  We propose a decentralized spatial soft-core cache placement (SSCC) policy
for wireless networks. SSCC yields a spatially balanced sampling via negative
dependence across caches, and can be tuned to satisfy cache size constraints
with high probability. Given a desired cache hit probability, we compare the
95% confidence intervals of the required cache sizes for independent placement,
hard-core placement and SSCC policies. We demonstrate that in terms of the
required cache storage size, SSCC can provide up to more than 180% and 100%
gains with respect to the independent and hard-core placement policies,
respectively. SSCC can be used to enable proximity-based applications such as
device-to-device communications and peer-to-peer networking as it promotes the
item diversity and reciprocation among the nodes.
