On the characters of unipotent representations of a semisimple p-adic   group
  Let G be a semisimple almost simple algebraic group defined and split over a nonarchimedean local field K and let V be a unipotent representation of G(K) (for example, an Iwahori-spherical representation). We calculate the character of V at compact very regular elements of G(K) at compact very regular elements of G(K). 
Ju-Lee Kim and George Lusztig
math.RT