Sharing of Unlicensed Spectrum by Strategic Operators

Facing the challenge of meeting ever-increasing demand for wireless data, the industry is striving to exploit large swaths of spectrum which anyone can use for free without having to obtain a license. Major standards bodies are currently considering a proposal to retool and deploy Long Term Evolution (LTE) technologies in unlicensed bands below 6 GHz. This paper studies the fundamental questions of whether and how the unlicensed spectrum can be shared by intrinsically strategic operators without suffering from the tragedy of the commons. A class of general utility functions is considered. The spectrum sharing problem is formulated as a repeated game over a sequence of time slots. It is first shown that a simple static sharing scheme allows a given set of operators to reach a subgame perfect Nash equilibrium for mutually beneficial sharing. The question of how many operators will choose to enter the market is also addressed by studying an entry game. A sharing scheme which allows dynamic spectrum borrowing and lending between operators is then proposed to address time-varying traffic and proved to achieve perfect Bayesian equilibrium. Numerical results show that the proposed dynamic sharing scheme outperforms static sharing, which in turn achieves much higher revenue than uncoordinated full-spectrum sharing. Implications of the results to the standardization and deployment of LTE in unlicensed bands (LTE-U) are also discussed.Comment: To appear in the IEEE Journal on Selected Areas in Communications, Special Issue on Game Theory for Network

THE ROBUSTNESS OF EQUILIBRIUM ANALYSIS: THE CASE OF UNDOMINATED NASH EQUILIBRIUM

I consider a strategic game form with a finite set of payoff states and employ undominated Nash equilibrium (UNE) as a solution concept under complete information. I propose notions of the proximity of information according to which the continuity of UNE concept is considered as the robustness criterion. I identify a topology (induced by what I call d?) with respect to which the undominated Bayesian Nash equilibrium (UBNE) correspondence associated with any game form is upper hemi-continuous at any complete information prior. I also identify a slightly coarser topology (induced by what I call d??) with respect to which the UBNE correspondence associated with some game form exhibits a failure of the upper hemi-continuity at any complete information prior. In this sense, the topology induced by d? is the coarsest one. The topology induced by d?? is also used in both Kajii and Morris (1998) and Monderer and Samet (1989, 1996) with some additional restriction. I apply this robustness analysis to the UNE implementation. Appealing to Palfrey and Srivastava’s (1991) canonical game form, I show, as a corollary, that almost any social choice function is robustly UNE implementable relative to d?. I show, on the other hand, that only monotonic social choice functions can be robustly UNE implementable relative to d??. This clarifies when Chung and Ely’s Theorem 1 2003) applies.

Partial Certifiability and Information Precision in a Cournot Game

This paper examines strategic information revelation in a Cournot duopoly with incomplete information about firm~1\'s cost and information precision. Firm~2 relies on certifiable and ex post submissions of firm~1, without necessarily knowing whether firm~1 knows its cost or not. The sequential equilibria of the induced communication game are determined for different certifiability possibilities. A perfectly cevealing equilibrium in which information precision is irrelevant is obtained under full certifiability. On the contrary, it is shown that if only payoff-relevant (fundamental) events can be certified, then the equilibrium output and profit of firm~1 decreases with its average information precision if this firm is uninformed or if its cost is high. A consequence of this local effect is that information precision has, on average, no value for a firm.Strategic information revelation; Information precision; Cournot competition; Cost uncertainty; Higher order uncertainty.

Experts Playing the Traveler's Dilemma

We analyze a one-shot experiment on the traveler's dilemma in which members of the Game Theory Society, were asked to submit both a (possibly mixed) strategy and their belief concerning the average strategy of their opponents. Very few entrants expect and play the unique Nash equilibrium, while we observe a fifth playing the cooperative solution of the game, i.e. a strictly dominated strategy. The experimental data suggest to analyze the game as one of incomplete information. Most strategies observed are in the support of its Bayesian Nash equilibria. A notable exception is the Nash equilibrium strategy of the original game.Traveler's Dilemma; Experiment; Experts; Incomplete Information