Maurizio Naldi

Cloud storage pricing: a comparison of current practices

Cloud storage is fast securing its role as a major repository for both consumers and business customers. Many companies now offer storage solutions, sometimes for free for limited volumes. The most apparent means of competition is pricing, though the complexity of pricing plans may make a comparison difficult. We have surveyed the pricing plans of a selection of major cloud providers and compared them using the unit price as the means of comparison. We find that all the providers, excepting Amazon, adopt a bundling pricing scheme; Amazon follows instead a block-declining pricing policy. Our comparison of pricing plans is conducted through a double approach: a pointwise comparison for each value of storage volume, and an overall comparison using a two-part tariff approximation and a Pareto-dominance criterion. Under both approaches, most providers appear to offer pricing plans that are more expensive and can be excluded from a procurement selection in favour of a limited number of dominant providers.

Long-range Evaluation of Risk in the Migration to Cloud Storage

The economical evaluation of the benefits of cloud migration versus the decision to buy and manage the storage facilities in house is essential for the migration decision. Deterministic models have been proposed in the past, which fail to account for the essentially random nature of any future quantity involved in the decision. The random nature of future events also implies the insurgence of risks when the decision taken turns out to be wrong. Here we adopt a probabilistic model and employ it to assess the risk associated to either decision over an extended time period. We adopt the Value-at-Risk as a risk metric, and compare two decision variables, namely the mean and the median Differential Net Present Value. We show that though the two decision variables bear the same risk for most values of the range of leasing prices, the mean Differential Net Present Value abates the Value-at-Risk even by as much as 60% in the small region of leasing prices where there is large uncertainty between the two alternatives.

Storage Buy-or-Lease decisions in cloud computing under price uncertainty

Cloud computing allows to lease computational resources on demand on the network instead of buying them. Storage is a major computational resource that may be leased under the cloud computing approach. An economical model is provided for the analysis of the Buy-or-Lease decision for storage in cloud computing. The model introduces a probabilistic approach to evaluate future prices and the replacement needs for disk arrays (in contrast to the current literature which considers deterministic prices and fixed replacement rates). The median Differential Net Present Value is proposed as the decision variable. A simulation analysis is conducted that shows that the cloud computing approach appears more profitable for medium-sized companies with longer investment plans. The risks associated to wrong decisions is evaluated through the Value-at-Risk tool.

A real options model for the transferability value of telecommunications licenses

Licenses for telecommunications services are awarded with a number of side obligations and commitments for the licensee. Under such obligations the licensee is typically not allowed to transfer its license to another operator. Such prohibition may cause heavy inconveniences for customers, so that its removal is strongly advocated and already a reality in many cases. Its removal adds value to the original license and may then constitute a valuable option (the transferability option). A method is here proposed to assess such value, by using the framework of real options. The method is applied in a variety of settings and shows that the value of the option depends superlinearly on the reselling price and the market volatility, and linearly or sub-linearly on the expiry time of the option.

Spectrum reservation options for Mobile Virtual Network Operators

Mobile Virtual Network Operators (MVNO) operate without owning spectrum usage rights, by leasing spectrum from Mobile Network Operators owning a license. Spectrum leasing may occur through a reservation process that assigns the MVNO the right, but not the obligation, to lease spectrum at a later time. Reservation contracts may be signed with strict guarantees, that provide MVNOs with the certainty of obtaining the needed spectrum, or soft guarantees, which allow the MNO to adopt an overbooking policy and refusing to lease the spectrum, compensating the refused MVNO through the payment of a penalty. In this paper the two kinds of reservation contracts are compared from the viewpoint of the MVNO, by considering the profitability of the two alternatives. The cash flows associated to the two kinds of reservation contracts are determined and employed to compare the alternatives. The probability of overbooking and the expiry time of reservations appear as the major decision factors, while the penalty value has a negligible influence. It is shown that the reservation contract with soft guarantees is to be prefereed for larger values of the expiry time and for the lower values of the overbooking probability.

Pricing of reservations for time-limited spectrum leases under overbooking

With spectrum trading the owners of usage rights on wireless spectrum may transfer them temporarily to other users. A secondary market for spectrum may be implemented through the use of reservation mechanisms, by which prospective consumers of spectrum portions may first book them and decide later whether to actually buy the usage rights. A possible strategy for the owners of usage rights is to practise overbooking, i.e., to allow for more reservations than what they could sell (and then pay a penalty if they cannot satisfy the requests). A relevant problem for the owners of usage rights is to set the price for reservations. An algorithm is proposed here to price reservations in the presence of overbooking. The algorithm is based on the iterative use of the Cox-Ross-Rubinstein approach to price financial call options. The algorithm is then applied to a number of cases and the dependence of the price on the overbooking probability and the penalty is analysed.

Quality Management in the Design of TLC Call Centers

Call centres rely heavily on the self-service paradigm through the use of an automated IVR (Interactive Voice Response) system. The service time delivered by the IVR is a major component of the overall QoS (Quality of Service) delivered by the call centre. We analyse the structure and service times of IVR systems through a case study of five call centres in the telecommunications sector. The service trees of the call centres under survey are reconstructed by complete exploration and analysed through a set of metrics. The present design of service trees leads to service times typically larger than those spent waiting for a human agent and to excessively long announcements, with a negative impact on the overall QoS. Imbalances in the popularity of the services offered by the IVR can be exploited to reduce remarkably the average service time, by properly matching the most popular services with the shortest service times.

A short-range, high-resolution millimeter-wave surface movement radar

Today’s Air (and Airport traffic) management needs an advanced surveillance function for the airport’s surface. Among the different sensors to be integrated for this function just the surface movement radar is able to detect the presence, and determine the position, of non co-operating targets. Present-day smr’s are considered aged and inadequate. In this paper we propose a novel short range radar, operating at frequencies around 95 GHz, to be used in a distributed surface surveillance system. Its main characteristics and the trade-off considerations involved in its design are discussed.RésuméLe contrôle des pistes d’un aéroport a un rôle de plus en plus important dans la gestion du trafic aérien. Le radar pour les mouvements au sol (surface movement radar, smr) est le seul capteur capable de détecter la presénce et de déterminer la position d’une cible non coopérative, mats les radars installés actuellement sont anciens et ne peuvent répondre aux exigences actuelles. Cet article présente un nouveau radar fonctionnant vers 95 GHz, intégré dans un système distribué de surveillance. Il discute ses caractéristiques et les compromis intervenus pendant sa conception.

Simulation of Aircraft Images for Airport Surface Traffic Control

An Air Surface Traffic Control (ASTC) system needs an advanced and integrated surveillance function based on radar sensors for non-cooperative targets. A new generation of Surface Movement Radars is currently being developed that requires the use of tools like radar-image simulators, able to test the performances of such radars. A high resolution radar-image simulator that meets the ASTC requirements is described in this paper.