Evolution and service requirements of CBR applications on ATM networks

Broadband integrated networks based on asynchronous transfer mode (ATM) technology are being proposed to provide a single integrated access to a variety of services and applications. Constant bit rate services will form an important part of this unified networking solution. In this paper, we identify and describe the relevant aspects related to the implementation of CBR services on ATM. First, we identify two broad categories of potential CBR services for broadband ATM networks. The ATM infrastructure for the identified services is then developed along with the required functionalities of different network elements. Finally, end-to-end performance objectives for the ATM network are determined and verified empirically based on results of laboratory experiments. These performance objectives help us determine the minimum QOS required by the highest class of service category offered by an ATM network.     

Cross-layer optimization for wireless multihop networks with pairwise intersession network coding

For wireless multi-hop networks with unicast sessions, most coding opportunities involve only two or three sessions as coding across many sessions requires greater transmission power to broadcast the coded symbol to many receivers, which enhances interference. This work shows that with a new flow-based characterization of pairwise intersession network coding (coding across two unicast sessions), an optimal joint coding, scheduling, and rate-control scheme can be devised and implemented using only the binary XOR operation. The new scheduling/rate-control scheme demonstrates provably graceful throughput degradation with imperfect scheduling, which facilitates the design tradeoff between the throughput optimality and computational complexity of different scheduling schemes. Our results show that pairwise intersession network coding improves the throughput of non-coding solutions regardless of whether perfect/imperfect scheduling is used. Both the deterministic and stochastic packet arrivals and departures are considered. This work shows a striking resemblance between pairwise intersession network coding and non-coded solutions, and thus advocates extensions of non-coding wisdoms to their network coding counterpart.     

A cell switching WDM broadcast LAN with bandwidth guarantee andfair access

This paper presents the design of a cell-switching wavelength division multiplexing (WDM) local area network (LAN), which constitutes a key component of a next-generation internet (NGI) consortium project recently funded by DARPA. An important goal of the NGI project is to support bandwidth-on-demand services with quality-of-service (QOS) guarantee over WDM networks. As a first step toward this goal, we have developed several fast scheduling algorithms for flexible bandwidth reservations and fair sharing of unreserved bandwidth in a WDM broadcast network with fast-tunable transceivers. Unlike circuit-based bandwidth reservation schemes that impose a fixed schedule precomputed on setup, our scheme deals with bursty traffic by allocating network resources dynamically using very efficient algorithms. Our algorithms are based on a new concept of computing maximal weighted matchings, which is a generalization of maximal matchings on unweighted graphs. We prove that our algorithms can support total reserved bandwidth of up to 50% of the network capacity, and in that case constant delay bounds are also established. Simulations show that our algorithms can in practice support much higher reserved bandwidth-up to 90% of network capacity, and with much better delay bounds, even for burst traffic. In addition to the bandwidth guarantee, the unreserved bandwidth can be shared fairly among the users using our fair access algorithms with case to 100% network utilization in simulations     

Cross-layer Scheduling Algorithms for IEEE 802.16 Based Wireless Mesh Networks

Wireless mesh network (WMN) is emerging as an important networking architecture for future wireless communications. The mesh mode supported in IEEE 802.16 protocol provides a TDMA solution for WMN, in which scheduling is an important issue. In this paper, we discuss the issues on how to satisfy a set of bandwidth requests in IEEE 802.16 WMNs using minimal radio resources (or solving minimal schedule length problem). In consideration of transmission overhead and adaptive modulation and coding (AMC), two cross-layer scheduling algorithms are proposed, namely max-transmission and priority-based algorithms. In particular, they are proposed based on a physical interference model, instead of a protocol interference model as suggested in the literature. For the priority-based algorithm, we study several priority criteria based on different cross-layer information. An iterative scheme for QoS traffic is introduced to guarantee fairness when traffic load exceeds the network capacity. Simulation results show that our algorithms outperform the existing schemes based on protocol model, and they also ensure better fairness among different nodes.     

NGN和IMS对承载网QOS方面的要求和QOS保障技术

在通信运营商推行的光进铜退和网络演进改造过程中,大量的PSTN用户割接到了NGN或IMS网络;还有大量的企事业单位也在逐步使用企业级的NGN或IMS设备更新换代原有老化的传统的DID交换机设备。现有的PSTN网络以电路交换为特征,在支持语音通信上颇有优势;NGN或IMS网络为保证语音通信的质量,对其承载网在QOS保障方面有明确的指标要求。本文论述了NGN、IMS对承载网QOS方面的指标要求以及QOS的相关保障技术。     

基于IPv6的无线传感器网络关键技术研究

基于IPv6技术的无线传感器网络是一门新兴的网络技术,人们对它的研究尚处于起步阶段。在此主要论述IPv6技术在无线传感器网组网应用,对使用无线与有线相结合的通信方法,通信协议和算法的研究,使得视频监控系统信号,通信系统信号以及检测系统信号在同一个通信平台上互不干涉的平稳的传输信息。就IPv6无线传感器网络与现有网络的互联互通方式,关键技术和算法等方面进行概述。     

网络编码在MANET最小能量多播中的应用研究

网络编码理论是当代信息论的重要组成部分,移动特设网络(MANET)是由-组带有无线收发装置的移动终端组成的一个多跳临时性自治系统,利用网络编码理论解决MANET中最小能量多播问题是无线通信中新的研究热点之一.文中阐述了网络编码基本理论在无线通信中应用的技术原理,然后通过构建无线网络节点分层模型分析了基于网络编码的MANET最小能量求解过程,为解决该类型网络中能耗问题提供新的视角.     

A negotiation-based networking methodology to enable cooperation across heterogeneous co-located networks

In a future internet of things, an increasing number of every-day objects becomes interconnected with each other. Current network solutions are not designed to connect a large number of co-located devices with different characteristics and network requirements. To cope with increasingly large and heterogeneous networks, this paper presents an ‘incentive driven’ networking approach that optimizes the network performance by taking into account the network goals (‘incentives’) of all individual devices. Incentive driven networking consists of the following steps. First, devices dynamically search for co-located devices with similar network preferences and hardware and/or software capabilities. Next, if such devices are found, communities consisting of interconnected objects with similar network expectations are formed on an ad hoc basis. Due to the similarities between the involved devices, it is easier to optimize the network performance of each individual community. Finally, different communities can cooperate with each other by activating and sharing (software or hardware) network resources. The paper describes which (future) research is needed to realize this vision and illustrates the concepts with a number of simple algorithms. Through an experimental proof-of-concept implementation with two networks of resource-constrained embedded devices, it is shown that even these simple algorithms already result in improved network performance. Finally, the paper describes a large number of example use cases that can potentially benefit from our innovative networking methodology.     

编码TCP的理论研究与应用方法

为了深入理解编码TCP的原理,在讨论TCP Vegas协议和网络编码的基本形式的基础上,分别从无线网络发送端和接收端的角度深入论述了其与网络编码的融合方法以及网络编码层的结构和控制机理,在最后提出了NS2模拟软件底层代码的修改思路来实现检测网络编码TCP性能的目的。     

传感器网络变权组合预测流量整形算法

针对现有流量整形算法在传感器网络应用上的不足,提出了一种新的流量整形算法。分析了传感器网络流量具有突发随机性以及时变不均衡性的原因,根据传感器网络流量的模糊性、随机性以及时变性统一建模,提出了变权组合预测流量整形算法（TSAV,Traffic Shaping Algorithm with Variable weight combination forecast）,该算法通过逼近最优组合理论分配模糊AR预测与Kalman预测的组合权重,得到更为精确的预估流量值,提前规划整形速率从而平滑的输出分组流。实验表明,TSAV算法应用到传感器网络时能够准确预测流量,减少分组丢弃率的同时增大网络吞吐量,改善了传感器网络信息传输的QOS性能。      

MARC中联合BICM-ID和网络编码设计及性能分析

联合网络信道编码是将网络编码和信道编码联合处理,通过联合处理网络信道编码可以增加带有噪声信道的分集数,从而进一步提高网络容量。结合联合网络信道编码的思想,基于比特交织编码调制迭代译码(BICM-ID)设计了两种应用于多址接入中继信道(MARC)环境中的联合网络信道编码方案,并对这两种方案进行了仿真比较。仿真结果表明:在译码之前对解调后的软信息直接进行网络译码相比于对译码后的外信息进行网络译码能更加有效地利用中继信道传输的冗余信息。     

Consideration of node failures in network-reliability calculation

Terminal-pair reliability is a common measure of telecommunication network reliability, and many algorithms for calculating it have been published. Most such algorithms presume perfect nodes; although some have presumed imperfect nodes. This paper presents a very simple, uncomplicated way to account for imperfect nodes     

Routing subject to quality of service constraints in integratedcommunication networks

With increasingly diverse QOS requirements, it is impractical to continue to rely on conventional routing paradigms that emphasize the search for an optimal path based on a predetermined metric, or a particular function of multiple metrics. Modern routing strategies must not only be adaptive to network changes but also offer considerable economy of scope. We consider the problem of routing in networks subject to QOS constraints. After providing an overview of prior routing work, we define various QOS constraints. We present a call architecture that may be used for QOS matching and a connection management mechanism for network resource allocation. We discuss fallback routing, and review some existing routing frameworks. We also present a new rule-based, call-by-call source routing strategy for integrated communication networks     

An algebraic approach to network coding

We take a new look at the issue of network capacity. It is shown that network coding is an essential ingredient in achieving the capacity of a network. Building on recent work by Li et al.(see Proc. 2001 IEEE Int. Symp. Information Theory, p.102), who examined the network capacity of multicast networks, we extend the network coding framework to arbitrary networks and robust networking. For networks which are restricted to using linear network codes, we find necessary and sufficient conditions for the feasibility of any given set of connections over a given network. We also consider the problem of network recovery for nonergodic link failures. For the multicast setup we prove that there exist coding strategies that provide maximally robust networks and that do not require adaptation of the network interior to the failure pattern in question. The results are derived for both delay-free networks and networks with delays.     

基于反馈重传的网络信道编码多播研究

在无线网络中,采用现用机制(ARQ)带宽利用率并不是很高。针对这种情况,提出了一种将网络编码思想融入到重传机制中的方式———NC-ARQ,来提高单跳无线网络(例如WiMAX、WLAN等)的带宽利用率。此外,高误比特率下,在NC-ARQ基础上将网络编码与信道编码结合,即NC-HARQ,可以进一步改善无线网络的带宽利用率。分析了在传统反馈重传机制和信道编码中加入网络编码后,多播网络带宽利用率的增益。理论和仿真都证明了加入网络编码后,反馈重传机制的带宽利用率能得到较大改善。     

宽带网络与服务质量（QOS）

通过对宽网络的服务质量（ＱＯＳ）参数的分析，论述了ＡＴＭ宽带网络是如何满足不同业务的服务质量ＱＯＳ要求的。     

基于超宽带技术的无线Ad Hoc网络

文章研究了一种基于超宽带(UWB)和电路交换技术的无线AdHoc网络的结构和算法。该网络是面向无线个人局域网(PAN)的。文章对物理层进行了描述,并对数据传输技术进行了选择,提出了网络设备的实现模型,开发了网络的逻辑结构和算法(包括路由的基本原理、寻址系统以及网络服务质量参数的分析),讨论了组网过程中的特征以及可能存在的一些问题。     

Priority assignment control of ATM line buffers with multiple QOSclasses

In an asynchronous transfer mode (ATM) network multimedia environment, the bandwidth efficiency can be improved by defining multiple quality of service (QOS) classes and using a traffic control which manages required QOS of each class individually (QOS control). Priority assignment control is presented as a QOS control method in an ATM switching node. To quantitatively evaluate the control performance, the region determined by the offered load of each class where the QOS requirements of all the classes are satisfied is analytically obtained and various combinations of two classes and related control effects are discussed. When required values of cell loss rate and delay time are both different between the classes, the control effect is large; however, when only either of them is different, the effect is relatively small. The control scheme to enlarge the actual admissible offer load region by adaptively changing the priority assignment ratio is presented and its feasibility is confirmed by the simulation     

Efficient Broadcasting Using Network Coding

We consider the problem of broadcasting in an ad hoc wireless network, where all nodes of the network are sources that want to transmit information to all other nodes. Our figure of merit is energy efficiency, a critical design parameter for wireless networks since it directly affects battery life and thus network lifetime. We prove that applying ideas from network coding allows to realize significant benefits in terms of energy efficiency for the problem of broadcasting, and propose very simple algorithms that allow to realize these benefits in practice. In particular, our theoretical analysis shows that network coding improves performance by a constant factor in fixed networks. We calculate this factor exactly for some canonical configurations. We then show that in networks where the topology dynamically changes, for example due to mobility, and where operations are restricted to simple distributed algorithms, network coding can offer improvements of a factor of , where is the number of nodes in the network. We use the insights gained from the theoretical analysis to propose low-complexity distributed algorithms for realistic wireless ad hoc scenarios, discuss a number of practical considerations, and evaluate our algorithms through packet level simulation.