SUCCESS-HPON: A next-generation optical access architecture for smooth migration from TDM-PON to WDM-PON

Optical access networks are considered to be a definite solution to the problem of upgrading current congested access networks to ones capable of delivering future broadband integrated services. However, the high deployment and maintenance cost of traditional point-to-point architectures is a major economic barrier. Current TDM-PON architectures are economically feasible, but bandwidth-limited. In this article we first discuss the possible role of WDM in access networks and investigate the associated issues. We then present the Stanford University Access Hybrid WDM/TDM Passive Optical Network (SUCCESS-HPON), a next-generation hybrid WDM/TDM optical access architecture that focuses on providing a smooth migration path from current TDM-PONs to future WDM-PONs. The first testbed for this architecture is described, along with the experimental results obtained, including feasibility of bidirectional transmission on the same wavelength on the same fiber for access networks and ONU modulation of upstream data on continuous waves provided by the OLT, eliminating the need for tunable components at the ONUs. The development of a second testbed and the issues it will address, including the implementability of the SUCCESS-HPON MAC protocol and scheduling algorithms, are also described.     

Scheduling in Optical WDM Networks Using Hidden Markov Chain Based Traffic Prediction

This paper presents the design and performance analysis of a predictor-based scheduling algorithm for optical wavelength division multiplexed (WDM) networks. WDM technology provides multiple, simultaneous and independent gigabit-per-second channels on a single fiber. A reservation-based multiple access control (MAC) protocol is considered here for a local area WDM network based on the passive star topology. The MAC protocol schedules reservation requests from the network nodes on the multiple channels. In previous work, we have presented an on-line scheduling algorithm for such a network. We have shown earlier that schedule computation time can significantly affect performance and the scheduling algorithms should be simple for better performance. In this work, we further improve system performance by using a hidden Markov chain based prediction algorithm. The objective here is to reduce the amount of time spent in computing the schedule by predicting traffic requests. Performance analysis based on discrete-event simulation, varying parameters such as number of nodes and channels is presented. The results show that the error of prediction is reasonable for most cases: more than 70% of the time, the error between actual request and predicted request is less than 20%. Network throughput is higher with the proposed prediction algorithm due to pipelining of schedule computation.     

多波长无源光接入网接入控制的分析研究

描述了基于多波长无源不接入网的（WDM-PON）的体系结构和数据信道非时隙化的接入控制协议，这种方式可大大简化以往复杂的同步功能。分析了在控制信道中选择接入协议的必要条件，这就使得控制信道接入协议的选择不再是盲目的。分析随机访问请求队列的延特性。     

SUCCESS: a next-generation hybrid WDM/TDM optical access network architecture

In this paper, the authors propose a next-generation hybrid WDM/TDM optical access network architecture called Stanford University aCCESS or SUCCESS. This architecture provides practical migration steps from current-generation time-division multiplexing (TDM)-passive optical network (PONs) to future WDM optical access networks. The architecture is backward compatible for users on existing TDM-PONs, while simultaneously capable of providing upgraded high-bandwidth services to new users on DWDM-PONs through advanced WDM techniques. The SUCCESS architecture is based on a collector ring and several distribution stars connecting the CO and the users. A semipassive configuration of the Remote Nodes (RNs) enables protection and restoration, making the network resilient to power failures. A novel design of the OLT and DWDM-PON ONUs minimizes the system cost considerably: 1) tunable lasers and receivers at the OLT are shared by all ONUs on the network to reduce the transceiver count and 2) the fast tunable lasers not only generate downstream data traffic but also provide DWDM-PON ONUs with optical CW bursts for their upstream data transmission. Results from an experimental system testbed support the feasibility of the proposed SUCCESS architecture. Also, simulation results of the first SUCCESS DWDM-PON MAC protocol verify that it can efficiently provide bidirectional transmission between the OLT and ONUs over multiple wavelengths with a small number of tunable transmitters and receivers.     

All-optical WDM multi-rings with differentiated QoS

This article considers all-optical WDM networks based on a slotted multichannel ring topology, where nodes are equipped with one fixed-wavelength receiver and one wavelength-tunable transmitter; and shows how to design very effective MAC protocols that provide packet-mode transport to multiple information flows with different QoS requirements. As an example, we describe SR3, a collision-free slotted MAC protocol which combines a packet scheduling strategy (called SRR), a fairness control algorithm (called MMR); and a reservation mechanism. SRR achieves an efficient exploitation of the available bandwidth, MMR guarantees fair throughput access to each node, and SR3, by permitting slot reservations, leads to tighter control on access delays, and can thus effectively support traffic classes with different QoS requirements     

An AWG-based WDM-PON architecture employing WDM/TDMA transmission for upstream traffic with dynamic bandwidth allocation

In this article, we examine a candidate architecture for wavelength-division multiplexed passive optical networks (WDM-PONs) employing multiple stages of arrayed-waveguide gratings (AWGs). The network architecture provides efficient bandwidth utilization by using WDM for downstream transmission and by combining WDM with time-division multiple access (TDMA) for upstream transmission. In such WDM-PONs, collisions may occur among upstream data packets transmitted simultaneously from different optical networking units (ONUs) sharing the same wavelength. The proposed MAC protocol avoids such collisions using a request/permit-based multipoint control protocol, and employs a dynamic TDMA-based bandwidth allocation scheme for upstream traffic, called minimum-guaranteed maximum request first (MG-MRF), ensuring a reasonable fairness among the ONUs. The entire MAC protocol is simulated using OPNET and its performance is evaluated in terms of queuing delay and bandwidth utilization under uniform as well as non-uniform traffic distributions. The simulation results demonstrate that the proposed bandwidth allocation scheme (MG-MRF) is able to provide high bandwidth utilization with a moderately low delay in presence of non-uniform traffic demands from ONUs.     

Optical burst switching: a viable solution for terabit IP backbone

Wavelength-division multiplexing has emerged as an important physical layer technology. Optical transmission provides a physical layer capable of carrying bits at the speed at the order of a gigabit per second. Optical burst switching is proposed to overcome the shortcomings of conventional WDM deployment, such as lack of fine bandwidth granularity in wavelength routing and electronic speed bottlenecks in SONET/SDH. We describe an architecture for IP network over the OBS WDM transmission core. The use of MPLS-type technique for forwarding data bursts and the inclusion of a medium access control layer between the optical (WDM) and IP layers are the key ingredients of the proposed architecture. In particular, the architecture is based on provisioning MPLS paths, also called label switched paths, of desired quality of service through the OBS WDM transmission core. The MAC layer performs various OBS-specific functions, such as burst assembly, burst scheduling, and offset setting/traffic shaping. While burst assembly and burst scheduling are relatively straightforward, we point out that the offset setting strategy has significant impact on the performance of IP network operating over OBS WDM core. We describe a shaping scheme to set the offset, an important system parameter for OBS, between the successive data bursts of a given data stream (label switched path) and their associated control packets. This scheme results in robust operation of the network and also facilitates traffic engineering. Guidelines are provided for implementing various IP QoS mechanisms in the optical backbone using OBS.     

波分复用网络中无接收碰撞的访问控制协议

本文针对可调发送机/可调接收机(TT/TR)的单跳波分复用网络提出多种无接收碰撞的访问控制协议,包括简单的无接收碰撞的数据传送策略TS和按最早发送时间进行优化的两种数据传送策略ETS、METS。计算机模拟结果说明优化的数据传送方案可以获得十分优良的网络性能,是WDM网络中行之有效的访问控制协议,尤其是METS协议能在可调光器件的调谐时间较长时依然保持非常突出的性能。对于采用任意调谐时间的可调光器件的WDM网络,METS具有相当重要的实用价值。     

Efficient protocols for multimedia streams on WDMA networks

This paper introduces a new approach to integrate different types of medium access control (MAC) protocols into a single wavelength-division-multiplexing (WDM) network system. The WDM network is based on a passive star coupler, and the purpose of integrating different MAC protocols is to efficiently accommodate various types of multimedia traffic streams with different characteristics and quality of service demands. Our integrated MAC protocol is termed multimedia wavelength-division multiple-access (M-WDMA). Three types of multimedia traffic streams are considered in this paper: constant-bit-rate traffic and two classes of variable-bit-rate traffic. Accordingly, three tunable transmitters and one fixed home channel receiver are used in the design of each WDM node. The transmitters transmit the three types of multimedia traffic streams in a pipeline fashion so as to overcome the tuning time overhead and to support parallel transmissions of traffic streams that emerge simultaneously. We further incorporate a dynamic bandwidth allocation scheme that dynamically adjusts the portions of bandwidth occupied by the three types of traffic streams according to their demands. Consequently the M-WDMA protocol achieves high utilization and efficiently adapts to the demands of the multimedia streams so as to guarantee their QoS. The performance of the M-WDMA is evaluated through a simple analytical model and extensive discrete-event simulations. It is shown that the M-WDMA can satisfy the QoS requirements of various mixes of multimedia traffic streams even under very stringent requirements. Moreover, we show that the M-WDMA outperforms conventional MAC protocols for WDM networks. As a result, we expect M-WDMA to be a good multimedia MAC candidate protocol for future-generation WDM networks.     

A slotted CDMA protocol with BER scheduling for wireless multimedianetworks

In future wireless multimedia networks, there will be a mixture of different traffic classes which have their own maximum tolerable bit error rate (BER) requirements. In this paper, a novel medium access control (MAC) protocol called wireless multimedia access control protocol with BER scheduling (in short form, WISPER) for CDMA-based systems is proposed. WISPER utilizes the novel idea of scheduling the transmission of multimedia packets according to their BER requirements. The scheduler assigns priorities to the packets, and performs an iterative procedure to determine a good accommodation of the highest-priority packets in the slots of a frame so that packets with equal or similar BER requirements are transmitted in the same slots. The proposed WISPER protocol has been validated using a software emulator on the cellular environment. Performance evaluation results based on the implementation are also included     

Architectures and technologies for high-speed optical data networks

Current optical networks are migrating to wavelength division multiplexing (WDM)-based fiber transport between traditional electronic multiplexers/demultiplexers, routers, and switches. Passive optical add-drop WDM networks have emerged but an optical data network that makes full use of the technologies of dynamic optical routing and switching exists only in experimental test-beds. This paper discusses architecture and technology issues for the design of high performance optical data networks with two classes of technologies, WDM and time division multiplexing (TDM). The WDM network architecture presented stresses WDM aware Internet protocol (IP), taking full advantage of optical reconfiguration, optical protection and restoration, traffic grooming to minimize electronics costs, and optical flow-switching for large transactions. Special attention is paid to the access network where innovative approaches to architecture may have a significant cost benefit. In the more distant future, ultrahigh-speed optical TDM networks, operating at single stream data rates of 100 Gb/s, may offer unique advantages over WDM networks. These advantages may include the ability to provide integrated services to high-end users, multiple quality-of-service (QoS) levels, and truly flexible bandwidth-on-demand. The paper gives an overview of an ultrahigh-speed TDM network architecture and describes recent key technology developments such as high-speed sources, switches, buffers, and rate converters     

一种有效的802.16MAC层QoS调度架构

首先简要分析了802.16协议中的服务质量(QoS)业务模型,然后提出了一种新颖的用于802.16媒体访问控制(MAC)层的QoS调度架构。该架构包括3个用于不同业务的调度器,1个用于信道补偿的调度器和1个映射(MAP)信息生成器。该调度架构能够有效地区分业务类型,保证不同类型业务的带宽请求,并且能很好地解决无线信道特殊性带来的调度问题。最后简单分析了该调度架构的优点。     

Employing Code Domain for Contention Resolution in Optical Burst Switched Networks With Detailed Performance Analysis

We propose the implementation of spectral-amplitude-coding optical code division multiple access (SAC-OCDMA) as a contention resolution technique in optical burst switched (OBS) networks. The new system architecture is presented in details where an all-optical methodology for cancelling multiple access interference is proposed. Performance evaluation of the proposed system in both MAC and optical layers is introduced where the overall burst error rate of the system is evaluated in three cases: full, partial, and no code conversion capabilities taking into account the receiver dark current, thermal, and shot noises at the egress nodes. Our results reveal that a considerable improvement in the performance of each core node in the system is achieved by using SAC-OCDMA instead of WDM in the optical layer underneath an OBS based MAC layer. We also conclude that a slight increase in the employed number of code converters enhances the overall system performance noticeably. Finally, optimum values for the number of codes, which lead to minimum overall burst error rate, are reached at different traffic conditions.     

QoS-oriented access control for 4G mobile multimedia CDMAcommunications

An efficient medium access control protocol with fair packet loss sharing packet scheduling is proposed for wireless code-division multiple access communications. The proposed MAC protocol exploits both time-division and code-division statistical multiplexing. The FPLS scheduler uses the information of traffic rate distribution and quality of service requirements to assign priorities to the users and determines an efficient combination of the packets for transmission in the time slots of each frame, so the number of the served users is maximized under the QoS constraints. Simulation results demonstrate the effectiveness of the FPLS scheduler, in comparison with other previously proposed scheduling algorithms     

Provision of quality of service in wireless fourth generation networks

A key word describing next generation wireless networks is ‘seamless’. Wireless fourth generation (4G) networks represent a set of new technologies that will enable seamless integration of various wireless access systems, while targeting to support various sophisticated and quality of service constraining applications, such as high‐speed data services and multimedia services. This paper first proposes an architecture for 4G networks. The most significant feature of this architecture is its flexibility, openness and ability to enable seamless handoff in a single logical overlay network composed of many heterogeneous access networks. A medium access control (MAC) protocol for basic access networks is then introduced. A generic scheduling scheme, named CS‐EDF (channel state‐earliest deadline first) and the details of an efficient handoff management method are also briefly introduced. The bandwidth utilization, handoff resources reservation, and scheduling scheme performances of the proposed schemes are discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Fair MAC protocol for optical ring network of wavelength-shared access nodes

In this paper, a WDM optical ring consisting of access nodes with fixed transmitter-n fixed receivers (FT—FR ⁿ ) is considered. As access nodes share a wavelength channel there is trade-off between node throughput and fairness among them. In order to abbreviate the transmission unfairness and to increase the throughput, we propose p-persistent medium access control (MAC) protocol. Each node uses the carrier sense multiple access with collision avoidance (CSMA/CA) protocol to transmit packets, and decides whether to use a local empty slot with probability p when a transferred packet based on source-stripping is dropped and emptied. Numerical prediction for the proposed MAC protocol is introduced to compute the maximum node throughput under uniform traffic condition. For more detail results, we use network simulation with self-similar traffic and introduce various results. The proposed MAC protocol gives better node throughput than non-persistent protocol and shows an improved fairness factor than 1-persistent protocol. Through simulation, we also find the reasonable probability of p-persistent protocol for a given architecture.     

Quality-of-service oriented medium access control for wireless ATMnetworks

The medium access control (MAC) protocol and the underlying traffic scheduling algorithm developed within project Magic WAND (Wireless ATM Network Demonstrator) are presented. Magic WAND is investigating wireless ATM technology for customer premises networks in the framework of the Advanced Communications Technologies and Services (ACTS) program funded by the European Union. The MAC protocol, known as MASCARA, is a hub-based, adaptive TDMA scheme which combines reservation- and contention-based access methods to provide multiple access efficiency and quality-of-service guarantees to wireless ATM terminal connections sharing a common radio channel. The traffic scheduling algorithm is delay-oriented to meet the requirements of the various traffic classes defined by the ATM architecture. The results of the simulation of a number of scenarios are presented to assess the performance of the proposed algorithm     

A novel medium access control protocol for passive optical network supporting local area networking capabilities

An alternate solution for Ethernet passive optical networks (EPON) providing local area networking (LAN) capabilities is proposed in this article. Our solution adopts a star coupler-based PON architecture and uses radio frequency subcarrier multiplexed transmission for the LAN traffic delivery. The proposed medium access control (MAC) protocol supports a fully distributed control plane among the optical network units (ONUs) for ONU–ONU communication as well as upstream access to the OLT. The simulation results indicate that the proposed MAC protocol outperforms the others in terms of the average packet end-to-end delay, especially for LAN traffic.     

A management and visualization framework for reconfigurable WDM optical networks

As the phenomenal advance in optical WDM networking technologies continues, optical WDM network equipment has been deployed not only in backbone networks, but also in regional, metropolitan, and access networks. It is widely believed that a major component of the next-generation Internet will be an IP-based optical network employing WDM. WDM wavelength routing and signaling have become an active research field, and dynamic and adaptive wavelength routing and assignment algorithms have been proposed. However, there is less work on reporting network control and management system implementation efforts over testbed WDM networks. This article presents a network management and visualization framework aimed at guiding the development of management applications for reconfigurable WDM optical networks. A layered framework architecture including element and network management and visualization is provided, and an object-based information model representing the WDM network is introduced. Functional components on reconfiguration, software agent, and network visualization services are presented, and important issues related to optical lightpath generation are discussed. A network visualization service also provides WDM control and management APIs to applications and access networks such as an IP network management system. To illustrate the usage of the framework, we share our experience in implementing the MONET network control and management system, and present network visualization views obtained from the MONET WDM network to highlight the framework features.     

WDM城域环网中支持可变长分组的节点结构及MAC协议设计

WDM城域环网在升级时,信道数可能是不变的.本文基于此设计了一种新颖的节点结构,它由固定发射器和一组固定接收器组成.基于该结构,文中给出了支持可变长分组的时隙结构及MAC协议.由于实现MAC协议毋需专用波长信道,提高了资源利用率.理论分析和仿真结果证明了本文设计方法可以充分利用空间重用能力,获得很好的网络流量,分组排队时延及分组丢弃率.对于信道数较多,或者网络在升级时信道数也可能变化的情况,本文建议采用固定发射器,一组"准"调谐的接收器结构.该方案可在实现复杂度,网络性能及成本间取得折衷.