Table 1 The parameter settings for the simulation study

α

Pass loss exponent

4

η _p

Threshold of the PR in the primary network

4 dB

d ₀₀

Distance between PT and PR

d

d _i0

Distance between a secondary transmitter and the PR

100 m

d _ij

Distance between a secondary transmitter and its destination

20 m

d _0j

Distance between the PT and a secondary receiver

\(\sqrt {120^{2}+100^{2}}\)m

β

Angle between the line of Relay-PR and that of PT-PR

0, \(\frac {\pi }{3}\)

d _r0

Distance between relay and PR

dr

d _0r

Distance between PT and relay

\(\sqrt {(d-dr\cdot \cos {\beta })^{2}+(dr\cdot \sin {\beta })^{2}}\)m

d _ir

Distance between the secondary transmitter and the relay

\(\sqrt {100^{2}+d^{2}}\)m

d _rj

Distance between the relay and a secondary receiver

\(\sqrt {100^{2}+(d+20)^{2}}\)m