tailieunhanh - Future terrestrial broadcast systems

This article provides a general overview of broadcasting and TV white spaces. However, some of the information is specific to the European market and, therefore, may not apply to other regions such as the United States. | Future Terrestrial Broadcast Systems . . An overview of the use of TV white spaces. Due to the growing demand for high data rates wireless communication systems require more and more terrestrial frequency resources. Usable frequencies however are typically fully allocated to all kinds of wireless technology. One possible solution to meet the increasing data traffic demands is to build smaller radio cells to reuse spectrum more efficiently. However the associated costs for new infrastructure and increased energy consumption make this option economically unviable. Therefore efforts are being made to make static primary usage with well-known coverage areas which makes it relatively easy to implement a system for secondary use. As indicated in Figure 1 secondary users cannot use all the potential TV white spaces outside the broadcaster s coverage range as this might interfere with TV receivers at the edges of the broadcast coverage areas. As a result the number of potential TV white spaces is reduced the safety margin in Figure 1 is marked in green . The amount of TV-white-space spectrum can be relatively large. However in many cases this resource cannot be use of locally vacant spectrum that is primarily licensed to other wireless systems on a license-exempt or secondary license basis. Locally underutilized spectrum can be found in many frequency ranges . in military aeronautical and TV spectrum or in frequency bands allocated to historic communication systems and is usually referred to as spectrum holes or white spaces 1 . Before these frequency resources are allowed to be exploited by secondary users regulators must ensure that primary users will not be negatively affected by additional interference. Currently spectrum allocated to ter- f restrial TV broadcasting ultrahigh frequency UHF bands from 470 to 790 MHz is very popular for potential secondary exploitation mainly due to its good signal propagation characteristics for the coverage of large areas. TV .

• Kĩ thuật Viễn thông
• Future terrestrial broadcast systems
• Wireless broadband in rural areas
• Wi fi hotspot coverage
• Program making and special events
• Machine to machine communication