Yujia Zhai

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.

Impacts of Internal Network Contexts on Performance of MANET Routing Protocols: A Case Study

Performance of Mobile Ad hoc Network (MANET)routing protocols is greatly affected by network contexts. The network contexts actually contain external and internal parts. However, there is relatively little research on the internal part. In this paper, we discuss the impacts of internal network contexts on routing protocol performance. First, a conceptual model is proposed to separate internal network contexts from external ones. Then we do a case study for Ad hoc On-demand Distance Vector (AODV) routing protocol. The parameter TTL_INCREMENT, which is involved in the broadcast of Route Request (RREQ) messages, is chosen as the typical internal parameter. The simulation shows, for varied values of TTL_INCREMENT, the results of performance comparisons between AODV and Optimized Link State Routing Protocol (OLSR) may be opposite. The rate of performance change with node density also shows relativity with TTL_INCREMENT. Further, based on simplified external network contexts, the relationship between TTL_INCREMENT and the overhead performance metric is proved quantitatively.

A Terrain-Awareness Based Mobility Model with Markov Random Disturbance for Tactical MANET

Terrain factors may have significant impacts on the dynamic characteristics of mobile nodes, especially in tactical MANET. However, most of the existing mobility models are probability models, which do not catch real tactical feature behaviors such as random disturbance and bypass processes. In this work, we establish a formalized process model to imitate the impact of small-scale terrain factors on the movement of nodes. In the model, we use a linear time invariant system to generate a colored noise with first-order Markov property, as a tiny random disturbance in the acceleration. Furthermore, we propose a terrain-awareness based bypass strategy to enable the nodes to perceive and bypass the area of obstacles. This strategy imitates the reaction of nodes when the nodes face large-scale terrain factors such as lakes and hills. The mobility traces show that our model realistically presents the impacts of terrain factors on the mobility of nodes. And parameters in our process model can be configured flexibly for different tactical scenarios.

An Index Structure Model for Mobility Management of Integrated Mobile IP 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 IP 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 model is proposed to characterize mobility management schemes. 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. The fundamental performance metrics and the expressions of the cost functions is obtained. We indicate that the proposed model is flexible in its elements and parameters, and could be applied for many scenarios.