Showing papers in "Mobile Networks and Applications in 2007"
TL;DR: One major application in pervasive healthcare, termed comprehensive health monitoring is presented in significant details using wireless networking solutions of wireless LANs, ad hoc wireless networks, and, cellular/GSM/3G infrastructure-oriented networks.
Abstract: With an increasingly mobile society and the worldwide deployment of mobile and wireless networks, the wireless infrastructure can support many current and emerging healthcare applications. This could fulfill the vision of "Pervasive Healthcare" or healthcare to anyone, anytime, and anywhere by removing locational, time and other restraints while increasing both the coverage and the quality. In this paper, we present applications and requirements of pervasive healthcare, wireless networking solutions and several important research problems. The pervasive healthcare applications include pervasive health monitoring, intelligent emergency management system, pervasive health-care data access, and ubiquitous mobile telemedicine. One major application in pervasive healthcare, termed comprehensive health monitoring is presented in significant details using wireless networking solutions of wireless LANs, ad hoc wireless networks, and, cellular/GSM/3G infrastructure-oriented networks. Many interesting challenges of comprehensive wireless health monitoring, including context-awareness, reliability, and, autonomous and adaptable operation are also presented along with several high-level solutions. Several interesting research problems have been identified and presented for future research.
704 citations
TL;DR: A prototype application that tracks the daily exercise activities of people, using an Artificial Neural Network to analyse GSM cell signal strength and visibility to estimate a user’s movement is described.
Abstract: This paper explores the potential for use of an unaugmented commodity technology--the mobile phone-- as a health promotion tool. We describe a prototype application that tracks the daily exercise activities of people, using an Artificial Neural Network (ANN) to analyse GSM cell signal strength and visibility to estimate a user's movement. In a short-term study of the prototype that shared activity information amongst groups of friends, we found that awareness encouraged reflection on, and increased motivation for, daily activity. The study raised concerns regarding the reliability of ANN-facilitated activity detection in the 'real world'. We describe some of the details of the pilot study and introduce a promising new approach to activity detection that has been developed in response to some of the issues raised by the pilot study, involving Hidden Markov Models (HMM), task modelling and unsupervised calibration. We conclude with our intended plans to develop the system further in order to carry out a longer-term clinical trial.
261 citations
TL;DR: The objective in this paper is to survey how the existing research-based and commercial-based sensor nodes are suitable for this purpose, analyzing how the hardware can influence the provision of the primitives and how software implementations tackles the task of implementing instances of those primitives.
Abstract: In a wireless sensor network environment, a sensor node is extremely constrained in terms of hardware due to factors such as maximizing lifetime and minimizing physical size and overall cost. Nevertheless, these nodes must be able to run cryptographic operations based on primitives such as hash functions, symmetric encryption and public key cryptography in order to allow the creation of secure services. Our objective in this paper is to survey how the existing research-based and commercial-based sensor nodes are suitable for this purpose, analyzing how the hardware can influence the provision of the primitives and how software implementations tackles the task of implementing instances of those primitives. As a result, it will be possible to evaluate the influence of provision of security in the protocols and applications/scenarios where sensors can be used.
128 citations
TL;DR: A prototype context aware perioperative information system to capture and interpret data in an operating room of the future that seeks to automate some of the tasks done by nursing staff today that detracts from their ability to attend to the patient.
Abstract: We describe a prototype context aware perioperative information system to capture and interpret data in an operating room of the future. The captured data is used to construct the context of the surgical procedure and detect medically significant events. Such events, and other state information, are used to automatically construct an electronic medical encounter record (EMR). The EMR records and correlates significant medical data and video streams with an inferred higher-level event model of the surgery. Information from sensors such as Radio Frequency Identification (RFID) tags provides basic context information including the presence of medical staff, devices, instruments and medication in the operating room (OR). Patient monitoring systems and sensors such as pulse oximeters and anesthesia machines provide continuous streams of physiological data. These low level data streams are processed to generate higher-level primitive events, such as a nurse entering the OR. A hierarchical knowledge-based event detection system correlates primitive events, patient data and workflow data to infer high-level events, such as the onset of anesthesia. The resulting EMR provides medical staff with a permanent record of the surgery that can be used for subsequent evaluation and training. The system can also be used to detect potentially significant errors. It seeks to automate some of the tasks done by nursing staff today that detracts from their ability to attend to the patient.
117 citations
TL;DR: This paper describes an approach to estimate the activity being performed by hospital workers, based on information gathered from a workplace study conducted in a hospital, and indicates that the user activity can be correctly estimated 75% of the time which is good enough for several applications.
Abstract: Hospitals are convenient settings for the deployment of context-aware applications. The information needs of hospital workers are highly dependent on contextual variables, such as location, role and activity. While some of these parameters can be easily determined, others, such as activity are much more complex to estimate. This paper describes an approach to estimate the activity being performed by hospital workers. The approach is based on information gathered from a workplace study conducted in a hospital, in which 196 h of detailed observation of hospital workers was recorded. Contextual information, such as the location of hospital workers, artifacts being used, the people with whom they collaborate and the time of the day, is used to train a back propagation neural network to estimate hospital workers activities. The activities estimated include clinical case assessment, patient care, preparation, information management, coordination and classes and certification. The results indicate that the user activity can be correctly estimated 75% of the time (on average) which is good enough for several applications. We discuss how these results can be used in the design of activity-aware applications, arguing that recent advances in pervasive and networking technologies hold great promises for the deployment of such applications.
81 citations
TL;DR: An upper bound of EOT and its concavity is identified, which indicates that even if the candidate coordination delay were negligible, the throughput gain would become marginal when the number of forwarding candidates increases, and a local metric named expected one-hop throughput (EOT) is proposed to balance the benefit and cost.
Abstract: Geographic opportunistic routing (GOR) has shown throughput efficiency in coping with unreliable transmissions in multihop wireless networks. The basic idea behind opportunistic routing is to take advantage of the broadcast nature and spacial diversity of the wireless medium by involving multiple neighbors of the sender into the local forwarding, thus improve transmission reliability. The existing GOR schemes typically involve as many as available next-hop neighbors into the local forwarding, and give the nodes closer to the destination higher relay priorities. In this paper, we show that it is not always the optimal way to achieve the best throughput. We introduce a framework to analyze the one-hop throughput of GOR, provide a deeper insight into the trade-off between the benefit (packet advancement and transmission reliability) and cost (medium time delay) associated with the node collaboration, and propose a local metric named expected one-hop throughput (EOT) to balance the benefit and cost. We also identify an upper bound of EOT and its concavity, which indicates that even if the candidate coordination delay were negligible, the throughput gain would become marginal when the number of forwarding candidates increases. Based on the EOT, we also propose a local candidate selection and prioritization algorithm. Simulation results validate our analysis and show that the EOT metric leads to both better one-hop and path throughput than the corresponding pure GOR and geographic routing.
71 citations
TL;DR: In this paper, the authors investigated the power saving mechanism of Universal Mobile Telecommunications System (UMTS) and proposed an adaptive algorithm called dynamic discontinuous reception (DDRX) to enhance the performance of UMTS DRX.
Abstract: This paper investigates the power saving mechanism of Universal Mobile Telecommunications System (UMTS). UMTS discontinuous reception (DRX) is exercised between the network and a mobile station (MS) to save the power of the MS. The DRX mechanism is controlled by two parameters: the inactivity timer threshold tI and the DRX cycle tD. Analytic analysis and simulation model are proposed to study the optimal tI and tD selections that maximize the MS power saving under the given mean packet waiting time constraint. We also devise an adaptive algorithm called dynamic DRX (DDRX). This algorithm dynamically adjusts the tI and tD values to enhance the performance of UMTS DRX. Our study quantitatively shows how to select the best inactivity timer and DRX cycle values for various traffic patterns. We also show that DDRX nicely captures the user traffic patterns, and always adjusts the tI and tD close to the optimal values.
64 citations
TL;DR: QUORUM integrates a novel end-to-end packet delay estimation mechanism with stability-aware routing policies, allowing it to more accurately follow QoS requirements while minimizing misbehavior of selfish nodes.
Abstract: Wireless mesh networks (WMNs) can provide seamless broadband connectivity to network users with low setup and maintenance costs. To support next-generation applications with real-time requirements, however, these networks must provide improved quality of service guarantees. Current mesh protocols use techniques that fail to accurately predict the performance of end-to-end paths, and do not optimize performance based on knowledge of mesh network structures. In this paper, we propose QUORUM, a routing protocol optimized for WMNs that provides accurate QoS properties by correctly predicting delay and loss characteristics of data traffic. QUORUM integrates a novel end-to-end packet delay estimation mechanism with stability-aware routing policies, allowing it to more accurately follow QoS requirements while minimizing misbehavior of selfish nodes.
49 citations
TL;DR: A novel privacy enhanced anonymous authentication and access control scheme to secure the interactions between mobile users and services in PCEs with optional context authentication capability and provides explicit mutual authentication and allows multiple current sessions between a user and a service, while allowing the user to anonymously interact with the service.
Abstract: In pervasive computing environments (PCEs), privacy and security are two important but contradictory objectives. Users enjoy services provided in PCEs only after their privacy issues being sufficiently addressed. That is, users could not be tracked down for wherever they are and whatever they are doing. However, service providers always want to authenticate the users and make sure they are accessing only authorized services in a legitimate way. In PCEs, such user authentication may include context authentication in addition to the entity authentication. In this paper, we propose a novel privacy enhanced anonymous authentication and access control scheme to secure the interactions between mobile users and services in PCEs with optional context authentication capability. The proposed scheme seamlessly integrates two underlying cryptographic primitives, blind signature and hash chain, into a highly flexible and lightweight authentication and key establishment protocol. It provides explicit mutual authentication and allows multiple current sessions between a user and a service, while allowing the user to anonymously interact with the service. The proposed scheme is also designed to be DoS resilient by requiring the user to prove her legitimacy when initializing a service session.
40 citations
TL;DR: A low-cost and easy-to-deploy wireless telemedicine system that can assist on-site patient care during disasters by facilitating real-time transfer of multimedia data from video cameras, sensors, medical images and text from multiple disaster sites to the control center of the disaster area.
Abstract: In this paper, we introduce a low-cost and easy-to-deploy wireless telemedicine system, denoted WISTA, that can assist on-site patient care during disasters. The proposed system facilitates real-time transfer of multimedia data from video cameras, sensors, medical images and text from multiple disaster sites to the control center of the disaster area. WISTA enables disaster managers to obtain patients' status information in real-time from the entire disaster site, which can assist the timely diagnosis as well as the treatment of patients. Moreover, the disaster managers in the control center can remotely control the information sent from the individual disaster sites. The proposed system uses a hierarchical architecture which allows scalable implementation. For dense disaster areas, a layered structure is applied to support information dissemination from s large number of patients. We have implemented the system prototype over a wireless channel and successfully demonstrated simultaneous transmission of video, sensor information, medical images and text from multiple sites to the control center. In addition, the scalability of the system is evaluated using OPNET simulation. Both experiments validate our system design.
34 citations
TL;DR: Through a performance study, the proposed channel assignment protocol can substantially increase throughput and reduce delay in wireless ad hoc networks, compared to the IEEE 802.11 MAC protocol and an existing multi-channel scheme.
Abstract: To improve the capacity of wireless ad hoc networks by exploiting multiple available channels, we propose a distributed channel assignment protocol that is based on a cross-layer approach. By combining channel assignment with routing protocols, the proposed channel assignment protocol is shown to require fewer channels and exhibit lower communication, computation, and storage complexity than existing channel assignment schemes. A multi-channel MAC (MC-MAC) protocol that works with the proposed channel assignment protocol is also presented. We prove the correctness of the proposed channel assignment protocol. In addition, through a performance study, we show that the proposed protocol can substantially increase throughput and reduce delay in wireless ad hoc networks, compared to the IEEE 802.11 MAC protocol and an existing multi-channel scheme.
TL;DR: A high-speed public-key cryptoprocessor that exploits three-level parallelism in Elliptic Curve Cryptography (ECC) over GF(2n) to perform over 80,000 scalar multiplications per second and to enhance security in wireless mobile applications is presented.
Abstract: We present a high-speed public-key cryptoprocessor that exploits three-level parallelism in Elliptic Curve Cryptography (ECC) over GF(2n). The proposed cryptoprocessor employs a Parallelized Modular Arithmetic Logic Unit (P-MALU) that exploits two types of different parallelism for accelerating modular operations. The sequence of scalar multiplications is also accelerated by exploiting Instruction-Level Parallelism (ILP) and processing multiple P-MALU instructions in parallel. The system is programmable and hence independent of the type of the elliptic curves and scalar multiplication algorithms. The synthesis results show that scalar multiplication of ECC over GF(2163) on a generic curve can be computed in 20 and 16 µs respectively for the binary NAF (Non-Adjacent Form) and the Montgomery method. The performance can be accelerated furthermore on a Koblitz curve and reach scalar multiplication of 12 µs with the TNAF (τ-adic NAF) method. This fast performance allows us to perform over 80,000 scalar multiplications per second and to enhance security in wireless mobile applications.
TL;DR: DS-EDCA outperforms the original EDCA in terms of its support for both strict priority and weighted fair service and can be easily implemented, and is compatible to the IEEE 802.11 Standard.
Abstract: In this paper, we propose a new differentiated service model, referred to as Differentiated Service-EDCA (DS-EDCA), for the Enhanced Distributed Channel Access (EDCA) of IEEE 802.11e wireless local area networks (WLANs). With DS-EDCA, both strict priority and weighted fair service can be provided. The strict priority service is provided for high priority traffic through carefully setting the EDCA parameter sets of lower priority traffic; the proportional fairness service is enabled by determining the backoff intervals according to the distributed scheduling discipline (DFS). We also propose a hierarchical link sharing model for IEEE 802.11e WLANs, in which AP and mobile stations are allocated different amounts of link resource. The performance of DS-EDCA and EDCA is compared via ns-2 simulations. The results show that DS-EDCA outperforms the original EDCA in terms of its support for both strict priority and weighted fair service. More importantly, DS-EDCA can be easily implemented, and is compatible to the IEEE 802.11 Standard.
TL;DR: A quality of protection (QoP) model is introduced to indicate the benefits and the performance cost of security protocols in terms of authentication time, cryptographic overhead and throughput and it is found that some protocols are robust against mobility with little variation in system performance; thus, it is possible to provision steady service by choosing security protocols when users' mobility pattern is unknown.
Abstract: Wireless local area networks (LANs) are vulnerable to malicious attacks due to their shared medium in unlicensed frequency spectrum, thus requiring security features for a variety of applications even at the cost of quality of service (QoS). However, there is very little work on investigating to what extent system performance is affected by security configurations with respect to mobility scenarios, heterogeneous networks, and different applications. In order to exploit the full potential of existing security solutions, we present a detailed experimental study to demonstrate the impacts of security features on performance by integrating cross-layer security protocols in a wireless LAN testbed with IP mobility. We introduce a quality of protection (QoP) model to indicate the benefits of security protocols and then measure the performance cost of security protocols in terms of authentication time, cryptographic overhead and throughput. Our measurements demonstrate that the effects of security protocols on QoS parameters span a wide range; for example, authentication time is between 0.11 and 6.28 s, which can potentially affect packet loss dramatically. We also find that for the same security protocol throughput in nonroaming scenarios can be up to two times higher than that in roaming scenarios. However, some protocols are robust against mobility with little variation in system performance; thus, it is possible to provision steady service by choosing security protocols when users' mobility pattern is unknown. Furthermore, we provide observations on cross-layer security protocols and suggestions to the design of future security protocols for real-time services in wireless LANs.
TL;DR: The authors' CAPM scheme has an adaptive on period feature that allows it to achieve high delivery ratio and low delivery latency when used with Prophet, a recently proposed DTN routing scheme, which is very promising in providing energy saving without degrading much the data delivery performance.
Abstract: Disruption tolerant network (DTN) is characterized by frequent partitions and intermittent connectivity. Power management issue in such networks is challenging. Existing power management schemes for wireless networks cannot be directly applied to DTNs because they assume the networks are well-connected. Since the network connectivity opportunities are rare, any power management scheme deployed in DTNs should not worsen the existing network connectivity. In this paper, we design a power management scheme called context-aware power management scheme (CAPM) for DTNs. Our CAPM scheme has an adaptive on period feature that allows it to achieve high delivery ratio and low delivery latency when used with Prophet, a recently proposed DTN routing scheme. Via simulations, we evaluate the performance of the CAPM scheme when used with the Prophet routing scheme in different scenarios e.g. different traffic load, node speeds and sleep patterns. Our evaluation results indicate that the CAPM scheme is very promising in providing energy saving (as high as 80%) without degrading much the data delivery performance.
TL;DR: A new concept of channel allocation model for BWA system is proposed and the relations between the signal propagation and the distance is investigated as well as a signal-aware dynamic channel allocation (SDCA) scheme for dynamicChannel allocation (DCA) in BWA networks (BWANs).
Abstract: The radio spectrum of IEEE 802.16 medium access control (MAC) protocol ranges from 2-66 GHz, which is one of potential solutions for broadband wireless access (BWA) or beyond third generation (B3G)/ 4G networks. The maximum transmission range can reach about 48 km. However, with the property of radio propagation, the maximum transmission distance is proportioned inversely to the frequency the mobile subscriber station (MSS) carries. According to this property, the channel allocation can be based on how far the distance between the MSS and the base station (BS) in a macrocell. Therefore, this paper first proposes a new concept of channel allocation model for BWA system and investigates the relations between the signal propagation and the distance as well as propose a signal-aware dynamic channel allocation (SDCA) scheme for dynamic channel allocation (DCA) in BWA networks (BWANs). The SDCA enables the BS to allocate appropriate channels to MSSs according to the received signal-to-noise ratio (SNR) value from the MSSs. Besides, according to the frequency, the SDCA can estimate a minimum power for MSS to communicate. The SDCA not only increases the capacity of the system but saves the overall power consumption of the system well. We also present a new out-of-service prevention scheme for supporting mobility in the system. Simulation results show that the proposed SDCA can achieve the channel utilization (throughput) by up to 94.4% when the spectrum ranges from 2-11 GHz.
TL;DR: The work at hand presents the firstHardware implementation of a frequency domain multiplier suitable for ECC and the first hardware implementation of ECC in the frequency domain.
Abstract: We propose a novel area/time efficient elliptic curve cryptography (ECC) processor architecture which performs all finite field arithmetic operations in the discrete Fourier domain. The proposed architecture utilizes a class of optimal extension fields (OEF) GF(qm) where the field characteristic is a Mersenne prime q = 2n - 1 and m = n. The main advantage of our architecture is that it achieves extension field modular multiplication in the discrete Fourier domain with only a linear number of base field GF(q) multiplications in addition to a quadratic number of simpler operations such as addition and bitwise rotation. We achieve an area between 25k and 50k equivalent gates for the implementations over OEFs of size 169, 289 and 361 bits. With its low area and high speed, the proposed architecture is well suited for ECC in small device environments such as sensor networks. The work at hand presents the first hardware implementation of a frequency domain multiplier suitable for ECC and the first hardware implementation of ECC in the frequency domain.
TL;DR: An analytical model is proposed to determine the associate cost for the signaling and data traffic for inter-system communication in these architectures and it includes the transmission, processing, and queueing costs at various entities.
Abstract: The future fourth generation wireless heterogeneous networks aim to integrate various wireless access technologies and to support the IMS (IP multi-media subsystem) sessions. In this paper, we propose the Loosely Coupled Satellite-Cellular-WiMAX-WLAN (LCSCW2) and the Tightly Coupled Satellite-Cellular-WiMAX-WLAN (TCSCW2) interworking architectures. The LCSCW2 and TCSCW2 architectures use the loosely coupling and tightly coupling approach, respectively. Both of them integrate the satellite networks, third generation (3G) wireless networks, worldwide interoperability for microwave access (WiMAX), and wireless local area networks (WLANs). They can support IMS sessions and provide global coverage. The LCSCW2 architecture facilitates independent deployment and traffic engineering of various access networks. The TCSCW2 architecture can provide quality of service (QoS) guarantee. We also propose an analytical model to determine the associate cost for the signaling and data traffic for inter-system communication in these architectures. The cost analysis includes the transmission, processing, and queueing costs at various entities. Numerical results are presented for different arrival rates and session lengths.
TL;DR: A packet-level UWB channel model considering the shadowing processes based on a Finite-state Markov Chain is built that can be incorporated into existing network simulators and used to facilitate protocol design and quality of service analysis for UWB based wireless personal area networks.
Abstract: For an indoor ultra-wideband (UWB) communication system, the line-of-sight (LOS) between the transmitter and receiver may be frequently blocked by moving people. Blocking of LOS may significantly affect the quality of service of on-going UWB communications. Based on the Angular Power Spectrum Density and the human blocking models, we build a packet-level UWB channel model considering the shadowing processes based on a Finite-state Markov Chain. The model is simple enough to be incorporated into existing network simulators like NS-2 and it can be used to facilitate protocol design and quality of service analysis for UWB based wireless personal area networks.
TL;DR: An algorithm called interference-aware adaptive frequency hopping (IAFH) is presented and implemented on Bluetooth devices to mitigate the interference between IEEE 802.11b and Bluetooth wireless networks.
Abstract: IEEE 802.11b wireless networks and Bluetooth networks provide complimentary services using the same unlicensed radio frequency band. As the benefits of utilizing these services become increasingly apparent, the likelihood of mutual interference also increases. The well-known frequency hopping algorithm and adaptive frequency hopping algorithm do not fully consider the interference level of the operating environment. In this paper an algorithm called interference-aware adaptive frequency hopping (IAFH) is presented and implemented on Bluetooth devices to mitigate the interference between IEEE 802.11b and Bluetooth wireless networks. An analytical model of IAFH is developed to evaluate the performance of 802.11b stations and Bluetooth devices in a mutual interference environment. The analysis comprises the collision probability, packet error rate, and throughput performance for both IEEE 802.11b and Bluetooth wireless networks. Simulation results confirm that 802.11b station and IAFH-enabled Bluetooth devices experience lower packet error rates and better throughput as compared to the frequency hopping and adaptive frequency hopping algorithms.
TL;DR: This paper presents and analyzes detection methods purely based on geometric constraints in sensor networks that can protect the localization algorithm from malicious attacks by detecting and eliminating the negative impact of fake information.
Abstract: In wireless sensor networks, sensors should have some mechanisms to learn their locations since sensed data without associated location information may be meaningless. While many sensor localization algorithms have been proposed, security issues in sensor localization are usually not addressed in their original design. Secure sensor localization is very challenging due to limited computation and energy resources in sensors. It is highly desirable that a localization scheme is robust and is able to detect malicious attacks without using complex cryptographic operations. In this paper, we present and analyze detection methods purely based on geometric constraints in sensor networks. Our detection methods can protect the localization algorithm from malicious attacks by detecting and eliminating the negative impact of fake information.
TL;DR: It is proved that for a two-tier wireless network architecture, the optimal policy has a two -dimensional threshold structure and this structural result is used to design two computationally efficient algorithms, Structured Value Iteration and Structured Update value Iteration, which can be used to determine the optimalpolicy in terms of thresholds.
Abstract: In the near future, demand for heterogeneous wireless networking (HWN) is expected to increase. QoS provisioning in these networks is a challenging issue considering the diversity in wireless networking technologies and the existence of mobile users with different communication requirements. In HWNs with their increased complexity, "the curse of dimensionality" problem makes it impractical to directly apply the decision theoretic optimal control methods that are previously used in homogeneous wireless networks to achieve desired QoS levels. In this paper, optimal call admission control policies for HWNs are considered. A decision theoretic framework for the problem is derived by a dynamic programming formulation. We prove that for a two-tier wireless network architecture, the optimal policy has a two-dimensional threshold structure. Further, this structural result is used to design two computationally efficient algorithms, Structured Value Iteration and StructuredUpdate Value Iteration. These algorithms can be used to determine the optimal policy in terms of thresholds. Although the first one is closer in its operation to the conventional Value Iteration algorithm, the second one has a significantly lower complexity. Extensive numerical observations suggest that, for all practical parameter sets, the algorithms always converge to the overall optimal policy. Further, the numerical results show that the proposed algorithms are efficient in terms of time-complexity and in achieving the optimal performance.
TL;DR: A new distributed wakeup schedule is introduced in the context of topology control which aims to conserve more energy while not compromising on the delay performance of the system and addresses the problem of increasing the network longevity for a given upper bound on the average end-to-end delay.
Abstract: Wakeup scheduling in wireless sensor networks is known as the most effective way to conserve the limited amount of available energy for each sensor node. Such schedules are applicable to protocols of different network layers and often result in higher latency. Tolerance to latency varies greatly depending on the application so that it is low for a large class of delay sensitive applications. In this paper, we present a unified approach in the design of wakeup schedules in different network layers. A new distributed wakeup schedule is introduced in the context of topology control which aims to conserve more energy while not compromising on the delay performance of the system. The proposed protocol addresses the problem of increasing the network longevity for a given upper bound on the average end-to-end delay. In this scheme neither localization nor synchronization is required and only local information about the network topology is used. In addition to its simplicity of implementation, its energy overhead is negligible and it implicitly determines the routing paths. Our simulation results show that the performance of this protocol is close to the optimal schedule and significantly higher than SPAN, an existing topology control mechanism.
TL;DR: This paper investigates the queuing behavior of self-similar traffic flows for data applications in a packet-switching single-server wireless network, and investigates the multiplexing of heavy-tailed traffic flows with a finite buffer for the downlink transmission of a wireless network.
Abstract: Recent research based on traffic measurements shows that Internet traffic flows have a fractal nature (i.e., self-similarity property), which causes an underestimation of network engineering parameters when using the conventional Poisson model. Preliminary field measurements demonstrate that packet data traffic in wireless communications also exhibits self-similarity. In this paper, we investigate the queuing behavior of self-similar traffic flows for data applications in a packet-switching single-server wireless network. The traffic is generated by an on-off source with heavy-tailed on periods and exponentially distributed off periods. We extend previous analysis of a relation among the asymptotic distribution of loss probability, traffic specifications, and transmission rate for a wireline system to a wireless system, taking into account wireless propagation channel characteristics. We also investigate the multiplexing of heavy-tailed traffic flows with a finite buffer for the downlink transmission of a wireless network. Computer simulation results demonstrate that assumptions made in the theoretical analysis are reasonable and the derived relationships are accurate.
TL;DR: An improved Montgomery multiplier, based on modified four-to-two carry-save adders (CSAs) to reduce critical path delay, is presented and a new bit-sliced, unified and scalable Montgomery multiplier architecture, applicable for both RSA and ECC, is proposed.
Abstract: In this paper an improved Montgomery multiplier, based on modified four-to-two carry-save adders (CSAs) to reduce critical path delay, is presented Instead of implementing four-to-two CSA using two levels of carry-save logic, authors propose a modified four-to-two CSA using only one level of carry-save logic taking advantage of pre-computed input values Also, a new bit-sliced, unified and scalable Montgomery multiplier architecture, applicable for both RSA and ECC (Elliptic Curve Cryptography), is proposed In the existing word-based scalable multiplier architectures, some processing elements (PEs) do not perform useful computation during the last pipeline cycle when the precision is not equal to an exact multiple of the word size, like in ECC This intrinsic limitation requires a few extra clock cycles to operate on operand lengths which are not powers of 2 The proposed architecture eliminates the need for extra clock cycles by reconfiguring the design at bit-level and hence can operate on any operand length, limited only by memory and control constraints It requires 2∼15% fewer clock cycles than the existing architectures for key lengths of interest in RSA and 11∼18% for binary fields and 10∼14% for prime fields in case of ECC An FPGA implementation of the proposed architecture shows that it can perform 1,024-bit modular exponentiation in about 15 ms which is better than that by the existing multiplier architectures
TL;DR: This paper presents several mobile traversal algorithms (MTA) based on triangulation coverage that employs N ≥ 3 MSNs such that, up to N−3 node failures can be tolerated and the bounds on the total traveling distance and time are derived and the tightness of the bounds are proven through simulations.
Abstract: In harsh outdoor terrains like disaster areas and urban toxic regions, optimal placements of static sensor nodes might not be possible, leading to possible incomplete coverage of the region. In such situations, mobile sensor nodes (MSNs) might be a better option and a significantly fewer number of nodes are required than their static counterparts. A triangulation-based coverage where, groups of three MSNs position themselves to form equilateral triangles, has several applications in localization, 3D imaging and coordinated search operation. In this paper, we present several mobile traversal algorithms (MTA) based on triangulation coverage that employs N ≥ 3 MSNs such that, up to N - 3 node failures can be tolerated. MTA achieves three objectives: (a) as N increases, the total time to cover the field decreases in the absence of a failure; (b) each MSN travels a minimum distance; (c) upon a failure, the remaining MSNs efficiently complete the coverage of the field. The bounds on the total traveling distance and time are derived and the tightness of the bounds are proven through simulations. Furthermore, we also derive the bounds on the distance traveled by an MSN to complete the coverage process. The bounds on the individual traveling distances are useful in minimizing and bounding the energy consumption of the MSNs.
TL;DR: This special issue aims to present recent advances in cryptographic hardware architectures for secure mobile computing, and illustrates the possibilities of using ECC to provide strong security for mobile computing applications.
Abstract: Security is of paramount importance to the design of modern communication systems and in particular, to wireless networks. Wireless devices are becoming commonplace in both the office and home environment and therefore, the need for strong secure transport protocols is one of the most important issues in mobile standards. Cryptography is the foremost method for providing communication security and is a mathematically intensive process which, to date, has mainly been implemented in software. However, such methods are slow and cannot cope with the demands of rapidly growing real-time wireless communication systems. Encryption of digital information in real-time holds the key to the successful growth of applications such as wireless hand-held devices and high performance mobile communications. The innovative mapping of complex cryptographic operations onto hardware architectures with consideration for throughput, area and power issues has emerged as a viable solution. This special issue aims to present recent advances in cryptographic hardware architectures for secure mobile computing. The majority of the accepted papers focus on the challenge of designing high-speed asymmetric cryptographic hardware architectures for mobile applications. Asymmetric techniques are, in general, more complex than symmetric cryptographic methods and as such, it is inevitably more difficult to design efficient low resource, high-speed asymmetric architectures. The most common and best known asymmetric scheme is the RSA algorithm, but hardware implementations of RSA can require tens of thousands of gates. A much more promising asymmetric security solution is elliptic curve cryptography (ECC). ECC is viewed as a low-cost alternative to RSA and provides similar security strengths using much shorter key lengths. The research described in the contributions to this special issue illustrate the possibilities of using ECC to provide strong security for mobile computing applications. The first paper, ‘A Survey of Cryptographic Primitives and Implementations for Hardware-Constrained Sensor Network Nodes’, by Roman, Alcaraz and Lopez surveys existing research into hardware and software cryptographic implementations for wireless sensor networks. They conclude that while existing sensor nodes can support software security implementations, next generation sensor nodes will be able to support hardware security architectures of more complex asymmetric cryptographic algorithms. The next three papers describe high-speed ECC processor architectures. Sakiyama, Batina, Preneel and Verbauwhede’s paper, ‘High-Performance Public-Key Cryptoprocessor for Wireless Mobile Applications’, presents an ECC processor hardware architecture that exploits parallel processing of the modular operations in the arithmetic logic unit, in addition to instruction-level parallelism to achieve a high overall Mobile Netw Appl (2007) 12:229–230 DOI 10.1007/s11036-007-0023-3
TL;DR: A technique is presented to construct multi-hop clusters with balanced sizes, based on the neighborhood benchmark (NB) to quantify the connectivity and link stability of mobile nodes.
Abstract: Large-scale mobile ad-hoc networks require flexible and stable clustered network structure for efficient data collection and dissemination. In this paper, a technique is presented to construct multi-hop clusters with balanced sizes, based on the neighborhood benchmark (NB) to quantify the connectivity and link stability of mobile nodes. By exploiting autonomous clusterhead selection and a specialized handshake process with the clusterheads, the nodes with highest NB scores are selected as clusterheads and all the clusters constructed are connected. The deviation of cluster sizes is kept small using a partial probability-based approach. Our technique generates highly stable multi-hop clusters with low overhead, and provides the flexibility of controlling the cluster radius adaptively for various network applications.
TL;DR: A novel sharing scheme is proposed to significantly reduce the number of field multiplications and the usage of lookup tables, providing high speed operations for both hardware and software realizations.
Abstract: Elliptic curve cryptography (ECC) is recognized as a fast cryptography system and has many applications in security systems. In this paper, a novel sharing scheme is proposed to significantly reduce the number of field multiplications and the usage of lookup tables, providing high speed operations for both hard-ware and software realizations.