properties of the carrier-to-interference ratio (CIR) in both the downstream and the upstream channel. Since the propagation phenomena affecting LMDS are quite different than those affecting narrowband wireless networks, emphasis is placed on incorporating the spatial inhomogeneity of rain attenuation in the interference analysis and on estimating the additional CIR degradation not taken into account in the conventional clear sky approach. The proposed model is accompanied by illustrative simulations identifying worst case interference scenarios and clarifying various aspects of the system.

A wireless multimedia framework for the management of emergency situations in automotive applications: The AIDER system

Automotive applications would greatly benefit of multimedia telematic services for many purposes, from tourism and entertainment, to most important issues such as security and traffic management. Within this context, the AIDER system (AIDER is the acronym of Accident Information and Driver Emergency Rescue) is one of the most advanced multimedia mobile services targeted at emergency situations such as road accidents. The AIDER allows the interactive exchange of multimedia data (and in particular, audio, video and biomedical information) between the vehicle and a remote rescue centre, by using several different narrowband radio channels including cellular networks and satellite. In this paper an overview of the AIDER architecture is provided, focusing on the advanced video communication system.

A Proxy Architecture to Enhance the Performance of WAP 2.0 by Data Compression

This paper presents a novel proxy architecture for wireless application protocol (WAP) 2.0 employing an advanced data compression scheme. Though optional in WAP 2.0, a proxy can isolate the wireless from the wired domain to prevent error propagations and to eliminate wireless session delays (WSD) by enabling long-lived connections between the proxy and wireless terminals. The proposed data compression scheme combines content compression together with robust header compression (ROHC), which minimizes the air-interface traffic data, thus significantly reduces the wireless access time. By using the content compression at the transport layer, it also enables TLS tunneling, which overcomes the end-to-end security problem in WAP 1.x. Performance evaluations show that while WAP 1.x is optimized for narrowband wireless channels, WAP 2.0 utilizing TCP/IP outperforms WAP 1.x over wideband wireless channels even without compression. The proposed data compression scheme reduces the wireless access time of WAP 2.0 by over 45% in CDMA2000 1XRTT channels, and in low-speed IS-95 channels, substantially reduces access time to give comparable performance to WAP 1.x. The performance enhancement is mainly contributed by the reply content compression, with ROHC offering further enhancements.

Ultra-wideband for multiple access communications

Ultra-wideband wireless communications techniques have many merits, including an extremely simple radio that inherently leads to low-cost design, large processing gain for robust operations in the presence of narrowband interference, covert operations, and fine time resolution for accurate position sensing. However, there are a number of challenges in UWB receiver design, such as capturing multipath energy, intersymbol interference especially in a non-line-of-sight environment, and the need for high-sampling-rate analog-to-digital converters. In this article, we provide a comprehensive review of UWB multiple access and modulation schemes, and their comparison with narrowband radios. We also outline the issues with UWB signal reception and detection, and explore various suboptimal low-complexity receiving schemes.

Ultrawideband through-the-wall propagation

The propagation of ultrawideband (UWB) signals in indoor environments is an important issue with significant impacts on the future direction and scope of UWB technology. The propagation of UWB signals is governed, among other things, by the properties of materials in the propagation medium. The information on electromagnetic properties of construction materials in the UWB frequency range would provide valuable insights into the appreciation of the capabilities and limitations of UWB technology. Although electromagnetic properties of certain construction materials over relatively narrow bandwidths in GHz frequency ranges are available, ultrawideband characterisation of most typical construction materials for UWB communication purposes has not been reported. In narrowband wireless communications, only the magnitude of insertion loss has been the quantity of interest. But for UWB signals, in addition to the magnitude, the phase information is an equally important factor that needs to be accounted for. In fact, UWB signals not only suffer attenuation when propagating through walls, but also suffer distortion due to the dispersive properties of the walls. This research examines propagation through typical construction materials and their ultrawideband characterisation. Ten commonly used construction materials are chosen for this investigation. Results for the dielectric constant and loss tangent of the materials over the UWB frequency range are presented. Accuracy of the measured results is discussed and distortions of UWB signals due to the dispersive properties of wall materials are addressed.

Direct Position Determination of Narrowband Radio Frequency Transmitters

The most common methods for location of communications or radar transmitters are based on measuring a specified parameter such as signal angle of arrival (AOA) or time of arrival (TOA). The measured parameters are then used to estimate the transmitter location. Since the AOA/TOA measurements are done at each base station separately, without using the constraint that all measurements must correspond to the same transmitter, they are suboptimal. We propose a technique that uses exactly the same data as the common methods, except that the estimation of location is based on exact maximum likelihood, and the location determination is direct. Although there are many stray parameters, including the attenuation coefficients and the signal waveform, the method requires only a two-dimensional search. Monte Carlo simulations indicate that the accuracy is equivalent to AOA, TOA, and their combination for high SNR, while for low SNR, the accuracy of the proposed method is superior.

Optical Single-Sideband Modulators and Their Applications

We review our recent work in the implementation of optical single-sideband (OSSB) modulation and in the application of this modulation format to microwave photonics and optical testing systems. We have developed an enhanced OSSB modulator for wide-band operation, the so-called bidirectional OSSB modulator, and a simplification of this scheme for narrow-band applications. These OSSB modulators are based on the use of a standard single-electrode Mach-Zehnder electro-optic modulator (MZ-EOM) and passive fiber-optic components. In both designs, the OSSB operation is shown to be independent of the MZ-EOM bias. Therefore, the optical modulation depth at the output of the device can be enhanced using minimum transmission biasing to provide suppression of the optical carrier. Finally, we demonstrate the application of OSSB modulators to the improvement of microwave/millimeter-wave subcarrier multiplexing fiber-optic links and to narrow-band fiber radio systems. In addition, we analyzed the feasibility and the limitations of an optical vector network analysis technique based on OSSB modulation that can provide sub-picometer wavelength resolution.

Channel models for ultrawideband personal area networks

This article describes the modeling of ultrawideband wireless propagation channels, especially for the simulation of personal area networks. The IEEE 802.15.3a standards task group has established a standard channel model to be used for the evaluation of PAN physical layer proposals. We discuss the standard model, the measurements that form its basis, and the possibilities for future improvements. This article points out the important differences between UWB channels and narrowband wireless channels, especially with respect to fading statistics and time of arrival of multipath components. The impacts on the different propagation conditions on system design, like RAKE receiver performance, are elaborated.

A narrowband interference rejection technique for DS‐CDMA system

AbstractDue to congestion in wireless frequency use, it is difficult to assign an independent frequency bandwidth to broadband wireless communication systems based on the DS‐CDMA (Direct Sequence Code Division Multiple Access) system. Therefore, operation of the DS‐CDMA system on the existing narrowband wireless system is contemplated. However, the interference of the transmitted power of the existing narrowband wireless system on the DS‐CDMA system has not been studied. There is a possibility that significant narrowband interference on the DS‐CDMA system may occur. In this paper, a narrowband interference rejection system in DS‐CDMA is proposed. By making use of prior information on the carrier frequency of the narrowband interference, a narrowband interference rejection process with little computational overhead is realized. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(3): 74–86, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10076

Ultra‐wideband wireless communications

AbstractUltra‐wideband (UWB) communication techniques have attracted a great interest in both academia and industry in the past few years for applications in short‐range wireless mobile systems. This is due to the potential advantages of UWB transmissions such as low power, high rate, immunity to multipath propagation, less complex transceiver hardware, and low interference. However, tremendous R&D efforts are required to face various technical challenges in developing UWB wireless systems, including UWB channel characterization, transceiver design, coexistence and interworking with other narrowband wireless systems, design of the link and network layers to benefit from UWB transmission characteristics. This paper is to provide an overview of UWB communications, summarize the previous research results, and identify further research issues that need to be tackled. The emphasis is placed on the commercial wireless communications. Copyright © 2003 John Wiley & Sons, Ltd.

Optimum design criterion and multilevel coding for radio systems over AWGN and Rayleigh fading channels

AbstractFor the narrow band Wireless Code Division Multiple Access (WCDMA) system, there are some channel coding schemes proposed and applied like Turbo code and convolutional codes. But for the 4G Code Division Multiple Access (CDMA) wideband systems, we have to use new channel coding schemes with high bandwidth efficiency. In this case, multilevel coding (MLC) scheme is easy to map to Multiple Quardrature Amplitude Modulation (MQAM) modulation strategy to be used for 4G, and MLC+MQAM will be a potential channel coding scheme for the error correcting of next generation of mobile systems.A novel criterion, that is ‘capacity rule’ plus ‘mapping rule’, for the design of the optimum MLC scheme for radio systems over Rayleigh fading channels is proposed in this paper. Based on this theory, a few of key issues related to design an optimum MLC system are investigated. These include a novel optimum design criterion proposed, different mapping strategies, different decoding methods of MLC/MSD and MLC/Parallel Decoding on Levels (PDL) and their performance comparison over Additive White Gaussian Noise (AWGN) and Rayleigh fading channels respectively. Copyright © 2003 John Wiley & Sons, Ltd.

New analytical models and probability density functions for fading in wireless communications

This paper presents new envelope probability density functions (PDFs) that describe small-scale, local area fading experienced by narrow-band wireless receivers. The paper also develops novel PDFs that describe the local area fading of two specular multipath components in the presence of other diffusely propagating waves. These PDFs are studied in the context of classical fading PDFs such as the Rayleigh, Rician, and other distributions.

Cable measurements supporting xDSL technologies

The ongoing developments in the field of high-speed data transmission over twisted-pair cables (DSL-Digital Subscriber Line) leads to methods that can exploit the transmission media with increased efficiency. MIMO (Multiple-Input Multiple-Output) transmission, i.e., the coordinated use of many pairs within a bundle, is such an emering DSL technology. A further goal is to maintain a certain transmission quality in the presence of non-DSL noise. For example, cancellation techniques to combat narrowband radio interference, which is generated by radio amateur transmitters and may be picked up by the wire close to the subscriber or by the in-hourse wiring, become important.