# Energy Transmission and Equilibrium Scheme in Data Communication Opportunistic Networks
## 2 System Model Design  
In opportunistic networks, nodes carry different data packets in communication. They transmit data packets by moving and creating communication areas. However, some nodes carrying a great number of different important data packets have high transmission frequency when transmitting messages; the other nodes may carry a few data packets and take part in communication rarely. Therefore, active nodes which have a high transmission frequency when transmitting messages consume energy very soon; inactive nodes carry energy but take part in communication rarely. In data communication, the effective energy equilibrium of active and inactive nodes may improve the quality in transmitting and energy supply. Moreover, in the IoT communication application, active nodes can be supplied with energy from inactive nodes, and then extend their life-times. Inactive nodes also have more of an opportunity to join in the communication. In order to solve this problem, the scheme PSDRA considers three problems. 1. Active nodes need to supply enough energy to guarantee that data packets transmit data communication. 2. Inactive nodes must be utilized effectively. They can transmit energy to active nodes and join the active nodes. 3. The energy for each node should become an equilibrium when the node transmits data packets. If these problems can be solved, the performance of the opportunistic network will be improved. The epidemic algorithm is a kind of typical opportunistic network algorithm. It can acquire maximal exclusive data packets. Therefore, when two nodes \(A\) and \(B\) transmit data packets, node \(A\) can acquire data packets which node \(A\) has not carried but node \(B\) has. Then, node \(B\) transmits these packets to node \(A\). The same condition is applied to node \(B\), which is similar to an epidemic. This algorithm may acquire maximal effective data packets in communication. Especially in data communication, effective data packets transmission is important, since it can improve the delivery ratio and reduce energy consumption. However, this algorithm has a problem in which no energy can be supplied among the nodes. In this algorithm, nodes become dead very soon in data communication, since more data packets transmit and over consume energy. A new method which is applied in data communication is energy supply and equilibrium. In order to extend the nodes life-times when there are a great number of nodes transmitting data packets and consuming energy, the scheme is designed as follows:  
1. Set the transmission threshold. In Figure 1, node \(A\) and \(B\) send request \(A\) and request \(B\) to each other. When they receive a request, they can send data packets which they carry while its neighbor has not. In communication, the average transmission data packets \(p_{ave}\) between \(A\) and \(B\) are: \[p_{ave}=\frac{p_{<A,B>}+p_{<B,A>}}{2}\] (1) where \(p\) is the transmission data packet, \(p_{<A,B>}\) are the data packets transmitted from \(A\) to \(B\). Node \(A\) sends the data packets \(p_{<A,B>}=p_{A}\cap\overline{p_{B}}\). At the same time, node \(B\) receives \(p_{<A,B>}\) and sends data packets \(p_{<B,A>}=p_{B}\cap\overline{p_{A}}\) to node \(A\). Then, node \(A\) receives data packets \(p_{<B,A>}\). Additionally, node \(B\) receives data packets \(p_{<A,B>}\). Where the average transmission data packets act as a threshold. Especially in data communication, the average transmission threshold can control the over-selection and over-transmission among nodes. 2. Difference in transmitting data packets. If the transmission of data packets \(p\) and threshold \(p_{ave}\) have the relationship \(p-p_{ave}\geq 0\). For a node, it indicates that sending packets is more than receiving; otherwise, \(p-p_{ave}<0\). Nodes can judge how many new data packets they gain and send and how many data packets are by themselves. It is important for the nodes to calculate the energy consumption. 3. Energy consumption. When two nodes meet, they establish a communication area in the opportunistic network.