Achievable rates in cognitive radio channels
IEEE Transactions on Information Theory
Spectrum sharing for unlicensed bands
IEEE Journal on Selected Areas in Communications
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We consider a two-user interference channel where the users are not synchronous meaning there exists a delay between their transmitted codes. Assuming no user is aware of the location of the interference burst on its code, no interference cancellation is performed, i.e., users treat each other as noise. By the same token, the interference is no longer Gaussian as a result of the ambiguity on the start of the interference burst. We propose a stationary channel model for this setup for which we are able to derive the achievable rates based on upper and lower bounds on the mutual information between the input and output of the channel. These bounds meet each other as the code length grows to infinity. We define the outage capacity for each user as the largest transmission rate such that the outage probability is ensured to be below a certain threshold. In case the users are sharing a certain number of frequency sub-bands, we propose to divide the spectrum among the users to maximize the outage capacity for each user. We demonstrate that depending on the probabilistic parameters of the delay model and the value of the outage threshold, there are cases where the best strategy is to assign both private and common frequency sub-bands to the users.