WiMAX IEEE 802.16 technology tutorial
- IEEE 802.16, WiMAX, Wireless Microwave Access technology is able to provide 4G levels of Broadband Wireless Access for both mobile and fixed applications.
WiMAX technology is a broadband wireless data communications technology based around the IEE 802.16 standard providing high speed data over a wide area.
The letters of WiMAX stand for Worldwide Interoperability for Microwave Access (AXess), and it is a technology for point to multipoint wireless networking.
WiMAX technology is able to meet the needs of a large variety of users from those in developed nations wanting to install a new high speed data network very cheaply without the cost and time required to install a wired network, to those in rural areas needing fast access where wired solutions may not be viable because of the distances and costs involved. Additionally it is being used for mobile applications, providing high speed data to users on the move.
What is WiMAX technology? - basics
The standard for WiMAX technology is a standard for Wireless Metropolitan Area Networks (WMANs) that has been developed by working group number 16 of IEEE 802, specializing in point-to-multipoint broadband wireless access. Initially 802.16a was developed and launched, but now it has been further refined. 802.16d or 802.16-2004 was released as a refined version of the 802.16a standard aimed at fixed applications. Another version of the standard, 802.16e or 802.16-2005 was also released and aimed at the roaming and mobile markets.
WiMAX technology uses some key technologies to enable it to provide the high speed data rates:
- OFDM (Orthogonal Frequency Division Multiplex): OFDM has been incorporated into WiMAX technology to enable it to provide high speed data without the selective fading and other issues of other forms of signal format.
Note on OFDM:
Orthogonal Frequency Division Multiplex (OFDM) is a form of transmission that uses a large number of close spaced carriers that are modulated with low rate data. Normally these signals would be expected to interfere with each other, but by making the signals orthogonal to each other there is no mutual interference. The data to be transmitted is split across all the carriers to give resilience against selective fading from multi-path effects..
Click on the link for an OFDM tutorial
- MIMO (Multiple Input Multiple Output): WiMAX technology makes use of multipath propagation using MIMO. By utilising the multiple signal paths that exist, the use of MIMO either enables operation with lower signal strength levels, or it allows for higher data rates.
Note on MIMO:
Two major limitations in communications channels can be multipath interference, and the data throughput limitations as a result of Shannon's Law. MIMO provides a way of utilising the multiple signal paths that exist between a transmitter and receiver to significantly improve the data throughput available on a given channel with its defined bandwidth. By using multiple antennas at the transmitter and receiver along with some complex digital signal processing, MIMO technology enables the system to set up multiple data streams on the same channel, thereby increasing the data capacity of a channel.
Click on the link for a MIMO tutorial
The WiMAX Forum is a wireless industry consortium with a growing number of members including many industry leaders. It has been set up to support and develop WiMAX technology worldwide, bring common standards across the globe to enable the technology to become an established worldwide technology.
One of the aims of the forum is to enable a standard to be adopted that will enable full interoperability between products. Learning from the problems of poor interoperability experienced with previous wireless standards, and the impact that this had on take up, the WiMAX Forum aims to prevent this from happening. Ultimately vendors will be able to have products certified under the auspices of the Forum, and then be able to advertise their products as "Forum Certified".
Although WiMAX technology will support traffic based on transport technologies ranging from Ethernet, Internet Protocol (IP), and Asynchronous Transfer Mode (ATM), the Forum will only certify the IP-related elements of the 802.16 products. The focus is on IP operations because this is the now the main protocol that is used.
Since its initial conception, new applications for WiMAX have been developed and as a result there are two "flavours" of WiMAX technology that are available:
- 802.16d (802.16-2004)
- 802.16e (802.16-2005)
The two flavours of WiMAX technology are used for different applications and although they are based on the same standard, the implementation of each has been optimised to suit its particular application.
- 802.16d - DSL replacement The 802.16d version is often referred to as 802.16-2004 and it is closer to what may be termed the original version of WiMAX defined under 802.16a. It is aimed at fixed applications and providing a wireless equivalent of DSL broadband data. In fact the WiMAX Forum describes the technology as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL."
802.16d is able to provide data rates of up to 75 Mbps and as a result it is ideal for fixed, DSL replacement applications. It may also be used for backhaul where the final data may be distributed further to individual users. Cell radii are typically up to 75 km.
- 802.16e - Nomadic / Mobile While 802.16 / WiMAX was originally envisaged as being a fixed only technology, with the need for people on the move requiring high speed data at a cost less than that provided by cellular services and opportunity for a mobile version was seen and 802.16e was developed. This standard is also widely known as 802.16-2005. It currently provides the ability for users to connect to a WiMAX cell from a variety of locations, and there are future enhancements to provide cell handover.
802.16e is able to provide data rates up to 15 Mbps and the cell radius distances are typically between 2 and 4 km.
The competition with WiMAX, 802.16 depends upon the type or version being used. Although initially it was thought that there could be significant competition with Wi-Fi, there are other areas to which WiMAX is posing a threat.
- DSL cable lines WiMAX is able to provide high speed data links to users and in this way it can pose a threat to DSL cable operators.
- Cell phone operators Cell phone operators saw the mobile version of WiMAX as a significant threat. It is offering data download speeds in excess of those that can be offered even using the cellular UMTS HSPA (High Speed Packet Access) However LTE has gained acceptance as the global cellular telecommunications system.
WiMAX technology is now being deployed in many areas and while it was initially seen as yet another wireless standard that might fall into the background, it is now emerging as a major front runner and posing threats to other areas of the industry.
By Ian Poole
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