Hi,
i assume that the received vector you have is signal at receiver input.
The very first thing that is necessary for the receiver is synchronization - basically receiver should know the strongest path.
There should be some kind of sinchronisation info available in the telecom system - preamble, midamble, pilot channel or pilot subcarriers. A correlation should be run on received signal against sinchronization pattern. The correlation peak would give the strongest path. For MIMO system correlation must be performed for each branch separately.
If there is no correlation, then the signal is too weak, i.e. below receiver sensitivity level.