基于GMPLS的动态分布式WDM网状网路由选择算法研究

研究了在基于GMPLS的WDM网络中,当节点不具备波长变换能力并且配备有限个光收发器对时,如何为到达的业务请求建立标记交换路径(LSP)的问题。提出一种以跳数和带宽碎片要求为权重,合理分配带宽资源的新算法。仿真结果表明,该算法在保证用户业务可靠性要求的同时,能够更有效地提高全网资源的利用率,并大大降低网络阻塞的可能性。     

基于GMPLS的动态分布式WDM网状网路由选择算法研究

研究了在基于GMPLS的WDM网络中，当节点不具备波长变换能力并且配备有限个光收发器对时，如何为到达的业务请求建立标记交换路径（LSP）的问题。提出一种以跳数和带宽碎片要求为权重，合理分配带宽资源的新算法。仿真结果表明，该算法在保证用户业务可靠性要求的同时，能够更有效地提高全网资源的利用率，并大大降低网络阻塞的可能性。     

网状WDM网中多播业务的共享保护设计

研究网状波分复用(WDM)光网络中动态多播业务的保护方案,提出一种共享保护和重配置(SPR)算法.该算法根据网络状态动态调整链路代价,为每个多播业务请求建立最小代价工作树,并为光树上互不重叠的工作段提供链路分离的保护段.当网络中发生链路失效时,进行业务段保护切换和局部资源重配置.仿真表明,该算法可以合理共享波长资源、平衡网络负载,有效保护WDM网中任意单链路失效,并在多链路失效情况下大大提高业务恢复能力.     

WDM疏导网络中一种新的多播业务路由算法

研究了波分复用(WDM)网状网中动态多播业务量疏导,提出一种新的辅助疏导模型,其可以描述当前网络资源状况和节点分光特点,并动态更新.进而提出一种有效的多播业务量疏导启发式算法(MGA),将业务的多播选路和波长分配同时完成.仿真表明,该算法在波长连续性限制、网络波长和节点收发器数目有限的情况下,具有较低网络阻塞率.     

一种移动Ad hoc环境下的LBS位置保护算法的研究

传统的基于位置信息的服务(LBS)的隐私保护需要LBS提供者(简称LSP)与用户之间通过第三方作为中介来进行信息交换,但这种模式极易遭到攻击者攻击。为此提出一种基于K-匿名机制的隐形空间算法KABSCA(k-anonymity based spatial cloaking algorithm),通过移动设备独立建立一个分布式网络直接与LSP通讯进而避免了第三方的安全威胁。仿真实验显示:使用这种算法,用户可以享受到高质量的信息服务以及高度的隐私保护。     

离散余弦变换的改进的算术傅立叶变换算法

离散余弦变换(DCT)是数字图像处理等许多领域的重要数学工具.本文通过一种新的傅立叶分析技术——算术傅立叶变换(AFT)来计算DCT.本文对偶函数的AFT进行了改进.改进的AFT算法不但把AFT所需样本点数减少了一半,从而使所需加法计算量减少了一半,更重要的是它建立起AFT和DCT的直接联系,因而提供了适合用于计算DCT的AFT算法.本文推导了用改进的AFT计算DCT的算法并对算法进行了简要的分析.这种算法的乘法量仅为O(N),并且具有公式一致,结构简单,易于并行,适合VLSI设计等特点,为DCT的快速计算开辟了新的途径.     

IP/MPLSoverWDM网中基于共享风险链路组限制的共享通路保护算法

本文研究了IP/MPLS over WDM网中,如何建立两条共享风险链路组(SRLG)分离的标记交换路径(LSP)问题,提出一种新的基于SRLG分离的共享通路保护算法.该算法既可以保证用户业务的可靠性要求,同时又能够有效提高全网的资源利用率,从而大大降低全网LSP建立请求的阻塞率.本文还对所提算法进行了仿真研究,并给出了仿真结果.     

光突发交换网络中基于标记可抢占的调度算法

根据光突发交换(OBS)网络核心节点的结构和功能 特点,分析了OBS网络核心节点的数据信道 调度算法,提出了一种新的基于标记可抢占调度算法(LPSA),并讨论和分析了算法的实 现过程。本文算法根据到达核心节点的控制包所属业务等级的突发数据(OB)包占用的网络带 宽决定 数据信道调度的方法,实现了合理的使用数据信道和各业务类别间的业务区分,最终达到改 善OBS网络性能的目的。     

基于空间递推的毫米波信道一致性仿真算法研究

根据鸟巢28 GHz信道测量数据,提出了 一种基于空间递推的空间一致性信道大尺度参数(large-scale parameter,LSP)生成算法——空间递推算法(spatial recursion algorithm,SRA),并与传统的 WINNER Ⅱ 算法进行了比较.SRA利用多维正态分布,通过特定的递推算法依...     

IP over WDM网中的策略路由算法

业务量工程允许管理者通过赋予业务主干不同的业务量工程属性来体现一定的管理策略,在为业务主干建立标记交换路径(LSP)时也应该考虑这些策略的影响,该文讨论了业务主干具有不同优先权属性时的 LSP建立问题,针对中断 LSP个数最少和中断业务量最小两种指标,分别提出不同的解决策略:最小连接数中断法(MCNIM)和最小连接带宽中断法(MCBIM),并在不同负载的动态业务下对所提算法进行了仿真研究,给出了仿真结果。     

Reconfiguration and Dynamic Load Balancing in Broadcast WDM Networks*

In optical WDM networks, an assignment of transceivers to channels implies an allocation of the bandwidth to the various network nodes. Intuition suggests, and our recent study has confirmed, that if the traffic load is not well balanced across the available channels, the result is poor network performance. Hence, the time-varying conditions expected in this type of environment call for mechanisms that periodically adjust the bandwidth allocation to ensure that each channel carries an almost equal share of the corresponding offered load. In this paper we study the problem of dynamic load balancing in broadcast WDM networks by retuning a subset of transceivers in response to changes in the overall traffic pattern. Assuming an existing wavelength assignment and some information regarding the new traffic demands, we present two approaches to obtaining a new wavelength assignment such that (a) the new traffic load is balanced across the channels, and (b) the number of transceivers that need to be retuned is minimized. The latter objective is motivated by the fact that tunable transceivers take a non-negligible amount of time to switch between wavelengths during which parts of the network are unavailable for normal operation. Furthermore, this variation in traffic is expected to take place over larger time scales (i.e., retuning will be a relatively infrequent event), making slowly tunable devices a cost effective solution. Our main contribution is a new approximation algorithm for the load balancing problem that provides for tradeoff selection, using a single parameter, between two conflicting goals, namely, the degree of load balancing and the number of transceivers that need to be retuned. This algorithm leads to a scalable approach to reconfiguring the network since, in addition to providing guarantees in terms of load balancing, the expected number of retunings scales with the number of channels, not the number of nodes in the network.     

用于超宽带高分辨率成像的二维稀疏MIMO面阵拓扑结构研究

分析并总结了超宽带二维多输入多输出(Multiple Input Multiple Output, MIMO)面阵拓扑结构设计的两条原则——等效孔径的均匀性与无明显遮蔽性, 并根据这两条原则提出了一种用于超宽带近距离高分辨率成像的新型面阵拓扑结构.与尺寸、阵元数相同的MIMO面阵相比, 该新型面阵结构在仿真获取的方向图中具有更好的聚焦效果和旁瓣抑制能力.并且, 不同距离下的聚焦结果显示, 该面阵的峰值旁瓣水平均要低于另两个阵列2 dB以上.对复杂目标成像的实验结果进一步证明了该阵列良好的成像性能.结合其等效阵元数量较少的特点, 文中提出的这种新型MIMO面阵拓扑结构为高效、实时的超宽带近距离高分辨率成像应用提供了可能.     

Design considerations for transceiver-limited elastic optical networks

The continuous increase of data traffic for present-day applications necessitates the development of Elastic Optical Networks (EONs). Significant advancements in efficient Routing and Spectrum Assignment (RSA) algorithms for EONs have been noticed in the recent past. These existing algorithms did not mention constraints on the number of transceivers per node in a network. However, for the planning of a realistic network, it is necessary to estimate the number of transceivers required at each node for the efficient operation of a network. Therefore, transceiver constraints should be taken into account while designing the RSA algorithms. In this paper, we present the impact of putting a limit to the number of transmitters and receivers available at each node of an EON. Moreover, the cost of a network heavily depends on the number of transceivers that each node in the network may offer. Hence, estimating the required number of transceivers per node in a network is vital to approximate the design cost of a network. Here, we present an Integer Linear Programming (ILP) formulation that includes the transceiver constraints and also develop a transceiver-aware heuristic algorithm for routing and spectrum assignment in EONs. Simulation results help us provide a proper design tool to estimate the number of transceivers per node in elastic optical networks.

     

Incremental Redundancy and Link Adaptation in Wireless Local Area Networks Using Residue Number Systems

The paper explores the use of residue number systems (RNS) to incorporate incremental redundancy (IR) and link adaptation (LA) in wireless communication systems. This also explores the use of RNS to increase the transmission data rate and to enhance the privacy of a wireless network. By exploiting IR and LA further, one can design an appropriate coding scheme for transmission at the currently experienced SNR level. The proposed method is implemented in existing wireless local area network (WLAN) standards and simulated extensively to find its suitability. The results of simulation studies are discussed in details.     

Performance analysis of MIMO cognitive amplify‐and‐forward relay networks with orthogonal space–time block codes

In this paper, we study the performance of multiple‐input multiple‐output cognitive amplify‐and‐forward relay networks using orthogonal space–time block coding over independent Nakagami‐m fading. It is assumed that both the direct transmission and the relaying transmission from the secondary transmitter to the secondary receiver are applicable. In order to process the received signals from these links, selection combining is adopted at the secondary receiver. To evaluate the system performance, an expression for the outage probability valid for an arbitrary number of transceiver antennas is presented. We also derive a tight approximation for the symbol error rate to quantify the error probability. In addition, the asymptotic performance in the high signal‐to‐noise ratio regime is investigated to render insights into the diversity behavior of the considered networks. To reveal the effect of network parameters on the system performance in terms of outage probability and symbol error rate, selected numerical results are presented. In particular, these results show that the performance of the system is enhanced when increasing the number of antennas at the transceivers of the secondary network. However, increasing the number of antennas at the primary receiver leads to a degradation in the secondary system performance. Copyright © 2014 John Wiley & Sons, Ltd.     

High-resolution background calibrated ADCs for software-defined radios

Next-generation transceivers operating with different standards require the existence of a wide bandwidth and highly linear analog-to-digital converters (ADCs) to enable software-defined radios (SDR). Several methods dealing with the design and implementation of high-resolution and high-speed ADCs to provide the stringent requirements of the wide-bandwidth transceivers are presented. A special focus is made on pipelined ADC for its superior performance in terms of speed and resolution. A digital background calibration technique to compensate for the capacitors mismatch, and the finite opamps gain is presented. Low overhead digitally oriented technique to increase the speed of the ADC beyond the technological limits by overcoming the problems of the conventional time-interleaving is also presented. Simulation results prove the effectiveness of these techniques.     

Optimal Transceiver Scheduling in WDM/TDM Networks

In this paper, we study the benefits of using tunable transceivers for reducing the required number of electronic ports in wavelength-division-multiplexing/time-division multiplexing optical networks. We show that such transceivers can be used to efficiently “groom” subwavelength traffic in the optical domain and so can significantly reduce the amount of terminal equipment needed compared with the fixed-tuned case. Formulations for this “tunable grooming” problem are provided, where the objective is to schedule transceivers so as to minimize the required number of ports needed for a given traffic demand. We establish a relationship between this problem and edge colorings of graphs which are determined by the offered traffic. Using this relationship, we show that, in general, this problem is NP-complete, but we are able to efficiently solve it for many cases of interest. When the number of wavelengths in the network is not limited, each node is shown to only require the minimum number of transceivers (i.e., no more transceivers than the amount of traffic that it generates). This holds regardless of the network topology or traffic pattern. When the number of wavelengths is limited, an analogous result is shown for both uniform and hub traffic in a ring. We then develop a heuristic algorithm for general traffic that uses nearly the minimum number of transceivers. In most cases, tunable transceivers are shown to reduce the number of ports per node by as much as 60%. We also consider the case where traffic can dynamically change among an allowable set of traffic demands. Tunability is again shown to significantly reduce the port requirement for a nonblocking ring, both with and without rearrangements.     

DFT-modulated filterbank transceivers for multipath fading channels

The orthogonal frequency division multiplexing (OFDM) transceiver has enjoyed great success in many wideband communication systems. It has low complexity and robustness against multipath channels. It is also well-known that the OFDM transceiver has poor frequency characteristics. To get transceivers with better frequency characteristics, filterbank transceivers with overlapping-block transmission are often considered. However these transceivers in general suffer from severe intersymbol interference (ISI) and high complexity. Moreover costly channel dependent post processing techniques are often needed at the receiving end to mitigate ISI. We design discrete Fourier transform (DFT) modulated filterbank transceivers for multipath fading channels. The DFT modulated filterbanks are known to have the advantages of low design and implementation cost. Although the proposed transceiver belongs to the class of overlapping-block transmission, the only channel dependent part is a set of one-tap equalizers at the receiver, like the OFDM system. We show that for a fixed set of transmitting or receiving filters, the design problem of maximizing signal-to-interference ratio (SIR) can be formulated into an eigenvector problem. Experiments are carried out for transmission over random multipath channels, and the results show that satisfactory SIR performance can be obtained.     

Filterbank transceivers optimizing information rate in blocktransmissions over dispersive channels

Optimal finite impulse response (FIR) transmit and receive filterbanks are derived for block-based data transmissions over frequency-selective additive Gaussian noise (AGN) channels by maximizing mutual information subject to a fixed transmit-power constraint. Both FIR and pole-zero channels are considered. The inherent flexibility of the proposed transceivers is exploited to derive, as special cases, zero-forcing (ZF) and minimum mean-square error receive filterbanks. The transmit filterbank converts transmission over a frequency-selective fading channel, affected by additive colored noise, into a set of independent flat fading subchannels with uncorrelated noise samples. Two loading algorithms are also developed to distribute transmit power and number of bits across the usable subchannels, while adhering to an upper bound on the bit error rate (BER). Reduction of the signal-to-noise ratio (SNR) margin required to satisfy the prescribed BER is achieved by coding each subchannel's bit stream. The potential of the proposed transceivers is illustrated and compared to discrete multitone (DMT) with simulated examples     

ISI-free FIR filterbank transceivers for frequency-selectivechannels

Discrete multitone modulation transceivers (DMTs) have been shown to be very useful for data transmission over frequency-selective channels. The DMT scheme is realized by a transceiver that divides the channel into subbands. The efficiency of the scheme depends on the frequency selectivity of the transmitting and receiving filters. The receiving filters with good stopband attenuation are also desired for combating narrowband noise. The filterbank transceiver or discrete wavelet multitone (DWMT) system has been proposed as an implementation of the DMT transceiver that has better frequency band separation, but usually, intersymbol interference (ISI) cannot be completely cancelled in these filterbank transceivers, and additional equalization is required. We show how to use over interpolated filterbanks to design ISI-free FIR transceivers. A finite impulse response (FIR) transceiver with good frequency selectivity can be designed, as demonstrated by the design examples