Research Projects

 Our research is focused on system and application issues in computer and sensor networks.  And a large portion will be anytime-anywhere computing, which will open many opportunities for mobile applications and systems to support the needs.  

Specifically, we focus our research on three areas: 1) network issues (e.g., routing, link measurement); 2) network system (e.g., software-defined network, mobile phones, sensors, vehicles); and 3) data analysis (e.g., network traffic, mobile object trajectory, energy usage from smart meter). 

Conferences Interested: ACM SIGCOMM, ACM MobiCom/MobiSys, IEEE INFOCOM,  ACM SenSys, IEEE International Systems Conference (SysCon) / IEEE System Journal, IEEE International Conference on Communications (ICC), IEEE GLOBECOM, IEEE Sensors / Sensors Journal, IEEE Vehicular Technology /IEEE Transactions on Vehicular Technology, ACM e-Energy. 

SELECTED RESEARCH & PROJECTS

Creating a Safe Learning Environment in the Age of Respiratory Infectious Diseases Pandemic

Develop a miniature indoor air quality sensing device and strategically deploy the air sensing device for air quality detection to prevent the spreading of the flu and respiratory infectious diseases for learning environments

Aug. 2021 to Present

Sponsored by Ministry of Science and Technology, Taiwan 

Grant Number: MOST 110-2221-E-003-001 

In the era of the flu and respiratory infectious diseases pandemic, some of the basic protective and preventive measures for learning environments are infrared body temperature measurement, disinfection protection, personnel entry and exit records, and other measures. In addition to the basic protection measurements, the indoor air quality monitoring for learning environments can faithfully reflect the indoor air circulation of indoor and outdoor air quality which is essential for preventing the spread of the virus. Indoor air quality can be used to prevent the outbreak of influenza and respiratory infectious diseases. The air quality measurement provides scientific evidence as an important basis for improving indoor air quality, enhancing circulation, and reducing the risk of epidemic spread. In this project, we will start from the perspective of indoor air quality sensing by developing a miniature indoor air quality sensing device and strategically deploying the air sensing device for air quality detection. Next, we will be exploiting sensing results with real-time data analysis for environmental information and prediction of indoor air quality using machine learning techniques such as Support Vector Machine (SVM), Recurrent Neural Networks (RNN), or Long Short-Term Memory (LSTM) model. With the results of the analysis, we will design a series of information delivery platforms such as chat robots and visual interfaces to share with users. Also, we will develop smart remote IoT devices using the results of the analysis to control the active and passive air circulation equipment to improve the air circulation in the learning environments. By providing good indoor air quality, the project will be able to reduce the risk of respiratory infectious diseases and provide a safe learning environment in the era of respiratory infectious diseases.

 Development of Indoor Air Quality Monitoring System for Proactive Control of Respiratory Infectious Diseases

Tackle the disease surveillance problem by developing low-cost indoor air quality monitoring devices and strategic deployment with real-time data analysis

Jan. 2019 to Dec. 2021

Sponsored by Taiwan Center for Disease Control (CDC)

Grant Number: MOHW108-CDC-C-114-113701, MOHW109-CDC-C-114-123601, MOHW110-CDC-C-114-133501 

Disease surveillance is essential for the control of flu and respiratory infectious diseases including the novel coronavirus disease (COVID-19). Indoor air quality monitoring has been shown effective in understanding the effectiveness of airflow and circulation indoors to reduce the risk of infectious diseases. In this project, we developed low-cost indoor air quality monitoring devices and systems to tackle the disease surveillance problem. The monitoring device consists of a set of air quality sensors. By strategic deployment and real-time data analysis, the system is able to yield insightful air circulation information indoors. The real-time data analysis is performed on air quality for the indoor ventilation using Long Short-Term Memory (LSTM) on sensed data. A series of user-friendly visualization interfaces and chatbot applications are designed to interact with users and ensure the successful delivery of infection control information. Finally, we work closely with the Taiwan Centers for Disease Control (CDC) and conduct field experiments in 15 locations including hospitals, long-term care centers, schools with total of 144 IAQ devices.

[1] Yao-Hua Ho, Pei-En Li, Ling-Jyh Chen, and Yu-Lun Liu. 2020. Poster Abstract: Indoor Air Quality Monitoring System for Proactive Control of Respiratory Infectious Diseases. In Proceedings of The 18th ACM International Conference on Embedded Networked Sensor Systems (SenSys ‘20), Nov 16-19, 2020, Virtual Event, Japan.

 COVID-19 Pandemic Analysis for a Country’s Ability to Control the Outbreak Using Little’s Law: Infodemiology Approach

Since the outbreak of coronavirus disease (COVID-19), all countries across the globe have been trying to control its spread. A country’s ability to control the epidemic depends on how well its health system accommodates COVID-19 patients. In this research study, we aimed to assess the ability of different countries to contain the COVID-19 epidemic in real-time with the number of confirmed cases, deaths, and recovered cases. Using the dataset provided by the Humanitarian Data Exchange (HDX), we analyzed the spread of the virus from 22 January 2020 to 15 September 2020 and used Little’s Law to predict a country’s ability to control the epidemic. According to the average recovery time curve changes, 16 countries are divided into different categories—Outbreak, Under Control, Second Wave of Outbreak, and Premature Lockdown Lift. The curves of outbreak countries (i.e., U.S., Spain, Netherlands, Serbia, France, Sweden, and Belgium) showed an upward trend representing that their medical systems have been overloaded and are unable to provide effective medical services to patients. On the other hand, after the pandemic-prevention policy was applied, the average recovery time dropped in under-control countries (i.e., Iceland, New Zealand, Taiwan, Thailand, and Singapore). Finally, we study the impact of interventions on the average recovery time in some of the countries. The interventions, e.g., lockdown and gathering restrictions, show the effect after 14 days, which is the same as the incubation period of COVID-19. The results show that the average recovery time (T) can be used as an indicator of the ability to control the pandemic.

[1] Yao-Hua Ho, Yun-Juo Tai, and Ling-Jyh Chen. 2021. COVID-19 Pandemic Analysis for a Country’s Ability to Control the Outbreak Using Little’s Law: Infodemiology Approach. In Sustainability 2021. 13, no. 10: 5628 (Special Issue Big Data Analytics amid COVID-19: Toward Sustainable Society). https://doi.org/10.3390/su13105628

 Open Framework for Participatory PM2.5 Monitoring

As the population in cities continues to increase rapidly, air pollution becomes a serious issue from public health to social economy. Among all pollutants, fine particulate matters (PM2.5) directly related to various serious health concerns, e.g., lung cancer, premature death, asthma, and cardiovascular and respiratory diseases. To enhance the quality of urban living, sensors are deployed to create smart cities. In this research, we proposed a participatory urban sensing framework for PM2.5 monitoring [1] with more than 2500 devices deployed in Taiwan and 29 other countries. It is one of the largest deployment project for PM2.5 monitor in the world as we know until May 2017. The key feature of the framework is its open system architecture, which is based on the principles of open hardware, open source software, and open data. To facilitate the deployment of the framework, we investigate the accuracy issue of low-cost particle sensors with a comprehensive set of comparison evaluations [2] to identify the most reliable sensor. By working closely with government authorities, industry partners, and maker communities, we can construct an effective eco-system for participatory urban sensing of PM2.5 particles. Based on our deployment achievements to date, we provide a number of data services to improve environmental awareness, trigger on-demand responses, and assist future government policymaking. The proposed framework is highly scalable and sustainable with the potential to facilitate the Internet of Things, smart cities, and citizen science in the future.

[1] Ling-Jyh Chen, Yao-Hua Ho, Hu-Cheng Lee, Hsuan-Cho Wu, Hao-Min Liu, Hsin-Hung Hsieh, Yu-Te Huang, and Shih-Chun Candice Lung. An Open Framework for Participatory PM2.5 Monitoring in Smart Cities, IEEE Access, Volume 5, pp. 14441 - 14454, July, 2017. 

[2] Ling-Jyh Chen, Yao-Hua Ho, Hsin-Hung Hsieh, Shih-Ting Huang, Hu-Cheng Lee, and Sachit Mahajan. ADF: an Anomaly Detection Framework for Large-scale PM2.5 Sensing Systems, IEEE Internet of Things Journal, Oct. 2017. (Impact Factor 7.596, SCIE)

 On-demand Misbehavior Detection for Vehicular Network

Maintaining communication links of an established communication path that extends between the source and destination nodes is a significant challenge in Vehicular Ad Hoc Networks due to the movement of the vehicles. Operations of Vehicular Ad Hoc Network rely on the collaboration of participating nodes to route data for each other. A critical requirement for the nodes is to cooperate with each other for successful data transmission. Thus, the impact of malicious and selfish users must be detected to ensure the operations of the Vehicular Ad Hoc Network. In this research, we proposed the On-demand Misbehavior Detection technique [1] for vehicle-to-vehicle communication. We adapt two location-based routing protocols, Contention-Based Forwarding [2]and Connectionless Approach for Streets [3], to our On-demand Misbehavior Detection. Various experiments are conducted to show the effectiveness and efficiency of the proposed On-demand Misbehavior Detection technique. The simulation and analytical results showed that the proposed technique is very effective in detecting misbehaving nodes. The primary contributions of this article are as follows: (1) we introduce OMD for location-based routing protocols in VANET, (2) we apply the OMD method to two of location-based routing protocols, CBF and Connectionless Approach for Street (CLA-S), and (3) we present simulation and analytical results to show that OMD can successfully detect malicious nodes without false accusation to maintain the good performance of the network.

[1] Yao-Hua Ho, Chun-Han Lin, and Ling-Jyh Chen, On-Demand Misbehavior Detection (OMD) for VANET, International Journal of Distributed Sensor Networks (IJDSN) - SI on Towards Architectures and Applications of Mobile Wireless Sensor Networks, Sage, Volume 12, Issue 10, 2016.

[3] H. Fubler, J. Widmer, M. Kasemann, M. Mauve, and H. Hartenstein. Contention-based forwarding for mobile ad-hoc networks. Ad Hoc Netw 2003; 1(4): 351–369.

[4] Y. H. Ho, A. H. Ho, and K. A. Hua, et al. A connectionless approach to mobile ad hoc networks. In: Proceedings of the ninth international symposium on (ISCC) computers and communications, vol. 1, Alexandria, Egypt, 28 June–1 July 2004, pp.188–195. New York: IEEE.

 Assisting Search and Rescue Operations using Wi-Fi Signal with UAV

Natural disasters affect thousands of people every year.  In a large disaster area, search and rescue operations can face great difficulties to locate victims. According to the Annual Disaster Statistical Review 2013 [2], 330 natural disasters were registered and a significant number of people (21,610 - including a number of confirmed dead and missing) were killed. Estimated economic losses were US$ 156.7 billion. Hydrological disasters (i.e., floods, landslides, etc.) had still by far the largest share of 48.2% of natural disasters. Without any communication, it will not be easy for victims to call for help and report their locations.  Second, search and rescue operations can face great difficulties to find victims in a large disaster area.  Third, disaster areas are often unfriendly, inaccessible, or even dangerous for rescue teams. Unmanned Aerial Vehicles (UAVs) is a good option to provide support to search and rescue (SAR) operations with low operating cost, fast deployment, and agile maneuverability.  After Hurricane Katrina in 2005, two UAVs were used to search for survivors in the disaster area [3].  In fact, UAVs have been used to support SAR operations with image recognition for victim detection. However, victims are often buried or covered under debris or mud from the disaster that makes such vision-based SAR operations difficult. We proposed a system, called Krypto [1], which is carried by UAVs (e.g., quadcopter drones) to support SAR operations by detecting wireless signals from mobile phones.  Krypto is the name of Superdog from Superman comic books. Just like a search-and-rescue dog that smells scent from any humans, Krypto flies around the disaster area and sniffs out wireless signals from any mobile phone.  In particular, we use Wi-Fi signals from mobile phones to locate possible survivors.  The aim of Krypto is to support the search team to narrow down the search area within meters.

[1] Ho, Y-H, Chen, Y-R, and Chen, L-J. “Krypto: Assisting Search and Rescue Operations using Wi-Fi Signal with UAV” in ACM International Workshop on Micro Aerial Vehicle Networks, Systems, and Applications for Civilian Use (DroNet), Florence, Italy, 2015.

[2] Guha-Sapir, D., Hoyois, P., and Below, R. 2014. “Annual Disaster Statistical Review 2013: The Numbers and Trends,” Brussels: Centre for Research on Epidemiology of Disasters CRED. 

[5] National Science Foundation (NSF), 2005. Hurricane Katrina Small, Unmanned Aircraft Search for Survivors in Katrina Wreckage, http://www.nsf.gov/news/news_summ.jsp?cntn_id=104453 

[6] Yao H. Ho and Ling-Jyh Chen. “Enhancing Robustness of Vehicular Networks using Virtual Frameworks,” in Telecommunication System Journal (TSMJ) 2014 – SI: Critical Application in Vehicular Ad Hoc/Sensor Networks. 

[7] Yao H. Ho and William W.Y. Hsu. “Disaster Resilient Communication for Tunnels and Bridges,” in Workshop on Resilient ICT for Management of Mega Disasters (RITMAN conjunction with WoWMoM) Sydney, Australia, June 16, 2014.

[8] Yao H. Ho, “Enhancing Robustness of Wireless Mesh Networks using Virtual Routers,” in 12th International Conference on Intelligent Transportation Systems (ITS) Telecommunications (ITST), Taipei, Taiwan, Nov, 2012.

 Virtual Router (Connectionless) Approach to MANET and Vehicular Network

Many routing protocols have been proposed for Mobile Ad-Hoc Networks (MANETs) and Vehicular Networks (VNETs) that follow a connection-oriented approach.  By connection-oriented, we mean that mobile nodes need to establish a connection using either route discovery or a routing table before two mobile units can communicate. In practice, the mobility of some of the nodes can be high, causing frequent reconnections.  Such overhead wastes energy and causes discontinuity in communications.  The jitter effect is particularly undesirable for streaming applications such as voice and video.  Reducing the frequency of reconnections is a hard problem as it is an innate property of mobility beyond the control of any routing algorithm.  This fact has motivated us to avoid using any “fixed” connections at all.  In our proposed approach [1], [2], [3], [4], and [5] the network area is divided into small non-overlapping grid cells. Instead of maintaining a hop-by-hop route between the source and destination node, the source selects a list of grid cells that form a “connecting” path between the source and destination.  From a different perspective, each grid cell can be viewed as a virtual router in the sense that any physical router (i.e., a mobile node) currently within the virtual router can alternate in forwarding data toward the next virtual router.  The communication path consisting of consecutive virtual routers forms a virtual link. 

[1] Yao-Hua Ho. Routing Protocols in Vehicle-to-Vehicle Communication.  In F. Hu (Editor). Vehicle-to-Vehicle and Vehicle-to-Infrastructure Communications: A Technical Approach. Taylor & Francis LLC, CRC Press, May 2017.

[2] Yao H. Ho, Meng Chang Chen, and Han-Chieh Chao. “Congestion Avoidance Routing for MANETs,” in International Journal of Ad Hoc and Ubiquitous Computing 2014 – SI: Application-oriented Protocol Design for Wireless Ad Hoc Networks, Vol 16, Issue 1, June 2014. 

[3] Yao H. Ho, “Enhancing Robustness of Wireless Mesh Networks using Virtual Routers,” in 12th International Conference on Intelligent Transportation Systems (ITS) Telecommunications (ITST), Taipei, Taiwan, Nov, 2012. 

[4] Y.H. Ho, A.H. Ho, K.A. Hua, G.L. Hamza-Lup. “A Connectionless Approach to Mobile Ad hoc Networks,” in Proc. of Ninth International Symposium on Computers and Communications (ISCC), Vol 1, pp. 188-195, Alexandria, Egypt, 2004.

[5] Y. H. Ho, A. H. Ho, and K. A. Hua, “Connectionless Protocol – A Localized Scheme to Ad Hoc Network,” in Proceedings of International Journal of Ad Hoc and Ubiquitous Computing (IJAHUC) Vol. 2, Issue 1/2, pp. 21 – 35, 2007.

[6] Ai Hua Ho, Yao H. Ho, and Kien A. Hua. “Adapting Connectionless Approach to Ad-hoc Networks in Urban Environments,” in Proc. of International Conference on Wireless Network, Las Vegas, Nevada 2005.

 PLASH: a Platform for Location-Aware Service with Human Computation

Location-Aware Service (LAS) emerges as smart mobile devices and IP wireless networks (e.g., 3G and WiMax) become popular and ubiquitous. The major difference between PLASH [4] and other approaches [1][2][3][5][6][7] is that it emphasizes the support of volunteers and application providers. In PLASH, users can contribute their efforts and location-related data voluntarily; and LAS builders can use the PLASH framework and provided functions to deploy their applications easily. Moreover, with the support of PLASH, an ordinary user can easily share his personal LAS with other users. We design and build a platform that comprises three layers, namely Communication, Data, and Service Layer. Communication Layer supports various wireless communication (e.g., WLAN, WiMAX, and 3G) and networking contexts (e.g., Vehicle to Infrastructure, Vehicle to Vehicle, and Vehicle to Mobile device). Data Layer is for geo-location data representation, storage, access, and Service Layer provides various types of services to support PLASH applications. This layered architecture allows LAS application builders to conveniently create their systems by simply using API to access Service Layer or via an Application Specification Language (ASL) to build their systems. To demonstrate the capability of the PLASH platform, a number of LAS applications for Android, iPhone, and web browsers are built as a first attempt.

[1] T. Das, M. Mohan, V. Padmanaabhan, R. Ramjee, and A. Sharma. “PRISM: Platform for Remote Sensing using Smartphones,” in Proceeding 8th ACM MobiSys, San Fransciso, CA, USA, 2010.

[2] S. Ducasse, M. Rieger, S. Demeyer, “A language Independent Approach for Detecting Duplicated Code”, ICSM, 1999.

[3] Foursquare Web Site. http://foursquare.com/

[4] Yao Hua Ho, Yao Chuan Wu, and Meng Chang Chen. “PLASH: A Platform for Location Aware Service with Human Computation,” in IEEE Communication Magazine - Consumer Communications and Networking Series, December Issue, 2010.

[5] A. Hunt, and D. Thomas, The Pragmatic Programmer: From Journeyman to Master, Addison-Wesley, 2000.

[6] Spam Net Web Site. http://www.cloudmark.com

[7] Yu Zheng, Xing Xie, and Wei-Ying Ma. “GeoLife: A Collaborative Social Networking Service among User, location and trajectory,” in IEEE Data(base) Engineering Bulletin, June 2010.

 Failure-Resilient Wireless Mesh Network for Disaster Recovery

We have witnessed over the last few years many disasters in the globe. One thing that all of those natural disasters have in common, besides the tremendous loss of life, is that they are immediately followed by an almost total loss of the ability to communicate with the outside world. Wireless mesh network (WMN) is one of the best choices and is widely used for establishing communication networks during disaster recovery due to its scalability, flexibility, ease of setup, and maintenance. Due to unpredictable changes in the disaster area, the connectivity WMNs and the reliability of individual mesh nodes decreased rapidly. Using crow sourcing and human computing, mesh clients can participate in message forwarding and information/resource sharing. For power-efficient communication, messages (or data) are aggregated in an efficient way to reduce the number of the transmitted packet and to save the power of mobile devices. We proposed approaches [1][2]: Virtual Router Approach (VRA) and a Virtual Link Approach (VLA). In VRA, when a mesh node fails, a client can be connected to a remote mesh node through a virtual router. Similarly, a client can be connected to a remote mesh node through a virtual link in VLA. A virtual route is a sequence of connecting virtual routers. A virtual router is a logical router that is associated with a geographical area. This approach requires each mobile device to be equipped with a localization device such as GPS. In contrast, the VLA does not have this requirement. A virtual link is a communication path between a mobile node and a remote mesh node. The proposed techniques are able to retain 80% of the original capacity with only 50% working mesh nodes. We give simulation results, validated by analytical analysis, to show that this desirable property can be achieved, using virtual routers and/or virtual links, with minimal overhead. VRA and VLA also balance the workload among the mesh nodes even when the mesh clients are not uniformly distributed over the application terrain. This characteristic helps improve the overall end-to-end delay and communication throughput of the network. 

[1] Yao H. Ho and Ling-Jyh Chen. “Enhancing Robustness of Vehicular Networks using Virtual Frameworks,” in Telecommunication System Journal (TSMJ) 2013 – SI: Critical Application in Vehicular Ad Hoc/Sensor Networks.

[2] Yao H. Ho, “Enhancing Robustness of Wireless Mesh Networks using Virtual Routers,” in 12th International Conference on Intelligent Transportation Systems (ITS) Telecommunications (ITST), Taipei, Taiwan, Nov, 2012.

 Backup Grid System for Symantec Corporation

Various organizations face an explosive growth of data that must be protected and backup. This challenge is made more difficult by the movement from stand-alone server backup to backup over the local area network (LAN) and by the need to automatically manage multiple backup servers efficiently for concurrent backup jobs. We proposed a novel software approach [1] to backup service, where application servers provide their unused resource to participate in a virtual backup environment. This software approach offers organization a scalable, robust, efficient, and economical solution to doing backups and restores across a distributed organization. The contribution of this work is a new service-oriented framework for storage backup. This software approach offers organizations a scalable, robust, efficient, and economical solution to doing backups and restores across a distributed organization—whether one that has multiple servers in one campus or distributed among remote offices.

[1] Hao Cheng, Yao H. Ho, Kien A. Hua, Danzhou Liu, and Fei Xie, “A Software Approach to Storage Backup,” in IEEE International Conference on Service Computing: Industry Track 2008 on February 18, 2008.

[2] Ynn-Pyng Tsaur, Kien A. Hua, Hao Cheng, Yao Hua Ho, Danzhou Liu, and Fei Xie. Redirection of an Ongoing Backup, U.S. Patent. Patent No. US 7,890,714 B1. University of Central Florida and Symantec ® Join Research Project. 2/15/2011 

(http://www.freepatentsonline.com/7890714.pdf).