Computing approximate blocking probability in hierarchical wavelength routing optical networks

Modeling and analyzing the performance of adaptive hierarchical networks

In the future automated battle field communications will be supported in part by a hierarchical wireless network that includes: ad hoc ground radio subnets; point to point wireless long haul backbone, and; unmanned aerial vehicles (UAVs). In such a hierarchical network, nodes are generally partitioned into groups. Each group has one or more backbone nodes that provide access points to the backbone network and to UAVs. Communications between groups can thus utilize links at higher level. A critical protocol in the operation of such a large mobile network is routing. Previous research of UAV based systems has generally assumed the use of a hierarchical routing scheme, for example, extended hierarchical state routing (EHSR). However, a hierarchical scheme like EHSR has some limitations. In this paper, we extend landmark ad hoc routing (LANMAR) to a hierarchical structure with backbone nodes, high quality backbone links and UAVs. We show that the basic LANMAR scheme can be extended to incorporate backbone and UAV links. We will also show how backbone links and UAV links are automatically discovered by the LANMAR routing algorithm and are used effectively to reach remote destinations (thus reducing the hop distance). In other words, our scheme will combine the benefits of flat LANMAR routing and physical network hierarchy, without suffering of the intrinsic EHSR limitations.

An exact end-to-end blocking probability algorithm for multicast networks

Analysis of adaptive cost functions for dynamic update policies for QoS routing in hierarchical networks

We consider the problem of estimating steady-state blocking probability for circuit-switched networks that allow alternate routing with particular emphasis on networks protected by trunk reservation. We use a recently proposed blocking probability estimate, the Overflow Priority Classification Approximation (OPCA) as an alternative to the currently used Erlang's Fixed-Point Approximation (EFPA). We demonstrate empirically that OPCA provides a better blocking estimate than EFPA for circuit-switched networks with alternate routing, that are reasonably protected by trunk reservation.

As a key component in dynamic wavelength-routing optical networks (WRONs), the contention performance at add/drop (A/D) ports of ROADMs has attracted a lot of attention in recent years. For the first time, this paper derives the close-form solutions of the blocking probability (BP) of A/D requests to characterize the fundamental tradeoff between A/D flexibility and system complexity in the ROADM. We show that the ROADM with fiber cross-connect (FXC) can decide whether a request can be satisfied based on global transceiver-usage information, and thus an exact expression of BP can be obtained. In comparison, the ROADM without FXC needs detail transceiver-usage information to make decision, and thus is hard to be analyzed. To circumvent the difficulty in analysis, we describe the evolution of the number of busy transceivers using a one-dimensional Markov chain, where the state transition rates are estimated from global transceiver-usage information. Based on this model, we obtain an approximate BP the accuracy of which is high enough for currently commercialized ROADMs and increases with the number of drop ports. Our analytical results provide an interesting insight into the tradeoff between A/D flexibility and system complexity, based on which we give some suggestions for system design.

Multicast connections have a bandwidth saving nature. This means that a multicast connection --- in taking the form of a tree with streams merging at the nodes --- requires much less capacity from the network links than a bunch of separate point-to-point connections providing the same connectivity. In this paper, we consider dynamic multicast connections that can be used to model, for example, TV or radio delivery on a telecommunications network, such as an ATM network with virtual circuits. We show how to calculate the blocking probabilities of requests to join such a tree. First, we consider the blocking probabilities occurring in a single link. The resulting model is able to capture heterogeneous capacity requirements for different multicast channels. Then we extend the results to a whole network using the reduced load approximation. The accuracy of the approximation method is studied by simulations.

In this paper, we introduce two novel evolutionary processes for hierarchical networks referred to as dominance- and prestige-based evolution models, i.e., DBEM and PBEM, respectively. Our models are deterministic in nature which allows for closed-form derivation of equilibrium points for such type of networks, for the special case of complete networks. After deriving these equilibrium points, we are somewhat surprised in recovering the exponential and power-law strength distribution as the shared property of the resulting hierarchal networks. Additionally, we compute the network properties, Geodesic distance distribution and centrality closeness, for each model in closed form. Interestingly, these results demonstrate very different roles of hubs for each model, shedding the light on the evolutionary advantages of hierarchies in social networks: in short, hierarchies can lead to efficient sharing of resources and robustness to random failures. For the general case of any hierarchical network, we compare the estimations of tie intensities and node strengths using the proposed models to open-source real-world data. The prediction results are statistically compared using the Kolmogorov–Smirnov test with the original data.

In a hierarchical network, groups of nodes are represented by logical nodes for the purposes of simplifying routing. Each group has a set of ingress-egress nodes, and routing information is conveyed to the outside world in the form of a transition matrix that gives the cost of traversing the network between each ingress-egress node pair. In this paper, we present a minimal logical node representation that has sufficient descriptive power to enable path selection in support of connection admission control for services that have both path (restrictive) and link (additive) constraints. For example, the representation can be used to find a path that maximizes bandwidth subject to a delay constraint or minimizes delay subject to a bandwidth constraint. We present our solution in the form of a matrix whose elements are vectors, each of which specifies the efficient frontier of the solution space, and we specify an efficient procedure for constructing the efficient frontier. We present the least upper bound on the number of elements that must be present in the efficient frontier. We provide numerical examples that illustrate construction of the efficient frontier.

While a session request is assigned to a wavelength-routed optical WDM networks, which are circuit-switched in nature, the challenge of routing and wavelength assignment (RWA) is to calculate the optimal path between two nodes, and further is to assign an available set of wavelengths along this path. An algorithm called Total wavelengths and Expected available wavelengths (TEW) proposed by Pavarangkoon et. al. in order to achieve effective routing and wavelength assignment formulates a link weight function and considers this as the main factor for route selection. This function is calculated by using a determination factor of the number of wavelengths that are being used currently and are supposed to be available after a certain time. However, this algorithm tends to overload paths with smaller weights and higher utilization while lightly loaded paths with slightly lower capacities may remain unused. In this paper, propose an improvement to the TEW algorithm by incorporating the frequency of usage of the paths in the weight function and running Dijkstra’s shortest path algorithm to choose paths that have more total and expected available wavelengths and less frequency of usage. The proposed algorithm is called as Countered Total wavelengths and Expected available wavelengths (CTEW) algorithm. The impact of the proposed algorithm on blocking probability is investigated by means of computer simulation and by comparing it with TEW algorithm. The results show that the proposed algorithm can achieve better performance in terms of blocking probability.

Spectrum holding per cellular telephony service provider in India is significantly lower than the world average. The spectrum is also severely fragmented across bands and the fragments also have different license conditions. Regulators in India have recently recognized that such spectrum fragmentation is a source of inefficiency for the service providers and have allowed sharing of spectrum among the providers. The genesis of this paper is this regulatory order and it has a three-fold objective. We first study an example spectrum allocation. By assuming GSM-like voice telephony service, we analyse the spectrum holding in one service area in some detail. Using simple calculations, we see that complete pooling of resources by the providers may not be stable-one provider may have a lower blocking probability if it does not form a coalition. This leads us to our second objective of developing analytically tractable partial sharing models where the providers do not pool all their resources. For a probabilistic spectrum sharing model, we analyse a simple system and obtain the partial sharing that will make the coalition stable and Pareto efficient. This model is then extended to a larger system and numerical results from the analytical model are used to obtain additional insights. We then consider a deterministic sharing model for which we also present a similar analysis for this system. We also show that the deterministic sharing system can be analysed via a suitably defined circuit multiplexed network that allows us to use Kelly's Erlang fixed point approximation which in turn provides economic insights. The final objective is to develop a game theoretic model for partial sharing. We provide a Nash bargaining framework for partial sharing. We also discuss some revenue sharing mechanisms when the providers' benefits from partial sharing are asymmetric.

This paper studies the blocking performance of optical burst switching (OBS) networks using a sequential office control (SOC) state-independent deflection routing policy. We show that unprotected deflection routing may destabilize OBS resulting in higher blocking probabilities than if bursts were not deflected but simply blocked. This study was motivated by the well-known destabilizing effect that alternative routing has on circuit switching in classical telephony networks. We propose two forms of protection to guard against destabilization: 1) wavelength reservation, which is analogous to trunk reservation in circuit switching; and, 2) preemptive priority, which is a new form of protection where bursts that have not been deflected are given preemptive priority over bursts that have been deflected. Our main contribution is a one-moment reduced-load approximation to evaluate the blocking performance of OBS networks using deflection routing protected by either wavelength reservation or preemptive priority. Our reduced-load approximation relies on the usual assumptions of link independence and Poisson distributed link arrivals. We quantify the error admitted in making these two assumptions via simulation. Using our reduced-load approximation, we evaluate the blocking performance of protected and unprotected deflection routing in several randomly generated networks. The chief conclusion of our study is that deflection routing in OBS should be given some form of protection to avoid destabilization resulting from upward load variations, and in terms of blocking performance, preemptive priority is the best form of protection for OBS. We use simulation to verify that our conclusions remain valid for a realistic traffic scenario.

Hierarchical spanning tree network design with Nash genetic algorithm

Wireless sensor networks (WSNs) nodes are commonly designed to work with limited resources of memory, energy and processing. The routing protocol is one of the key components of WSNs and its features impact network performance significantly. We present an efficient Multi-Parent Hierarchical (MPH) routing protocol for wireless sensor networks; its main goal is to achieve reliable delivery of data in a single sink scenario while keeping low overhead, reduced latency and low energy consumption. The main features of MPH are self-configuration, hierarchical topology, persistence according to link quality, and source routing from sink to nodes. Network performance simulations of the MPH routing protocol are carried out and compared with two popular protocols, AODV, DSR and with the well-known algorithm ZTR (Zigbee Tree Routing). Results show that for the single sink scenario, the MPH protocol has an energy saving of 35% against AODV and DSR protocols and 8% compared with ZTR. MPH has 27% less overhead compared with AODV and DSR. And MPH presents a 10% increase in packet delivery compared with AODV, DSR and ZTR. Finally, we present a real WSN built based on the MPH protocol, which works satisfactorily, providing an experimental demonstration of the capabilities of the protocol.

Wireless sensor networks represent technology for networking of sensor devices, as well as for other devices in IoT systems. The hierarchical routing protocols have many advantages when these networks are used in monitoring applications, with the energy efficient hierarchical multi-hop routing proposed for large scale networks that assures reliable data gathering in the non-ideal connectivity conditions. We here propose a modification of our previously designed multi-hop routing concept by employing clustering algorithm from HEED protocol in order to achieve uniformly placed clusters. The conducted analysis for several multi-hop protocols showed good performance of here proposed solution for ideal and non-ideal network connectivity.