CCII-Based Continuous-Time Current-Mode Biquad Filter

ＣＣＩ┐ＢａｓｅｄＣｏｎｔｉｎｕｏｕｓ┐ＴｉｍｅＣｕｒｅｎｔ┐ＭｏｄｅＢｉｑｕａｄＦｉｌｔｅｒＭａｎｕｓｃｒｉｐｔｒｅｃｅｉｖｅｄＪｕｎ．２９，１９９６．Ｔｈｉｓｗｏｒｋｉｓｓｕｐｐｏｒｔｅｄｂｙｔｈｅｓｃｉｅｎｃｅａｎｄｔｅｃｈｎｏｌｏｇｙｆｏｕｎ...     

低功耗应用中的M.Core和ARM处理器

在低功耗应用领域，Ｍｏｔｏｒｏｌａ的Ｍ·Ｃｏｒｅ处理器向ＡｄｖａｎｃｅｄＲＩＳＣＭａｃｈｉｎｅ公司的ＡＲＭ简短指令结构处理器提出了挑战。虽然ＡＲＭ７和Ｍ·Ｃｏｒｅ作为独立的ＩＰ（即拥有知识产权的模块设计）方案，都采用了逻辑核芯做为专用集成电路构建模块...     

A Blind Equalizer Based on Unsupervised Gaussian Cluster Formation with an Adaptive Non-Linearit

ＡＢｌｉｎｄＥｑｕａｌｉｚｅｒＢａｓｅｄｏｎＵｎｓｕｐｅｒｖｉｓｅｄＧａｕｓｉａｎＣｌｕｓｔｅｒＦｏｒｍａｔｉｏｎｗｉｔｈａｎＡｄａｐｔｉｖｅＮｏｎ┐ＬｉｎｅａｒｉｔｙＬｉｕＨａｎｙｕ（ＤｅｐｔｏｆＥｌｅｃｔｒｉｃａｌａｎｄＣｏｍｐｕｔｅｒＥｎｇｉｎ...     

无线mesh网中最小编码代价低时延多播路由

提出了一种无线mesh网中最小网络编码代价低时延多播路由协议(MNCLDMR, minimal network coding and low delay multicast routing)。MNCLDMR的目标是选择合适的网络编码节点,最小化网络编码代价,降低网络时延。MNCLDMR主要思想是引入拓扑关键节点和网络编码关键节点的概念,以下一跳的节点是否是网络编码关键节点或拓扑关键节点作为路由判据,采用MNCLD算法构造多播树。仿真结果表明,MNCLDMR可以达到预定目标,合理形成网络编码机会,能实现最小网络编码代价低时延多播路由。     

一种传感器网络的分布式多播路由优化算法

传感器感知的信息需要通过网络传送给感兴趣目标节点,传统网络中的多播技术往往能耗高、实时性不够理想,不利于在传感器网络中使用。针对 WSN中节点对网络拓扑未知,该文先将多播路由问题演化为最优多播路径问题,通过启发式算法求解分布式最优路径,并通过一种基于贪婪思想的裁剪合并策略优化多播路由树,直至整个网络得到最优路径,最后并结合了节点区域集中以及无线多播特性,提出了 DCast 路由算法。最后通过仿真实验与uCast, SenCast等经典的传感器网络的多播路由算法仿真比较,可以得出其算法在时延性以及能耗等方面性能有优势。     

时延受限低代价的一种组播路由动态算法

提出了一种适合目的节点动态加入的、时延受限低代价多播路由的启发式算法DLHMA算法。该算法基于MPH算法的基本思想进行扩展,在满足时延限制条件和多播树代价增加最小的基础上,逐步将目的节点添加到多播树上。最后,证明了算法的正确性,分析了算法的动态性,并进行了仿真实验。结果表明,该算法可以实现新加目的节点的动态加入,并保证所获得多播树的低代价。     

IP多播中的路由技术

多播（ｍｕｌｔｉｃａｓｔ）是未来Ｉｎｔｅｒｎｅｔ中的一项重要业务。多播路由技术建立在点到点路由技术的基础上,但在寻路机制和路由结构上有很大区别。本文介绍了ＩＰ多播机制、路由树的类型,以及目前已经应用的典型协议。     

IP多播中的路由技术

多播（ｍｕｌｔｉｃａｓｔ）是未来Ｉｎｔｅｒｎｅｔ中的一项重要业务。多播路由技术建立在点到点路由技术的基础上,介在寻路机制和路由结构上有很大区别。本介绍了ＩＰ多播机制、路由树的类型,以及目前已经应用的典型协议。     

平面网络中QOS多播路由算法研究与设计

多播通信这种兼顾了广播通信与单播通信两者优点的通信模式,已经被越来越多地应用于平面网络业务之中。首先讨论了面向源节点的多播路由策略。在分析传统多播路由算法中最佳链路选择函数的基础上,提出了一个新的最佳路由模型和QMRI算法,该算法成功地解决了网络中多播节点动态变化时的QOS路由选择问题。     

网络多播路由的改进编码软件设计与实现

传统网络多播路由编码方法采用多播分布树进行编码,但链路容量遭遇瓶颈,致使编码节点较多,导致浪费带宽资源的问题。在此提出基于Koetter指数时间的网络多播路由改进编码算法对编码软件进行设计,分析多播路由的总体设计,通过数据包编码转发模块在多播拓扑不相交路径上进行编码和转发多播数据包,利用输入模块实现网络多播路由和上游节点的信息交换,通过开关仲裁模块判断能够向特定输出端口传输信息的输入端口,利用死锁控制模块对出现死锁现象的路由节点进行检测,一段时间后使多播路由恢复正常的数据交换,通过输出模块对数据的输出进行管理。以降低带宽资源为目的,采用Koetter指数时间算法实现网络多播路由编码,并给出编码的详细代码。实验结果表明,所提方法不仅节省网络资源,而且显著降低多播路由时延,增强网络吞吐量。     

Minimizing the Number of Multicast Transmissions in Single-Hop WDM Networks

The problem of minimizing the number of transmissions for a multicast transmission under the condition that the packet delay is minimum in single-hop wavelength division multiplexing (WDM) networks is studied in this paper. This problem is proved to be NP-complete. A heuristic multicast scheduling algorithm is proposed for this problem. Extensive simulations are performed to compare the performance of the proposed heuristic algorithm with two other multicast scheduling algorithms, namely, the greedy and no-partition scheduling algorithms. The greedy algorithm schedules as many destination nodes as possible in the earliest data slot. The no-partition algorithm schedules the destination nodes of a multicast packet to receive the packet in the same data slot without partitioning the multicast transmission into multiple unicast or multicast transmissions. Our simulation results show that (i) an algorithm which partitions a multicast transmission into multiple unicast or multicast transmissions may not always produce lower mean packet delay than the no-partition algorithm when the number of data channels in the system is limited and (ii) the proposed heuristic algorithm always produces lower mean packet delay than the greedy and the no-partition algorithms because this algorithm not only partitions a multicast transmission into multiple unicast or multicast transmissions to keep the packet delay low but also reduces the number of transmissions to conserve resources.     

一种支持单播与组播混合业务的高速Crossbar调度算法

当前在高速crossbar中支持单、组播混合业务调度的实用算法一般采用请求-许可-接受的处理流程(例如ESLIP算法)。研究发现,该类算法中存在单、组播许可相互阻塞现象,造成调度效率降低。从实用性出发,该文提出了一种新的支持单、组播混合业务的调度算法ERGRR(Extended Request-Grant-based Round- Robin),通过简化调度处理流程,克服了许可阻塞现象,提高了系统吞吐量、时延等性能。仿真结果表明,在单、组播混合业务流下,ERGRR算法吞吐量、时延等性能优于ESLIP算法。另外,ERGRR算法具有更好的公平性以及更加易于硬件实现。     

Directional core selection approach and dynamic tree reorganization for delay and delay variation multicast routing

Multicast communication constrained by end‐to‐end and interdestination delay variation is known as delay and delay variation–bounded multicast. These constraints are salient for real‐time multicast communications. In this paper, we propose a directional core selection algorithm for core selection and delay variation–bounded multicast tree generation. Another algorithm, based on k‐shortest paths, is proposed to further decrease the interdestination delay variation of the trees generated by directional core selection. We also propose the dynamic version of both algorithms that respond to dynamic join and leave requests to the ongoing multicast session by reorganizing the tree and avoiding session disruption. Simulations show that the proposed algorithms surpass existing algorithms in end‐to‐end delay, interdestination delay variation, execution time, and failure probability.     

Multicast routing and wavelength assignment with delay constraint in WDM networks with sparse wavelength conversions

With the developments in multimedia and other real-time group applications, the question of how to establish multicast trees satisfying Quality-of-Service (QoS) requirements is becoming a very important problem. In this paper, multicast routing and wavelength assignment with delay constraint (MCRWA-DC) in wavelength division multiplexing (WDM) networks with sparse wavelength conversions is studied. We propose a colored multigraph model for the temporarily available wavelengths. Based on this colored multigraph model, two heuristic algorithms are proposed to solve the MCRWA-DC problem. The proposed algorithms have the following advantages:(1) finish multicast routing and wavelength assignment in one step; (2) the total cost of the multicast tree is low; (3) the delay from the source node to any multicast destination node is bounded; and (4) locally minimize the number of wavelength conversions and the number of different wavelengths used to satisfy a multicast request. Simulation results show that the proposed algorithms work well and achieve satisfactory blocking probability.     

Performance analysis of multicast flow control algorithms overcombined wired/wireless networks

A multicast flow control framework for data traffic traversing both a wired and wireless network is proposed. Markov-modulated fluid (MMF) models are used for the receivers to capture the dynamics of the wireless links. Our study shows that the phase differences of the instantaneous throughput capabilities of the receivers are a distinctive feature of multicast connections. The objectives of the multicast flow control algorithms are to cope with the receiver phase differences (RPDs) cost effectively in addition to the general goals such as maximizing throughput and minimizing delay. Three ad hoc algorithms have been studied: listen to slowest request (LSQ), source estimation (SE), and open-loop control. A fluid-flow analysis technique is applied to study the effect of receiver phase differences assuming zero propagation delay. The effect of propagation delay in multicast connections is then discussed. Simulation results are presented to verify the analysis for the zero-delay case and to compare the performance of the algorithms under nonnegligible delays. It turns out that the zero-delay case reveals the characteristics of the multicast algorithms and provides good performance bounds for the cases with nonnegligible propagation delays     

基于可用带宽满足时延和时延差别 约束的实时多播路由算法

实时多播路由中具有可加性的代价(Cost)不能确切反映网络本质特性,尤其不能反映路径带宽的凹性(Concave).已有基于代价的算法不能很好适应多播应用,需要新的模型和算法.本文采用可用带宽代替代价作为主要度量,并满足实时多播中二个重要约束度量:时延和时延差别.同时基于此三个度量,本文提出二种新的具有多项式复杂性的实时多播路由算法并比较其性能.新算法通过分析得到每路径时延和二约束之间的关系,有效降低涉及时延和时延差别此类问题的复杂性.新算法采用度量反映实时多播本质特性而具有实际推广性.     

A ring-based multicast routing topology with QoS support in wireless mesh networks

Wireless mesh networking (WMN) is an emerging technology for future broadband wireless access. The proliferation of the mobile computing devices that are equipped with cameras and ad hoc communication mode creates the possibility of exchanging real-time data between mobile users in wireless mesh networks. In this paper, we argue for a ring-based multicast routing topology with support from infrastructure nodes for group communications in WMNs. We study the performance of multicast communication over a ring routing topology when 802.11 with RTS/CTS scheme is used at the MAC layer to enable reliable multicast services in WMNs. We propose an algorithm to enhance the IP multicast routing on the ring topology. We show that when mesh routers on a ring topology support group communications by employing our proposed algorithms, a significant performance enhancement is realized. We analytically compute the end-to-end delay on a ring multicast routing topology. Our results show that the end-to-end delay is reduced about 33 %, and the capacity of multicast network (i.e., maximum group size that the ring can serve with QoS guarantees) is increased about 50 % as compared to conventional schemes. We also use our analytical results to develop heuristic algorithms for constructing an efficient ring-based multicast routing topology with QoS guarantees. The proposed algorithms take into account all possible traffic interference when constructing the multicast ring topology. Thus, the constructed ring topology provides QoS guarantees for the multicast traffic and minimizes the cost of group communications in WMNs.     

Algorithms for precomputing constrained widest paths and multicast trees

We consider the problem of precomputing constrained widest paths and multicast trees in a communication network. Precomputing and storing of the relevant information minimizes the computational overhead required to determine an optimal path when a new connection request arrives. We evaluate algorithms that precompute paths with maximal bandwidth (widest paths), which in addition satisfy given end-to-end delay constraints. We analyze and compare both the worst case and average case performance of the algorithms. We also show how the precomputed paths can be used to provide computationally efficient solutions to the constrained widest multicast tree problem. In this problem, a multicast tree with maximal bandwidth (widest multicast tree) is sought, which in addition satisfies given end-to-end delay constraints for each path on the tree from the source to a multicast destination.     

一种非精确状态下满足多QoS约束的 动态组播路由算法

提出了一种非精确状态下满足多QoS约束的动态组播路由算法——DMIQ,该算法采用改进的BF算法作为路径搜索算法,WFQ作为分组调度机制,链路延迟不确定且服从均匀分布,能在非精确状态且满足带宽、延迟抖动和丢包率约束的前提下确定具有最小跳数和开销的动态组播路由.仿真实验表明,DMIQ能在非精确状态且满足多QoS约束的前提下建立动态组播路由,在路由请求平均成功率、平均延迟和平均跳数等衡量指标下表现出良好的性能.     

Avoidance of multicast incapable branching nodes for multicast routing in WDM networks

In this article we study the multicast routing problem in all-optical WDM networks under the spare light splitting constraint. To implement a multicast session, several light-trees may have to be used due to the limited fanouts of network nodes. Although many multicast routing algorithms have been proposed in order to reduce the total number of wavelength channels used (total cost) for a multicast session, the maximum number of wavelengths required in one fiber link (link stress) and the end-to-end delay are two parameters which are not always taken into consideration. It is known that the shortest path tree (SPT) results in the optimal end-to-end delay, but it can not be employed directly for multicast routing in sparse light splitting WDM networks. Hence, we propose a novel wavelength routing algorithm which tries to avoid the multicast incapable branching nodes (MIBs, branching nodes without splitting capability) in the shortest-path-based multicast tree to diminish the link stress. Good parts of the shortest-path-tree are retained by the algorithm to reduce the end-to-end delay. The algorithm consists of tree steps: (1) a DijkstraPro algorithm with priority assignment and node adoption is introduced to produce a SPT with up to 38% fewer MIB nodes in the NSF topology and 46% fewer MIB nodes in the USA Longhaul topology, (2) critical articulation and deepest branch heuristics are used to process the MIB nodes, (3) a distance-based light-tree reconnection algorithm is proposed to create the multicast light-trees. Extensive simulations demonstrate the algorithm’s efficiency in terms of link stress and end-to-end delay.