  We present Saguaro, a permissioned blockchain system designed specifically
for edge computing networks. Saguaro leverages the hierarchical structure of
edge computing networks to reduce the overhead of wide-area communication by
presenting several techniques. First, Saguaro proposes coordinator-based and
optimistic protocols to process cross-domain transactions with low latency
where the lowest common ancestor of the involved domains coordinates the
protocol or detects inconsistency. Second, data are collected over hierarchy
enabling higher-level domains to aggregate their sub-domain data. Finally,
transactions initiated by mobile edge devices are processed without relying on
high-level fog and cloud servers. Our experimental results across a wide range
of workloads demonstrate the scalability of Saguaro in supporting a range of
cross-domain and mobile transactions.
