## 3 System Model
### WBAN Blockchain System Performance Analysis  
In this section, we carried out several tests to validate the performance of the proposed blockchain-enabled WBAN platform in terms of the block size (number of the transaction), read throughput, transaction throughput, read latency, and transaction latency. We used Hyperledger Caliper, an open-source simulation tool used to investigate the performance of blockchain applications [59]. In order to evaluate the system performance of the blockchain network, we predefined some experimental parameters, i.e., one orderer and four peer nodes. In the proposed blockchain-enabled WBAN platform, we computed the throughput by changing the tps send rate from 200 tps to 1300 tps. The throughput could be broken down into two groups, such as transaction throughput and read throughput. The transaction throughput was defined as the number of  
Figure 11: Throughput with different node density. Figure 10: Average energy consumption with different node density. **(a)** Simulation time = 300 s; **(b)** simulation time = 1000 s.  
transactions triggered in the blockchain network within the assigned time slot, which is also presented in Equation (6). Likewise, the read-through was used to measure the reads operation in the blockchain network within the allocated time slot, as mentioned in Equation (7). The transaction read throughput was measured by varying the tps send rate by 500 to 3000 tps as shown in Figure 12 with random machine utilization configuration. The maximum throughput achieved was 2250 tps with a send rate of 2500 tps. For committing a transaction, the maximum transaction throughput was 1100 tps with a send rate of 1100 tps whereas the lowest one was 205 tps at 200 send rate, also shown in Figure 13.  
\[Transaction\ Throughput=\frac{Total\ committed\ transaction}{Time(sec)} \tag{6}\]  
\[Read\ Transaction\ Throughput=\frac{Total\ read\ operation}{Time(sec)} \tag{7}\]  
Figure 12: Read transaction throughput. Figure 13: Transaction throughput. Figures 14 and 15, show the transaction and read latency for the proposed blockchain-enabled WBAN platform. The term network latency is referred to as the time for a transaction to be executed in the blockchain network. In the proposed system we computed the network latency based on transaction latency and read latency as presented in Equations (8) and (9), respectively. The transaction latency was the amount of time taken by the transaction to be executed across the blockchain network. The time in transaction latency also included transaction submission, broadcast, and transaction consensus mechanism time. Similarly, read latency was measured by considering the round-trip time (RTT) for a transaction to be submitted until its first response. [PERSON] et al. [60] discuss the network threshold as the network percentile time required to execute the transaction in the network. \[\mathit{Transaction\ Latency}=(\mathit{Transaction\ execution\ time}*\mathit{Network\ threshold\ time})-\mathit{Transaction\ invoke\ time} \tag{8}\]  
\[\mathit{Read\ Latency}=(\mathit{Transaction\ RTT}-\mathit{Transaction\ invoke\ time}) \tag{9}\]  
Figure 14 shows the average transaction latency in which the linear rise in the transaction latency occurs as the user request increase in the network. It can be observed from the graph that the transaction latency started rising after 1100 tps send rate, which was considered as the optimal send rate. Similarly, the average read latency was computed by changing the send rate from 500 to 3000 tps using different machine resources. It can be observed from Figure 15 that the network read latency increased relatively less with the rise of send rate as compared to transaction latency. Nevertheless, the read latency significantly increased after the optimal send rate of 2500 tps. Endorser peers endorsed the transaction when it was proposed. The endorser peer function was executed when the specific chaincode was triggered and endorsed the transaction before it was committed.