  We formulate a first quantized construction of the AdS_{d+1}/CFT_d
correspondence using the bi-local representation of the free d-dimensional
large N vector model. The earlier reconstruction of AdS_4 higher-spin gravity
provides a scheme where the AdS spacetime (and higher-spin fields) are given by
the composite bi-local fields. The underlying first quantized, world-sheet
picture is extracted in the present work and generalized to any dimension. A
higher-spin AdS particle model is shown to emerge from the collective
bi-particle system of Minkowski particles through a canonical transformation.
As such this construction provides a simple explicit mechanism of the AdS/CFT
correspondence.
