Fault-tolerant architecture with dynamic wavelength and bandwidth allocation scheme in WDM-EPON

This study proposes a novel cost-based fault-tolerant WDM-EPON (CFT-WDM-EPON) to provide overall protection. It only equips a backup feeder fiber to recover the system failure. Additionally, a prediction-based fair wavelength and bandwidth allocation (PFWBA) scheme is proposed to enhance the differentiated services for WDM-EPON based on dynamic wavelength allocation (DWA) and prediction-based fair excessive bandwidth reallocation (PFEBR) from our previous work. PFEBR involves an early-DBA mechanism, which improves prediction accuracy by delaying report messages of unstable traffic optical network units (ONUs), and assigns linear estimation credit to predict the arrival of traffic during waiting time. DWA can operate in coordination with an unstable degree list to allocate the available time of wavelength precisely. Simulation results show that the proposed PFWBA scheme outperforms WDM IPACT-ST and DWBA3 in terms of packet delay, jitter performance, throughput, wasted bandwidth, gain ratio of bandwidth, and packet loss.

WDM EPON中的动态波长带宽分配算法

基于WDM EPON系统结构和已有波长带宽分配算法(DWBA)的不足,提出了一种结合流量预测与预分配机制的动态波长带宽分配算法--DWBPA.仿真表明在不同网络负载情况下,该算法不仅保证了波长带宽分配的公平性,而且能够满足高优先级业务的延时要求.     

一种基于 SLA 的 WDM EPON 动态波长带宽分配算法简

波分复用技术结合时分复用形成了混合WDM EPON,如何提高系统的带宽利用率和用户服务质量成为关键技术。结合已有算法的优缺点,提出一种新的动态波长带宽分配算法。该算法结合业务等级分类和用户服务等级协议的权重为光网络单元分配相应的带宽和波长,以达到提高服务质量、带宽分配公平性,提高上行带宽利用率和改善网络性能的目的。     

A reliable WDM optical access network enabling dynamic wavelength allocation and triple-play service

A reliable dual-fiber ring-tree wavelength-division multiplexing optical access network architecture is proposed in this paper. On the one hand, due to the use of differential phase shift keying modulation, triple-play service including point-to-point service and broadcast service is realized. On the other hand, the wavelengths can be allocated dynamically by means of the special design of the remote node. What is more important is this network architecture can provide flexible protection modes for either single or multiple failures as well. The network survivability could be improved largely.     

Performance analysis of channelized cellular systems with dynamic channel allocation

We present an analytical model to compute the blocking probability in channelized cellular systems with dynamic channel allocation. We model the channel occupancy in a cell by a two-dimensional (2D) Markov chain, which can be solved to obtain the blocking probability in each cell. We apply our analytical model to linear highway systems with and without lognormal shadowing and then extend it to 2D cellular systems with lognormal shadowing. We show that, for linear highway systems, distributed dynamic channel-allocation schemes perform similarly to the centralized dynamic channel-allocation schemes in terms of blocking probability. However, for 2D cellular systems, the improvement in the performance is significant and the reduction in the blocking probability in systems with distributed dynamic channel allocation is by almost one order of magnitude, when compared to that in systems with centralized dynamic channel allocation. In practice, our analysis of linear highway systems is applicable to Digital European Cordless Telephony (DECT) and that of 2D cellular systems is applicable to global systems for mobile communications (GSM).     

New concept in long-reach PON Planning: BER-aware wavelength allocation

With the use of arrayed-waveguide grating (AWG) and erbium-doped-fiber amplifier (EDFA), the long-reach passive optical network (LR-PON) can provide enormous bandwidth over large distances. However, these new technologies can also deteriorate the receivers' bit-error rate (BER) performance. By bringing the concept of BER-awareness into network planning, we can alleviate the performance deterioration, which could in turn lead to simpler design of receiver and thus lower the total cost of LR-PON.The effects of AWG and EDFA on BER are studied in this paper. An analytical model of BER performance is developed as a function of the output port location in the AWG and the distance of the receiver from the AWG. Not only does the proposed model capture the power loss caused by AWG, but it also accounts for several transmission impairments, including the beat noise due to inter-channel crosstalk in the AWG, the amplified spontaneous emission (ASE) noise related to EDFA, and the thermal noise related to the receiver. Based on this model, we propose both short-term and long-term distance-aware wavelength allocation schemes, which balance the BER among the optical network units (ONUs) at different distance. Simulation results show that average BER improves and the relative standard deviation decreases.     

A path-disjoint approach for blocking probability analysis in hybrid dynamic wavelength routed WDM grooming networks

The present article addresses a novel approach to enhance the overall performance of a WDM optical network. Centralized and distributed approaches for dynamic lightpath establishment are well studied in the literature. Both the approaches have some drawbacks. In this article a hybrid approach is proposed to accept the advantages and discard the disadvantages of both the approaches. With the proposed hybrid approach, a WDM optical network is divided into clusters of nodes. Within a cluster centralized mechanism is applicable whereas connection requests between the node pairs from different clusters follow the distributed mechanism. Also, in this article an analytical model is proposed to compute the expected blocking probability of the proposed hybrid network. First, blocking probabilities for the centralized and distributed approaches are computed and then it is extended for the hybrid approach. The distinguished feature of the proposed analytical model is that it efficiently utilizes the path information of the calls to determine the overall blocking probability of a WDM optical network. It extracts the necessary parameters of a network by simulation and utilize the information to analytically calculate the blocking probability of the network. The NSFNET T1 backbone network is used for the simulation study. To justify the analytical model, the simulation results are compared with that of the analytical model. The simulation results establish the effectiveness of the proposed hybrid approach over the distributed approach in merits of both the call setup time and blocking probability.     

On the performance analysis of dynamic channel allocation with FIFO handover queuing in LEO-MSS

The exact analysis of dynamic channel allocation (DCA) with first-in/first-out (FIFO) queuing of handover (QH) requests is highly complex, due to the dynamic nature of channel allocation to different cells. This letter presents an approximate but accurate analytical method to evaluate the performance of DCA in conjunction with FIFO-QH in low earth orbit mobile satellite systems. The accuracy of the proposed analysis has been verified by means of computer simulation.     

Modeling dynamic channel allocation in multicellular communicationnetworks

Future cellular mobile communication networks will exploit microcellular architectures and dynamic channel allocation in order to meet the rapidly increasing traffic demand. In this paper, an analytical model has been developed in order to evaluate the performance of maximum packing, a dynamic channel allocation scheme for cellular communication networks. Specifically, a finite number of users has been assumed, moving in a geographical region, covered by a finite set of cells. The considered users are characterized by a variable degree of mobility, which allows both variable sized cells and different user speeds to be analyzed. The model, based on queueing networks, allows the evaluation of the main system performance parameters in terms of blocking probability of new calls, handoff blocking probability, forced termination probability, unsuccessful probability, and throughput. Performance predictions are confirmed by simulation in a wide range of load conditions and user mobility     

Worst-case stability analysis of switching regulators using thestructured singular value

A method to assess the effect of component tolerances on the stability of closed-loop switching regulators is given. Use of μ, the structured singular value, is made which obviates the need for time-intensive Monte Carlo simulation runs and also guarantees the assessment of the worst-case condition of the system. Furthermore, through the use of newly developed software routines for μ, the effect of up to 100 uncertainties may be taken into account. The analysis procedure entails isolating component value uncertainties Δ from the nominal system M. Subsequent determination of μ for this Δ-M structure enables a robustness assessment to be made for the system under study. A procedure which considers uncertainties in inductor, capacitor, and resistance values is given which enables reduction of a switching regulator system to Δ-M form. An example is given of a regulator design for which an assessment is made of the allowed component tolerances which guarantees a lower limit of the phase margin     

一种TD-SCDMA系统的动态信道分配策略

提出了一种适用于TD-SCDMA系统的动态信道分配算法.该算法在进行资源整合的基础上将信道条件较好的用户分配于交叉时隙,从而达到减少交叉时隙干扰,提高频谱效率的目的.仿真结果表明该算法能够有效增加系统容量,改善系统性能.     

Performance analysis of multicast routing and wavelength assignment protocol with dynamic traffic grooming in WDM networks

The need for on‐demand provisioning of wavelength‐routed channels with service‐differentiated offerings within the transport layer has become more essential because of the recent emergence of high bit rate Internet protocol (IP) network applications. Diverse optical transport network architectures have been proposed to achieve the above requirements. This approach is determined by fundamental advances in wavelength division multiplexing (WDM) technologies. Because of the availability of ultra long‐reach transport and all‐optical switching, the deployment of all‐optical networks has been made possible. The concurrent transmission of multiple streams of data with the assistance of special properties of fiber optics is called WDM. The WDM network provides the capability of transferring huge amounts of data at high speeds by the users over large distances. There are several network applications that require the support of QoS multicast, such as multimedia conferencing systems, video‐on‐demand systems, real‐time control systems, etc. In a WDM network, the route decision and wavelength assignment of lightpath connections are based mainly on the routing and wavelength assignment (RWA). The multicast RWA's task is to maximize the number of multicast groups admitted or minimize the call‐blocking probability. The dynamic traffic‐grooming problem in wavelength‐routed networks is generally a two‐layered routing problem in which traffic connections are routed over lightpaths in the virtual topology layer and lightpaths are routed over physical links in the physical topology layer. In this paper, a multicast RWA protocol for capacity improvement in WDM networks is designed. In the wavelength assignment technique, paths from the source node to each of the destination nodes and the potential paths are divided into fragments by the junction nodes and these junction nodes have the wavelength conversion capability. By using the concept of fragmentation and grouping, the proposed scheme can be generally applied for the wavelength assignment of multicast in WDM networks. An optimized dynamic traffic grooming algorithm is also developed to address the traffic grooming problem in mesh networks in the multicast scenario for maximizing the resource utilization and minimizing the blocking probability. Copyright © 2011 John Wiley & Sons, Ltd.     

EPON中节能动态带宽分配算法

结合光网络单元(ONU)休眠控制和动态带宽分配机制,提出一种节能的双向DBA算法。该算法根据上/下行业务量为每个ONU分配合适的上/下行授权带宽,保证每个ONU在上/下行方向都具有较低的传输时延,同时尽可能增加ONU的休眠时间来降低网络能耗。仿真结果表明,与已有算法相比,该算法具有较低的上/下行平均时延,并能减少ONU的能耗。     

On dynamic wavelength assignment in wavelength-convertible multi-granular optical networks

In this paper, we study the dynamic wavelength assignment problem in waveband-switched (WBS) networks composed of wavelength-convertible multi-granular OXCs (MGOXCs). With the aim to minimize the extra port consumption and utilize wavelength converters in an efficient manner, we propose a heuristic wavelength assignment algorithm named Least Weighted Configuration Cost (LWCC).WAPG, an algorithm proposed in previous literature, is compared with LWCC in both blocking performance and converter utilization. Numerical results show that LWCC offers more benefit in waveband grouping, which results in significant improvement in terms of blocking probability.     

Performance analysis of A dynamic channel allocation technique for satellite mobile cellular networks

This paper deals with an efficient dynamic channel allocation (DCA) technique suitable for applications in mobile satellite cellular networks. A cost function is defined to allow an optimum selection of channels to be allocated on demand. A mobility model suitable for low earth orbit (LEO) satellite systems is presented. The performance of the novel DCA technique in terms of call blocking probability has been derived by simulations. The obtained results are compared with those achieved by a fixed channel allocation (FCA) technique to show a better behaviour.     

Heuristic algorithm for allocation of wavelength convertible nodesand routing coordination in all-optical networks

It is true that in all-optical networks, network performance can be improved by wavelength conversion. However, the switching node with wavelength conversion capability is still costly, and the number of such nodes should he limited in the network. In this paper, a performance optimization problem is treated in all-optical networks. We propose a heuristic algorithm to minimize an overall blocking probability by properly allocating a limited number of nodes with wavelength conversion capability. The routing strategy is also considered suitable to the case where the number of wavelength convertible nodes are limited. We validate the minimization level of our heuristic algorithm through numerical examples, and show that our algorithm can properly allocate nodes with conversion and decide routes for performance optimization     

Genetic evolutionary algorithm for optimal allocation of wavelength converters in WDM optical networks

In this article, a genetic evolutionary algorithm is proposed for efficient allocation of wavelength converters in WDM optical networks. Since wavelength converters are expensive, it is desirable that each node in WDM optical networks uses a minimum number of wavelength converters to achieve a near-ideal performance. The searching capability of genetic evolutionary algorithm has been exploited for this purpose. The distinguished feature of the proposed approach lies in handling the conflicting circumstances during allocation of wavelength converters considering various practical aspects (e.g., spatial problem, connectivity of a node with other nodes) rather than arbitrarily to possibly improve the overall blocking performance of WDM optical networks. The proposed algorithm is compared with a previous approach to establish its effectiveness and the results demonstrate the ability of the proposed algorithm to efficiently solve the problem of Optimal Wavelength Converters Allocation (OWCA) in practical WDM optical networks.

Performance analysis of channel de-allocation schemes for dynamic resource allocation in GSM/GPRS networks

Channel de-allocation for GSM voice call (DASV) has been considered for dynamic resource allocation in GSM/GPRS networks. Two new de-allocation schemes are proposed: de-allocation for GPRS packet (DASP) and de-allocation for both GSM voice call and GPRS packet (DASVP). An analytic model with general GPRS data channel requirement is derived to evaluate the performance of the schemes in terms of GSM voice call incompletion probability, GPRS packet dropping probability, average GPRS packet transmission time and channel utilisation.     

Composite-two-phase wavelength reservation scheme for dynamic optical networks

An enhanced hybrid scheme of wavelength reservation for dynamic wavelength routed optical networks is proposed. The performance of a newly introduced composite-two-phase reservation protocol (C2P-RP) is evaluated and compared with the existing hybrid reservation protocol. By offering connection requests an enhanced scope of finding an end-to-end available wavelength, the C2P-RP scheme shows improved connection-request blocking performance.     

EPON中一种改进的动态带宽分配算法

对经典的EBA算法进行了改进,提出了一种有效地利用空闲时间(idle time)来传输数据的动态带宽分配算法--N-EBA算法.仿真结果表明,N-EBA算法具有良好的平均包时延和较高的带宽利用率.