Ultra-wideband Networks Research Articles

Evaluation of a Novel Radar Based Scanning Method

The following paper introduces a novel scanning method for mapping and localization purposes in mobile robotics. Our method is based on a rotating monostatic radar network, which determines the positions of objects around the scanner via a continuously running lateration algorithm. The estimation of surfaces with ultrawideband radar networks has been studied experimentally in lab environments, especially with lateration, envelopes of spheres, and SEABED algorithms. But we do not see a link to the field of mapping and localization of mobile robots, where laser scanners are dominating. Indeed, only few research groups use radars for mapping and localization, but their applied sensor principle is based on a rotating focused radar beam. Consequently, only 2D radar scanners are known inside the robotic world and methods for 3D scanning with radars need to be investigated. This paper will derive the theoretical background of the sensor principle, which is based on a radar network on a rotating joint, and discuss its erroneous influences. We were performing first scans of standard geometries and deriving a model in order to compare theoretical and experimental measurement results. Furthermore, we present first mapping approaches and a simulation of a scanner with multiple sensors.

UWB monopole antenna with multiple fractal slots for band-notch characteristic and integrated Bluetooth functionality

This article presents the design of compact microstrip-fed modified half annular-shaped planar monopole antenna for ultra-wideband (UWB) (3.1–10.6 GHz) application. An electromagnetically coupled circular-shaped parasitic patch is introduced at the backside of the substrate to enhance the bandwidth of the whole antenna by shifting the lower frequency band. A rectangular slot-embedded ground plane at the bottom surface of the substrate improves the impedance bandwidth with excellent matching characteristics for the entire design frequency band. In addition to this, a half Minkowski fractal slot, a hybrid fractal slot, and Sierpinski arrowhead curve fractal slot are coupled to the feed line individually such that three UWB antennas with band-notched characteristic are realized that mitigate the interference between UWB and Wireless local area network (5.15–5.825 GHz) assigned to IEEE 802.11a and HIPERLAN/2 can be reduced. Now to increase the functionality of the antenna, a second iterated fractal binary tree is embedded on the patch to excite resonant mode centered at 2.45 GHz for the Bluetooth band. The proposed antenna exhibits omnidirectional radiation pattern and constant gain characteristics over the desired frequency band except the notch band. Prototypes of variants are fabricated and measured results agree well with simulation.

Frequency reconfigurable bow‐tie antenna array

A novel frequency reconfigurable bow-tie antenna array for Bluetooth, worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) applications is presented. This array comprises four double-sided bow-tie elements and an ultra-wideband feed network. By controlling the states of the pin diodes loaded on the radiators, the effective electrical lengths of bow-tie elements can be changed, thus the operating band of the array can be electronically switched between three different frequency bands. A prototype was fabricated and measured, and the results are in good agreement with the simulations, which shows that this array is a good candidate for multi-radio wireless applications.

효율적인 멀티미디어 전송을 위한 분산방식 MAC 프로토콜 성능분석

The salient features of UWB(Ultra WideBand) networks such as high-rate communications, low interference with other radio systems, and low power consumption bring many benefits to users, thus enabling several new applications such as wireless universal serial bus (WUSB) for connecting personal computers (PCs) to their peripherals and the consumer-electronics (CE) in people's living rooms. Because the size of multimedia data frame, WiMedia device must transmit the fragment of MSDU. However, when the fragment of MSDU is lost, WiMedia device maintains active mode for the time to complete the transmission MSDU, and there is a problem that unnecessary power consumption occurs. Therefore we propose new power management scheme to reduce unnecessary power consumption of WiMedia devices in the case that the fragment is lost.

A Multi-channel Scheduling Scheme for Collision-Free High-Rate WPANs

Ultra wide-band (UWB) technologies are being feverishly developed in the technical community. UWB devices are expected to operate at rates of up to 0.5 Gb/s and communicate with other devices at a range of up to 10 m. Thus, UWB technologies are being developed as core technology for high-speed wireless personal area networks. The salient features of UWB networks--high-rate communications, low interference with other radio systems, and low power consumption--bring many benefits to users. Thus, they enable consumers to experience new applications such as wireless universal serial bus for connecting personal computers to their peripherals and the consumer---electronics in people's living rooms. However, if multiple WiMedia logical link protocol Service Sets (WSSs) coexist in an adjacent area, various conflicts among independent WSSs can occur frequently. In order to solve this problem, we propose a multi-channel scheduling scheme (MCS) for the coexistence of adjacent WSSs. The proposed MCS scheme can scan new idle channel and detect its time offset where a WSS device can transmit a new beacon frame and data frames without conflicts. We also evaluate the performance of the proposed MCS scheme through various simulations in terms of several metrics. Simulation results demonstrate that the MCS scheme can minimize the possibility of data frame collisions by efficiently managing the multiple available channels in a hybrid manner combining proactive and reactive methods.

Performance of Two-Way Code-Multiplexed UWB Relay Networks

Recently, two-way relay network has been taken attention. In this paper, the two-way relayprotocols of ultra-wideband (UWB) network based on code-multiplexed transmitted-reference (CMTR)impulse radio have been studied. Based on code-multiplexed scheme, a new two-way relayingstrategy for two-slots protocol is designed. The corresponding bit error rate (BER) performance isevaluated via simulations and compared with three-slots scheme which can get path diversity gainfrom direct link between terminals. Simulation results reveal that the performance of the two-slotsrelaying scheme is almost same with that of the three-slots scheme. Meanwhile the throughput ispromoted about 33% over three-slots scheme.

거대 초 광 대역 애드 혹 네트워크에서의 개선된 용량 스케일링

n개의 무선 노드가 랜덤하게 위치한 초 광 대역 애드 혹 네트워크에서의 개선된 용량 스케일링 법칙을 보인다. 먼저, 수정된 계층적 협력 기술이 사용되는 경우를 고려한다. 단위 면적의 밀집 네트워크에서, 유도한 용량 스케일링은 전력 제한된 성격 때문에 특정 동작 영역에서 경로손실 지수 <TEX>${\alpha}$</TEX>에 의존함을 보인다. 또한, 계층적 협력 기술은 2 < <TEX>${\alpha}$</TEX> < 3에서 우월하지만 <TEX>${\alpha}{\geq}3$</TEX>에 대해서는 다중 홉 라우팅을 사용하는 것이 더 높은 용량을 취득함이 밝혀진다. 둘째로, m개의 기지국이 초 광 대역 네트워크에 균일하게 분포한 경우, 인프라 구조의 영향 및 이득을 분석한다. 이때, 모든 동작 영역에 대해 전력 제한된 성격 때문에, 유도한 용량 스케일링은 <TEX>${\alpha}$</TEX>에 의존한다. 게다가, 변수 m이 특정 레벨 이상일 때 전체 용량이 m과 함께 선형적으로 스케일함을 보인다. 그러므로 계층적 협력 또는 인프라 구조의 사용은 특정 조건에서 초 광 대역 네트워크의 용량을 개선하는데 도움이 된다. We show improved throughput scaling laws for an ultra-wide band (UWB) ad hoc network, in which n wireless nodes are randomly located. First, we consider the case where a modified hierarchical cooperation (HC) strategy is used. Then, in a dense network of unit area, our result indicates that the derived throughput scaling depends on the path-loss exponent <TEX>${\alpha}$</TEX> for certain operating regimes due to the power-limited characteristics. It also turns out that the HC protocol is dominant for 2 < <TEX>${\alpha}$</TEX> < 3 while using the nearest multihop (MH) routing leads to a higher throughput for <TEX>${\alpha}{\geq}3$</TEX>. Second, the impact and benefits of infrastructure support are analyzed, where m base stations (BSs) are regularly placed in UWB networks. In this case, the derived throughput scaling depends on <TEX>${\alpha}$</TEX> due to the power-limited characteristics for all operating regimes. Furthermore, it is shown that the total throughput scales linearly with parameter m as m is larger than a certain level. Hence, the use of either HC or infrastructure is helpful in improving the throughput of UWB networks in some conditions.

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.

Distributed multi-hop reservation protocol for wireless personal area Ultra-Wideband networks

Ultra-wideband (UWB) technology is a promising technology for multimedia applications in wireless personal area networks (WPANs) that supports very high data rates with lower power transmission for short range communication. The limitation of coverage radius of UWB network necessitates for multihop transmissions. Unfortunately, as the number of hops increases, the quality of service (QoS) degrades rapidly in multihop network. The main goal of this research is to develop and enhance multihop transmission that ensures QoS of real time traffic through the proposed distributed multihop reservation (DMR) scheme. The DMR scheme consists of two modules; distributed multihop reservation protocol (DMRP) and path selection. DMRP incorporates resource reservation, routing and connection setup that are extended on the existing WiMedia Media Access Control protocol (MAC). On the other hand, the path selection determines the optimal path that makes up the multihop route. The path selection selects nodes based on the highest Signal to Interference and Noise Ratio (SINR). The performance of DMR scheme has been verified based on the performance of the video traffic transmission. The main metrics of QoS are measured in terms of Peak Signal- to- Noise ratio (PSNR), End-to-End (E2E) delay, and throughput. The results show that DMRP compared to Multiple Resources Reservation Scheme (MRRS) in six (6) hops transmission has enhanced the average PSNR by 16.5%, reduced the average E2E delay by 14.9% and has increased the throughput by 11.1%. The DMR scheme which is the inclusion of path selection in DMRP has been compared to Link Quality Multihop Relay (LQMR). DMR scheme has improved the video quality transmission by 17.5%, reduced the average E2E delay by 18.6% and enhanced the average throughput by 20.3%. The QoS of six (6) hops transmission employing DMR scheme is almost sustained compared to two hops transmission with the QoS experiencing only slight degradation of about 2.0%. This is a considerable achievement as it is well known that as the number of hops increases the QoS in multihop transmission degrades very rapidly. Thus DMR scheme has shown to significantly improve the performance of real time traffic on UWB multihop network. In general, DMR can be applied to any WPAN network that exploit multihop transmission.

A Cross-layer Link Adaptive HD Video Transmission Scheme in WiMedia D-MAC based UWB Systems

In this paper, we propose a QoS (Quality of Service)-aware and cooperative resource reservation scheme using cross-layer link adaptation for wireless high definition video transmission through UWB (Ultra Wide Band) network with D-MAC (Distributed Medium Access Control). A wireless high definition video transmission system usually requires stable high throughput even without line-of-sight, e.g., a destination device in another room separated by a wall. Since the WiMedia D-MAC supporting DRP (Distributed Reservation Protocol) scheme causes lots of DRP resource reservation conflicts due to failure of beacon detection in wireless channel environment, overall performances of the WiMedia D-MAC can be deteriorated. And the current WiMedia MAC standard has not considered QoS provisioning even though QoS parameters such as a range of service rates are provided to each traffic stream. Therefore, we propose Relay DRP protocol with QoS-based relay node selection criterion, which makes a relay path to avoid DRP resource reservation conflicts and guarantee QoS more stably through cross-layer link adaptation of cooperative relay transmission scheme and is compliant with the current WiMedia D-MAC protocol. Simulation results demonstrate performance improvements of the proposed method for throughput and QoS provisioning.

Compact Coplanar Waveguide-fed Planar Antenna for Ultra-wideband and WLAN Applications

A novel compact planar antenna is presented for Ultra-wideband (UWB) applications in this paper. The proposed antenna has rectangle-like slot and it is fed by coplanar waveguide. The antenna is printed on FR4 substrate and it has compact size of $$28 \times 31 \times 0.8 \,\,\text{ mm}^{3}$$ . Parametric study is performed on the antenna by investigating the effect of various geometrical parameters on the frequency characteristics. The antenna is fabricated and measured. It has better return loss response and stable gain over the entire UWB band. The antenna has stable radiation pattern and good impedance matching over entire ultra-wide bandwidth of 3---10.6 GHz. The results show that there is good agreement between measured and simulated results. Various features such as compactness, simple configuration and low fabrication cost make the antenna suitable for UWB and wireless local area network systems.

Game-theoretic approach for interference management in heterogeneous multimedia wireless personal area networks

Emergence of new wireless technologies has facilitated the way to higher data rates and more robust communication links. Ultra wideband (UWB) is one of these promising technologies that, despite its several outstanding benefits, can cause interference to other networks operating in the same frequency range because of its large bandwidth. In this study, the authors introduce a solution for interference management in heterogeneous UWB networks. The analysis can be generalised for other coexistence scenarios where we have wireless networks with different specifications. Game theory is used to study the joint power and rate control problem under mutual interference between two UWB standards, namely, multiband orthogonal frequency division multiplexing UWB and direct-sequence UWB. A non-cooperative joint rate and power control game with pricing (NRPGP) in which each node seeks to choose its possible transmit power and rate in order to maximise its own utility while satisfying its target signal-to-interference-and-noise ratio as quality-of-service requirement is introduced. Simulation results are provided to evaluate the performance of the proposed game, NRPGP.

SocialMesh: Can networks of meshed smartphones ensure public access to twitter during an attack?

We explore whether public data networks called SocialMesh - formed automatically from smartphone radio-routers and adapting to changing RF propagation and interference without relying on managed cellular infrastructure - can also be designed to overcome any and all countermeasures mounted by an attacker and reliably support social applications such as Twitter, Facebook, and Google. We rigorously examine the architecture, techniques and algorithms that make decentralized or "ad-hoc," ultrawideband networks work in the presence of hostile jamming or protocol attacks. We illustrate the RF link-budget using 3-d graphs to show how interference affects the network performance as these networks become heavily utilized or jammed. Using low-cost hardware, self-organizing routing software, and uncoordinated/distributed CDMA we show how they can retain adequate system capacity even under heavy load from users or interference from jammers. Open standardization and field trials of SocialMesh networks will further clarify SocialMesh security and performance by opening up the design specifications to international review. Open-source design specifications for SocialMesh will be updated at http://www.socialmesh.org.

Throughput Scaling of Ultra-Wide Band Ad Hoc Networks with Infrastructure

The impact and benefits of infrastructure support are shown by introducing an achievable throughput scaling law of a ultra-wide band (UWB) ad hoc network in which m base stations (BSs) are regularly located. The existing multi-hop scheme consisting of two variants, with and without BS help, is utilized with a slight modification. Our result indicates that the derived throughput scaling depends on the path-loss exponent due to the power-limited characteristics for all operating regimes examined. Furthermore, it is shown that the total throughput scales linearly with parameter m as m is larger than a certain level. It thus turns out the use of infrastructure is also helpful in improving the throughput scaling of UWB networks in some conditions.

Enhanced FCME Thresholding for Wavelet-Based Cognitive UWB over Fading Channels

The cognitive ultra-wideband (UWB) network detects interfering narrowband systems and adapts its configuration accordingly. An inherently adaptive and flexible candidate for cognitive UWB transmission is the wavelet packet multicarrier modulation (WPMCM). In this letter, we use an enhanced forward consecutive mean excision thresholding algorithm to tackle the noise uncertainty in the wavelet-based sensing of WPMCM systems, and mathematical analysis is performed for primary user channel fading. As a benchmark, we compare the proposed system with a conventional fast Fourier transformation-based system, and performance investigation proves significant improvements when primary and secondary links are subjected to multipath fading and noise.

Interference Aware-based Ad-Hoc On Demand Distance Vector (IA-AODV) ultra wideband system routing protocol

Ultra wideband (UWB) systems are communication systems based on a baseband impulsive transmission that has recently excited interest both in the commercial and academic fields. Physical layer aspects and MAC protocols have been intensively investigated in the recent years leading, in some cases, to important and definitive results. However, many questions relating to the UWB network layer are still open. The aim of this paper is to investigate the network layer of the UWB system: for this purpose a new routing protocol called Interference Aware-based Ad-Hoc On Demand Distance Vector (IA-AODV) and based on the interference concept has been proposed. In particular, two distinct metrics are explained in detail: the first one is based on the concept of global interference perceived by each node; the second one is based on the concept of link interference perceived by a node on a wireless path to a generic neighbor. Finally, a comparative analysis between our protocol and Ad-Hoc On Demand Distance Vector (AODV) protocol are carried out in order to show the soundness of our proposal.

A cross-layer stability-based routing mechanism for ultra wideband networks

Ultra wideband (UWB) radio is emerging as an attractive physical layer for mobile ad hoc network (MANET). Routing in MANET is a challenge owing to the dynamic nature of network topology and resource constraints. A stable routing mechanism is proposed for UWB network in this paper, focusing on the instability problem derived from communication gray zone. This mechanism is a cross-layer enhancement of ad hoc on-demand vector (AODV) routing protocol, which is named as CLS_AODV. The routing discovery algorithm is extended by introducing the notion of source routing and ad hoc on-demand multipath distance vector (AOMDV) routing. A computing model is established to map received signal strengths into link stability factor and route stability factor which serves as a routing metric for path selection. In contrast to the reactive way in AODV, the received signal strength can be used to reveal the link state information for gray zone prediction, as well as for route state monitoring. A HELLO-based preemptive local route repair algorithm is presented to prevent the occurrence of link breakage. HELLO message is extended not only for neighbor sensing and neighborhood information exchanging, but also as an ON/OFF command to control the position location scheme and HELLO scheme of neighbor nodes. The simulation results show the improvements of CLS_AODV in terms of packet loss ratio and average end-to-end delay without compromising the throughput performance compared with AODV.

Interference Management and Rate Adaptation in OFDM-Based UWB Networks

Ultrawideband (UWB) communications has emerged as a promising technology for high data rate wireless personal area networks (WPANs). Several proposals for UWB-based WPANs have been made. One widely popular proposal was standardized by ECMA-368, and is based on OFDM. In this paper, we address one of the important aspects that impact the performance of this standard, namely interference management between different uncooperative beacon groups that operate simultaneously over the same area. We first propose an interference management distributed reservation protocol (IM-DRP) for OFDM-based UWB communications. IM-DRP aims at improving the throughput of an UWB WPAN by reducing interference between uncooperative beacon groups. We then integrate IM-DRP into the design of a rate adaptation strategy that exploits the multirate capability of OFDM-based UWB systems. Besides maintaining a target packet error rate, our proposed strategy attempts to reduce the required reservation time over a link, hence allowing more links to be simultaneously activated. This improves the overall network throughput. Simulations are used to demonstrate the performance gain of our proposed schemes.

A Cross-Layer Approach in Sensing and Resource Allocation for Multimedia Transmission over Cognitive UWB Networks

We propose an MAC centric cross-layer approach to address the problem of multimedia transmission over cognitive Ultra Wideband (C-UWB) networks. Several fundamental design issues, which are related to application (APP), medium access control (MAC), and physical (PHY) layer, are discussed. Although substantial research has been carried out in the PHY layer perspective of cognitive radio system, this paper attempts to extend the existing research paradigm to MAC and APP layers, which can be considered as premature at this time. This paper proposed a cross-layer design that is aware of (a) UWB wireless channel conditions, (b) time slot allocations at the MAC layer, and (c) MPEG-4 video at the APP layer. Two cooperative sensing mechanisms, namely, AND and OR, are analyzed in terms of probability of detection ( ), probability of false alarm ( ), and the required sensing period. Then, the impact of sensing scheduling to the MPEG-4 video transmission over wireless cognitive UWB networks is observed. In addition, we also proposed the packet reception rate- (PRR-) based resource allocation scheme that is aware of the channel condition, target PRR, and queue status.

Energy Normalized Correlation for Signal Acquisition in Power-Control-Absent UWB Networks

This letter presents a novel detection method for signal acquisition in a power-control-absent ultra-wideband (UWB) system where concurrent transmissions are unavoidable. In such a scenario, the conventional single-user detection method which is based on correlating the received signal with a template pulse train suffers from the near-far effect, since the matched-filter sum can easily be overwhelmed by a strong interferer. Our proposal copes with this near-far issue by compensating the correlation result based on the energy in the sliding window. Therefore the energy normalized correlation is sensitive to the existence of a pulse but not to its strength. Our proposal is compared with the conventional method in terms of the probability of faulty acquisition. Simulation results show substantial improvement using our proposed method in an indoor environment with uncontrolled multi-user interference (MUI). We also point out that hybrid time hopping (TH)/direct sequence (DS) UWB systems result in less faulty acquisition than TH UWB systems.