Optical cascade star network--A new configuration for a passive distribution system with optical collision detection capability

A new fiber-optic passive network configuration with novel star couplers is reported. The new optical network configuration, an Optical Cascade Star Network, optimizes contradictory requirements for network system size and cable cost, and matches the actual layout in offices or factories. The star coupler is novel in that the optical signal does not return to the source terminals. This feature enables cascade connection of star networks, the use of simple repeaters for system extension, and the easy support of carrier sense multiple access with collision detection (CSMA/CD) bus access procedure. Experimental results obtained from novel star couplers, optical transceivers with (CSMA/CD) bus compatibility, and a total network system are also discussed.     

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。     

Implementation of a MAC-layer protocol (GIT-CSMA/CD) for industrialLAN's and its experimental performance

This paper describes the pilot implementation of a local area network by using a hybrid medium access control (MAC) layer protocol, called group implicit token-carrier sense multiple access with collision detection (GIT-CSMA/CD) developed for hard real-time industrial local area networks (LANs). This protocol outperforms standard CSMA/CD and token-passing protocols, as well as other hybrid protocols, in terms of mean and maximum packet delays versus throughput. Also, GIT-CSMA/CD offers bounded packet delay and a great degree of adaptation to the varying requirements imposed by the user applications. A seven-node pilot network was set up and its experimental performance evaluated. The implementation of the network node is based on the existing microcontroller technology (INTEL 80C3152 Communication Controller) and field programmable gate array (FPGA) logic (XILINX XC3190). The measurements carried out in real time on a 1-Mb/s LAN yielded reproducible results. The comparison between the experimental and the simulation results showed excellent agreement     

Performability evaluation of CSMA/CD and CSMA/DCR protocols undertransient fault conditions

This study compares the performability of the carrier sense multiple access protocol with collision detection (CSMA/CD) and a variant, the CSMA protocol with deterministic CD ( CSMA/DCR), which uses a deterministic collision-resolution, considering errors induced by transient faults. The long-term effect that transient faults can induce on the electronics which implement the protocols is considered. This is done using stochastic activity networks (SANs), a stochastic extension of Petri nets. SANs permits the detailed workings of CSMA/DCR and traditional CSMA/CD to be represented accurately, as well as the effects of transient faults     

The tone sense multiaccess protocols with partial collisiondetections (TSMA/PCD) for packet satellite communications

The tone sense multiaccess with partial collision detection (TSMA/PCD) protocol is particularly suitable for a packet satellite system serving an area with a dense population of earth stations. By incorporating a narrowband ground radio channel for broadcasting busy ones, the earth stations are able to avoid packet collisions by sensing for the absence of busy tones before transmitting packets. Partial collision detection capability can also be achieved. Single-tone TSMA/PCD gives 97% of the carrier-sense multiaccess with collision detection (CSMA/CD) throughput when N=10 tones are used, while for multitone and slot-by-slot announcement TSMA/PCD protocols only N=8 and N=2, respectively, are sufficient to drive the system to the CSMA/CD performance     

Finite Population CSMA/CD Networks

A continuous time Markov chain model of a nonpersistent carrier sense multiple access with collision detection (CSMA/CD) protocol is developed to determine the performance of finite population systems. The model allows a wide range of distributions for the length of packets and the lengths of the transmission detection and collision detection times. A stability measure for finite population asynchronous systems-the instantaneous expected drift-is developed. Performance calculations for many sample systems show that the following behavior is characteristic of these systems: a wide range of retransmission rates provides almost optimal performance; the instantaneous drift is a sensitive indicator of the stability characteristics of CSMA/CD networks; if high fixed retransmission rates are used, performance decays very rapidly when other network parameters cross critical thresholds. In addition, adaptive retransmission policies and the maximum length of a CSMA/CD cable network are found to be very sensitive to the distribution of the transmission detection time.     

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     

CSMA/CD with Deterministic Contention Resolution

This paper presents a novel media access protocol CSMA/CD with deterministic contention resolution (DCR) for a local area network. It usually operates as CSMA/CD, but once a collision occurs it resolves the collision using a kind of implicit token passing. An analysis was conducted on DCR performance characteristics based on simulation studies and in comparison to conventional CSMA/CD and implicit token passing. It was found that they were very satisfactory in terms of throughput, message delay, and delay standard deviation, these performance characteristics make DCR attractive as a media access protocol for combined voice and data traffic. It has also been shown that this protocol assures robustness against various kinds of transmission errors and station failures. A prototype of a local area network using this protocol has been developed. It consists of a pair of optical fiber buses to which each station is attached via a pair of directional couplers.     

The delay characteristics of CSMA/CD networks

A continuous-time Markov chain model of the CSMA/CD (carrier-sense multiple-access with collision detection) protocol is used to find its delay characteristics. For both random-service-order (RSO) and first-come-first-serve (FCFS) CSMA/CD networks, matrix-geometric methods are used to derive and/or compute the throughput-delay and caudal-characteristics curves, the distribution and variance of the delay, and the rate of decay of the tail of the delay distribution. These results can be used to determine the suitability of RSO and FCFS CSMA/CD networks in applications in which they must carry delay-sensitive data. This is illustrated by an example which shows the significant improvement obtained in the delay characteristics of a particular network when FCFS is used instead of RSO     

Novel collision detection technique for CSMA/CD based fibre-optic local area networks

A novel and simple collision detection technique for CSMA/CD based fibre-optic local area networks is reported. The method is suitable for both passive and active ring and star configured systems. All collisions are detected in ring networks. In star networks, approximately less than 1% of collisions, depending on the system parameters, cannot be detected.     

A simulation study of delay in multichannel CSMA/CD protocols

Simulation is used to estimate the performance of media access control (MAC) protocols derived from carrier-sense multiple access with collision detection (CSMA/CD), and operating in local area networks comprising several parallel broadcast channels. The influence of possible protocol and system alternatives on the network performance is discussed, based on results of the packet delay average, variance, mean square, coefficient of variation, and histogram, as well as the packet rejection probability due to lack of buffer space. The delay incurred by multipacket messages is estimated, comparing the single channel to the multichannel option. Numerical results indicate that the multichannel option provides reductions in both the packet delay average and variance, even when stations are only able to simultaneously receive from a subset of channels     

The CSMA/DM LAN protocol

We propose an extension of the classical CSMA/CD protocol that eliminates its three main drawbacks. The new protocol, called dual‐mode CSMA/CD (CSMA/DM), operates in two modes, light mode and heavy mode. The light mode of CSMA/DM is almost the same as the original CSMA/CD protocol and is primarily used when the LAN load is light. The heavy mode is a collision free mode and is applied when the LAN load is heavy. The proposed modification to CSMA/CD is minimal while performance gain is significant. CSMA/DM automatically switches between its two modes based on the observed LAN load. Under heavy mode, the monitor station in a CSMA/DM LAN allocates bandwidth to those busy stations without collisions. The newly added priority scheme in the heavy mode allows stations to reserve bandwidth for their high priority frames. Compared with the current collision‐free fast Ethernet and Gigabit Ethernet, CSMA/DM has the advantage of not needing any extra switches or hubs while maintaining comparable performance. Its priority scheme provides more flexibility on bandwidth distribution than in fast Ethernet and Gigabit Ethernet. It can also be easily adapted for high‐speed wireless LANs. More importantly, CSMA/DM should be a good alternative of the widely used CSMA/CA (collision avoidance) in mobile ad hoc networks (MANET) and sensor networks. Copyright © 2005 John Wiley & Sons, Ltd.     

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     

A passive star-configured optical local area network using carrier sense multiple access with a novel collision detector

This work describes design and theoretical performance of a passive star-configured multimode optical fiber local area network that employs carrier sense multiple access with collision detection (CSMA/CD). We introduce a novel collision detection method that uses collision sequences constructed from cyclic error-correcting codes and a sequence weight violation rule. Each transmitter has its own unique sequence and all sequences have identical Hamming weight. The collision detection sequence is inserted in each packet header. Our method enables detection of collisions subject to a wider dynamic range variation than competing methods proposed up to now and is extremely simple. The collision detector consists of a counter which estimates the Hamming weight of the received collision detection sequence. It works both for non-return-to-zero and Manchester coding. The collision detector is analyzed for an avalanche photodiode receiver. The general performance analysis is done both with Gaussian approximations and with method of moments. A dynamic range of 17 dB seems possible for a transmitter with an extinction ratio of 100 and a simple receiver with a fixed threshold. An explicit table of 56 collision detection sequences based on the Golay code is presented.     

A novel hidden station detection mechanism in IEEE 802.11 WLAN

The popular IEEE 802.11 wireless local area network (WLAN) is based on a carrier sense multiple access with collision avoidance (CSMA/CA), where a station listens to the medium before transmission in order to avoid collision. If there exist stations which can not hear each other, i.e., hidden stations, the potential collision probability increases, thus dramatically degrading the network throughput. The RTS/CTS (request-to-send/clear-to-send) frame exchange is a solution for the hidden station problem, but the RTS/CTS exchange itself consumes the network resources by transmitting the control frames. In order to maximize the network throughput, we need to use the RTS/CTS exchange adaptively only when hidden stations exist in the network. In this letter, a simple but very effective hidden station detection mechanism is proposed. Once a station detects the hidden stations via the proposed detection mechanism, it can trigger the usage of the RTS/CTS exchange. The simulation results demonstrate that the proposed mechanism can provide the maximum system throughput performance.     

Fiber optic LANs for the manufacturing environment

The physical layer requirements for local area networks (LANs) that satisfy the set of environmental requirements unique to factory automation applications are discussed. In many cases these requirements are best met with fiber-optic LANs compatible with the IEEE 802.3 (CSMA/CD) or 802.4 (token bus) network standards. Implementation of a passive fiber-optic star-coupler-based LAN is presented in terms of two simple fiber-optic system design rules. A number of applications of the passive star-coupler-technology LAN are briefly described to highlight the benefits of fiber optics as a data communication medium     

Passive optical star bus with collision detection for CSMA/CD-based local-area networks

A prototype 16-terminal passive star bus suitable for carrier sense multiple access with collision detection (CSMA/CD)-based fiber-optic local-area network is described. Operation is at 16 Mbit/s over optical path lengths of 600 m. The optical wavelength is 830 nm. A novel and simple collision detection method based on listening onto the bus is incorporated within the system. In addition, data is scrambled instead of Manchester encoded. The effect that scrambling has on the collision detection method, as well as on the detection of both the bus idle state and the beginning and end of data packets is examined in detail. The network efficiency is calculated taking into account the operation of the scrambler as well as the collision detection method.     

A multistage hierarchical distributed arbitration technique for priority-based real-time communication systems

ISO 11898 is a communication protocol based on the carrier sense multiple access with collision detection and arbitration on message priority (CSMA/CD+AMP) technique, which at present is largely used as a real-time network for industrial environments. Unfortunately, because of the peculiarities of the arbitration technique it adopts, it suffers from severe limitations on the maximum extension of the network, which cannot be overcome simply by means of improvements in the transceiver's technology as they depend on the limited propagation speed of the signals on the communication support. In this paper, a new kind of network is presented that features a behavior very similar to ISO 11898, but which achieves noticeably larger areas to be covered without having to reduce the bit rate. It relies on a tree topology and adopts a brand new multistage hierarchical distributed arbitration technique, which takes the increased propagation delays into account properly.     

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.     

A simple and versatile decentralized control for slotted ALOHA,reservation ALOHA, and local area networks

A simple, decentralized control for reducing the delays and stabilizing random-access channels is presented. The control, which is based on a computationally efficient recursive implementation of the minimum mean-squared error (MMSE) predictor of the channel backlog, applies to slotted ALOHA, to reservation ALOHA, and to local area networks (LANs) with carrier-sense multiple access (CSMA) or CSMA with collision detection (CSMA/CD) protocols. The MMSE predictor controller (MMSE-PC) can stabilize the slotted ALOHA for all traffic rates not exceeding e^-1, and it can achieve stable throughput arbitrarily close to one with finite delays in the reservation ALOHA and in LANs. Extensive simulation has shown that the MMSE-PC performs extremely well in all three random-access environments. For the implementation of the MMSE-PC in LANs, synchronization of transmissions is not required but it is required in slotted ALOHA and reservation ALOHA. The MMSE-PC has been implemented in hardware and tested in asynchronous LANs