# A Cache Placement Strategy with Energy Consumption Optimization in Information-Centric Networking
## 3 An Energy Consumption Optimization for ICN
### Energy Consumption Model for Content Distribution Between Nodes  
The ICN consists of a plurality of user nodes and a plurality of network nodes connecting the users. Assume that there are \(m\) user nodes in the network, and the network nodes connecting these user nodes are \(n\). To simplify the model, the distribution rate of each node is assumed to be \(\tau\), and the communication channel between nodes is AWGN (Additive White Gaussian Noise). The network nodes are homogeneous. In order to eliminate the communication interference, CDMA (Code Division Multiple Access) is used in the communication between nodes and the receiving power of the nodes is set to GR (Gain Reduction). According to the network model of ICN, the energy consumed by the user to get the required content is composed of two parts. That is, the energy consumed for receiving the content requested by the user, and the energy consumed for the distribution of the content to the user.  
Content is distributed by node \(v_{y}\) to user node \(u_{x}\). The signal received by node \(u_{x}\) can be represented as:  
\[S_{x}(t)=a_{xy}\phi_{y}(t)+\omega_{x}(t) \tag{1}\]  
The theoretical basis in the formula is given in [18]. Among them, the amplitude of the signal transmitted by node \(v_{y}\) is \(\phi_{y}(t)\), and the attenuation factor of the channel from node \(v_{y}\) to user node \(u_{x}\) is \(a_{xy}\); \(\omega_{x}(t)\) is the AWGN with normal distribution, the mean value is 0, and the variance is \(g\) (noise power). The SNR (Signal Noise Ratio) at the user node \(u_{x}\) can be expressed as:  
\[f=G_{R}/g \tag{2}\]  
Among them, the lowest SNR for reliable distribution is \(f\), and the received signal power at user node \(u_{x}\) is \(G_{R}\), \(G_{R}=fg\), its signal amplitude is \((G_{R})^{1/2}\cdot a_{xy}\), and the transmit signal power is:  
\[G_{T}=\frac{G_{R}}{a_{xy}^{2}}=\frac{fg}{a_{xy}^{2}} \tag{3}\]  
In Formula (3), \(a_{xy}{}^{2}=e/d_{xy}\), where the distance from user node \(u_{x}\) to network node \(v_{y}\) is \(d_{xy}\), \(e\) is a constant, and thus Equation (3) is changed to:  
\[G_{T}=\frac{fgd_{xy}^{2}}{e^{2}} \tag{4}\]Then, the energy of \(c_{k}\) size is transmitted to the user node \(u_{x}\) by node \(v_{y}\). The energy consumed is:  
\[E_{yT}^{ccn}(c_{k})=c_{k}\tau(G_{E}+G_{T})=c_{k}\tau(G_{E}+\frac{fgd_{xy}^{2}}{ e^{2}}) \tag{5}\]  
Among them, the circuit power of the node is \(G_{E}\).  
The amount of energy consumed by the user node \(u_{x}\) for the content of the \(c_{k}\) size is:  
\[E_{xR}^{ccn}(c_{k})=c_{k}\tau(G_{E}+G_{R}) \tag{6}\]  
From Formulas (5) and (6), it is known that the energy consumption between the nodes is proportional to the size of the content and the square of the distance between the nodes, and is proportional to the content distribution rate. To sum up, the total energy consumption required to perform a complete content distribution between two nodes is obtained:  
\[E_{xy}^{ccn}(c_{k})=c_{k}\tau(G_{E}+G_{T}+G_{R}) \tag{7}\]  
\[E_{xy}^{ccn}(c_{k})=c_{k}\tau(G_{E}+\frac{fgd_{xy}^{2}}{e^{2}}+G_{R}) \tag{8}\]