Wireless mesh network?? Wireless Mesh Technology and Networking – wireless mesh
In recent years by a high degree of attention and rapid development of new network technologies to support broadband high-speed multimedia services. Article on the wireless Mesh network technology and applications to discuss, review the history of development of wireless Mesh networks, basic technology, typical applications and current developments. With the distribution of future wireless technologies and wireless distribution networks, wireless Mesh technology and wireless mobile communication network will be the basic network technology and network architecture, to infiltrate a variety of wireless networks, play a greater role.
Keywords: Wireless mesh networks; Mesh Router ; Wireless broadband access in the future wireless communication
Wireless mesh network (WMN) technology is IP-based access for new wireless mobile Communications technology Suitable for regional environmental coverage and broadband high-speed wireless access. Wireless Mesh networks based on the occurrence of network between the many wireless access points, the mutual Cooperation And synergy with broadband high-speed and high spectral efficiency advantages of a dynamic self-organizing, self-configuring, self-maintenance features outstanding, so the wireless Mesh network technology and research and development and practical application, a current hot topic wireless mobile communication of 1, particularly in long-term evolution of future mobile communication systems (LTE), the wireless Mesh technology and the Internet has become the focus of attention [1-6].
1 Wireless Mesh Networks Origin Wireless Mesh Networks
the emergence and development, with the western developed countries, especially the United States, 80 in the 20th century, the rise of Internet and wireless local area network and application directly. Personal computer applications and Internet can enable people to exchange of information, and information become extremely convenient and easy application, greatly changed people's social activities and living conditions, promote the rapid development and social progress. However, already have the layout of urban construction and building, not for the Internet's need for any change and reconstruction. Building layout can not change, urban construction can not be destroyed, so that the coverage and application of Internet has caused extreme difficulties. Therefore, wireless communications and wireless coverage with excellent prospects. Wireless coverage for Internet access for the user terminal means, a very effective and convenient, get much attention, have research and applications, such as IEEE802 series of standards and products, is a typical representative of Wireless Mesh. However, all cities, all areas with limited Internet access points and network connection location, to a wireless coverage across the region has brought problems.
Figure 1 is a wireless IP access point (wireless gateway), on a given area of wireless coverage map. High-rise blocks in the city and the specific environment, it is impossible for large-scale buildings and block construction and change, a large area may have only a wireless gateway (WGW) access to Internet. Clearly, to achieve a single cover, in wireless mobile band, WGW and the corresponding user terminal transmission signal power will be great, this is often not allowed or not. In addition, IP data transmission, high data rate requirements, communication quality, low error rate, also need to receive adequate signal power. WGW large coverage area, also requires the signal emission power. For example, Figure 1, a distance of terminal 1 to WGW R1, stable emission signal received power P1; Terminal 4 to WGW distance is R4, stable power to receive the transmit signal P4. If the R4 is R1 4 times, the wireless signal propagation fading factor a = 4 (typically 3 to 5), that is, R4 = 4R1, then:
P4 = 4aP1 = 256P1 Obvious place to cover the edge of the signal power to increase 250 times, it is impossible to achieve common personal terminal. Also, if WGW using a bandwidth of wireless mobile band B, for single coverage, each user needs to transmit data bandwidth of b, then the entire region supports the largest number of multi-user:
M = B / b Obviously, there's a single cover, not to reuse a given frequency band to support fewer terminals, multi-user ability. Large transmit signal power requirements to support the number of users were not high, is shown in Figure 1 a single wireless access point coverage of major IP flaw.
Order to solve this problem, the 80s of the 20th century, two effective solutions.
A solution shown in Figure 2. In order to maintain the signal in Figure 1, the smaller transmission power P1 can be applied to all terminals, and to the edge of the cover or the remote user terminals to access WGW, used by a routing function for relay terminal adjacent to relay through the multi-hop , access to the WGW, to achieve Internet access under the small power. This area covers the formation of micro-power solutions for a comprehensive, constitute the AdHoc network. This network enables small signal power access, while access to the largest number of users does not increase, but the relay relay communication between user terminals need to increase the overhead. This dependence has a larger terminal routing in case of terminal mobility routing and network topology can not be fixed, variable big. However, AdHoc wireless network does not need to add another Router To achieve micro-cell coverage, through the end of the relay Relay access Internet, on the Construction of the terminal is not moving, location, relatively random distribution of the wireless sensor network is very convenient, practical and effective.
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