Jose R. Vidal

Dynamic spectrum sharing in cognitive radio networks using truthful mechanisms and virtual currency

Abstract In cognitive radio networks, there are scenarios where secondary users (SUs) utilize opportunistically the spectrum originally allocated to primary users (PUs). The spectrum resources available to SUs fluctuates over time due to PUs activity, SUs mobility and competition between SUs. In order to utilize these resources efficiently spectrum sharing techniques need to be implemented. In this paper we present an approach based on game-theoretical mechanism design for dynamic spectrum sharing. Each time a channel is not been used by any PU, it is allocated to SUs by a central spectrum manager based on the valuations of the channel reported by all SUs willing to use it. When an SU detects a free channel, it estimates its capacity according to local information and sends the valuation of it to the spectrum manager. The manager calculates a conflict-free allocation by implementing a truthful mechanism. The SUs have to pay for the allocation an amount which depends on the set of valuations. The objective is not to trade with the spectrum, but to share it according to certain criteria. For this, a virtual currency is defined and therefore monetary payments are not necessary. The spectrum manager records the credit of each SU and redistributes the payments to them after each spectrum allocation. The mechanism restricts the chances of each SU to be granted the channel depending on its credit availability. This credit restriction provides an incentive to SUs to behave as benefit maximizers. If the mechanism is truthful, their best strategy is to communicate the true valuation of the channel to the manager, what makes possible to implement the desired spectrum sharing criteria. We propose and evaluate an implementation of this idea by using two simple mechanisms which are proved to be truthful, and that are tractable and approximately efficient. We show the flexibility of these approach by illustrating how these mechanisms can be modified to achieve different sharing objectives which are trade-offs between efficiency and fairness. We also investigate how the credit restriction and redistribution affects the truthfulness of these mechanisms.

Maximum-Profit Two-Sided Pricing in Service Platforms Based on Wireless Sensor Networks

A business model for Internet-of-Things-based services is proposed whereby a platform serves as an intermediary between human users and wireless sensor networks (WSNs). The platform, acting as a monopolist, posts both the price paid by each user and the price paid to each WSN so as to maximize its profits. In this setting, we propose, analyze, and compare two alternative payment schemes for the WSN side. We demonstrate that the two payment schemes are equivalent from every stakeholders point of view. And then we show that there is a user cost ceiling, which depends both on the number of WSNs and the strength of the cross externality that the WSNs creates on the users, below which the take-up is maximum.

Entry, competition and regulation in cognitive radio scenarios: a simple game theory model

Spectrum management based on private commons is argued to be a realistic scenario for cognitive radio deployment within the current mobile market structure. A scenario is proposed where a secondary entrant operator leases spectrum from a primary incumbent operator. The secondary operator innovates incorporating cognitive radio technology, and it competes in quality of service and price against the primary operator in order to provide service to users. We aim to assess which benefit users get from the entry of secondary operators in the market. A game theory-based model for analyzing both the competition between operators and the subscription decision by users is proposed. We conclude that an entrant operator adopting an innovative technology is better off entering the market, and that a regulatory authority should intervene first allowing the entrant operator to enter the market and then setting a maximum amount of spectrum leased. This regulatory intervention is justified in terms of users utility and social welfare.

Approximate Analysis of Cognitive Radio Systems Using Time-Scale Separation and its Accuracy

We model a cognitive radio system as a quasi-birth-death (QBD) process and determine its performance parameters. We also model the system at the quasi-stationary limiting regime. We show that this regime defines the asymptotic system behavior. The performance parameters of interest at this regime are independent of the service time distributions and can be determined by simple recursions. We propose and evaluate a new methodology to determine when the quasi-stationary approximation can be considered a good approximation of the actual system behavior. It requires low computational cost and does not require to solve the exact system.

Femtocell Operator Entry Decision with Spectrum Bargaining and Service Competition

This paper analyzes the effect of the entry of a femtocell operator into a mobile communications market where a macrocell operator exists. The analysis is conducted using a game-theory-based model, specifically a three-level multi leader-follower game, where different solution concepts are applied: Shapley value, Nash equilibrium and Wardrop equilibrium. It aims to answer the question of which benefit mobile communication users get from the entry of a femtocell operator into the market. The equilibrium is assessed from the point of view of each agent (e.g. profits and utilities), and of the whole (e.g. social welfare). A case for regulatory intervention is made.

Competition in cognitive radio networks: Spectrum leasing and innovation

The paper deals specifically with spectrum leasing within cognitive radio networks and it covers the economic issues that arise when primary users lease spectrum to secondary users. It aims at assessing which benefit mobile users get from the entry of secondary operators in the market. A game theory-based model is built for the case of an incumbent primary operator and an entrant secondary operator.

Analysis of price competition under peering and transit agreements in Internet Service provision to peer-to-peer users

Many studies on Internet Service Provider (ISP) interconnection make simplifying assumptions on the implementation of the service provision. Our work explicitly models the ISP service that is provided to users that run peer-to-peer applications and it analyses the behavior of competing ISPs. The ISPs have agreed to peer each other and each ISP has purchased transit service from one Internet Backbone Provider. The quality of service, the equilibrium prices and the market shares that the competition game yields are computed by means of our model. Our work assesses the strategy of an ISP which provisions its transit link against a competing ISP in terms of competitive advantage and social welfare. And it assesses the effect of the entrance of more competing ISPs.

Price competition between a macrocell and a small-cell service provider with limited resources and optimal bandwidth user subscription: a game-theoretical model

The ever-increasing demand for higher data rates in wireless commutations provides a rationale for small cells deployment. While the physical and technological aspects of small-cell networks have been extensively studied in recent years, the economic analysis has received much less attention. We focus on the economic rationale for a small-cell service provider (SSP) operating a market where an incumbent macrocell service provider (MSP) exists, and competition develops. We analyze such scenario for the case of fixed users by means of Game Theory, specifically through a two-stage game: in the first stage each service provider posts its price according to a Stackelberg game where the MSP is the leader and the SSP is the follower; and, in the second stage, each user chooses both which provider to subscribe to and the optimal amount of bandwidth. A subgame perfect Nash equilibrium is used as a solution concept, and it is derived analytically. We show that the SSP has an incentive to operate in the market and its profit gets higher as SSP’s resources increase. Furthermore, users benefit from SSP’s operation, which may provide a rationale for a regulatory authority to grant the SSP access to the market, despite the fact that MSP’s profit is harmed. Finally, we identify two modes of operation of the system, which depend on the SSP coverage: one where SSP’s deployment is limited and the MSP strategy is not affected by SSP competition and takes only the users outside the SSP coverage; and another, where the SSP covers a large area and the MSP competes against the SSP taking a fraction of the users inside the small cells.

Pricing of Wireless Sensor Data on a centralized bundling platform

A marketplace for the sale of sensor data is analysed, where the data collected by a set of Wireless Sensor Networks (WSN) are made available as a bundle to end customers through an intermediary bundling platform. The platform collects a flat fee from end customers and pays WSNs a price growing linearly with the sensing rate. The bundling platform sets both prices, while the other stakeholders act as price takers. A solution maximizing the platforms profit is shown to exist, and a closed form is provided for the pricing strategy to be adopted by the bundling platform. The fee paid by end customers grows linearly with the number of WSNs and the maximum sensing rate, while the price paid to WSNs grows as the two-thirds power of the fee paid to the network provider.

A Low Complexity Congestion Control Algorithm for the ABR Class of Service

A new generation of systems called Networked Multimedia Systems are currently being the subject of intense study. These systems require a high throughput and QoS guarantees. The Broadband Integrated Service Digital Network (B-ISDN) based on the Asynchronous Transfer Mode (ATM) provides these requirements in an efficient manner. A new ATM service category, the Available Bit Rate (ABR) service, will systematically and dynamically allocate available bandwidth to users by controlling the flow of traffic with a closed-loop feedback mechanism. The ABR service was initially design to support data traffic but recently there has been much interest in using ABR to support voice and video applications [9]. In this scenario, the voice and video connections, which may require small delays, and the bursty data connections are multiplexed on different queues at the switches. An admission control policy over the real-time connections is usually required to guarantee that the end to end delay is kept below a target. With explicit rate feedback the sources can adapt faster to the new network conditions achieving in this way less queueing delays and cell-loss rates.