## 4 Performance Analysis and Discussion
### Integrity Measurement  
In addition to the on-time performance of the platform, integrity is another key factor in aiding ATCOs to carry out ATC tasks. In particular, as our network is wireless, it might be possible for data loss in the atmosphere to occur during data transmission. Nevertheless, every bit of data is crucial to ATC decisions and situational awareness. Therefore, high integrity should be attained. With the same experimental setting in Section 4.1, each request is paired with a return value to indicate whether data loss during wireless transmission is minimised. The KPI adopted to measure integrity is the percentage of data loss during transmission %\({}_{loss}\), regardless of the cause of data loss.  
\[\%_{loss}=\sum_{i}^{N}\frac{Number\ of\ transmission\ loss}{Total\ number\ of\ transmission}\times 100\%. \tag{2}\]  
Ideally, it should be kept at 0% so that all the requests can be successfully transmitted to the server and the required data are returned to the client. The performance is regarded as satisfactory if %\({}_{loss}\) is below 10%. Nevertheless, it is more promising to achieve a %\({}_{loss}\) that is less than 5% and ideally less than 1%. The interval of the data output is measured and analysed for deducing %\({}_{loss}\). For instance, when the data request application is running at 1 Hz, the interval between two data should be maintained at the same rate (with minor tolerance for computational load) to demonstrate no data loss during transmission.  
Table 5 shows the evaluation results of integrity measurement. The results demonstrated an acceptable performance throughout all the experimental settings. Out of the 36 KPIs measured for different scenarios, three of them (8.33%) achieved less than 1% data loss, 22 of them (61.1%) achieved less than 5% data loss, and all of them (100%) achieved less than 10% data loss. The performance was convincing with more than 60% of the test scenarios that could benchmark performance having less than 5% data loss. It can be observed that the average data loss percentage for the 1 Hz frequency of request (2.42%) was lower than that for the 6 Hz frequency of request (4.85%). This is likely due to the huge number of requests and data flowing between the client and the server at the 6 Hz request frequency. During large instantaneous data flow, data loss in wireless media is possible and reasonable. Even the transmission of ADS-B data involves a large proportion of data loss. The original ADS-B transmission interval should be 0.5 s. Nonetheless, it is often seen to receive a data stream with double the interval. In the controlled experimental platform evaluation, the amount of data loss should be minimised as much as possible, and the criteria should be stricter than in the ADS-B transmission. With the reduced frequency of transmission, the network traffic load is alleviated. The alleviated workload can reduce transmission errors caused by the overwhelming flow of data. Therefore, it is reasonable to have a small percentage of data loss as it is difficult and unrealistic to reach ideal conditions. Hence, with the high integrity achieved, fewer information errors would  
disrupt the ATCOs' decision-making process. In short, the proposed platform is practical for real-world applications in shared situational awareness training.