1. Symmetric Detection

2. Overview In this phase, each mote will maintain a neighbor table. It provide a command bool isSymmetric(uint16_t neighborID) for the backbone creation phase. The judgment is based on the statistic.

3. Overview Provides interface –SDNeighborTable –StdControl Used components –SDM –RoutingC –RandomLFSR –TimerC –TinyAlloc

4. Data Structure sendIdsizeData 2 1 18 Every neighborID occupies 2 bytes, so one packet can accommodate 18/2=9 neighborID MAX_NEIGHBOR = 40 Totally we need 5 packets at most. MAX_SD_BUFFER_SIZE = (MAX_NEIGHBOR+5)/10, Shall we use MAX_NEIGHBOR/9+1? Or shall we change the SD_PAYLOAD_SIZE= 18 ?

5. Data Structure typedef struct{ uint16_t neighborID[MAX_NEIGHBOR]; uint8_t symmChannel[MAX_NEIGHBOR]; uint8_t asymmChannel[MAX_NEIGHBOR]; uint8_t noChannel[MAX_NEIGHBOR]; uint8_t currStatus[MAX_NEIGHBOR]; /* 0------noChannel 1------asymmChannel 2------symmeChannel */ uint8_t aliveLastTime[MAX_NEIGHBOR]; } NEIGHBOR_TABLE; Note:neighborID[0..MAX_NEIGHBOR] is initialed to be 0xffff

6. Workflow Scan the neighbor table Generate packets to be send Start a new Timer Send Packet Check Neighbor table Interval of T1:SEND_BEACON_PERIOD Interval of T2:(Random.rand()) % (SEND_BEACON_PERIOD/global_size) Check Neighbor table

7. Workflow How about the last packet in the T1 interval If the process to generate packets is too long or due to other delay, then the last packet will be lost. Guarantee that SEND_BEACON_PERIOD/global_size - beacon_delay > 640

8. Rules checkNT() will examine the previous round status and update the statistical value. Once a mote receive a packet, it examine the sendID first, then examine the string of neighbor ID to judge whether it is symmetric in previous round. If a node does not receive a packet from a certain node in a round &&nodeId is in the neighbortable-> no channel in this round.

9. Overflow Node 10 Node 11 Neighbor[0]=11 Neighbor[0]=10 Cur[0]=asy Cur[0]=sym checkNT Syn[0]=1 checkNT Syn[0]=1 noChan[0]=1 checkNT Syn[0]=2 checkNT Syn[0]=1 noChan[0]=2 checkNT Syn[0]=2 Ayn[0]=1 Cur[0]=sym Cur[0]=noChan Cur[0]=asy

10. Parameters SEND_BEACON_PERIOD –Interval for T1 CHECKNT_WAIT_TIMES –In which round it starts to do checkNT() global_threshold –numSymm /(numAsymm + numSymm + numNone) >= (global_threshold/100) Also, the system should carefully the number of round to detect symmetric

11. Parameters Node 10 Node 11 Neighbor[0]=11 Neighbor[0]=10 Cur[0]=asy Cur[0]=sym checkNT Syn[0]=1 checkNT Syn[0]=1 noChan[0]=1 checkNT Syn[0]=2 checkNT Syn[0]=1 noChan[0]=2 checkNT Syn[0]=2 Ayn[0]=1 Cur[0]=sym Cur[0]=noChan Cur[0]=asy If the motes are fully synchronized,then the third time it could do checkNT()

12. If motes are not fully synchronized, then forth timer is the best time to start do checkNT().

13. Neighbor table: 7byte*MAX_NEIGHBOR MAX_SD_BUFFER_SIZE*sizeof(TOS_Msg)) If we do not plan to do the judgment on multiple rounds. Then we do not need to have uint8_t symmChannel[MAX_NEIGHBOR]; uint8_t asymmChannel[MAX_NEIGHBOR]; uint8_t noChannel[MAX_NEIGHBOR]; uint8_t aliveLastTime[MAX_NEIGHBOR];