WiFi Links Research Articles

A SURVEY OF LTE WI-FI COEXISTENCE IN UNLICENSED BANDS

With the rapid growth of mobile data, many LTE operators are interested in leveraging unlicensed bands to enhance data rates and user experience. Th is paper investigates the problem of the coexistence of LTE and Wi-Fi in 5 GHz unlicensed bands. We fi rst introduce the current rules for the 5 GHz unlicensed bands and the carrier aggregation technique. We then discuss four deployment scenarios and two LTE-unlicensed (LTE-U) coexistence scenarios. Further, we provide a feature comparison between LTE and Wi-Fi in the PHY/MAC layers, and review the coexistence methods for LTE-U and Wi-Fi without or with the Listen- Before-Talk (LBT) mechanism. Th is paper is concluded by an examination of Wi-Fi link aggregation and in-device coexistence issues.

On Achieving Cyber-Physical Real-Time Snapshot Acquisition in Billboard/Signage Networks

This paper explores a cyber-physical system (CPS) that enables a billboard viewer to instantaneously obtain the snapshot of the displayed media content upon a smartphone gesture. We first define an add-on device mounted to each billboard/signage, called media processing and content access box (MP-CAB), which collaborates with the content management server and the viewers’ smartphones for achieving the desired applications. The detailed design of the MP-CAB will be presented, followed by introducing a simple yet efficient multicast scheduling approach in presence of lossy WiFi link and multiple viewers of heterogeneous receiving modes. We model the response delay of the proposed CPS which jointly considers a set of key parameters, such as file size, percentage of receiver modes, and length of snapshot cycles. Extensive case studies are conducted to provide in-depth analysis and gain insights into the proposed CPS and employed scheduling approach regarding the relationship among several operation parameters. Specifically, we look into the network operation and multicast scheduling settings for achieving minimal expected response delay and maximal image size, aiming to gain sufficient understanding of the behavior of the proposed CPS in the real-time content snapshot acquisition process.

A novel geometric handover model for aerial 4G networks with WiFi‐based X2 interface

AbstractGiven the temporary nature of radio communications for mission critical scenarios, the existing dedicated public safety network lacks the flexibility of cutting edge technologies to leverage on packet data services. In this context, new challenges arise such as high‐capacity demand and low‐latency flexible backhaul connection for public safety users. In this paper, we consider a scenario in which 4G LTE radio coverage is provisioned by aerial eNodeBs installed on low‐altitude platforms raised in the sky and interconnected through WiFi links. We focus our attention on the critical aspect of theThird Generation Partnership Project handover mechanism studying the handover performance using a X2 interfaces over WiFi links. We develop a novel geometric model of the handover in the context of public safety communications but extensible also to other contexts. Relying on such a model, the handover failure probability is computed taking into account the different handover phases. The coverage area of an aerial eNodeB is studied using a suitable air‐to‐ground propagation model, while the average handover duration is computed taking into account the delay introduced by the WiFi communication dynamics. Copyright © 2016 John Wiley & Sons, Ltd.

A Behavioral Adaptive Fuzzy controller of multi robots in a cluster space

Cooperation between autonomous robot vehicles holds several promising advantages like robustness, adaptability, configurability, and scalability. Coordination between the different robots and the individual relative motion represent both the main challenges especially when dealing with formation control and maintenance. Cluster space control provides a simple concept for controlling multi-agent formation. In the classical approach, formation control is the unique task for the multi-agent system. In this paper, the development and application of a novel Behavioral Adaptive Fuzzy-based Cluster Space Control (BAFC) to non-holonomic robots is presented. By applying a fuzzy priority control approach, BAFC deals with two conflicting tasks: formation maintenance and target following. Using priority rules, the fuzzy approach is used to adapt the controller and therefore the behavior of the system, taking into accounts the errors in the formation states and the target following states. The control approach is easy to implement and has been implemented in this paper using SIMULINK real-time platform. The communication between the different agents and the controller is established through Wi-Fi link. Both simulation and experimental results demonstrate the behavioral response where the robot performs the higher priority tasks first. This new approach shows a great performance with a lower control signal when benchmarked with previously known results in the literature.

A wireless Transient Electromagnetic Data Acquisition System based on Virtual Instrument

Electromagnetic survey equipment is widely used in the geophysical field, such as mineral exploration and underground oil detection. To meet the demand of high processing speed and flexible maneuverability, this paper proposes a wireless transient electromagnetic system combined virtual instrument and Wi-Fi technology. Transient electromagnetic receiver and transmitter, Wi-Fi communication links and human operation terminal comprise the whole acquisition system. With the implementation of software programmed by using LabVIEW, the system can process in real-time. This system replaces the old dedicated hardware with compact and flexible device with the same functionality and superior performance.

Computer Vision-Based Portable System for Nitroaromatics Discrimination

A computer vision-based portable measurement system is presented in this report. The system is based on a compact reader unit composed of a microcamera and a Raspberry Pi board as control unit. This reader can acquire and process images of a sensor array formed by four nonselective sensing chemistries. Processing these array images it is possible to identify and quantify eight different nitroaromatic compounds (both explosives and related compounds) by using chromatic coordinates of a color space. The system is also capable of sending the obtained information after the processing by a WiFi link to a smartphone in order to present the analysis result to the final user. The identification and quantification algorithm programmed in the Raspberry board is easy and quick enough to allow real time analysis. Nitroaromatic compounds analyzed in the range of mg/L were picric acid, 2,4-dinitrotoluene (2,4-DNT), 1,3-dinitrobenzene (1,3-DNB), 3,5-dinitrobenzonitrile (3,5-DNBN), 2-chloro-3,5-dinitrobenzotrifluoride (2-C-3,5-DNBF), 1,3,5-trinitrobenzene (TNB), 2,4,6-trinitrotoluene (TNT), and tetryl (TT).

Adaptive interface selection over cloud-based split-layer video streaming via multi-wireless networks

As mobile devices such as tablet PCs and smartphones proliferate, the online video consumption over a wireless network has been accelerated. From this phenomenon, there are several challenges to provide the video streaming service more efficiently and stably in the heterogeneous mobile environment. In order to guarantee the QoS of real-time HD video services, the steady and reliable wireless mesh is necessary. Furthermore, the video service providers have to maintain the QoS by provisioning streaming servers to respond the clients’ request of different video resolution. In this paper, we propose a reliable cloud-based video delivery scheme with the split-layer SVC encoding and real-time adaptive multi-interface selection over LTE and WiFi links. A split-layer video streaming can effectively scale to manage the required channels on each layer of various client connections. Moreover, split-layer SVC model brings streaming service providers a remarkable opportunity to stream video over multiple interfaces (e.g. WiFi, LTE, etc.) with a separate controlling based on their network status. Through the adaptive interface selection, the proposed system aims to ensure the maximizing video quality which the bandwidth of LTE/WiFi accommodates. In addition, the system offers cost-effective streaming to mobile clients by saving the LTE data consumption. In our system, an adaptive interface selection is developed with two different algorithms, such as INSTANT and EWMA methods. We implemented a prototype of mobile client based on iOS particularly by using iPhone5S. Moreover, we also employ the split-layer SVC encodes in streaming server-side as the add-on module to SVC reference encoding tool in a virtualized environment of KVM hypervisor. We evaluated the proposed system in an emulated and a real-world heterogeneous wireless network environments. The results show that the proposed system not only achieves to guarantee the highest quality of video frames via WiFi and LTE simultaneous connection, but also efficiently saves LTE bandwidth consumption for cost-effectiveness to client-side. Our proposed method provides the highest video quality without deadline misses, while it consumes 50.6% LTE bandwidth of ‘LTE-only’ method and 72.8% of the conventional (non-split) SVC streaming over a real-world mobile environment.

A Wi-Fi Cluster Based Wireless Sensor Network Application and Deployment for Wildfire Detection

We introduce the wireless sensor network (WSN) data harvesting application we developed for wildfire detection and the experiments we have performed. The sensor nodes are equipped with temperature and relative humidity sensors. They are organized into clusters and they communicate with the cluster heads using 802.15.4/ZigBee wireless links. The cluster heads report the harvested data to the control center using 802.11/Wi-Fi links. We introduce the hardware and the software architecture of our deployment near Rhodiapolis, an ancient city raising on the outskirts of Kumluca county of Antalya, Turkey. We detail our technical insights into the deployment based on the real-world data collected from the site. We also propose a temperature-based fire detection algorithm and we evaluate its performance by performing experiments in our deployment site and also in our university. We observed that our WSN application can reliably report temperature data to the center quickly and our algorithms can detect fire events in an acceptable time frame with no or very few false positives.

Fast and Secure Session Mobility in IMS-based Vertical Handover Scenario

In this paper, the make-before-break handover method is basically considered in order to reduce the SIP (session initiation protocol) session restoration delay due to the interface switching during WiFi-to-3G vertical handover under IMS (IP multimedia subsystem). Actually, the session restoration delay in WiFi-to-3G handover scenario can be dramatically reduced by performing IMS registration and session re-setup beforehand via WiFi link before actual vertical handover. However, the proper SA (security association) setup scheme between MH (mobile host) and P-CSCF (proxy call session control function) should be developed for the successful pre-authenticated registration since the IP address bound to 3G interface has to be used instead of the IP address bound to WiFi interface as the source IP address of the packets that the MH generates. In this paper, we have enhanced SIP header in order to solve this kind of IP address-mismatch problem. That is, a SA setup scheme is proposed for pre-authenticated registration in WiFi-to-3G handover scenario. We also define IMS handover delay as the sum of authenticated registration delay and session re-setup delay occurring under IMS-based vertical handover. We finally show that this delay reduced by the proposed scheme is acceptable enough to provide delay-sensitive real-time services. Moreover, the modification is deployed only at MH and P-CSCF, which is independent of other party’s network as well as the CSCFs in MH’s HN (home network).

Red Swarm: Reducing travel times in smart cities by using bio-inspired algorithms

This article presents an innovative approach to solve one of the most relevant problems related to smart mobility: the reduction of vehicles’ travel time. Our original approach, called Red Swarm, suggests a potentially customized route to each vehicle by using several spots located at traffic lights in order to avoid traffic jams by using V2I communications. That is quite different from other existing proposals, as it deals with real maps and actual streets, as well as several road traffic distributions. We propose an evolutionary algorithm (later efficiently parallelized) to optimize our case studies which have been imported from OpenStreetMap into SUMO as they belong to a real city. We have also developed a Rerouting Algorithm which accesses the configuration of the Red Swarm and communicates the route chosen to vehicles, using the spots (via WiFi link). Moreover, we have developed three competing algorithms in order to compare their results to those of Red Swarm and have observed that Red Swarm not only achieved the best results, but also outperformed the experts’ solutions in a total of 60 scenarios tested, with up to 19% shorter travel times.

Letter to the Editor Re: the iPad Tablet Computer for Mobile On-Call Radiology Diagnosis? Auditing Discrepancy in CT and MRI Reporting

Letter to the Editor Re: the iPad Tablet Computer for Mobile On-Call Radiology Diagnosis? Auditing Discrepancy in CT and MRI Reporting

Sensabot: A Safe and Cost-Effective Inspection Solution

Young Technology Showcase In response to the oil and gas industry’s need to improve productivity while managing health, safety, and environmental (HSE) risks, Carnegie Mellon University’s National Robotics Engineering Center (NREC) developed and launched Sensabot, a mobile robot that it says can safely and cost-effectively inspect and monitor hazardous and remote production facilities. The robot performs the same inspection and reporting tasks that humans do, such as monitoring the condition and performance of production equipment and areas, but without the risk associated with workers becoming exposed to hazardous conditions. The robot’s ability to operate in flammable and explosive conditions and its mobility distinguishes it from current energy industry inspection technology. It provides the monitoring and reporting capabilities of separate stationary instrumentation and also can respond to dynamic situational conditions. The primary business incentive for using this robot is the alleviation of HSE risk, as well as the reduction of logistic and manpower costs associated with worker-performed inspections. Also, because the robot offers a variety of sensor capabilities, the facility operator can reduce the number of fixed sensors at the site, and the cost and risk associated with workers installing and maintaining these sensors. While this robot requires regular maintenance, it can be performed in safe and well-equipped workshops. Robot Technology and Specifications This robot is designed to meet Inter-national Electrotechnical Commission (IECEx) standards for electronic equipment operating in flammable and explosive environments. The robot design also complies with NACE MR0175/ISO 15156, the standard for materials used in H2S-containing environments in oil and gas production. The robot meets the American National Standards Institute safety standards for guided industrial vehicles and industry standard for human factors engineering guidelines. The robot is a battery-powered machine controlled by a human operator through a remote Wi-Fi link and joysticks. The complete robot system also includes infrastructure components, such as a customized dumbwaiter elevator and a cog rail ladder for cost-effective integration into multilevel production facilities such as drilling rigs and refineries.

Avoiding the Rush Hours: WiFi Energy Management via Traffic Isolation

WiFi continues to be a prime source of energy consumption in mobile devices. This paper observes that, despite a rich body of research in WiFi energy management, there is room for improvement. Our key finding is that WiFi energy optimizations have conventionally been designed with a single AP in mind. However, network contention among different APs can dramatically increase a client's energy consumption. Each client may have to keep awake for long durations before its own AP gets a chance to send it packets to it. As AP density increases, the waiting time inflates, resulting in a proportional decrease in battery life. We design SleepWell, a system that achieves energy efficiency by evading network contention. The APs regulate the sleeping window of their clients in a way that different APs are active/inactive during nonoverlapping time windows. The solution is analogous to the common wisdom of going late to office and coming back late, thereby avoiding the rush hours. We implement SleepWell on a testbed of eight Laptops and nine Android phones, and evaluate it over a wide variety of scenarios and traffic patterns. Results show a median gain of up to 2x when WiFi links are strong; when links are weak and the network density is high, the gains can be even more.

Splitting downlink multimedia traffic over WiMAX and WiFi heterogeneous links based on airtime‐balance

AbstractWe investigate the challenge of splitting a traffic flow over WiMAX and WiFi links. For traffic load distribution over heterogeneous RATs (Radio Access Technologies), heterogeneous link resources need to be commonly measured and fairly compared. To this end, an airtime cost model is considered as a common resource measure. The model can be used to estimate channel time consumed for a successful packet transmission. As a traffic split mechanism, an airtime‐balance method is proposed. Using the airtime cost model, the offered traffic load (in Mbps) is converted into airtime cost required for its transmission, and IP packets are distributed to multiple RATs so that airtime is equally balanced between RATs.We have implemented a practical test‐bed system, including both WiMAX and WiFi systems, and used it to conduct extensive experiments indoor and outdoor. Experimental results confirm that airtime‐balance can achieve an improved flow split to reduce the waiting packets at the reorder buffer of the receiver. Moreover, it could realize a more rapid adaptation to link variations with local measurements, when compared to the RTT‐based method, which also requires extra system overhead due to the use of probe packets. Copyright © 2010 John Wiley & Sons, Ltd.

Wireless Tag and Reader Module Design for AutomatedHand Hygiene Documentation and Reminder System inHospitals

This paper presents a design of a wireless tag and wireless reader for the automated hand hygiene documentation and reminder system (AHHDRS). This system addresses the problem of healthcare associated infections mainly caused by lack of hand hygiene among clinicians and costs $35.7-$45 billion annually in direct medical costs to the U.S hospitals alone. AHHDRS works by creating ultrasonic hotspots with unique Identifier which can be ultrasonically tagged into the wireless Tag based on clinician's movement among hotspots. Correct movement of the clinicians with Tag among the Wash zone/Bed zone hot spots ensures hand hygiene compliance. Tag accumulates the compliance data and periodically transfers it to the wireless reader through 915MHz RF link. Wireless reader consolidates compliance data from Tags in its vicinity and sends it to hand hygiene server through Wi-Fi link. Hand hygiene server processes and reports compliance data and stores for future reference.

RAIS: a real time strong-motion network in northern Italy

When compared to more seismically active regions, damaging earthquakes occur only occasionally in the central part of northern Italy. Nevertheless, the lack of a dense strong-motion network in this area was highlighted by the occurrence of the November 24, 2004, ML 5.2, Salo earthquake. In 2006, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) section of Milano-Pavia began the installation of new strong-motion stations in central-northern Italy. At present, the Strong-Motion Network of Northern Italy (RAIS; Rete Accelerometrica Italia Settentrionale) includes 22 stations with an average inter-distance of about 20 km. All of the stations are equipped with Kinemetrics Episensor FBA ES-T sensors coupled with 24-bit digital recorders. Starting from 2009, 14 strong-motion stations have been sending data to the INGV acquisition center in Milan, in real time using TCP/IP over wi-fi links. Another eight stations still work in dial-up mode and send data through GSM modems. The real-time connections allow the use of strong-motion data recorded by RAIS for the generation of shake maps for Italy, the implementation of which represents one of the main tasks of the last agreement between INGV and the Italian Civil Protection Department. The RAIS data is stored directly at the INGV section of Milano-Pavia, which was realized using the MiniSEED format: the data management and exchange are carried out by the SeisComP package with the SeedLink protocol. Metadata dissemination is achieved through the website http://rais.mi.ingv.it, where the strong-motion parameters related to each recorded and processed waveform are made available.

A Dynamic Multimedia User-Weight Classification Scheme for IEEE_802.11 WLANs

In this paper we expose a dynamic traffic-classification scheme to support multimedia applications such as voice and broadband video transmissions over IEEE 802.11 Wireless Local Area Networks (WLANs). Obviously, over a Wi-Fi link and to better serve these applications - which normally have strict bounded transmission delay or minimum link rate requirement - a service differentiation technique can be applied to the media traffic transmitted by the same mobile node using the well-known 802.11e Enhanced Distributed Channel Access (EDCA) protocol. However, the given EDCA mode does not offer user differentiation, which can be viewed as a deficiency in multi-access wireless networks. Accordingly, we propose a new inter-node priority access scheme for IEEE 802.11e networks which is compatible with the EDCA scheme. The proposed scheme joins a dynamic user-weight to each mobile station depending on its outgoing data, and therefore deploys inter-node priority for the channel access to complement the existing EDCA inter-frame priority. This provides efficient quality of service control across multiple users within the same coverage area of an access point. We provide performance evaluations to compare the proposed access model with the basic EDCA 802.11 MAC protocol mode to elucidate the quality improvement achieved for multimedia communication over 802.11 WLANs.

Monitoring continuous k-nearest neighbor queries in the hybrid wireless network

In a mobile/pervasive computing environment, one of the most important goals of monitoring continuous spatial queries is to reduce communication cost for location-updates. Existing work uses many cellular wireless connections, which would easily become the performance bottleneck of the overall system. This paper introduces a novel continuous kNN query monitoring method to reduce communication cost in the hybrid wireless network, where the moving objects in the wireless broadcasting system construct the ad-hoc network. Simulation results prove the efficiency of the proposed method, which leverages the wireless broadcasting channel as well as the WiFi link to alleviate the burden on the cellular uplink communication cost.

Tool release

We are pleased to announce the release of a tool that records detailed measurements of the wireless channel along with received 802.11 packet traces. It runs on a commodity 802.11n NIC, and records Channel State Information (CSI) based on the 802.11 standard. Unlike Receive Signal Strength Indicator (RSSI) values, which merely capture the total power received at the listener, the CSI contains information about the channel between sender and receiver at the level of individual data subcarriers, for each pair of transmit and receive antennas. Our toolkit uses the Intel WiFi Link 5300 wireless NIC with 3 antennas. It works on up-to-date Linux operating systems: in our testbed we use Ubuntu 10.04 LTS with the 2.6.36 kernel. The measurement setup comprises our customized versions of Intel's close-source firmware and open-source iwlwifi wireless driver, userspace tools to enable these measurements, access point functionality for controlling both ends of the link, and Matlab (or Octave) scripts for data analysis. We are releasing the binary of the modified firmware, and the source code to all the other components.

Feedback-based traffic splitting for wireless terminals with multi-radio devices

It is expected that a number of heterogeneous radio access technologies will be available simultaneously at a single wireless terminal in next generation wireless networks. This paper addresses the challenge of link aggregation in a wireless terminal with multi-radio devices. A major issue in multi-path transmission is how to reduce the additional reordering delay at the receiver, which is mainly caused by the difference between link delays. This is particularly critical in wireless environments due to dynamics in link quality. Motivated by this observation, we propose a feedback-based technique to determine split ratios adaptively, based on measurements at the receiver. The link-level packet delay is measured on a periodic basis. The measurement is conveyed to the sender, and is used for split ratio calculation. The proposed technique has been implemented into an actual test-bed network which includes WiMAX and WiFi systems, and its potential usefulness is extensively evaluated. It was experimentally verified that for given radio link conditions, the traffic split ratio between WiMAX and WiFi links is optimally converged.