A low overhead synchronization mechanism for beamformed systems

Small cells deployments, at carrier frequencies much higher than the current cellular deployments, featuring electronically steerable transmit and receive antenna arrays offering high-gain beam-forming, are likely to form the basis of next generation cellular networks (sometimes referred to as 5G). This shift to smaller cells and high-gain directional transmit/receive technologies will be accompanied with challenges of handling increased number of cell edges and “more fragile” communication links, compared to the traditional macro cell operation in the cellular bands with omni-directional receivers. Cloud Cell - a system framework for virtually eliminating the edges and handling fragility, by ensuring that the Mobile Station (MS) always has multiple “good” links to choose from, was introduced in an earlier work. A fundamental challenge in enabling Cloud Cell, or another system where an MS is served by multiple base stations (BSs), is to come up with schemes where the synchronization overhead can be kept to a minimum without incurring excessive losses in performance. In this paper, we propose and evaluate a low-pilot overhead scheme for uplink synchronization in a Cloud Cell based beam-formed system, suitable for use in mm-Wave bands.