WiMAX Standards IEEE 802.16
The standard WiMAX was published at the end of 2001. In accordance with the hierarchy of wireless access standards, it belongs to the class MAN (Metropolitan Area Network). For a number of factors, such as bandwidth, coverage and services, WiMAX outperforms the Wi-Fi standard (IEEE802.11) of the LAN class (Local Area Network), allowing it to build regional, national and even global networks with a developed infrastructure. At the physical level, two fundamentally different technologies are used in the WiMAX standard. Data can be transmitted by modulating one carrier frequency (SC-Single Carrier) or multiple sub-carriers-OFDM technology. In the SC mode, the same requirements apply to radio channels as in radio relay networks: the use of direct rays only and the use of narrowly directional antennas, suppression of all reflected beams in order to eliminate intersymbol interference. In this regard, SC technology cannot be used in mass-use networks with multipath propagation of radio waves in communication channels.
The transition to OFDM technology occurred in 2004 with the advent of the new WiMAX standard: 802.16-2004. This technology eliminates inter-symbol interference. In the next version of the standard, the OFDM parameters were significantly changed. In particular, they switched to scalable OFDM: the number of subcarriers used became dependent on the operating band (SOFDM), and the subscriber began to allocate a certain number of sub-channels (SOFDMA - Scalable OFDM Access). In addition, there was an opportunity of realization of handovers. This version of the WiMAX standard was given the name of mobile WiMAX or 802.16e standard. The 802.16e option is the basic one in the existing WiMAX networks. The last few years the standard was constantly improved. For example, it was supplemented with 802.16i and 802.16j standards. The latter allows expanding existing networks by using repeaters. In 2011, a new version of the WiMAX standard, 802.16m, was approved. It is designed for building networks with a bandwidth above 100 Mb/s and for implementing a number of new promising services.
IEEE 802.16: Was released in 2001; frequency bands 11 – 66 GHz; mobility – no; technology – SC; channel width - 20, 25, 28 MHz.
IEEE 802.16-2004 (802.16d): Was released in 2004; frequency bands 2 – 11 GHz; mobility – no; technology – SC or OFDM (256); channel width - 1,75; 3,5; 7; 14; 1,25; 5; 10; 15; 8,75 MHz.
IEEE 802.16е: Was released in 2005; frequency bands 11 – 66 GHz, 2 - 11 GHz (fixed), 2 – 6 GHz (mobile); mobility – yes; technology – SC or OFDM (256), or SOFDM (128, 512, 1024, 2048); channel width - 1,25; 5; 10; 20 MHz.
IEEE 802.16k: Was released in 2007; frequency bands 11 – 66 GHz, 2 – 11 GHz (mobile); mobility – yes; technology – SC or OFDM (256), or SOFDM (128, 512, 1024, 2048); channel width - 1,25; 5; 10; 20 MHz.
IEEE 802.16-2009: Was released in 2009; frequency bands 11 – 66 GHz, 2 – 11 GHz (mobile); mobility – yes; technology – SC or OFDM (256), or SOFDM (128, 512, 1024, 2048); channel width - 1,25; 5; 10; 20 MHz.
IEEE 802.16j: Was released in 2009; frequency bands 11 – 66 GHz, 2 – 11 GHz (mobile); mobility – yes; technology – SC or OFDM (256), or SOFDM (128, 512, 1024, 2048) + retranslation; channel width - 1,25; 5; 10; 20 MHz.
IEEE 802.16m: Was released in 2011; frequency bands below 3,6 GHz; mobility – yes; technology –SOFDMA; channel width - 1‒ 20 MHz.
WiMAX is a long-range system covering kilometers of space that typically uses licensed frequency spectra (although it is possible to use unlicensed frequencies) to provide a connection to the Internet, such as a point-to-point provider, to the end user. Different 802.16 family standards provide different types of access, from mobile (similar to data transfer from mobile phones) to fixed (alternative to wired access, where the user's wireless equipment is tied to a location).
Wi-Fi is a shorter-acting system, usually covering tens of meters, which uses unlicensed frequency bands to provide access to the network. Usually, Wi-Fi is used by users to access their own local network, which may or may not be connected to the Internet.
WiMAX and Wi-Fi have a completely different Quality of Service (QoS) mechanism. WiMAX uses a mechanism based on establishing a connection between the base station and the user's device. Each connection is based on a special scheduling algorithm that can guarantee the QoS parameter for each connection. Wi-Fi, in turn, uses a QoS mechanism similar to that used in Ethernet, in which packets receive a different priority. This approach does not guarantee the same QoS for each connection.
WiMAX technology has several advantages:
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WiMAX networks allow operators and service providers to cover not only new potential users economically, but also expand the range of information and communication technologies for users already having fixed access.
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The standard combines technologies of the operator level (to unify many subnets and give them access to the Internet), as well as the technology of the “last mile” (the final segment from the point of entry into the provider's network to the user's computer), which creates universality and, consequently, increases the reliability of the system.
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Wireless technologies are more flexible and, as a result, are easier to deploy, as they can be scaled as needed.
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Ease of installation as a factor in reducing the cost of deploying networks in developing countries, sparsely populated or remote areas.
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The coverage range is an essential indicator of the radio communication system. Now, most wireless broadband technologies require direct visibility between network objects. WiMAX, thanks to the use of OFDM technology, creates coverage areas in the absence of line of sight from the client equipment to the base station, with distances of kilometers.
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WiMAX technology initially contains the IP protocol, which allows it to be easily and transparently integrated into local networks.
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WiMAX technology is suitable for fixed, moving and mobile network objects on a single infrastructure.