Abstract:WOSInternational audienceWe derive a lower bound on the capacity of discrete-time Rician-fading channels that are selective both in time and frequency. The noncoherent setting is considered, where neither the transmitter nor the receiver knows a priori the actual channel realization. Single-input single-output communications subject to both average and peak power constraints are investigated. The lower bound assumes independent and identically distributed input data and is expressed as a difference between two… Show more
“…It must be stressed that u i should not be understood as an achievable rate for UA systems in the sense of [27], [28], but rather as an optimization criterion useful to automatically drive noncooperative UA systems toward a more efficient spectrum sharing strategy than the usual uniform power allocation strategy.…”
“…Using (28) and conditional expectations, we can write equation 30 The game could be defined with (9) as utility functions. However, the water-filling solution would not have a closed-form expression as in (15) and convergence and NE uniqueness conditions cannot be found easily.…”
Section: A Minimization Against the Worst Case Cross-channels Distrimentioning
International audienceThis paper focuses on underwater acoustic (UA) communications and proposes a decentralized spectrum sharing method for noncooperative orthogonal frequency-division multiplexing systems in interference channels. The problem is formulated as a noncooperative game where the players are UA communication systems aiming at finding the power allocation on subcarriers that maximizes a utility function related to their information rate. Realistic assumptions regarding the UA context are formulated. Frequency-selective and randomly time-varying channels are considered. Each system is constrained in average power and adapts its power allocation strategy only with local knowledge of its channel statistics and noise plus interference power spectral density. This knowledge is obtained through a feedback link from the receiver. Estimation errors on the channel statistics are taken into account, thanks to a robust reformulation of the game. We show that an efficient decentralized spectrum sharing can be achieved when all players use a water-filling strategy against each other iteratively. Simulations results are obtained on synthetic but realistic channels. In configurations where the UA communication systems are in close areas, significant increases of spectral efficiencies can be expected compared to the conventional uniform power allocation. Results on channels sounded at sea support our conclusions
“…It must be stressed that u i should not be understood as an achievable rate for UA systems in the sense of [27], [28], but rather as an optimization criterion useful to automatically drive noncooperative UA systems toward a more efficient spectrum sharing strategy than the usual uniform power allocation strategy.…”
“…Using (28) and conditional expectations, we can write equation 30 The game could be defined with (9) as utility functions. However, the water-filling solution would not have a closed-form expression as in (15) and convergence and NE uniqueness conditions cannot be found easily.…”
Section: A Minimization Against the Worst Case Cross-channels Distrimentioning
International audienceThis paper focuses on underwater acoustic (UA) communications and proposes a decentralized spectrum sharing method for noncooperative orthogonal frequency-division multiplexing systems in interference channels. The problem is formulated as a noncooperative game where the players are UA communication systems aiming at finding the power allocation on subcarriers that maximizes a utility function related to their information rate. Realistic assumptions regarding the UA context are formulated. Frequency-selective and randomly time-varying channels are considered. Each system is constrained in average power and adapts its power allocation strategy only with local knowledge of its channel statistics and noise plus interference power spectral density. This knowledge is obtained through a feedback link from the receiver. Estimation errors on the channel statistics are taken into account, thanks to a robust reformulation of the game. We show that an efficient decentralized spectrum sharing can be achieved when all players use a water-filling strategy against each other iteratively. Simulations results are obtained on synthetic but realistic channels. In configurations where the UA communication systems are in close areas, significant increases of spectral efficiencies can be expected compared to the conventional uniform power allocation. Results on channels sounded at sea support our conclusions
“…Note that u i should not be understood as an achievable rate in the sense of [7] but rather as an optimization criterion allowing UA systems to find efficient power allocation strategies in a noncooperative way and with minimal knowledge about their environment. In the following, u i will thus be called "information rate" with a slight abuse of language.…”
Section: System Model and Problem Formulationmentioning
Abstract-This paper aims at studying underwater acoustic OFDM communication systems interfering with each others in the same channel. We propose a decentralized spectrum sharing method that minimizes the total power consumed while satisfying a constraint related to their information rate. The considered systems are supposed noncooperative, i.e. unable to communicate with each others so that they cannot agree on a fair resource sharing scheme. The problem is formulated within the framework of game theory and solved according to the Nash Equilibrium concept. Several results are presented and show that interfering UA systems can share the spectrum in a more efficient way, both in terms of energy consumption and information rate.
“…From a single measurement, it is thus possible to compare competing transmission schemes when faced to the same realistic environment [3]. Thanks to Monte-Carlo simulations, design and validation metrics such as bit error rate [1]- [3], capacity bounds [4]- [6] or fading statistics [2] can be computed with a good accuracy. Note however that the methodology behind stochastic replay does not apply to every UAC channel.…”
This paper lays the foundation of an underwater acoustic channel simulation methodology that is halfway between parametric modeling and stochastic replay of at-sea measurements of channel impulse responses. The motivation behind this approach is to extend the scope of use of replay-based methods by allowing some parameterization of the channel properties while complying with some level of realism. Based on a relative entropy minimization between the original channel impulse response and the simulated one, the idea is to deliberately distort the original channel statistics in order to meet some specified constraints.
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