Chuan-Gang Liu

A multi-hop resource scheduling algorithm for IEEE 802.16j relay networks

Abstract The IEEE 802.16j standard defines both transparent and non-transparent relay transmission mode. The present study formulates and optimizes the relay resource scheduling problem for the case of a non-transparent relay network. It is shown that the resource scheduling problem is NP-Complete. A method is proposed for optimizing the position of the zone boundary adaptively during the resource scheduling process in order to maximize the system throughput. In addition, a low time complexity algorithm designated as MRRS (multi-hop relay resource scheduling) is proposed to obtain an approximate solution for the NP-Complete scheduling problem. In the proposed algorithm, the zone boundary is adjusted adaptively in accordance with the user distribution and the channel state information in such a way as to improve the utilization of the available slots. The simulation results show that MRRS achieves a higher throughput than existing relay resource scheduling algorithms (GenArgMax and Eliminate-Repeat) with no significant loss in fairness. In addition, it is shown that the performance improvement provided by MRRS increases as the hop-count is increased.

A Novel Group-Based Location Service Management Scheme in VANETs

—One of the major concerns in VANETs is to design a scalable and robust routing protocol, which usually depends on the ability of tracking the locations of vehicles in VANETs. The location information service in VANETs helps to find the destination vehicle effectively. However, vehicle mobility and lack of adequate location information management scheme for vehicles in large scale VANETs are the main challenges. In this paper we proposed a novel group-based location information service scheme that places Location Information Points on the roadside to provide up-to-date location information and resolve lookup query of vehicles in the network. Furthermore, our proposed scheme groups LIPs into hotspot or non-hotspot groups. Hotspot LIPs will construct a P2P overlay network which facilitates the resolution of the query message in VANETs. Comparing to previous schemes, our scheme can perform location update and reply to lookup query on each LIPs well with less communication overhead in large scale VANETs.

Improve TCP performance with a novel adaptive queue management scheme in IEEE 802.17 RPR optical networks

Resilient Packet Ring (RPR), a novel IEEE 802-series MAC scheme over optical network for Metropontan Area Networks (MAN), provides flexible data efficient delivery and optical transmission reliability. However, RPR fairness scheme causes TCP performance degradation. In this paper, an analytical traffic model is developed to study the impact of congestion control of TCP under RPR AM fairness scheme. Basically, two possible ways may be able to improve this impact, to equip a buffer to accommodate the burst or to employ a robust active queue management (AQM). However, buffer requirement in RPR networks may be different for various network scenarios and AQM scheme should be better for RPR networks. Furthermore, our study shows that TCP works not well if queue management parameters are fixed at a value. Hence, a novel adaptive queue management scheme with RPR feedback information is proposed. Available bandwidth for each ingress-aggregated flow should be passed to its upstream nodes in RPR MAC scheme. Accordingly, queue management design parameters could be adaptively tuned to achieve better queueing behavior. Through detailed simulations in various scenarios, our proposed schemes are able to improve TCP performance obviously.

Improving RPR fairness convergence

IEEE 802.17 RPR is a MAN candidate due to its ability to achieve fairness and fast restoration. However, the proposed fairness scheme may lead to slow convergence and permanent oscillation. This letter proposes a novel fast-convergent scheme to provide fairness using estimated number of unbounded flows in each link. After detailed evaluations and simulations, the proposed scheme is proven to allocate bandwidth fairly among flows fast-convergently and achieve high utilization at the same time

K-anonymity against neighborhood attacks in weighted social networks

Nowadays, with the advance of Internet technology, social network is getting popular, which combines the virtual network and the real world. People employ this network to communicate with all social things of their interest, including shopping, making friends, sharing experiences of life, and so on. In social networks, the social data expands rapidly and the malicious users can easily get the social data. With the social information, they could conjecture the relationship among social network data via the systematical analysis tool. Hence, the personal privacy data in social network may be exposed to some unknown risks, and recently, these issues arising in such a network catch much attention. The protection of personal privacy social data becomes an important and urgent research in social networks. One of personal privacy social information is the relations between the individuals and their social groups, namely human relationships.

Navigation-aware association control in vehicular wireless networks

Currently, internetworking over Wireless Vehicular Ad Hoc Networks VANET is getting more attention and discussion. Mobile devices, including smartphones, laptops and PDAs, associate with nearby access points that are located on the roadside to access Internet in VANETs. Hence, people can use these devices to communicate in VANETs. However, the unbalanced traffic distribution often occurs among the APs in the networks, which leads to unfair bandwidth share for each user. This situation may get worse in VANETs composed of thousands of high mobility vehicles. Hence, this study focuses on association control to achieve load balancing among APs RSUs, and we propose a novel association control algorithm with an aid of the navigation system. Based on the use of fully-fledged navigation system, our proposed algorithm plans a RSU-association-schedule, which selects a series of appropriate RSUs roadside units in advance to reach destination and meanwhile achieves load balancing among RSUs. The simulation results show that our scheme does improve the fairness and overall performance in VANETs.

Distributed Node Scheduling Algorithms for Multiple Group Communications in Wireless Multi-hop Networks

We study the scheduling problem in performing multiple multicast communications in wireless multi-hop networks, it is necessary to ensure that each multicast group can complete one transmission from the source to all the destination nodes without conflict in every frame. The present study proposes two distributed token-based STDMA node scheduling algorithms which not only satisfy this requirement, but also minimize the frame length. In the first algorithm, the multicast groups are scheduled on a group-by-group basis, whereas in the second algorithm, multiple groups are scheduled in each scheduling operation. The first algorithm has the advantages of computational simplicity and a straightforward implementation, while the second algorithm increases the percentage of reused time slots and reduces the number of token forwarding events. The simulation results show that both algorithms achieve a shorter frame length than existing methods.

Distributed Log System in Cloud Digital Forensics

Cloud computing in recent years has become very popular and, indeed, many current applications are served from the cloud. Because the cloud architecture is based on virtual machines, VMs and VM management are quite important. Monitoring a large number of virtual machines is an important research topic. Since the establishment of the Personal Information Protection Act, there has been more attention focused on cloud security. Among cloud security topics, log analysis allows insight into virtual machine operation. If there are incidents, they need to be reported instantly in order to maintain information security. Consequently, log collection and real time warning systems are necessary. In this paper, we propose a distributed management architecture and evaluate its system performance. We also discuss the effects on the system due to bandwidth and background traffic ratios, VM numbers and transmission time using a set of simulations. The results show the proposed architecture not only saves time, but also reduces the load of log transmission for monitoring cloud services.

Achieving multipoint-to-multipoint fairness with RCNWA

In current Internet, applications employ lots of sessions with multiple connections between multiple senders and receivers. Sessions or users with more connections gain higher throughput. To obtain more network resource, applications tend to create more connections. It causes unfair bandwidth allocation by per-connection TCP rate allocation and the network suffers lots of TCP overheads. In this paper, we explore the issue on fair share allocation of bandwidth among sessions or users. Various fairness definitions are discussed in this study. Then, we propose a novel distributed scheme to achieve various fairness definitions. Simulation results show that our distributed scheme could achieve fair allocation according to each fairness definition.