# A Distributed Energy-Throughput Efficient Cross-Layer Framework Using Hybrid Optimization Algorithm
## 3 Energy-Throughput Efficient Cross-Layer Solution Using MPNMRA for WUSNs
### MI Techniques Used in WUSNs  
The architecture of direct MI communication involves a transmitter coil and a receiver coil, similar to transformers [21]. The transmitter coil carries a sinusoidal current that generates a corresponding sinusoidal current in the receiver coil through mutual induction, thereby facilitating communication [2], as shown in Figure 2[22].  
By leveraging the principles of mutual magnetic induction, WUSNs can establish reliable and efficient communication links within underground environments. This enables the deployment of WSNs for various applications, including monitoring, disaster prevention, and resource extraction, while overcoming the limitations of traditional electromagnetic wave-based communication methods. Indeed, while direct MI communication offers advantages for WUSN applications, there are limitations that need to be addressed. One such limitation is the limited communication range, which can restrict the coverage area of the network. To overcome this limitation, researchers have developed waveguide-based MI communication as an alternative approach.  
Waveguide-based MI communication utilizes waveguides, which are structures designed to guide and propagate electromagnetic waves to reduce transmission path loss and enhance the communication range in underground environments [22]. By employing waveguides, the communication signals can propagate over longer distances compared with direct MI communication. The use of waveguides in MI communication helps achieve a practical bandwidth for inter-sensor communication, enabling higher data rates and more efficient information exchange among sensors in WUSNs.  
Figure 3 illustrates the implementation of waveguide-based MI communication, highlighting its benefits in terms of increased communication range and reduced transmission path loss. By leveraging waveguide-based MI communication, WUSNs can overcome the limitations associated with direct MI communication, thereby enabling more extensive coverage, improved communication reliability, and efficient data exchange within the underground environment.  
Figure 2: Structure of direct MI communication [22].  
In the design of MI-based WUSNs, a configuration consisting of resonant relay nodes has been proposed [22].  
The use of relay nodes and multidimensional MI coils in this design leads to a reduction in path loss, improved system robustness, and an extended lifetime of the WUSN. The MI channel between the relay nodes and sensor nodes remains stable, ensuring reliable communication. Moreover, the deployment and maintenance of the network are made easier due to the flexible arrangement of coils, accommodating the presence of rocks, pipes, or changes in coil positions during operation.  
To address the impact of coil orientation on received signal strength, multidimensional MI coils, specifically 3D coils, have been designed and utilized. These 3D coils offer omnidirectional signal coverage, ensuring that the signals can be effectively transmitted and received regardless of the relative orientation between adjacent coils. This leads to cost-effectiveness, reduced system complexity, and high-quality transmission between the sensing nodes.  
Figure 4 illustrates the deployment and arrangement of multidimensional MI coils, showcasing their omnidirectional signal coverage and the minimal number of coils required for efficient transmission within the complex underground scenario. By employing resonant relay nodes and multidimensional MI coils, this design enhances the performance, reliability, and practicality of MI-based WUSNs, making them suitable for a wide range of underground communication applications.