Shaobin Cai

Research of localization algorithm based on weighted Voronoi diagrams for wireless sensor network

Wireless sensor network (WSN) is formed by a large number of cheap sensors, which are communicated by an ad hoc wireless network to collect information of sensed objects of a certain area. The acquired information is useful only when the locations of sensors and objects are known. Therefore, localization is one of the most important technologies of WSN. In this paper, weighted Voronoi diagram-based localization scheme (W-VBLS) is proposed to extend Voronoi diagram-based localization scheme (VBLS). In this scheme, firstly, a node estimates the distances according to the strength of its received signal strength indicator (RSSI) from neighbor beacons and divides three beacons into groups, whose distances are similar. Secondly, by a triangle, formed by the node and two beacons of a group, a weighted bisector can be calculated out. Thirdly, an estimated position of the node with the biggest RSSI value as weight can be calculated out by three bisectors of the same group. Finally, the position of the node is calculated out by the weighted average of all estimated positions. The simulation shows that compared with centroid and VBLS, W-VBLS has higher positioning accuracy and lower computation complexity.

Network Coding Based Schemes for Imperfect Wireless Packet Retransmission Problems: A Divide and Conquer Approach

NC (Network Coding) provides a new approach to packet retransmission problems in wireless networks, which are named as WPRTPs (Wireless Packet Retransmission Problems) in this paper. Some research has been conducted on P-WPRTPs (Perfect WPRTPs) where, for one receiver, a packet is either being requested by or already known to it. However, very few efforts are focused on IP-WPRTPs (Imperfect WPRTPs) where, for one receiver, a packet can be neither requested by nor already known to it. In this paper, we focus on IP-WPRTPs. Firstly, a WPRTP reduction theorem for simplifying WPRTPs is proposed and proved. Then, the upper and lower bounds of the number of necessary packet transmissions in optimal NC-based solutions to IP-WPRTPs are analyzed. Next, a scheme named as IP-WPRTP-DC (Divide and Conquer based scheme for IP-WPRTPs) is proposed based on the WPRTP reduction theorem using a divide and conquer approach. Extensive simulations show that the IP-WPRTP-DC scheme is effective in saving the number of packet transmissions for solving IP-WPRTPs.

Tree-Mesh Based P2P Streaming Data Distribution Scheme

This paper presents the design of a novel P2P live streaming policy, tree-mesh based P2P Streaming Data Distribution Scheme(TMDS). Both the tree-based and the mesh-based structures have respective flaws while distributing the media data. The tree-based structure is highly vulnerable, so it is very suitable for the stable environment in small scale. And the mesh-based structure is quite stable, and can guarantee certain grade of service under the large-scale environment, but its costs of control are bigger, and also creates heavy load to the network. However TMDS can effectively solve these problems, and take advantage of their merits. Confirmed in the simulated environment, TMDS can: improve the quality of service; decrease the costs of system control, lighten the burden on the network; relieve the load on the transmitting end, enhance the stability of the system.

The Nonlinear Network Coding and Its Application in Error-Correcting Codes

Nonlinear network coding is researched here. For determined network, Jaggi–Sanders algorithm is generalized to its nonlinear form for the the multicast network. Precise details of the algorithm implementation and the proof on the algorithm existence are given. The error-correcting codes for determined network coding is also proposed based on the traditional error-correcting codes for network coding. For random network, the nonlinear network coding scheme is proposed. It shows the nonlinear network coding has advantages in solving the so-called “all-or-nothing” problem caused by errors. Some interesting mathematical concepts such as shared agreements, composite functions and n-dimensional maximal independent set based on combinatorics are proposed. These new concepts may offer beneficial lessons for further research on nonlinear network coding.

Random network coding-based optimal scheme for perfect wireless packet retransmission problems

Solving wireless packet retransmission problems (WPRTPs) using network coding (NC) approach is increasingly attracting research efforts. However, existing researches are almost all focused on solutions in Galois field GF(2), and consequently, the solutions found by these schemes are usually less optimal. In this paper, we focus on optimal NC-based scheme for perfect WPRTPs (P-WPRTPs) where, with respect to each receiver, a packet is either requested by or already known to it. The number of retransmitted packets in optimal NC-based solutions to P-WPRTPs is firstly analyzed and proved. Then, random network coding-based optimal scheme (RNCOPT) is proposed for P-WRPTPs. RNCOPT is optimal in the sense that it guarantees to obtain a valid solution with minimum number of packet retransmissions. Furthermore, in RNCOPT, each coding vector is generated using a publicly known pseudorandom function with a randomly selected seed. The seed, instead of the coding vector, is used as decoding information to be retransmitted together with the coded packet. Thus, packet overhead of RNCOPT is reduced further. Extensive simulations show that RNCOPT distinctively outperforms some previous typical schemes for P-WPRTPs in saving the number of retransmitted packets. Copyright

An improved RED algorithm with combined of queue length and sending-rate inspection

This paper presents an improved algebraic pruning method for point projection for Bezier curves. It first turns the point projection into a root finding problem, and provides a simple but easily overlooked method to avoid finding invalid roots which is obviously irrelative to the closest point. The continued fraction method and its expansion are utilized to strengthen its robustness. Since NURBS curves can be easily turned into Bezier form, the new method also works with NURBS curves. Examples are presented to illustrate the efficiency and robustness of the new method.The main purpose of active queue management is to provide congestion information so that sources can set their rates. In this paper, we consider an algorithm which can achieve high utilization as well as a low queuing delay and loss, regardless of the number of sources. This is done by matching the source rate to the network capacity and stabilizing the queue lengths around target values. Based on load level prediction we proposed an asynchronous control mechanism combine with the queue-based and rate-based to make better performance trade-off.

Group-Based Key Management for Multicast of Ad Hoc Sensor Network

In order to protect communication security among sensor nodes, a cryptographic method are needed by ad hoc sensor networks. According to that most ad hoc sensor networks are deployed in groups, a group-based multicast key management scheme is proposed to extend RPS scheme in this paper. Compared with RPS, our scheme improves the probability that a shared key exists between two sensor nodes, and reduce the probability that the shared key is decrypted.

A Fault Detection Service for Cluster-Based Ad Hoc Network

Ad Hoc Network becomes widely used for many specific fields. In case of frequently happened node failures and message losses, in order to expedite the development of applications, we propose a middleware service for the failure detection to support these applications. Based on the hierarchical-based and Gossip-based detection techniques, a fault detection service for cluster-based Ad Hoc Network integrating the proposed adaptive fault detector is proposed. Simulations show that the proposed detection service achieves a preferable system performance.

Modified Improved Alternating Combination Trilateration Algorithm with a Variable m

In most applications of wireless sensor network, the acquired information is useful only when their locations are known. Compared with ACT (alternating combination trilateration), IACT (improved alternating combination trilateration) has reduced its calculation overhead greatly. In IACT, The value of m, which determines how many triangles are used in calculations, is static. In this paper, the value of m is studied further, and a modified improved alternating combination trilateration is proposed. The simulation results show that its calculation can be reduced further when m is defined according to the number of anchor nodes.

Practical Privacy-Preserving Outsourcing of Large-Scale Matrix Determinant Computation in the Cloud

Jaggi-Sanders algorithm is generalized to its nonlinear form for multicast network. Precise details of the algorithm implementation and the proof on the algorithm existence are given. It may has meaningful significance in the two following aspects. First, it may offer a thinking for the urgent need to find a nonlinear coding scheme for non-multicast network some of which can not be coded by linear coding. Second, some interesting mathematical concepts such as shared agreements, composite functions and n-dimensional maximal independent set (nMIS) based on combinatorics are proposed. These new concepts may offer beneficial lessons for further research on nonlinear network coding.