Weijing Qi

A Unified Routing Framework for Integrated Space/Air Information Networks

The aerospace-based communications can be managed more efficiently through the construction of an integrated space/air information network by the convergence of satellite (space) and unmanned aerial vehicle (air) networks. Such an integrated network would best fit the advent of delay- and disruption-tolerant networking, in which the data transmission can tolerate long delay and disruption under a store-carry-forward mechanism. Such a network, however, has some challenging research needs due to the networks high mobility of nodes and time-varying topology that may result in high error bit rate and long delay. In this paper, we propose a unified routing framework for this integrated network, where a Hybrid time-space Graph supporting Hierarchical Routing (HGHR) algorithm is achieved. More specifically, the HGHR performs on a hybrid time-space graph, including two subgraphs: a deterministic graph for the space network and a semi-deterministic one for the air network. This latter graph is based on a discrete time homogeneous semi-Markov prediction model. The hybrid time-space graph is then transformed into a state-space graph, based on which, a message forwarding rule under the store-carry-forward mechanism is adopted. Simulation results show that the proposed HGHR algorithm has good performance in terms of message delivery ratio, end-to-end delay, and power consumption.

Virtual concatenation-based elastic network embedding for inter-cloud-data-center networks

The elastic optical network (EON) provides fine-grained and orthogonal spectrum slots for the establishment of the elastic connection using orthogonal frequency division multiplexing (OFDM). Currently, the EON interconnection has realized the high-rate transmission among data centers (DCs). With the implementation of cloud DCs (CDCs) and EON virtualization, it becomes very essential to achieve the elastic network embedding (ENE) that facilitates the resource sharing in inter-cloud-data-center networks. The ENE operation consists of two components, the virtual-node mapping from virtual machine to CDC and the virtual-link (VL) mapping from virtual lightpath to fiber link(s). Thus an ENE request can be satisfied only when those two mapping processes have completed successfully. But during the VL mapping, some rigid constraints must be satisfied, such as the spectrum continuity, etc. This makes the ENE operation create the spectrum fragments over fiber links, which results in the denial of requests. Thus in this paper, we take the virtual concatenation (VC) into account when the VL mapping fails. The problem is formulated using the relaxed integer linear programming (ILP) model, and we also design a VC-based heuristic. Simulation results have verified the superiorities of the VC scheme on increasing the spectrum utilization and reducing the blocking rate of ENE requests.

Trajectory Data Mining-Based Routing in DTN-Enabled Vehicular Ad Hoc Networks

A delay/disruption tolerant network (DTN) architecture where a “store-carry-forward” strategy is adopted for data transmissions can be utilized in vehicular ad hoc networks (VANETs). The key point of routing in DTN-enabled VANETs is to choose the best node and determine the best time to forward messages. Time-space graph models provide an idea of converting the dynamic routing problems into static ones in deterministic DTNs. But it is a challenge to predict vehicles’ future positions in order to obtain the time-space graph. In this paper, to achieve the cost-efficient and reliable routing in DTN-enabled VANETs, a novel timeliness-aware trajectory data mining algorithm is proposed to predict nodes’ future positions. A sparse time-space graph is then obtained, based on which, two routing heuristics are proposed. Simulation results demonstrate that our proposed routing algorithms ensure low cost and high reliability over time.

Topology Control and Routing Based on Adaptive RF/FSO Switching in Space-Air Integrated Networks

To make full use of space/air resources, a Space-Air Integrated Network (SAIN) which is a hierarchical network with satellites, airships and hovering Unmanned Aerial Vehicles (UAVs) is constructed. Nowadays, Free Space Optical (FSO) links have been widely applied in SAINs since they provide high-rate and large-capacity data transmission. Unfortunately, the FSO links across the atmosphere would perform badly in adverse weather. Besides, the limited number of transceivers brings bottlenecks of link capacity and node energy. To solve these problems, in this paper, we first propose an adaptive RF/FSO switching mechanism based on predictions of atmosphere conditions, so that the high- rate and large-capacity data transmission can be achieved while overcoming the negative influences of bad weathers. Moreover, under the limited number of transceivers, we design a Dynamic Energy \& Traffic Balance (DETB) topology control algorithm. Except for transmit power, both residual bandwidth and energy are taken into account for obtaining an optimal topology dynamically. Finally, a hierarchical routing policy combined with our DETB algorithm is proposed. It has been proved that our method extends the network lifetime, and the network throughput remains stable.

A traffic-differentiated routing algorithm in Flying Ad Hoc Sensor Networks with SDN cluster controllers

Abstract Recently, Flying Ad-hoc Sensor Networks (FASNETs), which are basically ad hoc networks between Unmanned Aerial Vehicles (UAVs), have been playing a great role in many sensing fields. To further improve the utilization of network resources, researchers offer the possibility of applying Software Defined Networking (SDN) technology to FASNETs, enabling various applications to be supported over the same platform. Since these concurrently executed applications might have diverse Quality of Service (QoS) requirements, it brings new challenges to network management and resource scheduling. In this paper, we propose a novel clustering FASNET architecture with SDN cluster controllers and also a collaborative controller, in order to realize hierarchical management and unified dispatch. Based on our designed architecture, we also propose a centralized traffic-differentiated routing (TDR) executed in each cluster, which aims to guarantee the specific QoS requirements of delay-sensitive and reliability-requisite services. Different weights are assigned to various flows according to their sensitivity to delay and also levels of importance. In particular, we introduce a transmission reliability prediction model to TDR, in which we consider both link availability and node’s forwarding ability. Simulation results show our proposed TDR has good performances in terms of end-to-end delay, packet dropping ratio and network throughput.

Maintenance and bandwidth scheduling for cloud rendering in optical data center networks

Animation rendering aims to transform a digital design into a vivid cartoon. To achieve a high-quality animation in the short term, the cloud rendering was presented through consolidating Data Center (DC) resources. Since DCs are far away from each other due to the space limitation, the cloud rendering will run over the Optical Data Center Network (ODCN) where DCs are interconnected by high-speed optical links. This high-speed interconnection well supports the fast data migration for the DC maintenance, which is a preventive measure for safeguarding the uptime of cloud rendering. In this paper, to achieve the least batch maintenance scheduling, multiple DCs are maintained simultaneously through one batch, which makes Rendering Processes (RPs) migrated among DCs via high-speed optical links, and brings the extra costs such as the link-bandwidth consumption. Thus, after performing the least batch maintenance using the heuristic, we determine the bandwidth provisioning for the optical links along a migration trajectory. Simulation results demonstrate the effectiveness of our method.

Novel routing algorithms in space information networks based on timeliness-aware data mining and time-space graph

Space information network is a kind of delay-tolerant networks. Recently, with possible participation of many network nodes, maintaining efficient and dynamic topology becomes crucial. In space information networks, the underlying topology is lack of continuous connectivity, and has the drawbacks of network segmentation, long delay and unreliable connections, which makes the routing design face severe challenges. In this paper, we propose novel routing schemes for space information networks. To construct a semi-deterministic time-space graph model, the timeliness-aware data mining algorithm is introduced to predict the contact probability for each pair of nodes. Using this time-space graph model, we put forward a simplified topology for achieving the reliable and cost-efficient routing. Simulation results demonstrate that the proposed routing algorithms can ensure the connectivity and reliability of paths over time, but also significantly reduce the total link overhead.

Hierarchical Routing for Integrated Space/Air Information Networks

An integrated space/air information network is a convergence of satellite communication networks in space regions and aircraft communication networks in air regions. It supports direct internal information interactions. Along with the extensive application of the integrated space/air information network especially in military fields, its routing problem becomes a key point of research. However, the existing routing algorithms are mainly designed for the space or air region separately and there is little study on the generalized routing for the integrated space/air information network. In this paper, we propose a Hybrid time-space Graph based Hierarchical Routing (HGHR) scheme for this integrated network. The hybrid time-space graph includes two subgraphs: a deterministic one and a semi-deterministic one. As satellite orbits are pre- known in the space region, we introduce a deterministic time-space subgraph. While each aircraft has a cyclic movement with the predictable contact probability and contact time in the air region, we construct a semi-deterministic time-space subgraph according to the prediction results of a discrete time homogeneous semi-Markov model. Simulation results show that HGHR has good performance in terms of data delivery ratio and end- to-end delay.