An adaptive FEC scheme for data traffic in wireless ATM networks

A new adaptive forward-error-correction scheme (AFEC) is introduced at the link layer for TCP/IP data traffic in wireless ATM networks. The fading and interference in wireless links cause high and variable error rates, as well as bursty errors. The purpose of the AFEC scheme is to provide a dynamic error-control mechanism by using Reed-Solomon coding to protect the ATM cell payload, as well as the payload type indicator/cell loss priority fields in the ATM cell header. In order to enhance the error tolerance in cell framing and correct delivery, the AFEC scheme functions within a new concept called LANET framing and addressing protection mechanisms. The AFEC scheme has been validated using a simulation testbed of a low-speed wireless ATM network     

Policing of realistic VBR video traffic in an ATM network

ATM has been accepted by CCITT as the transport mechanism for the future BISDN and will also be widely used in future customer premises networks. Networks based on the ATM principle are expected to provide a very flexible communications infrastructure allowing customers to make effective use of a wide variety of offered services. To provide this flexibility with an acceptable quality of service while operating the network in an economic way, elaborate traffic management functions will be necessary to control the traffic flows within the network. This paper will study one of these functions—the so-called ‘usage parameter control’ or ‘policing’ function—in some detail to illustrate some of the problems that arise and point out possible solutions. The mechanisms chosen to implement the policing function will be the ‘leaky bucket’ mechanism, the ‘jumping window’ mechanism and the ‘moving window’ mechanism. The input streams used to assess the mechanisms represent different types of video communication—videophone, video conference and entertainment video—coded according to different variable bit-rate (VBR) algorithms. In contrast to most of the previous studies, where artificial, statistical traffic sources have been used, the sources used in this paper are directly based on measured ‘real-life’ video data. This ensures that all the statistical properties of the actual traffic stream are preserved and allows identification of the different factors that influence the dimensioning and the performance of the policing mechanism. The results of this study show that the uncertainty about the key parameters at call set-up and the considerable impact of single scenes make the proper dimensioning of policing mechanisms difficult. Furthermore, it seems not to be practical to use the long term mean bit-rate as the key traffic control parameter for these sources. Results indicating that the long-term cell loss ratio is not a sufficient measure for the quality of service are also presented. A comparison of the mechanisms shows that from a performance perspective, the ‘leaky bucket’ mechanism is superior to the two window mechanisms. This work is relevant to evolving standards for both BISDN traffic management and variable bit-rate video coding.     

Virtual reservation scheme for supporting CBR multimedia services with strict QoS performance over WLAN and wireless mesh

Carrier sense multiple access and its variants have been widely used in mobile ad hoc networks. However, most existing access mechanisms cannot guarantee quality of service for real‐time traffic. In this paper, we present a novel approach to guarantee the performance of real‐time applications such as voice and video that require periodic access to the wireless local area network (WLAN) channel. Our approach can work either with distributed coordination function or enhanced distributed coordination function, and includes distributed reservations of time slots between the stations sharing the WLAN without the need to send any signaling or control messages. Stations can access the wireless medium only if they are able to complete the frame transmission without interruption to the reserved slots of existing real‐time sessions. Simulation results indicate that the proposed mechanism provides high channel utilization, and bounded delays and jitter for real‐time traffic. Copyright © 2009 John Wiley & Sons, Ltd.     

无线ATM通信网中一种新的快速越区切换方案

本文根据地无线ATM通信网中快速越区切换问题的研究,提出了一种新的基于虚道路（VP）的快速越区切换方案,并通过建立简化的呼叫模型对该方案的切换性能进行了理论分析和比较,其结果表明,该方案的各项性能均比虚拟连接树（VCT）方案和永久虚连接（PVC）方案优越。     

一种新的ATM网VBR视频业务模型

许多研究工作表明ＶＢＲ视频业务的每帧信元数服从Ｇａｍｍａ分布，便是考虑这一性质的视频业务模型却很少。本文提出一种新的视频业务模型，一阶自回归Ｇａｍｍａ序列，以值是Ｇａｍｍａ分布的随机变量，文中给出ＧＡＲ模型的定义及有关性质，对ＧＡＲ（１）视频模型的参数估计方法也作了研究。     

Tiered bandwidth reservation scheme for multimedia wireless networks

It is important to provide quality of service (QoS) guarantees if we want to support multimedia applications over wireless networks. In this paper, considering the features of tiering in sectored cellular networks, we propose a novel scheme for bandwidth reservation to approach QoS provisioning. By predicting the movement of each connection, the reserving of bandwidth is only required in needful neighboring cells instead of in all neighboring cells. In addition, an admission control mechanism incorporated with bandwidth borrowing assists in distributing scarce wireless bandwidth in more adaptive way. Through mathematical analysis, we proof the advantages of tier‐based approach and the bound for the selection of tiered boundary. The simulation results also verify that our scheme can achieve superior performance than traditional schemes regarding no bandwidth reserving, fixed bandwidth reserving, and bandwidth borrowing in sectored cellular networks when performance metrics are measured in terms of the connection dropping probability (CDP), connection blocking probability (CBP), and bandwidth utilization (BU). Copyright © 2008 John Wiley & Sons, Ltd.     

综合业务接入ATM网络的资源共享

本文提出了一种在ATM网络中传输综合业务的资源共享方案,该方案中,每一VP只传输一类业务,并根据各业务的带宽,各VP传输的业务量和链路的剩余带宽动态分配各个VP占用的宽带,在保证各类业务呼损率的前提下,可获得提高传输效率和降低节点归一化处理负荷的良好折衷。本文还引入了迟滞和资源预留两个概念,并分析了它们对呼损率和节点的归一化处理负荷的影响,最后给出了详细的理论分析和计算机模拟结果。     

A dynamic transmission capacity allocation scheme for wired/wireless ATM networks

The previous research on administration of the transmission capacity in the wired/ wireless ATM networks only focuses on wired part or wireless part. There are very few people do the work extending to the links associating with handoff in the whole network. This paper develops the algorithms of transmission capacity administration on the link connecting the base station and base station controller (including the air interface of the base station) and the VPs among the base station controllers in the wired/ wireless ATM networks, which adapt to the traffic state of each service in every cellular cell to allocate (provision) transmission capacity and to reserve handoff guard capacity on these links, respectively. By simulating and analyzing the performance of the algorithm, it is found that it does well for the multimedia communication in which the transmission capacity requirement of each service may be widely different, so that the network bandwidth resource can be used efficiently.     

A dynamic call admission scheme for VBR traffic in ATM networks

The role of call admission control (CAC) in high-speed networks is to maintain the network utilization at a high level, while ensuring that the quality of service (QoS) requirements of the individual calls are met. We use the term static CAC to describe schemes that always allocate the same bandwidth to a specific group of multiplexed calls, independent of the other traffic sharing the link. Dynamic CAC, on the other hand, denotes a scheme in which the bandwidth allocation to a group of calls sharing a queue is influenced by the traffic in other queues destined for the same outgoing link. We propose a generic dynamic call admission scheme for VBR and ABR traffic whose aim is to reduce the blocking rate for VBR calls at the expense of a higher blocking rate for ABR calls. Our scheme is generic because it builds up on a pre-existing static scheme, e.g., one based on a simple notion of effective bandwidth. Our simple approach results in a significant reduction of the blocking rate for VBR traffic (several orders of magnitude), if the bandwidth requirements of a single call are a reasonably small fraction of the link capacity. At the same time, the deterioration of service for ABR traffic can be contained. This revised version was published online in August 2006 with corrections to the Cover Date.     

无线ATM接入技术在军事通信中的应用

无线ATM技术由于吞吐量大、支持综合业务等一系列优点,在军事通信领域得到了广泛的应用,目前的发展方向是把ATM应用于军用移动通信,在战场上实现运动中的语音、数据、多媒体等业务的实时传输.本论文利用现有成熟的无线ATM接入技术和蜂窝移动网技术,结合现代高技术信息作战对军事通信的要求,研究宽带无线接入在军事通信网中的应用.     

A synchronous duty-cycled reservation based MAC protocol for underwater wireless sensor networks

To design an energy-efficient Medium Access Control (MAC) protocol for the Underwater Wireless Sensor Networks (UWSNs) is an urgent research issue since depleted batteries cannot be recharged or replaced in the underwater environment. Moreover, the underwater acoustic channels are affected by hindrances such as long propagation delay and limited bandwidth, which appear in the design of the MAC protocol for the UWSNs. The available MAC protocols for the terrestrial wireless sensor networks exhibit low performance in energy efficiency, throughput and reliability in the UWSNs, and cannot be used in the UWSNs directly because of their unique characteristics. This paper proposes a synchronous duty-cycled reservation-based MAC protocol named Ordered Contention MAC (OCMAC) protocol. The basic mechanism of this protocol is to schedule data transmission by transmitters through the scheduling of Ready To Send (RTS) frames. The protocol eliminates the possible collision during data transmission and improves communication efficiency. The paper analyzes the performance in energy efficiency, throughput and reliability of the protocol by modeling the queuing behavior of OCMAC with a Markov Chain process. Furthermore, the analytical model is validated through a simulation study. The analysis results demonstrated that while providing good throughput and reliability, OCMAC can achieve energy saving.     

Schemes for mobility management of wireless ATM networks

The growing fields of wireless networks and asynchronous transfer mode (ATM) are merging to form wireless ATM networks. This paper addresses dynamic bandwidth allocation, connection admission procedures, routing, and location management strategies in wireless ATM. More precisely, we investigate the issue of extending the private Network to Network Interface, PNNI, and protocols to support mobility. PNNI‐based hierarchical routing, hand‐off, location management and routing schemes are proposed to integrate wireless capabilities into ATM networks. These schemes provide fast and efficient hand‐off connection processing mechanism and a reduction in the connection disruption time during a connection hand‐off session. They also provide a predictable resource requirement of the mobile system during its connection. During a connection hand‐off, misrouted cells can be re‐routed to their destinations. This substantially reduces the overhead due to end‐to‐end re‐transmissions invoked at higher layers. An analytical model is developed to illustrate the hand‐off algorithm. Copyright © 1999 John Wiley & Sons, Ltd.     

有/无线ATM网的组播选路算法

本文提出一种组播选路算法,在组播连接路由树的代价函数中计入了移动成员的越区切换发生概率,使为移动成员服务的接入节点（ＡＰ）尽可能成为组播路由树的树叶节点。当移动成员发生越区切换以后,可减去原来为之服务的ＡＰ和相应的树枝通道链路,从而保证了网络资源得以有效地利用。数值模拟分析的结果表明,我们提出的算法达到了这一目的。     

无线传感网混合类MAC协议研究综述

在无线传感网( WSN)体系结构中,介质访问控制( MAC)协议负责调配网络中节点的信道接入,具有保障网络高效通信的重要作用。混合类MAC 协议综合了竞争类MAC 协议以及调度类MAC协议的特点,在融合两种机制的优点的同时克服其缺点,为无线信道资源的分配提供了更加灵活和全面的策略。首先概述了无线传感网MAC协议设计要点及分类,然后重点分析了无线传感网中经典的混合类MAC协议及国内外前沿的研究进展,并进一步归纳对比了各协议运行机制、性能及不足,得出混合类MAC协议的应用相关性及差异性的结论,最后总结了无线传感网混合类MAC协议研究现状并指出了未来的研究重点,以期为相关领域的研究人员提供参考。     

A linear‐based trunk reservation routing algorithm for ATM networks

In this paper a practical routing algorithm is proposed that increases the network throughput irrespective of the network traffic load. Its effectiveness is based on an efficient cost function which achieves a successful trade‐off between the use of the minimum‐hop routes and the application of the load‐balancing concept. Moreover, it employs the known Trunk Reservation notion according to a probability that increases linearly with the traffic load. This results in an effective compromise of the performance of the algorithm between light and heavy traffic loads. Finally, its simplicity and its suitability for a real‐time application render it as an efficient routing algorithm for ATM networks. Copyright © 1999 John Wiley & Sons, Ltd.     

自适应动态分组预约多址协议

该文提出一种基于自适应传输的动态分组预约多址协议。用来在业务量和信道都时变的环境下，灵活、高效地支持需要各种不同质量需求的无线多媒体通信。在这个方案中根据特点不同将空闲时隙分为“自由”、“长可用”或“短可用”三种，以“自由”时隙数目作为系统实时业务量的判决标准，根据系统实时业务量分别采用不同的多址接入策略，将长数据和短数据安排在语音传输的空隙传输，同时采用了自适应传输体制来进一步提高系统性能。仿真实验表明，通过合理选择系统参数，可以有效地增加系统总容量。     

An agent-based signaling architecture for supporting mobility in radio ATM networks

This paper presents a signaling architecture for supporting mobility in radio asynchronous transfer mode (ATM) networks. A new concept of mobile software agent, known as ‘representative’, is used for insulating fixed network entities from the effects of user mobility. It is shown that, depending on the physical locations of the mobile terminals, their representatives can be used for distributing the mobility management load within the fixed backbone network. This paper describes a location and a representative management scheme followed by a novel connection caching strategy which is used for implementing a family of low-latency and scalable ATM connection handovers. A prototype implementation of the proposed architecture and the associated experimental results are also presented to demonstrate the feasibility and performance of this agent-based signaling scheme. ©1997 by John Wiley & Sons, Ltd.     

A novel adaptive hybrid ARQ scheme for wireless ATM networks

This paper describes the design and performance of a novel adaptive hybrid ARQ scheme using concatenated FEC codes for error control over wireless ATM networks. The wireless links are characterized by higher, time‐varying error rates and burstier error patterns in comparison with the fiber‐based links for which ATM was designed. The purpose of the hybrid ARQ scheme is to provide a capability to dynamically support reliable ATM‐based transport over wireless channels by using a combination of our ARQ scheme (called SDLP) and the concatenated FEC scheme. The key ideas in the proposed hybrid ARQ scheme are to adapt the code rate to the channel conditions using incremental redundancy and to increase the starting code rate as much as possible with the concatenated FEC, maximizing the throughput efficiency. The numerical results show that our proposed scheme outperforms other ARQ schemes for all SNR values. This revised version was published online in July 2006 with corrections to the Cover Date.     

Improved channel‐aware MAC protocols for wireless local area networks

This paper studies the fading properties of the communication channel assumed in wireless local area networks (WLANs) and devises efficient channel‐aware protocols for the distributed coordination function (DCF) and the point coordination function (PCF), the two modes of communication defined in the IEEE standard for WLAN. Our simulations show that the proposed PCF protocol improves the channel capacity usage up to 14% and the proposed DCF protocol improves the channel capacity up to 90%, when compared with standard IEEE 802.11 implementations, depending on the loss rate and temporal characteristics of the wireless channel. The proposed protocols introduce minimum computational overhead. We also show that, compared with standard DCF protocol defined in IEEE 802.11, the proposed DCF protocol can lower the SNR requirements for a given packet error rate thus potentially extending the battery life of portable devices that use WLAN.. Copyright © 2004 John Wiley & Sons, Ltd.     

A bandwidth assignment algorithm on a satellite channel for VBR traffic

Variable bit rate (VBR) video is currently by far the most interesting and challenging real-time application. A VBR encoder attempts to keep the quality of video output constant and at the same time reduces bandwidth requirements, since only a minimum amount of information has to be transferred. On the other hand, as VBR video traffic is both highly variable and delay-sensitive, high-speed networks (e.g. ATM) are generally implemented by assigning peak rate bandwidths to VBR video applications. This approach may, however, be inefficient in a satellite network based on a TDMA scheme. To overcome this problem, we have designed a demand assignment satellite bandwidth allocation algorithm in TDMA, named V2L-DA (VBR 2-Level Demand Assignment), which manages the VBR video traffic according to a dynamic bandwidth allocation algorithm. In this paper we discuss how to tune the proposed algorithm in order to optimize network utilization when MPEG-1 VBR video traffic is being transmitted. Our results indicate that most of the time only 40% of the peak rate bandwidth is needed to satisfy the VBR source, so the remaining 60% of the peak rate bandwidth can be used to transmit the datagram traffic queued in the network stations. © 1997 John Wiley & Sons, Ltd.