  The massive amounts of bandwidth available at millimeter-wave frequencies
(roughly above 10 GHz) have the potential to greatly increase the capacity of
fifth generation cellular wireless systems. However, to overcome the high
isotropic pathloss experienced at these frequencies, high directionality will
be required at both the base station and the mobile user equipment to establish
sufficient link budget in wide area networks. This reliance on directionality
has important implications for control layer procedures. Initial access in
particular can be significantly delayed due to the need for the base station
and the user to find the proper alignment for directional transmission and
reception. This paper provides a survey of several recently proposed techniques
for this purpose. A coverage and delay analysis is performed to compare various
techniques including exhaustive and iterative search, and Context Information
based algorithms. We show that the best strategy depends on the target SNR
regime, and provide guidelines to characterize the optimal choice as a function
of the system parameters.
