Hongjie Du

Efficient Algorithms for Topology Control Problem with Routing Cost Constraints in Wireless Networks

Topology control is one vital factor to a wireless networks efficiency. A Connected Dominating Set (CDS) can be a useful basis of a backbone topology construction. In this paper, a special CDS, named α Minimum routing Cost CDS (α-MOC-CDS), will be studied to improve the performance of CDS based broadcasting and routing. In this paper, we prove that construction of a minimum α-MOC-CDS is NP-hard in a general graph and we propose a heuristic algorithm for construction of α-MOC-CDS.

Efficient Virtual Backbone Construction with Routing Cost Constraint in Wireless Networks Using Directional Antennas

Directional antennas can divide the transmission range into several sectors. Thus, through switching off sectors in unnecessary directions in wireless networks, we can save bandwidth and energy consumption. In this paper, we will study a directional virtual backbone (VB) in the network where directional antennas are used. When constructing a VB, we will take routing and broadcasting into account since they are two common operations in wireless networks. Hence, we will study a VB with guaranteed routing costs, named α Minimum rOuting Cost Directional VB (α-MOC-DVB). Besides the properties of regular VBs, α-MOC-DVB also has a special constraint - for any pair of nodes, there exists at least one path all intermediate directions on which must belong to α-MOC-DVB and the number of intermediate directions on the path is smaller than α times that on the shortest path. We prove that construction of a minimum α-MOC-DVB is an NP-hard problem in a general directed graph. A heuristic algorithm is proposed and theoretical analysis is also discussed in the paper. Extensive simulations demonstrate that our α-MOC-DVB is much more efficient in the sense of VB size and routing costs compared to other VBs.

Construction of directional virtual backbones with minimum routing cost in wireless networks

It is well-known that the application of directional antennas can help conserve bandwidth and energy consumption in wireless networks. Thus, to achieve efficiency in wireless networks, we study a special virtual backbone (VB) using directional antennas, requiring that from one node to any other node in the network, there exists at least one directional shortest path all of whose intermediate directions should belong to the VB, named as Minimum rOuting Cost Directional VB (MOC-DVB). In addition, VB has been well studied in Unit Disk Graph (UDG). However, radio wave based communications in wireless networks may be interrupted by obstacles (e.g., buildings and mountains). Thus, in this paper, we model a network as a general directed graph. We prove that construction of a minimum MOC-DVB is an NP-hard problem in a general directed graph and in term of the size of MOC-DVB, there exists an unreachable lower bound of the polynomial-time selected MOC-DVB. Therefore, we propose a distributed approximation algorithm for constructing MOC-DVB with approximation ratio of 1 + lnK + 2lnδD, where K is the number of antennas on each node and δD is the maximum direction degree in the network. Extensive simulations demonstrate that our constructed MOC-DVB is much more efficient in the sense of MOC-DVB size and routing cost compared to other VBs.

Constructing weakly connected dominating set for secure clustering in distributed sensor network

Secure clustering problem plays an important role in distributed sensor networks. Weakly Connected Dominating Set (WCDS) is used for solving this problem. Therefore, computing a minimum WCDS becomes an important topic of this research. In this paper, we compare the size of Maximal Independent Set (MIS) and minimum WCDS in unit disk graph. Our analysis shows that five is the least upper bound for this ratio. We also present a distributed algorithm to produce a weakly connected MIS within a factor 5 from the minimum WCDS.

Two constructions of new error-correcting pooling designs from orthogonal spaces over a finite field of characteristic 2

AbstractIn this paper, we construct two classes of t×n,se-disjunct matrix with subspaces in orthogonal space

Connected Dominating Set in Wireless Networks

\mathbb{F}_{q}^{(2\nu+1)}

On minimum submodular cover with submodular cost

of characteristic 2 and exhibit their disjunct properties. We also prove that the test efficiency t/n of constructions II is smaller than that of D’yachkov et al. (J. Comput. Biol. 12:1129–1136, 2005).

Security and Privacy in Online Social Networks: Optimization Perspectives

In a graph G D .V;E/, a subset C of vertices is called a Connected Dominating Set if every vertex is either in C or adjacent to a vertex in C , and in addition the subgraph induced by C is connected. Given a graph, finding the minimum Connected Dominating Set is a classical combinatorial optimization problem, existing in literature for a long time. Due to wide applications of the minimum Connected Dominating Set in wireless networks, Connected Dominating Sets attract many recent research efforts. In this chapter, those developments are surveyed.

An efficient approximation for minimum energy broadcast in multi-channel multi-hop wireless network with directional antennas

In this paper, we show that a minimum non-submodular cover problem can be reduced into a problem of minimum submodular cover with submodular cost. In addition, we present an application in wireless sensor networks.

New algebraic constructions for pooling design in DNA library screening

Recently, Online Social Networks (OSNs) becomes one of the most remarkable technologies in the twenty-first century since it has been extraordinarily popular with over 200 million users. Security and privacy problems are the most important issues in OSNs. In this chapter, we introduced the optimization of security and privacy problems in OSNs. We characterized three existing works with different targets to give a view of this problem.