40,347 research outputs found
Wireless sensor network for health monitoring
Wireless Sensor Network (WSN) is becoming a significant enabling technology for a wide variety of applications. Recent advances in WSN have facilitated the realization of pervasive health monitoring for both homecare and hospital environments. Current technological advances in sensors, power-efficient integrated circuits, and wireless communication have allowed the development of miniature, lightweight, low-cost, and smart physiological sensor nodes. These nodes are capable of sensing, processing, and communicating one or more vital signs. Furthermore, they can be used in wireless personal area networks (WPANs) or wireless body sensor networks (WBSNs) for health monitoring. Many studies were performed and/or are under way in order to develop flexible, reliable, secure, real-time, and power-efficient WBSNs suitable for healthcare applications. To efficiently control and monitor a patient’s status as well as to reduce the cost of power and maintenance, IEEE 802.15.4/ZigBee, a communication standard for low-power wireless communication, is developed as a new efficient technology in health monitoring systems. The main contribution of this dissertation is to provide a modeling, analysis, and design framework for WSN health monitoring systems. This dissertation describes the applications of wireless sensor networks in the healthcare area and discusses the related issues and challenges. The main goal of this study is to evaluate the acceptance of the current wireless standard for enabling WSNs for healthcare monitoring in real environment. Its focus is on IEEE 802.15.4/ZigBee protocols combined with hardware and software platforms. Especially, it focuses on Carrier Sense Multiple Access with Collision Avoidance mechanism (CSMA/CA) algorithms for reliable communication in multiple accessing networks. The performance analysis metrics are established through measured data and mathematical analysis.
This dissertation evaluates the network performance of the IEEE 802.15.4 unslotted CSMA/CA mechanism for different parameter settings through analytical modeling and simulation. For this protocol, a Markov chain model is used to derive the analytical expression of normalized packet transmission, reliability, channel access delay, and energy consumption. This model is used to describe the stochastic behavior of random access and deterministic behavior of IEEE 802.15.4 CSMA/CA. By using it, the different aspects of health monitoring can be analyzed. The sound transmission of heart beat with other smaller data packet transmission is studied. The obtained theoretical analysis and simulation results can be used to estimate and design the high performance health monitoring systems
Energy-Efficient Resource Allocation in Wireless Networks: An Overview of Game-Theoretic Approaches
An overview of game-theoretic approaches to energy-efficient resource
allocation in wireless networks is presented. Focusing on multiple-access
networks, it is demonstrated that game theory can be used as an effective tool
to study resource allocation in wireless networks with quality-of-service (QoS)
constraints. A family of non-cooperative (distributed) games is presented in
which each user seeks to choose a strategy that maximizes its own utility while
satisfying its QoS requirements. The utility function considered here measures
the number of reliable bits that are transmitted per joule of energy consumed
and, hence, is particulary suitable for energy-constrained networks. The
actions available to each user in trying to maximize its own utility are at
least the choice of the transmit power and, depending on the situation, the
user may also be able to choose its transmission rate, modulation, packet size,
multiuser receiver, multi-antenna processing algorithm, or carrier allocation
strategy. The best-response strategy and Nash equilibrium for each game is
presented. Using this game-theoretic framework, the effects of power control,
rate control, modulation, temporal and spatial signal processing, carrier
allocation strategy and delay QoS constraints on energy efficiency and network
capacity are quantified.Comment: To appear in the IEEE Signal Processing Magazine: Special Issue on
Resource-Constrained Signal Processing, Communications and Networking, May
200
Energy-efficient wireless communication
In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters
Flow Allocation for Maximum Throughput and Bounded Delay on Multiple Disjoint Paths for Random Access Wireless Multihop Networks
In this paper, we consider random access, wireless, multi-hop networks, with
multi-packet reception capabilities, where multiple flows are forwarded to the
gateways through node disjoint paths. We explore the issue of allocating flow
on multiple paths, exhibiting both intra- and inter-path interference, in order
to maximize average aggregate flow throughput (AAT) and also provide bounded
packet delay. A distributed flow allocation scheme is proposed where allocation
of flow on paths is formulated as an optimization problem. Through an
illustrative topology it is shown that the corresponding problem is non-convex.
Furthermore, a simple, but accurate model is employed for the average aggregate
throughput achieved by all flows, that captures both intra- and inter-path
interference through the SINR model. The proposed scheme is evaluated through
Ns2 simulations of several random wireless scenarios. Simulation results reveal
that, the model employed, accurately captures the AAT observed in the simulated
scenarios, even when the assumption of saturated queues is removed. Simulation
results also show that the proposed scheme achieves significantly higher AAT,
for the vast majority of the wireless scenarios explored, than the following
flow allocation schemes: one that assigns flows on paths on a round-robin
fashion, one that optimally utilizes the best path only, and another one that
assigns the maximum possible flow on each path. Finally, a variant of the
proposed scheme is explored, where interference for each link is approximated
by considering its dominant interfering nodes only.Comment: IEEE Transactions on Vehicular Technolog
Applications of Repeated Games in Wireless Networks: A Survey
A repeated game is an effective tool to model interactions and conflicts for
players aiming to achieve their objectives in a long-term basis. Contrary to
static noncooperative games that model an interaction among players in only one
period, in repeated games, interactions of players repeat for multiple periods;
and thus the players become aware of other players' past behaviors and their
future benefits, and will adapt their behavior accordingly. In wireless
networks, conflicts among wireless nodes can lead to selfish behaviors,
resulting in poor network performances and detrimental individual payoffs. In
this paper, we survey the applications of repeated games in different wireless
networks. The main goal is to demonstrate the use of repeated games to
encourage wireless nodes to cooperate, thereby improving network performances
and avoiding network disruption due to selfish behaviors. Furthermore, various
problems in wireless networks and variations of repeated game models together
with the corresponding solutions are discussed in this survey. Finally, we
outline some open issues and future research directions.Comment: 32 pages, 15 figures, 5 tables, 168 reference
Reducing false wake-up in contention-based wake-up control of wireless LANs
This paper studies the potential problem and performance when tightly integrating a low power wake-up radio (WuR) and a power-hungry wireless LAN (WLAN) module for energy efficient channel access. In this model, a WuR monitors the channel, performs carrier sense, and activates its co-located WLAN module when the channel becomes ready for transmission. Different from previous methods, the node that will be activated is not decided in advance, but decided by distributed contention. Because of the wake-up latency of WLAN modules, multiple nodes may be falsely activated, except the node that will actually transmit. This is called a false wake-up problem and it is solved from three aspects in this work: (i) resetting backoff counter of each node in a way as if it is frozen in a wake-up period, (ii) reducing false wake-up time by immediately putting a WLAN module into sleep once a false wake-up is inferred, and (iii) reducing false wake-up probability by adjusting contention window. Analysis shows that false wake-ups, instead of collisions, become the dominant energy overhead. Extensive simulations confirm that the proposed method (WuR-ESOC) effectively reduces energy overhead, by up to 60% compared with state-of-the-arts, achieving a better tradeoff between throughput and energy consumption
- …