CWN's are a true phenomena of the 21st century and is now found in thousands of countries around the world. Although there are differences, between countries and groups most have common characteristics:
1) They are non-commercial entities established and maintained by groups of individuals.
2) They use wireless LAN to form a network that:
Spans across property boundaries and/or public spaces
Allow TCP/IP network devices and computers to communicate and share/stream data
3) They grow by:
Interconnecting smaller networks together to form larger networks and so overcome topographical boundaries.
Developing a group identity designed to focus efforts and facilitates cooperation between people of different backgrounds, skills and interests.
4) Their popularity has grown due to:
The relative low cost of wireless LAN equipment.
The ability of individuals to connect a network across property boundaries without need of a commercial carrier or special licence.
Public familiarity with wireless and networking/internet applications.
5) They use one or more combinations of network models:
WLAN – Wireless local area network
Mesh - Self organising adhoc wireless network
WAN – Wide Area Networks using wireless for user connections and backhaul
Hybrid – Any combination of the above including wire or fibre, in networks there are really no boundaries.
Line Of Sight (LOS), a motivator for shared networks
One of the major hurdles faced by many people setting up a wireless network over distance is the problem of establishing good LOS between two sites. Without LOS it is highly unlikely or impossible to establish a reliable network over a few hundred metres. This is because of the high frequency and low power used by most standard wireless LAN devices 802.11(a/b/g) has difficulty passing through a solid object without a significant reduction and dissipation of the signal.
With good LOS however, it is not uncommon to see links over 10kms sustained at relatively high data rates using low cost off-the-shelf equipment. But in the real world good LOS between different locations is often rare for an individual working on their own and this is the main reason many CWN groups have formed. By coordinating a group people who can share and combine their networks between those with good LOS and others without, they can overcome many of the topographical barriers that an individual would find difficult on their own.
To achieve the aim of building a large network and joining smaller networks together there becomes a need to develop some form of network management to allow significant numbers of nodes and users to be joined together. This is because a simple Layer 2 WLAN would not be effective and would soon congest, just as a basic wired LAN, as they do not have the ability to route or shape traffic if network congestion or failures occur.
As a result two main routing protocols have become predominantly used by CWN Groups. These are either self organizing routing systems, often termed Mesh using OLSR or Autonomous Systems similar to that used by the Internet typically BGP or in some cases OSPF.