Multiterminal estimation - extensions and geometric interpretation

There are two approaches to establishing estimation efficiency bounds in a multiterminal setting. Zhang and Berger (see IEEE Trans. Inf. Theory, vol.34, no.2, p.198-211, 1988) derive a bound using the so-called solvability conditions. Han and Amari (see IEEE Trans. Inf. Theory, vol.41, no.6, p.1802-33, 1995) tighten the bound under weaker rate and test channel constraints, but their bound is prohibitively complex to compute. Here we construct a bound that is asymptotically equal to the Han and Amari bound, yet easily computed and has a geometric interpretation.