  We propose, analyze and demonstrate an architecture for scalable cooperative
reception. In a cluster of N + 1 receive nodes, one node is designated as the
final receiver, and the N other nodes act as amplify-and-forward relays which
adapt their phases such that the relayed signals add up constructively at the
designated receiver. This yields received SNR scaling linearly with N, while
avoiding the linear increase in overhead incurred by a direct approach in which
received signals are separately quantized and transmitted for centralized
processing. By transforming the task of long-distance distributed receive
beamforming into one of local distributed transmit beamforming, we can leverage
a scalable one-bit feedback algorithm for phase synchronization. We show that
time division between the long-distance and local links eliminates the need for
explicit frequency synchronization. We provide an analytical framework, whose
results closely match Monte Carlo simulations, to evaluate the impact of phase
noise due to relaying delay on the performance of the one-bit feedback
algorithm. Experimental results from our prototype implementation on
software-defined radios demonstrate the expected gains in received signal
strength despite significant oscillator drift, and are consistent with results
from our analytical framework.
