# Two-Tier Cooperation Based High-Reliable and Lightweight Forwarding Strategy in Heterogeneous WBAN
## 4 Experiments Analysis and Discussion  
### Experimental Environment and Parameters Setting  
In WBAN, multi-hop data transmission can effectively reduce system energy consumption and prolong network life. This paper adopts a simulation experiment to verify the feasibility and efficiency of the proposed TTCF strategy; the experimental platform uses MATLAB 2020B, and the computer is mainly configured as a CPU 2.39 GHZ, 8 GB Memory, 64 bit Windows 10 operating system. In WBAN, the sensors with different health monitoring functions are distributed in the head, feet, legs, thighs, knees, abdomen, back, waist, chest, upper arm, forearm, neck and other parts of the human body, and are responsible for collecting physical signals such as blood pressure, blood oxygen, temperature, ECG, EEG, EMG and electroretinogram. With the change of human behavior, such as lying, sitting, standing and walking, or the loss of sensor energy, the relative position of the sensors on each part also changes. Obviously, the WBAN network environment is changing all the time. Due to the different functions of each sensor, their data rate, corresponding sampling frequency and initial energy are also greatly different. For example, the ECG and EEG sensors should have higher sampling frequency and initial energy than the temperature and blood pressure sensors, because the latter only reflects whether a person is healthy, while the former is a key signal that can reflect whether a person is alive or not. Therefore, in this paper, various functional sensors are set with different data rates, sampling frequencies and initial energy, as shown in Table 1.  
For ease of calculation, the energy consumption of all sensor nodes when compressing data is 0.05 J/bit, the energy consumption when transmitting data is set to 1 J/kb, the number of packets collected on each node is 10 to 100 and the size of each data packet is 1 KB to 2 MB. It is assumed that there is one sink node and 15 sensor nodes in WBAN at a certain time. The specific distribution is shown in Figure 3.  
In Figure 3, the red five-star represents the sink node, the position of which is the coordinate origin, and the positions of the other nodes are assigned with the sink node as the origin according to the posture of the human body at a certain time. The sensor node type is allocated according to its human body position, and it is necessary to ensure that there is at least one type in Table 1. Based on the node positions shown in Figure 3, EEG nodes include 1 and 2, ECG nodes are 5, 14 and 15, EMG nodes have 10, 12 and 13, blood  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sensor Type** & **Data Rate (Kbps)** & **Sampling Frequency (HZ)** & **Initial Energy (J)** \\ \hline temperature & 2.4 & 0.1 & 50 \\ blood pressure & 1.44 & 60 & 50 \\ blood oxygen & 7.2 & 300 & 80 \\ EMG & 45 & 150 & 60 \\ EEG & 60 & 200 & 70 \\ ECG & 72 & 250 & 70 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Sensor type and related parameters.  
Figure 3: An example scenario of node distribution in WBAN.  
pressure nodes contain 4 and 7, blood oxygen nodes are 3, 6 and 9 and temperature nodes include 8 and 11. According to the node distribution in Figure 3, sensors 5, 6, 9 and 10 are the four closest to the sink node and usually undertake a large number of forwarding tasks; 3, 12 and 13 are sensors close to the sink node, which usually undertake some forwarding tasks; and the other nodes are the nodes farthest from the sink node, and usually rarely participate in task forwarding.  
TTCF first uses the STPCSE model to minimize the amount of physical data on the WBAN sensors, and then transmits the compressed data to the human body sink node. Generally, human sensors far away from the sink node have to use relay nodes for data transmission, so multiple transmission paths composed of different nodes may be formed between the source nodes and sink nodes. The purpose of TTCF is to select the optimal path nodes from these paths for data transmission and convergence.