Performance evaluation of a buffer-based CSMA/CD protocol for single channel optical Ethernet LAN

Using CSMA/CD, Ethernet suffers capture effect that makes it unsuitable for supporting real-time multimedia traffic. It does not guarantee delay bound and behaves poorly under heavy load conditions, leading to excessive delay, throughput degradation and packet loss because of excessive collisions. Aim of this paper is to increase throughput and reduce average packet transfer delay of CSMA/CD-based LAN by reducing collisions and eliminating packet loss. Here, each user has a finite buffer capacity that helps to reduce collisions and Ethernet capture effect. At the same time, to eliminate packet loss, a new special-jamming signal is used. The network performance in terms of throughput, average packet transfer delay and percentage of collision based on the proposed protocol shows significant improvements. Throughput is increased more than 10% whereas average packet transfer delay and percentage of collision are reduced to less than 1.5 ms and 3%, respectively, compared to conventional protocol.     

1-persistent DUAL channel local area network for integrated voice and data application

It is a well-known fact that the carrier sense multiple access with collission detection (CSMA/CD) protocol would suffer from throughput degradations and long packet delays at heavy loads due to excessive collisions and retransmissions, and thus is not suitable for voice/data integration. Recently, a new protocol called carrier sense multiple access with time-split collision detection and split channel reservation (CSMA-TCD-SCR) has been proposed¹ to improve the channel throughput of CSMA/CD protocol by splitting the common channel into dual channels, i.e. one for data transfer and the other for reservation. It has been shown that the CSMA-TCD-SCR protocol improves the channel throughput and stability performance significantly.¹ In this paper, we propose a 1-persistent dual-channel LAN (1P-DC-LAN) protocol with the tree algorithm for reservation, which is an extension of the CSMA-TCD-SCR protocol, for voice/data integration applications. Through approximate analytical modelling and computer simulations, it has been demonstrated that the 1P-DC-LAN protocol exhibits nearperfect scheduling throughputs for data transmission and highly bounded voice packet delays. In addition, the results were compared with IEEE 802.3 CSMA/CD and twin-channel CSMA/CD.     

Reservation CSMA/CD: a multiple access protocol for LAN's

A multiple-access protocol for local area networks is described. It is basically a hybrid of carrier-sense multiple access with collision detection (CSMA/CD) and the broadcast recognizing access method (BRAM). CSMA/CD, which is contention-based, works well under light traffic, but message collisions degrade system performance when the channel becomes heavily loaded. BRAM, which is collision-free, has no longer delays at low load, but its efficiency improves as the load increases. Performance models are developed for the hybrid protocol and for the Ethernet protocol, a proven commercial implementation of CSMA/CD-type protocols. It is found that the hybrid protocol gives better performance for a wide range of scenarios     

QL－PAUSE：基于队列长度的PAUSE算法

以太网是目前使用最为广泛的局域网技术，由于采用了冲突检测和随机后退的MAC协议，基于CSMA／CD的半双工以太网不需要采用特殊的流量控制技术。随着快速以太网和以太网交换机的出现，如何有效管理全双工环境下以太网交换机以及网络的带宽资源成为日益突出的问题。该文针对IEEE定义的PAUSE操作，提出了基于队列长度的PAUSE（QL－PAUSE）算法，并通过仿真和分析证明该方法可以简洁有效地实现全双工以太网中的流量控制。     

基于CSMA/CD的教学实验的设计与实现

设计并实现了一种适用于教学的基于CSMA／CD机制的实验,重点给出了CSMA／CD机制的原理以及与此相关的信道共享技术、早期冲突、晚期冲突、以太网捕获等。实验界面知识点丰富,有助于学生掌握上述知识要点,在教学实践中获得了很好的效果。     

A load awareness medium access control protocol for single‐hop wireless ad hoc networks

A contention‐based wireless ad hoc medium access control (MAC) protocol, such as carrier sense multiple access with collision avoidance (CSMA/CA), has excellent efficiency when the system is light loaded. The main drawback of such protocols is their inefficiency and unbounded delay when the system load is heavy. On the other hand, a contention‐free MAC protocol, such as token passing, has a better and fair throughput when the system is heavy loaded. The main drawback of such protocols is their inefficiency when only a small amount of users want to transmit. In this paper, we propose a new load awareness single‐hop wireless ad hoc MAC protocol (which is called the LA protocol) that exploits the benefits of both contention‐based and contention‐free protocols. A contention‐based MAC protocol is used when the system is light loaded and a contention‐free one is used otherwise. Our LA protocol, which operates in a distributed fashion and is fully compatible with the IEEE 802.11 wireless local area network (WLAN) standard, can switch smoothly between the contention‐based protocol and the contention‐free one. Simulation results show that our protocol indeed extracts the better part of two kinds of protocols. Copyright © 2006 John Wiley & Sons, Ltd.     

带有网络分割的CSMA／CD技术

通过在ＣＳＭＡ／ＣＤ局域网中引入网络分割这一新概念，建立了以太网模拟模型，改善了ＣＳＭＡ／ＣＤ技术在重负载下的性能。     

Saturation performance analysis of directional CSMA/CA in mmWave WPANs

The millimeter‐wave (mmWave) band offers the potential for multi‐gigabit indoor wireless personal area networks (WPANs). However, there are problems such as the short wavelength and high propagation losses. In order to compensate for these, it is highly recommended to use directional antennas at the physical layer. In this paper, directional carrier sense multiple access/collision avoidance (CSMA/CA) is analyzed in IEEE 802.15.3c, a standard for mmWave WPANs, under a saturated environment. A Markov chain model is presented and analyzed for the no‐acknowledgment (No‐ACK) mode. For the analysis, the device interaction is considered using directional antennas over a shared channel. A Markov chain model is presented in which the features of IEEE 802.15.3c such as backoff counter freezing and the effects of using directional antennas are incorporated. The maximal number of frames that can be transmitted concurrently and successfully is derived by an algorithm, and the system throughput and the average transmission delay are obtained in the closed forms. Numerical results show that the effects of using directional antennas in CSMA/CA and the overall analysis are verified by the simulation. The obtained results illustrate the physical layer impact on the CSMA/CA medium access control protocol, and these insights can be helpful in developing a medium access control protocol for enhancing the performance of mmWave WPANs. Copyright © 2011 John Wiley & Sons, Ltd.     

互连的CSMA／CD局部网络的性能测量和分析

把两个具有碰撞深测载波检测多路存取协议的局部网络由桥接器和光纤链路互连起来，进行性能测量和研究。这种测量涉及内部网络和中间网络由桥接器和光纤链路互种配置上。对网络的吞吐量和延迟性能的分析表明，桥接网络的损失对负载的依赖关系很大。这种损失，在开始时最高的，然而，随着负载的增加却又减少，本文在提出问题以后，接着对桥接的ＣＳＭＡ／ＣＤ网络进行介绍。然后描述测量结果和进行性能分析；最后给出结论。     

Analytical modeling of MAC protocol in ad hoc networks

In ad hoc networks, CSMA/CA is a widely used MAC layer protocol. There has been considerable work on the performance evaluation of this protocol. But most work is confined to saturation performance of single‐hop ad hoc networks. In this paper, we employ a linear feedback model to evaluate the performance for CSMA/CA according to the Poisson distributed traffic in both single‐hop and multi‐hop ad hoc networks. To the best of our knowledge, this is the first attempt to analytically evaluate the performance for CSMA/CA protocol under a general assumption about the traffic. This paper also gives analytical results, showing the impact of RTS/CTS. Although RTS/CTS do add the overhead to the system, they become essential when either the hidden terminal problem is dominant, or the traffic is heavy, or the packet length is very large. This paper also shows that the performance degrades dramatically in multi‐hop ad hoc networks when the number of competing nodes increases, which implies that the scalability is still a major problem in ad hoc networks. To validate our analytical results, we have done extensive simulations, and it is observed that the simulation results match the analytical results very well. Copyright © 2006 John Wiley & Sons, Ltd.     

The 802.3z Gigabit Ethernet Standard

Considers standards development in the IEEE 802.3z Gigabit Ethernet Task Force, part of the IEEE 802.3 CSMA/CD Working Group. IEEE Std 802.3z-1998 was formally approved by the IEEE Standards Board on June 25th, 1998. IEEE Std 802.3z, extends the operating speed of the world's most popular local area network to 1 billion bits per second (1000 Mb/s) for interconnecting high-performance switches, routers, and servers in the backbone of local area networks. Maintaining backward compatibility with the over-100-million-node installed base of 10 Mb/s and 100 Mb/s was a key requirement     

Formal Specification and Model-Checking of CSMA/CA Using Finite Precision Timed Automata

1 Introduction Ani mportant activity within the engineering of com-munication andreal-ti me protocolsisto validate whethera given protocol functions as expected.Formal methodscan support this activity to a large extent . During thelast few years ,the formal specification and verificationof networking or telecommunication systems using for-mal tools[1 ~2]has attracted muchinterest fromacademiccommunity and industrial developers . In fact , therehave been some publications to discuss the specifi…     

Frame bursting: a technique for scaling CSMA/CD to gigabit speeds

Gigabit Ethernet supports the transmission of ordinary Ethernet frames at a data rate of 1000 Mb/s. Both flow-controlled full-duplex point-to-point links and half-duplex shared collision domains are included in the IEEE 802.3z draft standard. The parameters for half-duplex operation were chosen to align with the requirements of current generic building cabling standards, rather than to match the natural way that network size scales inversely with speed, so a star-wired single repeater topology with a maximum diameter of 200 m is permitted. Thus, gigabit Ethernet is the first time that the CSMA/CD medium access control algorithm has been applied to networks in which the round-trip propagation delay can be much greater than the transmission time for a minimum length frame. In this article, we describe the changes made to CSMA/CD that allow it to support large propagation delays without increasing the minimum frame length or changing its existing one-frame-at-a-time service interface. First, carrier extension is used to decouple the slot time from the minimum frame length, so the slot time can be increased without changing the Ethernet frame format. Second, frame bursting is used to reduce the overhead for transmitting small frames by allowing a host to transmit more than one frame without ever releasing control of the channel. Using simulation, we show that CSMA/CD with carrier extension and frame bursting operating on 1000 Mb/s links provides a significant performance increase over 100 Mb/s Fast Ethernet     

非均匀CSMA/CD光纤总线LAN的性能分析

作为尝试，以ＣＳＭＡ／ＣＤ光纤总线ＬＡＮ为对象，应用排队服务理论，对非均匀网络环境下的系统模型进行了数学解析和评价，推导出网络性能的重要参数利用率的计算公式，并通过ＧＰＳＳ仿真对数学模型进行了初步验证，获得了满意结果。     

一种实时以太网介质访问控制协议的时延性能分析

本文提出一种新的基于持续竞争的实时以太网介质访问控制协议,该协议能够保证实时信号的发送有确定的最大时延.在新协议下,如果检测到冲突,实时节点并不像普通以太网节点一样停止传输,而是坚持发送竞争信号,利用信道冲突通知非实时节点或者低优先级实时节点停止传输,把信道留给高优先级的实时节点.而且该协议与普通以太网介质访问控制协议兼容,这样实时节点与普通以太网节点能共存于同一网络系统中互相通信.文中详细描述了新型以太网介质访问控制协议,分析了实时信号的发送时延,理论分析和仿真均证明了该协议是可行和有效的.     

Exploiting the channel using uninterrupted collision‐free MAC adaptation over IEEE 802.11 WLANs

IEEE 802.11 wireless local area networks (WLANs) have reached an important stage and become a common technology for wireless access due to its low cost, ease of deployment, and mobility support. In parallel with the extensive growth of WLANs, the development of an efficient medium access control protocol that provides both high throughput performance for data traffic and quality of service support for real‐time applications has become a major focus in WLAN research. The IEEE 802.11 Distributed Coordination Functions (DCF/EDCA) provide contention‐based distributed channel access mechanisms for stations to share the wireless medium. However, performance of these mechanisms may drop dramatically because of high collision probabilities as the number of active stations increases. In this paper, we propose an adaptive collision‐free MAC adaptation. The proposed scheme prevents collisions and allows stations to enter the collision‐free state regardless of the traffic load (saturated or unsaturated) and the number of stations on the medium. Simulation results show that the proposed scheme dramatically enhances the overall throughput and supports quality of service for real‐time services over 802.11‐based WLANs. Copyright © 2013 John Wiley & Sons, Ltd.     

基于IEEE 802.15.4的CSMA/CA性能分析与研究

针对目前无线传感器网络所采用的IEEE802.15.4通讯协议进行研究及分析,包括了碰撞发生后的重传机制,也就是IEEE 802.15.4所使用的CSMA/CA算法,对于整体网络通信所造成的影响.经分析评估以及程序仿真后,将针对网络状况来找出CSMA/CA算法的三个重要参数对系统性能的影响.     

自适应p-持续CSMA/CD介质访问控制策略

针对IEEE802．3局域网介质随机访问协议l-持续CSMA／CD，在同一个冲突域内，它的性能在重荷载下有明显缺陷的问题，本文分析了p-持续CSMA／CD协议，提出了一种新的关于概率p的自适应算法。该算法基于对网络流量的分析，在OSI物理层通过信道信息量的在线实时检测，根据反馈控制的原理，在数据链路层动态地调整控制输入参数p，从而控制站点发送分组数据帧的行为，使信道处于最佳的传输状态，提高信道的效率。     

Broadband wireless infrared LAN architecture compatible withEthernet protocol

A wireless infrared (IR) LAN for the indoor environment is proposed which is compatible with the familiar CSMA/CD protocol used in Ethernet. Eye safe 140 Mbit/s transmission at only 5 mW transmitter power in a 20 m² cell is experimentally demonstrated     

Analysis of Priority R‐ALOHA (PR‐ALOHA) protocol

With the exception of required time synchronization, the Reservation‐ALOHA (R‐ALOHA) protocol is simple to implement and suitable for medium access control in ad hoc wireless networks. In this paper, we propose an innovative protocol, referred to as Reservation ALOHA with priority (PR‐ALOHA) that provides differentiated services on the basis of traffic priority. To date, the carrier sense multiple access/collision avoidance (CSMA/CA) protocol has been widely used for this purpose by employing an interframe spacing (IFS) for priority service, that is, nodes ready for packet transmissions are required to wait for an IFS amount of time, where a shorter IFS is used to gain faster access to the radio channel. However, sensing and collision avoidance mechanisms make CSMA/CA unsuitable for delay‐sensitive applications, that is, congested scenarios with high traffic. In contrast, the proposed PR‐ALOHA protocol may be considered a good candidate for such applications. In this paper, the performance of the PR‐ALOHA protocol is investigated analytically and by simulation. Its comparison with regular R‐ALOHA is also carried out. Modeling and simulation results of PR‐ALOHA show that PR‐ALOHA improves the performance of high‐priority traffic with limited effect on normal network traffic. Thus, PR‐ALOHA may be useful in vehicular communications, where traffic may be separated into emergency messages having high priority and multimedia messages having low priority. Copyright © 2013 John Wiley & Sons, Ltd.