Reliable p‐Hub Location Problems in Telecommunication Networks

This article deals with a Hub Location Problem arising in Telecommunication Network Design. The considered network presents two different kinds of nodes: access nodes, that represent source and destination of traffic demands but cannot be directly connected, and transit nodes, that have no own traffic demand but collect traffic from access nodes and route it through the network. Transit nodes are supposed to be fully connected. Given a set of access nodes and a set of potential locations for the transit nodes, the problem is to decide number and positions of the transit nodes to guarantee that all access nodes are allocated to a transit node, satisfying capacity constraints. The goal is to minimize the total cost of the network, which is the sum of connection costs and nodes fixed costs. The problem is a Hub Location Problem, which is known to be NP‐hard. A local search approach is proposed, and different metaheuristic algorithms, such as tabu search, iterated local search and random multistart, have been developed, based on such local search. [A preliminary procedure has been developed in a research project joint with Telecom Italia (Turin Research & Innovation Laboratories) and a patent application has been filed to cover this issue.] © 2004 Wiley Periodicals, Inc. NETWOEKS, Vol. 44(2), 94–105 2004

Hub covering location problems with different coverage types

Telecommunications networks are facing increasing demand for Internet services. Therefore, the problem of telecommunications network design with the objective to maximize service data flows and provide fair treatment of all services is very up-to-date. In this application, the so-called maxmin fair (MMF) solution concept is widely used to formulate the resource allocation scheme. It assumes that the worst service performance is maximized and the solution is additionally regularized with the lexicographic maximization of the second worst performance, the third one, etc. In this paper we discuss solution algorithms for MMF problems related to telecommunications network design. Due to lexicographic maximization of ordered quantities, theMMF solution concept cannot be tackled by the standard optimization model (mathematical programme). However, one can formulate a sequential lexicographic optimization procedure. The basic procedure is applicable only for convex models, thus it allows to deal with basic design problems but fails if practical discrete restrictions commonly arriving in telecommunications network design are to be taken into account. Then, however, alternative sequential approaches allowing to solve non-convex MMF problems can be used.

Reliability metrics and modeling techniques have been successfully used to analyze the reliability of a system, which typically consists of hardware platforms and software running on top of the hardware platforms. In telecommunications applications, system level reliability evaluation and improvement activities are better-understood. However, measurements for assessing reliability of complex networks still need to be better defined and understood. This becomes particularly essential as evolving telecommunications networks are getting more complicated with diversified technologies, multimedia services and evolving infrastructure. Besides the traditional voice application, today's telecommunication networks support multimedia applications that blend text, voice and video services. These solutions deal with different access technologies (e.g., wireless and wireline) and often use network elements from different vendors. Moreover, different applications (e.g., games, gambling, bank transactions, etc.) can have very different reliability requirements and characteristics. This paper discusses reliability considerations in estimating and analyzing the end-to-end reliability of complicated telecommunications network solutions.

In hub location problem the overall network performance is extremely depends on the operation of network elements such as hubs and arcs. Happening disorder in one elements of network (hubs or arcs), may lead to network breakdown or poor service levels. This study presents multi-objective single allocation hub covering location which is by exploring the tradeoff between the total cost and total number of intermediate links between all origins and destinations, offers a scenario ideal from the investor point of view and so convenient from the customer point of view. This study also gives this assurance that the minimum reliability of all routes that formed by hubs and arcs does not less than a specified value (controls the network minimum reliability). The type of coverage that rarely studied in the literature and does not have other type’s deficiency is used. Moreover, this paper presents a non-dominated sorting genetic algorithm-II, which its parameters are tuned by response surface methodology, to find near optimal pareto solutions for the given problem. The reliability of the proposed algorithm, based on three evaluation metrics (number of pareto solutions, spacing metric, diversity metric) is determined. Computational results of Turkish dataset are presented for better illustration of the proposed model.

Hub location problem is one of the most important problems in the areas of logistics and telecommunication network design. In this paper, we address the single allocation maximal covering hub location problem in which the objective is to maximise the amount of covered flows associated with origin-destination pairs in a hub-and-spoke network using a fixed number of hub facilities. Two mathematical programming formulations are developed for the problem and since the problem belongs to the class of NP-hard problems, an efficient simulated annealing (SA)-based heuristic is proposed to solve it. Computational results indicate the efficiency of the proposed heuristic both in terms of solution quality and CPU time.

The design and analysis of cost effective survivable telecommunication networks is a very important problem. We study techniques for visualizing survivable telecommunication networks. The visualization of telecommunication networks is very useful in aiding the design process of minimum cost networks and the management of network operations. We present several linear time algorithms for drawing telecommunication networks (with optimal area) so that important properties are displayed. Given a ring cover of a network, our algorithms display it in such a way that rings are easily identifiable and possible problems can be spotted by network designers.

This paper proposes parallel asynchronous versions of promising multi-objective evolutionary algorithms, implemented over a network of personal computers, with the aim of designing an optimal telecommunication network in the presence of multiple conflicting objectives as cost and performance. The resulting tool provides a set of Pareto optimal solutions, facilitating the decision making process of designing a telecommunication network with a mix of different technologies.

Traditionally, performance of telecommunications networks has been undertaken on a Network Element (NE) basis, often in an uncoordinated manner and requiring sophisticated human expertise for relatively trivial tasks. However, as networks become increasingly diverse and complex, and the demands upon them increase, this approach is more and more inefficient. Additionally, the advent of distributed processing networks, such as mobile cellular, IN (Intelligent Networks) and TINA (Telecommunication Information Networking Architecture), means that local performance will no longer be sufficient and co-ordination of these activities across the network is now required. The problems with centralised performance of networks are the volume of data, the complexity of the network, and the resultant latencies in response times to network problems, A real time performance system for telecommunications networks is described, which can form the basis of real time decentralised control of future telecommunications networks. The proposed performance measurement system provides open interfaces for subscription to real time performance information at varying degrees of abstraction, corresponding to the required view. The measurement system takes an event-based approach to delivering firm real time performance information. The measurement enables real time and near real time control systems to be decentralised within the network, both at a local level and at a regional level. A hierarchical approach both reduces the volume and complexity of performance information and facilitates the development of a management by delegation paradigm in the network.

Background. The Erlang B-formula that establishes a relationship between probability of dropped calls, call intensity in a certain link and available communication channels in this link is widely used in telecommunication networks’ design and calculations. In a great number of applications, a problem emerges of finding required number of channels in a link for set call intensity to satisfy required probability of dropped calls. Methods. Methods of computer simulation as well as complex systems analysis. Results. With account of the fact that the number of channels enters Erlang B-formula, firstly, as upper index of summation, secondly, exponent of the exponent function and, thirdly, in the factorial, the solution of the problem is possible graphically. This approach includes calculation of the dropped calls probability for a certain range of numbers of channels to determine the first channel’ number for which dropped call probability results in a value below the threshold. The paper shows that for big values of the number of channels and call intensity direct use of Erlang B-formula on a computer leads to quick bit grid overflow and inability to fulfill required calculations. To overcome this problem, a recurrent algorithm is proposed to resolve the task, which is derived from Erlang B-formula and due to its structure does not suffer from the above limitations while performed on a computer. Сonclusions. Research results of the proposed algorithm demonstrate its high efficiency in implementation in Matlab environment. It is thought that the algorithm can find wide application in telecommunication networks design.

The telecommunications network has become an essential facility of our daily life, which is the reason why a good number of the recent researches are directed to it. In this paper, the performance of routing protocols for selected network and the optimum way of utilizing the network resources is proposed, through improving the routing method protocols to obtain the most accurate communication models, which give the best network performance, taking into consideration that the protocol time interval to recalculate the future routing step is agreed to be our performance criteria, which is then used to determine the total amount of incoming traffic normalized at the best network performance with respect to the network capacity as well. Moreover, adaptive routing evaluation methods have been mathematically investigated in this work for telecommunication networks (TN), more precisely, developing the infrared radiation (IR) routing methods for hybrid TN applications, in terms of implementation conditions at a certain guaranteed quality of service, where we give a particular interest in analyzing routing methods based on the fact that the distribution information is contained in the routing variables, rather than in the state variables. The protocol that deals with the unbalanced traffic distribution over TN nodes has been investigated in this paper as well, and simulation results show good progress in the proposed protocol over the traditional protocols.

One group of the optimization problems is Hub location problem. Hub facilities are used in transportation network which are provided transfer of products, information, passengers and postal package through of intermediate node instead of direct transfer. Methodology: One main group of these problems is discrete hub median location that seeks to minimize total transportation cost. Results: In this paper, we present hub median location problem with multiple allocation of non-hub nodes to hub nodes, moreover it is possible to connect non-hub nodes directly with considering a penalty coefficient. Conclusion: The numerical example for CAB25data set -which is related to flow and distance between 25 cities in America- with establishment cost under fuzzy circumstance solved and presented.

The sample average approximation (SAA) approach is a widely used technique, based on Monte‐Carlo simulation, often applied to large‐scale stochastic optimization problems. In this approach, a set of sample average problems with multiple copies of sampled scenarios are generated and solved exactly. In other words, there is an implicit assumption that the sample average problems are solvable to optimality. In some instances, however, the sample average problems might be NP‐hard problems, often difficult or impractical to solve to optimality. In this article, we broaden the scope of the SAA approach and show that even without solving the sample problems to optimality, by combining a heuristic and a lower bounding approach, high‐quality solutions with tight confidence bounds on the optimal solution value can be obtained. We demonstrate this “inexact SAA approach” on two problems. First, we apply it to the Stochastic Connected Facility Location (SConFL) problem, the motivating application for this article, that arises in the design of telecommunications networks. As an additional application, we also use it for the Stochastic Uncapacitated Facility Location (SUFL) problem. Our computational results demonstrate the effectiveness of the inexact SAA approach. © 2017 Wiley Periodicals, Inc. NETWORKS, Vol. 70(1), 19–33 2017

Mathematical modeling for a p-mobile hub location problem in a dynamic environment by a genetic algorithm

Shipment scheduling in hub location problems