Mathematical Channel Modeling of Electromagnetic Waves in Biological Tissues for Wireless Body Communication
Round 1
Reviewer 1 Report
This work demonstrated the characteristics of inhomogeneous planar human tissue exposed to incident plane waves, based on 373 an analytical model, by using the Method of Moments (MoM). The manuscript is well organized. Some minor concerns are suggested.
1\The article mentions FDTD method several times, and compares it with MoM and FEM method. However, there are no formulas or diagrams related to FDTD method. It is suggested to add some relevant demonstration.
2\The English language should be carefully corrected. For example, subject is missing in Line 269 "is the incident signal perpendicular to the skin layer".
Author Response
Reply to the Reviewers
We would like to thank the reviewers for reading, reviewing, and commenting on our manuscript. Those comments are all valuable and very helpful for revising and improving our manuscript to a better scientific level. We have carefully studied the raised comments and made corrections, which we hope meet your requirements. The revised portions are marked in red and visible on the paper.
Below, we provide answers to the raised questions and comments in detail.
Reviewer: 1
- The article mentions FDTD method several times and compares it with MoM and FEM method. However, there are no formulas or diagrams related to FDTD method. It is suggested to add some relevant demonstration.
We thank the reviewer for the comment. Electromagnetic simulation-based channel modeling presents a good technique for solving several problems and it has gained a lot of interest in recent years. Full-wave solutions aim to accurately determine the channel characteristics by solving Maxwell’s equations using numerical approaches. In Wireless Body Area Network (WBAN) applications, the most used full-wave numerical approach for channel modeling is the FDTD method. This technique is based on the iterative solution of the discretized Maxwell’s equations in the time domain. Despite its wide use, the FDTD method has several limitations. Firstly, it requires the entire computational domain to be meshed into small cells, with a size smaller than the smallest wavelength used in the simulations. Secondly, it assumes the use of homogeneous mesh cells, which can become impractical in complex models involving several different materials. As a result, the computational burden of FDTD can become excessive, particularly at higher frequencies. Despite the limitations of the FDTD method, there are alternative techniques that can offer better solutions for complex channel modeling in the WBAN context. One such approach is MoM method which operates in the frequency domain and can accurately model and analyze the complex behavior of heterogeneous material properties and geometries. In this study, we propose the use of the MoM method to analyze the complexity of consecutive human body tissues with high accuracy, in a minimum amount of time. This method works by solving the integral form of Maxwell’s equations over the boundaries, allowing for an accurate analysis of the electromagnetic fields in the given scenario. The MoM method has several advantages, such as being able to model a wide range of geometries and material properties and often presenting the same advantages as the Finite Element Method (FEM), which we used to validate our analytical model.
To address the reviewer’s point, we added the sentence below in the Introduction section:
As compared to MoM, FDTD requires the entire domain analysis to be meshed into small cells, with a size smaller than the smallest wavelength used in the simulation. It also assumes the use of homogenous mesh cells, which can become impractical in complex models involving several different materials. Moreover, MOM operates in the frequency domain, and can accurately be used to analyze the complex behavior of heterogeneous material properties. It is a very powerful method when studying inhomogeneous complex shapes [20] [22] [23].
- The English language should be carefully corrected. For example, subject is missing in Line 269 "is the incident signal perpendicular to the skin layer".
We thank the reviewer for the remark. To address the reviewer’s point, we correct the sentence in section 3.3 Simulation settings as fellow: Ei=1(V/m) is the incident signal perpendicular to the skin layer.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper describes an investigation into electromagnetic wave penetration in biological tissue, which is strongly influenced by frequency and tissue thickness. The steady-state electromagnetic distribution is calculated using the Method of Moments (MoM), and the results are compared to analytical and Finite Element Method (FEM) results. The study demonstrates the Path Loss channel model's ability to estimate the Power Loss Density (PLD) and Path Loss (PL) in WBANs and to determine communication quality in various scenarios.
The main work of the authors in this work is , a mathematical formulation based on the solution of DIE using the MoM.
1-Have the authors done any practical analysis or only simulation work?
2- What is the difference between heading 2.2 an 2.3?
2.2 Lossy to Lossy medium: Fat to Muscle Human Tissue
2.3 Lossy to Lossy medium: Fat to Muscle Human Tissue
Author Response
Reply to the Reviewers
We would like to thank the reviewers for reading, reviewing, and commenting on our manuscript. Those comments are all valuable and very helpful for revising and improving our manuscript to a better scientific level. We have carefully studied the raised comments and made corrections, which we hope meet your requirements. The revised portions are marked in red and visible on the paper.
Below, we provide answers to the raised questions and comments in detail.
Reviewer: 2
- Have the authors done any practical analysis or only simulation work?
We thank the reviewer for the comment. In this paper, we present an analytical study to model a Wireless Body Area Network (WBAN) with different communication scenarios using the method of Moments. In fact, modeling the behavior of WBAN can be challenging due to the complex distinctive of human tissues. Most of the proposed analytical models, presented in the literature, is based on the time domain (FDTD method for example). However, the time domain methods require a large computational time and memory, as they use uniform mesh for the entire computational domain. In this work we highlight the potential of using the Method of Moments (MoM), which is a frequency domain method, to solve the integral Maxwell equations in the case of the interaction between electromagnetic waves and Human tissues with high accuracy with reduced computational time. The results presented in this paper, using the MoM method, corroborate those using the finite element method under the same conditions.
- What is the difference between heading 2.2 and 2.3? 2.2 Lossy to Lossy medium: Fat to Muscle Human Tissue. 2.3 Lossy to Lossy medium: Fat to Muscle Human Tissue.
We thank the reviewer for this comment. In section 2.2, we explained the propagation mechanisms within only muscle. We assumed that the transmitting antenna Tx is in a fat layer on the surface of the muscle. While the receiving antenna Rx is placed in the lossy medium of human muscle tissue. For this study, various Rx locations are investigated. In section 2.3, we exposed the interaction between electromagnetic waves with human tissues. The Tx antenna is placed on the skin, and the insulated Rx antenna is placed in the layered model. This layered model consists of the skin, and fat tissue, and ends at the muscle layer.
To address the reviewer’s point, we changed the section 2.3 label as fellow: 2.3 Lossless to Lossy medium: Air to Layers Equivalent to human tissue.
Author Response File: Author Response.docx
