Simultaneous Burst and Burst Control Packet Transmission Protocol for Optical Burst Switching Ring Networks

In this letter, we design a collision resolution protocol for optical burst switching ring networks to avoid burst collision. We define the offset time condition for no burst transmission collision and manage the free time list of nodes for no burst reception collision. In order to improve the throughput, we use a fiber delay line, void‐filling, and void‐compression. This protocol does not require any additional procedures for bandwidth reservation such as centralized assignment of bandwidth, lightpath setup of WDM ring networks, or token capturing for the burst transmission. The simulation results show that the proposed protocol can achieve high throughput while saving 70% of wavelengths when compared to round robin with random selection, round robin with persistent, and round robin with non‐persistent with only destination delay.     

A New Performance Measurement for Voice Transmission in Burst and Packet Switching

Voice transmission in burst switching is characterized by the process of talkspurt clipping, while in packet switching, it is characterized by the process of packet delay. In most analyses, the talkspurt clipping has been measured by the clipping probability averaged over all bits, and the packet delay has been measured by the delay performance averaged over all packets. The resulting measures overlook the duration of clipping in a talkspurt and the significant difference of delay in packets arriving at different times. Because of the nature of voice, different effects of these may result in substantially different degrees of voice distortion. This paper studies the worst case performance of both processes. The voice traffic is modeled as a process alternating between overload and underload periods. Statistically, more clipping and delay will be incurred while in the overload period. By worst case we mean that, in burst switching, we measure the worst case of talkspurt clipping duration in an overload period, while in packet switching, we measure the worst case of packet delay in an overload period. Furthermore, a simple closed form equation is derived which gives a very good approximation of the worst case mean packet delay performance. This equation can be more generally applied when the packet service time is to be geometrically distributed or when voice and data are to be integrated. The voice performances in burst switching and packet switching are also compared.     

CDMA2000 1xEV-DO中的分组调度算法

移动通信系统需要更好地支持分组数据业务，并满足高速分组数据业务的服务质置要求。这可以通过采用好的调度算法提高平均业务速率和系统整体稳定性实现。针对CDMA2000 1x EV-DO系统的有代表性的调度算法有3种：正比公平算法、速率受限的最大载干比算法、加权公平排队-正比公平（WFQ-PF）联合算法。正比公平调度算法是一种算法简单实用的调度方案，但不能满足用户的服务质景保证；速率受限的最大载干比算法具有比正比公平算法更高的平均吞吐量，可方便地在吞吐量和公平性之间获得很好的折衷；WFQ-PF联合算法具有良好的综合性能，但算法较复杂。     

Decorrelating Detectors for a Dual Rate Synchronous DS/CDMA System

This paper addresses the use of decorrelating detectors for a dual rate DS/CDMA system that serves both low bit rate and high bit rate users. We assume that in an interval of duration T ₀, a low rate user transmits one bit while a high rate user transmits M bits. Applying a standard decorrelator to the interval of duration T ₀ yields an M bit processing delay for high rate users and a computational complexity that grows with M. In this paper, we propose a decorrelator that generates bit decisions for each high rate user in every subinterval of duration T_0/M. To decode a low rate user, a soft decoding rule applies maximal ratio combining on M separate decorrelated outputs of each low rate user. The soft decoding dual rate decorrelator eliminates the bit processing delay for high rate users and also reduces the computational complexity of a standard decorrelator. Further, it is shown that the asymptotic efficiency of the standard decorrelator is greater than or equal to the proposed decorrelator. By evaluation, it is observed that when the signature sequences have good correlation properties, the proposed soft decoding decorrelator is found to perform nearly as well as the standard decorrelator. However, when the signature sequences have high cross-correlation, then the proposed decorrelator suffers in terms of bit error rate while retaining the near-far resistance property.     

一种基于速率控制的反向链路分组数据新传输方案

该文介绍了在CDMA2000 中反向链路数据传输采取的速率控制机制;然后提出了一种在CDMA2000 1x Release C系统中实现该机制的方案。通过分析和系统仿真可知,该方案有利于提高反向链路的数据吞吐量,又能保持RoT(Rise-over-Thermal)的稳定,而且所需的时延相对于调度方式要小,能较好地适应对时延敏感业务的要求。     

应用网络编码的分组交换调度算法

网络编码理论与交换调度算法相结合重点是实现在联合输入输出排队（CIOQ）交换结构中提供组播服务。文章证明了对一个流中的分组进行线性网络编码可以承载不允许网络编码时不能够承载的交换流量模式,也就是说,网络编码允许CIOQ交换结构在实现组播服务时有更大的速率区域,并给出了基于图论方法的描述。运用增强冲突图的稳定集多面体等概念,文章证明了计算离线调度的问题可以简化成某种图染色问题,同时,也针对组播调度提出了一个称之为最大权重稳定集的在线调度算法。     

Adaptive Retransmission Diversity with Packet Combining for Slotted DS/CDMA Packet Radio Networks

A time diversity automatic repeat-request (ARQ) scheme is investigated for slotted random access direct-sequence code-division multiaccess (DS/CDMA ALOHA) wireless packet radio networks on multipath Rayleigh fading channels. The receiver retains and processes all the retransmissions of a single data block (packet) using predetection diversity combining, instead of discarding those which are detected in error. This effectively improves the system throughput and delay characteristics especially at small values of signal-to-noise ratio (SNR) per bit. A simple and practical selection combining rule is proposed, which lends itself to a low-complexity receiver structure and specifically suitable for high data rate transmissions. Owing to the stochastic nature of the multiple access interference, the new maximum output selection diversity (MO/SD) system yields superior performance in comparison to the traditional maximum SNR selection diversity (SNR/SD) model. The bit error rate performance, throughput and the average number of transmissions required to transmit a packet successfully with and without forward error correction (FEC) are evaluated. Numerical results reveal that the proposed adaptive retransmission diversity with packet combining provides a considerable advantage over the conventional slotted DS/CDMA ALOHA without incurring a substantial penalty in terms of cost or complexity.     

两级混合型DS/CDMA捕捉结构

提出一种基于匹配滤波器的混合型快速捕捉结构,将固定停顿时间与可变停顿时间相结合,实现可靠快速的捕捉.数值分析结果表明,与传统两级固定停顿时间结构相比,捕捉性能得到显著提高.     

混合ossiocs网络中基于突发插空的传输机制(英文)

Hybrid optical switching networks make full use of the advantages of Optical Circuit Switching(OCS)and Optical Burst Switching(OBS).In parallel hybrid optical switching networks,edge nodes choose a switching mode for traffic and no longer change.The inflexible decision making of the traffic transfer mode leads to low resource utilization when the arrival rate of the OCS traffic is lower than the capacity of the light path.In this paper,a new transmission scheme is proposed to improve resource utilization for hybrid optical switching networks.When the traffic arrival rate of the light path is lower than the transmission rate of the light path,the OCS traffic flow is reshaped at the edge nodes to generate a series of voids.Then,several message packets are sent along the light path to inform the core nodes of the voids of the light paths that represent the unused bandwidth resources.To improve the resource utilization,the voids can be filled with data bursts by core nodes.The simulation results show that the new scheme can effectively reduce the burst loss rate and improve the link utilization of the hybrid optical switching network on the premise of a providing service quality guarantee for OCS traffic.     

DS／CDMA系统中的干扰抑制

WCDMA技术是无线宽带通信发展方向之一，其抗干扰技术成为WCDMA系统中的关键技术。本文就DS/CDMA系统的抗干扰性及其干扰抑制进行分析和探讨。     

CDMA蜂窝移动通信系统中基于Eb/No的无线分组公平调度算法

在第三代移动通信的无线资源管理机制中,分组调度机制在保证预期的服务质量（QoS）和优化无线资源的利用率方面起到了至关重要的作用.至今已经有很多的调度算法被提出,用来有效地提高无线网络资源的利用率.本文提出一种基于Eb/No并且利用功率控制和管理机制的无线分组公平调度算法用来保证QoS,优化资源配置并且达到调度公平性.     

Framework for Analysis of Transmission Rate Scheduling for Wireless CDMA Data Networks

The optimal utilization of network resources and the capacity to fulfill quality of service requirements are key requirements for 3rd G networks operations. Several burst admission and transmission rate scheduling algorithms are proposed in the literature. In this study, we develop an analytical framework for the downlink transmission rate scheduling problem for CDMA networks employing discrete service bit rates. The framework uses the average downlink transmit power as the system state and develops a K-dimensional Markov chain representing all possible states in the system. In addition, the transition probabilities due to arrivals of burst requests are made a function of the power utilization and the average power required to support the new burst taking into account the path loss model. The study assumes a transmission rate assignment scheme where the maximum possible system bit rate is assigned given the current system state and the subscriber’s eligibility profile for particular system service rates. The analytical model provides performance metrics such as system throughput, average power utilization, average number of simultaneous transmissions, burst request blocking probability, and mean burst service time. While the developed model is applicable for a general CDMA based network with arbitrary discrete system service bit rates, the model is evaluated for the example of a cdma2000 1xRTT network. A comparison between simulation and analytic results to assess the accuracy of the model is provided.

A Distributed Packet Scheduling Scheme with Interference Avoidance for Non Real-Time Applications in CDMA Networks

In this paper, a packet scheduling scheme based on real-time channel conditions and dominant intercell interferer avoidance is proposed, studied and evaluated for reverse links in a time-slotted code division multiple access (CDMA) system. This scheme is implemented by distribution of tags by receivers among transmitters. Each base station issues M(1) tags to M mobile users based on the ranked reverse link gains in every slot. M=1 corresponds to spread-spectrum time division multiplexing mode operation and M1 corresponds to scheduling multiple simultaneous transmissions as in the traditional CDMA systems. The number of issued tags is a system parameter which depends on the expected traffic, the number of cells and the propagation conditions in the network. In the proposed scheme, users who not only have stronger channel gains to their respective home base stations but also cause relatively lower intercell interference are scheduled for transmissions. Different classes of tags can be issued and various scheduling decision rules can be implemented giving flexibility in interference management. Simulation results in shadow and multipath fading environment are presented to show the performance advantage of the proposed scheme.     

A Novel EKF-Based Recovery in DS Scheme for DS/CDMA Systems Tracking Code Delay

Classical delay-lock loops (DLL) have beenwidely considered for code synchronization purposes inDS/CDMA systems, although they have not been devised foroperation when channel fading is present. This paper describes a new code synchronizationscheme based on a previously proposed extended Kalmanfilter (EKF) approach. The scheme proposed in this paperis able to operate under low signal-to-interference ratios (SIR), usual at the receiver input incellular CDMA mobile environments, and it outperformsthe behavior of previously proposed EKF-based schemes,which failed in such environments. Performance results under realistic mobile environment conditionsare shown in terms of the mean time to lose lock (MTLL)and the tracking error variance ² for a wide range ofSIR values and under Rayleigh fading. Moreover, the Cramer-Rao lower boundon ² is also computed inorder to validate the results obtained viasimulations.     

Performance of a Multiuser Detector with Multicarrier Transmission for a DS/CDMA System

In this paper, a new multiuser detector combining decorrelating detector and multicarrier transmission scheme is proposed and analyzed in a frequency selective Rayleigh fading channel. The bit error probability and asymptotic multiuser efficiency are derived as performance measures. From numerical results, it is shown that the proposed detector achieves better BER performance and lower computational complexity compared to a conventional decorrelating detector. It is also shown that the proposed detector is robust to partial narrowband interference, and alleviates near-far problem effectively. The results in this paper can be applied to design of a wideband CDMA system.     

基于突发分组传输的OFDM同步算法研究

基于802.11a突发数据帧结构,分析了突发分组传输中OFDM同步算法的性能;对802.11a突发数据帧中的短训练符号结构作了改进,给出了相应的时频域估计算法;该算法有良好的定时相关特性,运算复杂度低,仿真结果表明该算法具有很好的定时和频偏估计性能.     

Priority‐Based Duplicate Burst Transmission Mechanism in Optical Burst Switching Networks

This paper proposes a priority‐based duplicate burst transmission mechanism in an optical burst switching network to enhance the probability of successful reception of bursts. The performance of the proposed mechanism is evaluated by NS2 simulations. Our results show that the burst loss rate is improved especially under light traffic loads.     

Multiple Antenna Enhancements for a High Rate CDMA Packet Data System

A High Data Rate (HDR) system has been proposed for providing downlink wireless packet service by using a channel-aware scheduling algorithm to transmit to users in a time-division multiplexed manner. In this paper, we propose using multiple antennas at the transmitter and/or at the receiver to improve performance of an HDR system. We consider the design tradeoffs between scheduling and multi-antenna transmission/detection strategies and investigate the average Shannon capacity throughput as a function of the number of antennas assuming ideal channel estimates and rate feedback. The highest capacities are achieved using multiple antennas at both the transmitter and receiver. For such systems, the best performance is achieved using a multi-input multi-output capacity-achieving transmission scheme such as BLAST (Bell Labs Layered Space-Time) in which the transmitted signal is coded in space and time, and the receive antennas are used to resolve the spatial interference. In the second part of the paper, we discuss practical transmitter and receiver architectures using BLAST for approaching the theoretical gains promised by the capacity analysis. Because the terminal receivers will be portable devices with limited computational and battery power, we perform a computational complexity analysis of the receiver and make high-level assessments on its feasibility. We conclude that the overall computational requirements are within the reach of current hardware technology.     

网络服务器系统与新型光突发交换网络解决方案

随着用户带宽超摩尔定律增长、传输链路容量的迅猛增加,节点服务器系统能力成为制约网络容量增长的主要瓶颈。网络业务的发展趋势不会坐等高性能光子器件的成熟和实用化,可以预见未来10—20年内光子器件瓶颈将制约着新型光网络节点能力提高。文蕈将网络分成接入、节点和链路3个网络服务器系统,提出一种全新的光网络体系架构——基于服务的光网络体系架构,通过一个隐函数从网络代价、能耗和容量等角度定性考察各服务器系统对网络性能的影响。由此提出了双光纤链路与IP插空联合的光突发交换解决方案,以缓解光子器件瓶颈的限制。     

Total Resource Requirements‐Based Priority Queuing Scheme for DS/CDMA Cellular Networks

We propose and analyze a priority queuing scheme that gives priority in the same class of calls according to their total resource requirements (TRRs). The proposed scheme gives a higher priority to the calls that have a lower TRR over the calls that have a higher TRR. The numerical results show that the proposed priority queuing scheme provides better performance than the traditional queuing schemes in call blocking probability.