福州广电网络的教育城域网实现方案

广电网络除了可开展多种业务,还可以根据用户的具体需求,很灵活地选择各种业务,将多个业务组合提供给不同的最终用户。主要介绍福州广电教育城域网实现方案,包括方案的总体设计框架、网络拓扑结构、设备选型等。实践证明技术先进的广电城域网可为教育系统提供广阔的应用平台。     

云计算计费模型研究

分析并提出了一种基于用户业务相关的灵活定价策略和用户资源使用行为及对资源评价反馈的计费模型:首先,基于设定的业务类别资源定价策略关联模块,获取针对特定业务类别的资源单价策略,同时通过对云计算系统中用户的资源使用行为的分析,获得用户的资源使用行为影响因子;并依据SLA(服务等级协议)对资源提供者进行评价得到服务满意度,基于用户行为影响因子和服务满意度对计费结果进行调整。模型的实际应用表明,其具有良好的应用效果。     

构建可扩展、可适配的业务配置激活方案研究

电信行业进入了一个飞速发展的全业务运营时期,电信运营商对现有网管运营支撑系统的要求不断提高.作为支撑系统重要环节之一的电信业务开通系统,原有的单一开通操作方式已经无法满足全业务快速发展的要求.为了快速支持新业务开通流程的定制和实施,灵活地支持全业务产品的组合开通,需要在综合资源、业务开通系统建设的基础上构建业务激活平台.本文通过研究和生产实践,结合不同业务开通激活场景,阐述了如何适应全业务运营灵活多变的特点,构建可扩展、可适配的业务配置激活方案.     

移动通信网融合HSS用户数据导出研究与应用

移动通信网HSS具备2G/3G、EPC及IMS三融合网络功能,但系统本身缺乏基于用户业务特征的数据导出功能.本文结合业务数据特征,充分发挥系统潜能,通过在设备上部署DTL用户导出功能,实现了HSS用户数据的精准导出和灵活管理,保障了设备侧与BOSS业务签约的一致性,提升了用户感知.     

40Gbps×16DWDM传输系统的色散补偿仿真研究

本文提出了一种速率为40Gbps的16通道DWDM传输系统的色散补偿方案,通过数值仿真研究了系统中光纤的入纤功率、色散补偿因子、色散补偿系数以及脉冲占空比等参数对系统传输性能的影响,仿真结果对40Gbps DWDM系统设计具有参考价值。     

FTTH家庭网关及其对视频业务的承载

基于EPON接入结构,提出了一种FTTH家庭网关的总体设计方案,该方案在用户端能够为用户提供视频、语音和数据三种业务的接口,实现三种业务的融合.尤其是在视频业务的承载方面,综合IPTV与DVB的优点,通过灵活组合,为用户提供H.264和MPEG-2两种编码方式的视频节目的接收平台.分析比较了两种编码方式的点播节目对带宽需求的差别.     

5G毫米波业务需求和灵活帧结构方案分析

毫米波系统是5G移动通信系统的重要组成部分,是5G满足大带宽需求的重要手段.对具体业务进行分析,明确毫米波适用场景和业务需求,提出适应不同业务需求的毫米波帧结构和灵活帧结构方案,并对方案进行可行性分析.     

一种适应复杂网络环境的数字远程监控系统

从行业实际需求和当前网络与视频技术发展现状出发,提出了一种数字远程监控系统方案,该方案能够灵活地部署于各种IP网络环境,充分利用网络资源,又能保证上层业务的部署不受网络环境的限制.     

WCDMA的业务复用方案原理及解复用的硬件实现

W-CDMA中的业务复用方案考虑如何以灵活、有效的方式将不同速率和质量要求(Qos)的业务进行复用.本文以3GPP指定的W-CDMA Release'99规范中的业务复用方案为基础分析了第三代移动通信系统中上/下行链路业务复用方案的原理和特点并给出上行业务解复用的硬件实现方案.     

CDMA系统提供的电信业务

蜂窝移动通信发展的总趋势是系统容量越来越大,技术越来越先进,组网方式、入网方式及业务的提供越来越灵活。CDMA是近年来用于数字蜂窝移动通信的一种先进的无线扩频通信技术。从业务角度来看,CDMA系统从服务的角度出发,为用户提供了更加丰富、多样且应用灵活方便的业务。本文将对这些业务作一介绍。按照CDMA的规范,交换子系统应能向用户提供用户终端业务、承载业务、补充业务三类业务。用户终端业务用户终端业务是在用户终端协议互通基础上提供终端间信息传递能力的业务,该类业务包括电话业务、紧急呼叫业务、短消息业务和语音…     

一种通用的OFDM发射机设计

正交频分复用（OFDM）系统参数众多,设计灵活,可以根据不同用途、信道环境以及接收机的性能等,设计出很多不同的OFDM系统。针对此问题,提出了一种通用的基于训练序列的OFDM发射机设计方案。从性能的角度出发,设计了OFDM符号结构和传输帧结构,并重点分析了OFDM数字基带调制模块的组成,最终在Xilinx开发板上实现了该方案,并获得了OFDM各模块的仿真时序图、OFDM射频信号频谱和误比特率图。研究结果表明,该方案频谱利用率高,复杂度低,通用性好。     

All-optical OFDM network coding scheme for all-optical virtual private communication in PON

A novel optical orthogonal frequency division multiplexing (OFDM) network coding scheme is proposed over passive optical network (PON) system. The proposed scheme for all-optical virtual private network (VPN) does not only improve transmission efficiency, but also realize full-duplex communication mode in a single fiber. Compared with the traditional all-optical VPN architectures, the all-optical OFDM network coding scheme can support higher speed, more flexible bandwidth allocation, and higher spectrum efficiency. In order to reduce the difficulty of alignment for encoding operation between inter-communication traffic, the width of OFDM subcarrier pulse is stretched in our proposed scheme. The feasibility of all-optical OFDM network coding scheme for VPN is verified, and the relevant simulation results show that the full-duplex inter-communication traffic stream can be transmitted successfully. Furthermore, the tolerance of misalignment existing in inter-ONUs traffic is investigated and analyzed for all-optical encoding operation, and the difficulty of pulse alignment is proved to be lower.     

Transforming the Statistical Distribution of Wireless OFDM Signal for PAPR Reduction

To reduce the high peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signal, a novel nonlinear companding transform (CT) scheme is proposed in this paper. This scheme can reallocate both the amplitude/power as well as statistical distribution of the companded signal more reasonably and flexibly than existing CT methods with low computational complexity. By choosing an appropriate companding parameter, it can provide more effective PAPR reduction but at the price of a minimal amount of bit-error-rate (BER) performance degradation caused by the companding distortion. The closed-form expressions including the achievable PAPR gain, signal attenuation factor, and corresponding selection criteria for the companding parameter were derived. Computer simulations demonstrate that the scheme significantly improves the overall performances of OFDM system in terms of PAPR, BER and bandwidth efficiency under the multipath fading channel or with the high power amplifier.

     

Load-adaptive frequency reuse scheme for inter-cell interference coordination in relay networks

Cellular relay networks adopting orthogonal frequency division multiple(OFDM)technology has been widely accepted for next generation wireless communication due to its advantage in enlarging coverage scale as well as improving data rate.In order to improve the performance of user equipments(UEs)near the cell edge,especially to avoid the interference from inter-cell and intra cell,an enhanced soft frequency reuse scheme is adopted in this paper to assure inter-cell interference coordination(ICIC).Compared with traditional frequency allocation work,the proposed scheme is interference-aware and load-adaptive,which dynamically assigns available frequency among UES under certain schedule method in variable traffic load condition and mitigates interference using information provided by interference indicator.It can improve signal-to-interference plus noise ratio(SINR)of the UE in each sub channel thus enable the system achieve better throughput and blocking probability performance.Simulation results prove that the proposed scheme may achieve desirable performance on throughput,blocking probability and spectral utilization in the sector under different traffic load compared with other schemes.     

放大转发OFDM协同中继系统多业务资源分配机制

提出了点到点多载波协同中继系统多业务资源分配框架,并给出了一种最优化自适应功率、载波和比特分配算法;为了降低算法复杂度,又提出了一种次优搜索算法,该算法依据信道特性,在满足业务QoS基础上使业务占用资源最小.仿真结果表明:提出的最优算法在保障多媒体业务QoS的基础上能够有效改善频谱效率,对比于传统算法有1～2bit/(s·Hz)的性能提升;而提出的次优搜索能够取得接近最优算法的性能(差别在0.6 bit/(s·Hz)左右),并且实现复杂度由指数级别降至线性.     

An OFDM-TDMA/SA MAC Protocol with QoS Constraints for Broadband Wireless LANs

Orthogonal frequency division multiplexing (OFDM) is an important technique to support high speed transmission of broadband traffic in wireless networks, especially broadband wireless local area networks (LANs). Based on OFDM, a new multiple access scheme, called OFDM-TDMA with subcarrier allocation (OFDM-TDMA/SA), is proposed in this paper. It provides more flexibility in resource allocation than other multiple access schemes such as OFDM-TDMA, OFDM-frequency division multiple access (OFDM-FDMA), and orthogonal frequency division multiple access (OFDMA). With OFDM-TDMA/SA, a medium access control (MAC) is designed for broadband wireless LANs. It optimizes bit allocation in subcarriers so that maximum bits are transmitted in each OFDM symbol under a frequency selective fading environment. The OFDM-TDMA/SA MAC protocol also supports three classes of traffic such as guaranteed, controlled-load, and best effort services. Based on the optimum subcarrier bit-allocation algorithm and considering heterogeneous QoS constraints of multimedia traffic, a hierarchical scheduling scheme is proposed to determine the subcarriers and time slots in which a mobile terminal can transmit packets. In such a way, the OFDM-TDMA/SA MAC protocol significantly increases system throughput in a frequency selective fading environment and guarantees QoS of multimedia traffic. Computer simulation is carried out to evaluate the performance of the OFDM-TDMA/SA MAC protocol. Results show that the new MAC protocol outperforms other MAC protocols for OFDM-based wireless LANs. This work was supported by the State of Georgia Yamacraw Project (E21-105).     

Channel assignment with QoS guarantees for a multiclass multicode CDMA system

In a wireless system that supports multimedia services, each traffic requires different quality of service (QoS) at both communication on radio links and connection admission. We initially derive the uplink capacity satisfying the QoS constraint on radio links in a multiclass multicode code-division multiple-access (CDMA) system. Based on the derived capacity, the number of channel elements, which is one of the system resources, is determined. Then, we define the QoS parameters associated with connection processes. To guarantee the defined QoS at the connection level, under given channel elements, we propose a channel-assignment scheme with dynamic priority adjustment (DPA). The proposed scheme gives multipriority to different traffic classes. Real-time classes can preempt non-real-time classes with restricted preemptive priority. Such restriction is regulated by preemption-free code channels and a buffer threshold for non-real-time classes. Among real-time classes, different priorities are assigned to each traffic class by code reservation parameters. These multipriority parameters are dynamically adjusted in order to guarantee different QoS requirements. We analyze the DPA scheme by the matrix-geometric method, and evaluate the performance of each traffic class. The results show that the proposed scheme flexibly guarantees QoS depending on traffic loading condition and achieves high channel utilization.     

An optimized scheduling scheme in OFDMA WiMax networks

This paper proposes an optimized scheduling scheme in OFDMA‐based WiMax networks to achieve both optimized system throughput and a complete QoS implementation for various types of traffic flows. Our scheduling scheme includes two components, one is the resource allocation for each user; the other is the QoS scheduling for various traffic sessions. Specifically an optimization problem is formulated to distribute all OFDMA channel resource among different competing users by exploiting the transmission adaption and multiuser diversity on each traffic channel. The optimized resource allocation can also be processed under different constraints to achieve different performance metrics. To ensure the WiMax QoS performance, we perform the resource allocation in a priority manner with respect to the different types of QoS requirements and get a desired transmission bandwidth for each user. Based on it we further schedule different traffic sessions at each user with respect to a proper admission control mechanism. The relevant solution and algorithms for our proposed scheduling scheme are presented in detail. Both the theoretical analysis and simulation results show that our scheme can achieve the key performance objectives such as complete QoS requirements, high channel transmission efficiency and optimal throughput over the whole OFDMA WiMax system. Copyright © 2009 John Wiley & Sons, Ltd.     

MIMO-OFDM自适应比特分配算法研究

针对当前OFDM系统中的比特分配算法复杂度比较高,不适合运用于自适应调制系统中,提出改进的自适应比特分配调整算法,采用变步长调整的思想,进一步简化比特分配的复杂度。在此基础上,将OFDM和MIMO技术结合,进行MIMO-OFDM系统的相关参数仿真并进行分析。通过仿真说明本文介绍的算法计算复杂度小,成本较低,适用多用户,能够很好的应用到实际中。     

Video coding for OFDM systems with imperfect CSI: A hybrid digital–analog approach

Performance of an orthogonal frequency division multiplexing (OFDM) system is greatest when the exact channel state information (CSI) is used for transmitter rate control and power allocation. However, in real systems CSI can only be approximately known. Moreover, in video communication, it can be difficult to use any CSI for rate control of a video codec if the channel changes significantly during a group of pictures coded jointly, such as when the receiver is moving. We address this issue through a hybrid digital–analog (HDA) coding system where a standard video codec is used to generate a fixed-rate base layer upon which the analog quantization error is superimposed as a refinement layer. The system adapts to channel variations by proper transmit-power allocation between digital and analog components and across OFDM subcarriers, based on CSI. We present a power allocation scheme for this system which explicitly takes into account the imprecise nature of the available CSI. Experimental results obtained with simulated OFDM channel traces show that proposed scheme is able to achieve a much better quality-vs-reliability trade-off in video transmission, compared to the best known digital-only and analog-only alternatives.