Wireless Network Topology

Posted By: technopediasite



Introduction to Wireless Topology

Wireless topologies are essentially identical to the same traditional cabled network topologies.Only the transmission media is different. Keep in mind that applications can fall under more than one of the following topologies (a peer-to-peer network also can be described as a mesh),but the distinctions of each topology determine how a network is classified.

Point-to-Point (PTP) Topology

PTP topology is the basic building block for all topologies. It consists of one direct

connection between two points. This can be for a two node peer-to-peer network, a wireless

connection to a printer or other peripheral, or a link between buildings.

For most applications, communications is bidirectional, although unidirectional may be

required in certain solutions. While the primary purpose for a PTP connection is a backbone

link between two nodes, it also can be designed for distribution purposes.

Point-to-Multipoint Topology

The point-to-multipoint topology consists of a central hub for distribution of data. This is

useful in an environment where a central repository is maintained to insure data integrity.This could be an admissions department that holds all student records or a city hall acting as the hub for other municipal buildings and departments.

Multiple Point-to-Point (PTP) Topology

The multiple PTP topology is a collection of PTP connections in series. This topology could

be utilized to extend beyond distance limitations of the wireless transceiver hardware,

eliminate or avoid obstructions (natural or man-made), or overcome the curvature of the

Earth, where LOS is a requirement of the hardware.

User-to-User Topology

A peer-to-peer network topology also is called user to user. This methodology is used as an ad hoc small network application and for Bluetooth® technology (piconet/scatternet). It allows for file and peripheral sharing in a limited geographic area, on one floor or within one

building. Every device must have its own antenna and internal wireless operating software

(as compared with an AP connected to a hub for server connectivity).

Mesh Topology

Mesh topology, like its cabled counterpart, is a conglomerate of wireless connections of single or multiple topologies. It can be used for large geographic coverage and utilizes multiple links for redundancy. It is a wireless version similar to the cabled Internet.

The mesh topology can be implemented in a limited area, such as a department, floor, or

building, or a larger application such as a MAN. Mesh installations can take advantage of the same or different hardware technologies, as long as the protocols are the same or a gateway is implemented. The cells of a cellular telephone system are an application of the mesh topology.

Implementation of Wireless Topologies

Implementation of wireless topologies requires many of the same procedures as a cabled

network and some that are unique to the wireless environment.

Point-to-Point (PTP) Topology

Implementation of a PTP connection can be as easy as plugging in two APs at opposite sides of a building to link independent LANs or as complex as measuring and tracking atmospheric conditions between buildings miles apart.

LOS first must be established. A check then must be made for other wireless communications in the pathway that could cause interference. If there are any obstructions or other communications that could be a problem, another design may need to be engineered. Once all of these problems are eliminated, the hardware can be installed.

For devices such as Yagi antennas, they must be pointed at each other and tested for signal

strength. Many antenna transceivers have built in diagnostic applications that assist in the

pointing and testing of the antenna. Radio wave signal strength testers also can be utilized.

Most Yagi antennas allow for a specified angle or range to achieve communications (i.e., 15

or 30 degrees). The signal will shoot in a strait path with a width equal to the degree of angle allowed.

When the connection is established, the network link can be brought up and monitored for

performance. If there is an abundance of collisions or dropped packets, the antenna may need to be moved or aimed.

Point-to-point topology—metropolitan area network

Point-to-Multipoint Topology

Implementation of a point-to-multipoint topology requires the installation of an omnidirectional antenna at the central distribution node or hub of the network.These antennas generally are shaped like a spike or rod and allow for the connecting

nodes to merely require being pointed in their direction. Again, the antenna must be focused

for best signal strength.

Like PTP, LOS is required, other signals in the area may cause interference, and environmental conditions may cause degradation of signal strength.

Multiple Point-to-Point (PTP) Topology

A multiple PTP topology is a series of single PTP links. Utilized to extend

distances or to avoid obstructions, each link of the multiple PTP installation must adhere to

the requirements of a single PTP connection.

When implementing, each link first must be tested individually to insure connectivity,

followed by a test of the entire link to test for throughput.

User-to-User Topology

User-to-user, or peer-to-peer, topologies are implemented in confined areas. Obstructions such as walls and floors can be identified easily. Once the hardware and software are implemented, it is not difficult to test for signal strength and connectivity.

Because of the wide range of electronic devices available and used in the SOHO environment, interference may be an issue. Wireless telephones, cellular telephones, wireless security systems, and other electronic devices may cause problems for communications. If interference causes slow communications or dropped connections, other devices may have to be eliminated individually to identify the source of problems.

Mesh Topology

Implementation of a mesh network involves all of the previously mentioned procedures and

adds requirements based on the protocols being utilized. Because multiple pathways may exist between nodes, problems may exist but may never be identified. If a link is causing a bottleneck, the applications may avoid the slow path in favor of a faster one.Like multiple PTP, each link should be fully tested and monitored upon implementation to

avoid the likelihood of errors and throughput issues.