Yuebin Bai

Link availability prediction-based reliable routing for mobile ad hoc networks

Mobile ad hoc networks (MANETs) are becoming increasingly important. The most challenging issue in conjunction with MANETs is reliable routing, that is, the procedure that determines the trajectory of packets travelling over the network. The authors present a novel link availability-based routing protocol (LBRP) for MANETs. Compared with other routing protocols, LBRP takes unpredictable topology change and frequent link failure into account. Meanwhile, by a rough estimation of the distance between two adjacent nodes, the proposed approach is able to accurately predict link availability over a short period of time. Simulation results are given to verify the approach. This study could serve as groundwork for further MANET research, including analysing and optimising other network protocols. Reliable routing protocol can effectively improve the availability and reliability of upper layer services and quality of service.

An Energy Optimization Protocol Based on Cross-Layer for Wireless Sensor Networks

Survivability is one of the critical issues and the most important research topics in the fields of wireless sensor networks (WSNs). Energy efficiency is one of the determining factors for survivability and lifetime of WSNs. In the WSNs, severe energy issue necessitates energy-efficient approach to fulfill application objectives. In this paper, we propose an Energy Optimization Approach based on Cross-Layer for Wireless Sensor Networks named as EOA, which consider the joint optimal design of the physical, medium access control (MAC), and routing layer. The focus of EOA is on the computation of optimal transmission power, routing, and duty-cycle schedule that optimize the WSNs energy-efficiency. We first propose a feedback algorithm that computes the proper transmission power level between nodes. Then, routing protocol can make use of the transmission power as a metric by choosing route with optimal power consumption to forward packets. Finally, the cross-layer routing information is exploited to form a duty-cycle schedule in MAC layer. EOA is validated on a CROSSBOW’s MicaZ mote platform, and evaluated using the TOSSIM simulator, the simulation results show that EOA is an energy-efficient approach and able to achieve significant performance improvement as well.

Performance Evaluation of Parallel Programming in Virtual Machine Environment

As multi-core processors become increasingly mainstream, architects have likewise become more interested in how best to make use of the computing capacity of the CPU, for instance, through multiple simultaneous threads or processes of execution with OpenMP or MPI. At the same time, the increasingly mature and prevailing virtualization technique in server consolidation and HPC promotes the emergence of a large number of virtual SMP servers. Therefore, whether the parallel program can run in the virtual machine environment efficiently or not is a topic of concern. In this paper, we investigate the performance of three typical parallel programming paradigms, including OpenMP, MPI, and Hybrid of OpenMP and MPI in the popular, open-source, Xen virtualization system. The results show that the performance of the traditional parallel program in Xen VMs is close to it in native, non-virtualized environment, if there is little communication or synchronization between threads or processes. In most cases, without excessive IO access, we can get an ideal speedup in a SMP VM or virtual cluster, which is close to linearity when the total virtual CPUs (vCPUs) number is not larger than the number of Physical CPUs (pCPUs). And the pure MPI implementation shows the best scalability and stability in virtual machine environment compared with the other two paradigms.

Task-aware based co-scheduling for virtual machine system

Today, virtualization technique is increasingly mature and prevalent in server consolidation and HPC. Virtual machine monitor plays a significant role in the resource management by dynamically mapping the virtual CPUs of virtual machines to physical CPUs according to chosen scheduling policy. However, since a virtual machine monitor lacks the insight into each virtual machine, the unpredictability of each workload makes effective resource allocation difficult. Particularly, current virtual machine scheduling policy has a critical impact on the performance of concurrent workload due to the non-synchronization of virtual CPUs. This paper presents a task-aware co-scheduling scheduler for virtual machine system. The task-aware mechanism is based on inference techniques using gray-box knowledge which can infer the concurrency and synchronization of guest OS level tasks. With this inference, proposed scheduler schedules the designated virtual machine to make it possible that corresponding virtual CPUs in this virtual machine can run on the physical CPUs synchronously in order to reduce the cost of synchronization between processes or threads. All implementation is confined to the virtualization layer based on Xen virtual machine monitor and the Credit scheduler. We evaluated our prototype in terms of synchronization performance and CPU fairness over synthetic mixed workloads and realistic applications. The experiment results indicate that task-aware based co-scheduling policy is feasible to improve the performance of virtual machine system for concurrent tasks.

Affinity-Aware Dynamic Pinning Scheduling for Virtual Machines

Virtualization provides an effective management in server consolidation. The transparence enables different kinds of servers running in the same platform, making full use of hardware resource. However, virtualization introduces two-level schedulers: one from Guest OS, where the tasks are scheduled to virtual CPUs (VCPUs), the other from the virtual machine monitor (VMM), where VCPUs are scheduled to CPUs. As a result, the lower level scheduler is ignorant of the task information so that it cannot allocate appropriate proportion of CPU resource for every Guest OS in some cases. This paper presents an affinity-aware Dynamic Pinning Scheduling scheduler (DP-Scheduling). We aim at two objects: Bridging the semantic gap between Guest OS and VMM, introducing an affinity-aware method and providing the tasks information about CPU affinity to VMM, Bringing up a novel scheduling, DP-Scheduling, so that VCPU can be pinned or unpinned on one CPU¡¯s running queue dynamically. For this purpose, we first get the Machine Address (MA) of process descriptor from the angle of VMM. The affinity information is also acquired before the task is enabled to run. To acknowledge the affinity information, DP-Scheduling calls an API provided by us. Depending on the affinity information, we put forward a series of measures to implement pinning dynamically as well as to keep workload balance. All implementation is confined to Xen VMM and Credit scheduler. Our experiments demonstrate that DP-Scheduling outperforms Credit scheduling by testing various indicators for CPU-bound tasks, without interfering the load balance.

Link Availability Prediction in Ad Hoc Networks

Since mobility may cause radio links to break frequently, one pivotal issue for routing in mobile ad hoc networks is how to select a reliable path that can last longer. Several metrics have been proposed in previous literatures, including link persistence, link duration, link availability, link residual time, and their path equivalents. In this paper, we present a novel algorithm for predicting continuous link availability between two mobile ad hoc nodes. By a rough estimation of the distance between two nodes, our approach is able to accurately predict link availability over a short period of time. Simulation results are given to verify our approach. This study could serve as groundwork for further ad hoc network researches including analyzing and optimizing other network protocols.

FCCM: A Novel Inter-Core Communication Mechanism in Multi-Core Platform

With the increasing number of cores integrated on a single chip, inter-core communication becomes more important in how to effectively support applications on multi-core platform. In this paper, we analyse the characteristics of multi-core tasks and classify processor cores into two categories based on their different functions: control core and computing core. According to the classification, we design a novel inter-core communication mechanism which includes three communication paths. With these paths, we can improve the utilization of multi-core by migrating the I/O part of applications from computing core to control core. Experiment results have proved the efficiency of them.

FAST: Fuzzy Decision-Based Resource Admission Control Mechanism for MANETs

Mobile Ad Hoc Networks (MANETs) have inherently dynamic topologies and heterogeneous network environments. Due to the distributed, multi-hop nature of these networks, as well as limited network resource, wireless capacity and random mobility of nodes, Quality of Service (QoS) provisioning faces severe challenges, especially in multicast scenarios. Resource admission control is one of the most effective methods for resource utilization and QoS guaranteed. In this paper, we combine resource admission control technologies and intelligent methods, propose a fuzzy decision-based resource admission control mechanism for MANETs (FAST), which can fast respond to dynamic topology changes and unstable link status. FAST also supports multicast and destination heterogeneity. Users can choose multiple evaluation parameters with different weights of services in fuzzy decision. Simulation results have proved the efficiency of the mechanism.

Adaptive Routing Based on Bayesian Network and Fuzzy Decision Algorithm in Delay-Tolerant Network

The topology of delay-tolerant network (DTN) changes frequently. The whole network is disconnected and there exists no end-to-end path for messages. We need a kind of mechanism called store-carry-forward to overcome this fault in DTN. However, traditional end-to-end routing protocols do not meet this requirements. Researchers developed many kinds of DTN routing protocols and different routing protocol fits different application characteristics. Because of the variable application characteristics, we should choose suitable routing protocols according to application requirements. For example, if the current traffic is heavy or the size of the message is too big, we should use routing protocols with small copy number, if the transmission is emergent, we should use routing protocols with short delay. This paper proposes the concept of adaptive routing, meaning choosing routing protocols based on application characteristics in DTN. We develop an adaptive routing scheme according to particular requirements, history network information and current network conditions in network scenarios and validate that with adaptive routing scheme the network performances improve a lot in many aspects, such as delay, overhead and delivery through simulations.

A high performance inter-domain communication approach for virtual machines

Highlights? Presented a novel inter-domain communication approach (IVCOM) for virtual machine. ? Using bypassing protocol stacks, shunning page flipping methods. ? IVCOM applies a direct communication channel between domain 0 and U. ? IVOCM can improve the latency and throughput in para-virtualized environment. ? IVCOM can greatly reduce the VM entry/exit operations. In virtualization technology field, researches mainly focus on strengthening the isolation barrier between virtual machines (VMs) that are co-resident within a single physical machine. At the same time, there are many kinds of distributed communication-intensive applications such as web services, transaction processing, graphics rendering and high performance grid applications, which need to communicate with other virtual machines at the same platform. Unfortunately, current inter-VM communication method cannot adequately satisfy the requirement of such applications. In this paper, we present the design and implementation of a high performance inter-VM communication method called IVCOM based on Xen virtual machine environment. In para-virtualization, IVCOM achieves high performance by bypassing some protocol stacks and privileged domain, shunning page flipping and providing a direct and high-performance communication path between VMs residing in the same physical machine. But in full-virtualization, IVCOM applies a direct communication channel between domain 0 and Hardware Virtualization based VM (HV2M) and can greatly reduce the VM entry/exit operations, which has improved the HV2M performance. In the evaluation of para-virtualization consisting of a few of benchmarks, we observe that IVCOM can reduce the inter-VM round trip latency by 70% and increase throughput by up to 3 times, which prove the efficiency of IVCOM in para-virtualized environment. In the full-virtualized one, IVCOM can reduce 90% VMX transition operations in the communication between domain 0 and HV2M.