Cell planning for outdoor distributed antenna systems in dense urban areas

Provisioning of high rate mobile data services and increased network level capacities in mobile cellular systems require higher received signal levels and improved interference characteristics throughout the cell coverage area. Traditional macrocellular deployments, due to high associated path losses, are only able to provide peak bit rates to users near the base stations. Moreover, the situation is further degraded in dense urban areas due to fading and shadowing effects. Hence, operators are forced to bring the antenna installations closer to the users in order to reduce the link losses and increase the service availability. As such, two competing technologies have been identified as alternative solutions for provisioning of high speed data in the outdoor environment, (i) small cells and (ii) outdoor distributed antenna systems (ODAS). In this article we evaluate and analyze the performance of small cells and outdoor DAS based deployments in a dense urban environment. The analysis covers the performance evaluation in both outdoor and indoor settings while taking into account two key performance metrics: coverage and spectral efficiency. Furthermore, we study different deployment strategies for deploying the outdoor DAS network. Results indicate, that due to better interference management, ODAS deployments can provide improvements in outdoor cell level capacities, specifically cell edge capacity performance, as compared to stand-alone small cell deployments, however, due to comparatively lower frequency reuse factor than small cell scenario, the area capacity performance of ODAS is lower. For indoor receivers, the performance of all outdoor solutions are fairly low, mainly due to high associated building penetration loss. The findings strongly motivate the deployments towards heterogeneous network, where the indoor small cell solutions fulfill the exponentially increasing capacity demand of the indoor environment. For fulfilling the dynamic outdoor capacity demands, there is an inherent need of an advanced version of outdoor DAS solution that can dynamically configure the DAS nodes to act as a `single super micro-/DAS cell' or multiple independent small microcells, based on the outdoor traffic conditions.