分布式控制光网络的一种高效信令协议

为了在光网络中建立连接,信令协议需要依次配置路径沿途节点上的光交叉矩阵完成.提出了一种高效的信令协议,使各节点的光交叉矩阵的切换过程并行完成,可在光网络中实现快速光路供给.在分布式离散时间仿真平台上所做出的深入仿真结果表明此信令协议能够获得比反向预留信令协议更好的网络性能,可获得更低的阻塞概率、更短的平均连接时间和最长连接时间,尽管可能付出了稍高一些的控制带宽的代价.     

Routing and wavelength assignment algorithms for multiclass WDM optical networks

In this paper dynamic routing and wavelength assignment strategies have been proposed for multiclass WDM optical networks. Multiclass optical networks provide multiple classes of services to the subscriber according to the requirement, which in turn increase operational profitability. Each class of service could be characterized by parameters like number of wavelengths, expected call holding time and average arrival rate of request. The proposed strategies have been analyzed and compared with existing strategies on the basis of blocking probabilities for multiclass traffic scenarios. Simulation results on different network topologies demonstrate that the performance of proposed strategies “Fixed shortest/alternate shortest path routing with wavelength reservation (FSASWR)” and “Fixed alternate shortest path routing with least priority wavelength assignment (FASPL)” are much better as compared to existing strategies. Proposed strategies minimize blocking probability of the multiclass network using limited number of wavelengths.     

LC-DLA: A fair congestion-aware Distributed Lightpath Allocation mechanism

One of the main challenges in all-optical WDM networks is the problem of Routing and Wavelength Assignment (RWA). In large-scale networks with heavy traffic load, distributed RWA is more suitable than centralized RWA. One of the distributed algorithms proposed recently is Distributed Lightpath Allocation (DLA) [1]. We use the DLA as our basic algorithm to design a new congestion-aware RWA algorithm, called Least-Congested Distributed Lightpath Allocation (LC-DLA). We consider congestion in the network as a decision point for solving RWA. Selection of the least congested path among available paths from source to destination can improve the blocking probability of the network. Fairness is one of the crucial metrics that network designers should consider. We define a new concept for fairness in RWA. Our performance evaluations show that LC-DLA can provide good blocking and fairness performances in WDM networks.     

Double-link failure protection algorithm for shared sub-path in survivable WDM mesh networks

We propose a novel shared sub-path protection (SSPP) algorithm to protect the double-link failures in wavelength division multiplexing (WDM) mesh networks. SSPP segments the primary path into several equal-length sub-paths and searches two link-disjoint backup paths for each sub-path. When computing the paths, SSPP considers the load balance and the resource sharing degree, so that the blocking ratio can be effectively reduced. The simulation results show that SSPP not only can completely protect the double-link failures but also can make the tradeoffs between the resource utilization ratio (or blocking ratio) and the protection-switching time.     

Routing and wavelength assignment in WDM networks with dynamic link weight assignment

We consider the routing and wavelength assignment problem on wavelength division multiplexing networks without wavelength conversion. When the physical network and required connections are given, routing and wavelength assignment (RWA) is the problem to select a suitable path and wavelength among the many possible choices for each connection such that no two paths using the same wavelength pass through the same link. In wavelength division multiplexing (WDM) optical networks, there is need to maximize the number of connections established and to minimize the blocking probability using limited resources. In this paper, we have proposed three dynamic link weight assignment strategies that change the link weight according to the traffic. The performance of the existing trend and the proposed strategies is shown in terms of blocking probability. The simulation results show that all the proposed strategies perform better than the existing trend.     

智能光网络中一种新型的分布式恢复方法

提出了一种基于固定备用路由和目的端触发的智能光网络中的分布式恢复方法,所选择的任一对源端节点和目的的端节点之间的固定备用路由包括该节点对之间的k条最短路径路由和基于部分链路无关的路由.目的端节点一旦探测到业务通道的失效将立即启动恢复进程,根据网络当前的资源使用情况,在这些备用路由中按照一定的次序选择一条恢复路由并为此分配一条可用的波长(对于没有波长变换器的光网络),然后将恢复通道的建立请求消息发送给该恢复通道的相关节点,这些相关节点可以锁定相关的网络资源,以避免来自其他恢复通道的竞争.所提出的算法增加了固定备用路由的数量,从仿真结果可以看出,该方法明显改善了失效连接的阻塞性能.     

System of mobile agents to model social networks

We propose a model of mobile agents to construct social networks, based on a system of moving particles by keeping track of the collisions during their permanence in the system. We reproduce not only the degree distribution, clustering coefficient, and shortest path length of a large database of empirical friendship networks recently collected, but also some features related with their community structure. The model is completely characterized by the collision rate, and above a critical collision rate we find the emergence of a giant cluster in the universality class of two-dimensional percolation. Moreover, we propose possible schemes to reproduce other networks of particular social contacts, namely, sexual contacts.     

Dynamic protected lightpath provisioning in mesh WDM networks

This paper investigates the problem of dynamic protected lightpath services provisioning in optical mesh networks employing wavelength division multiplexing (WDM). A variety of schemes for dynamic protected services provisioning have been proposed, supporting a range of tradeoffs among restoration speed, capacity efficiency, and scalability. In this paper, we propose a novel scheme, called p-cycles-based maximum protected working capacity envelope (PC-MPWCE), which can offer an attractive combination of fea-tures: ring-like speed, mesh-like capacity efficiency, and good scalability. To evaluate the performance of PC-MPWCE, we compare it via simulation with 1 + 1 automatic protection switching (APS) and two well-known shared backup path protection (SBPP) on NSFNET. Our simulation results show that PCMPWCE can achieve much better blocking performance than 1 + 1 APS, and perform the similar blocking performance and capacity efficiency as SBPP.     

Neutron diffraction study of the magnetic structure of Na2 RuO 4

We present a novel model to simulate real social networks of complex interactions, based in a system of colliding particles (agents). The network is build by keeping track of the collisions and evolves in time with correlations which emerge due to the mobility of the agents. Therefore, statistical features are a consequence only of local collisions among its individual agents. Agent dynamics is realized by an event-driven algorithm of collisions where energy is gained as opposed to physical systems which have dissipation. The model reproduces empirical data from networks of sexual interactions, not previously obtained with other approaches.     

Blocking probability analysis model for flexible spectrum optical networks

Compared to the traditional wavelength division multiplexing （WDM） optical networks with rigid and coarse granularities, flexible spectrum optical networks have high spectrum efficiency, which can support the service with various bandwidth requirements, such as sub and super channel. Among all network performance parameters, blocking probability is an important parameter for the performance evaluation and network planning in circuit~based optical networks including flexible spectrum optical networks. We propose an analytical method of blocking probability computation for flexible spectrum optical networks in this letter through mathematical analysis and theoretical derivation. Two blocking probability models are built respectively based on whether considering spectrum consecutiveness or not. Numerical results validate our proposed blocking probability models under different link capacity and traffic loads.     

HEAVY ION COLLISION DYNAMICS IN FERMI DOMAIN (I) DYNAMICS DEPENDENCE OF ENERGY

In the case of central collisions,the collision mechanism of complete,incomplete fusion,and fragmentation were systematically studied via the Boltzmann-Uehling-Uhlenbeck theory which included the nuclear mean field dynamics,two-body collisions,and Pauli blocking between 5 and 150MeV/u for ²⁰Ne+²⁰Ne collision system.How the mean field,Pauli blocking of the two-body collisions were affected by bombarding energy and their effect on the reaction mechanism was discussed.     

Pauli blocking and Fermi motion effects in ion-ion collisions

A geometrical model for Pauli blocking and Fermi motion effects in ion-ion collisions is presented. The results, given as effective nucleon-nucleon total cross sections, incicate that the Pauli blocking reduces the nucleon-nucleon cross section in the ion-ion environment by a larger amount than previously estimated.     

Generic-II routing and wavelength assignment algorithm for a wavelength-routed WDM network

In this paper, we have developed a Generic routing and wavelength assignment algorithm (Generic RWA-II) which is used for the calculation of blocking probability of network. A simple mathematical model has also been proposed for the optimization and minimization of blocking probability. The implementation of the proposed model and algorithm has less complexity and the computation used in this model is quite efficient. This paper suggests an optimum path and assigns wavelength to that path, as a solution to routing and wavelength assignment problem to have least blocking probability. This model can be implemented on different network topologies. Further, the model is also used to evaluate the blocking performance of a 6-node simple network topology and hence used to improve its performance on the basis of blocking probability.     

Parallel signaling-based fast restoration scheme in distributed optical networks

The fast parallel restoration （FPR） scheme is proposed to achieve the fast setup of restoration label switched path （LSP） in the distributed optical networks. The scheme is derived by dividing the whole restoration LSP into several segments of sub-LSP and triggering each sub-LSP along the new route to finish the signaling procedure concurrently, and subsequently merging all sub-LSPs into a whole LSP. The theoretical analysis and simulation results show that the FPR scheme outperforms the other two typical restoration schemes in terms of connection setup time.     

An efficient fault localization or detection mechanism for high speed optical networks

Optical burst switching (OBS) has been considered as the gate through which the envisaged world of optical Internet will be conquered by implementing Internet Protocol (IP) software directly over a wavelength-division-multiplexing (WDM) optical layer (IP/WDM). The main feature for designing next generation optical networks is protecting and restoring high capacity WDM networks from the failures. Quick detection, identification and restoration make networks more strong and consistent even though the failures cannot be avoided. Hence, it is necessary to develop fast, efficient and dependable fault localization or detection mechanisms. In this paper, an efficient scheme for OBS networks has been proposed to provide fast restoration of links with minimum delay as well as blocking probability. By simulation results, it is shown that the proposed OBS scheme achieve less blocking probability and delay while getting higher throughput in comparison to conventional schemes.     

Blocking in wavelength-routed all-optical WDM network with wavelength conversion

The blocking probability in wavelength-routed all optical networks is very important measure of performance of the network, which can be affected by many factors such as network topology, traffic load, number of links, algorithms employed and whether wavelength conversion is available or not. In this paper, we have proposed a mathematical model to reduce the blocking probability of the WDM optical network for wavelength-convertible networks. The model can be used to evaluate the blocking performance of any network topology also it can be useful to improve its blocking performance of the given network topology. The blocking probability variation of the network for a particular load (per link) has been studied based on the load variation and total number of wavelengths used in the network. This model gives good results for high load (per link).     

A Device-to-Device direct discovery algorithm to mitigate the collision caused by hidden users

Device-to-Device (D2D) discovery is an essential constituent in D2D communications as a future generation of wireless communication networks. Direct discovery enables users to discover their neighbors to exchange traffic without the cellular-networks assistance in order to enhance spectral efficiency and throughput. Despite its role to reduce signaling load, few works pay sufficient attention to direct discovery. According to the latest density of users detected by User Equipments (UEs) and their neighbors, this study suggests an adaptable, neighborhood-aware D2D direct discovery technique. To distinguish concealed UEs from other UEs, this technique employs a novel classification method. It also uses its neighborhood-aware capability to avoid severe collisions among all users, including hidden users. The performance of the proposed algorithm is compared with the recent adaptive algorithms and the algorithm recommended by the 3GPP standard. We evaluate algorithms in metrics such as discovery delay and the number of beacons required to terminate the discovery process. The simulation results show that the number of beacons, collision, and discovery delay considerably decrease via the proposed algorithm.     

Blocking in wavelength-routed all-optical WDM network with or without wavelength conversion

The blocking probability in wavelength-routed all-optical networks is a very important measure of performance of the network. This blocking probability can be affected by many factors such as network topology, traffic load, number of links, algorithms employed and whether wavelength conversion is available or not. In this paper we have proposed a mathematical model to reduce the blocking probability of the WDM optical network for both wavelength convertible networks as well as for wavelength non-convertible networks. The model is can be used to evaluate the blocking performance of any network topology also it can be useful to improve its performance of the given network topology.     

A novel hop constrained sub-path protection routing algorithm in WDM networks

The survivable design is a key issue in reliable WDM optical networks to assure the service guarantee to customers. The sub-path protection metrics can achieve shorter failure recovery time than path protection metrics for a modest sacrifice in resource utilization. Rather than the conventional equal-length sub-path protection metrics (CDR algorithm), in this paper we propose a novel heuristic dynamic hop constrained sub-path protection (HCSPP) routing algorithm to provide a more flexible way to compute the primary sub-paths and the backup sub-paths. The main idea of HCSPP is that we first compute the primary path and its end-to-end backup path, the found primary and its end-to-end backup path constitute a protection cycle, then we partition the protection cycle into several smaller protection cycles by the straddling paths we introduced, the hop count for each small protection cycle should be constrained in a threshold value and the value can be adjusted according to different network topologies or different management policy, thus we can control the tradeoff between the failure recovery time and the resource utilization ratio. Compared with the CDR [P.-H. Ho, J. Tapolcai, T. Cinkler, IEEE/ACM Trans. Networking 12 (6) (2004) 1105] algorithm, HCSPP can achieve a better compromise between the blocking probability and the failure recovery time. We evaluate the effectiveness of the HCSPP and the results are found to be promising.     

A heuristic priority based wavelength assignment scheme for optical networks

We propose a heuristic priority based wavelength assignment (HPWA) scheme to minimize the blocking probability. In this scheme, the connection requests having same s–d pair are groomed first and then these groomed connection requests are served for routing and wavelength assignment according to their priority order. The priority order of each groomed connection request is estimated based on both the types of path (direct link physical path or in-direct link physical path) first and then their traffic volume. The performance analysis of our proposed scheme is made in terms of blocking probability and compared the same with similar heuristic non-priority based wavelength assignment (HNPWA) scheme. Simulation study shows that the blocking probability of HPWA scheme is less than that of NPRWA. It is also seen that the performance of the proposed scheme is better in comparison to HNPWA, when the number of connection requests increases in the network.