This document discusses three problems related to efficient tag detection in RFID systems: (1) detecting tags accurately in the presence of reader interference, known as the reader collision avoidance problem; (2) eliminating redundant tag reports from multiple readers, known as the optimal tag reporting problem; and (3) minimizing redundant reports from multiple readers by identifying a minimal set of readers that cover all tags, known as the optimal tag coverage problem. The document proposes algorithms to address these problems in a distributed, localized manner without requiring global knowledge or a centralized controller. It analyzes the performance and accuracy of the proposed algorithms through simulations.
Mobile Adhoc Network (MANET) is a self-configuring and infrastructure-less network which consists of mobile devices such as mobiles, laptops, PDA's etc. Because of its lack of infrastructure, wireless mobile communication, dynamic topology, MANET is vulnerable to various security attacks. This survey paper presents an overview of developments of voting and non-voting based certificate revocation mechanisms in past few years. Certificate revocation is an important method used to secure the MANET. Certificate revocation isolates the attacker nodes from participating in network activities by revoking its certificate. Over last few years different schemes are explored for certificate revocation. In concluding section we present the limitations of the current cluster based certificate revocation scheme.
Support Recovery with Sparsely Sampled Free Random Matrices for Wideband Cogn...IJMTST Journal
The main objective of this project is to design an eigenvalue-based compressive SOE technique using asymptotic random matrix theory. In this project, investigating blind sparsity order estimation (SOE) techniques is an open research issue. To address this, this project presents an eigenvalue-based compressive SOE technique using asymptotic random matrix theory. Finally, this project propose a technique to estimate the sparsity order of the wideband spectrum with compressive measurements using the maximum eigenvalue of the measured signal's covariance matrix. .
Table-Based Identification Protocol of Compuatational RFID Tags csandit
Computation RFID (CRFID) expands the limit of traditional RFID by granting computational
capability to RFID tags. RFID tags are powered by Radio-Frequency (RF) energy harvesting.
However, CRFID tags need extra energy and processing time than traditional RFID tags to
sense the environment and generate sensing data. Therefore, Dynamic Framed Slotted ALOHA
(DFSA) protocol for traditional RFID is no longer a best solution for CRFID systems. In this
paper, we propose a table-based CRFID tag identification protocol considering CRFID
operation. An RFID reader sends the message with the frame index. Using the frame index,
CRFID tags calculate the energy requirement and processing time information to the reader
along with data transmission. The RFID reader records the received information of tags into a
table. After table recording is completed, the optimal frame size and proper time interval is
provided based on the table. The proposed CRFID tag identification protocol is shown to
enhance the identification rate and the delay via simulations.
The peer-reviewed International Journal of Engineering Inventions (IJEI) is started with a mission to encourage contribution to research in Science and Technology. Encourage and motivate researchers in challenging areas of Sciences and Technology.
One of the most popular areas of research is wireless communication. Mobile Ad Hoc network (MANET) is a network with wireless mobile nodes, infrastructure less and self organizing. With its wireless and distributed nature it is exposed to several security threats. One of the threats in MANET is the wormhole attack. In this attack a pair of attacker forms a virtual link thereby recording and replaying the wireless transmission. This paper presents types of wormhole attack and also includes different technique for detecting wormhole attack in MANET..
Mobile Adhoc Network (MANET) is a self-configuring and infrastructure-less network which consists of mobile devices such as mobiles, laptops, PDA's etc. Because of its lack of infrastructure, wireless mobile communication, dynamic topology, MANET is vulnerable to various security attacks. This survey paper presents an overview of developments of voting and non-voting based certificate revocation mechanisms in past few years. Certificate revocation is an important method used to secure the MANET. Certificate revocation isolates the attacker nodes from participating in network activities by revoking its certificate. Over last few years different schemes are explored for certificate revocation. In concluding section we present the limitations of the current cluster based certificate revocation scheme.
Support Recovery with Sparsely Sampled Free Random Matrices for Wideband Cogn...IJMTST Journal
The main objective of this project is to design an eigenvalue-based compressive SOE technique using asymptotic random matrix theory. In this project, investigating blind sparsity order estimation (SOE) techniques is an open research issue. To address this, this project presents an eigenvalue-based compressive SOE technique using asymptotic random matrix theory. Finally, this project propose a technique to estimate the sparsity order of the wideband spectrum with compressive measurements using the maximum eigenvalue of the measured signal's covariance matrix. .
Table-Based Identification Protocol of Compuatational RFID Tags csandit
Computation RFID (CRFID) expands the limit of traditional RFID by granting computational
capability to RFID tags. RFID tags are powered by Radio-Frequency (RF) energy harvesting.
However, CRFID tags need extra energy and processing time than traditional RFID tags to
sense the environment and generate sensing data. Therefore, Dynamic Framed Slotted ALOHA
(DFSA) protocol for traditional RFID is no longer a best solution for CRFID systems. In this
paper, we propose a table-based CRFID tag identification protocol considering CRFID
operation. An RFID reader sends the message with the frame index. Using the frame index,
CRFID tags calculate the energy requirement and processing time information to the reader
along with data transmission. The RFID reader records the received information of tags into a
table. After table recording is completed, the optimal frame size and proper time interval is
provided based on the table. The proposed CRFID tag identification protocol is shown to
enhance the identification rate and the delay via simulations.
The peer-reviewed International Journal of Engineering Inventions (IJEI) is started with a mission to encourage contribution to research in Science and Technology. Encourage and motivate researchers in challenging areas of Sciences and Technology.
One of the most popular areas of research is wireless communication. Mobile Ad Hoc network (MANET) is a network with wireless mobile nodes, infrastructure less and self organizing. With its wireless and distributed nature it is exposed to several security threats. One of the threats in MANET is the wormhole attack. In this attack a pair of attacker forms a virtual link thereby recording and replaying the wireless transmission. This paper presents types of wormhole attack and also includes different technique for detecting wormhole attack in MANET..
Cisco Certification Training Provides job oriented online training with ccna ccnp interview questions by real time CISCO Professionals who attend with us
A review on distributed beam forming techniques an approach in wireless rela...eSAT Journals
Abstract Physical layer security can be considered to solve the security problem from the point of view of information theory in wireless networks. The combination of cryptographic schemes with channel coding techniques is called for in the basic principle of information-theoretic security. Due to the presence of one or more eavesdropper in wireless relay networks, secrecy of communication is in jeopardy. For such a scenario secrecy rate of the network provide a good measure of performance of the system. In this paper our focus is on secrecy capacity and its optimization with appropriate weight designs of relays taking into consideration the channels through which the eavesdroppers are connected to the relays. We propose the AF and DF based optimal beam forming scheme to improve the wireless security against eavesdropping attack by detecting and removing the eavesdroppers from the wireless relay networks and thus finding measures to maximize the efficiency, response time and the throughput of the system It includes an auto-regression technique as first approach and the use of RC6 algorithm for encrypting the confidential messages. The scheme is a two way approach that will not only provides security to the confidential messages, to be communicated within a wireless relay network in presence of multiple relays and eavesdroppers, but also it will deal with the saving the consumed power by detecting and removing the nodes which are malicious or defected which in turn will consume more power in order to perform malicious activity on the messages or may try to create interferences in the network. The eavesdropper nodes in the proposed system are considered to be working as relays so it may either be connected to source or destination directly or in between the relays. Keywords: Beamforming, Channel State Information, Eavesdropper Attack, Power Consumption, Secrecy Capacity.
EAASR: Enhanced AASR Protocol to Reduce Traffic and Eliminate the Malicious N...paperpublications3
Abstract: Mobile ad hoc networks (MANETs) are self-organizing the mobile nodes. It placed in adversary environments and it is vulnerable to security threats due to the characteristics of such networks. The main requirement on the networks is to provide unidentifiability and unlinkability for mobile networks. The existing protocols are not fully satisfied in this requirements. In this paper propose a new routing protocol that is enhanced authenticated anonymous secure routing (EAASR), to satisfy the unidentifiability and unlinkability. The new protocol provides less delay as compared with other protocol.
PRIVACY ENHANCEMENT OF NODE IN OPPORTUNISTIC NETWORK BY USING VIRTUAL-IDijsc
An entrepreneurial system is one of the sort of remote system. Delay resistance system is correspondence
organizing proposition which empowers the correspondence in such a situation where end to end way
might never be exist. Message is forward on the premise of chance. Time interim to convey a message is
long we can't evaluate or anticipate the time until we get the message. There is a security issue in these
sorts of system. In this paper we will proposed another procedure which will expand the protection of the
system and build execution of the system.
A Multiparametric Reliable AODV Protocol using Alternate Routing in MANET’s u...Editor IJCATR
In this paper, we design and formulate a trust-based routing protocol for secure transactions, such as military and disaster
relief operations, banking in mobile ad hoc networks (MANETs). The proposed approach is showing the idea of a trust model in the
network layer of MANET.AODV is ad hoc on demand distance vector, this protocol starts the route specially when some node claims
to send data. In AODV whenever a link breaks an error message is sent indicating the link and packet sending is dropped. In our
proposed scheme a packet is sent through alternative path. In this approach a trust node is made with neighbors. Simulation results
shows that proposed scheme has less packet loss and packet ratio delivered is more.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A Novel Approach To Detect Trustworthy Nodes Using Audit Based Scheme For WSNIJERDJOURNAL
ABSTRACT: In multi-hop ad hoc networks there exists a problem of identifying and isolating misbehaving nodes which refuses to forward packets. Audit-based Misbehavior Detection (AMD) is a comprehensive system that effectively and efficiently isolates both continuous and selective packet droppers. The AMD system integrates reputation management, trustworthy route discovery, and identification of misbehaving nodes based on behavioral audits. Compared to previous methods, AMD evaluates node behavior on a per-packet basis, without employing energy-expensive overhearing techniques or intensive acknowledgment schemes. Moreover, AMD can detect selective dropping attacks even if end-to-end traffic is encrypted and can be applied to multichannel networks or networks consisting of nodes with directional antennas. This work implements the AMD approach by considering the rushing attack. The analysis of the results confirms that AMD based method with rushing attack performs better as compared to the non rushing attack.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Popularity of ubiquitous computing increases the importance of location-aware applications,
which increases the need for finding location of the user. In this paper, we present a novel localization method
for indoor environments using Wi-Fi infrastructure.
While localization using Wi-Fi is cost effective, handling the obstructions which are the main cause of
signal propagation error in indoor environments is a challenging task. We address this problem in two levels,
resulting in increased accuracy of localization. In the first level, we "localize" the residing area of user node in
coarse granularity. Then, we use building layout to find the objects that attenuate the signal between the
reference node and the coarse estimate of the location of user node. Using multi-wall propagation model, we
apply corrections for all obstructions and find the location of user node. Empirical results based on experiments
conducted in lab-scale, shows meter-level accuracy.
A MANET is a continuously self-configuring, infrastructure-less type network, which consists of number of mobile nodes
with wireless network interfaces. In order to make communication among nodes, the nodes demoniacally establish paths among
neighbouring nodes. Security in mobile adhoc network is a big challenge because many nodes perform many kinds of misbehaviour.
In this paper, the main focus is on collaborative attacks in MANET using CBDS approach. CBDS is a approach which consolidate
asset of proactive and reactive defense method in reverse tracing. In reverse tracing method we compare performance of CBDS
approach with DSR and AOMDV routing protocols.
Bayesian distance metric learning and its application in automatic speaker re...IJECEIAES
This paper proposes state-of the-art Automatic Speaker Recognition System (ASR) based on Bayesian Distance Learning Metric as a feature extractor. In this modeling, I explored the constraints of the distance between modified and simplified i-vector pairs by the same speaker and different speakers. An approximation of the distance metric is used as a weighted covariance matrix from the higher eigenvectors of the covariance matrix, which is used to estimate the posterior distribution of the metric distance. Given a speaker tag, I select the data pair of the different speakers with the highest cosine score to form a set of speaker constraints. This collection captures the most discriminating variability between the speakers in the training data. This Bayesian distance learning approach achieves better performance than the most advanced methods. Furthermore, this method is insensitive to normalization compared to cosine scores. This method is very effective in the case of limited training data. The modified supervised i-vector based ASR system is evaluated on the NIST SRE 2008 database. The best performance of the combined cosine score EER 1.767% obtained using LDA200 + NCA200 + LDA200, and the best performance of Bayes_dml EER 1.775% obtained using LDA200 + NCA200 + LDA100. Bayesian_dml overcomes the combined norm of cosine scores and is the best result of the short2-short3 condition report for NIST SRE 2008 data.
A Novel Acknowledgement based Intrusion Detection System for MANETsIJMER
In Mobile Ad Hoc Networks(MANETs), a set of interacting nodes should cooperatively
implement the routing functions to enable end-to-end communication along dynamic paths composed by
multi-hop wireless links. Several multi-hop routing protocols have been proposed for ad hoc networks,
and most popular ones include: Dynamic Source Routing (DSR), Optimized Link-State Routing (OLSR),
Ad Hoc On-Demand Distance Vector (AODV) and Destination- Sequenced Distance-Vector (DSDV).
Most of these protocols rely on the assumption of a trustworthy cooperation among all participating
nodes; unfortunately, this may not be a realistic assumption in real hosts. Malicious hosts could exploit
the weakness of MANET to launch various kinds of attacks. Node mobility on ad hoc network cannot be
restricted. As results, many Intrusion Detection System(IDS) solutions have been proposed for the wired
network, which they are defined on strategic points such as switches, gateways, and routers, can not be
implemented on the MANET. Thus, the wired network IDS characteristics must be modified prior to be
implemented in the ad hoc network. Thus an IDS should be added to enhance the security level of
MANETs. If MANET can detect the attackers as soon as they enter the network, we will be able to
completely eliminate the potential vulnerabilities caused by compromised nodes at the first time. IDSs
usually act as the second layer in MANETs. This paper presents an novel IDS for MANETs which is
based on acknowledgements.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Enhancing AODV Routing Protocol to Eliminate Black Hole Attack in MANET.......................................1
Ei Ei Khin and Thandar Phyu
Adaptive Search Information Technology in the University Library ........................................................ 15
Andriy Andrukhiv and Dmytro Tarasov
Educational Data Mining: Performance Evaluation of Decision Tree and Clustering Techniques Using
WEKA Platform........................................................................................................................................... 26
Ritika Saxena
Hamiltonian cycle in graphs 흈4 ≥ ퟐn....................................................................................................... 38
Nguyen Huu Xuan Truong and Vu Dinh Hoa
Cisco Certification Training Provides job oriented online training with ccna ccnp interview questions by real time CISCO Professionals who attend with us
A review on distributed beam forming techniques an approach in wireless rela...eSAT Journals
Abstract Physical layer security can be considered to solve the security problem from the point of view of information theory in wireless networks. The combination of cryptographic schemes with channel coding techniques is called for in the basic principle of information-theoretic security. Due to the presence of one or more eavesdropper in wireless relay networks, secrecy of communication is in jeopardy. For such a scenario secrecy rate of the network provide a good measure of performance of the system. In this paper our focus is on secrecy capacity and its optimization with appropriate weight designs of relays taking into consideration the channels through which the eavesdroppers are connected to the relays. We propose the AF and DF based optimal beam forming scheme to improve the wireless security against eavesdropping attack by detecting and removing the eavesdroppers from the wireless relay networks and thus finding measures to maximize the efficiency, response time and the throughput of the system It includes an auto-regression technique as first approach and the use of RC6 algorithm for encrypting the confidential messages. The scheme is a two way approach that will not only provides security to the confidential messages, to be communicated within a wireless relay network in presence of multiple relays and eavesdroppers, but also it will deal with the saving the consumed power by detecting and removing the nodes which are malicious or defected which in turn will consume more power in order to perform malicious activity on the messages or may try to create interferences in the network. The eavesdropper nodes in the proposed system are considered to be working as relays so it may either be connected to source or destination directly or in between the relays. Keywords: Beamforming, Channel State Information, Eavesdropper Attack, Power Consumption, Secrecy Capacity.
EAASR: Enhanced AASR Protocol to Reduce Traffic and Eliminate the Malicious N...paperpublications3
Abstract: Mobile ad hoc networks (MANETs) are self-organizing the mobile nodes. It placed in adversary environments and it is vulnerable to security threats due to the characteristics of such networks. The main requirement on the networks is to provide unidentifiability and unlinkability for mobile networks. The existing protocols are not fully satisfied in this requirements. In this paper propose a new routing protocol that is enhanced authenticated anonymous secure routing (EAASR), to satisfy the unidentifiability and unlinkability. The new protocol provides less delay as compared with other protocol.
PRIVACY ENHANCEMENT OF NODE IN OPPORTUNISTIC NETWORK BY USING VIRTUAL-IDijsc
An entrepreneurial system is one of the sort of remote system. Delay resistance system is correspondence
organizing proposition which empowers the correspondence in such a situation where end to end way
might never be exist. Message is forward on the premise of chance. Time interim to convey a message is
long we can't evaluate or anticipate the time until we get the message. There is a security issue in these
sorts of system. In this paper we will proposed another procedure which will expand the protection of the
system and build execution of the system.
A Multiparametric Reliable AODV Protocol using Alternate Routing in MANET’s u...Editor IJCATR
In this paper, we design and formulate a trust-based routing protocol for secure transactions, such as military and disaster
relief operations, banking in mobile ad hoc networks (MANETs). The proposed approach is showing the idea of a trust model in the
network layer of MANET.AODV is ad hoc on demand distance vector, this protocol starts the route specially when some node claims
to send data. In AODV whenever a link breaks an error message is sent indicating the link and packet sending is dropped. In our
proposed scheme a packet is sent through alternative path. In this approach a trust node is made with neighbors. Simulation results
shows that proposed scheme has less packet loss and packet ratio delivered is more.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A Novel Approach To Detect Trustworthy Nodes Using Audit Based Scheme For WSNIJERDJOURNAL
ABSTRACT: In multi-hop ad hoc networks there exists a problem of identifying and isolating misbehaving nodes which refuses to forward packets. Audit-based Misbehavior Detection (AMD) is a comprehensive system that effectively and efficiently isolates both continuous and selective packet droppers. The AMD system integrates reputation management, trustworthy route discovery, and identification of misbehaving nodes based on behavioral audits. Compared to previous methods, AMD evaluates node behavior on a per-packet basis, without employing energy-expensive overhearing techniques or intensive acknowledgment schemes. Moreover, AMD can detect selective dropping attacks even if end-to-end traffic is encrypted and can be applied to multichannel networks or networks consisting of nodes with directional antennas. This work implements the AMD approach by considering the rushing attack. The analysis of the results confirms that AMD based method with rushing attack performs better as compared to the non rushing attack.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Popularity of ubiquitous computing increases the importance of location-aware applications,
which increases the need for finding location of the user. In this paper, we present a novel localization method
for indoor environments using Wi-Fi infrastructure.
While localization using Wi-Fi is cost effective, handling the obstructions which are the main cause of
signal propagation error in indoor environments is a challenging task. We address this problem in two levels,
resulting in increased accuracy of localization. In the first level, we "localize" the residing area of user node in
coarse granularity. Then, we use building layout to find the objects that attenuate the signal between the
reference node and the coarse estimate of the location of user node. Using multi-wall propagation model, we
apply corrections for all obstructions and find the location of user node. Empirical results based on experiments
conducted in lab-scale, shows meter-level accuracy.
A MANET is a continuously self-configuring, infrastructure-less type network, which consists of number of mobile nodes
with wireless network interfaces. In order to make communication among nodes, the nodes demoniacally establish paths among
neighbouring nodes. Security in mobile adhoc network is a big challenge because many nodes perform many kinds of misbehaviour.
In this paper, the main focus is on collaborative attacks in MANET using CBDS approach. CBDS is a approach which consolidate
asset of proactive and reactive defense method in reverse tracing. In reverse tracing method we compare performance of CBDS
approach with DSR and AOMDV routing protocols.
Bayesian distance metric learning and its application in automatic speaker re...IJECEIAES
This paper proposes state-of the-art Automatic Speaker Recognition System (ASR) based on Bayesian Distance Learning Metric as a feature extractor. In this modeling, I explored the constraints of the distance between modified and simplified i-vector pairs by the same speaker and different speakers. An approximation of the distance metric is used as a weighted covariance matrix from the higher eigenvectors of the covariance matrix, which is used to estimate the posterior distribution of the metric distance. Given a speaker tag, I select the data pair of the different speakers with the highest cosine score to form a set of speaker constraints. This collection captures the most discriminating variability between the speakers in the training data. This Bayesian distance learning approach achieves better performance than the most advanced methods. Furthermore, this method is insensitive to normalization compared to cosine scores. This method is very effective in the case of limited training data. The modified supervised i-vector based ASR system is evaluated on the NIST SRE 2008 database. The best performance of the combined cosine score EER 1.767% obtained using LDA200 + NCA200 + LDA200, and the best performance of Bayes_dml EER 1.775% obtained using LDA200 + NCA200 + LDA100. Bayesian_dml overcomes the combined norm of cosine scores and is the best result of the short2-short3 condition report for NIST SRE 2008 data.
A Novel Acknowledgement based Intrusion Detection System for MANETsIJMER
In Mobile Ad Hoc Networks(MANETs), a set of interacting nodes should cooperatively
implement the routing functions to enable end-to-end communication along dynamic paths composed by
multi-hop wireless links. Several multi-hop routing protocols have been proposed for ad hoc networks,
and most popular ones include: Dynamic Source Routing (DSR), Optimized Link-State Routing (OLSR),
Ad Hoc On-Demand Distance Vector (AODV) and Destination- Sequenced Distance-Vector (DSDV).
Most of these protocols rely on the assumption of a trustworthy cooperation among all participating
nodes; unfortunately, this may not be a realistic assumption in real hosts. Malicious hosts could exploit
the weakness of MANET to launch various kinds of attacks. Node mobility on ad hoc network cannot be
restricted. As results, many Intrusion Detection System(IDS) solutions have been proposed for the wired
network, which they are defined on strategic points such as switches, gateways, and routers, can not be
implemented on the MANET. Thus, the wired network IDS characteristics must be modified prior to be
implemented in the ad hoc network. Thus an IDS should be added to enhance the security level of
MANETs. If MANET can detect the attackers as soon as they enter the network, we will be able to
completely eliminate the potential vulnerabilities caused by compromised nodes at the first time. IDSs
usually act as the second layer in MANETs. This paper presents an novel IDS for MANETs which is
based on acknowledgements.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Enhancing AODV Routing Protocol to Eliminate Black Hole Attack in MANET.......................................1
Ei Ei Khin and Thandar Phyu
Adaptive Search Information Technology in the University Library ........................................................ 15
Andriy Andrukhiv and Dmytro Tarasov
Educational Data Mining: Performance Evaluation of Decision Tree and Clustering Techniques Using
WEKA Platform........................................................................................................................................... 26
Ritika Saxena
Hamiltonian cycle in graphs 흈4 ≥ ퟐn....................................................................................................... 38
Nguyen Huu Xuan Truong and Vu Dinh Hoa
Forewards customer referral programs for ecommerceJason Dea
Are you spending your marketing dollars on the most efficient channel of them all? Customer referrals, word of mouth, and advocate marketing programs have proven to be the most efficient and the most effective ways for businesses of all sizes to scale and grow. Forewards makes setting up a refer a friend program simple and effective for even the most resource strapped organizations.
Tämän asiakirjan tarkoitus on edistää ja ylläpitää kestävää kehitystä, tarkoituksenmukaisella, taloudellisella ja ympäristöä vaalivalla tavalla ehkäistä oman toiminnan, käyttäjien ja tuotettujen palvelujen sekä ylläpidon aiheuttamia haitallisia ympäristövaikutuksia, sekä vaikuttaa paikallisesti omalla esimerkillä ympäristö tietoiseen toimintaan. Tavoitteena on, ennaltaehkäistä, ja minimoida tiedossa olevat sekä hyvissä ajoin havaita ja välttää uudet ympäristöä kuormittavat tekijät.
Here is your last DAKTARI Newsletter of 2014!! As always, it keeps you update about the local underprivileged children, the orphaned animals and all our exciting projects! Enjoy the reading! www.daktaribushschool.org
Grouping based radio frequency identification anti-collision protocols for d...IJECEIAES
Radio frequency identification (RFID) is an important internet of things (IoT) enabling technology. In RFIDs collision occur among tags because tags share communication channel. This is called tag collision problem. The problem becomes catastrophic when dense population of tags are deployed like in IoT. Hence, the need to enhance existing dynamic frame slotted ALOHA (DFSA) based electronic product code (EPC) C1G2 media access control (MAC) protocol. Firstly, this paper validates through simulation the DFSA theory that efficiency of the RFID system is maximum when the number tags is approximately equal to the frame size. Furthermore, literature review shows tag grouping is becoming popular to improving the efficiency of the RFID system. This paper analyzes selected grouping-based algorithms. Their underlining principles are discussed including their tag estimation methods. The algorithms were implemented in MATLAB while extensive Monte Carlo simulation was performed to evaluate their strengths and weaknesses. Results show that with higher tag density, fuzzy C-means based algorithm (FCMBG) outperformed traditional DFSA by over 40% in terms of throughput rate. The results also demonstrate FCMBG bettered other grouping-based algorithms (GB-DFSA and GBSA) whose tag estimation method are based on collision slots in terms slot efficiency by over 10% and also in terms of identification time.
Ijaems apr-2016-18 Simulation on probabilistic anti collision protocols of RF...INFOGAIN PUBLICATION
In RFID System, it is important to avoid tag collision for identifying tag faster. In this paper, we proposed concept of variable delay for tag estimation & identification. The scheme is based on the Multi-level dynamic framed ALOHA protocol. Simulation results indicate that the time delay is added to each tag for avoiding collision. The main advantage of this is the delay is in microseconds which will not create problem of more time consumption.
Ijaems apr-2016-35 Comparative Analysis of Anti-Collision Protocols in RFIDINFOGAIN PUBLICATION
Radio Frequency Identification, abbreviated as RFID which was originally invented as a replacement tool for bar-code scanning and identification has now evolved into a vital technology spanning across fields such as supply chain management, shipping of goods, tracking and identification, etc. However along with the widespread use of RFID, the underlying problem of collision of readers, and tags has been hampering the reliability, and integrity of RFID; thus causing a problem in the further evolution and future deployment of the same in new-born organizations. This papers aims at surveying the various anti-collision protocols which are designed and implemented in order to curb one of the major encumbrances in RFID technology viz. collision.
Systematic literature survey: applications of LoRa communicationIJECEIAES
LoRa is a communication scheme that is part of the low power wide area network (LPWAN) technology using ISM bands. It has seen extensive documentation and use in research and industry due to its long coverage ranges of up-to 20 km or more with less than 14 dB transmit power. Moreover, some applications report theoretical battery lives of up to 10 years for field deployed modules utilising the scheme in wireless sensor network (WSN) applications. Additionally, the scheme is very resilient to losses from noise, as well as bursts of interference through its forward error correction (FEC) scheme . Our objective is to systematically review the empirical evidence of the use-cases of LoRa in rural landscapes, metrics and the relevant validation schemes. In addition, the research is evaluated based on (i) mathematical function of the scheme (bandwidth use, spreading factor, symbol rate, chip rate and nominal bit rate) (ii) usecases (iii) test-beds, metrics of evaluation and (iv) validation methods. A systematic literature review of published refereed primary studies on LoRa applications was conducted using articles from 2010-2019. We identified 21 relevant primary studies. These reported a range of different assessments of LoRa with 10 out of 21 reporting on novel use cases. The authors conclude that more work is needed in terms of field testing, as no articles could be found on performance/deployment in Botswana or South Africa despite the existence of LoRa networks in both countries. Thus researchers in the region can research propagation models performance, the energy efficiency of the scheme and MAC layer as well as the channel access challenges for the region.
A Novel Spatio-Temporal Data Redundancy Elimination Approach for RFID Systems...ijwmn
In this paper, we propose a Voronoi diagram based spatio-temporal data redundancy elimination approach for RFID systems having multiple readers so that every RFID tag will
be read by only one reader depending on the distance between the tag and the center of the Minimum Enclosing Circle (MEC) of the Voronoi cell which the reader belongs to.
Thus, the spatial redundancy in the gathered data is completely eliminated. Temporal redundancy is also minimized by reading the RFID tags at regular time intervals larger than an
appropriately chosen threshold value. Existing methods of reducing data redundancy in RFID systems are often associated with loss of data, false positive errors and false
negative errors. In contrast to this, our proposed technique is free from any false positive and false negative errors with no loss of data and every tag being read by only one single reader. Simulation of our proposed approach also establishes its superiority to the existing techniques in terms of these performance parameters.
A Novel Spatio-Temporal Data Redundancy Elimination Approach for RFID Systems...ijwmn
In this paper, we propose a Voronoi diagram based spatio-temporal data redundancy elimination approach for RFID systems having multiple readers so that every RFID tag will be read by only one reader depending on the distance between the tag and the center of the Minimum Enclosing Circle (MEC) of the Voronoi cell which the reader belongs to. Thus, the spatial redundancy in the gathered data is completely eliminated. Temporal redundancy is also minimized by reading the RFID tags at regular time intervals larger than an appropriately chosen threshold value. Existing methods of reducing data redundancy in RFID systems are often associated with loss of data, false positive errors and false negative errors. In contrast to this, our proposed technique is free from any false positive and false negative errors with no loss of data and every tag being read by only one single reader. Simulation of our proposed approach also establishes its superiority to the existing techniques in terms of these performance parameters.
Energy Efficient Enhancement of TDEEC Wireless Sensors Network Protocol Based...chokrio
Radio frequency identification (RFID) and wireless sensor networks are two important wireless technologies which have a wide variety of applications in current and in future systems. By integration of these technologies, it is
feasible to improve the operating functionalities. In the heterogeneous network, the need to apply the balancing of
energy consumption across all nodes is very important to prevent the death of those nodes and thereafter increase the lifetime of the network .The most part of the network energy is consumed in the localization and in the communication stages, when nodes are sending HELLO packet, this energy can be recovered by implementing a passive RFID circuit in each node. This approach extends the network lifetime and increase the number of packet messages sent to the base station. Computer simulation in MATLAB with different scenarios comparison shows that the proposed method presents an efficient solution to enhance the energy network performance.
Performance Analysis of Multi-QoS Model of OCDMA System by Adopting OPPM Sign...IJERA Editor
In this paper, optical CDMA which combines the large bandwidth of the fibre medium with the flexibility of the
CDMA technique to achieve high speed connectivity has been used. For achieving this purpose, OPPM
signalling and switching techniques have been employed. This helps in the achievement of high tolerance to
Multiple Access Interference, further resulting in improvement of both the Bit Error Rate and optical channel
capacity without the need to decrease the light pulse width. An OPPM scheme to support multimedia services
with different transmission rates and Quality of Service requirements is proposed. Packet Switching technique
has been employed to help in the transfer of data in the form of packets from the source to the destination via a
specified route. The results are calculated by using PPM signalling and switching technology.But switching
technology has been found to be far better than the OOK-OCDMA if the average power has been considered as
the restraining factor.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
DESIGN AND VLSIIMPLEMENTATION OF ANTICOLLISION ENABLED ROBOT PROCESSOR USING ...VLSICS Design
RFID is a low power wireless emerging technology which has given rise to highly promising applications in real life. It can be employed for robot navigation. In multi-robot environment, when many robots are moving in the same workspace, there is a possibility of their physical collision with themselves as well as with physical objects. In the present work, we have proposed and developed a processor incorporating smart algorithm for avoiding such collisions with the help of RFID technology and implemented it by using VHDL. The design procedure and the simulated results are very useful in designing and implementing a practical RFID system. The RTL schematic view of the processor is achieved by successfully synthesizing the proposed design.
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
Running Head RFID Transportation2RFID in Tr.docxtoltonkendal
Running Head: RFID Transportation 2
RFID in Transportation Executive Summary
Pravallika Dubbakula
Wilmington University
Executive Summary
A study has been done on the use of radio frequency Identification and its commercial use in commercial industries. The aim of the study was to understand how the technology can help in providing information to a centralized control unit when the commodity transport vehicle or the items are being transported from one place to another. The study also undertook a detailed examination of the process that is used in the technology and the benefits of the Radio frequency identification technology in commercial industries.
It was found that the use of the technology reduced the losses in transit and made it simpler to use and tag the items for purchase or sale. It also helped to lower mal – practices when vehicles with goods were in transit from region to another. The radio frequency identification technology is the latest available technology in tracking systems using sensors. It has an electromagnetic field which is activated and increases the strength of the sensors when it apses by a reader which has sensors that picks up the data that has been micro chipped into the items or vehicles. These signals are transmitted to a centralized unit where it is transformed into readable information providing the whereabouts of the vehicles and the items.
A tag is attached and this tag is then further attached to the items. It was also found that there are 2 types of RFID tags one is passive and the other is active. The passive tags collect their energy resources from the readers that are installed close by and the active tag have their own power resources built into the tags such as small batteries that are powerful enough to transit information to a reader.
The data about the vehicles or the reader is sent using radio wave transmissions. It has also been found from the study that the radio frequency identification is one of the forms of automatic- Identification and data capture from tags known in short as – A.I.D.C. The most common method of radio frequency identification is implanting it into livestock, individuals and items. The tags have worked per their mechanisms even when they have been embedded into:
The radio frequency identification standards have been laid out in the ISO-IEC – 18000 and the ISO-IEC-29167. The standards specify the details of the methods that can be used for cryptographic encryption and reader authentication. It also includes standards for in the air – privacy concerns of interception. The third standard for the technology is the ISO-IEC-20248 which provides the guidelines for the digital – signature and bar code requirements.
The tags are simply labels, and the readers are two way transmitters for radio wave signals which transmit the signal to the tag and read the response that is sent by the tag. The tags that are mainly used are the active tags since they have their own ...
Energy efficient anti-collision algorithm for the RFID networksjournalBEEI
Energy efficiency is crucial for radio frequency identification (RFID) systems as the readers are often battery operated. The main source of the energy wastage is the collision which happens when tags access the communication medium at the same time. Thus, an efficient anti-collision protocol could minimize the energy wastage and prolong the lifetime of the RFID systems. In this regard, EPCGlobal-Class1-Generation2 (EPC-C1G2) protocol is currently being used in the commercial RFID readers to provide fast tag identification through efficient collision arbitration using the Q algorithm. However, this protocol requires a lot of control message overheads for its operation. Thus, a reinforcement learning based anti-collision protocol (RL-DFSA) is proposed to provide better time system efficiency while being energy efficient through the minimization of control message overheads. The proposed RL-DFSA was evaluated through extensive simulations and compared with the variants of EPC-Class 1 Generation 2 algorithms that are currently being used in the commercial readers. The results show conclusively that the proposed RL-DFSA performs identically to the very efficient EPC-C1G2 protocol in terms of time system efficiency but readily outperforms the compared protocol in the number of control message overhead required for the operation.
Evaluating feasibility of using wireless sensor networks in a coffee crop thr...IJCNCJournal
A Wireless Sensor Networks is a network formed with sensors that have characteristics to sensor an area to
extract a specific metric, depending of the application.
We would like to analyse the feasibility to use sensors in a coffee crop.In this work we are evaluating routing protocolsusing real dimensions and characteristics of a coffee crop. We evaluate, through simulation, AODV, DSDV and AOMDV and two variants known in this work as AODVMOD and AOMDVMOD with 802.15.4 MAC Protocol
.For this comparison, we defined three performance metrics: Packet Delivery Ratio (PDR), End-to-End Delay
and Average Energy Consumption. Simulation results show that AOMDVMOD overall, outperforms others
routing protocols evaluated, showing that is possible to use WSN in a real coffee crop environment.
Attending a job Interview for B1 and B2 Englsih learnersErika906060
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It is crucial for the taxpayers to understand about the TDS Return Filing Due Date, so that they can fulfill your TDS obligations efficiently. Taxpayers can avoid penalties by sticking to the deadlines and by accurate filing of TDS. Timely filing of TDS will make sure about the availability of tax credits. You can also seek the professional guidance of experts like Legal Pillers for timely filing of the TDS Return.
Improving profitability for small businessBen Wann
In this comprehensive presentation, we will explore strategies and practical tips for enhancing profitability in small businesses. Tailored to meet the unique challenges faced by small enterprises, this session covers various aspects that directly impact the bottom line. Attendees will learn how to optimize operational efficiency, manage expenses, and increase revenue through innovative marketing and customer engagement techniques.
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This 60-minute webinar, sponsored by Adobe, was delivered for the Training Mag Network. It explored the five elements of SPARK: Storytelling, Purpose, Action, Relationships, and Kudos. Knowing how to tell a well-structured story is key to building long-term memory. Stating a clear purpose that doesn't take away from the discovery learning process is critical. Ensuring that people move from theory to practical application is imperative. Creating strong social learning is the key to commitment and engagement. Validating and affirming participants' comments is the way to create a positive learning environment.
Falcon stands out as a top-tier P2P Invoice Discounting platform in India, bridging esteemed blue-chip companies and eager investors. Our goal is to transform the investment landscape in India by establishing a comprehensive destination for borrowers and investors with diverse profiles and needs, all while minimizing risk. What sets Falcon apart is the elimination of intermediaries such as commercial banks and depository institutions, allowing investors to enjoy higher yields.
Cracking the Workplace Discipline Code Main.pptxWorkforce Group
Cultivating and maintaining discipline within teams is a critical differentiator for successful organisations.
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Unveiling the Secrets How Does Generative AI Work.pdfSam H
At its core, generative artificial intelligence relies on the concept of generative models, which serve as engines that churn out entirely new data resembling their training data. It is like a sculptor who has studied so many forms found in nature and then uses this knowledge to create sculptures from his imagination that have never been seen before anywhere else. If taken to cyberspace, gans work almost the same way.
As a business owner in Delaware, staying on top of your tax obligations is paramount, especially with the annual deadline for Delaware Franchise Tax looming on March 1. One such obligation is the annual Delaware Franchise Tax, which serves as a crucial requirement for maintaining your company’s legal standing within the state. While the prospect of handling tax matters may seem daunting, rest assured that the process can be straightforward with the right guidance. In this comprehensive guide, we’ll walk you through the steps of filing your Delaware Franchise Tax and provide insights to help you navigate the process effectively.
Business Valuation Principles for EntrepreneursBen Wann
This insightful presentation is designed to equip entrepreneurs with the essential knowledge and tools needed to accurately value their businesses. Understanding business valuation is crucial for making informed decisions, whether you're seeking investment, planning to sell, or simply want to gauge your company's worth.
Discover the innovative and creative projects that highlight my journey throu...dylandmeas
Discover the innovative and creative projects that highlight my journey through Full Sail University. Below, you’ll find a collection of my work showcasing my skills and expertise in digital marketing, event planning, and media production.
"𝑩𝑬𝑮𝑼𝑵 𝑾𝑰𝑻𝑯 𝑻𝑱 𝑰𝑺 𝑯𝑨𝑳𝑭 𝑫𝑶𝑵𝑬"
𝐓𝐉 𝐂𝐨𝐦𝐬 (𝐓𝐉 𝐂𝐨𝐦𝐦𝐮𝐧𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬) is a professional event agency that includes experts in the event-organizing market in Vietnam, Korea, and ASEAN countries. We provide unlimited types of events from Music concerts, Fan meetings, and Culture festivals to Corporate events, Internal company events, Golf tournaments, MICE events, and Exhibitions.
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"𝐄𝐯𝐞𝐫𝐲 𝐞𝐯𝐞𝐧𝐭 𝐢𝐬 𝐚 𝐬𝐭𝐨𝐫𝐲, 𝐚 𝐬𝐩𝐞𝐜𝐢𝐚𝐥 𝐣𝐨𝐮𝐫𝐧𝐞𝐲. 𝐖𝐞 𝐚𝐥𝐰𝐚𝐲𝐬 𝐛𝐞𝐥𝐢𝐞𝐯𝐞 𝐭𝐡𝐚𝐭 𝐬𝐡𝐨𝐫𝐭𝐥𝐲 𝐲𝐨𝐮 𝐰𝐢𝐥𝐥 𝐛𝐞 𝐚 𝐩𝐚𝐫𝐭 𝐨𝐟 𝐨𝐮𝐫 𝐬𝐭𝐨𝐫𝐢𝐞𝐬."
Explore our most comprehensive guide on lookback analysis at SafePaaS, covering access governance and how it can transform modern ERP audits. Browse now!
Personal Brand Statement:
As an Army veteran dedicated to lifelong learning, I bring a disciplined, strategic mindset to my pursuits. I am constantly expanding my knowledge to innovate and lead effectively. My journey is driven by a commitment to excellence, and to make a meaningful impact in the world.
India Orthopedic Devices Market: Unlocking Growth Secrets, Trends and Develop...Kumar Satyam
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[Note: This is a partial preview. To download this presentation, visit:
https://www.oeconsulting.com.sg/training-presentations]
Sustainability has become an increasingly critical topic as the world recognizes the need to protect our planet and its resources for future generations. Sustainability means meeting our current needs without compromising the ability of future generations to meet theirs. It involves long-term planning and consideration of the consequences of our actions. The goal is to create strategies that ensure the long-term viability of People, Planet, and Profit.
Leading companies such as Nike, Toyota, and Siemens are prioritizing sustainable innovation in their business models, setting an example for others to follow. In this Sustainability training presentation, you will learn key concepts, principles, and practices of sustainability applicable across industries. This training aims to create awareness and educate employees, senior executives, consultants, and other key stakeholders, including investors, policymakers, and supply chain partners, on the importance and implementation of sustainability.
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1. Develop a comprehensive understanding of the fundamental principles and concepts that form the foundation of sustainability within corporate environments.
2. Explore the sustainability implementation model, focusing on effective measures and reporting strategies to track and communicate sustainability efforts.
3. Identify and define best practices and critical success factors essential for achieving sustainability goals within organizations.
CONTENTS
1. Introduction and Key Concepts of Sustainability
2. Principles and Practices of Sustainability
3. Measures and Reporting in Sustainability
4. Sustainability Implementation & Best Practices
To download the complete presentation, visit: https://www.oeconsulting.com.sg/training-presentations
Sustainability: Balancing the Environment, Equity & Economy
10.1.1.150.595
1. 1
Efficient Tag Detection in RFID Systems
Bogdan Carbunar
, Murali Krishna Ramanathan
¡
, Mehmet Koyut¨urk
¢
,
Suresh Jagannathan
¡
and Ananth Grama
¡
Motorola Labs
1295 E. Algonquin Rd. IL05 2nd Floor
Schaumburg, IL 60195
Email:carbunar@motorola.com
¡
Department of Computer Science
Purdue University, West Lafayette, IN 47907
Email:
£
rmk, suresh, ayg¤ @cs.purdue.edu
¢
Department of Electrical Engineering and Computer Science
Case Western Reserve University, Cleveland, OH 44106
Email:koyuturk@eecs.case.edu
2. 2
Abstract
Recent technological advances have motivated large-scale deployment of RFID systems. However, a number
of critical design issues relating to efficient detection of tags remain unresolved. In this paper, we address three
important problems associated with tag detection in RFID systems: (i) accurately detecting RFID tags in the presence
of reader interference (reader collision avoidance problem); (ii) eliminating redundant tag reports by multiple readers
(optimal tag reporting problem); and (iii) minimizing redundant reports from multiple readers by identifying a
minimal set of readers that cover all tags present in the system (optimal tag coverage problem). The underlying
difficulties associated with these problems arise from the lack of collision detection mechanisms, the potential
inability of RFID readers to relay packets generated by other readers, and severe resource constraints on RFID
tags. in this paper we present a randomized, distributed and localized Reader Collision Avoidance (RCA) algorithm
and provide detailed probabilistic analysis to establish the accuracy and the efficiency of this algorithm. Then, we
prove that the optimal tag coverage problem is NP-hard even with global knowledge of reader and tag locations.
We develop a distributed and localized Redundant Reader Elimination (RRE) algorithm, that efficiently identifies
redundant readers and avoids redundant reporting by multiple readers. In addition to rigorous analysis of performance
and accuracy, we provide results from elaborate simulations for a wide range of system parameters, demonstrating
the correctness and efficiency of the proposed algorithms under various scenarios.
3. 3
I. INTRODUCTION
Radio Frequency Identifier (RFID) is an increasingly deployed technology for tagging and uniquely identifying
objects. Unlike barcodes, RFID enables simultaneous detection of multiple, distant, and non-line-of-sight objects.
There are hundreds of millions of RFID tags currently deployed; it is believed that this number will reach tens of
billions within seven years [1]. The use of RFID systems is primarily motivated by their net savings, low deployment
cost, and accuracy. As an example, Wal-Mart anticipates savings of billions of dollars from tagging pallets and
individual products, while the International Air Transport Association (IATA) projects annual industry savings of
$760 Million from RFID luggage tags [2]. Apparel vendor Gap documented an increase of accuracy from 85% to
99.9% when using RFID technology [3].
RFID systems have two types of components, RFID transponders (tags), placed on objects and RFID transceivers
(tag readers). RFID tags store information using a small integrated circuit and communicate using an antenna. RFID
readers are capable of reading the information stored on tags placed in their vicinity and communicate it to a host
computer. Most tags are passive, i.e., they do not require battery power. Instead, passive tags use the energy of the
reader’s signal to fetch, process, and communicate stored data.
The past few years have witnessed tremendous advances in RFID technology beyond reduction in size and price
of components. Notably, diverse solutions for wireless readers are now supported, including quarter-sized wireless
readers [4] compatible with Crossbow [5] sensors, Bluetooth enabled readers [6], SD card reader/writers [7], and
reader enabled phones [8]. These developments broaden the scope and utility of RFID systems, enabling their
on-line deployment. On the other hand, convenient, remote ad hoc deployment of wireless readers poses several
problems.
Reader Collision Avoidance: One problem, reader collision [9], occurs when co-located readers are simul-
taneously active. Specifically, reader collisions occur at tags situated in the vicinity of two or more readers that
simultaneously interrogate tags. Such tags may be unable to correctly decode reader queries, leading to undesirable
behavior. Consider, for example, the reader and tag deployment in Figure 1. In the figure, readers are represented
by dots, tags are represented by crosses, and the interrogation zone of a reader is represented by circles centered
around readers. If readers
and
¡
interrogate tags at the same time, neither of them may detect tag ¡
. This is
because ¡
resides at the intersection of interrogation zones of the two readers, and consequently responds to both
of their queries. This causes existing tag detection protocols to potentially report incorrect data, or to not terminate
at all.
Current protocols for avoiding reader collisions are based either on time scheduling of reader transmissions,
spatial isolation of readers or frequency assignment to readers, or a combination of these techniques. Solutions may
either require a centralized entity or are completely decentralized.
6. 6
Optimal Tag Coverage: We further introduce and study the related optimal tag coverage problem. This
problem follows from the observation that a reader that covers only tags covered by other readers as well, is
redundant2
. Consequently, the number of readers that need to use their wireless interface can be minimized by
identifying a minimal subset of readers in which no reader is redundant (with respect to the subset). This is the
optimal tag coverage problem, as illustrated in Figure 1. Observe that all readers except
in this deployment are
redundant. On the other hand, the minimum number of readers that need to report detected tags to ensure complete
tag coverage is two, since no reader is redundant in the set
¢¡
¡¤£ .
We first prove that even with centralized knowledge of tag distribution and reader deployment, the problem of
finding the optimal number of readers that need to report tags is NP-hard. We then propose RRE, a decentralized and
localized algorithm for the optimal tag coverage problem. Similar to RCA, RRE requires only basic reader-to-tag
communication capabilities. Furthermore, we show that a side effect of RRE is to allow each tag to be reported by
a single reader, effectively eliminating redundant tag reports, i.e., providing a solution to the optimal tag reporting
problem.
Our simulation results show that the performance of RRE is close to that of a centralized greedy heuristic for the
minimum set cover problem. We also show that, by ensuring that each tag is reported only once, RRE generates a
significantly lower number of (redundant) tag reports. Specifically, RRE generates between 20% and 600% fewer
tag reports than a protocol that does not eliminate redundancy.
This paper is organized as follows: we present background material, the RFID system model, and the problems
addressed in this work in Section II. In Section III, we discuss related work. Section IV describes a randomized
querying technique for avoiding reader collisions, used in both RCA and RRE. The technique is described in the
context of RCA. We prove the NP-hardness of the optimal tag coverage problem in Section V and present the
details of our solution, RRE, in Section VI. Simulation results of both algorithms are presented in Section VII. We
conclude our discussion in Section VIII.
II. PRELIMINARIES
We initiate our discussion with an overview of RFID systems and the capabilities of existing tags and readers. In
Section II-B, we briefly describe the tree walking algorithm for resolving tag collisions. In Section II-C, we formally
define the problems addressed in this paper. Finally, in Section II-D, we describe the system model considered.
7. 7
R3
T5
R2 T4 R4
R1
R5
R6
T1
T2
T3
Backend system Backend system
R3
T5
R2 T4 R4
R1
R5
R6
T1
T2
T3
(a) (b)
Fig. 2. Example of redundant tag reporting. Readers are denoted by small filled circles and their RF interrogation zones by larger disks.
Dotted arrows represent cellular links and plain arrows represent reader-to-reader wireless links. Small rectangles represent tags. (a) Wireless
readers may only communicate with the host system. If readers report tags directly to the host server, readers ¡ and ¡ can safely not
transmit. If they do, the duplicate tag reports are eliminated by the host system. (b) The same reader and tag placement but wireless readers
may now communicate with each other and with the host system. The root node £¢ needs to communicate with the host system. All other
readers route their reported tags toward ¢ . If £¡ , ¥¤ and all communicate their detected tags, tags ¦£¡ , ¦¥¤ , ¦ and ¦¡¤ are reported more
than once. While the duplicate reports of ¦ and ¦¡¤ can be eliminated by reader £¥ , duplicate reports of tags ¦£¡ and ¦¥¤ will be forwarded
by both readers ¥ and ¤ and the duplicates eliminated only by ¦¢ . This generates 4 transmissions, instead of only 2.
A. Overview of RFID Systems
RFID tags contain limited memory resources for storing unique identification, and information relating to the
objects with which they are associated (attached). They also contain an antenna, used for communication with
readers. There are two kinds of tags: passive and active. Passive tags do not need batteries, but are powered by RF
energy from the reader. In addition to the memory chip and antenna, active tags are equipped also with a battery
and a transmitter, allowing them to initiate transmissions.
While active tags have a greater communication range and can operate autonomously, they are more expensive.
The price efficiency of tags is the dominant factor determining their wide deployment. Most current RFID appli-
cations use only passive tags, thus, this paper focuses on passive tags. For most tags, the chip and antenna are
mounted on a base and encapsulated with thermoplastic. Their length ranges from 1/16 inch to more than 6 inches.
Tags can be paper thin or embedded into materials allowing them to withstand high temperatures and chemical
environments. They can be flexible enough to be embedded within an adhesive label and run through a printer.
Most RFID systems use either the low frequency LF (125 - 134.2 kHz and 140 - 148.5 kHz), high frequency
2
In multi-hop wireless reader networks, redundant readers may still need to use their wireless interface to forward tags detected by other
readers. In this case, however, eliminating duplicate tag reports is even more important, since redundancy may generate a large number of
transmissions.
8. 8
HF (13.56 MHz) or ultra high frequency domains UHF (860-960 MHz) for transmission. HF tags typically cost
less and are better suited for tagging water or liquid-bearing objects because the longer wavelengths of HF systems
are less susceptible to absorption. A UHF tag can be made to work in these conditions, but its effective read
range is dramatically reduced. The ISO/IEC 15693 standard has enabled the global acceptance of 13.56 MHz RFID
technology. Examples of HF tags include TI’s Tag-It HF-1, Philips’ I-Code SLI, Infineon’s my-d SRF55VxxP or
ST Microelectronics’ LRI512. These tags have factory programmed 64 bit identifiers and between 112 and 1000
bytes of memory available for read/write operations.
Signals from RFID readers activate compatible tags within their interrogation zone. The interrogation zone is
defined to be the area around a reader where tags can receive the reader’s signal, process it and send back a response
that can be correctly decoded by the reader. The information decoded by the reader is passed to host computing
systems where it is further processed, according to the application. In addition to locating, activating, and receiving
transmissions from RFID tags, RFID reader-writers also have the ability to send data back to read/write-capable
tags in order to append or replace data.
Readers may themselves be fixed or portable. Fixed readers are usually attached to antennae that are designed to
detect the tags within a specified area. These units typically collect data from products traveling through loading
dock doors, conveyor belts, gates and doorways, or even cars on tollways. Portable, wireless readers can be moved
to detect remote tags, in areas where wiring or antenna placement could be difficult. Readers with various wireless
communication capabilities exist in today’s market. SkyeTech’s SkyeRead M1 [4] reader is compatible with Mica
Motes [5] and IDBlue [6] is a handheld Bluetooth 13.56MHz RFID reader, compatible with devices ranging from
PDAs to PCs. Major cellular phone manufacturers provide phones with embedded RFID readers [8].
The size, portability, and price of such wireless readers motivates their deployment and organization into ad hoc
networks. The network can not only detect tags but also relay tag reports of remote readers toward the host system.
Several applications benefit from arbitrary deployments of reader networks, including supply chain management,
warehouse management [13], baggage management in airports [14], [2], and tracking participants at marathons [15].
In an arbitrary deployment the placement of readers does not follow pre-defined constraints so no assumptions about
the location or interference patterns of readers can be made.
Reader networks are currently supported by a number of vendors. PGS Electronics [16] provides a com-
plete solution for wireless RFID integration and Reva Systems [17] recently proposed a protocol called Simple
Lightweight RFID Reader Protocol (SLRRP). SLRRP defines how readers convey configuration, control, status, and
tag information between RFID reader network device managers and other readers in an IP-based network, either
wired or wireless.
We consider two models of wireless reader network deployments, each with a different set of networking
9. 9
capabilities. While the results presented in this paper are not restricted to these models, we believe them to be of
independent value.
The first model considers only the deployment of RFID readers that are equipped with cellular interfaces (e.g.,
RFID enabled cellphones) and is illustrated in Figure 2(a). Such readers may locally detect tags and then report
them to the host system using their cellular data link. Readers are assumed to be unable to communicate with
each other, except through the host system. The second model considers the deployment of WLAN, Bluetooth, or
802.15.4 readers, that are able to locally communicate3
. In this model, depicted in Figure 2(b), only a subset of the
readers communicate directly to the host, forming a backbone of the reader network. The other readers establish
ad-hoc paths to backbone readers and forward tags reported by other readers. In this model, redundant tag reports
may be more damaging than in the first model, since redundant tags may be propagated several hops before being
eliminated (see Figure 2(b) for an example).
B. Tree Walking: An Algorithm for Detecting Tags in the Presence of Collisions
RFID readers have the ability to accurately read (and report) data stored at multiple tags placed within their
interrogation zone. Since readers broadcast their queries, multiple tags may end up responding simultaneously,
leading to interference and inaccurate decoding of responses. This is known as the tag collision problem. Note that
tag collision and reader collision are different problems.
Several techniques have been proposed to solve the tag collision problem. A popular solution, known as the tree
walking algorithm (TWA) [18] is based on recursive traversal of the binary name tree of tag identifiers. The reader
initially sends a broadcast query containing the “0” string. All tags in its interrogation zone whose identifier starts
with a “0” bit reply. If a reply is received, or a tag collision is detected, the reader recurses on both subtrees of “0”,
rooted at “00” and “01”. However, if no reply is received, the reader concludes the absence of “0”-prefixed tags in
its interrogation zone and subsequently sends a “1” query. For a reader, the complexity of TWA is proportional to
the number of tags present in its interrogation zone and to the length of the binary representation of tag identifiers.
While TWA was designed to accurately read tag identifiers, it can also be used to read arbitrary data stored on
tags, as long as the data’s bit length is the same across all tags.
C. Reader Collision: Problem Definition
The tag collision problem occurs when one reader simultaneously interrogates multiple tags. In large scale
environments, such as retail spaces, the interrogation zone of a single reader may not cover all the tags. Furthermore,
tags can be randomly placed or moving. In such cases, accurate detection of all tagged objects requires (possibly
3
Many existing cellphones are equipped with Bluetooth and/or WLAN communication capabilities
12. 12
1000 bytes. Moreover, tags are capable of performing comparison and prefix matching. Prefix matching is
a requirement of the tree walking algorithm (see Section II-B) and the circuits performing comparison are
similar in functionality and complexity.
Furthermore, we assume that any reader is able to detect tag collisions, occurring when multiple tags respond to
one of its queries. In fact, this is a basic assumption necessary for any algorithm that resolves tag collisions and is
a requirement for the tree walking algorithm described in Section II-B.
III. RELATED WORK
We briefly describe related results on various aspects of the problems investigated here.
A. Collisions in RFID Systems
The reader-collision problem in RFID systems was first documented in [9]. The solution proposed, of allocating
different frequencies to interfering readers, is centralized. A simple decentralized version, where readers listen for
collisions and use randomized backoff when detecting one, is discussed. In contrast, our work assigns different time
slots for transmitting readers. Furthermore, our solution guarantees with high probability (w.h.p.) that each reader
is able to correctly read all the tags placed in its interrogation zone.
Another decentralized solution for the reader collision problem was proposed by the same group (Waldrop et
al [10]) shortly after. They proposed two decentralized MAC protocols for reader networks whose purpose is to
allocate disjoint time slots (colors) for reader transmissions. The first protocol is the Distributed Color Selection
(DCS) algorithm and the second one is Colorwave, or the Variable-Maximum Distributed Color Selection (VDCS)
algorithm. The DCS/VDCS protocols are based on the existence of an interference graph whose links denote
interference between the end-points corresponding to readers. That is, each reader is assumed to have knowledge
of the other readers with whom its transmissions interfere. This knowledge does not restrict itself to identification
data, but also requires interfering readers to be able to communicate with each other. In DCS, a reader that
needs to transmit does so only during its color timeslot. If a collision occurs, the transmission is aborted and the
reader changes color (timeslot). Furthermore, it reserves the newly chosen color by contacting all its neighbors
(from the interference set) and asking each to (randomly) choose a new color if there is a color conflict. DCS
assumes a maximum value for the number of colors, which however proves detrimental if the probability of readers
transmitting changes in time. The VDCS algorithm addresses this problem by dynamically allowing nodes to change
the maximum number of colors.
The problem of the DCS/VDCS protocols is that they rely on the interference graph. Building this graph is
a difficult problem in itself. One way of building it would be to perform manual RF site surveys, however, this
solution requires significant human intervention. Another solution would to schedule reader transmissions such that
13. 13
at any time only two readers transmit and the rest listen. At the end of the process, each reader communicates
interference data to the pairs of readers whose transmissions interfered. This solution is time consuming and
transmission intensive (
¢¡
¡¤£ pairs of readers). It also requires a centralized deployment of the schedule. Finally and
most importantly, the interference data would be incomplete, since the interference would only be measured at
reader locations, instead of tag locations.
Ho et al. [19] have similarly studied the problem of minimizing reader collisions. The solution proposed, HiQ,
learns the collision patterns of readers and assigns frequencies over time such that neighboring readers do not
experience collisions. They made the observation that Colorwave, proposed by a subset of the authors of HiQ, while
being able to dynamically adjust to changes in the environment, was unable to take advantage of the coordination and
optimization that would be possible using a global view of the network. However, since a centralized solution offers
a single point of communication and failure, HiQ is hierarchical, allowing for greater scalability and fault tolerance.
Specifically, each reader communicates with a single “R-server”. R-servers are responsible for preventing collisions
between the readers that report to them. Each reader is assumed to be able to detect collisions with neighboring
readers, then communicate the number and type of collisions detected (either frequency or tag collisions) and its
successful reads to its R-reader. An R-reader feeds the collision patterns learned from readers into a dynamic
on-line algorithm that then allocates resources (time slots and frequencies) back to the readers. R-servers are
allocated a limited number of resources by a “Q-server”, which is he highest element of the HiQ hierarchy. Each
R-server communicates with a single Q-server, requesting additional resources or reporting collisions. Q-servers
may e hierarchically organized, with a single root Q-server. Each Q-server allocates resources to the Q-servers and
R-servers that are below it in the hierarchy, using a dynamic Q-learning algorithm. The algorithm infers collision
constraints between readers based on reported collision information and from the requests for additional resources.
While HiQ is decentralized, it relies on additional hardware, namely the R-servers and Q-servers. Our algorithm,
RCA, makes no such demands and also requires much less communication with the backend system.
The Slotted Scheduled Tag Access protocol (SSTA) of Zhou et al. [11] is a hybrid between spatial, time and
frequency division MAC protocols for RFID systems. It assumes a planned deployment of the reader network,
where it is possible to perform RF site surveys and measure reader location and interference patterns. Moreover,
once this information is collected, it is processed at a central location and each reader is assigned its resulting
schedule. The problem is first studied under the assumption that no tag spatial distribution is known. The solution
proposed greedily activates a set of non-interfering readers in each time slot, such that a maximum possible amount
of new area is covered in each slot. When the spatial distribution of tags is known, the solution is made more
effective by the fact that the time to read all tags in a given area can be easily approximated. Note that the authors
propose solutions to the problem both in the single channel and in the multi-channel scenarios. The problems of
14. 14
the SSTA protocols stem from their limited applicability to models where the location and interference patterns of
readers are known to a central computing facility. They cannot be applied to scenarios where this information is
difficult or too expensive to collect.
Note that both Colorwave and HiQ are dynamic protocols, in the sense that they take as input read requests
from readers and then try to allocate resources (slots or frequencies) on the fly to the requesting readers and those
interfering with them. The SSTA algorithm is static, since it uses information collected from the deployed network
in order to once and for all determine reader resource assignments. Our protocol, RCA, is a randomized protocol,
where each reader attempts to perform a read operation multiple times at randomly chosen time slots. Thus, RCA
is a dynamic algorithm, which however requires no assistance from other servers or readers.
Deolalikar et al. [12] take an ingenious, graph-theoretic approach at the problem of assigning resources (time
slots or frequencies) to readers whose transmissions interfere. The input to their solution is also an interference
graph of the reader network. The authors make the observation that a bipartite interference graph is the easiest
to schedule, by firing for a read operation first the readers in one partition and then the readers in the second
partition. When more resources are available (e.g., time slots or frequency channels) k-partite graphs are a better
alternative since they are easier to derive from a reader network. The problem then is to efficiently transform an
interference graph into a k-partite (or bi-partite) graph. The authors make the observation that this transformation
can be performed in a succession of steps, where each step is either (i) an elimination of a collision constraint by
moving the endpoint readers apart or (ii) an elimination of a reader. They then propose heuristics for choosing the
best edge or verted for removal from the interference graph, based on a measure called “correlation” of readers.
The correlation of two readers consists of the number of tags covered by both readers. Namely, for edge removals,
first the edges between readers with the highest correlation are removed. For vertex removals, first the readers
with highest correlations with their neighbors are removed. Such readers are essentially what we call in this paper
redundant readers. Thus, besides the aforementioned problem of requiring the existence of an interference graph,
this solution attempts to solve the redundant reader problem (or at least count the tags covered by each reader and
build a correlation table for each neighbor) before solving the reader collision problem, that is, before being able
to read the tags. The authors do not provide a solution for building neither the interference graph nor the reader
correlation values.
Birari and Iyer [20] proposed Pulse, a protocol that addresses reader collisions through the use of a “control”
channel. Since the interference range of readers exceeds their transmission range, Pulse requires readers to send
control data at a higher power, in order to allow for inter-reader communication. With this capability, the Pulse
protocol allows readers to communicate with other readers with whom they are interfering. Then, readers can reserve
the channel for a tag reading session, by periodically sending a beacon. If a reader does not receive beacons for
15. 15
a certain interval (constant time + random interval) it can signal its intent to read tags by sending beacons. Using
a higher power for transmissions over the control channel also generates a much larger interference range, which
can disturb the tag reading processes of readers that are even farther away. Moreover, this process also consumes
more power and power consumption increases superlinearly with the transmission range.
B. Coverage Problems in Sensor Networks
The problem of coverage of a set of entities has been studied in a variety of contexts. In the area of wireless sensor
networks, Tian and Georganas [21] present an algorithm for detecting sensors whose coverage area is completely
covered by other sensors. A sensor turns itself off only when each sector of its coverage disk is covered by
another sensor. Zhang and Hou [22] provide a distributed algorithm for extending the network lifetime by turning
off “redundant” sensors. Their mechanism for deciding a sensor to be redundant requires a sensor to divide its
coverage area into small grids and then using a bitmap to indicate whether the center of each square of the grid is
covered by some other sensor. Ye et al. [23] present an algorithm that extends the network lifetime by maintaining
a necessary set of working sensors and turning off redundant ones. A sensor is alternatively sleeping or active.
When a sensor wakes up, if it has an active sensor inside its transmission range, it turns off again. Slijepcevic and
Potkonjak [24] introduce a centralized algorithm for finding the maximum number of disjoint subsets of sensors,
where each subset completely covers the same area as the entire set of sensors. Carbunar et al. [25] proposed the use
of Voronoi diagrams to determine in a distributed and locallized manner the redundancy of sensors. Sensors only
need the knowledge of their Voronoi cells, including the identities of the sensors that are their Voronoi neighbors.
All of the above results use a definition of coverage in terms of continuous areas. Our goal is however to detect
a discrete set of points in the coverage area of a reader network. Furthermore, we define coverage only in terms
of the set of discrete points, tags. While this approach has the potential to discover more redundant readers, the
problem is complicated by the scarce resources of tags.
C. Medium Access Control Issues
Medium Access Control protocols for wired and wireless networks share several details with our reader collision
avoidance algorithm. The first MAC protocol, proposed for packet radio networks, is ALOHA [26]. When the
transmission of a node results in collision, the node must wait for a random interval before retransmitting. However,
RFID systems do not have the mechanisms to detect collisions occurring at tags, making ALOHA unsuitable for
avoiding reader collisions. Multiple access with collision avoidance (MACA) [27] is a protocol that employs a
handshake to avoid hidden-node problems. The sender broadcasts an RTS message and the receiver replies with
a CTS message. All the nodes that hear the RTS and CTS messages delay their transmissions. Such a protocol
cannot be used in RFID system, since the purpose of a reader is to detect all the tags in its interrogation zone. Such
17. 17
impact of reader collisions.
A reader divides time into disjoint epochs and each epoch is further divided into multiple disjoint time frames.
The duration of a time frame is set to exceed the time a reader query needs to reach a reader’s entire interrogation
zone, plus the time a tag needs to process a query (one string comparison) and the time a tag answer needs to reach
back the reader. During each epoch, a reader picks a frame uniformly at random and sends its query in that frame.
This ensures that the queries of any two, potentially interfering readers will collide only if both readers choose the
same time frame during the current epoch. If no tag answer is received, the reader repeats the query in a randomly
chosen time frame of the next epoch. If a reader collision at matching tags has occurred during the query, the query
duplication correlated with the random backoff decreases the chances of repeated reader collisions.
This is illustrated in Figure 3. In Section IV-A, we prove that if the number of time frames per epoch is equal
to the number of readers, , and a query is not answered
¨¢¡¤£¦¥
times, then w.h.p., there are no tags matching
the query in the interrogation zone of the reader. If, however, an answer is received, either as a clear tag response
or by detecting a tag collision, in the next epoch the reader recursively moves to the next query, as in the TWA
algorithm.
Note that readers cannot and do not need to detect tag collisions. If after a query a reader receives no reply, it
means that either (i) there is no tag matching the query’s prefix string or that (ii) a collision has occurred. After a
single query without a reply, the reader cannot differentiate between these two cases. After
¡ £¦¥
queries, if still no
answer has been received, the reader can conclude with high probability the fact that no tag matching the query lies
in its interrogation zone. This result shows that having tag collisions for all of these queries is highly improbable,
indicating that the tag collision problem will be avoided without having to detect any collision.
The readers need then to know the value of in order to set the number of frames per epoch to the appropriate
value. Since the readers are deployed by a single entity their number may be provided to each reader before
deployment. If new readers are later deployed or existing readers have been detected as inactive (due to exhausted
battery or physical faults) readers may be provided by the central host with new estimates of the number of readers.
Depending on the network model (see Section II-A), this operation can be performed either over the cellular link
between the central host and individual readers or over the cellular link for the backbone readers who then propagate
this information to the other readers using inter-reader communication capabilities.
The choice of using frames per epoch and of repeating a query
¨¢¡¤£¦¥
times is made under the conservative
assumption that all readers interfere with each other at all tags. Hence, the bound that we provide is the worst case
bound with respect to the distribution of tags and deployment of readers. However, this is not always the case. In
our experiments (see Section VII), we show that in realistic scenarios of random deployment of readers and tags,
much fewer frames per epoch and repetitions per query are needed in order to allow readers to accurately detect
30. 30
5
10
15
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25
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35
0 50 100 150 200 250 300 350 400 450 500
replacements
)
RCA
All tags
Worst case
Averagenumberoftagsdetectedquery repetitions
essages per reader
)
frames per epoch
TWA
Worst case
etitions per query
es generated ( )
Number of tags
Number of readers
s per reader ( )
t readers detected
RRE
GREEDY
nterrogation zone
Worst case
ported by a reader
ported by a reader
r of tags reported
t readers detected
nterrogation zone
100
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10000
0 50 100 150 200 250 300 350 400 450 500
PSfrag replacements
)
RCA
All tags
Worst case
Average number of tags detected
Number of query repetitions
Average number of messages per reader
)
Number of time frames per epoch
TWA
Worst case
Average number of repetitions per query
Average number of messages generated ( )
Number of tags
Number of readers
Averagenumberofmessagesperreader(
¡ ¢
)
Number of redundant readers detected
RRE
GREEDY
Radius of reader interrogation zone
Worst case
Average number of tags reported by a reader
Average number of tags reported by a reader
Number of tags reported
Number of redundant readers detected
Radius of reader interrogation zone
(a) (b)
Fig. 8. Scalability of RCA and TWA when the number of readers increases from 10 to 500, for 4000 tags.
TWA has 14% accuracy. Fig. 7(b) shows the corresponding number of messages per readers generated by the two
algorithms, on a logarithmic scale, compared to the total number of messages per reader generated by RCAv.1.
While RCA generates 10 times more messages than TWA, this is simply due to the fact that TWA performs 3
times less query types than RCA. This is also the reason for TWA’s inaccuracy. However, RCA halves the number
of messages generated by RCAv.1, by not repeating answered queries.
In order to evaluate the reader scalability of RCA and TWA, we place 4000 tags and increase the number of
readers randomly deployed from 10 to 500. The interrogation radius of readers is set to 50 units. Fig. 8(a) shows
the accuracy of RCA and TWA. For a small number of readers, TWA accurately detects the tags deployed in
the interrogation zone of readers. This is because the interrogation zones of readers barely intersect, practically
eliminating reader collisions. However, as the number of readers increases, effectively increasing the overlapping
areas of the interrogation zones of readers, the accuracy of TWA constantly decreases. In contrast, RCA, by using
¡¤£¦¥
epochs per query is accurate, consistently discovering all the tags deployed. This accuracy comes at the
expense of more messages. Fig. 8(b) shows the corresponding average number of messages generated by RCA,
TWA and RCAv.1. The values are shown on a logarithmic scale. As observed in the previous experiment, TWA is
message efficient, since few queries are successful, leaving unexplored most of the name space of tags. However,
the number of messages generated by RCA quickly saturates to roughly half of the messages generated by RCAv.1.
The last experiment evaluates the performance of RCA when the interrogation radius of readers increases from 40
units to 100 units, while the number of readers randomly deployed is 500 and the number of tags is 4000. Fig. 9(a)
shows the accuracy of RCA compared with TWA. RCA discovers all the tags until the interrogation radius reaches
85 units. However, even for an interrogation radius of 100 units, RCA has a 94% accuracy. As the interrogation
radius increases so does the size and number of intersections of interrogation zones of readers. Since the number
of epochs per query,
¡¤£¦¥
and the number of time frames per epoch is constant, more collisions are generated,
leading to a decreased accuracy. However, the performance of TWA is significantly inferior. When the interrogation
31. 31
0
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80
100
120
40 50 60 70 80 90 100
replacements
)
RCA
All tags
Worst case
Averagenumberoftagsdetected
query repetitions
essages per reader
)
frames per epoch
TWA
Worst case
etitions per query
es generated ( )
Number of tags
Number of readers
s per reader ( )
t readers detected
RRE
GREEDY
Radius of reader interrogation zone
Worst case
ported by a reader
ported by a reader
r of tags reported
t readers detected
nterrogation zone
100
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100000
40 50 60 70 80 90 100
PSfrag replacements
)
RCA
All tags
Worst case
Average number of tags detected
Number of query repetitions
Average number of messages per reader
)
Number of time frames per epoch
TWA
Worst case
Average number of repetitions per query
Average number of messages generated ( )
Number of tags
Number of readers
Averagenumberofmessagesperreader(
¡ ¢
)
Number of redundant readers detected
RRE
GREEDY
Radius of reader interrogation zone
Worst case
Average number of tags reported by a reader
Average number of tags reported by a reader
Number of tags reported
Number of redundant readers detected
Radius of reader interrogation zone
(a) (b)
Fig. 9. Performance of RCA and TWA when the interrogation zone radius of readers increases from 40 units to 100 units, for 500 readers
and 4000 tags.
120
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1000 2000 3000 4000 5000 6000 7000 8000
RRE
GREEDY
replacements
)
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All tags
Worst case
r of tags detected
query repetitions
essages per reader
)
frames per epoch
TWA
Worst case
etitions per query
es generated ( )
Number of tags
Number of readers
s per reader ( )
Numberofredundantreadersdetected
RRE
GREEDY
nterrogation zone
Worst case
ported by a reader
ported by a reader
r of tags reported
t readers detected
nterrogation zone
t readers detected
0
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15000
20000
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35000
1000 2000 3000 4000 5000 6000 7000 8000
RRE
NORMAL
PSfrag replacements
)
RCA
All tags
Worst case
Average number of tags detected
Number of query repetitions
Average number of messages per reader
)
Number of time frames per epoch
TWA
Worst case
Average number of repetitions per query
Average number of messages generated ( )
Number of tags
Number of readers
Average number of messages per reader ( )
Number of redundant readers detected
RRE
GREEDY
Radius of reader interrogation zone
Worst case
Average number of tags reported by a reader
Average number of tags reported by a reader
Numberoftagsreported
Number of redundant readers detected
Radius of reader interrogation zone
Number of redundant readers detected
(a) (b)
Fig. 10. Performance of RRE when the number of tags randomly deployed increases from 1000 to 8000. Throughout this experiment 500
readers are randomly deployed, each with an interrogation radius of 50 units. (a) Number of redundant readers discovered by RRE and
GREEDY. (b) Number of tags reported by RRE and by NORMAL.
radius of readers is 100 units, readers running TWA discover only 5% of the tags detected by readers running
RCA. Fig. 9(b) shows the corresponding number of messages generated by the same algorithms. It confirms the
results shown in Fig. 7(b) and Fig. 8(b). TWA generates only a fraction of the messages generated by RCA, since
the number of queries correctly detected as successful is very small. However, we consistently reduce the number
of messages sent by eliminating repetitions of successful queries.
B. Efficiency of RRE
We investigate the performance of our redundant-reader detection algorithm by comparing it with the centralized
greedy approximation algorithm, GREEDY, described in Section VI. The performance of GREEDY is expected to be
better than that of the proposed distributed and localized algorithm, RRE, since GREEDY makes all decisions based
on global information. However, it should be noted that GREEDY is difficult and often impractical to implement,
since it requires centralized knowledge of the reader topology.
We also compare the performance of RRE in terms of the total number of tags that are reported by the system,