  In this paper, the robust distributed relay beamforming problem is solved
using the worst case approach, where the problem solution has been involved
because of the effect of uncertainty of channel knowledge on the quality of
service (QoS) constraints. It is shown that the original robust design, which
is a non-convex semi-infinite problem (SIP), can be relaxed and reformed to a
semi-definite problem (SDP). Monte-Carlo simulations are presented to verify
the performance improvement of our proposed robust problem over existing robust
and non-robust problems in terms of transmit power and symbol error
probability.
