  We propose a concept system termed distributed base station (DBS), which
enables distributed transmit beamforming at large carrier wavelengths to
achieve significant range extension and/or increased downlink data rate,
providing a low-cost infrastructure for applications such as rural broadband.
We consider a frequency division duplexed (FDD) system, using feedback from the
receiver to achieve the required phase coherence. At a given range, $N$
cooperating transmitters can achieve $N^2$-fold increase in received power
compared to that for a single transmitters, and feedback-based algorithms with
near-ideal performance have been prototyped. In this paper, however, we
identify and address key technical issues in translating such power gains into
range extension via a DBS. First, to combat the drop in per-node SNR with
extended range, we design a feedback-based adaptation strategy that is suitably
robust to noise. Second, to utilize available system bandwidth, we extend
narrowband adaptation algorithms to wideband channels through interpolation
over OFDM subcarriers. Third, we observe that the feedback channel may become a
bottleneck unless sophisticated distributed reception strategies are employed,
but show that acceptable performance can still be obtained with standard uplink
reception if channel time variations are slow enough. We quantify system
performance compactly via outage capacity analyses.
