# Insights from the Experimentation of Named Data Networks in Mobile Wireless Environments
## 4 Experimentation Setup and Results
### NDN Using Multiple Radio Wireless Interfaces  
A vehicular network presents a number of connectivity challenges that can be improved by adding extra points of contact across the city. Therefore, we decided to evaluate the behavior of the NDN using ITS-G5 and Wi-Fi simultaneously in ad-hoc mode. These tests were executed in a small-scale environment, following the same network elements used in the previous experiment (OBUs and RSUs), although without mobility. The goal was to evaluate the behavior of the NDN when two or more wireless communication technologies are available. In this evaluation there was the transmission of a single file, divided in several chunks, throughout the testbed. To further evaluate the impact of different application behaviors we explore two paradigms: pipelined and non-pipelined. In a pipelined scenario all chunks will be requested by the Consumer at once, virtually injecting a great mass of packets in the network in an effort to quickly retrieve the data. In a non-pipelined scenario the content chunks will be requested sequentially, with new chunks only being requested upon successful retrieval of the previous ones, hence guaranteeing a slower yet reliable delivery of the file requested. The test itself was performed by splitting the request of a 6 MB sized file through both wireless communication technologies, meaning that each will be in charge of retrieving half of the content chunks of the file (Figure 10). Furthermore, we considered both Unicast and Multicast communication methods to further enrich the study of the behavior of both technologies. In this scenario the performance of the NDN solution is assessed by measuring the number of packets transmitted (Interests) and received (Data), the number of timeouts, and the average delay per chunk which refers to the time between the creation of an Interest packet for a given chunk and the successful retrieval of its corresponding Data, taking into account all necessary retransmissions. We started our tests by transmitting the entire file using only one of the technologies to have a baseline when managing the use of two technologies simultaneously. Table 2 shows the results on distributing the 6 MB file (1403 chunks for MTU = 4470). Having established the performance benchmark for each technology, we split the file in half to be transmitted by one of the technologies so that we can assess the combined performance. Table 3 details the results obtained using the non-pipelined application for each technology. \begin{table}
\begin{tabular}{l l l l l l l l l} \hline \hline  & \multicolumn{4}{c}{**ITS-G5**} & \multicolumn{4}{c}{**Wi-Fi**} \\ \hline \multirow{2}{*}{**Multicast**} & **Time** & **OutInts** & **InData** & **TimedOuts** & **Time** & **OutInts** & **InData** & **TimedOuts** \\  & 94 s & 1412 & 1403 & 9 & 303 s & 1440 & 1403 & 37 \\  & & Average delay per chunk: 27.89 ms & & & & Average delay per chunk: 57.07 ms & \\ \hline \multirow{2}{*}{**Unicast**} & **Time** & **OutInts** & **InData** & **TimedOuts** & **Time** & **OutInts** & **InData** & **TimedOuts** \\  & 25 s & 1403 & 1403 & 0 & 82 s & 1403 & 1403 & 0 \\ \cline{1-1}  & & Average delay per chunk: 17.87 ms & & & & Average delay per chunk: 58.09 ms & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Non-pipelined results—full 6 MB file using ITS-G5 or Wi-Fi. Figure 10: NDN in multiple wireless interfaces—requesting a 6 MB file using both ITS-G5 and Wi-Fi. The summary of the results when both technologies are used simultaneously is shown in Table 4. Firstly, we can verify that using multicast brings about several delays in the delivery of the full sized file, no matter which technology is considered, in part due to the use of the shared wireless medium to forward data, which results in timeouts. Secondly, it is notable that using unicast methodology presents much better quality of results, both in terms of reliability and speed of content delivery, and allows us to conclude that ITS-G5 is much faster in delivering content as is to be expected.