Tian He

Professor, ACM and IEEE Fellow
Department of Computer Science and Engineering
Affiliate with Digital Technology Center
ate faculty in Electrical and Computer Engineering
University of Minnesota
4-205 EE/CSci Building
200 Union Street SE Minneapolis, MN 55455

Email: tianhe at cs.umn.edu
Office: (612) 626-1281  Fax: (612) 625-0572

Current Research Directions

  • WIRELESS:  Wireless Coexistence [Project Site]

  • WEARABLES:  Posture/behavior estimation, social interaction monitoring [Project Site]

  • CPS: Large-Scale Intelligent Transportation Systems (road network efficiency and safety) [Project Site]

  • ENERGY: Rechargeable Sensor Systems/Battery Array Management/Safe charging

Current Ph.D. Students

CS. Fall 2010
CS, Fall 2011
CS, Fall 2012
CS, Fall 2014
CS, Fall 2014
CS, Fall 2015

Ph.D. Graduates

PhD, CS, Assistant Professor at Singapore University of Technology and Design (now IBM Research)
PhD, CS, Assistant Professor at University of Nebraska Lincoln  (now TI)
PhD, CS, Assistant Professor at SUNY Binghamton (now University of Maryland Baltimore County)
PhD, CS, Assistant Professor at City University of Hong Kong
CS, Assistant Professor at Sungkyunkwan University
PhD, CS, Intel Security
PhD. ECE, Arista Networks
ECE, Assistant Professor at University of Wisconsin - Stout
PhD, ECE, Lemko Corporation

Master Graduates

Master, Oracle
Master, Amazon Inc
Master, LSI corporation

Visiting Scholars/PostDocs
Welcome to apply if you are largely self-funded. Please email tianhe@cs.umn.edu

  • Jiawei Huang
  • Mengfan Shan
  • XiaoLei Zhou
  • Anas Basalamah
  • Pengpeng Chen
  • Liangyin Chen
  • Shigemi Ishida
  • Zixi Jia
  • Naigao Jin
  • Xingfa Shen
  • Fulong Xu
Associate Professor, Central South University
Visiting Ph.D. student, Nanjing University
Visiting Ph.D. student, NUDT
Assistant Professor, Umm Al Qura University
Assistant Professor, China University of Mining and Technology
Associate Professor, Sichuan University
Assistant Professor, ISEE, Kyushu University
Assistant Professor, Northeastern University
Associate Professor, Dalian University of Technology
Associate Professor, Hangzhou Dianzi University
Research Scientist, UESTC

Selected Research Projects

TaxiBox consists of three main parts: central control system, onboard sensing system, and external devices.  With various onboard sensors, a dispatching center is capable of monitoring the comprehensive physical status of a taxicab on streets. Various external devices can be integrated into our Taxi- Box. Some external devices in the current TaxiBox design include (i) a display and a speaker integrated to the display; (ii) a traditional fare meter for fare calculation and receipt printing; (iii) backup power for a situation in which the main power is not available; (iv) an emergency button; (v) a GPS module with a separate GPS antenna; and (vi) a CDMA 1X communication module with a separate antenna.  This design and usage of this device has been reported in  MobiCom 13, BIGDATA 203, SENSYS 2012 and SenSys 2013  [PDF ]. [Data Source]
Carpooling has long held the promise of reducing gas consumption by decreasing mileage to deliver co-riders. In this work, we present  coRide  in a large-scale taxicab network intended to reduce total mileage for less gas consumption. Our coRide system consists of three components, a dispatching cloud server, passenger clients, and an onboard customized TaxiBox device. In the coRide design, in response to the delivery requests of passengers, dispatching cloud servers calculate cost-efficient carpool routes (Ratio-2 optimal) for taxicab drivers and thus lower fares for the individual passengers. We evaluate coRide with a real world dataset of more than 14,000 taxi- cabs, and the results show that compared with the ground truth, our service can reduce 33% of total mileage; This system has been reported in SenSys 2013  [PDF ].
To understand how environments impact wireless communication, researchers have studied extensively on the packet reception quality of individual wireless links in real-world environments. In contrast, little research has been done to investigate the reception correlation of wireless links and its related impact on network-layer performance, despite the fact that wireless communication essentially occurs in a broadcast medium with concurrent receptions. To address this gap, we propose an in-depth systematic study to cover a large design space from empirical measurement, modeling, and impact analysis to design and implementation of protocols that exploit spatiotemporal patterns of link pathcorrelation. The inital work has been reported in NSDI 2010 and MobiCom 2013
eShare supports the concept of energy sharing among multiple devices by providing designs for energy routers (i.e., energy storage and routing devices) and related energy access and network protocols. In a nutshell, energy routers exchange energy sharing control information using their data network while sharing energy freely among connected devices using their energy network. We extensively evaluate our system under six real-world settings and the result has been reported in ACM SenSys 2010 [PDF].
TwinStar is built upon recent breakthrough in energy storage using ultra-capacitors. We uniquely  feature a battery-less node design with a combination of solar cells and ultra-capacitors, which can store tens of thousands more energy than traditional capacitors. One of main challenging problems is to efficiently utilize the energy in the presence of  large leakage current exhibited in such capacitors. Our objective is to guarantee aliveness of sensor nodes between two consecutive recharging cycles using leakage-aware feedback control. With SSN nodes available, many long-term sensor network applications, such as bridge monitoring,  can be practically supported. This system has been reported in MobiSys 2009. [PDF]
In road networks, wireless sensors are deployed along the road ways for surveillance. This project proposes a virtual scanning algorithm, called VISA. We consider the surveillance scenario that entrance points on road map are specified as possible vehicle entrances and protection points are specified as important points before which vehicles should be detected. We guarantee the detection of moving vehicles entering entrance points of label E on the road network before they reach protection points of label P. Our objective is to maximize the lifetime of the sensor network deployed on the road network, satisfying such a detection guarantee. We construct a virtual graph composed of vertices and edges where the vertices are road intersections, protection points and entrance points and the edges are distances along with the number of sensors deployed on the road segments. This virtual graph is used to determine each sensor's duty cycle consisting of the working schedule and sleeping schedule. We evaluate our design outdoor in Minnesota roadways and show the detection guarantee despite of some sensing holes due to the absence of sensors. This system has been reported in Infocom 2009. [PDF]

In road networks, sensor nodes are deployed sparsely (hundreds of meters apart) to save costs. This makes the existing localization solutions based on the ranging ineffective. To address this issue, we introduce an Autonomous Passive Localization (APL) scheme. Our work is inspired by the fact that vehicles move along routes with a known map. Using vehicle-detection timestamps, we can obtain distance estimates between any pair of sensors on roadways to construct a virtual graph composed of sensor identifications (i.e., vertices) and distance estimates (i.e., edges). The virtual graph is then matched with the topology of road map, in order to identify where sensors are located in roadways. We evaluate our design in local roadways and simulated environments, where we found no location matching error, even with a maximum sensor time synchronization error of 0.3sec and the vehicle speed deviation of 10km/h..

This system has been reported in Infocom 2008. [PDF]

TinyCasper proposes two in-network distributed algorithms, namely Minimum Resource and Optimal Area that aim to preserve personal privacy in such areas while maintaining the monitoring functionality. Both algorithms reply on the well established privacy concept of k-anonymity; Although both proposed algorithms provide same privacy guarantees, the Minimum Resource aims to do so with minimum possible number of exchanged messages between sensor nodes while the Optimal Area algorithm aims to maintain the highest quality of monitoring functionality. Furthermore, to accommodate the system users mobility, we propose an incremental maintenance scheme for both algorithms that aims to avoid redundant reevaluation of privacy guarantees. The proposed system is evaluated with a network of 39 MICAz motes on a physical test-bed, and an extensive simulation of 1,000 sensor nodes. [Demo Video]

Mirage is a large indoor sensor network test-bed, supporting up to 360 nodes. The whole test-bed is composed of six 4 feet by 8 feet boards. Each board in the system can be used as an individual sub-system, because each board is designed to be separately powered, separately controlled and separately  metered. Each individual board can support up to 60 nodes, therefore, the whole system can support up to 360 nodes working simultaneously. In the first phase of construction,  three high-end HIT HITCPX1250 projectors are used to generate event  (it is capable to create mirage ). In the second phase of construction,  motorize objects are introduced to create another sets of mobile targets. The ultimate goal of this testbed is to allow researchers to conduct all kinds of system research locally and remotely with realistic sensing modality as inputs. The first phase of construction is finished during 2007. In the second phase, mobility support will be added.

Multi-Sequence Positioning (MSP) is designed and implemented for sensor node localization in outdoor environments.  The novel idea behind MSP is to reconstruct and estimate two-dimensional (or 3D) location information for each sensor node by processing multiple easy-to-get one-dimensional node sequences obtained through a loosely guided event distribution. We have realized the MSP idea through two physical systems (indoor and outdoor version) with totally over 60 MICAZ motes. This evaluation demonstrates that MSP can achieve sub-feet-level accuracy, requiring neither additional hardware on sensor nodes nor precise event distribution. It also provides a nice tradeoff between physical costs (anchors) with soft cost (events) while maintaining localization accuracy.[Demo Video]

This system has been reported in SenSys 2007. [PDF ]

Despite the well-known fact that in reality sensing patterns are highly irregular, researchers continue to develop protocols with simplifying assumptions of circular 0/1 sensing models. In this project, we design and implement two Sensing Area Modeling (SAM) techniques useful in the real world. P-SAM provides accurate sensing area models for individual nodes using controlled or monitored events, while V-SAM provides continuous sensing similarity models using natural events in an environment.  Evaluation under real-world settings reveal several serious issues concerning circular models, and demonstrate significant improvements in several applications when SAM is used.

This system has been reported in SenSys 2007. [PDF ]

uSense defines a Unified Sensing Coverage Architecture, which features three novel ideas: Asymmetric Architecture, Generic Switching and Global Scheduling. uSense provides sensing coverage through a creative separation of scheduling from switching. We design and implement sophisticated scheduling algorithms externally and represent such intelligence with a lightweight generic switching algorithm running at resource-constrained sensor nodes. As an instance of these scheduling algorithms, we propose a novel two-level scheduling algorithm, called uScan. We evaluate our architecture with a network of 30 MicaZ motes, an extensive simulation with 10,000 nodes. The results indicate that uSense is a promising architecture to support flexible and efficient coverage in sensor networks.  

This system has been reported in ICDCS 2007  [PDF ] and MobiCom SRC competition 2006

 In this project, we design and test a methodology for navigation of mobile wireless sensor networks and fast target acquisition without a map, called GraDrive. Our approach integrates per-node prediction with global collaborative prediction to estimate the position of a stationary target and to direct mobile nodes towards the target along the shortest path. We demonstrate that a high accuracy in localization can be achieved much faster than existing navigation models without any assistance from stationary sensor networks.

This system won the best paper award in the 2nd International Conference on Mobile Ad-hoc and Sensor Networks (MSN 2006) [PDF ]

In this project  we design and implement a framework, called StarDust, for wireless sensor network localization based on passive optical components. In the StarDust framework, sensor nodes are equipped with optical retro-reflectors. An aerial device projects light towards the deployed sensor network, and records an image of the reflected light. An image processing algorithm is developed for obtaining the locations of sensor nodes. For matching a node ID to a location we propose a constraint-based label relaxation algorithm. We propose and develop localization techniques based on four types of constraints: node color, neighbor information, deployment time for a node and deployment location for a node.

This system has been reported in SenSys06 [PDF ]

Spotlight uses the spatio-temporal properties of well controlled events in the network (e.g., light), to obtain the locations of sensor nodes. We demonstrate that a high accuracy in localization can be achieved without the aid of expensive hardware on the sensor nodes, as required by other localization systems. Through performance evaluations of a real system deployed outdoors, we obtain a 20cm localization error. A sensor network, with any number of nodes, deployed in a 2500m2 area, can be localized in under 10 minutes, using a device that costs less than $1000. To the best of our knowledge, this is the first report of a sub-meter localization error, obtained in an outdoor environment, without equipping the wireless sensor nodes with specialized ranging hardware.

This system has been reported in SenSys05 [PDF ][Demo Video]

Vigilnet is one of the major efforts in the sensor network community to build an integrated sensor network system for surveillance missions. The focus of this effort is to acquire and verify information about capabilities and positions of targets. Such missions often involve a high element of risk for human personnel and require a high degree of stealthiness. Hence, the ability to deploy unmanned surveillance missions, by using wireless sensor networks, is of great practical importance. In this work, we design and implement a complete running system, called VigilNet,  for energy-efficient surveillance.  It currently consists about 40,000 lines of NesC and Java code, running on XSM, Mica2 and Mica2dot platforms. The complete system is designed to scale to at least 1000 XSM motes and cover minimal 100x1000 square meters to ensure operational applicability. We evaluate middleware and system performance extensively on a network of 203 MICA2 motes.  

Various aspects of the VigilNet system have been reported in MobiSys04 [PDF], SenSys05 [PDF] , Infocom05 [PDF], RTAS06 and TECS [PDF]


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