  In this paper, the radiation field is defined for solutions to Einstein
vacuum equations which are close to Minkowski space-time with spacial dimension
$n\geq 4$. The regularity properties and asymptotic behavior of those Einstein
vacuum solutions are established at the same time. In particular, the map from
Cauchy intial data to the radiation field is proved to be an isomorphism when
restricting to a small neighborhood of Minkowski data in suitable weighted
b-Sobolev spaces.
