Search

A next-generation network (NGN) is an advanced network that exploits multiple broadband and QoS-enabled transport technologies to provide telecommunication services. The principles and requirements of convergence of wireless sensor networks are likely to deliver all the desired benefits of NGN and should be carefully studied. In this paper, we focus on the power consumption topic, which is a fundamental concern in wireless multimedia sensor networks (WMSNs). Node placement in WMSNs has considerable impact on network lifetime. In this paper, we have investigated and developed a power-efficient node placement scheme (PENPS) in linear WMSNs, which can minimize the average energy consumption per node and maximize the network lifetime. The analysis of PENPS and the comparison of performance with the equal-spaced placement scheme (EPS) show that PENPS scheme can significantly decrease the average energy consumption per node, which can prolong the lifetime of sensor nodes and sensor networks effectively. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The two-dimensional (2-D) integrated planar microlens (PML) is expected to be used in connection with various 2-D devices in parallel optical fiber communication systems. In this paper, we demonstrate recent progresses made for PML and its light coupling Characteristics. The coupling characteristics between (1) LD and single-mode fiber, (2) LED and GI-50 fiber, (3) single-mode fiber and single-mode fiber, and (4) single-mode fiber and detector were evaluated. In this paper, we evaluate coupling characteristics corresponding to single lens in an array. [ABSTRACT FROM AUTHOR]

This paper addresses the issues on spectrum sharing in a cognitive radio network consisting of a primary user and a group of cognitive users. Each cognitive user may occupy a non-overlapped sub-band of the primary spectrum, but it needs to perform spectrum sensing independently before accessing the sub-band. To reduce the complexity of spectrum sensing and thus energy consumption, this paper proposes a scheduled spectrum sensing scheme. First, we consider a single spectrum sensing scenario where only one cognitive user is elected to perform spectrum sensing, and then it broadcasts its sensing results to the other cognitive users. The scheduled spectrum sensing scheme works in both network-centric and user-centric ways. Next, the scheduled spectrum sensing scheme is further generalized to work in a multiple spectrum sensing scenario. The results show the effectiveness of the proposed schemes compared with the traditional schemes where all cognitive users may perform spectrum sensing at the same time. Copyright © 2010 John Wiley & Sons, Ltd. This paper proposes a scheduled spectrum sensing scheme for spectrum sharing in a cognitive radio network consisting of a primary user and a group of cognitive users. Both single and multiple scheduled spectrum sensing schemes are considered. The results show that in general the proposed scheduling schemes are more efficient than the extreme case in terms of the number of sensing operations required with a given sum false alarm probability and the sum-missed detection probability. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: This paper presents the design, testing, and validation of a ultra‐wideband (UWB) wireless solution to replace wired intra‐spacecraft communications with wireless communications. The system requirements are provided in the framework of the Eu:CROPIS mission and the wired intra‐spacecraft communication system is replaced with a two‐segment wireless network. As such, distinct sets of UWB gateways and nodes are prototyped to interface with the on‐board entities and properly handle the data transmission in the resulting spacecraft and payload wireless networks. To accomplish these tasks, a custom radio module integrated into the prototypes was designed to provide the appropriate UWB RF front‐end and run a custom‐built communication stack. The viability of the solution was tested in laboratory conditions. For the test scenarios, sensor data are acquired in the payload network and forwarded as SpaceWire packets over the spacecraft network. Experimental test results indicate the suitability of the proposed solution in terms of delay and data integrity for implementing intra‐spacecraft wireless communications. [ABSTRACT FROM AUTHOR]

The M-sequence (maximum length sequence) is often used as a ranging signal in radar and other systems. This paper considers the case where an M sequence ranging signal is detected by an MPD (matched pulse detector), which is a digital correlator, and analyzes the probabilities for miss detection and for false detection due to bit error. Previously, this correlation function has not been derived analytically. In this paper, a procedure is presented where the threshold for the miss detection and false detection probabilities is determined by a simulation result for the correlator. An experiment is attempted in which a single M-sequence is detected in satellite communication using VSAT (very small aperture terminal). It is shown that the experimental results and analysis almost agree for a single M-sequence with a 31-bit code length. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 82(2): 82–89, 1999 [ABSTRACT FROM AUTHOR]

This paper proposes the differential detection type direct sequence/code-division multiple-access (DS/CDMA) adaptive interference canceller (AIC) that can track the fast fading. The proposed AIC is composed of the fractionally chip-spaced code-orthogonalizing filter (COF) with tap length corresponding to several bit periods and the differential detector. The COF makes adaptively the tap weight orthogonal to all spreading codes of other users as a despreading code of the desired user so that the interferences from other users are cancelled and the signal component of the desired user is extracted. The differential detector compensation the carrier phase variation due to finding in the desired user's signal at the COF output. By such a structure, the tracking performance of AIC to the channel variation can be improved to the limit of the tracking performance of the differential detector. This paper evaluates the basic ability of the proposed AIC in the fast-fading channel. The AIC is especially expected to be utilized in the DS/CDMA mobile communications since the receiver is of the signle-user type, where no information concerning other users is needed. [ABSTRACT FROM AUTHOR]

Protecting implemented security mechanisms and trusting their output (e.g. log files) when the host, under which they are deployed, is compromised, is among the major challenges that have to be faced. To fulfil this need, recent advances in security have considered the design of storage-based intrusion detection system, which detect intrusions by looking at the low-level disk requests patterns. However, these systems neither tolerate intrusions, nor do they distinguish whether the disk requests are generated by legitimate or malicious processes; and consequently, they generate a lot of false negative and positive alerts. In this paper, we present a Cooperative Intrusion Detection and Tolerance System, called CIDTS, which takes advantage of the information that are available at the network, host operating system, and storage level to better detect intrusion attempts in their early stages, even when the host is compromised. To allow cooperation, the disk communication interface that transports requests between the storage level and the host level is extended to forward information about the processes that generate the request. The paper also provides intrusion tolerance capabilities and provides techniques to support investigation activities. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Wireless sensor networks (WSNs) are well suited to many applications, including environment surveillance and target tracking. ZigBee is an IEEE 802.15.4-based standard that is considered suitable for WSNs. The functional operations of a ZigBee network rely on self-organized network connections and the proper deployment of sensor devices. However, the devices comprising a ZigBee network may become isolated from the network after the joining phase due to the configuration constraints of the ZigBee standard. This means that some deployed devices cannot join the network even though they can communicate with other joined nodes. These isolated devices reduce the efficiency of network operation and increase deployment costs. This paper proposes a ZigBee-compatible adaptive joining mechanism with connection shifting schemes to improve the connectivity of ZigBee networks, allowing them to operate at the expected efficiency. Simulation results show that the proposed mechanism significantly improves the join ratio of deployed sensor devices in ZigBee WSNs. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

One of the fundamental and important operations in sensor networks is sink–source matching, i.e. target detection. Target detection is about how a sink finds the location of source nodes observing the event of interest (i.e. target activity). This operation is very important in many sensor network applications such as military battlefield and environment habitats. The mobility of both targets and sinks brings significant challenge to target detection in sensor networks. Most existing approaches are either energy inefficient or lack of fault tolerance in the environment of mobile targets and mobile sinks. Motivated by these, we propose an energy-efficient line proxy target detection (LPTD) approach in this paper. The basic idea of LPTD is to use designated line proxies as rendezvous points (or agents) to coordinate mobile sinks and mobile targets. Instead of having rendezvous nodes for each target type as used by most existing approaches, we adopt the temporal-based hash function to determine the line in the given time. Then the lines are alternated over time in the entire sensor network. This simple temporal-based line rotation idea allows all sensor nodes in the network to serve as rendezvous points and achieves overall load balancing. Furthermore, instead of network-wide flooding, interests from sinks will be flooded only to designated line proxies within limited area. The interest flooding can further decrease if the interest has geographical constraints. We have conducted extensive analysis and simulations to evaluate the performance of our proposed approach. Our results show that the proposed approach can significantly reduce overall energy consumption and target detection delay. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

With the advance of sensing technologies and their applications, advanced sensor networks are gaining increasing interest. For certain sensitive applications, heterogeneous sensors can be deployed in the monitored space to ensure scalability, high-speed communication, and long network lifetime. Hybrid sensor networks have capabilities to combine the use of both resource-rich and resource-impoverished sensor nodes. This paper proposes a heterogeneous broadband sensor network architecture for military vehicle tracking. Powerful sensor devices with good bandwidth and energy capabilities are used as a communication backbone while energy sensors are used to track moving targets. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper considers the concept of an MSCS (metastable information communications system) for remote transmission of measured data with gradual variations of the transmission frame cycle and proposes a signal integration method for improvement of the transmission characteristics. Based on the proposed method, a signal integration algorithm for a system remotely transmitting measured sensor data from on board a moving body is derived. An improvement of the received SNR (signal-to-noise ratio) is demonstrated by simulation. As a specific example, the integration effect and limitation of the number of integrations determined by the relationship between the error ellipse and the speed of movement is derived with a GPS as a measurement sensor. An example result includes a maximum of 7 integrations for an allowable error of ±16 m for the GPS sensor measurement, a frame period of 1 s, and a speed of movement of 2.5 m/s, with the bit error rate improved by 8 dB when the input SNR is 0 dB. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(3): 44–52, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20154 [ABSTRACT FROM AUTHOR]

An increase in the size of on-board antenna reflectors is a key technology in providing economical services by miniaturized portable equipment in future mobile satellite communication systems. In practice, a mesh antenna can be used as the on-board antenna. However, since the reflector surface of this antenna is supported by the cable and the mesh, and its size is larger, the surface is subject to larger thermal deformation in orbit than is the solid antenna reflector. Conventional compensation methods such as passive thermal control or rotation of the antenna reflector cannot maintain the required antenna performances. Various methods have been reported to compensate for the deterioration of antenna performance by thermal deformation. This paper describes a static shape control system for a 10-m diameter antenna which actively compensates for the deformation by using a shape-measuring sensor and shape-compensation actuator. The configuration of the sensor and the experimental results by a functional model are described to confirm the design validity. The shape-compensation method by the actuator was cone firmed to be useful in achieving a required surface accuracy. [ABSTRACT FROM AUTHOR]

A new procedure for obtaining the equivalent currents on a plane surface from spherical near field measurements is proposed. It uses the modal expansion in spherical waves and the plane wave spectrum to achieve the objective. Some results using real measurements are shown. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2043–2047, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22575 [ABSTRACT FROM AUTHOR]

A neural processing-type optical wavelength division multiplexing (WDM) demultiplexer (NP-ODEMUX), which consists of diffraction grating, detector array, and neural network LSI, is proposed in order to improve receiver sensitivity while maintaining flexible demultiplexing characteristics. In previous work, a neural processing-type optical WDM demultiplexer using a multimode optical waveguide was proposed. This conventional NP-ODEMUX and the proposed grating-type NP-ODEMUX are compared using power penalty calculation simulations. The results show that receiver sensitivity is improved using the proposed grating-type NP-ODEMUX. Also, a standard diffraction grating demultiplexer without neural processing is compared with the proposed NP-ODEMUX using power penalty and it is shown that the proposed NP-ODEMUX can demultiplex WDM signals without degrading receiver sensitivity. Next, the results of the demultiplexing experiment for six-channel WDM signal which has been directly modulated at 150 Mb/s using nonreturn to zero (NRZ) pseudorandom signal by grating-type NP-ODEMUX prototype are described. Bit-error rate measurement for both the conventional diffraction grating demultiplexer and the grating-type NP-ODEMUX using neural processing for the unequally spaced WDM signals revealed that the receiver sensitivity can be greatly improved and that it can flexibly compensate wavelength change. [ABSTRACT FROM AUTHOR]

The terahertz gap (0.1‐10 THz) is an attractive frequency band for new applications. In wireless communication, it can serve as a high capacity link. The lack in use of that gap exists due to a lack of available commercial communications technology systems in that region. We have found that neon indicator lamps or glow discharge detectors (GDD) can be used as simple and very inexpensive detectors in that frequency gap. In modern modulation techniques, the signal phase should be recovered. This article is a proof of concept of detection of quadratic amplitude modulated millimeter‐wave signals by a GDD and photodiode using a heterodyne detection method. [ABSTRACT FROM AUTHOR]

We have developed an optical fiber network combining communication and sensing using a hetero-core spliced fiber optic sensor inserted into an existing communication line. The measurement uses the Internet infrastructure effectively, and the sensitivity characteristic by wavelength of the measurement was examined. In addition, six binary switch modules and one displacement sensor module using the hetero-core spliced fiber optic sensor were inserted into an actual communication line, and the influence on the communication was examined. The hetero-core spliced fiber optic sensor showed the characteristic of loss only. When the sensor is inserted into the communication line, if the loss can be controlled to within tolerance to the wavelength of 1.31 μm of the communication line, a measurement function can be added to the communication line by a comparatively simple construction method. In addition, we realized a multiple binary switch measurement in real-time basis with tandem connection by simple addressing algorithm. The binary switches can be applied to a home security system to monitor the state of doors opening and closing. We have successfully fabricated and demonstrated the binary switch sensing system in tandem connection consisting of three binary switches using the proposed method. 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(3): 40–48, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ eej.21021 [ABSTRACT FROM AUTHOR]