一种面向超高速以太网的双模RS解码器设计

100 GB以上超高速以太网采用FEC(Forward Error Correction)技术来降低误码率，提升传输可靠性。针对目前以太网中RS(528,514)码和RS(544,514)码两种编解码规范并存，导致的FEC解码器结构冗杂、资源耗费严重、面积占用大等问题，文中将多模RS解码器的概念引入以太网FEC解码器设计，提出一种适用于100 GB及以上超高速以太网的双模RS解码器。通过对不同的编解码规范进行研究与分析，设计通用的SC、KES、CSEE模块并实现部分内存共享，采用并行设计与流水线处理来降低传输时延、提高吞吐量。在100 GB以太网中进行仿真实验，测试该双模解码器的功能完整性、资源开销以及功耗。结果表明，所设计的双模RS解码器能成功实现对两种FEC规范的解码，解码时延分别为93 ns,96 ns，相比于传统RS解码器，资源开销与功耗分别降低32.32%,17.34%。     

地面数字电视广播传输标准中FEC码的分析

概述了地面数字电视广播传输标准中FEC码的基本原理和实现方法,介绍了LDPC码的解码算法和仿真结果,并对符合地面数字电视传输标准的3种不同码率的FEC编码进行分析,给出了仿真结果.     

机会网络中一种低缓存占用的Epidemic 路由算法

由于机会网络中节点的缓存空间有限,容易导致数据分组丢失和时延增加。针对部分数据分组已经到达目的节点,但是该类分组仍在网络中其它节点存储、传输问题,提出一种低缓存占用的Epidemic路由算法(RBER)。该算法通过SV运算进行节点缓存清理,从而避免这类冗余数据分组对缓存的占用。理论分析和仿真结果表明,该机制能够降低网络开销、数据分组的发送和缓存占用。     

OTN中FEC的优化设计及实现

光信号在OTN中传输时不可避免地会产生误码,而传统的反馈重传纠错方式因为需要反馈信道和重传等待时间,所以不适合在传输速率较高的OTN中使用。因此利用RS码及数据交织方法,设计了OTN中的FEC电路,同时为了提高电路性能,对电路中常用的有限域乘法器进行了优化。并通过仿真和FPGA验证电路功能的正确性。实验结果表明,所设计的FEC电路能够纠正传输中出现的误码,满足OTN技术要求。     

光标签交换网络中边缘汇聚节点的研究

构建了一种光标签交换网络中可行的具有业务汇聚、分组重组、突发帧封装等功能的边缘节点结构,提出了一种适合于在突发环境下传输的帧格式.在此基础上搭建了光标签交换演示平台,该平台承载的光载荷速率为2.5Gbps,支持4路千兆以太网业务的接入,并成功进行了流媒体传输实验.     

光交换中标签提取技术的研究

随着光交换技术的快速发展,在核心节点如何有效快速地提取标签一直是研究的热点.分别对SCM技术分离标签、FP-SOA技术分离标签和利用特定光码控制光开关分离标签进行了研究,分析了各种方法的优缺点,介绍了光极性法分离标签与净荷的原理,提出了利用光不同模式分别调制标签与净荷的结构模型.     

基于多重光正交码光标签的光分组交换系统实验研究

采用多个光正交码串行排列组成的多重光正交码(MOOC)标签格式,提高了可用标签的数目;构建了基于MOOC标签的光分组交换系统(OPS),对该系统中的各项关键技术,包括光分组信号产生单元、光标签处理单元、交换控制单元,光交换矩阵等进行了分析和研究;完成了光分组交换系统演示实验,并对实验结果进行了讨论.     

ASON中信令协议RSVP_TE建立LSP的研究

文章对自动交换光网络（ASON）信令协议——基于流量工程扩展的资源预留协议（RSVP_TE）的主要内容及工作机制进行了分析研究,它主要是在ASON网络中动态地完成建立、保持和删除标签交换路径（LSP）。LSP的建立时间与信息传输时延、信息处理时延和节点配置时间有关。在RSVP_TE信令基础上提出一种新的标签分组方式来减少LSP建立时延。从理论和仿真上都验证了采用这种标签分组方式会改善LSP建立时延性能。     

一种新型的光分组交换环网体系结构

提出了一种以波长为标签的新型全光变长分组交换环网的体系结构、网络节点的光分组数据包收发模型,以及防止光分组冲突的多令牌协议。使用多令牌协议的环网在进行光分组交换时,不需要高速的光子器件,无需使用延迟线、电中继以及解决光分组的冲突问题。通过数值仿真,分析了4节点、8节点和16节点环网巾光分组各种的时延特性以及网络的吞吐量特性。结果表明,当网络负载增大时,数据包的平均时延增大,同时网络节点的吞吐量和资源利用率也随之增大;网络节点数目越多,网络的吞吐率也越大。     

基于光标签的光分组交换系统研究

光码分复用(OCDM)系统在光域对各路信号进行光编/解码,对用户数据进行全光信号处理,但是用户数目受到光标签数量的限制.光分组交换技术具有高速率、对数据速率和格式透明等优点,更能适应快速变化的网络环境,但存在光标签的提取、更新和竞争的难题.介绍了一种新型的基于WDM(波分复用)和OCDM的光分组交换系统,结合了光码分多址(OCDMA)技术和光分组交换(OPS)技术的优点,既扩展了系统用户容量又避免了对标签进行电域的处理,实现了数据的全光交换.     

Ultrafast all-optical pattern matching using differential spin excitation and its application to bypass/drop self-routing for asynchronous optical packets

This paper presents a novel scheme for ultrafast all-optical pattern matching using the differential spin excitation in semiconductor multiple quantum wells (MQWs). In a demonstration of an all-optical pattern matching between two 100-Gb/s 16-bit optical packets, the contrast ratio of the photodiode (PD) output from the pattern matcher, between the pattern matched and the pattern-unmatched cases, was more than four for packets with a 2-dB power fluctuation. As an application of the pattern matcher to optical-packet-switched ring networks, bypass/drop self-routing is demonstrated for asynchronous 100-Gb/s 32-bit optical packets with 8-bit labels. In the experiment, a label of an incoming packet was compared to a local address (LA) given to a node in the optical domain. By changing the pattern of the LA packet instead of that of the incoming packet, the pattern matching was carried out for packets with various kinds of patterns. The contrast ratio of the PD output was more than six for all patterns.     

A novel all-optical label swapping based on RZ-DQPSK/IRZ-ASK combined modulation format

A novel all-optical label swapping based on optical return zero (RZ) differential quadrature phase shifted keying/inverse return zero amplitude shifted keying (RZ-DQPSK/IRZ-ASK) combined modulation format scheme is investigated and analyzed theoretically. Internet protocol (IP) packets can be efficiently labeled and processed using this proposed scheme. Numerical simulation is taken to demonstrate the transmission characteristic of the all-optical label swapping based on RZ-DQPSK/IRZ-ASK modulation format. The transmission performance can be affected by the duty cycle of the IRZ pulse, the IRZ-ASK label extinction ratio, the dispersion compensation ratio, received optical power and the coupling coefficient of the coupler. Results show that the IRZ-ASK label extinction ratio is almost infinite and preferable performance is obtained. The proposed scheme is a practical solution to meet the data rate and cost-efficient of the optical links simultaneously in tomorrow's all-optical label swapping.     

Design and experimental demonstration of a variable-length optical packet routing system with unified contention resolution

This paper presents theoretical design, network simulation, implementation, and experimental studies of optical packet routing systems supporting variable-length packets. The optical packet switching network exploits unified contention resolution in core routers in three optical domains (wavelength, time, and space) and in edge routers by traffic shaping. The optical router controller and lookup table, implemented in a field-programmable gate array (FPGA), effectively incorporates the contention resolution scheme with pipelined arbitration of asynchronously arriving variable-length packets. In addition, real-time performance monitoring based on the strong correlation between the bit-error rates of the optical label and those of the data payload indicates its application in optical time-to-live detection for loop mitigations. Successful systems integration resulted in experimental demonstration of the all-optical packet switching system with contention resolution for variable-size packets.     

Mini‐Slot‐Based Transmission Scheme for Local Customer Internetworking in PONs

We propose a new mini‐slot transmission scheme for a passive optical network (PON) in which each customer can be switched either to access mode or to internetworking mode dynamically. In this paper, we present the system implementation (called LAN‐PON) as well as the performance of the proposed transmission scheme to illustrate its feasibility and benefits. A mini‐slot scheme can rapidly reduce the queuing delay, which increases due to the flooding of the deflected packets in a deflection scheme. We evaluate the impact of mode switching time on the bandwidth gain (throughput) and delay of local area network (LAN) traffic in the LAN‐PON with a mini‐slot scheme. We also analyze a theoretical delay model of the proposed scheme. The simulation results demonstrate that switching time has an impact on LAN performance, and the average packet delay of the proposed scheme is significantly improved compared to that of the deflection scheme.     

The RRA‐ISA multiple access protocol with and without simple priority schemes for real‐time and data traffic in wireless cellular systems

A multiple access protocol, based on a Reservation Random Access (RRA) scheme, is derived for a wireless cellular network carrying real-time and data traffic. Given a TDMA framed channel and a cellular structure, the aim of the protocol is that of maximizing the one-step throughput over an entire frame. This is achieved by deciding on the access rights at the cell base station, which then broadcasts this information at the beginning of the frame. The decision is made on the basis of binary channel feedback information (collision/no collision) over the previous frames, as well as of long term averages of packet generation rates at the mobile stations, assuming independence in the presence of packets at the latter. The resulting protocol has therefore been termed Independent Stations Algorithm (ISA), and the overall scheme RRA-ISA. As in other RRA protocols, time constrained (e.g., voice) traffic operates in a dynamic reservation mode, by contending for a slot in the frame with the first packet of a burst, and then keeping the eventually accessed slot for the duration of the burst; packets of the time constrained traffic unable to access a slot within a maximum delay are dropped from the input buffer. No such constraint is imposed on data traffic. Together with the “basic” version of the access algorithm, three other variants are presented, which exploit three simple different priority schemes in the RRA-ISA “basic” structure, in order to give a prominence to the voice service. The aim of these variants is to improve the performance in terms of the maximum number of stations acceptable in the system, by slightly increasing the data packets delay. All the proposed schemes are analyzed by simulation in the presence of voice and data traffic. Several comparisons show a relevant performance improvement (in terms of data delay and maximum number of voice stations acceptable within a cell) over other protocols that use ALOHA as a reservation mechanism (RRA-ALOHA or PRMA schemes). This revised version was published online in June 2006 with corrections to the Cover Date.     

Reduced-rate retransmissions for spread-spectrum packet radio multimedia networks

A reduced-rate retransmission (RRR) scheme is proposed for improving the throughput performance of spread-spectrum packet radio networks. The scheme takes advantages of the available multi-rate scalable source coding techniques. It assumes that several versions of a data packet with different sizes (number of information bits) are available. The transmission of a packet starts from its full-size version. If the full-size version is not correctly received, its half-size version is used in the retransmission. If further retransmissions are needed, the quarter-size version and so on are used. The shrunk packets are transmitted either in a minislot if the processing gain is kept the same, or occupying a slot duration by increasing the processing gain proportionally. In both cases, the effective signal to interference ratio for a packet is increased. As a result, the system throughput is improved. Theoretical and numerical results are provided in this paper which illustrate the throughput improvement. Another advantage of the proposed RRR scheme is that the packet-size reduction provides finer granules for link adaptation. Therefore, it is especially suitable for multimedia applications for which codes of variable rate for the source data are available and which can tolerate gracefully degraded quality of service. The performance of the proposed scheme in fading channels is also addressed.     

Code-based all optical routing using two-level coding

Code-based all optical routing employing a two-level-coding scheme is proposed. The first level of coding is employed to establish connections between users within a local area network; a second level of coding provides routing/interconnectivity between networks. The limitations due to physical-layer impairments, such as relative intensity noise (RIN) of the optical source, the signal-dependent shot noise, optical beat interference (OBI), and thermal noise at the receiver, which are some of the fundamental issues in the design of practical optical code division multiple access (CDMA) systems, are analyzed for the two-level scheme. The throughput in terms of "packets/time slot" offered by the scheme is also compared with that of the wavelength division multiple access (WDMA) system. The system capacity in WDMA is limited by the number of available wavelengths; optical CDMA, on the other hand, has many codes (user addresses), but the throughput is limited by multiple user interference, OBI, and RIN. System designs that overcome these effects and thereby improve the throughput are suggested.     

Elliptical slot loaded partially segmented circular monopole antenna for super wideband application

This article inspects partially segmented circular monopole with elliptical slot for super wideband applications. Two significant characteristics of proposed antenna design are: (i) partially segmented circular monopole, notch loaded elliptical ground plane along with tapered microstrip line provides super wide bandwidth; (ii) elliptical slot in between the partially segmented circular monopole reduces the lower operating frequency (1.07 GHz–0.96 GHz), which in turn enhance the bandwidth dimension ratio (BDR). For verifying the simulated outcomes, antenna prototype is practically constructed and measured. The proposed antenna design attains frequency range from 0.96 GHz to 10.9 GHz (VSWR < 2) with bandwidth ratio of 11.35:1 and percentage bandwidth of 167.22%. Bandwidth dimension ratio of proposed radiator is 6975.22. Frequency as well as time domain analysis of proposed radiator approves its applicability for super wideband wireless applications.     

Performance evaluation of a satellite-switched variable-frame TDMA system

In satellite-switched time-division multiple access (SS/TDMA) systems, the demand assignment control is a suitable scheme for the bursty packets to enhance the capacity efficiency. In the system, by applying the demand assignment scheme, the minimum transmission time could be achieved by the efficient time slot assignment algorithm. According to a given traffic matrix, the minimum transmission time cannot exceed the fixed TDMA frame duration. The spare time may be left at the end of the TDMA frame as the growth space for the future needs. To increase the system efficiency, the spare time could be reduced. In this paper, a demand assignment protocol with a variable frame is proposed for the system. The Markov chain model is applied to analyze the system performance on throughput, balking probability and packet delay. Performance comparison with the previous presented protocol, the proposed protocol could show a simple control technique and the efficient performance results in the system. It is a suitable candidate to be employed in the satellite networks to provide communication between the satellite and earth stations.     

A 40-Gb/s Self-Clocked Bidirectional Serial/Parallel Converter for Asynchronous Label Swapping

A novel scheme for self-clocked bidirectional serial/parallel conversion is proposed with an optically clocked transistor array (OCTA). As a result of its internal clock generation, serial-to-parallel (SP) and parallel-to-serial (PS) conversion capability, the OCTA alone realizes a single-chip low-power interface between input-output high-speed asynchronous burst optical packets and complimentary metal-oxide-semiconductor electronics, thus enabling a compact low-power solution for label swapping of optical packets. An eight-channel OCTA demonstrates self-clocked SP and PS conversion at 40 Gb/s