WirelessMesh

What is a Free Wireless Mesh

A large collection of wireless routers that talk to each other through the open spectrum (de-licensed) providing a backbone. And each router in turn connects to a local area network. A mesh can be as large as an entire city or a small campus. If you want to read more about it, get this book and start reading.

A wireless mesh is a group of wireless devices that talk to each other in the Ad-Hoc mode. When they additionaly use the OLSR protocol, they form the OLSR mesh.

What do we need to setup a wireless mesh

Wllingness to share a pinch of what you have, apart from the following.

Hardware

Linksys WRT54GS V.4 Wireless Routers. This is used since we can add [freifunk firmware]http://wiki.freifunk.net/Freifunk_Firmware_%28English%29. Freifunk site also lists few other routers. You can use any of them. Of course it is possible to create a wireless mesh using any PC with a WLAN card.

Software

First of course is the recent firmware from Freifunk website. After setting up and with a working network you can later add other additional software available from the same site.

This firmware contains a tiny but sufficiently equipped Linux kernel, busybox userland tools, ssh, iptables and a package manager called ipkg.

An additional package called 'freifunk-dnsmasq' has to be added to the Friefunk firmware in order to allow DHCP IP allocation for WLAN users. It has to be added in the way as explained below.

Basic Mesh Setup

Before we go into the setup, there are some concepts about this mesh that need to be understood.

All the wireless devices whether OLSR or non-OLSR, communicate with each other in the Ad-Hoc mode. They must use the came channel. There are 3 main IP settings to be carried out for every node in the mesh. LAN, WLAN and OLSR (HNA4). The OLSR refers to a network and is not an individual address. It is a reflection of the LAN subnet.

The LAN for each mesh node should belong to a seperate subnet. LANs of different nodes talk to each other using the mesh routing.

The OLSR setting is in the format X/n where 'X' is the network ID of the LAN and 'n' is the subnet mask. Eg. 192.168.3.0/24

WLAN is the interface that actually communicates with other nodes in the mesh as well as the non-OLSR users who are logged in through their wireless interfaces. WLAN IP should be kept static and all the WLANs should exist on the same subnet as they directly link to each other. The 'freifunk-dnsmasq' package adds a facility to allocate DHCP IPs to the WLAN interface in order to allow wireless laptop users to use the mesh.

In the setup at HBCSE in Mahkhurd Mumbai, we used 2 Linksys routers to form an OLSR mesh. We called them Node1 and Node2.

The settings for each is given below.

Node1

LAN:

    IP   10.10.3.1
    Mask 255.255.255.0
    DHCP start IP 10.10.3.10
    Users 250

OLSR:

     10.10.3.0/24

WLAN:

    Mode Ad-Hoc
    IP  10.10.0.2
    Mask 255.255.0.0
    Channel 1

NAT: Enabled

Firewall: Enabled

ESSID: gnower-mesh

Hostname: gnower-node1

Node2

LAN:

    IP   192.168.2.1
    Mask 255.255.255.0
    DHCP start IP 192.168.2.5
    Users 250

OLSR:

         192.168.2.0/24

WLAN:

    Mode Ad-Hoc
    IP  192.168.0.1
    Mask 255.255.255.0
    Channel 1

NAT: Enabled

Firewall: Enabled

ESSID: gnower-mesh

Hostname: gnower-node2