Strategies for Java ORM with Unreliable Network and Low Bandwidth

I am looking at Hibernate for a system which needs to work in an unreliable network. There is a single central database that we need read-write access to, but it is available over a pretty patchy wi-fi network. In addition, there may be power losses which do not shutdown the application cleanly, so any solution must have a persistent cache which can survive power-cycles. Lastly this is an embedded system with only modest memory, and disk space so for example doing full blown replication of the database is not a feasible strategy.

I have a basic understanding of Hibernate 2nd Level caching, and I am wondering if it is possible to configure this with something like Ehcache to solve this problem, but the main thrust of that seems to be performance not availability, so I am not aware of what the pitfalls might be.

I am also quite willing to consider other strategies which involve replication to a local database. I would rather not have to do too much of the heavy lifting myself to implement this.

Looking for some experience or possible alternatives.