Merge pull request #197 from pfaaj/master

Small changes to introductory text in SOLUTION ARCHITECTURE and typo correction

solution_architecture.md

@@ -29,7 +29,7 @@ We assume a close association of a mobile phone and its user and, thus, equate t
 
 ## INTRODUCTION
 
-To reduce the spread of [COVID-19](https://www.ecdc.europa.eu/en/covid-19-pandemic), it is necessary to inform people about their close proximity to positively tested individuals. So far, health departments and affected individuals identified these in personal dialogs based on the individuals' memory. This led to a high number of unknown connections, e.g. when using public transport. 
+To reduce the spread of [COVID-19](https://www.ecdc.europa.eu/en/covid-19-pandemic), it is necessary to inform people about their close proximity to positively tested individuals. So far, health departments and affected individuals have identified possibly infected individuals in personal conversations based on each individuals' memory. This has led to a high number of unknown connections, e.g. when using public transport. 
 
 ![Figure 1: High-level architecture overview](images/solution_architecture/figure_1.svg "Figure 1: High-level architecture overview")
 
@@ -250,7 +250,7 @@ For the operation of the back end, several bandwidth estimations need to be take
 
 ### Bandwidth Estimations
 
-While each set of 14 diagnosis keys only has the small size of 392 bytes, all newly submitted diagnosis keys of a time period need to be downloaded by all mobile phones having the application installed. When considering 2000 new cases for a day, a transmission overhead (through headers, handshakes, failed downloads, etc.) of 100% and 30 million clients, this adds up to approximately 1.5MB per client, i.e. **42.8TB** of overall traffic. If a day is split into 24 chucks (one per hour), this results in a total number of **720 million requests per day**. If the requests are evenly spread throughout the corresponding hour, approximately **8,500 session requests** per second need to be handled. Detailed descriptions of the connections can be found in the chapter ["Data transfer and data processing"](#data-transfer-and-data-processing). Those number exclude possible interoperability with other countries.
+While each set of 14 diagnosis keys only has the small size of 392 bytes, all newly submitted diagnosis keys of a time period need to be downloaded by all mobile phones having the application installed. When considering 2000 new cases for a day, a transmission overhead (through headers, handshakes, failed downloads, etc.) of 100% and 30 million clients, this adds up to approximately 1.5MB per client, i.e. **42.8TB** of overall traffic. If a day is split into 24 chunks (one per hour), this results in a total number of **720 million requests per day**. If the requests are evenly spread throughout the corresponding hour, approximately **8,500 session requests** per second need to be handled. Detailed descriptions of the connections can be found in the chapter ["Data transfer and data processing"](#data-transfer-and-data-processing). Those number exclude possible interoperability with other countries.
 
 If the back end calls from the mobile applications cannot be spread as evenly as we expect, we might experience peaks. To achieve an even spread (and to be able to handle a peak), we will employ a Content Delivery Network (CDN) by T-Systems to make the individual aggregated files available. According to an evaluation with T-Systems, the estimated throughput and request number can be handled by their infrastructure.