On Optimizing Base Station
Antenna Array Topology
|Jen-Wei Liang and Arogyaswami J. Paulraj
Information Systems Laboratory
Stanford, CA 94305
Abstract Use of higher frequencies (1.8 GHz) for the U.S. upper tier PCS cellular service and the FCC regulations on network buildout have resulted in significant interest in improving coverage of cellular networks. Networks that are coverage-limited imply that thermal noise is the limiting factor. Also, since the forward link (base station to mobile) has higher power than the reverse link, coverage is limited by the reverse link. This coverage can be extended by improving the reverse link budget. Therefore, use of receive antenna arrays for boosting array gain on the reverse link is now being intensively studied.
When receive antenna arrays are used at the base station, the array design parameters affect several aspects of the system performance and cost. Some of these are: the number of antenna elements (and channels) must be minimized to reduce system cost; the maximum span of the array has to be limited for convenient deployment on a tower; the interelement spacing must be controlled to avoid grating lobes (if these are not acceptable) while the array span must be maximized to enhance diversity gain. These conflicting requirements mean that careful design of the array topology can minimize cost/performance.
In this presentation, we study performance of linear and circular base station antenna arrays with grouped vs uniform topology as a function of angle spread, number of elements used, and maximum array span. We compare alternate topologies for both matched beamforming and phased array (planar wavefront) beamforming. Extensive simulation results are presented.
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