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In rural Africa the penetration of telecommunication services, for example telephony and internet access, is low and in some regions non-existent. The telecommunication operators in Africa consider rural Africa as uneconomical due to the nature of these regions - remote, often inaccessible, lacking in infrastructure, sparsely populated, low income households and people with low skills levels. Yet, reliable, affordable and easy access to telecommunication services for all has been identified as key to social and economic development in Africa.

Self-provisioning and community ownership of low cost, distributed infrastructure is becoming a viable alternative to increase the penetration of telecommunication services in rural Africa. The recent emergence of wireless mesh network technology (based on IEEE 802.11 a/b/g standards) can help to improve the delivery of telecommunication services in these regions.

The network design for a wireless mesh network will depend on the geographic landscape and distances between the points to be connected. A combination of point-to-point long distance links
(using directional antennas) and local point-to-multipoint links (using omni-directional antennas)
between mesh nodes can create a reliable mesh network.

In rural Africa a satellite link (VSAT) often provides the only possible way to connect a local mesh network to an upstream network provider offering global connectivity. Satellite links suffer from higher than normal latency and affect latency sensitive services such as telephony.

A number of pilot mesh projects across the world (Freifunk OLSR Experiment in Berlin, Germany, the Dharamsala mesh in India and Peebles Valley in South Africa) have demonstrated that a community can establish and maintain a wireless mesh network and have access to a range of modern information and communication services. These services include telephony (Voice over Internet Protocol), instant messaging, electronic mail, web access, multimedia services and service delivery (e.g. telehealth and e-learning).

A wireless mesh network (WMN) consists of mesh nodes that form the backbone of the network. The nodes are able to configure automatically and re-configure dynamically to maintain the mesh connectivity. This gives the mesh its “self-forming” and “self-healing” characteristics. This self-sufficient relationship between the mesh nodes removes the need for centralized management. Intelligent routing allow mesh nodes to route data packets for nodes that may not be within direct wireless range of each other. Thus information can be routed from source to destination over multiple hops. This has a potential advantage in terms of network reliability over traditional single hop networks, especially for backhaul communication.

A wireless mesh node consists of a wireless router and an antenna. The mesh node could
be installed indoors or in a weather-proof enclosure outdoors. The antenna could be the standard indoor omni-directional antenna or it could be an externally mounted omni-
directional or directional antenna. A mesh node communicates only with other wireless
mesh nodes.

A wireless access point consists of a wireless router and an antenna. The wireless access point could be installed indoors or in a weather-proof enclosure outdoors. The antenna could be the standard indoor omni-directional antenna or it could be an externally mounted omni-directional antenna. A wireless access point creates a hotspot where any Wi-Fi enabled device can connect to the wireless access point.

2.4 Advantages of Mesh Networking

Self-forming The wireless mesh network forms automatically once the mesh nodes have been configured and activated.

Fault tolerance If redundant routes exist in the network, information flow is not interrupted in the rest of the network when one node fails. The network will dynamically reroute the information via the next available route.

Self-healing Once restored, a node rejoins the mesh network seamlessly.

Community ownership Ownership of the network is shared, hence the burden of network support does not rest with a single person.

Low cost of infrastructure Mesh nodes can be built from low cost, common-off-the- shelf equipment.

Ease of deployment With little training members of a community can build their
own nodes, configure and deploy them in the community.

● Communication between mesh nodes are based on Wi-Fi radios (IEEE 802.11 a/b/g)
attached to directional or omni-directional antennas.

● All radios are set to ad-hoc mode (not client mode or infrastructure (access point) mode).

● Each node in the WMN has the same ESSID (name) and BSSID (number) - the BSSID
should be fixed to prevent partitioning of the wireless network.

● In an ideal WMN, each node should be able to “see” at least two other nodes in the WMN. This allows full fail-over in case any node goes out of commission (e.g. due to a hardware failure or power failure).

● A mesh routing protocol, like OLSR, will route IP traffic between the wireless interfaces of the mesh nodes. It learns the potential routes by listening to the routing information exchanged in the network and maintains routing tables dynamically. This feature provides routing fault-tolerance by providing an alternative route when a node fails, if one is available.

● No non-mesh wireless device connects directly to a wireless mesh node (mesh nodes provide a wireless back-bone). This infrastructure is considered critical infrastructure and should be managed for the highest availability as the rest of the network depends on the availability of each node. The login on the mesh nodes should only be available to the technical team and not to all users of the mesh network.

● Each IP address in the mesh network should be unique to allow any computer in the network to connect to any other computer in the network.

● A computer can connect to the mesh network via LAN cables connected to the mesh node
or via a wireless connection to a separate access point (hotspot) connected to the LAN side
of a mesh node.

● One or more mesh nodes may be connected to a specially prepared node linking into a distant network. This node may also be a mesh node, but will not be configured the same
as the local mesh nodes.

Cost of planning versus the cost
of support

There is a trade-off between the cost of planning and
building of a network well at the start of the project and the cost of maintaining a badly designed network. It is worth the effort to plan thoroughly, get the appropriate equipment and to create redundant routes in the wireless mesh network wherever possible.

Telecommunications
Regulations

Each country has a regulatory body that regulates the use
of wireless equipment. Check with your local regulator
(see Appendix B) for any specific regulations regarding Wi-Fi equipment, the use of the 2.4 GHz and 5.8 GHz bands, and maximum power output for wireless equipment.

Wi-Fi is a line-of-sight
technology

Various obstructions may interfere with the signals and
should be considered:

● Trees and plants – water on leaves negatively impact on signal strength

● Construction materials – metal objects like roofs or reinforcing in concrete walls affect the signal strength.

Sources of interference Microwave ovens, air-conditioners and other radio
equipment could interfere with Wi-Fi equipment. It is best to avoid interference in order to secure a good link.

Lightning Electronics are susceptible to lightning damage and lightning protection should be considered, especially for outdoor installations of Wi-Fi equipment.

This section describes the hardware and software requirements for the wireless mesh network.

● Wireless routers: Linksys WRT54G (up to version 4.0) or Linksys WRT54GL (version 1.0 or
1.1). From WRT54G version 5.0 the flash memory has been reduced from 4MB to 2MB and
as a result the memory is no longer sufficient for the Freifunk firmware. The Linksys
WRT54GL is currently one of the most popular devices for wireless networking.

● PC or Laptop with a LAN card (to connect your PC/laptop to internet or office network)

● Freifunk firmware version 1.4.5
(download from http://download-master.berlin.freifunk.net/ipkg/_g%2bgl/ )

If the full names of the files are not fully displayed, move the mouse over each name/link and notice the bottom left corner of your screen for the full name of the file. All these files are the same except for the language (i.e. English, German, etc.) they have been built for. To download the English version, select openwrt-g-freifunk-1.4.5-en.bin. Note the
folder/directory to which this file is stored on your local machine.

● DD-WRT firmware version 2.3
(download from http://www.dd-wrt.com/dd-wrtv2/downloads.php )

Select “stable” → select “dd-wrt.v23 SP2” → select “standard” →
select “dd-wrt.v23_wrt54g.bin”

● Putty.exe
This is a Windows SSH client, required for any PC/laptop running Windows
(download from http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html or other website on the internet).

● Tcpdump
(download the latest tcpdump and libpcap library from
http://downloads.openwrt.org/whiterussian/packages/ )

Wireless mesh networks need careful planning. A wireless mesh network is fairly easy to build when you have a few local nodes to configure. However, networks tend to grow fairly quickly and can become a nightmare if not properly planned and managed from the start. The following steps can be used as a guideline to plan a wireless mesh network.

● Identify and plot the sites (houses/offices) that will receive a mesh node (Linksys): Usually one would get the GPS coordinates of these sites in order to plot them on Google Earth. The GPS coordinates can also be used when doing radio planning with specialized tools which can give a “digital terrain elevation model” of each link. As a minimum requirement one should have at least a schematic plot of the sites. The position of each node does not need to be very accurate, although the position of nodes relative to each other is helpful when assigning channels and IP addresses.

● Plan the wireless mesh network (radio links): The sites can now be linked together using the plot. Each link is defined as the straight line between two wireless nodes. The length of each link should reflect the distance between the sites. Many possible links exist with a mesh network – drawing all possible combinations is not necessary. Also draw the location
of the internet gateway site. The main aim of the plot is to get an overall picture of the network. The picture will give information on the network topology and number of hops
between sites and the internet gateway.

● Mesh: This is the simplest topology to configure in mesh networks. The sites are fairly uniformly distributed and every node can see every other node. If the area becomes too large, some sites might be too far away from the internet gateway and therefore needs to “hop” through many other mesh nodes before reaching the gateway. This will slow down their connection.

One solution would be to add
gateways   throughout    the    mesh
(also uniformly distributed across the mesh). The disadvantage is the
high    cost    associated    with    an
internet gateway. The preferable solution would therefore be to build a        so-called         backbone     reaching from the gateway throughout the mesh network.

Figure 2: Simple mesh network plot

If the gateway is in the middle, several backbones might be needed (e.g. star topology) to
ensure that everyone gets the same bandwidth. Figure 2 gives an example of a “simple”
mesh network plot requiring no backbone. Figure 3 gives an example of a “rectangular”
mesh network that would ideally require a backbone throughout the mesh network.

Clusters: Are there clusters formed in the network? How far are these clusters from each
other? If the clusters are too far from each other (taking into account whether one uses indoor/outdoor antennas, size of the outdoor antennas), one might need a backbone to connect the clusters together. The location of the internet gateway should also be considered. As with the mesh topology above, the backbone will connect the gateway(s) with all the clusters ensuring that everybody gets equal bandwidth. Figure 4 shows a plot of
a network with three clusters that are connected together with a backbone. Note that the gateway forms part of the backbone network to ensure faster connections to the internet.Clusters: Are there clusters formed in the network? How far are these clusters from each
other? If the clusters are too far from each other (taking into account whether one uses indoor/outdoor antennas, size of the outdoor antennas), one might need a backbone to connect the clusters together. The location of the internet gateway should also be considered. As with the mesh topology above, the backbone will connect the gateway(s) with all the clusters ensuring that everybody gets equal bandwidth. Figure 4 shows a plot of
a network with three clusters that are connected together with a backbone. Note that the gateway forms part of the backbone network to ensure faster connections to the internet.

Two types of nodes have already been identified in section 5.2; a “normal” mesh node and a backbone node. Channel allocation on the mesh node is usually a very simple exercise. One can choose between three channels (1, 6 or 11). When every node in the mesh is set to the same channel, they can “talk” to each other. When adding a backbone node, one will need another channel. Adding a backbone effectively adds another wireless network that has to work independent from the other mesh network. The “normal” mesh network will therefore work at channel 6 and the backbone at channel 11. This will ensure that the two networks do not interfere with each other. Less interference will result in better performance. In figure 4 one can therefore configure the mesh nodes in clusters A,
B, and C to use channel 6. The backbone nodes will be configured to use channel 11. In this context, we assume that the backbone node consists of two radios (or two Linksys
boxes): one will serve the backbone on frequency 11 and the other will serve the mesh
network on channel 6. The two radios (or Linksys boxes) are connected together back-to- back with a LAN cable.

In section 5.3, two channels were already allocated for the backbone and mesh network.
A third wireless network is possible within this framework; a hotspot. A hotspot is usually required at home or the office when one wants to create a local wireless network to connect laptops and other wireless equipment. The hotspot will require a wireless access point (Linksys) to be connected to the mesh node. The two Linksys boxes are connected together back-to-back with an LAN cable (via the Ethernet switch ports). The access point cannot use the same channel as the mesh or backbone nodes. This would cause interference and degrade the performance of the network. In our example where channels 6 and 11 are already used, the only option would be to assign channel 1 to the hotspot. On the access point the LAN and the wireless interfaces are bridged. The Linksys creating the hotspot has to have special firmware in order to easily configure the access point. We prefer to use the DD-WRT firmware.

Addresses are allocated according to RFC 1918 which provides details of the private address space. RFCs are found at http://www.ietf.org/rfc.html . The IP addressing scheme should ensure unique addresses for each node and PC on the network. The first thing one has to choose is an available subnet. RFC 1918 gives information on which private subnets are available. According to RFC 1918, the subnets available for private IP networks that will not be connected to the internet are:

Once the subnet has been selected, one can assign IP numbers to mesh nodes and PCs
randomly. We propose that one choose a method of assigning IP numbers and stick to it very rigorously. An example of a method of assigning IP numbers is shown in Figure 5. An example of an implementation of the method is shown in Figure 6.

● Start building the wireless mesh network by configuring all the mesh nodes and wireless access points in a central location according to the network design document. Mark each mesh node and wireless access point with the configuration details written on a piece of paper and stuck to the device. In this way the later configuration steps will be much easier.
It is also good practice to keep a log book with the configuration details and location of each node and to record the history of the node. See Appendix G for a form for the planning details required for a node, which can also be used as a log sheet for record keeping.

● While still at the same central location, test all equipment to ensure that everything is working correctly. Connect a PC to a mesh node with a LAN cable. Ensure that the PC will request an IP address by DHCP. Ping every other mesh node. If the ping is successful, then the mesh node attached to the PC and the other mesh nodes are working. If it is not successful, check the configurations.

● Start installing the mesh nodes from the gateway – the point where the internet will be connected to the mesh network. In this way you can confirm that the network is still working
as you install each new mesh node. Connect a PC to the mesh node with a LAN cable. Simply ping the gateway first, and if that is successful, ping any site on the internet to
ensure that the PC can access the internet.

10.0.0.0	-	10.255.255.255	(10/8 prefix)
172.16.0.0	-	172.31.255.255	(172.16/12 prefix)
192.168.0.0	-	192.168.255.255	(192.168/16 prefix)