UWB Networks Research Articles

Polling Schedule Algorithms for Data Aggregation with Sensor Phase Control in In-Vehicle UWB Networks

Polling Schedule Algorithms for Data Aggregation with Sensor Phase Control in In-Vehicle UWB Networks

Accuracy enhancement of Wi-Fi positioning by ranging in dense UWB networks

This study proposed a fusion-based approach of Wi-Fi fingerprint positioning with relatively accurate UWB ranging in dense wireless networks (DWNs) to optimize indoor localization accuracy. Such an optimization was achieved through a proposed objective or “loss” function that minimizes the total positioning errors of the nodes composing a virtual geometric structure with the internode distances preserved during optimization in the DWN. Theoretical analysis and simulation results of DWNs up to 100 nodes revealed that, with at least 6 extra measured distances among as few as 4 participating nodes including the device-under-targeting (DUT) itself, the resulting localization accuracy improvement was proportional to the square root of the number of participating nodes towards the limit of the ranging error. Per experiment outcomes of a 10-node UWB DWN, our Wi-Fi/UWB ensemble reduced the baseline Wi-Fi K-nearest neighbors (KNN) fingerprint localization error by up to 69.8 %, further validating our theoretical and simulation results.

A systematic investigation of four ports MIMO antenna depending on flexible material for UWB networks

A flexible quad-port MIMO antenna with good isolation features with both flat and bending configurations is presented and investigated in this work. The single unit of the MIMO is composed of a crescent-shaped monopole antenna connected with a curved coplanar waveguide (CPW) fed to enhance the operating bandwidth. A thin and flexible Roger 3003 material with thickness = 0.13 mm, εr = 3, and tan δ = 0.001 is used. To improve the isolation between ports which in turn improves the performance of the MIMO system, the single unit antenna is repeated four times and placed orthogonal to each other. A 54 mm × 54 mm × 0.13 mm (0.63λo × 0.63λo × 0.0015λo @ 3.5 GHz) is the total size of the quad ports MIMO antenna. The flexible MIMO antennas in both flat and bending layouts are simulated, tested and the outcomes achieved S11 < − 10 dB from 3.5 GHz up to 11 GHz with mutual coupling ≤ − 17 dB between ports. The radiation patterns of the MIMO antenna are tested with 5 dB peak gain and with semi-omnidirectional and bidirectional patterns in both two planes. The Diversity Gain (DG) values ≥ 9.9 dB through the designed working band, Envelop Correlation Coefficient (ECC) lower than 0.03 from 3.5 GHz to 4 GHz and lower than 0.01 from 4 to 11 GHz, and Channel Capacity Loss (CCL) value ≤ 0.5 bit/s/Hz over the worked band are calculated and extracted in flat and bending configurations and achieved suitable values which support the suggested antenna in the UWB flexible networks.

Low complexity M‐PPM impulse‐radio ultra wideband over fiber system for wireless sensor networks applications

Ultra wideband over fiber (UWBoF) systems have been proposed to extend wireless range and to interconnect stand‐alone UWB networks. These systems have focused on high‐data‐rate applications. However, UWB will be a key enabler for low‐data‐rate wireless sensor network (WSN) deployments. In this letter, a low‐cost and low‐complexity M‐ary pulse position modulation (PPM) impulse radio (IR)‐UWBoF system designed for WSNs applications is proposed. A spectral line‐suppressive convolutional code is used to achieve spectral line suppression in the power spectral density (PSD). Experimental results show that the system does not distort or add spectral lines to the IR‐UWB signal PSD transmitted over 30 km of a single‐mode fiber, thus demonstrating its feasibility to interconnect WSN deployments. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Fuzzy Logic Control Based Dynamic Channel Allocation of WiMedia UWB Networks for Supporting Mixed Data Traffic

Fuzzy Logic Control Based Dynamic Channel Allocation of WiMedia UWB Networks for Supporting Mixed Data Traffic

Swarm intelligent approaches to auto-localization of nodes in static UWB networks

In this paper, we address the problem of localizing sensor nodes in a static network, given that the positions of a few of them (denoted as “beacons“) are a priori known. We refer to this problem as “auto-localization.” Three localization techniques are considered: the two-stage maximum-likelihood (TSML) method; the plane intersection (PI) method; and the particle swarm optimization (PSO) algorithm. While the first two techniques come from the communication-theoretic “world,” the last one comes from the soft computing “world.” The performance of the considered localization techniques is investigated, in a comparative way, taking into account (i) the number of beacons and (ii) the distances between beacons and nodes. Since our simulation results show that a PSO-based approach allows obtaining more accurate position estimates, in the second part of the paper we focus on this technique proposing a novel hybrid version of the PSO algorithm with improved performance. In particular, we investigate, for various population sizes, the number of iterations which are needed to achieve a given error tolerance. According to our simulation results, the hybrid PSO algorithm guarantees faster convergence at a reduced computational complexity, making it attractive for dynamic localization. In more general terms, our results show that the application of soft computing techniques to communication-theoretic problems leads to interesting research perspectives.

An Energy Efficient Multimedia Streaming Scheme in WiMedia Networks

The salient features of UWB 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.

On-body TOA-based ranging error model for motion capture applications within wearable UWB networks

We present herein an error model that characterizes on-body range measurements based on time of arrival (TOA) estimation in Impulse radio-ultra wideband, wireless body area networks. Considering real channel measurements over two representative on-body links for repeated walk cycles, the model is drawn as a conditional mixture, accounting for signal to noise ratio (SNR) variations and non line of sight (NLOS) channel obstructions caused by the body. Key model parameters are then investigated as a function of the previous obstruction and SNR configurations, illustrating missed/false path detection effects at low SNR. On this occasion, two TOA estimators are compared, namely a strongest path detection scheme through matched filtering and a first path detection scheme relying on high-resolution channel estimation. Finally, we discuss the possibility to generalize the previous model to any kind of on-body link, based on empirical observations regarding the dynamic range of the channel power transfer function under mobility. Accordingly, the resulting final model could integrate basic elements of classification, such as the instantaneous LOS/NLOS and static/dynamic link status.

Minimum Interference in UWB and WiFi Networks

Due to the key property of UWB communications: short transmission range, the communication between different UWB devices sometimes needs the help of relay devices. We studied a hybrid wireless network including UWB devices and WiFi devices together. We analyzed the interference of the network and introduced a new reasonable interference definition in the hybrid environment. We proposed an optimal algorithm to reduce the interference of network. Extensive simulations have been conducted to evaluate the performance of the proposed algorithms. The simulation results show that the new proposed algorithm make the interference of the network minimum and improve the throughput of the network.

MAC Layer Throughput Estimation in Impulse-Radio UWB Networks

The inherent channel characteristics of impulse-based UWB networks affect the MAC layer performance significantly. Most previous studies on evaluating MAC protocols are based on prolonged simulations and do not account for the multiple access interference due to multipath delay spread. In this work, we develop CTU, an analytical framework for Capturing the Throughput dependencies in UWB networks, while taking into account the PHY layer effects. The key attributes of CTU are: 1) It is modular; it can be easily modified to provide a basis for evaluating a wide range of MAC protocols for impulse-based UWB networks. The only requirements are that the MAC protocol under study be based on time-hopping and the modulation scheme be pulse position modulation; these are common design decisions in UWB networks. 2) It considers the channel characteristics in addition to MAC layer effects; CTU correlates probabilistically the multipath delay profile of the channel with the packet error rate. We employ CTU to evaluate the performance of different generic medium access procedure. We compare the results with those from extensive simulations and show the high accuracy of CTU. We use CTU to assess the impact of various system parameters on the MAC layer performance; we make several interesting observations that are discussed in depth.

Spatial Capacity of UWB Networks with Space-Time Focusing Transmission

Space-time focusing transmission in impulse-radio ultra-wideband (IR-UWB) systems resorts to the large number of resolvable paths to reduce the interpulse interference as well as the multiuser interference and to simplify the receiver design. In this paper, we study the spatial capacity of IR-UWB systems with space-time focusing transmission where the users are randomly distributed. We will derive the power distribution of the aggregate interference and investigate the collision probability between the desired focusing peak signal and interference signals. The closed-form expressions of the upper and lower bound of the outage probability and the spatial capacity are obtained. Analysis results reveal the connections between the spatial capacity and various system parameters and channel conditions such as antenna number, frame length, path loss factor, and multipath delay spread, which provide design guidelines for IR-UWB networks.

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.

Efficient MAC protocol for ultra-wideband networks

Ultra-wideband communication is a promising enabling technology for future broadband wireless multimedia services. A simple and robust medium-access-control (MAC) protocol is of critical importance to utilize the large bandwidth of UWB channels and to enable numerous new applications and services cost effectively. In this article, we introduce an efficient MAC protocol design for both centralized and distributed multihop UWB networks, based on the exclusive region concept. By reserving a small ER surrounding the receivers to assure successful transmissions, the ER-based MAC protocol can exploit the spatial multiplexing gain of UWB networks and enable multiple users to efficiently and fairly share network resources.

Cross-layer enhanced time scheduling for multi-band OFDM UWB networks

Multi-band Orthogonal Frequency Division multiplexing based Ultra Wide-band (MB-OFDM UWB) technology is one of the strong alternatives for high data rate wireless personal area networks (WPANs) with low power consumption. The capacity of such systems is degraded by multi-path fading, shadowing, multi-user interference and noise. To improve system capacity under these adverse effects, in this paper, we devise cross-layer time scheduling methods, Proportional Time Scheduling with Modiano Algorithm (PTS-MA) and Proportional Time Scheduling with Channel State Information (PTS-CSI), in which scheduling and link adaptation are performed using instantaneous bit error probability (IBEP) estimates obtained through Modiano's algorithm and our novel estimation technique, respectively. We evaluate the performance of the PTS schemes by using numerical experiments. Simulation results suggest PTS-CSI scheduler as the most promising candidate for practical MB-OFDM UWB WPANs with high capacity and fair throughput distribution.

Precoding in OFDM-based multi-antenna ultra-wideband systems

Next-generation ultra-wideband systems will be required to operate in a robust manner over short distances while achieving data rates on the order of gigabits per second. Sophisticated multiantenna techniques can be employed to meet these objectives; in particular, multi-antenna precoding (or beamforming) methods are promising solutions. However, due to the strict power regulations placed on UWB transmissions, conventional precoding techniques are not always suitable for use in UWB networks. In this article we present new theoretical results and practical approaches to performing precoding in OFDM-based multi-antenna UWB systems.

A Low-Overhead Cooperative Retransmission Scheme for IR-UWB Networks

The UWB unique properties such as fine ranging and immunity to small scale fading are utilized in order to exploit the multiuser diversity in UWB networks. The optimal cooperation strategies in the absence of control packet overhead are analyzed in the proactive and reactive settings. It is shown that the proposed method achieves a considerable diversity gain while minimizing the overhead of control packet exchange that is required for coordination among the relays.

Joint Power Adaptation, Scheduling, and Routing for Ultra Wide Band Networks

A general cross-layer optimization problem, to maximize network efficiency (min-max power) of ad-hoc networks, is formulated including power adaptation, scheduling and routing functionalities. The non-convexity of the link capacity, high dimensionality of multi-hop routing and inter-layer interactions among the protocol layers, renders the problem hard. Conversion to an equivalent form, results in two clearly separable sub-problems, demonstrating the functionalities of the protocol layers. This decomposition allows the application of a simple shortest path based algorithm to the high-dimensional routing sub-problem. Further, in the case of UWB networks, the non-convex scheduling & power adaptation sub-problem can be effectively approximated and solved by applying a novel quadratic lower bound to the link capacity function. Using these algorithmic solutions to these sub-problems, an interior point solver generating solutions to the joint UWB network problem is developed. The various simulation results demonstrate interesting characteristics of the optimal routing and scheduling solutions, and provide benchmarks for UWB network design. Comparison with prior information theoretic capacity results, validates the importance of this cross-layer optimization framework

A new binary conflict resolution‐based MAC protocol for impulse‐based UWB ad hoc networks

AbstractUltra wide band (UWB) technology offers a promising high capacity solution for short‐range wireless ad hoc networks, as in home networks or in wearable ad hoc networks. In this paper, we propose a novel multi‐band MAC protocol for use in small ad hoc networks that deploy an underlying UWB based physical layer. In our approach, we divide the available UWB bandwidth into multiple simultaneously usable bands. In the absence of a sophisticated equalizer, the size of a slot for transmitting a UWB pulse is typically dictated by the delay spread of the channel. Therefore, using a wider frequency band to shorten the transmission time for each pulse does not increase the data rate in proportion to the available bandwidth. A multi‐band approach that uses a plurality of bands that adhere to FCC specifications, with slightly elongated pulse durations, provides a solution that can effectively utilize the UWB spectrum. Our approach is based on the idea of conflict resolution using binary ‘something’/‘nothing’ feedback, which has not been widely studied in wireless and specifically in UWB networks. Our protocol unites binary conflict resolution and multi‐band utilization to effectively utilize the available bandwidth. To ensure that our proposed approach is tightly knit with the underlying physical layer, we discuss physical–layer dependencies and the conformance to FCC‐imposed emission limits. We evaluate our approach via extensive simulations. Our simulation results demonstrate the significant advantages of our approach over single‐band solutions: the throughput increases significantly, and the number of collisions decreases considerably. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Adaptive Delayed Acknowledgement Algorithm for MPEG-4 Traffic in UWB Networks

Although ultra-wideband transmission rates are very high in the physical layer, the bandwidth utilization efficiency is very low in the medium access control (MAC) layer. The bandwidth utilization efficiency can be improved and the quality of service for delay-sensitive variable bit rate traffic such as high rate motion picture experts group (MPEG)-4 traffic can be guaranteed by a simple and efficient algorithm that dynamically sets the burst size of the delayed-acknowledgement (Dly-ACK) based on the IEEE 802.15.3 standard. The burst size was adjusted in response to the wireless channel quality. Furthermore, the burst size was bounded by a maximum acknowledgement burst size setting and the remaining number of un-received blocks of a current supra-block. Simulation results show that the method achieves significant performance enhancement in the job failure rate and throughput compared to immediate-acknowledgement (Imm-ACK) and other fixed burst size Dly-ACK schemes. This algorithm can also be applied in generalized time division multiple access (TDMA) systems by using the block acknowledgement mechanism for delay sensitive traffic.

Introducing consciousness in UWB networks by hybrid modelling of admission control

We formalize a model for a self-organizing network of nodes that operate according to the UWB principle based on hybrid modelling formalism. We design the rules that lead to the formation of the network and in particular an admission control procedure that is capable to handle both continuous and discrete perturbations, while maintaining the network in a condition of stability. Cognition is introduced in the model by allowing nodes to adjust their rules of operation based on the perception of the environment by an elected node, serving as the observer, that is aware of context, evaluates, and selects one strategy of operation.