QoS-Oriented Optimal Relay Selection in Cognitive Radio Networks

Algorithm 1

Relay selection algorithm.

1: N = Number of Relays;

2: NumberOfObjectives = 4; // i.e. 1: Throughput, 2: Delay, 3: Battery and 4: Buffer

3: Exchange CSI and Resource Information

4: //Discover the available incoming links, i.e. links

5: ListOfAvailableIncomingLinks[] = [] //List contains indices of available relays for Rx, initially the list is empty

6: NumberOfAvailableIncomingLinks = 0;

7: for i=1:N do

8:   if AND // SNR of link

    AND // Available buffer at relay

    // Batery power at relay

   then

9:     NumberOfAvailableIncomingLinks++;

10:     ListOfAvailableIncomingLinks[NumberOfAvailableIncomingLinks] = i;

11:   end if

12: end for

13: //Discover the available outgoing links, i.e. links

14: ListOfAvailableOutgoingLinks[] = [] //List contains indices of available relays for Tx, initially the list is empty

15: NumberOfAvailableOutgoingLinks = 0;

16: for i=1:N do

17:   if AND // SNR of

    AND // Occupied buffer at relay

   // Batery power at relay

   then

18:     NumberOfAvailableOutgoingLinks++;

19:     ListOfAvailableOutgoingLinks[NumberOfAvailableOutgoingLinks] = i;

20:   end if

21: end for

22: // Now we select the best outgoing link out of the available outgoing links as per application QoS requirements.

23: selectedOutgoingRelayIndex = -1; // initially none selected

24: bestValue = 0; // initialized

25: for i=1: NumberOfAvailableOutgoingLinks do

26:   Y[ListOfAvailableOutgoingLinks[i]]=

27:   if Y[ListOfAvailableOutgoingLinks[i]] ¿ bestValue then

28:     bestValue = Y[ListOfAvailableOutgoingLinks[i]];

29:     selectedOutgoingRelayIndex = ListOfAvailableOutgoingLinks[i];

30:   end if

31: end for

32: // Now select the best incoming link out of the available incoming links as per application QoS requirements and also it is not the selected outgoing link.

33: selectedIncomingRelayIndex = -1; // initially none selected

34: bestValue = 0; // initialized

35: for i=1:NumberOfAvailableIncomingLinks do

36:   Y

37:   if Y[ListOfAvailableIncomingLinks[i]] ¿ bestValue AND

ListOfAvailableIncomingLinks[i] != selectedOutgoingRelayIndex then

38:     bestValue = Y[ListOfAvailableIncominggLinks[i]];

39:     selectedIncomingRelayIndex = ListOfAvailableIncomingLinks[i];

40:   end if

41: end for