Fulu Li

• PhD
• Massachusetts Institute of Technology

We introduce community coding, where information systems meet social networks. Community coding is an emerging field of social computation and coding theory, which provides a method of aggregating resources from a community to maximize the sum of their utilities by allowing the community members to coordinate their contributions of resources. Commu...

We investigate the problem of image sensing under unfavorable photographic conditions in a wireless image sensor network. In the scenes with deflective and/or reflective medium such as fogs, mirrors, glasses, degraded images are captured by those image sensors. Such degraded images often lack perceptual vividness and they offer a poor visibility of...

With the availability of ever-increasing gene sequence data across a large number of species, reconstruction of phylogenetic trees to reveal the evolution relationship among those species becomes more and more important. In this paper, we present a novel proof of the NP-completeness of the large parsimony problem by reduction from a newly-proved NP...

Photo tourism [11] is a platform that allows users to transform unstructured online digital photos into a 3D experience. Nowadays, image sensors are being extensively used to allow images to be taken automatically and remotely, which facilitates the opportunity for live update of photo mosaics. In this paper, we present a novel framework for live p...

We investigate the problem of image sensing under unfavorable photographic conditions in a wireless image sensor network. In the scenes with deflective and/or reflective medium such as fogs, mirrors, glasses, degraded images are captured by those image sensors. Such degraded images often lack perceptual vividness and they offer a poor visibility of...

Although CDMA EVDO Rev. A provides significant improvements over EVDO Release 0 that make it well suited for VoIP-like applications [3], it remains unclear about its performance in terms of quantitative evaluations with different real implementation scenarios. To understand the system design tradeoffs, we first investigate the traffic characteristi...

With the availability of ever-increasing gene sequence data across a large number of species, reconstruction of phylogenetic trees to reveal the evolution relationship among those species becomes more and more important. In this paper, we focus on the construction of the most parsimonious phylogenetic trees given sequence data of a group of species...

Photo tourism [5] is a platform that allows users to transform unstructured online digital photos into a 3D experience. Nowadays, image sensors are being extensively used to allow images to be taken automatically and remotely, which facilitates the opportunity for live update of photo mosaics. In this paper, we present a novel framework for live ph...

In this paper we study the probabilistic view coverage problem for image sensing in wireless sensor networks. The view coverage of an image sensor network determines the quality of the surveillance services that an image sensor network can provide. In this paper, we present an indepth analysis on probabilistic view coverage in an image sensor netwo...

We study the routing problem in all-wireless networks based on cooperative transmissions. We model the minimum-energy cooperative path (MECP) problem and prove that this problem is NP-complete. We hence design an approximation algorithm called cooperative shortest path (CSP) algorithm that uses Dijkstra's algorithm as the basic building block and u...

In this paper, we present a networking perspective of cooperative spectrum sharing in wireless networks. For unlicensed band like WiFi, e.g., 2.4 GHz, it is particularly critical that network nodes share the same spectrum cooperatively and efficiently. We discuss several cooperative techniques for spectrum sharing in wireless networks including str...

Information storage and storage sharing are key components of modern networked computer systems. Mobile devices such as PDAs and cell phones normally have very limited storage capacities compared with PCs or laptops, while storing a large number of media objects (such as e-books, pictures and videos, etc.) on mobile devices could take a lot of spac...

Recent advancement in peer-to-peer (P2P) technologies has enabled a wide range of new applications. In this paper, we present mixed integer programming (MIP) formulations to analyze multiple interior-disjoint-tree-based and mesh-based P2P media streaming for application level multicast (ALM). Network optimization is the key to simultaneously satisf...

In this paper, we derive the formula to count broadcast trees based on the number of internal nodes in the tree. To the best of our knowledge, it is the first time that tree enumeration formulas based on the number of internal nodes in the tree have been explored and addressed. In addition, we give a new proof of Cayley's famous formula for countin...

Expanders are potential mathematic tools to design robust computer networks and to analyze the formation and expansion of today's Internet. In this paper, we derive lower bounds regarding the expansion rate of Margulis expanders, lower bounds and upper bounds regarding the expansion rate of LPS expanders, for vertex set Z times Z . The two types of...

Interference and energy-restriction are two of the most important technical challenges in the design of networking protocols in wireless ad hoc networks. The interference is an inherent problem for wireless communication and it is not easy to control. On the other hand, the lifetime of an ad hoc network totally relies on the power consumption of th...

Voice traffic is not efficiently supported by CDMA EVDO Rev. A from its original design, but an efficient approach is needed to support voice traffic over CDMA EVDO Rev. A for graceful migration from CDMA2000 1x to CDMA EVDO Rev. A as voice service revenue is still the dominant income source for cellular service providers. To understand the system...

Global flooding and expanding ring search are two commonly used methods in search for an interested object in multi-hop wireless networks. While global flooding is simple, it is not scalable for large networks. To take advantage of expanding ring search, a critical question must be answered: what is the best initial TTL (time-to-live) value for the...

In this paper, we present a network-aware source coding (NASC) approach for wireless broadcast channels with multiple sources. The proposed NSAC approach takes into account the information of the network topology during the source coding process and the cross-layer design approach may be beneficial for wireless networks. We derive the optimal bound...

Wireless communication has fundamental impairments due to multi-path fading, attenuation, reflections, obstructions, and noise. More importantly, it has historically been designed to mimic a physical wire; in concept other communicators in the same region are viewed as crossed wires. Many systems overcome these limitations by either speaking more l...

ABSTRCT We conducted an empirical study of the clustering behavior of spammers and explored the group-based anti-spam strategies. We propose to block spammers as groups instead of dealing with each spam individually. We empirically observe that, with a certain grouping criteria such as having the same URL in the spam mail, the relationship among th...

We study the routing problem for multi-hop wireless ad hoc networks based on cooperative transmission. We prove that the minimum energy cooperative path (MECP) routing problem, i.e., using cooperative radio transmission to find the best route with the minimum energy cost from a source node to a destination node, is NP-complete. We thus propose a co...

We study the problem of minimum energy cooperative path (MECP) routing in wireless networks. The joint problem of cooperative routing in wireless networks that combines route selection and the transmit diversity was recently presented in A. Khandani et al. (2003). Several heuristic algorithms were also proposed in A. Khandani et al. (2003) to appro...

Wireless sensor networks consist of a large number of tiny sensors that have only limited energy supply. One of the major challenges in constructing such networks is to main-tain long network lifetime as well as sufficient sensing areas. To achieve this goal, a broadly-used method is to turn off redundant sensors. In this paper, the problem of esti...

Wireless sensor networks consist of a large number of tiny sensors that have only limited energy supply. One of the major challenges in constructing such networks is to maintain long network lifetime as well as su#cient sensing area. To achieve this goal, a broadly-used method is to turn o# redundant sensors. In this paper, the problem of estimatin...

We study optimization methods for source-initiated energy-efficient broadcast in all-wireless networks. Past studies on energy-efficient broadcast (1,3,5) focus on deterministic optimization to construct an energy-efficient broadcast tree. We present a Random Tree Optimization (RTO) approach that transforms the deterministic optimization problem in...

Real-time, mission-critical applications in mobile ad hoc networks, e.g., wireless sensor networks, have been seen for military battlefield operations, emergency relief for terrorist attacks, patient condition-monitoring in medical systems. We study fault-tolerant and distributed network protocols that support reliable, energy-efficient broadcastin...

We study the construction of the source-initiated (one-to-all) wireless broadcast tree to minimize the total required power for a given source node, a group of intended destination nodes and a given propagation constant, ie, the power attenuation constant λ. The minimum energy broadcasting (MEB) problem has received much attention recently due to t...

The conventional wisdom has been that IP is the natural protocol layer for implementing multicast related functionality. However, ten years after its initial proposal, IP Multicast is still plagued with concerns pertaining to scalability, network management, ...

The IETF is currently focused on differentiated services (Diffserv) as the architecture to provide quality of service in IP networks (IP-QoS). The Diffserv architecture consists of two key components: traffic conditioning at the edge and per hop behaviour (PHB) at the core. Traffic conditioners are realized through various building blocks such as c...

Periodic broadcast schemes have been proposed as a scalable solution for the implementation of Video--on-- Demand (VoD) systems. Efficient periodic broadcast schemes fragment each video into a number of segments assuming that the videos are encoded using Constant Bit Rate (CBR) coders. We focus instead on the more efficient and commonplace class of...

Several proposals for video-on-demand (VoD) systems assume batching of the user requests and subsequent multicasting of the selected videos. We propose that the waiting time, which is essential for the sake of batching, can be overlapped with a more elaborate call admission scheme. The call admission scheme provides sufficient bandwidth at any poin...

We study peer–to–peer (P2P) multicast streaming protocols for high bandwidth streams to large numbers of heterogeneous and transient users. First, the shortcomings of tree–based P2P schemes are discussed. Subsequently, a scalable swarm–based scheme is introduced that avoids maintaining a rigid logical topology. Peers self–organize into an unstructu...

Periodic broadcast schemes have been proposed to solve the Media-on-Demand (MoD) distribution problem for the set of the most frequently requested media objects. Most of the current proposals for periodic broadcast schemes assume Constant-Bit-Rate (CBR) encoded media objects [1,2,5,9]. The few existing proposals for support of the bandwidth-efficie...

We have conducted an empirical study of the community behavior of spammers, which has revealed various clustering structures among their population. Based on those structures (discovered solely by processing sighted spam mail), we propose a family of new spam-blocking techniques exploiting group membership of perceived spam sources. In particular,...

Thesis (M.Sc.)--University of Alberta, 2000. Includes bibliographical references.