Wireless Network Topology choices for Wireless Metropolitan Area Networks (Wi-MAN)
Wireless Point to Point
Wireless Networks with just two end points are considered Point to Point (P2P, PTP, Point-to-Point) networks. Sometimes this implies a technology or specific product that is only capable of operation between two end points. Point to Point connections generally do not share bandwidth or spectrum with other devices, which gives high dedicated bandwidths between the nodes. Some wireless technologies such as Microwave Millimeter Wave (MMW) and Free Space Optics (FSO) are only capable of operating in Point to Point wireless network topology.
Wireless Point to Multipoint
A Wireless Network with one central node and multiple remote nodes is termed a Point to Multipoint (P2MP, PTMP, Point-to-Multipoint) Network. Typically the central node is described as a Base Station (BS) and the remote ends are termed Subscriber Units (SU) or Customer Premise Equipment (CPE) devices. Point to Multipoint Wireless Networks are popular for Wireless ISP, CCTV and other applications where low costs of end-user nodes are desired. Technologies popular in Point to Multipoint include MIMO OFDM Radios
Wireless Star Topology
A star topology creates a network by arranging 2 or more host machines around a central hub. A variation of this topology, the ‘star ring’ topology, is in common use today. The star topology is still regarded as one of the major network topologies of the networking world. A star topology is typically used in a broadcast or SIMO network, where a single information source communicates directly with multiple clients. An example of this is a radio station, where a single antenna transmits data directly to many radios. If there are ‘n’ number of nodes in a star topology connection the connecting lines between the nodes should be ‘n-1’
Wireless Tree Topology
A tree topology is so named because it resembles a binary tree structure from computer science. The tree has a “root” node, which forms the base of the network. The root node then communicates with a number of smaller nodes, and those in turn communicate with an even greater number of smaller nodes.
Wireless Ring Topology
A ring topology creates a network by arranging 2 or more hosts in a circle. Data is passed between hosts around the network. If a host desires to send data to another host, it will attach that data as well as a piece of data saying who the message is for as it passes by. The other host will then see that message for it by scanning for destination MAC addresses that match its own. If the MAC addresses do match, the host will take the data and the message will be delivered. A variation of this topology, the ‘star ring’ topology, is in common use today.
Wireless Mesh Network
Mesh topology – A Wireless Mesh topology creates a network by ensuring that wireless devices are connected to more than one other devices on the Wireless Network. This topology’s purpose is for fault tolerance and also to enable mobility- as opposed to other wireless topologies such as P2P or P2MP, where the entire LAN will go down if one central node or unit fails. In a Wireless Mesh topology, as long as two nodes with a working connection are still functioning, a Wireless Network will still exist. The Wireless Mesh Topology is still regarded as one of the major network topologies of the wireless networking industry.
Wireless Line Topology
Line topology – This topology works by connecting wireless devices to the host located adjacent to it. Wireless units are then connected back-to-back at the nodes to create a linear network of points. Disadvantages of this topology are lack of fault tolerance and resilience, and shared bandwidth. Line Topology may be necessary if there is no Line of Sight between the end points, or to extend distances beyond that capable in a single “hop”
Wireless Tree Topology
‘Tree topology’ – A tree topology, similar to a line topology in that it is extremely rare and is generally not regarded as one of the main network topologies, forms a network by arranging hosts in a hierarchal fashion. A host that is a branch off from the main tree is called a ‘leaf.’ This topology in this respect becomes very similar to a partial mesh topology – if a ‘leaf’ fails, its connection is isolated and the rest of the LAN can continue onwards.
Bus topology – A bus topology creates a network by connecting 2 or more hosts to a common backbone infrastructure. This topology is not used in Wireless Networks, as it is typically physically considered in wired networks using coaxial cables.
Wireless Hybrid Topologies
Hybrid topology – A hybrid topology, which is what most networks implement today, uses a combination of multiple basic network topologies, usually by functioning as one topology logically while appearing as another physically. The most common hybrid topologies include Mesh Star, Mesh Ring, and Star Ring.
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