Design and experimental evaluation of a low-complexity spatial combiner for LTE distributed antenna systems

This article presents a distributed antenna system (DAS) architecture for small-cell base stations (BTSs), whereby cooperation between the DAS infrastructure and the BTS allows for an increase in performance compared to conventional systems, while at the same time keeping complexity and cost at low levels. Specifically, the article investigates the improvements in uplink physical layer performance achieved by adding an initial antenna combining step in the DAS system before conventional combining and equalization at the BTS. This initial step can be implemented in a very low-complexity fashion by performing all operations in the time domain and using channel state information calculated at the BTS itself. The article presents this technique in the context of an LTE DAS system. Results from both a software simulator and a custom-made hardware prototype are presented, establishing the feasibility of the proposed architecture.