On the far-field approximation in picocell environments using a two element antenna array

Many of today´s mobile channel models use the far-field approximation quite liberally without further validation. Strictly speaking, this approximation does introduce electric phase errors to the antenna signals. We quantify the probability of their occurrence within the framework of two elliptic channel models using a two element antenna array. For typical picocell design parameters, we find that errors are acceptably small for a great majority of realisations. Providing vector channel descriptions we extend the original models used for a single antenna element to cover an antenna array. However, we notice that these extensions do not account for fading correlation between array elements. Therefore, we explicitly discourage researchers in mobile communications to use this type of extension for picocell simulation. Finally, we conclude that the far-field assumption remains a valuable argument in support of a simplified evaluation of element correlation