An approximate protocol analysis with performance optimization for WDM networks

In this study, our main goal is to investigate the performance optimization conditions for WDM networks. We introduce a network architecture of passive star topology that uses a Multi-channel Control Architecture (MCA) to avoid both the data channels and the receiver collisions. Especially, we propose a synchronous access scheme that exploits the propagation delay parameter in order to assign the data channels to the stations for successful data packet transmission. Thus, we achieve effective bandwidth utilization. An approximate analysis based on Poisson statistics is developed in order to explore the performance measures optimization. Finally, extensive comparative study is given for various stations populations and number of MCA channels.     

An approximation and its applications in wireless networks performance analysis

In the literature, there are two common assumptions for the tele‐traffic parameter in analyzing the wireless network performance, that is, the tele‐parameter follows a specific probability density function (pdf) and additionally the pdf exists closed‐form Laplace Transform (LT). However, taking into account the cell irregular shape, the specific pdf may be unavailable while only the measured statistical moments are available. Moreover, the pdf function may not exist a closed‐form LT, for example, lognormal distribution function. In this paper, based on the Central Limit Theorem and hyper‐Erlang universal approximation property, we propose an approximation method applicable in the situations when only the statistical moments are available or LT of pdf does not exist. We then employ the technique in diverse applications, including the performance analysis of wireless network and the cost evaluation of mobility management. Extensive numerical examples demonstrate the good approximation capability to the exact formula and the simulation results. Copyright © 2006 John Wiley & Sons, Ltd.     

A reservation-based multicast protocol for WDM optical star networks

In this paper, we present a reservation-based medium access control (MAC) protocol with multicast support for wavelength-division multiplexing networks. Our system is based on the single-hop, passive optical star architecture. Of the available wavelengths (channels), one channel is designated as a control channel, and the remaining channels are used for data transmission. Each node is equipped with a pair of fixed transceiver to access the control channel, and a fixed transmitter and a tunable receiver to access data channels. For easy implementation of the protocol in hardware and for precisely computing the protocol's processing overhead, we give a register-transfer model of the protocol. We simulate the protocol to study its throughput behavior, and present its analytic model. For a node to be able to send data packets in successive data slots with no time gap between them, in spite of the situation that the protocol's execution time may be longer than data transmission time, we propose the idea of multiple MAC units at each node. Unicast throughput of our protocol reaches the theoretically possible maximum throughput for MAC protocols with distributed control, and the multicast throughput is at least as good as, and even better than, those delivered by existing MAC protocols with distributed control.     

Multiuser diversity with capture for wireless networks: protocol and performance analysis

In a wireless network, with the aid of rate adaptation, multiuser diversity can be exploited by allowing the mobile user with the best channel to use the channel. However, the overhead that results from polling mobile stations to obtain channel state information (CSI) in large networks can outweigh the multiuser diversity gain. In this paper, we propose a wireless medium access control protocol, namely multiuser diversity with capture (MDC), which explicitly employs the capture effect to obviate the overhead problem. We analyze the good put performance of MDC and compare it with the medium access diversity (MAD) scheme proposed in the literature. Our results show that MDC is effective in networks with radio receivers possessing reasonably good capture properties and in networks where the number of mobile stations is reasonably large.     

An effective method for blocking performance analysis of WDM all-optical networks

We propose a rational approximation (RA)-based algorithm to perform the blocking analysis of circuit-switched all-optical networks. Our algorithm can be applied to large networks with various topologies and routing and wavelength assignment algorithms. It can be applied to optical networks with either full, sparse, or no wavelength conversion. We also propose fixed-path wavelength assignment algorithms for networks with balanced and unbalanced traffic.     

收缩原理在通信网性能分析中的应用

收缩原理是大偏差理论的重要组成部分。在通信网中可利用收缩原理由通信系统的输入得到与通信网的性能有关的事件的统计特性。本文给出了利用收缩原理分析通信网性能的应用框架，详细说明了该框架的应用步骤。最后举例说明了利用收缩原理分析通信网性能的优越性。     

WDM applications in broadband telecommunication networks

Network applications of multichannel wavelength-division multiplexing (WDM) techniques are considered. The photonic technologies that will be critical to future systems using WDM are reviewed. Both interoffice and subscriber loop architectures that utilize the unique properties of WDM to achieve important advantages over more traditional network designs are presented. Several experimental demonstrations that illustrate how these architectures can be realized with currently available components are described     

Multifrequency lasers and applications in WDM networks

The current status and applications of multifrequency lasers (MFL) are reviewed. An MFL consists of an array of N optical amplifiers monolithically integrated with a 1×N optical multiplexer. The laser provides the functionality of N independent lasers whose optical wavelengths are precisely locked together by the common intracavity optical multiplexer. The design of an MFL together with its fundamental characteristics are discussed, and state-of-the-art results are shown. The functionality of an MFL is compared to that of an integrated DFB array. Finally, we show some applications of single-wavelength tunable transmitters and multiwavelength transmitters     

A scalable synchronization protocol for large scale sensor networks and its applications

Synchronization is considered a particularly difficult task in wireless sensor networks due to its decentralized structure. Interestingly, synchrony has often been observed in networks of biological agents (e.g., synchronously flashing fireflies, or spiking of neurons). In this paper, we propose a bio-inspired network synchronization protocol for large scale sensor networks that emulates the simple strategies adopted by the biological agents. The strategy synchronizes pulsing devices that are led to emit their pulses periodically and simultaneously. The convergence to synchrony of our strategy follows from the theory of Mirollo and Strogatz, 1990, while the scalability is evident from the many examples existing in the natural world. When the nodes are within a single broadcast range, our key observation is that the dependence of the synchronization time on the number of nodes N is subject to a phase transition: for values of N beyond a specific threshold, the synchronization is nearly immediate; while for smaller N, the synchronization time decreases smoothly with respect to N. Interestingly, a tradeoff is observed between the total energy consumption and the time necessary to reach synchrony. We obtain an optimum operating point at the local minimum of the energy consumption curve that is associated to the phase transition phenomenon mentioned before. The proposed synchronization protocol is directly applied to the cooperative reach-back communications problem. The main advantages of the proposed method are its scalability and low complexity.     

A high-performance message prioritization and scheduling protocol for WDM star networks

A high-performance Efficient Message Prioritization and Scheduling (EMPS) protocol, for intelligent message scheduling in Wavelength-Division Multiplexing (WDM) star networks is introduced. The performance of the well-known EATS and MSL schemes is noticeably degraded in practical networks with non-uniform destinations and non-negligible transceiver tuning latencies. Under these realistic conditions, it is common that two or more messages with the same destination have to be scheduled consecutively or at close times. In most cases, this brings about some performance penalty, owing to the delayed availability of the destination’s receiver for the second (and beyond) of the consecutive messages. As the frequency of such occurrences increases, the performance degradation of the existing schemes becomes more prominent. EMPS is proposed to deal with this problem. It simultaneously considers multiple messages from different transmitting nodes and gives priority to messages intended for the least used destinations each time. By balancing the offered load in this way, EMPS minimizes the probability of having to schedule two or more messages with the same destination consecutively or at close times. Additionally, by incorporating the Minimum Scheduling Latency algorithm for channel selection, the protocol also minimizes the actual performance penalty incurred, when scheduling of consecutive messages with the same destination cannot be avoided. Extensive simulations are carried out in order to study the performance of EMPS and compare it to other efficient schemes under various conditions. The simulation results show that the proposed protocol always brings about a significant performance improvement.     

A slotted access control protocol for metropolitan WDM ring networks

In this study we focus on the serious scalability problems that many access protocols for WDM ring networks introduce due to the use of a dedicated wavelength per access node for either transmission or reception. We propose an efficient slotted MAC protocol suitable for WDM ring metropolitan area networks. The proposed network architecture employs a separate wavelength for control information exchange prior to the data packet transmission. Each access node is equipped with a pair of tunable transceivers for data communication and a pair of fixed tuned transceivers for control information exchange. Also, each access node includes a set of fixed delay lines for synchronization reasons; to keep the data packets, while the control information is processed. An efficient access algorithm is applied to avoid both the data wavelengths and the receiver collisions. In our protocol, each access node is capable of transmitting and receiving over any of the data wavelengths, facing the scalability issues. Two different slot reuse schemes are assumed: the source and the destination stripping schemes. For both schemes, performance measures evaluation is provided via an analytic model. The analytical results are validated by a discrete event simulation model that uses Poisson traffic sources. Simulation results show that the proposed protocol manages efficient bandwidth utilization, especially under high load. Also, comparative simulation results prove that our protocol achieves significant performance improvement as compared with other WDMA protocols which restrict transmission over a dedicated data wavelength. Finally, performance measures evaluation is explored for diverse numbers of buffer size, access nodes and data wavelengths.     

Traffic grooming in mesh WDM optical networks - performance analysis

Traffic grooming is an important task in interworking between the wavelength-division multiplexing (WDM) optical network that supplies "pipes" at the wavelength granularity, and the attached client networks that usually require connections of subwavelength granularity. The focus of this paper is to conduct performance analysis of grooming dynamic client traffic in WDM optical networks with a mesh topology. This paper first briefly introduces the traffic grooming problem in WDM optical networks and the issues related to performance analysis. It then develops two link blocking models, an exact model based on the stochastic knapsack problem and an approximation model based on an approximate continuous time Markov chain (CTMC). The end-to-end performance analysis is conducted using the reduced load approximation. The result obtained from analysis is shown to be accurate compared with the numerical result obtained from simulation.     

The slow start power controlled MAC protocol for mobile ad hoc networks and its performance analysis

We propose and evaluate the performance of a new MAC-layer protocol for mobile ad hoc networks, called the Slow Start Power Controlled (abbreviated SSPC) protocol. SSPC improves on IEEE 802.11 by using power control for the RTS/CTS and DATA frame transmissions, so as to reduce energy consumption and increase network throughput and lifetime. In our scheme the transmission power used for the RTS frames is not constant, but follows a slow start principle. The CTS frames, which are sent at maximum transmission power, prevent the neighbouring nodes from transmitting their DATA frames at power levels higher than a computed threshold, while allowing them to transmit at power levels less than that threshold. Reduced energy consumption is achieved by adjusting the node transmission power to the minimum required value for reliable reception at the receiving node, while increase in network throughput is achieved by allowing more transmissions to take place simultaneously. The slow start principle used for calculating the appropriate DATA frames transmission power and the possibility of more simultaneous collision-free transmissions differentiate the SSPC protocol from the other MAC solutions proposed for IEEE 802.11. Simulation results indicate that the SSPC protocol achieves a significant reduction in power consumption, average packet delay and frequency of RTS frame collisions, and a significant increase in network throughput and received-to-sent packets ratio compared to IEEE 802.11 protocol.     

Comparative analysis of the traffic performance of fiber-impairment limited WDM and hybrid OCDM/WDM networks

Optical code-division multiplexing (OCDM) is a technique that is currently generating considerable research interest. This paper analyzes and compares the traffic performance of wavelength-division multiplexing (WDM) and hybrid OCDM/WDM-based optical networks. The analysis considers the influence of the limitations of fiber-induced signal impairments on traffic performance and comparisons are performed for an example network utilizing different standardized fiber types. Furthermore, comparisons of traffic performance are also made between different lightpath schemes used in WDM and OCDM/WDM networks. The analysis results show that the OCDM/WDM lightpath schemes significantly outperform the WDM lightpath schemes for given blocking probability criteria. Moreover, the analysis indicates that fiber nonlinearity (which limits the minimum channel spacing) affects the traffic performance more severely compared to fiber dispersion (limits code cardinality).     

一种基于捕获的扩频分组无线网MAC层协议及其性能分析

在分组接入过程中,当每个用户终端以随机竞争的方式获得所需的频谱资源时,会引起用户间的冲突和资源的浪费,造成系统性能的降低。本文引入了一种基于捕获的接入方法,当一个时隙中存在多个干扰分组时,该方法仍有捕获到某个分组的可能,该方法在系统高负载的情况下能有效地利用资源。性能分析和计算结果表明,基于捕获的方法改善了系统的性能。     

Metro WDM networks: performance comparison of slotted ring and AWG star networks

Both wavelength-division-multiplexing (WDM) networks with a ring architecture and WDM networks with a star architecture have been extensively studied as solutions to the ever increasing amount of traffic in the metropolitan area. Studies typically focus on either the ring or the star and significant advances have been made in the protocol design and performance optimization for the WDM ring and the WDM star, respectively. However, very little is known about the relative performance comparisons of ring and star networks. In this paper, we conduct a comprehensive comparison of a state-of-the-art WDM ring network with a state-of-the-art WDM star network. In particular, we compare time-slotted WDM ring networks (both single-fiber and dual-fiber) with tunable-transmitter and fixed-receiver (TT-FR) nodes and an arrayed-waveguide grating-based single-hop star network with tunable-transmitter and tunable-receiver (TT-TR) nodes. We evaluate mean aggregate throughput, relative packet loss, and mean delay by means of simulation for Bernoulli and self-similar traffic models for unicast traffic with uniform and hot-spot traffic matrices, as well as for multicast traffic. Our results quantify the fundamental performance characteristics of ring networks versus star networks and vice versa, as well as their respective performance limiting bottlenecks and, thus, provide guidance for directing future research efforts.     

Photonic packet WDM ring networks architecture and performance

This article reviews various WDM ring architectures and pays special attention to their implementation in the metropolitan environment. A number of possible network architectures as well as protocols are reviewed. The article also proposes and analyses a WDM slotted-ring network architecture with nodes that use one fixed transmitter and fixed receivers. Used as a metropolitan access network, it is shown through simulation how a simple slotted MAC protocol can be implemented in this network to achieve efficient bandwidth utilization. Throughput, delay and packet dropping probability results are presented under Poisson and self-similar traffic.     

可调谐光滤波器及其WDM应用

可调光滤波器技术是波分复用系统的关键技术之一,它对于发展全光网络具有极其重要的作用。文章介绍了几种具有潜力的可调谐光滤波器,包括：光纤光栅可调谐滤波器、声光可调滤波器、阵列波导光栅滤波器和光子晶体滤波器等,并分析了它们的工作原理及其在波分复用系统中的应用。     

Acoustooptic tunable filters in narrowband WDM networks: systemissues and network applications

The system issues and network applications of acoustooptic tunable filters (AOTFs) are discussed. AOTFs are thought to be attractive system components in dense wavelength-division multiplexed (WDM) networks because of their broad continuous electronic wavelength tunability and narrow filter bandwidth. Their unique multiwavelength filtering capability adds a greater dimension of flexibility to network design. The characteristics of the AOTF are reviewed from a system viewpoint and the performance and capabilities of bulk-devices, integrated-optic devices, and fiber-based devices are discussed and compared. Three network applications using the acoustooptic tunable filters are described. The first application is as wavelength-tunable receivers or taps for local users in a subscriber loop distribution network. The second is as multiwavelength tunable receivers in a broadcast local-area cross-connect for packet communication with very-high-throughput data rate. The third is as wavelength-selective space-division switch fabric for routing and cross-connect between central offices. Future prospects and various issues for future research are also discussed     

Policy-driven automated reconfiguration for performance management in WDM optical networks

A key feature of optical networks based on WDM technology is the ability to optimize the configuration of optimal resources (i.e., wavelengths) with respect to a particular traffic demand. In the broadcast architecture, this involves the assignment of wavelengths to logical links, while in the optically switched architecture it additionally involves the routing of all-optical data paths known as lightpaths. This survey article is concerned with the problem of automatically updating the configuration of an optical network to accommodate changes in traffic demand, which entails making a reconfiguration policy decision, selecting a new configuration and migrating from the current to the new configuration. Existing solutions are classified according to their algorithmic properties, and compared on the basis performance, computational cost, and flexibility. Finally, open problems and research directions are discussed.