UBC Theses and Dissertations
Delay-line-multiplexer-based distributed antenna channel sounders for indoor and outdoor microcellular environments Ahmed, Md. Humayun
Distributed Antenna Systems (DAS) are increasingly used to implement wireless access networks that provide high capacity, high reliability, and tailored coverage in both indoor and outdoor microcell environments. The third-generation DAS that have recently emerged are based on massively distributed antennas connected by fibre to transceiver hubs linked via a high-speed backplane. Such systems can be: 1) configured to operate in a variety of operating modes from small cells to Distributed MIMO and 2) highly customized based upon the nature of the environments and the performance demands of the users. Successful deployment of future Distributed Antenna Systems will require channel characterizations that capture our knowledge and understanding of the propagation impairments that degrade the airlink performance in a form useful in simulation and design. The principal challenge of DAS channel measurements is the need to characterize the signals presented by a multiplicity of distributed antennas in an effective and efficient manner. Most DAS channel sounders that have been reported in the literature to date are either based upon a multi-channel measurement receiver or a single-channel receiver equipped with a multi-throw RF switch. Each carries significant penalties in terms of cost and/or performance. Here, we present an alternative scheme that uses relatively inexpensive fibre-optic excess delay lines inserted into a conventional DAS distribution hub in order to effectively stack or multiplex signals in time so they can be presented in sequence by a conventional channel sounder equipped with a single-channel receiver. The concept is generally applicable, with appropriate modification, to channel sounders based upon: 1) Vector Network Analyzers that are commonly used to characterize short-range indoor environments, and 2) stepping or sliding correlators that are commonly used to characterize small cells in outdoor environments. In each case, we have derived system design formulas that allow one to determine the excess delay required to provide adequate temporal separation between the individual channel responses and system error models that allow cross-talk and other effects that may be present in the fiber distribution hub to be characterized. Finally, we have demonstrated proof-of-concept implementations of both in laboratory, real-world indoor, and outdoor small cell environments.
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