## 3 The Embedded System Implementation  
The embedded systems used in these tests are the PCEEngine ALIX 3d2 with a 4 GB Sandisk Ultra Compact Flash (CF) card as the storage medium for the OS and the software. Two Compex WLM54G23 wireless network cards that support the 802.11a/b/g on the physical layer and based on the Atheros AR 5414 chipset were added to the miniPCI slots in each of the embedded systems along with two Sub-Miniature version A (SMA) omni-directional antennas. The specifications of the PCEngline ALIX 3d2 are as follows [24]:  
* CPU: 500 MHz AMD Geode LX800
* DRAM: 256 MB DDR DRAM
* Storage: CompactFlash socket
* Power: DC jack or passive POE, min. 7 V to max. 20 V
* Three LED indicators
* Expansion: 2 miniPCI slots, LPC bus
* Connectivity: 1 Ethernet (Via VT6105M 10/100)  
Figure 1: 1-hop connection.  
* Input/Output:  DB9 serial port, dual USB
* Board size: \(100\times 160\) mm
* Firmware:  tinyBIOS  
A picture of the embedded system with two wireless network cards and an installed CF card is shown in Figure 2 below.  
NanoBSD was used to build the embedded version of the FreeBSD for this test bed implementation. Two configurations need to be created to build the FreeBSD image with NanoBSD, namely, the configuration of the FreeBSD kernel and NanoBSD. After the image building process, the image will be copied to the CF card. The embedded version of FreeBSD then runs on the embedded system in read-only mode.  
Some system files need to be modified after the OS has been copied to the CF card such that the embedded system boots with the wireless mesh interface and AP interface instead of the default station interface. Further configurations were added to the system files, such as the Internet Protocol (IP) address settings for each of the embedded systems and installation of the performance evaluation software in the embedded system; furthermore, the Dynamic Host Configuration Protocol (DHCP) was also configured so that the stations will be able to connect to the WMN with ease.  
In the system implementation, two wireless network cards were installed in each of the systems to distribute the network resources for different purposes. Two non-overlapping channels were used in the test: channel 11 for the backhaul connection and channel 6 for the stations to connect to the WMN. In this case, the wireless network cards will be initialized to work in the different mode and channel. The wireless mesh interface will be assigned to channel 11, and the AP interface will be assigned to channel 6. These two wireless network cards were then bridged together to communicate with each other.  
The WMN implementation of the FreeBSD can configure the topology automatically (default) or manually. To configure the topology of the WMN manually, the wireless local area network access control list (wlan_acl) had to be enabled during the NanoBSD image building phase or manually enabled with the help of a command [25].  
Figure 2: The (left photo) top view and (right photo) bottom view of the embedded system.  
Further explanations on how to configure the interfaces to work as the wireless mesh interfaces, the routing implementation of the IEEE 802.11s under FreeBSD and how to implement a routing protocol can be found in the paper by [PERSON] [9].