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59
smap: a simple measurement and actuation profile for physical information.
- In Proceedings of the 8th ACM Conference on Embedded Networked Sensor Systems, SenSys ’10,
, 2010
"... Abstract As more and more physical information becomes available, a critical problem is enabling the simple and efficient exchange of this data. We present our design for a simple RESTful web service called the Simple Measuring and Actuation Profile (sMAP) which allows instruments and other produce ..."
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Cited by 58 (17 self)
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Abstract As more and more physical information becomes available, a critical problem is enabling the simple and efficient exchange of this data. We present our design for a simple RESTful web service called the Simple Measuring and Actuation Profile (sMAP) which allows instruments and other producers of physical information to directly publish their data. In our design study, we consider what information should be represented, and how it fits into the RESTful paradigm. To evaluate sMAP, we implement a large number of data sources using this profile, and consider how easy it is to use to build new applications. We also design and evaluate a set of adaptations made at each layer of the protocol stack which allow sMAP to run on constrained devices.
Surviving Wi-Fi Interference in Low Power ZigBee Networks
"... Frequency overlap across wireless networks with different radio technologies can cause severe interference and reduce communication reliability. The circumstances are particularly unfavorable for ZigBee networks that share the 2.4 GHz ISM band with WiFi senders capable of 10 to 100 times higher tran ..."
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Cited by 52 (1 self)
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Frequency overlap across wireless networks with different radio technologies can cause severe interference and reduce communication reliability. The circumstances are particularly unfavorable for ZigBee networks that share the 2.4 GHz ISM band with WiFi senders capable of 10 to 100 times higher transmission power. Our work first examines the interference patterns between ZigBee and WiFi networks at the bit-level granularity. Under certain conditions, ZigBee activities can trigger a nearby WiFi transmitter to back off, in which case the header is often the only part of the Zig-Bee packet being corrupted. We call this the symmetric interference regions, in comparison to the asymmetric regions where the ZigBee signal is too weak to be detected by WiFi senders, but WiFi activity can uniformly corrupt any bit in a ZigBee packet. With these observations, we design BuzzBuzz to mitigate WiFi interference through header and payload redundancy. Multi-Headers provides header redundancy giving ZigBee nodes multiple opportunities to detect incoming packets. Then, TinyRS, a full-featured Reed Solomon library for resource-constrained devices, helps decoding polluted packet payload. On a medium-sized testbed, BuzzBuzz improves the ZigBee network delivery rate by 70%. Furthermore, BuzzBuzz reduces ZigBee retransmissions by a factor of three, which increases the WiFi throughput by 10%.
Exploring link correlation for efficient flooding in wireless sensor networks
- In NSDI ’10
"... Existing flooding algorithms have demonstrated their effectiveness in achieving communication efficiency and reliability in wireless sensor networks. However, further performance improvement has been hampered by the assumption of link independence, a design premise imposing the need for costly ackno ..."
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Cited by 28 (11 self)
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Existing flooding algorithms have demonstrated their effectiveness in achieving communication efficiency and reliability in wireless sensor networks. However, further performance improvement has been hampered by the assumption of link independence, a design premise imposing the need for costly acknowledgements (ACKs) from every receiver. In this paper, we present Collective Flooding (CF), which exploits thelinkcorrelation to achieve flooding reliability using the concept of collective ACKs. CF requires only 1-hop information from a sender, making the design highly distributed and scalable with low complexity. We evaluate CF extensively in realworld settings, using three different types of testbeds: a single hop network with 20 MICAz nodes, a multihop network with 37 nodes, and a linear outdoor network with 48 nodes along a 326-meter-long bridge. System evaluation and extensive simulation show that CF achieves the same reliability as the state-of-the art solutions, while reducing the total number of packet transmission and dissemination delay by 30 ∼ 50 % and 35 ∼ 50%, respectively. 1
Low-power wireless bus
- in Proc. ACM Conf. on Embedded Networked Sensor Systems (SenSys
, 2012
"... We present the Low-Power Wireless Bus (LWB), a communication protocol that supports several traffic patterns and mobile nodes immersed in static infrastructures. LWB turns a multi-hop low-power wireless network into an infrastructure similar to a shared bus, where all nodes are potential receivers o ..."
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Cited by 21 (5 self)
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We present the Low-Power Wireless Bus (LWB), a communication protocol that supports several traffic patterns and mobile nodes immersed in static infrastructures. LWB turns a multi-hop low-power wireless network into an infrastructure similar to a shared bus, where all nodes are potential receivers of all data. It achieves this by mapping all traffic demands on fast network floods, and by globally scheduling every flood. As a result, LWB inherently supports one-tomany, many-to-one, and many-to-many traffic. LWB also keeps no topology-dependent state, making it more resilient to link changes due to interference, node failures, and mobility than prior approaches. We compare the same LWB prototype on four testbeds with seven state-of-the-art protocols and show that: (i) LWB performs comparably or significantly better in many-to-one scenarios, and adapts efficiently to varying traffic loads; (ii) LWB outperforms our baselines in many-to-many scenarios, at times by orders of magnitude; (iii) external interference and node failures affect LWB’s performance only marginally; (iv) LWB supports mobile nodes acting as sources, sinks, or both without performance loss.
Thermocast: a cyber-physical forecasting model for data centers
- In 17th ACM Conference on Knowledge Discovery and Data Mining
, 2011
"... ABSTRACT Efficient thermal management is important in modern data centers as cooling consumes up to 50% of the total energy. Unlike previous work, we consider proactive thermal management, whereby servers can predict potential overheating events due to dynamics in data center configuration and work ..."
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Cited by 20 (3 self)
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ABSTRACT Efficient thermal management is important in modern data centers as cooling consumes up to 50% of the total energy. Unlike previous work, we consider proactive thermal management, whereby servers can predict potential overheating events due to dynamics in data center configuration and workload, giving operators enough time to react. However, such forecasting is very challenging due to data center scales and complexity. Moreover, such a physical system is influenced by cyber effects, including workload scheduling in servers. We propose ThermoCast, a novel thermal forecasting model to predict the temperatures surrounding the servers in a data center, based on continuous streams of temperature and airflow measurements. Our approach is (a) capable of capturing cyberphysical interactions and automatically learning them from data; (b) computationally and physically scalable to data center scales; (c) able to provide online prediction with real-time sensor measurements. The paper's main contributions are: (i) We provide a systematic approach to integrate physical laws and sensor observations in a data center; (ii) We provide an algorithm that uses sensor data to learn the parameters of a data center's cyber-physical system. In turn, this ability enables us to reduce model complexity compared to full-fledged fluid dynamics models, while maintaining forecast accuracy; (iii) Unlike previous simulation-based studies, we perform experiments in a production data center. Using real data traces, we show that ThermoCast forecasts temperature 2× better than a machine learning approach solely driven by data, and can successfully predict thermal alarms 4.2 minutes ahead of time.
@scale: Insights from a Large, Long-Lived Appliance Energy WSN
"... We present insights obtained from conducting a year-long, 455 meter deployment of wireless plug-load electric meters in a large commercial building. We develop a stratified sampling methodology for surveying the energy use of Miscellaneous Electric Loads (MELs) in commercial buildings, and apply it ..."
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Cited by 13 (1 self)
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We present insights obtained from conducting a year-long, 455 meter deployment of wireless plug-load electric meters in a large commercial building. We develop a stratified sampling methodology for surveying the energy use of Miscellaneous Electric Loads (MELs) in commercial buildings, and apply it to our study building. Over the deployment period, we collected over nine hundred million individual readings. Among our findings, we document the need for a dynamic, scalable IPv6 routing protocol which supports point-to-point routing and multiple points of egress. Although the meters are static physically, we find that the set of links they use is dynamic; not using such a dynamic set results in paths that are twice as long. Finally, we conduct a detailed survey of the accuracy possible with inexpensive AC metering hardware. Based on a 21-point automated calibration of a population of 500 devices, we find that it is possible to produce nearly utility-grade metering data.
Maximizing lifetime for the shortest path aggregation tree in wireless sensor networks
- in Proc. INFOCOM
"... Abstract—In many applications of wireless sensor networks, a sensor node senses the environment to get data and delivers them to the sink via a single hop or multi-hop path. Many systems use a tree rooted at the sink as the underlying routing structure. Since the sensor node is energy constrained, h ..."
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Cited by 12 (4 self)
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Abstract—In many applications of wireless sensor networks, a sensor node senses the environment to get data and delivers them to the sink via a single hop or multi-hop path. Many systems use a tree rooted at the sink as the underlying routing structure. Since the sensor node is energy constrained, how to construct a good tree to prolong the lifetime of the network is an important problem. We consider this problem under the scenario where nodes have different initial energy, and they can do in-network aggregation. In previous works, it has been proved that finding a maximum lifetime tree from all feasible spanning trees is NP-complete. Since delay is also an important element in time-critical applications, and shortest path trees intuitively have short delay, it is imperative to find a shortest path tree with long lifetime. This paper studies the problem of maximizing the lifetime of data aggregation trees, which are limited to shortest path trees. We find that when it is restricted to shortest path trees, the original problem is in P. We transform the problem into a general version of semi-matching problem, and show that the problem can be solved by min-cost max-flow approach in polynomial time. Also we design a distributed solution. Simulation results show that our approach greatly improves the lifetime of the network and is more competitive when it is applied in a dense network. I.
A case against routing-integrated time synchronization
- in Proc. of ACM Sensys
, 2010
"... To achieve more accurate global time synchronization, this paper argues for decoupling the clock distribution network from the routing tree in a multihop wireless network. We find that both flooding and routing-integrated time synchronization rapidly propagate node-level errors (typically due to tem ..."
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Cited by 12 (0 self)
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To achieve more accurate global time synchronization, this paper argues for decoupling the clock distribution network from the routing tree in a multihop wireless network. We find that both flooding and routing-integrated time synchronization rapidly propagate node-level errors (typically due to temperature fluctuations) across the network. Therefore, we propose that a node chooses synchronization neighbors that offer the greatest frequency stability. We propose two methods to estimate a neighbor’s stability. The first approach selects the neighbor whose Frequency Error Variance, or simply FEV, is smallest with respect to the local clock. The second approach selects the neighbor that reports the lowest FEV relative to its synchronization parent. We also propose the node-level time-variance FEV as an additive metric for selecting more stable clock trees than either naïve flooding or routing-integrated time synchronization can provide. We incorporate these techniques into FTSP, a widelyused time synchronization protocol, and show that the mean error in global time significantly improved (by a factor of five) when some nodes are warmed and others are not.
Joint optimization of computing and cooling energy: Analytic model and a machine room case study
- in Proceedings of the 2012 IEEE 32Nd International Conference on Distributed Computing Systems, ser. ICDCS ’12
"... Abstract—Total energy minimization in data centers (includ-ing both computing and cooling energy) requires modeling the interactions between computing decisions (such as load distribution) and heat transfer in the room, since load acts as heat sources whose distribution in space affects cooling ener ..."
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Cited by 11 (5 self)
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Abstract—Total energy minimization in data centers (includ-ing both computing and cooling energy) requires modeling the interactions between computing decisions (such as load distribution) and heat transfer in the room, since load acts as heat sources whose distribution in space affects cooling energy. This paper presents the first closed-form analytic optimal solution for load distribution in a machine rack that minimizes the sum of computing and cooling energy. We show that by considering actuation knobs on both computing and cooling sides, it is possible to reduce energy cost comparing to state of the art solutions that do not offer holistic energy optimization. The above can be achieved while meeting both throughput requirements and maximum CPU temperature constraints. Using a thorough evaluation on a real testbed of 20 machines, we demonstrate that our simple model adequately captures the thermal behavior and energy consumption of the system. We further show that our approach saves more energy compared to the state of the art in the field. Keywords-data-center; optimal load allocation; energy opti-mization; testbed; practical; I.
Synchronized Aggregate Signatures: New Definitions, Constructions and Applications
- Proceedings of the Annual Conference on Computer and Communications Security (CCS
, 2010
"... An aggregate signature scheme is a digital signature scheme where anyone given n signatures on n messages from n users can aggregate all these signatures into a single short signature. Unfortunately, no “fully non-interactive ” aggregate signature schemes are known outside of the random oracle heuri ..."
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Cited by 11 (1 self)
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An aggregate signature scheme is a digital signature scheme where anyone given n signatures on n messages from n users can aggregate all these signatures into a single short signature. Unfortunately, no “fully non-interactive ” aggregate signature schemes are known outside of the random oracle heuristic; that is, signers must pass messages between themselves, sequentially or otherwise, to generate the signature. Interaction is too costly for some interesting applications. In this work, we consider the task of realizing aggregate signatures in the model of Gentry and Ramzan (PKC 2006) when all signers share a synchronized clock, but do not need to be aware of or interactive with one another. Each signer may issue at most one signature per time period and signatures aggregate only if they were created during the same time period. We call this synchronized aggregation. We present a practical synchronized aggregate signature scheme secure under the Computational Diffie-Hellman assumption in the standard model. Our construction is based on the stateful signatures of Hohenberger and Waters (Eurocrypt 2009). Those signatures do not aggregate since each signature includes unique randomness for a chameleon hash and those random values do not compress. To overcome this challenge, we remove the chameleon hash from their scheme and find an alternative method for moving from weak to full security that enables aggregation. We conclude by discussing applications of this construction to sensor networks and software authentication. 1
