Table 1 Parameter configuration

Number of HeNB

9

Average number of neighbors

6 ∼7

Number of HUEs per cell

2

Number of channel

2

HeNB antennas

2

HUE antennas

1

Channel bandwidth

0.18 (MHz)

Maximum power

20 (dBm)

Path loss model [28] (dB)

\(\left \{ \begin {array}{l} 30\log _{10}D+37{\text {,indoor}}\\ 30\log _{10}D+5n+37{\text {,outdoor}}\\ D-{\text {distance}}\\ n-{\text {number\; of\; walls}} \end {array} \right. \)

MISO channel [23]

\(\left \{ \begin {array}{l} {{\mathbf {h}}_{\textit {ij}}} = PL \cdot {{\mathbf {c}}_{\textit {ij}}}\\ {{\mathbf {c}}_{\textit {ij}}} \sim {\cal C}{\cal N}\left ({{\mathbf {0}},{\mathbf {I}}} \right) \end {array} \right.\)

Step size of Loop1

\(\phi _{k} = \frac {7}{{{{{\text {(k + 1)}}}^{0.7}}}}\)

SCA_max

5

Alt_max

1