Yong Ren

Energy-aware weighted graph based dynamic topology control algorithm

In this paper a new energy-aware weighted dynamic topology control (WDTC) algorithm is proposed to extend the lifetime of wireless network and balance the nodes’ energy consumption. The idea is that each node builds its local minimum spanning tree (MST) based on the energy-aware weighted graph and the network topology is adjusted accordingly. It was proved theoretically that the topology under WDTC algorithm could preserve the network connectivity and a sufficient condition for the degree of no more than 6 was also given. Simulation shows that WDTC algorithm can effectively prolong the network lifetime and has good topological features.

A DHT and MDP-based mobility management scheme for large-scale mobile internet

Scalable mobility support is an important task in large-scale mobile Internet. A considerable amount of research on distributed hash table (DHT) based mobility support schemes, which are highly user scalable and load balanced, has been done. However these schemes have shortcomings in query and update performances and network scalability. It is because although routing of overlay itself is effective, there is inconsistency between logical and physical topologies, so the actual physical network performances are not necessarily efficient. In this article, while modeling the overlay mapping query to a Markov decision process (MDP), we define the reward function combining physical layer information with application layer information. Then we present a Markov decision routing (MDR) algorithm, which improves backward induction to get the global optimal strategy, and can balance the complexity of the time and space.We propose a DHT and MDR-based mobility management (DMDRMM) scheme. The numerical results show that the scheme inherits the advantages of the DHT-based management structure, and optimizes the update and query performances of dDHT especially for large-scale network.

An Index Structure Framework to Analyze Host Mobility Supports for Integrated Networks

Convergence is a key design aspect for next generation networks. Developing a general mobility management model is an important requirement for the integrated mobile networks. This paper begins with a survey of mobility management concept. Based on the analysis and comparison, we present a conceptual explanation of mobility management layer for mobility and its management. An index structure framework to analyze host mobility supports for integrated mobile networks is proposed in this paper. Our framework investigates the previous methods for mobility model analysis, and builds a general model to characterize and unify different mobility management schemes into an index structure. In our model, we construct the basic elements of management mechanisms, i.e. node and edge, and define the main operations, namely, update operation and query operation. At the same time, the fundamental performance metrics and the expressions of the cost functions is obtained. The proposed framework is flexible in its elements and parameters, and could be applied for many scenarios. We demonstrate the utility of our framework by evaluating various host mobility support schemes.

A DHT-based fast handover management scheme for mobile identifier/locator separation networks

Several researches propose the identifier/locator separation architecture to tackle the scaling problems of today’s Internet routing and addressing system. And scalable and seamless mobility support is an important task in mobile identifier/locator separation networks. In this paper, by analyzing the features, such as direct separation, flexible mapping and identifier replacement, we show that the new architecture delivers data packets more efficiently and protects location privacy better than traditional mobile IP networks, and is able to implement soft handover conveniently. Then we present a distributed Hash table (DHT) based fast handover management (DFHM) scheme for the new architecture, which improves the reactive handover mode of FMIPv6 and eliminates the duplicate address detection (DAD) and return routability (RR) processes in MIPv6. And we propose a generic analysis framework for handover management. Further, we demonstrate the validity of our framework by simulation and quantificationally study the effects of network scale and movement velocity. The results show that DFHM has good scalability and low handover latency, and has great advantages in the signaling cost and fast mobility support.

Phase transition and 1/f noise in a computer network model

Using a simple cellular automaton model of data packets transport in the Internet, the travel times of data packets and transport rates of routers along a fixed path are studied. In this model the additive increasing of transport rates, extraneous random interferences and finite capacity of router are considered. Changing the mean injecting rate of data packets, numerical simulation results show that there exists free flow and congested phase characterized by the different power spectrum of the travel times and the transport rates. While the power spectrum of both the travel times and the transport rates show 1/f noise (power law) in the free flow, the power spectrum of the travel times is approximately characterized by 1/f noise at low frequencies and white noise at high frequencies, and that of transport rates of routers only by white noise in the congested phase. These results are in agreement with previous experimental data.

A topology control algorithm based on D-region fault tolerance

In a wireless network, node failure due to either natural disasters or human intervention can cause network partitioning and other communication problems. For this reason, a wireless network should be fault tolerant. At present, most researchers use k-connectivity to measure fault tolerance, which requires the network to be connected after the failure of any up to k-1 nodes. However, wireless network node failures are usually spatially related, and particularly in military applications, nodes from the same limited area can fail together. As a metric of fault-tolerance, k-connectivity fails to capture the spatial relativity of faults and hardly satisfies the fault tolerance requirements of a wireless network design. In this paper, a new metric of fault-tolerance, termed D-region fault tolerance, is introduced to measure wireless network fault tolerance. A D-region fault tolerant network means that even after all the nodes have failed in a circular region with diameter D, it still remains connected. Based on D-region fault tolerance, we propose two fault-tolerant topology control algorithms—the global region fault tolerance algorithm (GRFT) and the localized region fault tolerance algorithm (LRFT). It is theoretically proven that both algorithms are able to generate a network with D-region fault tolerance. Simulation results indicate that with the same fault tolerance capabilities, networks based on both GRFT and LRFT algorithms have a lower transmission radius and lower logical degree.

Topology control algorithm using fault-tolerant 1-spanner for wireless ad hoc networks

A fault-tolerant 1-spanner is used to preserve all the minimum energy paths after node failures to cope with fault-tolerant topology control problems in wireless ad hoc networks. A fault-tolerant 1-spanner is a graph such that the remaining graph after node failures will not only remain connected, but also have a stretch factor of one. The fault-tolerant 1-spanner is used in a localized and distributed topology control al- gorithm, named the k-Fault-Tolerant 1-Spanner (k-FT1S), where each node constructs a minimum energy path tree for every local failed node set. This paper proves that the topology constructed by k-FT1S is a k-fault-tolerant 1-spanner that can tolerate up to k node failures, such that the remaining network after node failures preserves all the minimum energy paths of the remaining network gained from the initial network by removing the same failed nodes. Simulations show that the remaining network after removal of any k nodes still has the optimal energy efficiency and is competitive in terms of average logical degree, average physi- cal degree, and average transmission radius.

File-Sharing Preference in a Peer-to-Peer Network

Peer-to-peer network describes a typical complex network upon which users connect together according to their sharing preference, indicated by the resources they shared. In this article, we apply analytic methods from complex networks theory to investigate the sharing preference of users as well as the correlations between different resource categories in a real peer-to-peer file sharing system, which is helpful for getting more insight into rapid development of peer-to-peer network applications.

Hierarchical DHT and proportional replication based mobility management for large-scale mobile Internet ✩

Abstract A considerable amount of research on distributed hash table (DHT) based mobility support schemes, which are highly user scalable and load balanced, has been done. But these schemes have shortcomings in query performances and network scalability. It is because although routing of overlay is effective, there is inconsistency between logical and physical topologies, so the actual physical network performances are not necessarily efficient. In this paper, we introduce a replication technology based DHT-based mobility support. Then all queries from any subnet can get responses as early as possible, i.e.,xa0the query distances are reduced, and the scopes of the effect of topological inconsistency are limited. We investigate the effect of the number of mapping replicas on query performances for DHT-based mobility support. And we find that replicating mobile nodes’ mappings in proportion to their call-mobility-rates minimizes the query delay and ensures fairness in the query load distribution. Moreover, we combine the hierarchical structure with the domain-level DHT-based (dDHT) structure, to reduce the expense of replication on update performances. We propose a hierarchical DHT and proportional replication based mobility management (HDPRMM) scheme. The numerical results show HDPRMM optimizes the query and update performances of dDHT, and achieves better fairness and network scalability than MIP and dDHT.

Localized fault-tolerant spanner based topology control in wireless networks

As a metric of fault-tolerance, k-connectivity fails to consider the energy-efficiency of the remaining network after node failures. Fault-tolerant spanner considers both energy-efficiency and fault-tolerance problems of the network. A fault-tolerant spanner has a fault-tolerant stretch factor bounded by a predetermined real number, which guarantees that the remaining network is high energy-efficient after node failures. In this paper, we use fault-tolerant spanner to measure the network fault-tolerance and propose an approach to transform a spanner into a fault-tolerant spanner. Based on the approach, we propose a k-fault-tolerant t-spanner (k-FTtS) topology control algorithm. k-FTtS is localized and the topology under it has following properties: 1) it has (k+1)-connectivity; 2) it has a bounded stretch factor after the failure of up to k nodes. Simulation results show that k-FTtS is an effective algorithm to construct fault-tolerant spanners in wireless networks and also performs well in logical degree, physical degree and transmission radius.