  The high pseudo-rapidity region of the CMS muon system is covered by Cathode
Strip Chambers (CSC) only and lacks redundant coverage despite the fact that it
is a challenging region for muons in terms of backgrounds and momentum
resolution. In order to maintain good efficiency for the muon trigger in this
region additional RPCs are planned to be installed in the two outermost
stations at low angle named RE3/1 and RE4/1. These stations will use RPCs with
finer granularity and good timing resolution to mitigate background effects and
to increase the redundancy of the system.
