Sharif Digital Repository

A novel, robust and practical method for active user enumeration in asynchronous CDMA in multipath channel condition is proposed in this paper. Most of the previous works do not consider the fact that in practical case, user's signals with the help of receiver arrive asynchronously. The proposed method can be used practically in blind multi-user detection such as eavesdropping; moreover, the method is based on information theory criteria which outperform other methods. Minimum description length (MDL) has better performance than all other information criteria used in such scenarios. Unlike most of the pervious works, we do not exploit array antenna to gather necessary data of the users.... 

In this paper, we evaluate the capacity of Multiple-Input Multiple-Output (MIMO) systems using directional antennas in non-isotropic scattering environments. Our analytical analysis approach results in closed-form approximate formulas in low Signal to Noise Ratio (SNR) regime (in contrast to previous research works which have investigated the same problem by employing experimental or simulation frameworks). We propose an upper bound for the introduced approximate error. Our results show that MIMO systems equipped with directional antennas may have much higher capacity in nonisotropic scattering environments compared to MIMO systems equipped with omni-directional antennas. We also evaluate...