  In blind detection, a set of candidates has to be decoded within a strict
time constraint, to identify which transmissions are directed at the user
equipment. Blind detection is an operation required by the 3GPP
LTE/LTE-Advanced standard, and it will be required in the 5th generation
wireless communication standard (5G) as well. We propose a blind detection
scheme based on polar codes, where the radio network temporary identifier
(RNTI) is transmitted instead of some of the frozen bits. A low-complexity
decoding stage decodes all candidates, selecting a subset that is decoded by a
high-performance algorithm. Simulations results show good missed detection and
false alarm rates, that meet the system specifications. We also propose an
early stopping criterion for the second decoding stage that can reduce the
number of operations performed, improving both average latency and energy
consumption. The detection speed is analyzed and different system parameter
combinations are shown to meet the stringent timing requirements, leading to
various implementation trade-offs.
