Algorithm 3: Communication between the clusters. The cooperative modulation diversity with spectrum sensing is invoked if errors occur.

for i ← 1 to #packets do

CH transmits a new packet;

Receiver checks the CRC;

if CRC== correct then

Receiver sends back an ACK;

else

Receiver sends back a NACK;

Nr = 0;

for j ← 1 to $N_r^{\mathit{\text{max}}}$ do

CH transmits Q2 and I1 in the time slot 1;

Vice-CH performs spectrum sensing in the time slot 1;

Vice-CH transmits Q1 and I2 in the time slot 2;

CH performs spectrum sensing in the time slot 2;

if A request to emergency reporting is detected then

Vice-CH forwards the emergency information;

CH transmits the rest of the packet by simply QPSK;

else

Both CH and Vice-CH keeps cooperating;

end

Receiver checks the CRC;

if CRC == correct then

Receiver sends back an ACK;

else

Receiver sends back a NACK;

end

end

end

end