Time synchronization provides the basis for several applications in wireless sensor networks but the limited memory and computational power, and the use of low precision oscillators make the task of time synchronization non-trivial. In this demonstration, we present a novel time synchronization scheme that is based on time series analysis. To provide a general model for the practical behavior of low precision oscillators, autoregressive integrated moving average models are explored. Based on the analysis of experimental data, an autoregressive integrated model (ARI (1,1)) is derived. Unlike the resource hungry Kalman filter based formulations, the proposed scheme is resource efficient as it results in simple linear regression processing. Experiments are performed on real sensor devices including Zolertia and TelosB, where an accuracy below 1 clock tick 1 is achieved.
{"title":"Demo: Exploring Autoregressive Integrated Models for Time Synchronization in Wireless Sensor Networks","authors":"Wasif Masood, J. F. Schmidt","doi":"10.1145/2789168.2789182","DOIUrl":"https://doi.org/10.1145/2789168.2789182","url":null,"abstract":"Time synchronization provides the basis for several applications in wireless sensor networks but the limited memory and computational power, and the use of low precision oscillators make the task of time synchronization non-trivial. In this demonstration, we present a novel time synchronization scheme that is based on time series analysis. To provide a general model for the practical behavior of low precision oscillators, autoregressive integrated moving average models are explored. Based on the analysis of experimental data, an autoregressive integrated model (ARI (1,1)) is derived. Unlike the resource hungry Kalman filter based formulations, the proposed scheme is resource efficient as it results in simple linear regression processing. Experiments are performed on real sensor devices including Zolertia and TelosB, where an accuracy below 1 clock tick 1 is achieved.","PeriodicalId":424497,"journal":{"name":"Proceedings of the 21st Annual International Conference on Mobile Computing and Networking","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125270933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper describes the design and implementation of AirExpress, a system that enables in-band wireless cut-through transmission. Unlike wired cut-through, wireless cut-through can reduce latency and improve throughput performance of the network at the same time. In AirExpress, all the forwarders along the cut-through path forward the signal they received immediately without decoding. The hierarchical structure of AirExpress enables its interference cancellation ability to handle all kinds of interference among the radios. Novel MAC and routing algorithms based on cut-through transmission are also proposed to support the realization of AirExpress in multi-hop mesh networks. AirExpress is implemented on an NI-based SDR platform. Through experiments in the 2.4GHz ISM band, we show throughput gain of up to 3.4 times with a 4-hop AirExpress system. Trace driven evaluation of AirExpress on the NS3 platform shows an average throughput gain of 2.85 for AirExpress over optimal TDMA.
{"title":"AirExpress: Enabling Seamless In-band Wireless Multi-hop Transmission","authors":"Bo Chen, Yue Qiao, Ouyang Zhang, K. Srinivasan","doi":"10.1145/2789168.2790114","DOIUrl":"https://doi.org/10.1145/2789168.2790114","url":null,"abstract":"This paper describes the design and implementation of AirExpress, a system that enables in-band wireless cut-through transmission. Unlike wired cut-through, wireless cut-through can reduce latency and improve throughput performance of the network at the same time. In AirExpress, all the forwarders along the cut-through path forward the signal they received immediately without decoding. The hierarchical structure of AirExpress enables its interference cancellation ability to handle all kinds of interference among the radios. Novel MAC and routing algorithms based on cut-through transmission are also proposed to support the realization of AirExpress in multi-hop mesh networks. AirExpress is implemented on an NI-based SDR platform. Through experiments in the 2.4GHz ISM band, we show throughput gain of up to 3.4 times with a 4-hop AirExpress system. Trace driven evaluation of AirExpress on the NS3 platform shows an average throughput gain of 2.85 for AirExpress over optimal TDMA.","PeriodicalId":424497,"journal":{"name":"Proceedings of the 21st Annual International Conference on Mobile Computing and Networking","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123054847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Intermittent connection of wireless links, caused by low duty-cycle radio operation, harsh working environment, movement of sensor nodes, etc., makes clock synchronization a challenging task. Prior synchronization approaches in wireless sensor networks (WSNs) typically require that nodes exchange time messages frequently with the reference clock, which is difficult in networks with low or intermittent connectivity. This poster presents RobSync, a robust design for clock synchronization in intermittent-connected wireless networks. Having recognized that clock skew is highly correlated to the voltage supply, we use the local voltage information as a reference for clock self-calibration, which helps reduce the frequency of time-stamp exchanges. To prevent a misuse of the voltage information, leading to error accumulation, a re-synchronization interval adjustment design is developed to make a trade-off between accuracy and energy consumption. We present the theory behind RobSync, and provide preliminary results by experiments to compare our approach and the recent approach.
{"title":"Poster: An Insomnia Therapy for Clock Synchronization in Wireless Sensor Networks","authors":"Meng Jin, Dingyi Fang, Xiaojiang Chen, Lin X. Cai, Zhe Yang, Zhanyong Tang","doi":"10.1145/2789168.2795184","DOIUrl":"https://doi.org/10.1145/2789168.2795184","url":null,"abstract":"Intermittent connection of wireless links, caused by low duty-cycle radio operation, harsh working environment, movement of sensor nodes, etc., makes clock synchronization a challenging task. Prior synchronization approaches in wireless sensor networks (WSNs) typically require that nodes exchange time messages frequently with the reference clock, which is difficult in networks with low or intermittent connectivity. This poster presents RobSync, a robust design for clock synchronization in intermittent-connected wireless networks. Having recognized that clock skew is highly correlated to the voltage supply, we use the local voltage information as a reference for clock self-calibration, which helps reduce the frequency of time-stamp exchanges. To prevent a misuse of the voltage information, leading to error accumulation, a re-synchronization interval adjustment design is developed to make a trade-off between accuracy and energy consumption. We present the theory behind RobSync, and provide preliminary results by experiments to compare our approach and the recent approach.","PeriodicalId":424497,"journal":{"name":"Proceedings of the 21st Annual International Conference on Mobile Computing and Networking","volume":"92 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133571631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To explore the applicability of mobile smart devices to personal protection against violent crime, we propose a system that can detect the onset of hazardous situations involving violent crime by leveraging standard activity recognition strategies on smartphones and sensory inputs from wearable devices, as well as send help requests to alert the authorities.
{"title":"Poster: Can Smart Devices Protect Us from Violent Crime?","authors":"Alan Ferrari, D. Puccinelli, S. Giordano","doi":"10.1145/2789168.2795160","DOIUrl":"https://doi.org/10.1145/2789168.2795160","url":null,"abstract":"To explore the applicability of mobile smart devices to personal protection against violent crime, we propose a system that can detect the onset of hazardous situations involving violent crime by leveraging standard activity recognition strategies on smartphones and sensory inputs from wearable devices, as well as send help requests to alert the authorities.","PeriodicalId":424497,"journal":{"name":"Proceedings of the 21st Annual International Conference on Mobile Computing and Networking","volume":"262 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131725455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Figure 1: Overview of WiPrint system. User can input a floor plan, location of an AP and a desired signal map to the system. The desired signal pattern is marked with red and black regions indicating areas which should have strong and weak signals respectively. WiPrint uses an optimization algorithm to produce a reflector shape. This reflector is then fabricated and applied to an AP to achieve this desired signal pattern.
{"title":"Poster: 3D Printing Your Wireless Coverage","authors":"Justin Chan, Changxi Zheng, Xia Zhou","doi":"10.1145/2789168.2795164","DOIUrl":"https://doi.org/10.1145/2789168.2795164","url":null,"abstract":"Figure 1: Overview of WiPrint system. User can input a floor plan, location of an AP and a desired signal map to the system. The desired signal pattern is marked with red and black regions indicating areas which should have strong and weak signals respectively. WiPrint uses an optimization algorithm to produce a reflector shape. This reflector is then fabricated and applied to an AP to achieve this desired signal pattern.","PeriodicalId":424497,"journal":{"name":"Proceedings of the 21st Annual International Conference on Mobile Computing and Networking","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116269630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents mZig, a novel physical layer design that enables a receiver to simultaneously decode multiple packets from different transmitters in ZigBee. As a low-power and low-cost wireless protocol, the promising ZigBee has been widely used in sensor networks, cyber-physical systems, and smart buildings. Since ZigBee based networks usually adopt tree or cluster topology, the convergecast scenarios are common in which multiple transmitters need to send packets to one receiver. For example, in a smart home, all appliances report data to one control plane via ZigBee. However, concurrent transmissions in convergecast lead to the severe collision problem. The conventional ZigBee avoids collisions using backoff time, which introduces additional time overhead. Advanced methods resolve collisions instead of avoidance, in which the state-of-the-art ZigZag resolves one m-packet collision requiring m retransmissions. We propose mZig to resolve one m-packet collision by this collision itself, so the theoretical throughput is improved m-fold. Leveraging the unique features in ZigBee's physical layer including its chip rate, half-sine pulse shaping and O-QPSK modulation, mZig subtly decomposes multiple packets from one collision in baseband signal processing. The practical factors of noise, multipath, and frequency offset are taken into account in mZig design. We implement mZig on USRPs and establish a seven-node testbed. Experiment results demonstrate that mZig can receive up to four concurrent packets in our testbed. The throughput of mZig is 4.5x of the conventional ZigBee and 3.2x of ZigZag in the convergecast with four or more transmitters.
{"title":"mZig","authors":"L. Kong, Xuemei Liu","doi":"10.1145/2789168.2790104","DOIUrl":"https://doi.org/10.1145/2789168.2790104","url":null,"abstract":"This paper presents mZig, a novel physical layer design that enables a receiver to simultaneously decode multiple packets from different transmitters in ZigBee. As a low-power and low-cost wireless protocol, the promising ZigBee has been widely used in sensor networks, cyber-physical systems, and smart buildings. Since ZigBee based networks usually adopt tree or cluster topology, the convergecast scenarios are common in which multiple transmitters need to send packets to one receiver. For example, in a smart home, all appliances report data to one control plane via ZigBee. However, concurrent transmissions in convergecast lead to the severe collision problem. The conventional ZigBee avoids collisions using backoff time, which introduces additional time overhead. Advanced methods resolve collisions instead of avoidance, in which the state-of-the-art ZigZag resolves one m-packet collision requiring m retransmissions. We propose mZig to resolve one m-packet collision by this collision itself, so the theoretical throughput is improved m-fold. Leveraging the unique features in ZigBee's physical layer including its chip rate, half-sine pulse shaping and O-QPSK modulation, mZig subtly decomposes multiple packets from one collision in baseband signal processing. The practical factors of noise, multipath, and frequency offset are taken into account in mZig design. We implement mZig on USRPs and establish a seven-node testbed. Experiment results demonstrate that mZig can receive up to four concurrent packets in our testbed. The throughput of mZig is 4.5x of the conventional ZigBee and 3.2x of ZigZag in the convergecast with four or more transmitters.","PeriodicalId":424497,"journal":{"name":"Proceedings of the 21st Annual International Conference on Mobile Computing and Networking","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124475862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lan Zhang, Cheng Bo, Jiahui Hou, Xiangyang Li, Yang Wang, Kebin Liu, Yunhao Liu
Recently a number of systems have been developed to implement and improve the visual communication over screen-camera links. In this paper we study an opposite problem: how to prevent unauthorized users from videotaping a video played on a screen, such as in a theater, while do not affect the viewing experience of legitimate audiences. We propose and develop a light-weight hardware-free system, called Kaleido, that ensures these properties by taking advantage of the limited disparities between the screen-eye channel and the screen-camera channel. Kaleido does not require any extra hardware and is purely based on re-encoding the original video frame into multiple frames used for displaying. We extensively test our system Kaleido using a variety of smartphone cameras. Our experiments confirm that Kaleido preserves the high-quality screen-eye channel while reducing the secondary screen-camera channel quality significantly.
{"title":"Kaleido: You Can Watch It But Cannot Record It","authors":"Lan Zhang, Cheng Bo, Jiahui Hou, Xiangyang Li, Yang Wang, Kebin Liu, Yunhao Liu","doi":"10.1145/2789168.2790106","DOIUrl":"https://doi.org/10.1145/2789168.2790106","url":null,"abstract":"Recently a number of systems have been developed to implement and improve the visual communication over screen-camera links. In this paper we study an opposite problem: how to prevent unauthorized users from videotaping a video played on a screen, such as in a theater, while do not affect the viewing experience of legitimate audiences. We propose and develop a light-weight hardware-free system, called Kaleido, that ensures these properties by taking advantage of the limited disparities between the screen-eye channel and the screen-camera channel. Kaleido does not require any extra hardware and is purely based on re-encoding the original video frame into multiple frames used for displaying. We extensively test our system Kaleido using a variety of smartphone cameras. Our experiments confirm that Kaleido preserves the high-quality screen-eye channel while reducing the secondary screen-camera channel quality significantly.","PeriodicalId":424497,"journal":{"name":"Proceedings of the 21st Annual International Conference on Mobile Computing and Networking","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125316568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. H. Bui, Yunxin Liu, Hyosu Kim, I. Shin, Feng Zhao
Web browsing is a key application on mobile devices. However, mobile browsers are largely optimized for performance, imposing a significant burden on power-hungry mobile devices. In this work, we aim to reduce the energy consumed to load web pages on smartphones, preferably without increasing page load time and compromising user experience. To this end, we first study the internals of web page loading on smartphones and identify its energy-inefficient behaviors. Based on our findings, we then derive general design principles for energy-efficient web page loading, and apply these principles to the open-source Chromium browser and implement our techniques on commercial smartphones. Experimental results show that our techniques are able to achieve a 24.4% average system energy saving for Chromium on a latest-generation big.LITTLE smartphone using WiFi (a 22.5% saving when using 3G), while not increasing average page load time. We also show that our proposed techniques can bring a 10.5% system energy saving on average with a small 1.69% increase in page load time for mobile Firefox web browser. User study results indicate that such a small increase in page load time is hardly perceivable.
{"title":"Rethinking Energy-Performance Trade-Off in Mobile Web Page Loading","authors":"D. H. Bui, Yunxin Liu, Hyosu Kim, I. Shin, Feng Zhao","doi":"10.1145/2789168.2790103","DOIUrl":"https://doi.org/10.1145/2789168.2790103","url":null,"abstract":"Web browsing is a key application on mobile devices. However, mobile browsers are largely optimized for performance, imposing a significant burden on power-hungry mobile devices. In this work, we aim to reduce the energy consumed to load web pages on smartphones, preferably without increasing page load time and compromising user experience. To this end, we first study the internals of web page loading on smartphones and identify its energy-inefficient behaviors. Based on our findings, we then derive general design principles for energy-efficient web page loading, and apply these principles to the open-source Chromium browser and implement our techniques on commercial smartphones. Experimental results show that our techniques are able to achieve a 24.4% average system energy saving for Chromium on a latest-generation big.LITTLE smartphone using WiFi (a 22.5% saving when using 3G), while not increasing average page load time. We also show that our proposed techniques can bring a 10.5% system energy saving on average with a small 1.69% increase in page load time for mobile Firefox web browser. User study results indicate that such a small increase in page load time is hardly perceivable.","PeriodicalId":424497,"journal":{"name":"Proceedings of the 21st Annual International Conference on Mobile Computing and Networking","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125196371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Georgios Z. Papadopoulos, A. Gallais, G. Schreiner, Thomas Noël
This demonstration aims at observing in an interactive manner the impact of modification of preamble and sampling periods at the low-power family of MAC protocols, and thus, illustrating in real-time the energy consumption and delay performance of each node accordingly. To do so, we implemented the ability for users to generate traffic at some remote nodes that are involved in two distinct deployed topologies. Those deployed networks operate with either a statically configured network, by employing X-MAC on top of the Contiki OS, or T-AAD, a lightweight traffic auto-adaptive protocol that allows live and automatic modifications of duty-cycle configurations.
{"title":"Demo: Abstract: Live Adaptations of Low-power MAC Protocols","authors":"Georgios Z. Papadopoulos, A. Gallais, G. Schreiner, Thomas Noël","doi":"10.1145/2789168.2789184","DOIUrl":"https://doi.org/10.1145/2789168.2789184","url":null,"abstract":"This demonstration aims at observing in an interactive manner the impact of modification of preamble and sampling periods at the low-power family of MAC protocols, and thus, illustrating in real-time the energy consumption and delay performance of each node accordingly. To do so, we implemented the ability for users to generate traffic at some remote nodes that are involved in two distinct deployed topologies. Those deployed networks operate with either a statically configured network, by employing X-MAC on top of the Contiki OS, or T-AAD, a lightweight traffic auto-adaptive protocol that allows live and automatic modifications of duty-cycle configurations.","PeriodicalId":424497,"journal":{"name":"Proceedings of the 21st Annual International Conference on Mobile Computing and Networking","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129309601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Giulio Grassi, Matteo Sammarco, P. Bahl, K. Jamieson, G. Pau
In this work we propose ParkMaster, a low-cost crowdsourcing architecture which exploits machine learning techniques and vision algorithms to evaluate parking availability in cities. While the user is normally driving ParkMaster enables off the shelf smartphones to collect information about the presence of parked vehicles by running image recognition techniques on the phones camera video streaming. The paper describes the design of ParkMaster's architecture and shows the feasibility of deploying such mobile sensor system in nowadays smartphones, in particular focusing on the practicability of running vision algorithms on phones.
{"title":"Poster: ParkMaster: Leveraging Edge Computing in Visual Analytics","authors":"Giulio Grassi, Matteo Sammarco, P. Bahl, K. Jamieson, G. Pau","doi":"10.1145/2789168.2795174","DOIUrl":"https://doi.org/10.1145/2789168.2795174","url":null,"abstract":"In this work we propose ParkMaster, a low-cost crowdsourcing architecture which exploits machine learning techniques and vision algorithms to evaluate parking availability in cities. While the user is normally driving ParkMaster enables off the shelf smartphones to collect information about the presence of parked vehicles by running image recognition techniques on the phones camera video streaming. The paper describes the design of ParkMaster's architecture and shows the feasibility of deploying such mobile sensor system in nowadays smartphones, in particular focusing on the practicability of running vision algorithms on phones.","PeriodicalId":424497,"journal":{"name":"Proceedings of the 21st Annual International Conference on Mobile Computing and Networking","volume":"1601 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129200606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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