The Effect of Perturbations of Frames and Fusion Frames on Their   Redundancies
  An interesting question about the perturbed sequences is: when do they inherit the properties of the original one? An elegant relation between frames (fusion frames) and their perturbations is the relation of their redundancies.   In this paper, we investigate these relationships. Also, we express the redundancy of frames (fusion frames) in terms of the cosine angle between some subspaces. 
Asghar Rahimi, Golaleh Zandi, Bayaz Daraby
math.FA