  Emerging autonomous farming techniques rely on smart devices such as
multi-spectral cameras, collecting fine-grained data, and robots performing
tasks such as de-weeding, berry-picking, etc. These techniques require a high
throughput network, supporting 10s of Mbps per device at the scale of tens to
hundreds of devices in a large farm. We conduct a survey across 12 agronomists
to understand these networking requirements of farm workloads and perform
extensive measurements of WiFi 6 performance in a farm to identify the
challenges in meeting them. Our measurements reveal how network capacity is
fundamentally limited in such a setting, with severe degradation in network
performance due to crop canopy, and spotlight farm networks as an emerging new
problem domain that can benefit from smarter network resource management
decisions. To that end, we design Cornet, a network for supporting on-farm
applications that comprises: (i) a multi-hop mesh of WiFi routers that uses a
strategic combination of 2.4GHz and 5GHz bands as informed by our measurements,
and (ii) a centralized traffic engineering (TE) system that uses a novel
abstraction of resource units to reason about wireless network capacity and
make TE decisions (schedule flows, assign flow rates, and select routes and
channels). Our evaluation, using testbeds in a farm and trace-driven
simulations, shows how Cornet achieves 1.4 $\times$ higher network utilization
and better meets application demands, compared to standard wireless mesh
strategies.
