Shumao Ou

On effective offloading services for resource-constrained mobile devices running heavier mobile Internet applications

Rapid advances in wireless mobile network technologies and mobile handsets (MHs) facilitate ubiquitous infrastructure that can support a range of mobile services and applications in addition to conventional mobile Internet access. One recent trend is to effectively run desktop PC-oriented heavier applications on MHs. However, due to their miniature, portable size, MHs are resource-constrained and therefore, running these applications directly on an MH is not satisfactory given a users expectations. To cope with this problem, this article proposes a novel offloading service that can seamlessly offload some of the tasks of a mobile application from an MH to nearby, resource-rich PCs (called surrogates). The system architecture and key components of the proposed offloading service are presented, prototyped, and evaluated. The results of experiments and simulations have demonstrated the effectiveness and efficiency of this offloading service for mobile applications.

Convergence of ethernet PON and IEEE 802.16 broadband access networks and its QoS-aware dynamic bandwidth allocation scheme

IEEE 802.16 and Ethernet Passive Optical Network (EPON) are two promising broadband access technologies for high-capacity wireless access networks and wired access networks, respectively. They each can be deployed to facilitate connection between the end users and the Internet but each of them suffers from some drawbacks if operating separately. To combine the bandwidth advantage of optical networks with the mobility feature of wireless communications, we propose a convergence of EPON and 802.16 networks in this paper. First, this paper starts with presenting the converged network architecture and especially the concept of virtual ONU-BS (VOB). Then, it identifies some unique research issues in this converged network. Second, the paper investigates a dynamic bandwidth allocation (DBA) scheme and its closely associated research issues. This DBA scheme takes into consideration the specific features of the converged network to enable a smooth data transmission across optical and wireless networks, and an end-to-end differentiated service to user traffics of diverse QoS (Quality of Service) requirements. This QoS-aware DBA scheme supports bandwidth fairness at the VOB level and class-of-service fairness at the 802.16 subscriber station level. The simulation results show that the proposed DBA scheme operates effectively and efficiently in terms of network throughput, average/maximum delay, resource utilization, service differentiation, etc.

A Multihop Peer-Communication Protocol With Fairness Guarantee for IEEE 802.16-Based Vehicular Networks

Wireless-communication technology can be used to improve road safety and to provide Internet access inside vehicles. This paper proposes a cross-layer protocol called coordinated external peer communication (CEPEC) for Internet-access services and peer communications for vehicular networks. We assume that IEEE 802.16 base stations (BS) are installed along highways and that the same air interface is equipped in vehicles. Certain vehicles locating outside of the limited coverage of their nearest BSs can still get access to the Internet via a multihop route to their BSs. For Internet-access services, the objective of CEPEC is to increase the end-to-end throughput while providing a fairness guarantee in bandwidth usage among road segments. To achieve this goal, the road is logically partitioned into segments of equal length. A relaying head is selected in each segment that performs both local-packet collecting and aggregated packets relaying. The simulation results have shown that the proposed CEPEC protocol provides higher throughput with guaranteed fairness in multihop data delivery in vehicular networks when compared with the purely IEEE 802.16-based protocol.

An effective offloading middleware for pervasive services on mobile devices

The practical success of pervasive services running in mobile wireless networks and devices relies on their ability to provide effective and efficient offloading support, so as to satisfy the increasing demand for mobile devices to run heavier applications (e.g. those running on desktop PCs). Offloading is an effective mechanism for leveraging the severity of resource constrained mobile devices by migrating some computing load to nearby resource-rich surrogates (e.g. desktop PCs, servers) on home networks or their extension. This paper proposes a light-weight and efficient offloading middleware, which provides runtime offloading services for resource constrained mobile devices. The middleware considers multiple types of resources (i.e. memory, CPU and bandwidth) and carries out application partitioning and partition offloading in an adaptive and efficient manner. The corresponding algorithms are presented. The evaluation outcomes indicate the effectiveness and efficiency of this service offloading solution.

An adaptive multi-constraint partitioning algorithm for offloading in pervasive systems

Offloading is a kind of mechanism utilized in pervasive systems to leverage the severity of resource constraints of mobile devices by migrating part of the classes of a pervasive service/application to some resource-rich nearby surrogates. A pervasive service application needs to be partitioned prior to offloading. Such partitioning algorithms play a critical role in a high-performance offloading system. This paper proposes an adaptive (k+1) partitioning algorithm that partitions a given application into 1 unoffloadable partition and k offloadable partitions. Furthermore, these partitions satisfy the multiple constraints imposed by either application users or mobile device resources. Underpinning the partitioning algorithm is a dynamic multi-cost graph that models the costs of an application in terms of its component classes (including CPU cost, memory cost and communication cost), and a Heavy-Edge and Light-Vertex Matching (HELVM) algorithm to coarsen the multi-cost graph. An offloading toolkit implementing the above algorithms has been developed, upon which the evaluations are carried out. The outcomes of the evaluation have indicated a higher level of performance of our algorithm in terms of its efficiency and cost-effectiveness

A model driven integration architecture for ontology-based context modelling and context-aware application development

Context-awareness is a very important feature for pervasive services to enhance their flexibility and adaptability to changing conditions and dynamic environments. Using ontologies to model context information and to reason about context at a semantic level has attracted a lot of interest in the research community. However, most of the proposed solutions are ad hoc or proprietary. Therefore, employing standard approaches to formulate the development process becomes of importance. In this paper we examine how OMGs Model Driven Architecture (MDA) can be applied to tackle the issues of context modelling and Context-Aware Application (CAA) modelling and development. A Context Ontology Model (COM) is presented to model context information at two levels: upper-level and extended specific level. A Model Driven Integration Architecture (MDIA) is then proposed to integrate rigorous model specifications and generate CAA implementations either semi-automatically or automatically.

Performance Analysis of Offloading Systems in Mobile Wireless Environments

Offloading is an approach to leverage the severity of resource constrained nature of mobile devices (such as PDAs, mobile phones) by migrating part of the computation of applications to some nearby resource-rich surrogates (e.g., desktop PCs, mobility support stations). It is an essential mechanism for the execution of pervasive services. However, the mobile nature of mobile devices and the unstable connectivity of wireless links all render a less predictability of the performance of a pervasive service running under the control of offloading systems. This paper proposes an analytical model to express the performance of offloading systems in mobile wireless environments. We investigate the surrogate unreachability when mobile devices move following random waypoint (RWP) mobility scheme. We model the failure recovery time and total execution time of pervasive applications that run under the control of offloading systems. Detailed evaluation and analysis results are reported and the results of this paper can be used as design guidance for pervasive service offloading systems.

Integrated Dynamic Bandwidth Allocation in Converged Passive Optical Networks and IEEE 802.16 Networks

IEEE 802.16 and Passive Optical Network (PON) are two promising broadband access technologies for high-capacity wireless access networks and wired access networks, respectively. The convergence of 802.16 and PON networks can take the mobility feature of wireless communications and the bandwidth advantage of optical networks jointly. Dynamic bandwidth allocation (DBA) plays an important role in each of these two networks for QoS assurance. In converged 802.16 and PON networks, the integration of the DBA schemes in both networks plays an even more critical role, since bandwidth request/grant mechanisms used in 802.16 and PON are different and the performance of the integrated DBA directly determines the overall system performance. In this paper, we investigate integrated dynamic bandwidth allocation schemes and their signaling overhead. First, this paper starts with discussing the converged network architecture and especially the issues on integrating optical network unit (ONU) and 802.16 base station (BS). Second, it proposes a slotted DBA (S-DBA) scheme and its performance analytic model. The S-DBA scheme takes into account the specific features of the converged network, aiming to reduce signaling overhead caused by cascaded bandwidth requests and grants. The simulation results show that the proposed S-DBA scheme can effectively reduce signaling overhead and increase channel utilization.

A QoS-Aware Dynamic Bandwidth Allocation Algorithm for Relay Stations in IEEE 802.16j-Based Vehicular Networks

IEEE 802.16 has been regarded as a promising broadband wireless access technology for its large coverage, quality of service (QoS) support for different types of application, and easy deployment. IEEE 802.16j is an extension of IEEE 802.16 to support relay mode operation. This paper applies IEEE 802.16j to vehicular network to provide Internet access for high-way vehicles. In particular, it proposes a dynamic bandwidth allocation (DBA) algorithm specifically for relay stations (RS) to support QoS requirements of different types of service. The objective of the proposed DBA is to allocate bandwidth from relay station to its serving subscriber stations (SSs) with QoS consideration. The simulation results have shown the effectiveness and efficiency of the proposed DBA algorithm.

A selective downlink scheduling algorithm to enhance quality of VOD services for WAVE networks

Providing quality-of-service- (QoS-) guaranteed video on demand (VOD) services over wireless access in vehicular environments (WAVEs) is a challenge as WAVE adopts enhanced distributive channel access (EDCA), a contention-based channel access mechanism, for air interface access control. This paper proposes a selective downlink scheduling (SDS) algorithm to enhance the quality of VOD for WAVE networks. According to the importance of video decoding, video packets are categorized into high and low priorities. The categorized packets are put into different queues in roadside units (RSUs) to contend for transmission opportunities. Aiming to improve video playback quality and reduce video playback delay, the proposed SDS algorithm schedules video packets based on their importance, playback deadline, and their real-time parameters of receiving onboard units (OBUs), such as velocity and remaining dwelling time. The effectiveness of SDS algorithm is verified by simulations.