Sensors

Research

363 KiB

Open AccessArticle

Toward Sensor-Based Context Aware Systems

by Yoshitaka Sakurai, Kouhei Takada, Marco Anisetti, Valerio Bellandi, Paolo Ceravolo, Ernesto Damiani and Setsuo Tsuruta

Sensors 2012, 12(1), 632-649; https://doi.org/10.3390/s120100632 - 9 Jan 2012

Cited by 18 | Viewed by 8718

Abstract

This paper proposes a methodology for sensor data interpretation that can combine sensor outputs with contexts represented as sets of annotated business rules. Sensor readings are interpreted to generate events labeled with the appropriate type and level of uncertainty. Then, the appropriate context [...] Read more.

This paper proposes a methodology for sensor data interpretation that can combine sensor outputs with contexts represented as sets of annotated business rules. Sensor readings are interpreted to generate events labeled with the appropriate type and level of uncertainty. Then, the appropriate context is selected. Reconciliation of different uncertainty types is achieved by a simple technique that moves uncertainty from events to business rules by generating combs of standard Boolean predicates. Finally, context rules are evaluated together with the events to take a decision. The feasibility of our idea is demonstrated via a case study where a context-reasoning engine has been connected to simulated heartbeat sensors using prerecorded experimental data. We use sensor outputs to identify the proper context of operation of a system and trigger decision-making based on context information. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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479 KiB

Open AccessArticle

Modeling and Analysis of an Energy-Efficient Mobility Management Scheme in IP-Based Wireless Networks

by Ho Young Hwang, Sun-Jong Kwon, Yun Won Chung, Dan Keun Sung and Suwon Park

Sensors 2011, 11(12), 11273-11294; https://doi.org/10.3390/s111211273 - 28 Nov 2011

Cited by 6 | Viewed by 7132

Abstract

An energy-efficient mobility management scheme in IP-based wireless networks is proposed to reduce the battery power consumption of mobile hosts (MHs). The proposed scheme manages seven MH states, including transmitting, receiving, attention/cell-connected, attention/paging area(PA)-connected, idle, off/attached, and detached states, to efficiently manage battery [...] Read more.

An energy-efficient mobility management scheme in IP-based wireless networks is proposed to reduce the battery power consumption of mobile hosts (MHs). The proposed scheme manages seven MH states, including transmitting, receiving, attention/cell-connected, attention/paging area(PA)-connected, idle, off/attached, and detached states, to efficiently manage battery power, radio resources, and network load. We derive the stationary probabilities and steady state probabilities of the seven MH states for the proposed scheme in IP-based wireless networks in compact form. The effects of various input parameters on MH steady state probabilities and power consumption are investigated in the proposed scheme compared to the conventional scheme. Network costs such as cell updates, PA updates, binding-lifetime-based registrations, and paging messages are analyzed in the proposed and conventional schemes. The optimal values of PA size and registration interval are derived to minimize the network cost of the proposed scheme. The combined network and power costs are investigated for the proposed and conventional schemes. The results provide guidelines to select the proper system parameters in IP-based wireless networks. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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853 KiB

Open AccessArticle

Interoperation of an UHF RFID Reader and a TCP/IP Device via Wired and Wireless Links

by Sang Hoon Lee and Ik Soo Jin

Sensors 2011, 11(11), 10664-10674; https://doi.org/10.3390/s111110664 - 8 Nov 2011

Cited by 2 | Viewed by 10756

Abstract

A main application in radio frequency identification (RFID) sensor networks is the function that processes real-time tag information after gathering the required data from multiple RFID tags. The component technologies that contain an RFID reader, called the interrogator, which has a tag chip, [...] Read more.

A main application in radio frequency identification (RFID) sensor networks is the function that processes real-time tag information after gathering the required data from multiple RFID tags. The component technologies that contain an RFID reader, called the interrogator, which has a tag chip, processors, coupling antenna, and a power management system have advanced significantly over the last decade. This paper presents a system implementation for interoperation between an UHF RFID reader and a TCP/IP device that is used as a gateway. The proposed system consists of an UHF RFID tag, an UHF RFID reader, an RF end-device, an RF coordinator, and a TCP/IP I/F. The UHF RFID reader, operating at 915 MHz, is compatible with EPC Class-0/Gen1, Class-1/Gen1 and 2, and ISO18000-6B. In particular, the UHF RFID reader can be combined with the RF end-device/coordinator for a ZigBee (IEEE 802.15.4) interface, which is a low-power wireless standard. The TCP/IP device communicates with the RFID reader via wired links. On the other hand, it is connected to the ZigBee end-device via wireless links. The web based test results show that the developed system can remotely recognize information of multiple tags through the interoperation between the RFID reader and the TCP/IP device. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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201 KiB

Open AccessArticle

Skyline Query Processing in Sensor Network Based on Data Centric Storage

by Seokil Song, Yunsik Kwak and Seokhee Lee

Sensors 2011, 11(11), 10283-10292; https://doi.org/10.3390/s111110283 - 28 Oct 2011

Cited by 2 | Viewed by 5996

Abstract

Data centric storages for sensor networks have been proposed to efficiently process multi-dimensional range queries as well as exact matches. Usually, a sensor network does not process only one type of the query, but processes various types of queries such as range queries, [...] Read more.

Data centric storages for sensor networks have been proposed to efficiently process multi-dimensional range queries as well as exact matches. Usually, a sensor network does not process only one type of the query, but processes various types of queries such as range queries, exact matches and skyline queries. Therefore, a sensor network based on a data centric storage for range queries and exact matches should process skyline queries efficiently. However, existing algorithms for skyline queries have not considered the features of data centric storages. Some of the data centric storages store similar data in sensor nodes that are placed on geographically similar locations. Consequently, all data are ordered in a sensor network. In this paper, we propose a new skyline query processing algorithm that exploits the above features of data centric storages. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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2595 KiB

Open AccessArticle

Improved Kalman Filter Method for Measurement Noise Reduction in Multi Sensor RFID Systems

by Ki Hwan Eom, Seung Joon Lee, Yeo Sun Kyung, Chang Won Lee, Min Chul Kim and Kyung Kwon Jung

Sensors 2011, 11(11), 10266-10282; https://doi.org/10.3390/s111110266 - 28 Oct 2011

Cited by 26 | Viewed by 9017

Abstract

Recently, the range of available Radio Frequency Identification (RFID) tags has been widened to include smart RFID tags which can monitor their varying surroundings. One of the most important factors for better performance of smart RFID system is accurate measurement from various sensors. [...] Read more.

Recently, the range of available Radio Frequency Identification (RFID) tags has been widened to include smart RFID tags which can monitor their varying surroundings. One of the most important factors for better performance of smart RFID system is accurate measurement from various sensors. In the multi-sensing environment, some noisy signals are obtained because of the changing surroundings. We propose in this paper an improved Kalman filter method to reduce noise and obtain correct data. Performance of Kalman filter is determined by a measurement and system noise covariance which are usually called the R and Q variables in the Kalman filter algorithm. Choosing a correct R and Q variable is one of the most important design factors for better performance of the Kalman filter. For this reason, we proposed an improved Kalman filter to advance an ability of noise reduction of the Kalman filter. The measurement noise covariance was only considered because the system architecture is simple and can be adjusted by the neural network. With this method, more accurate data can be obtained with smart RFID tags. In a simulation the proposed improved Kalman filter has 40.1%, 60.4% and 87.5% less Mean Squared Error (MSE) than the conventional Kalman filter method for a temperature sensor, humidity sensor and oxygen sensor, respectively. The performance of the proposed method was also verified with some experiments. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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209 KiB

Open AccessArticle

Cooperative MIMO Communication at Wireless Sensor Network: An Error Correcting Code Approach

by Mohammad Rakibul Islam and Young Shin Han

Sensors 2011, 11(10), 9887-9903; https://doi.org/10.3390/s111009887 - 20 Oct 2011

Cited by 26 | Viewed by 8769

Abstract

Cooperative communication in wireless sensor network (WSN) explores the energy efficient wireless communication schemes between multiple sensors and data gathering node (DGN) by exploiting multiple input multiple output (MIMO) and multiple input single output (MISO) configurations. In this paper, an energy efficient cooperative [...] Read more.

Cooperative communication in wireless sensor network (WSN) explores the energy efficient wireless communication schemes between multiple sensors and data gathering node (DGN) by exploiting multiple input multiple output (MIMO) and multiple input single output (MISO) configurations. In this paper, an energy efficient cooperative MIMO (C-MIMO) technique is proposed where low density parity check (LDPC) code is used as an error correcting code. The rate of LDPC code is varied by varying the length of message and parity bits. Simulation results show that the cooperative communication scheme outperforms SISO scheme in the presence of LDPC code. LDPC codes with different code rates are compared using bit error rate (BER) analysis. BER is also analyzed under different Nakagami fading scenario. Energy efficiencies are compared for different targeted probability of bit error p_b. It is observed that C-MIMO performs more efficiently when the targeted p_b is smaller. Also the lower encoding rate for LDPC code offers better error characteristics. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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2128 KiB

Open AccessArticle

An Approach for Removing Redundant Data from RFID Data Streams

by Hairulnizam Mahdin and Jemal Abawajy

Sensors 2011, 11(10), 9863-9877; https://doi.org/10.3390/s111009863 - 20 Oct 2011

Cited by 38 | Viewed by 8861

Abstract

Radio frequency identification (RFID) systems are emerging as the primary object identification mechanism, especially in supply chain management. However, RFID naturally generates a large amount of duplicate readings. Removing these duplicates from the RFID data stream is paramount as it does not contribute [...] Read more.

Radio frequency identification (RFID) systems are emerging as the primary object identification mechanism, especially in supply chain management. However, RFID naturally generates a large amount of duplicate readings. Removing these duplicates from the RFID data stream is paramount as it does not contribute new information to the system and wastes system resources. Existing approaches to deal with this problem cannot fulfill the real time demands to process the massive RFID data stream. We propose a data filtering approach that efficiently detects and removes duplicate readings from RFID data streams. Experimental results show that the proposed approach offers a significant improvement as compared to the existing approaches. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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2193 KiB

Open AccessArticle

Authenticity Preservation with Histogram-Based Reversible Data Hiding and Quadtree Concepts

by Hsiang-Cheh Huang and Wai-Chi Fang

Sensors 2011, 11(10), 9717-9731; https://doi.org/10.3390/s111009717 - 13 Oct 2011

Cited by 45 | Viewed by 7561

Abstract

With the widespread use of identification systems, establishing authenticity with sensors has become an important research issue. Among the schemes for making authenticity verification based on information security possible, reversible data hiding has attracted much attention during the past few years. With its [...] Read more.

With the widespread use of identification systems, establishing authenticity with sensors has become an important research issue. Among the schemes for making authenticity verification based on information security possible, reversible data hiding has attracted much attention during the past few years. With its characteristics of reversibility, the scheme is required to fulfill the goals from two aspects. On the one hand, at the encoder, the secret information needs to be embedded into the original image by some algorithms, such that the output image will resemble the input one as much as possible. On the other hand, at the decoder, both the secret information and the original image must be correctly extracted and recovered, and they should be identical to their embedding counterparts. Under the requirement of reversibility, for evaluating the performance of the data hiding algorithm, the output image quality, named imperceptibility, and the number of bits for embedding, called capacity, are the two key factors to access the effectiveness of the algorithm. Besides, the size of side information for making decoding possible should also be evaluated. Here we consider using the characteristics of original images for developing our method with better performance. In this paper, we propose an algorithm that has the ability to provide more capacity than conventional algorithms, with similar output image quality after embedding, and comparable side information produced. Simulation results demonstrate the applicability and better performance of our algorithm. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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924 KiB

Open AccessArticle

Coexistence of WiFi and WiMAX Systems Based on PS-Request Protocols

by Jongwoo Kim, Suwon Park, Seung Hyong Rhee, Yong-Hoon Choi, Young-uk Chung and Ho Young Hwang

Sensors 2011, 11(10), 9700-9716; https://doi.org/10.3390/s111009700 - 13 Oct 2011

Cited by 3 | Viewed by 8580

Abstract

We introduce both the coexistence zone within the WiMAX frame structure and a PS-Request protocol for the coexistence of WiFi and WiMAX systems sharing a frequency band. Because we know that the PS-Request protocol has drawbacks, we propose a revised PS-Request protocol to [...] Read more.

We introduce both the coexistence zone within the WiMAX frame structure and a PS-Request protocol for the coexistence of WiFi and WiMAX systems sharing a frequency band. Because we know that the PS-Request protocol has drawbacks, we propose a revised PS-Request protocol to improve the performance. Two PS-Request protocols are based on the time division operation (TDO) of WiFi system and WiMAX system to avoid the mutual interference, and use the vestigial power management (PwrMgt) bit within the Frame Control field of the frames transmitted by a WiFi AP. The performance of the revised PS-Request protocol is evaluated by computer simulation, and compared to those of the cases without a coexistence protocol and to the original PS-Request protocol. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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466 KiB

Open AccessArticle

The Design of RFID Conveyor Belt Gate Systems Using an Antenna Control Unit

by Chong Ryol Park, Seung Joon Lee and Ki Hwan Eom

Sensors 2011, 11(9), 9033-9044; https://doi.org/10.3390/s110909033 - 21 Sep 2011

Cited by 5 | Viewed by 10825

Abstract

This paper proposes an efficient management system utilizing a Radio Frequency Identification (RFID) antenna control unit which is moving along with the path of boxes of materials on the conveyor belt by manipulating a motor. The proposed antenna control unit, which is driven [...] Read more.

This paper proposes an efficient management system utilizing a Radio Frequency Identification (RFID) antenna control unit which is moving along with the path of boxes of materials on the conveyor belt by manipulating a motor. The proposed antenna control unit, which is driven by a motor and is located on top of the gate, has an array structure of two antennas with parallel connection. The array structure helps improve the directivity of antenna beam pattern and the readable RFID distance due to its configuration. In the experiments, as the control unit follows moving materials, the reading time has been improved by almost three-fold compared to an RFID system employing conventional fixed antennas. The proposed system also has a recognition rate of over 99% without additional antennas for detecting the sides of a box of materials. The recognition rate meets the conditions recommended by the Electronic Product Code glbal network (EPC)global for commercializing the system, with three antennas at a 20 dBm power of reader and a conveyor belt speed of 3.17 m/s. This will enable a host of new RFID conveyor belt gate systems with increased performance. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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279 KiB

Open AccessArticle

Adaptive Redundant Speech Transmission over Wireless Multimedia Sensor Networks Based on Estimation of Perceived Speech Quality

by Jin Ah Kang and Hong Kook Kim

Sensors 2011, 11(9), 8469-8484; https://doi.org/10.3390/s110908469 - 31 Aug 2011

Cited by 10 | Viewed by 9062

Abstract

An adaptive redundant speech transmission (ARST) approach to improve the perceived speech quality (PSQ) of speech streaming applications over wireless multimedia sensor networks (WMSNs) is proposed in this paper. The proposed approach estimates the PSQ as well as the packet loss rate (PLR) [...] Read more.

An adaptive redundant speech transmission (ARST) approach to improve the perceived speech quality (PSQ) of speech streaming applications over wireless multimedia sensor networks (WMSNs) is proposed in this paper. The proposed approach estimates the PSQ as well as the packet loss rate (PLR) from the received speech data. Subsequently, it decides whether the transmission of redundant speech data (RSD) is required in order to assist a speech decoder to reconstruct lost speech signals for high PLRs. According to the decision, the proposed ARST approach controls the RSD transmission, then it optimizes the bitrate of speech coding to encode the current speech data (CSD) and RSD bitstream in order to maintain the speech quality under packet loss conditions. The effectiveness of the proposed ARST approach is then demonstrated using the adaptive multirate-narrowband (AMR-NB) speech codec and ITU-T Recommendation P.563 as a scalable speech codec and the PSQ estimation, respectively. It is shown from the experiments that a speech streaming application employing the proposed ARST approach significantly improves speech quality under packet loss conditions in WMSNs. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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Graphical abstract

1014 KiB

Open AccessArticle

A Novel Addressing Scheme for PMIPv6 Based Global IP-WSNs

by Md. Motaharul Islam and Eui-Nam Huh

Sensors 2011, 11(9), 8430-8455; https://doi.org/10.3390/s110908430 - 29 Aug 2011

Cited by 18 | Viewed by 8375

Abstract

IP based Wireless Sensor Networks (IP-WSNs) are being used in healthcare, home automation, industrial control and agricultural monitoring. In most of these applications global addressing of individual IP-WSN nodes and layer-three routing for mobility enabled IP-WSN with special attention to reliability, energy efficiency [...] Read more.

IP based Wireless Sensor Networks (IP-WSNs) are being used in healthcare, home automation, industrial control and agricultural monitoring. In most of these applications global addressing of individual IP-WSN nodes and layer-three routing for mobility enabled IP-WSN with special attention to reliability, energy efficiency and end to end delay minimization are a few of the major issues to be addressed. Most of the routing protocols in WSN are based on layer-two approaches. For reliability and end to end communication enhancement the necessity of layer-three routing for IP-WSNs is generating significant attention among the research community, but due to the hurdle of maintaining routing state and other communication overhead, it was not possible to introduce a layer-three routing protocol for IP-WSNs. To address this issue we propose in this paper a global addressing scheme and layer-three based hierarchical routing protocol. The proposed addressing and routing approach focuses on all the above mentioned issues. Simulation results show that the proposed addressing and routing approach significantly enhances the reliability, energy efficiency and end to end delay minimization. We also present architecture, message formats and different routing scenarios in this paper. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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1310 KiB

Open AccessArticle

A Study on Group Key Agreement in Sensor Network Environments Using Two-Dimensional Arrays

by Seung-Jae Jang, Young-Gu Lee, Kwang-Hyung Lee, Tai-Hoon Kim and Moon-Seog Jun

Sensors 2011, 11(9), 8227-8240; https://doi.org/10.3390/s110908227 - 25 Aug 2011

Cited by 3 | Viewed by 7200

Abstract

These days, with the emergence of the concept of ubiquitous computing, sensor networks that collect, analyze and process all the information through the sensors have become of huge interest. However, sensor network technology fundamentally has wireless communication infrastructure as its foundation and thus [...] Read more.

These days, with the emergence of the concept of ubiquitous computing, sensor networks that collect, analyze and process all the information through the sensors have become of huge interest. However, sensor network technology fundamentally has wireless communication infrastructure as its foundation and thus has security weakness and limitations such as low computing capacity, power supply limitations and price. In this paper, and considering the characteristics of the sensor network environment, we propose a group key agreement method using a keyset pre-distribution of two-dimension arrays that should minimize the exposure of key and personal information. The key collision problems are resolved by utilizing a polygonal shape’s center of gravity. The method shows that calculating a polygonal shape’s center of gravity only requires a very small amount of calculations from the users. The simple calculation not only increases the group key generation efficiency, but also enhances the sense of security by protecting information between nodes. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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Graphical abstract

779 KiB

Open AccessCommunication

Smart Learning Services Based on Smart Cloud Computing

by Svetlana Kim, Su-Mi Song and Yong-Ik Yoon

Sensors 2011, 11(8), 7835-7850; https://doi.org/10.3390/s110807835 - 9 Aug 2011

Cited by 93 | Viewed by 15599

Abstract

Context-aware technologies can make e-learning services smarter and more efficient since context-aware services are based on the user’s behavior. To add those technologies into existing e-learning services, a service architecture model is needed to transform the existing e-learning environment, which is situation-aware, into [...] Read more.

Context-aware technologies can make e-learning services smarter and more efficient since context-aware services are based on the user’s behavior. To add those technologies into existing e-learning services, a service architecture model is needed to transform the existing e-learning environment, which is situation-aware, into the environment that understands context as well. The context-awareness in e-learning may include the awareness of user profile and terminal context. In this paper, we propose a new notion of service that provides context-awareness to smart learning content in a cloud computing environment. We suggest the elastic four smarts (E4S)—smart pull, smart prospect, smart content, and smart push—concept to the cloud services so smart learning services are possible. The E4S focuses on meeting the users’ needs by collecting and analyzing users’ behavior, prospecting future services, building corresponding contents, and delivering the contents through cloud computing environment. Users’ behavior can be collected through mobile devices such as smart phones that have built-in sensors. As results, the proposed smart e-learning model in cloud computing environment provides personalized and customized learning services to its users. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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Graphical abstract

335 KiB

Open AccessArticle

Design and Analysis of Self-Adapted Task Scheduling Strategies in Wireless Sensor Networks

by Wenzhong Guo, Naixue Xiong, Han-Chieh Chao, Sajid Hussain and Guolong Chen

Sensors 2011, 11(7), 6533-6554; https://doi.org/10.3390/s110706533 - 27 Jun 2011

Cited by 80 | Viewed by 8867

Abstract

In a wireless sensor network (WSN), the usage of resources is usually highly related to the execution of tasks which consume a certain amount of computing and communication bandwidth. Parallel processing among sensors is a promising solution to provide the demanded computation capacity [...] Read more.

In a wireless sensor network (WSN), the usage of resources is usually highly related to the execution of tasks which consume a certain amount of computing and communication bandwidth. Parallel processing among sensors is a promising solution to provide the demanded computation capacity in WSNs. Task allocation and scheduling is a typical problem in the area of high performance computing. Although task allocation and scheduling in wired processor networks has been well studied in the past, their counterparts for WSNs remain largely unexplored. Existing traditional high performance computing solutions cannot be directly implemented in WSNs due to the limitations of WSNs such as limited resource availability and the shared communication medium. In this paper, a self-adapted task scheduling strategy for WSNs is presented. First, a multi-agent-based architecture for WSNs is proposed and a mathematical model of dynamic alliance is constructed for the task allocation problem. Then an effective discrete particle swarm optimization (PSO) algorithm for the dynamic alliance (DPSO-DA) with a well-designed particle position code and fitness function is proposed. A mutation operator which can effectively improve the algorithm’s ability of global search and population diversity is also introduced in this algorithm. Finally, the simulation results show that the proposed solution can achieve significant better performance than other algorithms. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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382 KiB

Open AccessArticle

Operating Systems for Wireless Sensor Networks: A Survey

by Muhammad Omer Farooq and Thomas Kunz

Sensors 2011, 11(6), 5900-5930; https://doi.org/10.3390/s110605900 - 31 May 2011

Cited by 125 | Viewed by 29223

Abstract

This paper presents a survey on the current state-of-the-art in Wireless Sensor Network (WSN) Operating Systems (OSs). In recent years, WSNs have received tremendous attention in the research community, with applications in battlefields, industrial process monitoring, home automation, and environmental monitoring, to name [...] Read more.

This paper presents a survey on the current state-of-the-art in Wireless Sensor Network (WSN) Operating Systems (OSs). In recent years, WSNs have received tremendous attention in the research community, with applications in battlefields, industrial process monitoring, home automation, and environmental monitoring, to name but a few. A WSN is a highly dynamic network because nodes die due to severe environmental conditions and battery power depletion. Furthermore, a WSN is composed of miniaturized motes equipped with scarce resources e.g., limited memory and computational abilities. WSNs invariably operate in an unattended mode and in many scenarios it is impossible to replace sensor motes after deployment, therefore a fundamental objective is to optimize the sensor motes’ life time. These characteristics of WSNs impose additional challenges on OS design for WSN, and consequently, OS design for WSN deviates from traditional OS design. The purpose of this survey is to highlight major concerns pertaining to OS design in WSNs and to point out strengths and weaknesses of contemporary OSs for WSNs, keeping in mind the requirements of emerging WSN applications. The state-of-the-art in operating systems for WSNs has been examined in terms of the OS Architecture, Programming Model, Scheduling, Memory Management and Protection, Communication Protocols, Resource Sharing, Support for Real-Time Applications, and additional features. These features are surveyed for both real-time and non-real-time WSN operating systems. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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0 pages, 866 KiB

Open AccessArticle

RETRACTED: Authenticated Key Agreement with Rekeying for Secured Body Sensor Networks

by Mohamed Hamdy Eldefrawy, Muhammad Khurram Khan, Khaled Alghathbar, Ahmed Saleh Tolba and Kyngn Jung Kim

Sensors 2011, 11(6), 5835-5849; https://doi.org/10.3390/s110605835 - 31 May 2011

Cited by 4 | Viewed by 9047 | Retraction

Abstract

This paper has been retracted on 15 August 2011. A Retraction note is published in Sensors, 2011, 11, 7992 Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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637 KiB

Open AccessArticle

Burst Packet Loss Concealment Using Multiple Codebooks and Comfort Noise for CELP-Type Speech Coders in Wireless Sensor Networks

by Nam In Park, Hong Kook Kim, Min A Jung, Seong Ro Lee and Seung Ho Choi

Sensors 2011, 11(5), 5323-5336; https://doi.org/10.3390/s110505323 - 17 May 2011

Cited by 10 | Viewed by 9266

Abstract

In this paper, a packet loss concealment (PLC) algorithm for CELP-type speech coders is proposed in order to improve the quality of decoded speech under burst packet loss conditions in a wireless sensor network. Conventional receiver-based PLC algorithms in the G.729 speech codec [...] Read more.

In this paper, a packet loss concealment (PLC) algorithm for CELP-type speech coders is proposed in order to improve the quality of decoded speech under burst packet loss conditions in a wireless sensor network. Conventional receiver-based PLC algorithms in the G.729 speech codec are usually based on speech correlation to reconstruct the decoded speech of lost frames by using parameter information obtained from the previous correctly received frames. However, this approach has difficulty in reconstructing voice onset signals since the parameters such as pitch, linear predictive coding coefficient, and adaptive/fixed codebooks of the previous frames are mostly related to silence frames. Thus, in order to reconstruct speech signals in the voice onset intervals, we propose a multiple codebook-based approach that includes a traditional adaptive codebook and a new random codebook composed of comfort noise. The proposed PLC algorithm is designed as a PLC algorithm for G.729 and its performance is then compared with that of the PLC algorithm currently employed in G.729 via a perceptual evaluation of speech quality, a waveform comparison, and a preference test under different random and burst packet loss conditions. It is shown from the experiments that the proposed PLC algorithm provides significantly better speech quality than the PLC algorithm employed in G.729 under all the test conditions. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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355 KiB

Open AccessArticle

Multi-Hop Routing-Based Optimization of the Number of Cluster-Heads in Wireless Sensor Networks

by Choon Sung Nam, Young Shin Han and Dong Ryeol Shin

Sensors 2011, 11(3), 2875-2884; https://doi.org/10.3390/s110302875 - 3 Mar 2011

Cited by 18 | Viewed by 7486

Abstract

Wireless sensor networks require energy-efficient data transmission because the sensor nodes have limited power. A cluster-based routing method is more energy-efficient than a flat routing method as it can only send specific data for user requirements and aggregate similar data by dividing a [...] Read more.

Wireless sensor networks require energy-efficient data transmission because the sensor nodes have limited power. A cluster-based routing method is more energy-efficient than a flat routing method as it can only send specific data for user requirements and aggregate similar data by dividing a network into a local cluster. However, previous clustering algorithms have some problems in that the transmission radius of sensor nodes is not realistic and multi-hop based communication is not used both inside and outside local clusters. As energy consumption based on clustering is dependent on the number of clusters, we need to know how many clusters are best. Thus, we propose an optimal number of cluster-heads based on multi-hop routing in wireless sensor networks. We observe that a local cluster made by a cluster-head influences the energy consumption of sensor nodes. We determined an equation for the number of packets to send and relay, and calculated the energy consumption of sensor networks using it. Through the process of calculating the energy consumption, we can obtain the optimal number of cluster-heads in wireless sensor networks. Full article

(This article belongs to the Special Issue Selected Papers from FGIT 2010)

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