International audienceDecentralized multiple access channels where each transmitter wants to selfishly maximize his transmission energy-efficiency are considered. Transmitters are assumed to choose freely their power control policy and interact (through multiuser interference) several times. It is shown that the corresponding conflict of interest can have a predictable outcome, namely a finitely or discounted repeated game equilibrium. Remarkably, it is shown that this equilibrium is Pareto-efficient under reasonable sufficient conditions and the corresponding decentralized power control policies can be implemented under realistic information assumptions: only individual channel state information and a public signal are required to implement the equilibrium strategies. Explicit equilibrium conditions are derived in terms of minimum number of game stages or maximum discount factor. Both analytical and simulation results are provided to compare the performance of the proposed power control policies with those already existing and exploiting the same information assumptions namely, those derived for the one-shot and Stackelberg games

We consider a Bayesian persuasion problem where the persuader and the decision maker communicate through an imperfect channel that has a fixed and limited number of messages and is subject to exogenous noise. We provide an upper bound on the payoffs the persuader can secure by communicating through the channel. We also show that the bound is tight, i.e., if the persuasion problem consists of a large number of independent copies of the same base problem, then the persuader can achieve this bound arbitrarily closely by using strategies that tie all the problems together. We characterize this optimal payoff as a function of the information-theoretic capacity of the communication channel. for stimulating discussions and comments. We thank the editor Alessandro Pavan, an anonymous associate editor and anonymous referees for helpful comments and suggestions. We also thank participants of the 6th workshop on /site/tristantomala2. Tristan Tomala gratefully acknowledges the support the HEC foundation and ANR/Investissements d'Avenir under grant ANR-11-IDEX-0003/Labex Ecodec/ANR-11-LABX-0047. 1 See e.g., Perez and Skreta, 2018. 2 See Boleslavsky and Cotton, 2015 for a model of grading standards through Bayesian persuasion.3 of good or bad quality. When a project is approved, it yields a positive return of +1 to the investors if it is good, and a negative return of −7 if it is bad; rejecting a project yields a payoff of 0. The objective of the firm is to get a maximum number of projects approved.Suppose that the firm commits to an information disclosure mechanism, i.e., distributions of messages conditional on states (as in Kamenica and Gentzkow, 2011) and faces no restriction on the number of messages. To invest, the board of investors must be persuaded that the project is good with probability at least 7/8. Thus, for each project, the firm would optimally draw a good message g or a bad message b with the following probabilities:This way, the belief that the project is good upon receiving the good message is as follows: P(project is good | g) = 7/8, and the project is accepted with probability 4/7 (see Section 4). Now, suppose that the auditing board gives the firm only half the time it would require to talk about all projects. Namely, there is an even number n of projects, but the firm has only n/2 messages available.A simple strategy the firm can adopt would be to select half of the projects, focus on them, and communicate optimally for each of them. With this strategy, half of the projects are accepted with probability 4/7 each, so in expectation, the average number of accepted projects is 2/7. This is not optimal, and a better strategy would be to pair projects by two and to draw one message g, b for each pair in the following way: P(g | both projects are good) = 1, P(g | both projects are bad) = 0, P(g | only one project is good) = 1/6.The total probability of g is 1/3 and upon observing this message, the beliefs about quality are as follows:P(both projects are good | g) = 6/8, P(only project 1 is good | g) = P(only p...

In this work, we investigate a coding strategy devised to increase the throughput in hybrid ARQ (HARQ) transmission over block fading channel. In our approach, the transmitter jointly encodes a variable number of bits for each round of HARQ. The parameters (rates) of this joint coding can vary and may be based on the negative acknowledgment (NACK) provided by the receiver or, on the past (outdated) information about the channel states. These new degrees of freedom allow us to improve the match between the codebook and the channel states experienced by the receiver. The results indicate that significant gains can be obtained using the proposed coding strategy, particularly notable when the conventional HARQ fails to offer throughput improvement even if the number of transmission rounds is increased. The new cross-packet HARQ is also implemented using turbo codes where we show that the theoretically predicted throughput gains materialize in practice, and we discuss the implementation challenges.