Algorithm 1. Image transmission algorithm.

//P(v): v’s downstream node //C(v): v’s upstream node //v.rch: v’s reception channel //v.tch: v’s transmission channel

1    At GW://requests image from srcMN 2       broadcast IREQ = (srcMN, WSNpath, WSNChList, dCHm); 3    At node v that receives IREQ: 4    if v = srcMN then 5       curTime = systemTime(); 6       set nextTxTimer = curTime + TxInt; 7       change myLoRaCh to dCHm;//channel switching 8       srcMN.tch = WSNChList [0];//takes the first channel 9       transmit iPacket on srcMN.tch using WSN; 10   else if v belongs to WSNpath then 11     turn on WSNmodule; 12     (v.rch, v.tch) = chMapping(v, WSNpath, WSNChList); 13     wait for iPacket on v.rch; 14   endif; //Transmits iPackets at TxInt intervals 15   At srcMN that nextTxTimer expires: 16     curTime = systemTime(); 17     set nextTxTimer = curTime + TxInt; 18     transmit iPacket on v.tch; //Forwarding packet and waiting for new packet 19   At node v that receives iPacket from C(v): 20   transmit iPacket to P(v) on v.tch; 21   wait for iPacket on v.rch; //myPos = index in WSNpath starting with 1 //WSNChList = list of three channels 22   function chMapping(v, WSNpath, WSNChList); //myPos > 1 since v cannot be srcMN 23     myPos = findPos(v, WSNpath); 24     if myPos is even then//dedicated channel 25          k = (myPos/2 - 1) % 3; 26          v.rch = v.tch = WSNChList [k]; 27     else//if odd 28          k = ((myPos − 1)/2 − 1) % 3; 29          v.rch = WSNChList[k];//upstream node ch 30          k = ((myPos + 1)/2 − 1) % 3; 31          v.tch = WSNChList [k];//downstream node ch 32     endif; 33     return (v.tch, v.rch); 34   endFunction