Wireless MANs refer to a set of wireless data networks that provide wireless data access in a metropolitan area. The principal advantage of building wireless MANs for data access as opposed to establishing a wired network infrastructure is the cost of copper-wire or fiber optic cable, installation, and maintenance. In rural areas and developing countries where telephone lines and cable televisions are not in place, a wireless data access solution is more cost effective than a wired network solution. Depending on how wireless technologies are used in the infrastructure, wireless MANs can be categorized into the following types:
• Wireless “ last mile ” (fixed broadband wireless access),
• Wireless data access for mobile terminals,
• Wireless backbones or wireless mesh.
The first type is still based on a wired network infrastructure; that is, base stations connect directly to a backend wired network. PTM wireless communication replaces wired network communication between a base station and the end-user’s computer, the so-called “ last mile. ” Telephone-line-based last-mile access allows dial-up data access and ADSL (with necessary modems), whereas cable-television-based last-mile access permits higher bandwidths and an always-on connection. Dedicated T1 is commonly used by businesses. For the general public, these Internet service providers coined the terms “ broadband Internet ” or “ high-speed Internet access ” in order to differentiate high-speed data access services such as ADSL and cable television from traditional dial-up service. In fact, one of the driving forces behind the wireless last-mile technology is that the broadband Internet access of ADSL and cable has grown rapidly in recent years.
The second type of wireless MANs targets mobile data access. In a sense, 2.5G and 3G cellular networks could be considered wireless MANs or wireless WANs as they have provided wide-area mobile data access for cell phone users. On the other hand, it would be natural to speculate on extending wireless LANs to cover a larger area and to allow roaming across areas covered by these base stations. Still, this type of wireless MAN relies on a wired network infrastructure to function, as the base stations connect directly to a wired network. Many proprietary wireless MANs have been in operation for years. They mainly target a very narrow business market such as mobile professionals, rather than the general public.
The third type of MAN is a pure wireless network, in which backbones as well as the means of access are both wireless. Base stations are not connected to a backend wired network; instead, they coordinate with adjacent base stations, forming a mesh for data forwarding over a wide area. This is a significant development with regard to providing data access services to underdeveloped areas where no fixed networks exist.
Source of Information : Elsevier Wireless Networking Complete 2010