Thuật toán XTC: (thuật toán cho nút u) Pmax là nút tối đa truyền tải điện năng N (u) là hàng xóm của nút u DN (u) là tập hợp của hàng xóm bỏ đi FN (u) là hàng xóm của u nút trong cuối cùng cấu trúc liên kết p (u) là sức mạnh cuối cùng (phát sóng) truyền của nút u 1. Khởi tạo N (u) = ∅ DN (u) = ∅ FN (u) = ∅ 2a. | 140 NEIGHBOR-BASED TOPOLOGY CONTROL Algorithm XTC algorithm for node u Pmax is the maximum node transmit power N u is the neighbor set of node u DN u is the set of discarded neighbors FN u is the neighbor set of node u in the final topology p u is the final broadcast transmit power of node u 1. Initialization N u 0 DN u 0 FN u 0 2a. ID broadcast send message u Pmax at maximum transmit power Pmax 2b. Neighbors detection upon receiving message v Pmax from node v N u N u u v determine the received signal strength and store this information 3. Exchange ordered neighbors list after all the messages from neighbors have been received order nodes in N u according to the received signal strength 3a. send message u N u at maximum transmit power Pmax 3b. upon receiving ordered neighbors list v N v from node v store this information 4. Determine final neighbor set after the ordered neighbor lists from all the nodes in N u have been received for each v e N u in decreasing order of link quality if 3w e DN u u FN u such that w . u then DN u DN u u v otherwise FN u FN u u v 5. Transmit power computation p u minimum power level needed to reach the farthest node in FN u Figure The XTC protocol. NEIGHBOR-BASED TOPOLOGY CONTROL 141 with a RSSI register and orders its neighbor set accordingly. So exchanging n messages overall every node sends one message at maximum power is sufficient to compute the neighbors order. Once the neighbor set has been computed and ordered every node broadcasts the ordered neighbor list at maximum power this also requires sending n messages overall . The final step of XTC that is the computation of the final topology can be done locally at each node with no further message exchange. To compute the network topology node u considers its neighbors in decreasing order of link quality when considering a certain neighbor v it checks whether there exists a node w with w u v . with better link quality such that w v u. Note that this check can be done locally
