A Survey of System Architecture Requirements for Health Care-Based Wireless Sensor Networks
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paper_title: Sensor networks for medical care

paper_content:

Sensor networks have the potential to greatly impact many aspects of medical care. By outfitting patients with wireless, wearable vital sign sensors, collecting detailed real-time data on physiological status can be greatly simplified. However, there is a significant gap between existing sensor network systems and the needs of medical care. In particular, medical sensor networks must support multicast routing topologies, node mobility, a wide range of data rates and high degrees of reliability, and security. This paper describes our experiences with developing a combined hardware and software platform for medical sensor networks, called CodeBlue. CodeBlue provides protocols for device discovery and publish/subscribe multihop routing, as well as a simple query interface that is tailored for medical monitoring. We have developed several medical sensors based on the popular MicaZ and Telos mote designs, including a pulse oximeter, EKG and motion-activity sensor. We also describe a new, miniaturized sensor mote designed for medical use. We present initial results for the CodeBlue prototype demonstrating the integration of our medical sensors with the publish/subscribe routing substrate. We have experimentally validated the prototype on our 30-node sensor network testbed, demonstrating its scalability and robustness as the number of simultaneous queries, data rates, and transmitting sensors are varied. We also study the effect of node mobility, fairness across multiple simultaneous paths, and patterns of packet loss, confirming the system’s ability to maintain stable routes despite variations in node location and
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paper_title: Robust medical ad hoc sensor networks (MASN) with wavelet-based ECG data mining

paper_content:

Heart disease is the top elder killer in the world. To reduce the healthcare cost, it is a necessary tendency to deploy self-organized, wireless heart disease monitoring hardware/software systems. Telemedicine platform based on ad hoc interconnection of tiny ECG sensors, called medical ad hoc sensor networks (MASN), can provide a promising approach for performing low-cost, real-time, remote cardiac patient monitoring at any time. The contribution of this research is the design of a practical MASN hardware/software platform to perform real-time healthcare data collections. It has reliable, cluster-based communication scheme. Due to the radio broadcasting nature of wireless networks, a MASN has the risk of being attacked. This research also designs a low overhead medical security scheme to achieve confidential ECG data transmission in the wireless medium. Finally, our MASN system has the capability of keeping track of cardiac patients and extracting ECG features based on wavelet theories. Our MASN platform is very useful to practical medical monitoring applications.
---
paper_title: Sensor networks for medical care

paper_content:

Sensor networks have the potential to greatly impact many aspects of medical care. By outfitting patients with wireless, wearable vital sign sensors, collecting detailed real-time data on physiological status can be greatly simplified. However, there is a significant gap between existing sensor network systems and the needs of medical care. In particular, medical sensor networks must support multicast routing topologies, node mobility, a wide range of data rates and high degrees of reliability, and security. This paper describes our experiences with developing a combined hardware and software platform for medical sensor networks, called CodeBlue. CodeBlue provides protocols for device discovery and publish/subscribe multihop routing, as well as a simple query interface that is tailored for medical monitoring. We have developed several medical sensors based on the popular MicaZ and Telos mote designs, including a pulse oximeter, EKG and motion-activity sensor. We also describe a new, miniaturized sensor mote designed for medical use. We present initial results for the CodeBlue prototype demonstrating the integration of our medical sensors with the publish/subscribe routing substrate. We have experimentally validated the prototype on our 30-node sensor network testbed, demonstrating its scalability and robustness as the number of simultaneous queries, data rates, and transmitting sensors are varied. We also study the effect of node mobility, fairness across multiple simultaneous paths, and patterns of packet loss, confirming the system’s ability to maintain stable routes despite variations in node location and
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paper_title: MEDiSN: Medical emergency detection in sensor networks

paper_content:

Staff shortages and an increasingly aging population are straining the ability of emergency departments to provide high quality care. At the same time, there is a growing concern about hospitals' ability to provide effective care during disaster events. For these reasons, tools that automate patient monitoring have the potential to greatly improve efficiency and quality of health care. Towards this goal, we have developed MEDiSN, a wireless sensor network for monitoring patients' physiological data in hospitals and during disaster events. MEDiSN comprises Physiological Monitors (PMs), which are custom-built, patient-worn motes that sample, encrypt, and sign physiological data and Relay Points (RPs) that self-organize into a multi-hop wireless backbone for carrying physiological data. Moreover, MEDiSN includes a back-end server that persistently stores medical data and presents them to authenticated GUI clients. The combination of MEDiSN's two-tier architecture and optimized rate control protocols allows it to address the compound challenge of reliably delivering large volumes of data while meeting the application's QoS requirements. Results from extensive simulations, testbed experiments, and multiple pilot hospital deployments show that MEDiSN can scale from tens to at least five hundred PMs, effectively protect application packets from congestive and corruptive losses, and deliver medically actionable data.
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paper_title: Medium access control with coordinated adaptive sleeping for wireless sensor networks

paper_content:

This paper proposes S-MAC, a medium access control (MAC) protocol designed for wireless sensor networks. Wireless sensor networks use battery-operated computing and sensing devices. A network of these devices will collaborate for a common application such as environmental monitoring. We expect sensor networks to be deployed in an ad hoc fashion, with nodes remaining largely inactive for long time, but becoming suddenly active when something is detected. These characteristics of sensor networks and applications motivate a MAC that is different from traditional wireless MACs such as IEEE 802.11 in several ways: energy conservation and self-configuration are primary goals, while per-node fairness and latency are less important. S-MAC uses a few novel techniques to reduce energy consumption and support self-configuration. It enables low-duty-cycle operation in a multihop network. Nodes form virtual clusters based on common sleep schedules to reduce control overhead and enable traffic-adaptive wake-up. S-MAC uses in-channel signaling to avoid overhearing unnecessary traffic. Finally, S-MAC applies message passing to reduce contention latency for applications that require in-network data processing. The paper presents measurement results of S-MAC performance on a sample sensor node, the UC Berkeley Mote, and reveals fundamental tradeoffs on energy, latency and throughput. Results show that S-MAC obtains significant energy savings compared with an 802.11-like MAC without sleeping.
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paper_title: Sensor networks for medical care

paper_content:

Sensor networks have the potential to greatly impact many aspects of medical care. By outfitting patients with wireless, wearable vital sign sensors, collecting detailed real-time data on physiological status can be greatly simplified. However, there is a significant gap between existing sensor network systems and the needs of medical care. In particular, medical sensor networks must support multicast routing topologies, node mobility, a wide range of data rates and high degrees of reliability, and security. This paper describes our experiences with developing a combined hardware and software platform for medical sensor networks, called CodeBlue. CodeBlue provides protocols for device discovery and publish/subscribe multihop routing, as well as a simple query interface that is tailored for medical monitoring. We have developed several medical sensors based on the popular MicaZ and Telos mote designs, including a pulse oximeter, EKG and motion-activity sensor. We also describe a new, miniaturized sensor mote designed for medical use. We present initial results for the CodeBlue prototype demonstrating the integration of our medical sensors with the publish/subscribe routing substrate. We have experimentally validated the prototype on our 30-node sensor network testbed, demonstrating its scalability and robustness as the number of simultaneous queries, data rates, and transmitting sensors are varied. We also study the effect of node mobility, fairness across multiple simultaneous paths, and patterns of packet loss, confirming the system’s ability to maintain stable routes despite variations in node location and
---
paper_title: MEDiSN: Medical emergency detection in sensor networks

paper_content:

Staff shortages and an increasingly aging population are straining the ability of emergency departments to provide high quality care. At the same time, there is a growing concern about hospitals' ability to provide effective care during disaster events. For these reasons, tools that automate patient monitoring have the potential to greatly improve efficiency and quality of health care. Towards this goal, we have developed MEDiSN, a wireless sensor network for monitoring patients' physiological data in hospitals and during disaster events. MEDiSN comprises Physiological Monitors (PMs), which are custom-built, patient-worn motes that sample, encrypt, and sign physiological data and Relay Points (RPs) that self-organize into a multi-hop wireless backbone for carrying physiological data. Moreover, MEDiSN includes a back-end server that persistently stores medical data and presents them to authenticated GUI clients. The combination of MEDiSN's two-tier architecture and optimized rate control protocols allows it to address the compound challenge of reliably delivering large volumes of data while meeting the application's QoS requirements. Results from extensive simulations, testbed experiments, and multiple pilot hospital deployments show that MEDiSN can scale from tens to at least five hundred PMs, effectively protect application packets from congestive and corruptive losses, and deliver medically actionable data.
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paper_title: An adaptive mobility-aware MAC protocol for sensor networks (MS-MAC)

paper_content:

Most of the MAC protocols proposed for wireless sensor networks assume sensors to be stationary after deployment. This usually provides very bad network performance in scenarios involving mobile sensors. Handling mobility in wireless sensor networks in an energy-efficient way is a new challenge. Techniques developed for other mobile networks, such as mobile phone or mobile ad hoc networks, cannot be applicable, as in these networks, energy is not a very critical resource. The paper presents a new adaptive mobility-aware MAC protocol for sensor networks (MS-MAC). The protocol uses any change in received signal level as an indication of mobility and, when necessary, triggers the mobility handling mechanism. In this way, the new mobility-aware MAC protocol can work in a very energy-efficient way when the network is stationary, whereas it can maintain some level of network performance when there are mobile sensors.
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paper_title: Medium access control with a dynamic duty cycle for sensor networks

paper_content:

Energy conservation is a primary concern in sensor networks. Several MAC protocols have been proposed to address this concern. However, the tradeoff between power consumption and latency has not been thoroughly studied. In this paper, we propose a sensor medium access control protocol with dynamic duty cycle, DSMAC, which achieves a good tradeoff between the two performance metrics without incurring much overhead. Moreover, DSMAC is able to adjust its duty cycle with varying traffic conditions without assuming any prior knowledge of application requirements. Both analytical and simulation results have been presented in this paper.
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paper_title: Mobility-aware MAC protocol for delay-sensitive wireless sensor networks

paper_content:

Most of the MAC protocols proposed for the wireless sensor networks (WSN) assume sensor nodes to be static and therefore they usually fail or provide very bad network performance in mobile sensor networks. Since WSN mobile applications have become popular nowadays, there is a need for MAC protocols that consider mobility. In this paper, we propose a mobility-aware MAC protocol for WSN that can work with satisfactory performance in both stationary and mobile sensor networks. Furthermore, most of the WSN mobile applications are considered critical ones (e.g. a patient assistance system which monitors patients' health via wearable bio-sensors). Such applications require very quick responses. So, in addition to handling mobility, the proposed MAC protocol considers the problem of latency as well. In summary, this paper proposes a WSN MAC protocol (MD-SMAC) that is considered to be mobility-aware, delay-sensitive and provides satisfactory level of energy efficiency. In addition, we study the performance of the proposed MD-SMAC protocol by simulating it using the NS-2 simulator and comparing it to other WSN MAC protocols. The results show that the MD-SMAC protocol outperforms other existing WSN MAC protocols in terms of mobility-handling, delay-reduction, and energy-efficiency in scenarios involving mobile sensors.
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paper_title: DS-MAC: Differential service Medium Access Control design for wireless medical information systems

paper_content:

The integration of wireless networking technologies with medical information systems (telemedicine) have a significant impact on healthcare services provided to our society. Applications of telemedicine range from personalized medicine to affordable healthcare for underserved population. Though wireless technologies and medical informatics are individually progressing rapidly, wireless networking for healthcare systems is still at a very premature stage. In this paper we first present our open architecture for medical information systems that integrates both wired and wireless networked data acquisition systems. We then present the implementation at the physical layer and differential service MAC design that adapts channel provisioning based on the information criticality. Performance evaluation using analytical modeling and simulation shows that our DS-MAC provides differentiated services for emergency, warning, and normal traffic.
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paper_title: Collection tree protocol

paper_content:

This paper presents and evaluates two principles for wireless routing protocols. The first is datapath validation: data traffic quickly discovers and fixes routing inconsistencies. The second is adaptive beaconing: extending the Trickle algorithm to routing control traffic reduces route repair latency and sends fewer beacons. We evaluate datapath validation and adaptive beaconing in CTP Noe, a sensor network tree collection protocol. We use 12 different testbeds ranging in size from 20--310 nodes, comprising seven platforms, and six different link layers, on both interference-free and interference-prone channels. In all cases, CTP Noe delivers > 90% of packets. Many experiments achieve 99.9%. Compared to standard beaconing, CTP Noe sends 73% fewer beacons while reducing topology repair latency by 99.8%. Finally, when using low-power link layers, CTP Noe has duty cycles of 3% while supporting aggregate loads of 30 packets/minute.
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paper_title: Robust medical ad hoc sensor networks (MASN) with wavelet-based ECG data mining

paper_content:

Heart disease is the top elder killer in the world. To reduce the healthcare cost, it is a necessary tendency to deploy self-organized, wireless heart disease monitoring hardware/software systems. Telemedicine platform based on ad hoc interconnection of tiny ECG sensors, called medical ad hoc sensor networks (MASN), can provide a promising approach for performing low-cost, real-time, remote cardiac patient monitoring at any time. The contribution of this research is the design of a practical MASN hardware/software platform to perform real-time healthcare data collections. It has reliable, cluster-based communication scheme. Due to the radio broadcasting nature of wireless networks, a MASN has the risk of being attacked. This research also designs a low overhead medical security scheme to achieve confidential ECG data transmission in the wireless medium. Finally, our MASN system has the capability of keeping track of cardiac patients and extracting ECG features based on wavelet theories. Our MASN platform is very useful to practical medical monitoring applications.
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paper_title: An application-specific protocol architecture for wireless microsensor networks

paper_content:

Networking together hundreds or thousands of cheap microsensor nodes allows users to accurately monitor a remote environment by intelligently combining the data from the individual nodes. These networks require robust wireless communication protocols that are energy efficient and provide low latency. We develop and analyze low-energy adaptive clustering hierarchy (LEACH), a protocol architecture for microsensor networks that combines the ideas of energy-efficient cluster-based routing and media access together with application-specific data aggregation to achieve good performance in terms of system lifetime, latency, and application-perceived quality. LEACH includes a new, distributed cluster formation technique that enables self-organization of large numbers of nodes, algorithms for adapting clusters and rotating cluster head positions to evenly distribute the energy load among all the nodes, and techniques to enable distributed signal processing to save communication resources. Our results show that LEACH can improve system lifetime by an order of magnitude compared with general-purpose multihop approaches.
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paper_title: Ad-hoc multicast routing on resource-limited sensor nodes

paper_content:

Many emerging sensor network applications involve mobile nodes with communication patterns requiring any-to-any routing topologies. We should be able to build upon the MANET work to implement these systems. However, translating these protocols into real implementations on resource-constrained sensor nodes raises a number of challenges. In this paper, we present the lessons learned from implementing one such protocol, Adaptive Demand-driven Multicast Routing (ADMR), on CC2420-based motes using the TinyOS operating system. ADMR was chosen because it supports multicast communication, a critical requirement for many pervasive and mobile applications. To our knowledge, ours is the first non-simulated implementation of ADMR. Through extensive measurement on Motelab, we present the performance of the implementation, TinyADMR, under a wide range of conditions. We highlight the real-world impact of path selection metrics, radio link asymmetry, protocol overhead, and limited routing table size.
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paper_title: Empirical Study of a Medical Sensor Application in an Urban Emergency Department

paper_content:

User needs and technology availability drive the introduction of wireless sensing applications in clinical environments. While these applications have the potential to improve efficiency and quality of care, very little is known about their performance during day-to-day use at the hospital. In this work, we use data from a deployment of a 802.15.4-based wireless sensor network at the Emergency Room of the Johns Hopkins hospital to answer these questions. Specifically, over a period of ten days we deployed a system of wireless vital signs monitors that measure the heart rate and blood oxygen levels of Emergency Room patients. During this time we collected statistics about the network's RF links, the performance of its tree routing protocol, and its end-to-end reliability. We find that the hospital environment we tested has considerably higher radio noise levels across multiple frequency channels and more bursty links compared to other indoor environments. Nonetheless, the routing protocol we use finds high quality links and the end-to-end packet reception ratio is above 99.9%. Taken as a whole, these preliminary results suggest that despite the challenges that clinical environments pose, wireless medical sensing applications can perform well in these conditions.
---
paper_title: Sensor networks for medical care

paper_content:

Sensor networks have the potential to greatly impact many aspects of medical care. By outfitting patients with wireless, wearable vital sign sensors, collecting detailed real-time data on physiological status can be greatly simplified. However, there is a significant gap between existing sensor network systems and the needs of medical care. In particular, medical sensor networks must support multicast routing topologies, node mobility, a wide range of data rates and high degrees of reliability, and security. This paper describes our experiences with developing a combined hardware and software platform for medical sensor networks, called CodeBlue. CodeBlue provides protocols for device discovery and publish/subscribe multihop routing, as well as a simple query interface that is tailored for medical monitoring. We have developed several medical sensors based on the popular MicaZ and Telos mote designs, including a pulse oximeter, EKG and motion-activity sensor. We also describe a new, miniaturized sensor mote designed for medical use. We present initial results for the CodeBlue prototype demonstrating the integration of our medical sensors with the publish/subscribe routing substrate. We have experimentally validated the prototype on our 30-node sensor network testbed, demonstrating its scalability and robustness as the number of simultaneous queries, data rates, and transmitting sensors are varied. We also study the effect of node mobility, fairness across multiple simultaneous paths, and patterns of packet loss, confirming the system’s ability to maintain stable routes despite variations in node location and
---
paper_title: MEDiSN: Medical emergency detection in sensor networks

paper_content:

Staff shortages and an increasingly aging population are straining the ability of emergency departments to provide high quality care. At the same time, there is a growing concern about hospitals' ability to provide effective care during disaster events. For these reasons, tools that automate patient monitoring have the potential to greatly improve efficiency and quality of health care. Towards this goal, we have developed MEDiSN, a wireless sensor network for monitoring patients' physiological data in hospitals and during disaster events. MEDiSN comprises Physiological Monitors (PMs), which are custom-built, patient-worn motes that sample, encrypt, and sign physiological data and Relay Points (RPs) that self-organize into a multi-hop wireless backbone for carrying physiological data. Moreover, MEDiSN includes a back-end server that persistently stores medical data and presents them to authenticated GUI clients. The combination of MEDiSN's two-tier architecture and optimized rate control protocols allows it to address the compound challenge of reliably delivering large volumes of data while meeting the application's QoS requirements. Results from extensive simulations, testbed experiments, and multiple pilot hospital deployments show that MEDiSN can scale from tens to at least five hundred PMs, effectively protect application packets from congestive and corruptive losses, and deliver medically actionable data.
---
paper_title: Distributed clustering in ad-hoc sensor networks: a hybrid, energy-efficient approach

paper_content:

Prolonged network lifetime, scalability, and load balancing are important requirements for many ad-hoc sensor network applications. Clustering sensor nodes is an effective technique for achieving these goals. In this work, we propose a new energy-efficient approach for clustering nodes in ad-hoc sensor networks. Based on this approach, we present a protocol, HEED (hybrid energy-efficient distributed clustering), that periodically selects cluster heads according to a hybrid of their residual energy and a secondary parameter, such as node proximity to its neighbors or node degree. HEED does not make any assumptions about the distribution or density of nodes, or about node capabilities, e.g., location-awareness. The clustering process terminates in O(1) iterations, and does not depend on the network topology or size. The protocol incurs low overhead in terms of processing cycles and messages exchanged. It also achieves fairly uniform cluster head distribution across the network. A careful selection of the secondary clustering parameter can balance load among cluster heads. Our simulation results demonstrate that HEED outperforms weight-based clustering protocols in terms of several cluster characteristics. We also apply our approach to a simple application to demonstrate its effectiveness in prolonging the network lifetime and supporting data aggregation.
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paper_title: END-TO-END RELIABILITY IN WIRELESS SENSOR NETWORKS: SURVEY AND RESEARCH CHALLENGES

paper_content:

This paper presents a survey on transport and routing protocols for wireless sensor networks(WSN). Research challenges regarding the problem of end-to-end reliability are addressed in particular.
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paper_title: AdapCode: Adaptive Network Coding for Code Updates in Wireless Sensor Networks

paper_content:

Code updates, such as those for debugging purposes, are frequent and expensive in the early development stages of wireless sensor network applications. We propose AdapCode, a reliable data dissemination protocol that uses adaptive network coding to reduce broadcast traffic in the process of code updates. Packets on every node are coded by linear combination and decoded by Gaussian elimination. The core idea in AdapCode is to adaptively change the coding scheme according to the link quality. Our evaluation shows that AdapCode uses up to 40% less packets than Deluge in large networks. In addition, AdapCode performs much better in terms of load balancing, which prolongs the system lifetime, and has a slightly shorter propagation delay. Finally, we show that network coding is doable on sensor networks in that (i) it imposes only a 3 byte header overhead, (ii) it is easy to find linearly independent packets, and (3) Gaussian elimination needs only 1 KB of memory.
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paper_title: Pump-slowly, fetch-quickly (PSFQ): a reliable transport protocol for sensor networks

paper_content:

There is a growing need to support reliable data communications in sensor networks that are capable of supporting new applications, such as, assured delivery of high-priority events to sinks, reliable control and management of sensor networks, and remotely programming/retasking sensor nodes over-the-air. We present the design, implementation, and evaluation of pump slowly, fetch quickly (PSFQ), a simple, scalable, and robust transport protocol that is customizable to meet the needs of emerging reliable data applications in sensor networks. PSFQ represents a simple approach because it makes minimum assumptions about the underlying routing infrastructure, it is scalable and energy- efficient because it supports minimum signaling, thereby reducing the communication cost for data reliability, and importantly, it is robust because it is responsive to a wide range of operational error conditions found in sensor network, allowing for the successful operation of the protocol even under highly error-prone conditions. The key idea that underpins the design of PSFQ is to distribute data from a source node by pacing data at a relatively slow speed ("pump slowly"), but allowing nodes that experience data loss to fetch (i.e., recover) any missing segments from their local immediate neighbors aggressively ("fetch quickly"). We present the design and implementation of PSFQ, and evaluate the protocol using the ns-2 simulator and an experimental wireless sensor testbed based on Berkeley motes and the TinyOS operating system. We show that PSFQ can outperform existing related techniques and is highly responsive to the various error conditions experienced in sensor networks. The source code for PSFQ is freely available for experimentation.
---
paper_title: END-TO-END RELIABILITY IN WIRELESS SENSOR NETWORKS: SURVEY AND RESEARCH CHALLENGES

paper_content:

This paper presents a survey on transport and routing protocols for wireless sensor networks(WSN). Research challenges regarding the problem of end-to-end reliability are addressed in particular.
---
paper_title: AdapCode: Adaptive Network Coding for Code Updates in Wireless Sensor Networks

paper_content:

Code updates, such as those for debugging purposes, are frequent and expensive in the early development stages of wireless sensor network applications. We propose AdapCode, a reliable data dissemination protocol that uses adaptive network coding to reduce broadcast traffic in the process of code updates. Packets on every node are coded by linear combination and decoded by Gaussian elimination. The core idea in AdapCode is to adaptively change the coding scheme according to the link quality. Our evaluation shows that AdapCode uses up to 40% less packets than Deluge in large networks. In addition, AdapCode performs much better in terms of load balancing, which prolongs the system lifetime, and has a slightly shorter propagation delay. Finally, we show that network coding is doable on sensor networks in that (i) it imposes only a 3 byte header overhead, (ii) it is easy to find linearly independent packets, and (3) Gaussian elimination needs only 1 KB of memory.
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paper_title: TDMA Scheduling with Optimized Energy Efficiency and Minimum Delay in Clustered Wireless Sensor Networks

paper_content:

In this paper, we propose a solution to the scheduling problem in clustered wireless sensor networks (WSNs). The objective is to provide network-wide optimized time division multiple access (TDMA) schedules that can achieve high power efficiency, zero conflict, and reduced end-to-end delay. To achieve this objective, we first build a nonlinear cross-layer optimization model involving the network, medium access control (MAC), and physical layers, which aims at reducing the overall energy consumption. We solve this problem by transforming the model into two simpler subproblems. Based on the network-wide flow distribution calculated from the optimization model and transmission power on every link, we then propose an algorithm for deriving the TDMA schedules, utilizing the slot reuse concept to achieve minimum TDMA frame length. Numerical results reveal that our proposed solution reduces the energy consumption and delay significantly, while simultaneously satisfying a specified reliability objective.
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paper_title: Minimum-Cost Multicast over Coded Packet Networks

paper_content:

We consider the problem of establishing minimum-cost multicast connections over coded packet networks, i.e., packet networks where the contents of outgoing packets are arbitrary, causal functions of the contents of received packets. We consider both wireline and wireless packet networks as well as both static multicast (where membership of the multicast group remains constant for the duration of the connection) and dynamic multicast (where membership of the multicast group changes in time, with nodes joining and leaving the group). For static multicast, we reduce the problem to a polynomial-time solvable optimization problem, and we present decentralized algorithms for solving it. These algorithms, when coupled with existing decentralized schemes for constructing network codes, yield a fully decentralized approach for achieving minimum-cost multicast. By contrast, establishing minimum-cost static multicast connections over routed packet networks is a very difficult problem even using centralized computation, except in the special cases of unicast and broadcast connections. For dynamic multicast, we reduce the problem to a dynamic programming problem and apply the theory of dynamic programming to suggest how it may be solved.
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paper_title: Security issues of wireless sensor networks in healthcare applications

paper_content:

The emergence of wireless sensor networks (WSNs) in healthcare applications is gaining momentum through the increasing array of wearable vital sign sensors and location tags which can track both healthcare personnel and patient status/ location continuously in real-time mode. Despite the increased range of potential application frameworks -- ranging from pre-hospital, in-hospital, ambulatory and home monitoring, to long-term database collection for longitudinal trend analysis -- the security gap between existing WSN designs and the requirements of medical applications remains unresolved. ::: ::: Generally, WSN devices are extremely limited in terms of power, computation, and communication. They are often deployed in accessible areas, thus increasing security vulnerabilities. The dynamic ad hoc topology, multicast transmission, location awareness, critical data prioritisation, and co-ordination of diverse sensors of healthcare applications further exacerbate the security challenges. This paper presents an analysis of various WSN security mechanisms from the demanding perspective of healthcare applications, and considers the importance of security to the successful deployment of pervasive computing solutions in the healthcare industry.
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paper_title: Cross-Layer Energy and Delay Optimization in Small-Scale Sensor Networks

paper_content:

The general joint design of the physical, MAC, and routing layers to minimize network energy consumption is complex and hard to solve. Heuristics to compute approximate solutions and high-complexity algorithms to compute exact solutions have been previously proposed. In this paper, we focus on synchronous small-scale networks with interference-free link scheduling and practical MQAM link transmission schemes. We show that the cross-layer optimization problems can be closely approximated by convex optimization problems that can be efficiently solved. There are two main contributions of this paper. First of all, we minimize the total network energy that includes both transmission and circuit energy consumptions, where we explore the tradeoff between the two energy elements. Specifically, we use interference-free TDMA as the medium access control scheme. We optimize the routing flow, TDMA slot assignment, and MQAM modulation rate and power on each link. The results demonstrate that the minimum energy transmission scheme is a combination of multihop and single-hop transmissions for general networks; including circuit energy favors transmission schemes with fewer hops. Secondly, based on the solved optimal transmission scheme, we quantify the best trade-off curve between delay and energy consumption, where we derive a scheduling algorithm to minimize the worst-case packet delay.
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paper_title: Minimum-energy multicast in mobile ad hoc networks using network coding

paper_content:

The minimum energy required to transmit one bit of information through a network characterizes the most economical way to communicate in a network. In this paper, we show that, under a layered model of wireless networks, the minimum energy-per-bit for multicasting in a mobile ad hoc network can be found by a linear program; the minimum energy-per-bit can be attained by performing network coding. Compared with conventional routing solutions, network coding not only allows a potentially lower energy-per-bit to be achieved, but also enables the optimal solution to be found in polynomial time, in sharp contrast with the NP-hardness of constructing the minimum-energy multicast tree as the optimal routing solution. We further show that the minimum energy multicast formulation is equivalent to a cost minimization with linear edge-based pricing, where the edge prices are the energy-per-bits of the corresponding physical broadcast links. This paper also investigates minimum energy multicasting with routing. Due to the linearity of the pricing scheme, the minimum energy-per-bit for routing is achievable by using a single distribution tree. A characterization of the admissible rate region for routing with a single tree is presented. The minimum energy-per-bit for multicasting with routing is found by an integer linear program. We show that the relaxation of this integer linear program, studied earlier in the Steiner tree literature, can now be interpreted as the optimization for minimum energy multicasting with network coding. In short, this paper presents a unifying study of minimum energy multicasting with network coding and routing.
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paper_title: Sensor networks for medical care

paper_content:

Sensor networks have the potential to greatly impact many aspects of medical care. By outfitting patients with wireless, wearable vital sign sensors, collecting detailed real-time data on physiological status can be greatly simplified. However, there is a significant gap between existing sensor network systems and the needs of medical care. In particular, medical sensor networks must support multicast routing topologies, node mobility, a wide range of data rates and high degrees of reliability, and security. This paper describes our experiences with developing a combined hardware and software platform for medical sensor networks, called CodeBlue. CodeBlue provides protocols for device discovery and publish/subscribe multihop routing, as well as a simple query interface that is tailored for medical monitoring. We have developed several medical sensors based on the popular MicaZ and Telos mote designs, including a pulse oximeter, EKG and motion-activity sensor. We also describe a new, miniaturized sensor mote designed for medical use. We present initial results for the CodeBlue prototype demonstrating the integration of our medical sensors with the publish/subscribe routing substrate. We have experimentally validated the prototype on our 30-node sensor network testbed, demonstrating its scalability and robustness as the number of simultaneous queries, data rates, and transmitting sensors are varied. We also study the effect of node mobility, fairness across multiple simultaneous paths, and patterns of packet loss, confirming the system’s ability to maintain stable routes despite variations in node location and
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paper_title: Hierarchical Routing for Large Networks -- Performance evaluation and optimization

paper_content:

Abstract Distributed adaptive routing has proven to be useful in packet switching networks. However, the storage and updating cost of this routing procedure becomes prohibitive as the number of nodes in the network gets large. This paper deals with the specification, analysis and evaluation of some hierarchical routing procedures which are effective for large store-and-forward packet-switched computer networks. The procedures studied are an extension of present techniques and rely on a hierarchical clustering of the network nodes. In particular, optimal clustering structures are determined so as to minimize the length of the routing tables required. A price for reducing the table length is the increase in the average message path length in the network. Bounds are derived to evaluate the maximum increase in path length for a given table length. From this we obtain our key result, namely, that in the limit of a very large network, enormous table reduction may be achieved with essentially no increase in network path length.
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paper_title: Pervasive, secure access to a hierarchical sensor-based healthcare monitoring architecture in wireless heterogeneous networks

paper_content:

This study presents a healthcare monitoring architecture coupled with wearable sensor systems and an environmental sensor network for monitoring elderly or chronic patients in their residence. The wearable sensor system, built into a fabric belt, consists of various medical sensors that collect a timely set of physiological health indicators transmitted via low energy wireless communication to mobile computing devices. Three application scenarios are implemented using the proposed network architecture. The group-based data collection and data transmission using the ad hoc mode promote outpatient healthcare services for only one medical staff member assigned to a set of patients. Adaptive security issues for data transmission are performed based on different wireless capabilities. This study also presents a monitoring application prototype for capturing sensor data from wireless sensor nodes. The implemented schemes were verified as performing efficiently and rapidly in the proposed network architecture.
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paper_title: MEDiSN: Medical emergency detection in sensor networks

paper_content:

Staff shortages and an increasingly aging population are straining the ability of emergency departments to provide high quality care. At the same time, there is a growing concern about hospitals' ability to provide effective care during disaster events. For these reasons, tools that automate patient monitoring have the potential to greatly improve efficiency and quality of health care. Towards this goal, we have developed MEDiSN, a wireless sensor network for monitoring patients' physiological data in hospitals and during disaster events. MEDiSN comprises Physiological Monitors (PMs), which are custom-built, patient-worn motes that sample, encrypt, and sign physiological data and Relay Points (RPs) that self-organize into a multi-hop wireless backbone for carrying physiological data. Moreover, MEDiSN includes a back-end server that persistently stores medical data and presents them to authenticated GUI clients. The combination of MEDiSN's two-tier architecture and optimized rate control protocols allows it to address the compound challenge of reliably delivering large volumes of data while meeting the application's QoS requirements. Results from extensive simulations, testbed experiments, and multiple pilot hospital deployments show that MEDiSN can scale from tens to at least five hundred PMs, effectively protect application packets from congestive and corruptive losses, and deliver medically actionable data.
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Title: A Survey of System Architecture Requirements for Health Care-Based Wireless Sensor Networks

Section 1: Introduction
Description 1: Introduce the importance of wireless sensor networks in healthcare applications, outline the major requirements, and discuss the focus of the paper.

Section 2: Survey of Existing HCWSNs
Description 2: Provide a comprehensive literature survey of major existing health care wireless sensor networks like CodeBlue, MEDiSN, and MASN, and assess their performance.

Section 3: MAC Protocols for HCWSNs
Description 3: Review various Medium Access Control (MAC) protocols with a focus on energy efficiency, latency, and support for mobility, particularly CSMA-based protocols.

Section 4: Routing Protocols for HCWSNs
Description 4: Detail the characteristics and operation of routing protocols implemented in existing HCWSNs and discuss their strengths and weaknesses.

Section 5: End-to-End Reliable Transmission Mechanisms for HCWSNs
Description 5: Explore approaches to improve end-to-end reliability using reliable transport protocols and redundant transmissions and coding techniques.

Section 6: Network Coding Techniques for Improved Reliability
Description 6: Review the application of network coding techniques to enhance reliability in HCWSNs and discuss potential benefits and limitations.

Section 7: Discussion
Description 7: Identify and discuss specific areas for further research to close identified gaps in the context of HCWSNs, including energy efficiency, traffic prioritization, data aggregation, and security schemes.

Section 8: Conclusions
Description 8: Summarize the key findings from the survey, highlight the most promising approaches for reliable communication in HCWSNs, and suggest future research directions.