Wireless Mesh
Wireless Mesh Networking Concepts
Single, Dual, and Multi Radio Meshes
There are three basic design concepts attributed to wireless mesh networking.
Single Radio Mesh
Single radio mesh networks are the very basic and worst design possible in mesh networking. The concept is that all AP traffic is shared by the wireless clients and backhaul on one radio on one single channel.
The result is that as more AP's are added the more traffic is dedicated to the backhaul and less bandwidth is available for the clients resulting in very poor speeds. Coupled with the fact that the AP cannot send and recieve at the same time results in in a huge degradation in service and unpredictable latency. Single radio meshes do not scale to large networks.
Dual Radio Mesh
In a dual radio mesh, one radio is designed for client access while the second radio deals with the backhaul traffic. This solution provides many advantages over single radio mesh networks, however the throuput problems still exists in dual radio meshes as the backhaul radio deals with inbound and outbound traffic with the end result being bottlenecked backhaul traffic.
Multi Radio Mesh or Structured Mesh
Multi radio mesh networks are by far the most advanced and scaleable type of mesh networks. These type of mesh networks consist of at least three radio mesh nodes. One or more radios deal with wireless clients and 2 or more radios dedicated for backhaul and forwardhaul. The result is that you have a scalable and high throughput mesh.
Mesh Routing Protocols
Wireless mesh protocols can be diveded in to two basic types (hybrids of these two types will be discussed later) - Pro-active and Reactive protocols. Both types have certain advantages and disadvantages.
Proactive Protocols
Proactive routing protocols are link state protocols such as OLSR (optimized link state routing) and operate as table driven protocols. Whereas each node in the mesh network maintains routing information of every other node in the network. This routing information is updated dynamically and broadcasts this information to every node at regular intervals to maintain the correct routing information. Proactive protocols provide high mobility in mesh networks with the tradeoff of higher overhead as the nodes need to update themselves frequently.
Reactive Protocols
Reactive protocols such as AODV (AD-Hoc On Demand Distance Vector) establish route destinations only on demand. It is capable of unicast and multicast routing. Since reactive protocols only find routes on demand they have a very low overhead but less mobility than proactive protocols.
So to sum up if you are in an office and you only move say from your desk to the board room and use your laptop in one place for extended periods of time then reactive protocols like AODV would suit that situation best. However if you need to rely on high mobility applications such as vowifi or some other scenario requiring a mobile mesh, then a proactive protocol such as olsr is your best bet.
Wireless Mesh Backhaul
By implementing olsr in star-os you can create a fully redundant wireless mesh backhaul. The basic concept is that if each backhaul node can see at least two other nodes in the network no single point of failure can bring down the entire network. The more backhaul nodes the more reliable the network becomes.
More to come real soon.....