The first algorithm, complete NCL, serves as a benchmark
and it corresponds to the situation when a call drop rate reaches
its minimum since the NCL contains all potential target eNBs
and all belonging HeNBs. For the handover history in the
second and the fourth scheme, Pt is set to 1 % according to
[7][16]. Thresholds for selection of the post eNB and serving
HeNB in the third algorithm are -90 dBm and -80 dBm
respectively [3]. The selection of the post eNB is finished after
scanning an eNB with signal quality above -90 dBm in the
hierarchical approach. This can lead to a selection of incorrect
eNB and thus to an increase in call drop rate. Therefore, we
define also enhanced hierarchical algorithm. Difference
between the hierarchical and enhanced hierarchical approach
consists in the following. First, handover statistics are
considered (according to [7][16])) in enhanced version to
reduce the amount of eNBs to be scanned. Further, scanning of
the eNBs is performed over all potential neighbor eNBs
(considering handover statistics) to avoid selection of an
incorrect post eNB.