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Long-range Wi-Fi is used for low-cost, unregulated point-to-point computer network connections, as an alternative to other fixed wireless, cellular networks or satellite Internet access. Wi-Fi networks have a range that's limited by the transmission power, antenna type, the location they're used in, and the environment. A typical wireless router in an indoor point-to-multipoint arrangement using 802.11b or 802.11g and a stock antenna might have a range of . Outdoor point-to-point arrangements, through use of directional antennas, can be extended with many kilometers between stations. ==Introduction== Since the development of the IEEE 802.11 radio standard (marketed under the Wi-Fi brand name), the technology has become markedly less expensive and achieved higher bit rates. Long range Wi-Fi especially in the 2.4 GHz band (as the shorter range higher bit rate 5.8 GHz bands become popular alternatives to wired LAN connections) have proliferated with specialist devices. While Wi-Fi hotspots are ubiquitous in urban areas, some rural areas use more powerful longer range transceivers as alternatives to cell (GSM, CDMA) or fixed wireless (Motorola Canopy and other 900 MHz) applications. The main drawbacks of 2.4 GHz vs. these lower-frequency options are: *poor signal penetration - 2.4 GHz connections are effectively limited to line of sight or soft obstacles *far less range - GSM or CDMA cell phones can connect reliably at > distances. The range of GSM, imposed by the parameters of Time division multiple access, is set at 35 km. *few service providers commercially support long distance Wi-Fi connections Despite a lack of commercial service providers, applications for long range Wi-Fi have cropped up around the world. It has also been used in experimental trials in the developing world to link communities separated by difficult geography with few or no other connectivity options. Some benefits of using long range Wi-Fi for these applications include: *unlicensed spectrum - avoiding negotiations with incumbent telecom providers, governments or others *smaller, simpler, cheaper antennas - 2.4 GHz antennas are less than half the size of comparable strength 900 MHz antennas and require less lightning protection *availability of proven free software like OpenWrt, DD-WRT, Tomato that works even on old routers (WRT54G for instance) and makes modes like WDS, OLSR, etc., available to anyone. Including revenue sharing models for hotspots. Nonprofit organizations operating widespread installations, such as forest services, also make extensive use of long-range Wi-Fi to augment or replace older communications technologies such as shortwave or microwave transceivers in licensed bands. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Long-range Wi-Fi」の詳細全文を読む スポンサード リンク
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