A sleep-mode interleaving algorithm for layered-video multicast services in IEEE 802.16e networks

In this paper we investigate efficient mechanisms to support layered-video multicast services in IEEE 802.16e (Mobile WiMAX) networks.¹ Given the bandwidth eager and energy hungry nature of layered-video multicast services, network systems should employ efficient bandwidth allocation and energy saving mechanisms. We first investigate how the WiMAX energy saving mechanisms significantly degrade the performance of multicast bandwidth allocation mechanisms for layered-video multicast services. Then, we present a theoretical model for illustrating this interaction problem. To the best of our knowledge, this paper offers the first investigation into and the first theoretical model of the interaction problem between multicast bandwidth allocation and WiMAX energy saving mechanisms. To solve the interaction problem, we propose a novel sleep-mode interleaving algorithm beyond the existing mechanisms. The proposed algorithm has full compatibility with the existing multicast bandwidth allocation mechanisms and with IEEE 802.16e standards. By appropriately adjusting one sleep mode parameter defined in the standard, the proposed sleep-mode interleaving algorithm effectively guarantees the bandwidth efficiency of the video multicast mechanisms while mobile users can execute the standard sleep mode operations. Simulation results demonstrate the effectiveness of the proposed algorithm in terms of packet delivery ratio, user satisfaction, energy efficiency and computational complexity.     

Optimization of QoS parameters using scheduling techniques in heterogeneous network

Multimedia applications in wireless communication have been increased in recent years. A variety of wireless access technologies is introduced for various needs. The abundant increase in mobile computing devices and different networking systems leads to the support of user’s mobility on heterogeneous network. In general, the roaming users migrate between two different wireless technologies and their service must be supported by vertical handover (HO). Since the roaming users expect a rapid handover experience while switching from one wireless network to another, the handover operation must be enhanced by the networks. Various wireless technologies such as wireless LAN, Worldwide Interoperability for Microwave Access (WiMAX), and the 3G Partnership Project (3GPP) are interlaced to support many wireless services in rural, urban, and global scenarios. Moreover, quality of service (QoS) has become more significant in many applications where wireless network resources are utilized. In this paper, a handover management scheme is proposed for QoS enhancement in roaming users between WiMAX and WLAN by subscribers of networks belonging to the 3GPP standards. The proposed algorithms genetic queuing, proportionally fair queuing, and WiMAX aware load balancing are analyzed in the scheduling process during handover. The simulation is implemented using NS–2 and the experimental results are obtained for the proposed algorithms and compared with the standard scheme.     

WiMAX上行链路实时业务改进调度算法

针对WiMAX建议的rtPS和ertPS调度机制处理变速率实时业务时MAC层开销大,导致时延增大的缺点,提出了一种能够有效调度多用户变速率实时业务的上行链路调度算法。该算法在SS端实时监控数据率,减少发送带宽请求的次数,从而提高整体的上行链路资源利用率,并在BS上行调度器中优化调度策略,使得最急迫的用户优先得到服务。仿真结果表明该算法与ertPS相比,在不影响系统吞吐量的情况下上行时延减少了约15%。     

Design,implementation and experimental evaluation of an end-to-end vertical handover scheme on NCTUns simulator

This paper presents the simulation study of “Host based autonomous Mobile Address Translation” using NCTUns simulator. It is a network layer, end-to-end vertical handover solution, based upon modification of “Mobile IP with address Translation”. Vertical handover approaches generally require new network elements, a new layer in TCP/IP stack, or fixing a protocol at a particular layer. To enhance handover experience, recent approaches focus on reducing signalling, localizing the registration, creating hierarchies, using proxy, preparing handover in advance, predicting target network, or exploiting multicasting and path extension techniques. These approaches, however, demand change in the network infrastructure to support mobility and limit the scope of mobility. Despite end-to-end signalling, the Host based autonomous Mobile Address Translation scheme ensures minimum service disruption and distinctly allows global mobility of the mobile node without requiring any modification in the network. We have simulated the mobility of a multi-interface mobile node in a heterogeneous network environment composed of WiFi (IEEE802.11a, IEEE802.11b) and WiMAX (IEEE802.16e) access networks. Performance of the scheme is evaluated taking into account wide range of end-to-end delays between mobile node and the correspondent node, various speeds of the mobile node and different packet loss rates of the network. Based on our detailed simulation study, it has been observed that this scheme offers reduced service disruption time, packet loss and packet latency. The service disruption time is found to be significantly low (typically in the range of 10 ms) compared to that of Mobile IP (which is in the order of 100 ms); this makes this new scheme perfectly suitable for real time applications. Low service disruption time consequently reduces the packet loss by manyfold and the packet latency remains unaffected during and after handover due to translation of address at the source. The results suggest that this protocol is a viable vertical handover solution due to its simplicity, scalability, low overhead and ready deployability.     

WiMAX Mesh网络中一种分布式时隙分配算法

提出了一种基于资源预留的WiMAX Mesh网络支持QoS的微时隙动态分配算法。通过区分数据流优先级的方式将业务分为高优先级业务和低优先级业务两类,对高优先级的业务在每帧中预留一定的微时隙作为分配高优先级业务的时隙,预留时隙大小可以根据网络时隙使用状态动态地进行调整。仿真表明该算法在满足高优先级业务QoS的同时兼顾业务的请求失败率与时隙的利用率,降低了分组的平均时延。     

无线自主网中位置扩散服务性能仿真比较

无线自主网中的位置信息辅助路由协议需要网络中的节点获得其它节点的位置信息.位置信息服务的选择会显著影响路由协议的性能.通过仿真对无线自主网中现有的位置扩散服务从位置平均误差、误差分布、分组开销和字节数开销等方面进行了比较.所比较的位置扩散服务种类是迄今为止最多的.仿真结果表明,SNLUS协议所消耗的分组开销最少,而PULS协议所带来的平均位置误差最小.比较结果不仅对于现有位置服务协议的选择具有参考价值,而且对于位置扩散服务的改进和新协议的提出也有重要意义.     

较小动态服务组合代价GLRA算法的设计与实现

针对动态服务组合的关键是优化组合后的服务代价这一问题,论文提出了较小动态服务组合代价GLRA算法,该算法首先对服务组合进行建模,针对动态服务组合中的Candidate Service模型,抽取出有向无环图,并根据服务代价动态性特点,使用基于贪心的局部修正算法,该算法每次都从当前值选取最小值,迭代次数和服务深度有关,循环次数有限.仿真结果表明算法能够高效的找到代价较小的组合方案,具有更好的时间复杂度.     

PolyMAX,a Mobile WiMAX module for the ns-2 simulator with QoS and AMC support

In this paper, we present the PolyMAX module which enhances network simulator 2 (ns-2), the most popular network simulator used in academia, to provide one of the most complete simulation tools to evaluate the performance of Mobile WiMAX networks. PolyMAX is based on the National Institute of Standards and Technology (NIST) module and our specific contributions consist on the design and implementation of the Quality of Service (QoS) classes and QoS management messages, the uplink access grant-request mechanisms, Adaptive Modulation and Coding, and a scheduler handling all five WiMAX QoS classes. We also present validation results for the different components of our module and typical WiMAX simulation scenarios illustrating its flexibility and some of its features. The PolyMAX module represents an important tool enabling researchers to easily implement their Mobile WiMAX scheduling and Adaptive Modulation and Coding (AMC) algorithms and accurately evaluate their performance for realistic scenarios.     

WiMAX系统突发实时业务调度算法的改进

针对现有WiMAX系统MAC层没有提供不同优先级业务具体调度方案的现状,在分析传统分级调度算法的基础上,提出一种针对实时业务突发性的改进DFPQ调度算法实现方案。该方案在带宽分配过程中,通过判断实时业务突发性增多,强制将低优先级业务的一部分带宽分配给实时业务。GloMoSim网络仿真环境下的仿真结果证明,该调度策略在满足各业务QoS要求方面优于传统分级调度策略。     

Role-based access control for grid database services using the community authorization service

In this paper, we propose a role-based access control (RBAC) method for grid database services in open grid services architecture-data access and integration (OGSA-DAI). OGSA-DAI is an efficient grid-enabled middleware implementation of interfaces and services to access and control data sources and sinks. However, in OGSA-DAI, access control causes substantial administration overhead for resource providers in virtual organizations (VOs) because each of them has to manage a role-map file containing authorization information for individual grid users. To solve this problem, we used the community authorization service (CAS) provided by the globus toolkit to support the RBAC within the OGSA-DAI framework. The CAS grants the membership on VO roles to users. The resource providers then need to maintain only the mapping information from VO roles to local database roles in the role-map files, so that the number of entries in the role-map file is reduced dramatically. Furthermore, the resource providers control the granting of access privileges to the local roles. Thus, our access control method provides increased manageability for a large number of users and reduces day-to-day administration tasks of the resource providers, while they maintain the ultimate authority over their resources. Performance analysis shows that our method adds very little overhead to the existing security infrastructure of OGSA-DAI.     

保证服务质量的Web服务优化选取

快速、准确地发现满足用户需求的Web服务是目前Web服务发现的一个研究重点。文中提出了一个基于服务质量的语义Web服务发现框架。首先采用遗传算法来实现服务的聚类预处理,以此来降低服务的查找空间,提高服务的查询效率。进一步,针对服务请求者对服务质量的需求,实现了基于WSMO-QoS的服务匹配策略。最后,实验结果表明了所提方法的有效性。     

一种基于WiMAX mesh网络的区分服务调度方案

IEEE 802.16支持多种不同类型的调度服务,并将服务质量支持机制引入媒体接入控制层,却没有规定相应的调度算法。在IEEE 802.16定义的mesh模式下,针对不同类型服务,提出了一种区分服务的调度方案,该方案采用集中式和分布式混合调度。仿真结果表明:该方案下系统平均时延和用户满意度均有所改善。     

Investigation on runtime partitioning of elastic mobile applications for mobile cloud computing

The latest developments in mobile computing technology have increased the computing capabilities of smartphones in terms of storage capacity, features support such as multimodal connectivity, and support for customized user applications. Mobile devices are, however, still intrinsically limited by low bandwidth, computing power, and battery lifetime. Therefore, the computing power of computational clouds is tapped on demand basis for mitigating resources limitations in mobile devices. Mobile cloud computing (MCC) is believed to be able to leverage cloud application processing services for alleviating the computing limitations of smartphones. In MCC, application offloading is implemented as a significant software level solution for sharing the application processing load of smartphones. The challenging aspect of application offloading frameworks is the resources intensive mechanism of runtime profiling and partitioning of elastic mobile applications, which involves additional computing resources utilization on Smart Mobile Devices (SMDs). This paper investigates the overhead of runtime application partitioning on SMD by analyzing additional resources utilization on SMD in the mechanism of runtime application profiling and partitioning. We evaluate the mechanism of runtime application partitioning on SMDs in the SmartSim simulation environment and validate the overhead of runtime application profiling by running prototype application in the real mobile computing environment. Empirical results indicate that additional computing resources are utilized in runtime application profiling and partitioning. Hence, lightweight alternatives with optimal distributed deployment and management mechanism are mandatory for accessing application processing services of computational clouds.     

Personalised ubiquitous file access with XML Web Services

The explosion of new types of end-user devices, as well as the increase in the number of users with broadband connection in private households, opens up the opportunity to provide access to documents and services residing in the home domain from remote locations. Also, the increased mobility of users, as well as the need to be able to work in all locations, further adds to the requirement of remote document access. The contribution of this paper is threefold. First, it introduces the Mobile Home Access system, which simplifies remote access to resources in a home domain. The Mobile Home Access (MHA) system is based on the Service-Oriented Computing concept and realized using XML Web Services for communication between the home domain and the end-user device, while employing the Common Internet File System (CIFS) network file system to allow appropriate file access in the home domain. The second contribution is the mechanism whereby such a service can be deployed when network elements like firewalls and NAT routers are introduced. The challenge of establishing a connection from a remote device is general for both client–server services and peer-to-peer services. The paper proposes and describes a design and implementation of a solution using XML Web Services technologies, and thus shows how NAT traversal technology can be integrated with such middleware. The third contribution of this paper is a performance analysis of the current implementation of the Mobile Home Access service. The results of the analysis should be interesting for the applicability of XML Web Services in mobile computing in general.     

移动边缘计算中资源受限的动态服务部署策略

移动边缘计算（MEC）的出现使移动用户能够以低延迟访问部署在边缘服务器上的服务。然而,MEC仍然存在各种挑战,尤其是服务部署问题。边缘服务器的数量和资源通常是有限的,只能部署数量有限的服务;此外,用户的移动性改变了不同服务在不同地区的流行度。在这种情况下,为动态请求部署合适的服务就成为一个关键问题。针对该问题,通过了解动态用户请求来部署适当的服务以最小化交互延迟,将服务部署问题表述为一个全局优化问题,并提出了一种基于集群划分的资源聚合算法,从而在计算、带宽等资源约束下初步部署合适的服务。此外,考虑动态用户请求对服务流行度及边缘服务器负载的影响,开发了动态调整算法来更新现有服务,以确保服务质量（QoS）始终满足用户期望。通过一系列仿真实验验证了所提出策略的性能。仿真结果表明,与现有基准算法相比,所提出的策略可以降低服务交互延迟并实现更稳定的负载均衡。     

智慧城市中QOE感知服务组合策略的研究

无线传感器的发展和物联网技术的应用,配有物联网的设备正以一种全新的“智能终端服务”的形式进入人类生活,要想在复杂冗余的物联网环境中寻得满足不同用户需求的服务,需要考虑服务组合的概念。为此,在对传统服务组合研究方法深入分析的基础上,提出了智慧城市的服务组合选择策略。首先根据物联网应用服务的多样性,通过改进蚁群算法获得用户对服务的偏好顺序,然后使用层次化QOE评价模型量化客户体验质量,进而选出最优服务组合提供给用户。根据提出的服务组合策略,给出服务选择具体的实施流程,通过仿真模拟表明基于改进蚁群算法的服务组合策略在服务选择问题上具有一定的推广价值。     

A utility-based algorithm for joint uplink/downlink scheduling in wireless cellular networks

The major driver for deploying next generation wireless cellular systems is their ability to efficiently deliver resource-demanding services, many of which require symmetric communication between an uplink mobile user and a downlink mobile user that belong to the same network. In this work, we propose a utility-based joint uplink/downlink scheduling algorithm suitable for wireless services involving pairwise communication among mobile users. While most existing literature focuses on downlink-only or uplink-only scheduling algorithms, the proposed algorithm aims at ensuring a utility function that jointly captures the quality of service in terms of delay and channel quality on both links. By jointly considering the time varying channel conditions in both the uplink and the downlink directions, the proposed algorithm avoids wasting of resources and achieves notable performance gains in terms of increased number of active connections, lower packet drop rate, and increased network throughput. These gains are achieved with a tradeoff cost in terms of complexity and signaling overhead. For overhead reduction in practical scenarios, we propose an implementation over clusters within the network.     

基于马尔可夫链与服务质量的网络可用性

针对网络可用性在不同网络业务中的服务质量（QoS）存在差异,且与性能花费相互制约的问题,引入了马尔可夫链理论,在定义了基于业务开销最小的服务能力匹配度的基础上构建了基于马尔可夫链和QoS指标的网络可用性（MCQNA）评价模型。首先,从最能反映网络可用特征的QoS指标出发,兼顾性能开销,同时定义了代价函数,并且给出了状态转移矩阵;然后,通过平稳状态与网络可用性关系的分析,求解出平稳分布并作为QoS运行开销的动态权重,实现了以业务运行代价最小为特点的网络可用性评判。仿真结果表明,所提模型构建的遍历性转移矩阵存在平稳分布,对网络可用性评判是可行的。该模型能针对不同业务的QoS标准,且有效针对具体业务衡量网络的可用性。     

Autonomous network-based integration architecture for multi-agent systems under dynamic and heterogeneous environment

Multi-agent systems fit nicely into domains that are naturally distributed and require artificial intelligence technology. Has been designed an autonomous information services integration architecture based on network to support the rapid changing environments and needs. However, substantial increase of users requests and redirects it may cause the system to unbalance loading and part overloading. This paper proposes an integrated access method by reduces the number of Pull Mobile Agents to reduces the total load of the system in order to achieveautonomous load distribution. In addition, the information structure of integrated service area is effective to improve the ratio of the satisfaction of Pull-Mas (Pull Mobile Agents) with joint request on one node. Through simulation tests show that this system can be guaranteed that services requests and related services requests is uniformly distributed to the nodes of system and ensure that the system load balancing.