At this point you may be thinking: why devise a new standard? Why not just
use 802.11 or 3G? In fact, WiMAX combines aspects of both 802.11 and 3G,
making it more like a 4G technology.
Like 802.11, WiMAX is all about wirelessly connecting devices to the Internet at megabit/sec speeds, instead of using cable or DSL. The devices may be mobile, or at least portable. WiMAX did not start by adding low-rate data on the side of voice-like cellular networks; 802.16 was designed to carry IP packets over the air and to connect to an IP-based wired network with a minimum of fuss. The packets may carry peer-to-peer traffic, VoIP calls, or streaming media to support a range of applications. Also like 802.11, it is based on OFDM technology to ensure good performance in spite of wireless signal degradations such as multipath fading, and on MIMO technology to achieve high levels of throughput.
However, WiMAX is more like 3G (and thus unlike 802.11) in several key respects. The key technical problem is to achieve high capacity by the efficient use of spectrum, so that a large number of subscribers in a coverage area can all get high throughput. The typical distances are at least 10 times larger than for an 802.11 network. Consequently, WiMAX base stations are more powerful than 802.11 Access Points (APs). To handle weaker signals over larger distances, the base station uses more power and better antennas, and it performs more processing to handle errors. To maximize throughput, transmissions are carefully scheduled by the base station for each particular subscriber; spectrum use is not left to chance with CSMA/CA, which may waste capacity with collisions.
Licensed spectrum is the expected case for WiMAX, typically around 2.5 GHz in the U.S. The whole system is substantially more optimized than 802.11. This complexity is worth it, considering the large amount of money involved for licensed spectrum. Unlike 802.11, the result is a managed and reliable service with good support for quality of service.
With all of these features, 802.16 most closely resembles the 4G cellular networks that are now being standardized under the name LTE (Long Term Evolution). While 3G cellular networks are based on CDMA and support voice and data, 4G cellular networks will be based on OFDM with MIMO, and they will target data, with voice as just one application. It looks like WiMAX and 4G are on a collision course in terms of technology and applications. Perhaps this convergence is unsurprising, given that the Internet is the killer application and OFDM and MIMO are the best-known technologies for efficiently using the spectrum.
Like 802.11, WiMAX is all about wirelessly connecting devices to the Internet at megabit/sec speeds, instead of using cable or DSL. The devices may be mobile, or at least portable. WiMAX did not start by adding low-rate data on the side of voice-like cellular networks; 802.16 was designed to carry IP packets over the air and to connect to an IP-based wired network with a minimum of fuss. The packets may carry peer-to-peer traffic, VoIP calls, or streaming media to support a range of applications. Also like 802.11, it is based on OFDM technology to ensure good performance in spite of wireless signal degradations such as multipath fading, and on MIMO technology to achieve high levels of throughput.
However, WiMAX is more like 3G (and thus unlike 802.11) in several key respects. The key technical problem is to achieve high capacity by the efficient use of spectrum, so that a large number of subscribers in a coverage area can all get high throughput. The typical distances are at least 10 times larger than for an 802.11 network. Consequently, WiMAX base stations are more powerful than 802.11 Access Points (APs). To handle weaker signals over larger distances, the base station uses more power and better antennas, and it performs more processing to handle errors. To maximize throughput, transmissions are carefully scheduled by the base station for each particular subscriber; spectrum use is not left to chance with CSMA/CA, which may waste capacity with collisions.
Licensed spectrum is the expected case for WiMAX, typically around 2.5 GHz in the U.S. The whole system is substantially more optimized than 802.11. This complexity is worth it, considering the large amount of money involved for licensed spectrum. Unlike 802.11, the result is a managed and reliable service with good support for quality of service.
With all of these features, 802.16 most closely resembles the 4G cellular networks that are now being standardized under the name LTE (Long Term Evolution). While 3G cellular networks are based on CDMA and support voice and data, 4G cellular networks will be based on OFDM with MIMO, and they will target data, with voice as just one application. It looks like WiMAX and 4G are on a collision course in terms of technology and applications. Perhaps this convergence is unsurprising, given that the Internet is the killer application and OFDM and MIMO are the best-known technologies for efficiently using the spectrum.
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