## 4 Experimental Results and Discussion  
### Experimental Results  
Iperf [26] was used as the performance evaluation tool to obtain the bandwidth result of the backhaul WMN and the stations that make use of the WMN. To evaluate the performance of the embedded system implementation, a series of tests were performed and the results were compared as described below. IEEE 802.11g is used as the wireless technology of the physical layer (PHY) in all the tests done is. Because the IEEE 802.11s is the routing protocol that works on OSI layer 2, IEEE 802.11g is needed to handle the tasks on PHY layer or the OSI layer 1. The setup parameters are listed as follows:  
* Default transmission power:
* The wireless mesh interface: 24.5 mW
* The AP interface: 24 mW
* Channels used: Channels 6 and 11 of 802.11g  
The first three tests use static routing to test the multi-hop network performance because the distance is not long enough to do a practical test. The details of the three tests are given in the following:  
* Test 1: test the 1-hop backhaul WMN connection as shown in Figure 3.
* Test 2: two mobile stations running non-FreeBSD OS were connected to the same backhaul WMN at each end through the same channel, as shown in Figure 4.
* Test 3: similar to test 2 but it will be using two non-overlapping channels instead of the same channel for the backhaul and the station connection as shown in Figure 4.  
Figure 4: The 2 mobile stations that are connected to each other through the backhaul WMN. Figure 3: The 1-hop backhaul WMN connection (test 1). All of these tests were performed in an outdoor environment with interference coming from APs and stations within the test range. On average, approximately 30 APs were detected within the communication range of the embedded systems by utilizing the Linux scanning command _iwlist wlan0 scan_ on a laptop computer that is running Ubuntu 11.10. Given these conditions, a significant amount of interference exists and renders the result unstable. The last two tests were performed to show the path selected by the FreeBSD IEEE 802.11s implementation in the default mode or the dynamic routing mode instead of the static routing used in the previous tests. A simple mesh topology was used to evaluate the path selection mechanism of the 802.11s implementation as shown in Figure 5. The photos of the field test indicate the location of each MP and station (Figures  
In the first three tests, each range was evaluated with 8 trials, and an average value was calculated to ensure the consistency of the results because the tests were performed outdoors where a significant amount of interference exists. Each trial was run for 60 seconds with a 10-second interval as the input to the iperf. The sample bandwidth results are shown in Figures 9-11. The results were then tabulated and compared. Figure 8: Photo of the actual field test where **(left)** station 2/desktop and **(right)** MP3 are located. Figure 7: Photo of the actual field test where MP2 is located in between MP1 and MP3. The range value in the tables indicates the distance between MP1 and MP3 where MP2 will be located in the middle of the 2 MPs. For example, for the 15 m test, the MP2 will be located 7.5 m away from both MP1 and MP3. This placement will be applied to tests 2 and 3 as well. The results of tests 1, 2 and 3 are tabulated in Tables 1-3, respectively. Figure 11: Sample bandwidth results for the stations that were connected to the WMN through a different channel with the backhaul connection. Figure 10: Sample bandwidth results for the stations that were connected to the WMN through the same channel with the backhaul connection. Figure 4.0 Sample bandwidth results of the MP1-MP3 connection. \begin{table}
\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|} \hline \multirow{2}{*}{**Range**} & \multicolumn{8}{c|}{**Throughput (Mbps)**} \\ \cline{2-10}  & **Trial 1** & **Trial 2** & **Trial 3** & **Trial 4** & **Trial 5** & **Trial 6** & **Trial 7** & **Trial 8** & **Average** \\ \hline
**15 m** & 1.60 & 1.93 & 1.67 & 1.65 & 2.41 & 2.