Wireless Mesh Topology

A wireless network as described in this document is a network of wireless local area networks (LAN) connected together to form a metropolitan network (MAN), usually located in one geographical area, such as a city or small town. Several wireless interface standards currently exist, some operate within licensed and others within unlicensed spectrum, some point to point, others point to multi-point, and yet others more flexible. The most common readily available standard at the moment is the 802.11 family (802.11, 802.11a, 802.11b and 802.11g]). This is consumer equipment that operates on an unlicensed radio frequency. Each wireless network is composed of various nodes connected together. A node is a collection of various PCs or other equipment connected together directly using the IP network and within direct radio range. A node consists of at least one router and one of more clients. The clients normally require little configuration and talk only to the router, whilst the router will route it’s own data and that of its clients to the rest of the network. It will also participate in exchange routing information with other nodes to ensure it always knows how to reach the rest of the network. The nodes can be connected together by radio links or by other means. The term node can loosely be associated with the router/host which manages each node’s own local network. Due to the limited range of the radio signals a large number of nodes will be required to provide coverage to a whole town, thus requiring a complex mesh of connections between the nodes to provide a robust network.
The network’s clients, the people who connect to the nodes from their home or office, make up the complete network. The nodes without clients form each group’s network infrastructure.

Wireless Mesh Topology

A wireless mesh network is made up of three or more wireless access points, working in harmony with each other while sharing each other routing protocols, in a collection of cross-connect links to create an interconnected electronic pathway for the transmission between two or more computers. When a wireless mesh is form it creates a single name identifier for access and the signals between wireless access points are used with each other to clearly distinguishable from another network. The organization of sharing access points working in harmony is known as the mesh topology. The defined mesh topology of a given area defined by the access points is known as mesh cloud. Access to this mesh cloud is dependent on the network created by the access points.

There are three types of mesh networks:

	Fixed wireless installations that connect multiple locations using Ad-hoc mode,
	Mobile, peer-to-peer, ad-hoc networks that have variable availability and a potentially ever changing set of nodes and finally
	Node-to-node infrastructure network that connect multiple locations and combine with mobile giving the best of the both world.

Fixed mesh networks are generally built with the expectation that many nodes have no direct backhaul, network, or Internet access. In fact, if each location had some kind of enterprise or Internet access, distributing service by wireless would be almost unnecessary.

In a fixed installation, locations for nodes are chosen with an eye for providing the right overall level of bandwidth with the fewest points. Fixed mesh networks also can effectively offer non-line-of-sight service by ringing an obstacle -- a tall building, a hill, a cluster of trees, an area of known interference -- with enough nodes to bypass it. These fixed networks are typically directional enough over each link to avoid major security risks.

In contrast, peer-to-peer mobile mesh networks -- which are a long way from actual deployment -- rely on individual devices connecting to each other through devices within radio range. Scalability can be an issue because each device has to manage known optimal paths, which can change from millisecond to millisecond. When an uplink of some kind is added via cell, satellite, or wire, the network becomes dynamically aware and can handle queued interactions.

Node-to-node network utilizes a fixed mesh network with mobile mesh network in an infrastructure mode. Node-to-node connects each node using infrastructure mode and it provides a network cloud that none-nodes or clients using 802.11b or g can roam in the network. It is has the benefits of both mobile mesh and fixed installations. Clients have the ability to roam the network similar to roaming a cellular network.

Roaming in Node-to-node

There are two methods of roaming in a node-to-node configuration: Patchwork roaming and Mobile Mesh roaming.

Nodes in a mobile mesh by their very nature roam in and out of coverage and between networks.

With Patchwork roaming, wireless connection between client’s hardware and mesh network, a wireless data networks, public Wi-Fi hotspots, and enterprise WLAN’s, are difficult to operate at best. The clients using Ipv4 that do not automatically change the IP address when moving between mesh nodes and wireless nodes. Manual intervention may be required. With Patchwork seamless roaming can be achieve; however, it requires DHCP to set every few seconds. The solution will be wait until Ipv6.

Mobile meshes implements self-contained dynamic addressing and rendezvous technologies to simplify address management and enable true nomadic operation without reliance on external clients hardware. Mobile devices can join and leave a mobile mesh and/or connect to public or private fixed infrastructure, all while retaining connectivity to critical services.

Wireless Mesh topology every node has a connection to every other node in the network realm. There is two types of mesh topologies: full mesh and partial mesh.

Full wireless mesh topology occurs when every node in a realm is connected to every other node in a network. Full mesh is yields the greatest amount of redundancy, so in the event that one of those nodes fails, network traffic can be directed to any of the other nodes. Full wireless mesh is difficult to achieve on a large scale using MeshAP; however, small-scale area like offices or small campus may be ideal. One should note that it is difficult to deploy a full mesh topology.

Partial mesh topology yields less redundancy than full mesh topology. With partial mesh, some nodes are organized in a full mesh scheme but others are only connected to one or more nodes in the network realm. Partial mesh topology is commonly found in either small or large networks or fulfilling the last mile connection to a full meshed backbone.

There are 4 main types of partial wireless mesh nodes topologies:

1. Point-to-point
2. Point-to-multipoint or Multipoint-to-point, and
3. Multipoint-to-multipoint,
4. Metropolitan

Point-to-point and point-to-multipoint networks have long been the standard for fixed wireless deployments and some 802.11 based networks. In testing of mesh networks have proven to be most versatile, overcoming a number of disadvantages in traditional wireless topologies. This section will detail the fundamentals of MeshAP and its inherent advantages.

Point-to-Point nodes topology

A point-to-point network is the simplest form of wireless network, composed of two radio and two high gain antennas in direct communication with each other. Point to point links are often used to provide high-performance, dedicated connections or high-speed interconnect links. These links are quick to deploy individually, but do not easily scale to create a large network. Client used these nodes in a site-to-site configuration.

Point to Multipoint nodes topology

A point-to multipoint or a Multipoint to point nodes share link between an uplink node with omni directional antenna and repeater nodes or downlink nodes with high gain directional antennas. This type of network is easier to deploy than Point to point network because adding a new subscriber only requires equipment deployment at the subscriber site, not at the uplink node; however, each remote site must be within range and clear line of sight of the base station. Trees, hills and other line of sight obstruction make point to multipoint nods impractical for residential and home office coverage. A Point to Multipoint network is suited for either backhaul operations or customers that need reliable, high-speed connections, but are not willing to pay for dedicated capacity that may go unused. The nodes performed as a bridge to the uplink network and are generally in wired configuration for the clients. The problem with point to Multipoint node topology is that they are not design to mesh with other nodes due to the directional antenna.

Multipoint nodes topology

Multipoint to multipoint networks creates a routed mesh topology that mirrors the structure of a wired Internet. To build a mesh network, indoor or outdoor Internet access is first established with the deployment of an access switch connected to a wired ISP. Additional access routers are then deployed throughout the coverage area until a maximum density is achieved. Each access router not only provides access for attached users, but also become part of the network infrastructure by routing traffic through the network over multiple hops. This allows any client to join the network at any point of the mesh, even if the clients are not using a node. Client can access the entire mesh wireless or wired making this the best choice to deploy for areas that require larger coverage MeshAP.

Metropolitan nodes topology

Metropolitan node topology uses the two mesh type networks. They are Backhaul and Last Mile.

Backhaul are either a Point-to-Point or Point-to-Multipoint topology. It design is to provide a backbone to the uplink nodes (see MeshAP configuration.) The nodes use dual antennas one being directional to the uplink the other providing connection to the last mile. The last mile antenna tends to be omni directional. Backhaul Wiana configuration uses two different realms, channels, and ESSID. Clients do not use the backhaul as an access point. The prime mission is to bring bandwidth to different part of the last mile. The uplink nodes in backhaul provide multi redundant connections to the wired Internet and have more capacity than 11 MBPS. Depending on the size of the area cover numerous backhaul points maybe required to cover a large city.

Last Mile is a Multipoint-to-Multipoint topology is nodes that have single radio cards with omni antennas and are linked to the backhauls omni antenna. The difference between Last Mile and Multipoint-to-Multipoint topology is that Internet connection does not come from a wired router but through the backhaul mesh via a central point.

These are just a few examples of the type of topology that a LocustWorld MeshAP can configure. The complexity increases when adding a second wireless radio card to a node and adding different types of antennas.

Mixed node topology

A mixed node network is the complex form of wireless network, composed of two radio and two high gain antennas in direct communication with each other and a third party wireless bridge/repeater. Mixed Nodes are often used to provide high-performance, dedicated connections or high-speed interconnect links. These links are quick to deploy individually, but do not easily scale to create a large network. Client used these bridge/repeater nodes in an indoor environment. The main benefit is that the indoor unit is a low cost commercial product.

Mixed Node Indoor topology

Similar to a mixed node network is the complex form of wireless network, composed of two radio and two high gain antennas in direct communication with each other and a series of third party wireless bridge/repeater. Mixed Nodes are often used to provide high-performance, dedicated connections or high-speed interconnect links. These links are quick to deploy individually, although they do not easily scale to create a large outdoor network they do scale to become a large indoor network. Client used these bridge/repeater nodes in an indoor environment. The main benefit is that the indoor unit is a low cost commercial product.

Mesh Structure

Rectangular Mesh Structure

The rectangular mesh structure, is the original topology proposed for a digital wave guide mesh. The main problem with this structure is the direction-dependent dispersion, which increases with frequency.

Triangle Mesh

Alternative sampling lattices have been studied to obtain more uniform wave propagation characteristics in all directions. When the sampling of the surface is hexagonal, the triangular digital wave guide mesh is obtained. This structure has better dispersion characteristics than the rectangular mesh. The same dispersion analysis as presented for the rectangular mesh is valid for the triangular mesh.