【正文】 9. Go to Construction Phase。 7. Copy value of GHC from the Inform packet to the respective field of the Construct packet。 5. Estimate effective transmission power (PTx(ij)) between the closest sender and itself。 For any Receiver(j): 1. If: (Receives Inform packet) 2. { 3. Wait for random time patible to CSMACA mechanism。 7. Broadcast the Inform packet。 5. Initialize: All parameters of the Inform packet。 13. Go to Maintenance Phase, as described in Section (C). Table 3. Information phase algorithm for both Sender and Receiver ALGORITHM 2: Information Phase For any Sender(i): 1. If: (Receives Construct packet) 2. { 3. Copy value of PGID and GHC from the Construct packet。 10. Go to Information Phase。 8. Broadcast the Construct packet。 6. Set: Pmin=0。 4. Scan LHC of each received packets。 5. Go to Information Phase。 3. Broadcast the Construct packet。 Current consumption (mA) . Definitions ? Upstream and Downstream Groups: Let {G1, G2, G3, …} be the set of group of nodes distributed over certain area. If two groups Gi and Gj, for i ≠ j, such that a control packet is forwarded from any node of Gi to Gj, then Gi is known as the upstream group with respect to Gj and Gj is the downstream group with respect to Gi. For example, in Fig. 1, group G1 that contains the sink node is considered as the upstream group with respect to the groups G2, G3 and G4, as the control packet is initially broadcast from the group containing the sink to other groups of the work. G2, G3 and G4 are the downstream groups with respect to G1. Similarly, G2 can be an upstream group for the groups G3 and G4, if control packets are broadcast from G2 to those groups and in that case, G3 and G4 are treated as the downstream groups for G2. ? Local Hop Counts (LHC): It is a counter, which represents the number of hops that a control packet traverses locally within a group, when it is forwarded from one node to other. The value of LHC of a control packet is initialized to 0 and incremented by 1 for each subsequent hopping of the packet within the same group. In general, LHC = LHC + 1. Within a group, if node A forwards a packet to B, and then B forwards the same packet to C, value of LHC in the control packet of A = 0, B = 1 and C = 2. ? Group Hop Counts (GHC): It is a counter, which represents the number of hops that a control packet passes, when it is transmitted from one group to other. The value of GHC is unique for all nodes of a particular group and it is incremented by 1, if the packet is transmitted from one group to other. Value of GHC is initialized to 0 and in general GHC = GHC + 1, for the subsequent hopping of the packet from one group to other. Mathematically, let G = {g1, g2, …, gn} be the set of n sensor nodes in a group and be the set of m sensor nodes in another group, for same or different value of m and n. If value of GHC = p, gi G, then , value of GHC = q, where p ≠ q, as G and are different group of nodes. In our protocol, since sink node initiates the construction phase, which is in G1, value of GHC for all nodes of G1 in Fig. 2, is 0 and if the packet is forwarded from G1 to any other groups like G2 or G4, value of GHC in the packet is increment by 1. Hence, value of GHC = 1, for G2 or G4. ? Parent Gateway ID (PGID): The node that leads all nodes of a group to connect with a node of an upstream group is known as the Parent Gateway and its ID is termed as PGID. In each group of nodes, there exists only one Parent Gateway. Fig. 2. Parent and child gateways of different group of nodes. ? Child Gateway: The node that connects to the parent gateway of a downstream group is known as the Child Gateway. In a group, there exists at least one child gateway. In certain cases, if a group contains only one node, that single node is treated as both parent and child gateway for that group. In Fig. 2, nodes A and B of group G1 are the child gateways of nodes D and C, respectively. ? Node Energy Level (NEL): The current energy level of a node is called NEL. For example, at the time of broadcasting a control packet, if energy level of a node is x units, NEL is assigned as x units in the control packet. ? Parent Gateway Power Level (PGPL): The transmission power level of the parent gateway of any group with which it can be connected with the child gateway of an upstream group is known as Parent Gateway Power Level (PGPL). Since, sink is always the parent gateway in its group, its PGPL is assigned to 0. However, for the parent gateway of other groups, Pmin PGPL Pmax, which may have value between 1 and 3, as per our assumption. ? Source ID (SID): If A and B are two different sensor nodes of the same or different groups such that A sends packet to B, A is the source for B and ID of node A is the Source ID (SID). 3. The distributed power control protocol In this section we present our power control based topology construction protocol, which constructs the topology dynamically. We assume that each node in the work has a unique ID and each of them knows its onehop neighbor’s ID prior to the construction of the topology. As per the system model of our protocol, since connectivity holes exist among each group of nodes, we assume that the work may be disconnected, if they use low transmission power level between one group of nodes with another and can consume more energy, if they use maximum transmission power level for munication. Moreover, in our assumption the transmission power level for all nodes in the work after deployment could be maximum or in between minimum and maximum. So, in our protocol, a tree topology is constructed among each group of nodes using minimum transmission power level (Pmin = 0 here) and a connected tree topology of the whole work is formed among differ