What is WiMax?
WiMAX is defined as Worldwide Interoperability for Microwave Access by the WiMAX Forum, formed in June 2001 to promote conformance and interoperability of the IEEE 802.16 standard, officially known as WirelessMAN. The Forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL."
Uses
Broadband Access
Many companies are closely examining WiMAX for "last mile" connectivity at high data rates. This could result in lower pricing for both home and business customers as competition lowers prices.
In areas without pre-existing physical cable or telephone networks, WiMAX may be a viable alternative for broadband access that has been economically unavailable. Prior to WiMAX, many operators have been using proprietary fixed wireless technologies for broadband services.
WiMAX subscriber units are available in both indoor and outdoor versions from several manufacturers. Self install indoor units are convenient, but the subscriber must be significantly closer to the WiMAX base station than with professionally installed units. As such, indoor installed units require a much higher infrastructure investment as well as operational cost (site lease, backhaul, maintenance) due to the high number of base stations required to cover a given area. Indoor units are comparable in size to a cable modem or DSL modem. Outdoor units allow for the subscriber to be much further away from the WiMAX base station, but usually require professional installation. Outdoor units are roughly the size of a textbook, and their installation is comparable to a residential satellite dish.
Limitations
A commonly held misconception is that WiMAX will deliver 70 Mbit/s, over 70 miles (112.6 kilometers). Each of these is true individually, given ideal circumstances, but they are not simultaneously true. In practice this means that in line-of-sight environments you could deliver symmetrical speeds of 10Mbps at 10km but in urban environments it is more likely that 30% of installations may be non-line-of-sight and therefore users may only receive 10Mbps over 2km. WiMAX has some similarities to DSL in this respect, where one can either have high bandwidth or long reach, but not both simultaneously. The other feature to consider with WiMAX is that available bandwidth is shared between users in a given radio sector, so if there are many active users in a single sector, each will get reduced bandwidth. However, unlike SDSL where contention is very noticeable at a 5:1 ratio (if you are sharing your connection with a large media firm for example), WiMAX does not have this problem. Typically each cell has a whole 100Mbps backhaul so there is no contention here. In practice, many users will have a range of 2-, 4-, 6-, 8- or 10Mbps services and the bandwidth can be shared. If the network becomes busy the business model is more like GSM or UMTS than DSL. It is easy to predict capacity requirements as you add customers and additional radio cards can be added on the same sector to increase the capacity.
Spectrum Allocations issues
The 802.16 specification applies across a wide swath of the RF spectrum. However, specification is not the same as permission to use. There is no uniform global licensed spectrum for WiMAX. In the US, the biggest segment available is around 2.5 GHz, and is already assigned, primarily to Sprint Nextel and Clearwire. Elsewhere in the world, the most likely bands used will be around 3.5 GHz, 2.3/2.5 GHz, or 5 GHz, with 2.3/2.5 GHz probably being most important in Asia. In addition, several companies have announced plans to utilize the WiMAX standard in the 1.7/2.1 GHz spectrum band recently auctioned by the FCC, for deployment of "Advanced Wireless Services" (AWS).
There is some prospect in the United States that some of a 700 MHz band might be made available for WiMAX use, but it is currently assigned to analog TV and awaits the complete rollout of digital TV before it can become available, likely by 2009. In any case, there will be other uses suggested for that spectrum if and when it actually becomes open.
It seems likely that there will be several variants of 802.16, depending on local regulatory conditions and thus on which spectrum is used, even if everything but the underlying radio frequencies is the same. WiMAX equipment will not, therefore, be as portable as it might have been - perhaps even less so than WiFi, whose assigned channels in unlicensed spectrum vary little from jurisdiction to jurisdiction.
The actual radio bandwidth of spectrum allocations is also likely to vary. Typical allocations are likely to provide channels of 5 MHz or 7 MHz. In principle the larger the bandwidth allocation of the spectrum, the higher the bandwidth that WiMAX can support for user traffic.
Uses
Broadband Access
Many companies are closely examining WiMAX for "last mile" connectivity at high data rates. This could result in lower pricing for both home and business customers as competition lowers prices.
In areas without pre-existing physical cable or telephone networks, WiMAX may be a viable alternative for broadband access that has been economically unavailable. Prior to WiMAX, many operators have been using proprietary fixed wireless technologies for broadband services.
WiMAX subscriber units are available in both indoor and outdoor versions from several manufacturers. Self install indoor units are convenient, but the subscriber must be significantly closer to the WiMAX base station than with professionally installed units. As such, indoor installed units require a much higher infrastructure investment as well as operational cost (site lease, backhaul, maintenance) due to the high number of base stations required to cover a given area. Indoor units are comparable in size to a cable modem or DSL modem. Outdoor units allow for the subscriber to be much further away from the WiMAX base station, but usually require professional installation. Outdoor units are roughly the size of a textbook, and their installation is comparable to a residential satellite dish.
Limitations
A commonly held misconception is that WiMAX will deliver 70 Mbit/s, over 70 miles (112.6 kilometers). Each of these is true individually, given ideal circumstances, but they are not simultaneously true. In practice this means that in line-of-sight environments you could deliver symmetrical speeds of 10Mbps at 10km but in urban environments it is more likely that 30% of installations may be non-line-of-sight and therefore users may only receive 10Mbps over 2km. WiMAX has some similarities to DSL in this respect, where one can either have high bandwidth or long reach, but not both simultaneously. The other feature to consider with WiMAX is that available bandwidth is shared between users in a given radio sector, so if there are many active users in a single sector, each will get reduced bandwidth. However, unlike SDSL where contention is very noticeable at a 5:1 ratio (if you are sharing your connection with a large media firm for example), WiMAX does not have this problem. Typically each cell has a whole 100Mbps backhaul so there is no contention here. In practice, many users will have a range of 2-, 4-, 6-, 8- or 10Mbps services and the bandwidth can be shared. If the network becomes busy the business model is more like GSM or UMTS than DSL. It is easy to predict capacity requirements as you add customers and additional radio cards can be added on the same sector to increase the capacity.
Spectrum Allocations issues
The 802.16 specification applies across a wide swath of the RF spectrum. However, specification is not the same as permission to use. There is no uniform global licensed spectrum for WiMAX. In the US, the biggest segment available is around 2.5 GHz, and is already assigned, primarily to Sprint Nextel and Clearwire. Elsewhere in the world, the most likely bands used will be around 3.5 GHz, 2.3/2.5 GHz, or 5 GHz, with 2.3/2.5 GHz probably being most important in Asia. In addition, several companies have announced plans to utilize the WiMAX standard in the 1.7/2.1 GHz spectrum band recently auctioned by the FCC, for deployment of "Advanced Wireless Services" (AWS).
There is some prospect in the United States that some of a 700 MHz band might be made available for WiMAX use, but it is currently assigned to analog TV and awaits the complete rollout of digital TV before it can become available, likely by 2009. In any case, there will be other uses suggested for that spectrum if and when it actually becomes open.
It seems likely that there will be several variants of 802.16, depending on local regulatory conditions and thus on which spectrum is used, even if everything but the underlying radio frequencies is the same. WiMAX equipment will not, therefore, be as portable as it might have been - perhaps even less so than WiFi, whose assigned channels in unlicensed spectrum vary little from jurisdiction to jurisdiction.
The actual radio bandwidth of spectrum allocations is also likely to vary. Typical allocations are likely to provide channels of 5 MHz or 7 MHz. In principle the larger the bandwidth allocation of the spectrum, the higher the bandwidth that WiMAX can support for user traffic.
posted by wifi guy at
9:01 AM
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