Bandwidth Adaptation Algorithms for Adaptive Multimedia Services in Mobile Cellular Networks

The fluctuation of available link bandwidth in mobilecellular networks motivates the study of adaptive multimediaservices, where the bandwidth of an ongoing multimedia call can bedynamically adjusted. We analyze the diverse objectives of theadaptive multimedia framework and propose two bandwidth adaptationalgorithms (BAAs) that can satisfy these objectives. The firstalgorithm, BAA-RA, takes into consideration revenue and``anti-adaptation' where anti-adaptation means that a user feelsuncomfortable whenever the bandwidth of the user's call ischanged. This algorithm achieves near-optimal total revenue withmuch less complexity compared to an optimal BAA. The secondalgorithm, BAA-RF, considers revenue and fairness, and aims at themaximum revenue generation while satisfying the fairnessconstraint defined herein. Comprehensive simulation experimentsshow that the difference of the total revenue of BAA-RA and thatof an optimal BAA is negligible. Also, numerical results revealthat there is a conflicting relationship between anti-adaptationand fairness.     

Asymptotic Connectivity in Wireless Ad Hoc Networks Using Directional Antennas

Connectivity is a crucial issue in wireless ad hoc networks (WANETs). Gupta and Kumar have shown that in WANETs using omnidirectional antennas, the critical transmission range to achieve asymptotic connectivity is $O(sqrt{log n/n})$ if $n$ nodes are uniformly and independently distributed in a disk of unit area. In this paper, we investigate the connectivity problem when directional antennas are used. We first assume that each node in the network randomly beamforms in one beam direction. We find that there also exists a critical transmission range for a WANET to achieve asymptotic connectivity, which corresponds to a critical transmission power (CTP). Since CTP is dependent on the directional antenna pattern, the number of beams, and the propagation environment, we then formulate a non-linear programming problem to minimize the CTP. We show that when directional antennas use the optimal antenna pattern, the CTP in a WANET using directional antennas at both transmitter and receiver is smaller than that when either transmitter or receiver uses directional antenna and is further smaller than that when only omnidirectional antennas are used. Moreover, we revisit the connectivity problem assuming that two neighboring nodes using directional antennas can be guaranteed to beamform to each other to carry out the transmission. A smaller critical transmission range than that in the previous case is found, which implies smaller CTP.      

无线多媒体传感器网络QoS区分服务路由机制

 无线多媒体传感器网络中多种类型数据并存,服务质量需求各异,因此如何提供服务质量保障机制是无线多媒体传感器网络研究领域的重点问题.本文提出了一种基于角度的区分服务路由算法,在该算法中,网络节点将各自的邻居节点按其偏转角度进行分类,为不同需求的数据流选择不同的转发区域,并结合邻居节点的地理位置、单跳通信负载、剩余能量等信息完成各数据流的区分路由.仿真结果表明,该算法在多媒体数据流传输的延迟、抖动、丢包率以及能耗等性能上均要优于已有算法.     

A Context-Aware Network Equipment for Dynamic Adaptation of Multimedia Services in Wireless Networks

B3G (Beyond 3rd Generation) networks is the next step in the wireless world. It will enable the delivery of services to end-users, on different underlying wireless access networks and customised to users’ context. Furthermore, seamless mobility between networks and switch of devices will be handled in a transparent way. In this paper, a Context-Aware Network Equipment (CANE) is introduced, that is able to dynamically adapt multimedia services according to the users’ context. The term context includes the users’ device, the users’ preferences, the network conditions as well as the service provider adaptation policies. As a proof of concept, an implementation of a CANE is given for a 802.11 network use-case. An evaluation of the prototype as well as simulations of the proposed solution, both for an audio streaming service and a video streaming service, are presented. The results show that adapting multimedia services in case of network overload can enable to maintain an acceptable quality of service delivered to end-users and even to allow more users to enjoy the services, which will not be possible without the CANE.     

Connectivity Based k-Hop Clustering in Wireless Networks

In this paper we describe several new clustering algorithms for nodes in a mobile ad hoc network. The main contribution is to generalize the cluster definition and formation algorithm so that a cluster contains all nodes that are at distance at most k hops from the clusterhead. We also describe algorithms for modifying cluster structure in the presence of topological changes. We also proposed an unified framework for most existing and new clustering algorithm where a properly defined weight at each node is the only difference in otherwise the same algorithm. This paper studied node connectivity and node ID as two particular weights, for k=1 and k=2. Finally, we propose a framework for generating random unit graphs with obstacles.     

Cross-Layer Design and Analysis of Wireless Networks Using the Effective Bandwidth Function

In this paper, we propose a useful framework for the cross-layer design and analysis of wireless networks where ARQ (automatic repeat reQuest) and AMC (adaptive modulation and coding) schemes are employed. To capture the joint effect of the packet transmission error rate at the PHY layer and the packet loss probability at the MAC layer, we introduce the effective bandwidth function of the packet service process. Base on queueing analysis with this effective bandwidth function, our cross-layer design tries to satisfy the required packet loss probability by each user and minimize the average packet transmission error rate. Numerical examples are provided to show the usefulness and characteristics of our framework.     

Cooperative Connectivity Models for Wireless Relay Networks

This paper considers the ways that cooperating terminals can be connected to each other in wireless relay networks and the constraints imposed by the availability of different system resources. A framework is developed that exposes the relationship between constraints on available system resources and the achievable combinations of communication links between cooperating terminals. Cooperative connectivity models defined by the achievable combinations of links are derived, associated with their minimum cost constraint sets, and mapped to diversity techniques presented in the literature. The constraints considered are the available number of orthogonal relaying channels, the ability of terminals to diversity combine signals on a single common channel, the ability of terminals to diversity combine signals on orthogonal channels, the ability of terminals to transmit signals on multiple orthogonal channels, and the ability of terminals to cancel the effects of interhop interference.     

QoS Provisioning in Wireless/Mobile Multimedia Networks Using an Adaptive Framework

Recently there is a growing interest in the adaptive multimedia networking where the bandwidth of an ongoing multimedia call can be dynamically adjusted. In the wireless/mobile multimedia networks using the adaptive framework, the existing QoS provisioning focused on the call blocking probability and the forced termination probability should be modified. We, therefore, redefine a QoS parameter – the cell overload probability – from the viewpoint of the adaptive multimedia networking. Then, we propose a distributed call admission control (CAC) algorithm that guarantees the upper bound of the cell overload probability. Also, a bandwidth adaptation algorithm which seeks to minimize the cell overload probability is also presented. Simulation experiments are carried out to verify the performance of the proposed CAC algorithm. Furthermore, the performance of the adaptive wireless/mobile network is compared to that of the existing non-adaptive wireless/mobile networks. As a further step in QoS provisioning, we propose another QoS parameter, the degradation period ratio, and discuss analytically how the CAC algorithm guarantees the upper bound of the degradation period ratio.     

Multi-class Bandwidth Reservation Scheme Based on Mobility Prediction for Handoff in Multimedia Wireless/Mobile Cellular Networks

Next generation of wireless cellular networks aim at supporting a diverse range of multimedia services to Mobile Terminal (MT) with guaranteed Quality of Service (QoS). The challenge is to maintain the playing continuity of multimedia streams during handoff. In this paper, a bandwidth reservation scheme based on mobility prediction is proposed, to enable high accurate prediction of next crossing cell (target cell) which a MT is going to, in order to avoid too early or over reservation resulting in a waste of resources. The amount of bandwidth to be reserved is dynamically adjusted according to (a) the current position (location) and the extrapolated direction of MT and; (b) the sector and zones of the cell. A Call Admission Control scheme (CAC) is also considered to further guarantee the QoS of real time traffic. The performance of the system is evaluated through discrete event simulation of the wireless cellular environment. Simulation results show that the proposed scheme as compared to several existing schemes is able to reduce the Handoff Call Dropping Probability (HCDP) of real time traffic and the number of terminated ongoing calls of non-real time traffic. In addition, it is efficient to reduce the number of cancelled reservation and subsequently increase the system bandwidth utilization.

Cooperative Caching in Wireless Multimedia Sensor Networks

The recent advances in miniaturization and the creation of low-power circuits, combined with small-sized batteries have made the development of wireless sensor networks a working reality. Lately, the production of cheap complementary metal-oxide semiconductor cameras and microphones, which are able to capture rich multimedia content, gave birth to what is called Wireless Multimedia Sensor Networks (WMSNs). WMSNs will boost the capabilities of current wireless sensor networks, and will fuel several novel applications, like multimedia surveillance sensor networks. WMSNs introduce several new research challenges, mainly related to mechanisms to deliver application-level Quality-of-Service (e.g., latency minimization). To address this goal in an environment with extreme resource constraints, with variable channel capacity and with requirements for multimedia in-network processing, the caching of multimedia data, exploiting the cooperation among sensor nodes is vital. This article presents a cooperative caching solution particularly suitable for WMSNs. The proposed caching solution exploits sensor nodes which reside in “positions” of the network that allow them to forward packets or communicate decisions within short latency. These so-called “mediator” nodes are selected dynamically, so as to avoid the creation of hot-spots in the communication and the depletion of their energy. The mediators are not more powerful than the rest of the nodes, but they have some special role in implementing the cooperation among the sensors. The proposed cooperative caching protocol includes components for locating cached data as well as for implementing data purging out of the sensor caches. The proposed solution is evaluated extensively in an advanced simulation environment, and it is compared to the state-of-the-art cooperative caching algorithm for mobile ad hoc networks. The results confirm that the proposed caching mechanism prevails over its competitor.     

Cache consistency in Wireless Multimedia Sensor Networks

The production of cheap CMOS cameras, which are able to capture rich multimedia content, combined with the creation of low-power circuits, gave birth to what is called Wireless Multimedia Sensor Networks (WMSNs). WMSNs introduce several new research challenges, mainly related to mechanisms to deliver application-level Quality-of-Service (e.g., latency minimization). Such issues have almost completely been ignored in traditional WSNs, where the research focused on energy consumption minimization. Towards achieving this goal, the technique of cooperative caching multimedia content in sensor nodes can efficiently address the resource constraints, the variable channel capacity and the in-network processing challenges associated with WMSNs. The technological advances in gigabyte-storage flash memories make sensor caching to be the ideal solution for latency minimization. Though, with caching comes the issue of maintaining the freshness of cached contents. This article proposes a new cache consistency and replacement policy, called NICC, to address the cache consistency issues in a WMSN. The proposed policies recognize and exploit the mediator nodes that relay on the most “central” points in the sensor network so that they can forward messages with small latency. With the utilization of mediator nodes that lie between the source node and cache nodes, both push-based and pull-based strategies can be applied in order to minimize the query latency and the communication overhead. Simulation results attest that NICC outperforms the state-of-the-art cache consistency policy for MANETs.     

Auction-Based Bandwidth Allocation in Multi-Hop Wireless Ad Hoc Networks

In this paper, we propose a multi-hop auction-based bandwidth allocation mechanism to address the flow contention problem in wireless ad hoc networks. By modeling the problem as an iterative auction-based structure, it enables us to derive fair and efficient bandwidth allocation to each node on the basis of only local information. Further, a multi-hop flow coordination mechanism is then developed to optimize the network performance. Simulation results suggest that the proposed mechanism outperforms other approaches in terms of network throughput, bandwidth utilization, fairness, end-to-end delay, packet loss rate, and robustness.     

Dynamic Bandwidth Management in Single-Hop Ad Hoc Wireless Networks

Distributed weighted fair scheduling schemes for Quality of Service (QoS) support in wireless local area networks have not yet become standard. Therefore, we propose an Admission Control and Dynamic Bandwidth Management scheme that provides fairness and a soft rate guarantee in the absence of distributed MAC-layer weighted fair scheduling. This scheme is especially suitable for smart-rooms where peer-to-peer multimedia transmissions need to adapt their transmission rates co-operatively. We present a mapping scheme to translate the bandwidth requirements of an application into its channel time requirements. The center piece of our scheme is a Bandwidth Manager, which allots each flow a share of the channel, depending on the flow's requirements relative to the requirements of other flows in the network. Admitted flows control their transmission rates so they only occupy the channel for the fraction of time allotted to them. Thus co-operation between flows is achieved and the channel time is fair shared. As the available channel capacity changes and the traffic characteristics of various flows change, the Bandwidth Manager dynamically re-allocates the channel access time to the individual flows. Our simulation experiments show that, at a very low cost and with high probability, every admitted flow in the network will receive at least its minimum requested share of the network bandwidth. We also present extensive testbed experiments with our scheme using a real-time audio streaming application running between Linux laptops equipped with standard IEEE 802.11 network cards.     

无线多媒体传感器网络研究

无线多媒体传感器网络(WMSNs)是在传统无线传感器网络(WSNs)的基础上发展起来的具有音频、视频、图像等多媒体信息感知功能的新型传感器网络,具有广阔的应用前景。该文介绍了WMSNs的概念,分析了WMSNs区别于传统WSNs的个性化特点。对节点系统、MAC协议、路由协议、多媒体信息处理等关键技术的国内外研究现状、面临的问题和可行的解决方案进行了深入探讨。最后对WMSNs亟待解决的问题和发展趋势进行了总结。     

Bandwidth Efficient Video Multicasting in Multiradio Multicellular Wireless Networks

In this paper, we propose a new mechanism to select the cells and the wireless technologies for layer-encoded video multicasting in the heterogeneous wireless networks. Different from the previous mechanisms, each mobile host in our mechanism can select a different cell with a different wireless technology to subscribe each layer of a video stream, and each cell can deliver only a subset of layers of the video stream to reduce the bandwidth consumption. We formulate the Cell and Technology Selection Problem (CTSP) to multicast each layer of a video stream as an optimization problem. We use Integer Linear Programming to model the problem and show that the problem is NP-hard. To solve the problem, we propose a distributed algorithm based on Lagrangean relaxation and a protocol based on the proposed algorithm. Our mechanism requires no change of the current video multicasting mechanisms and the current wireless network infrastructures. Our algorithm is adaptive not only to the change of the subscribers at each layer, but also the change of the locations of each mobile host.     

无线Ad Hoc网络中动态的带宽管理

基于已有的带宽管理机制,采用加权公平对竞争的流分配带宽,不仅可以对流实现准入控制,以保证每条流的最低信道时间需求,同时也能动态地调节流所分配的信道时间。另外,我们的方案,也适用于多跳的情况,通过例子说明,在考虑到用户需求的同时,也提高了网络的吞吐量。     

A Dual Feedback Approach of Request-Based Bandwidth Allocation for Real-Time Service in Broadband Wireless Access Networks

We propose an efficient request-based uplink bandwidth allocation algorithm for variable-rate real-time service in broadband wireless access networks. By introducing a notion of target delay under the framework of dual feedback, the proposed algorithm can regulate delay while minimizing delay jitter and bandwidth waste.     

Energy Harvesting System Design and Optimization Using High Bandwidth Rectenna for Wireless Sensor Networks

Wireless Personal Communications - Today’s world has a keen interest in systems which are battery-less and can harvest energy from their surroundings. There is an increased demand for...     

无线分组数据自适应技术

对于分组数据业务来说 ,如果用户有一个良好的连接 ,则蜂窝的频谱效率和数据速率都会得到长足的提高 ,全世界所有的蜂窝标准都利用了这一点来进行数据速率自适应 ,文中就以下几种系统描述数据速率自适应过程 :CDMA (IS - 95 ) ,宽带CDMA (CDMA2 0 0 0和UMTSCDMA) ,TDMA (IS - 136 )和GSM (GPRS和EDGE) ,并探讨一些尚待解决的问题