At first, the IEEE 802.16e and IEEE 802.20 standards may appear to be very similar. Both standards were developed to specify an air interface for providing broadband access to mobile users. Both standards will have low latency and will utilize packet architecture. However, other than the resemblances of their aims, there are few other parallels.
First the 802.16e standard is an extension of an existing standard, IEEE 802.16a. IEEE 802.20 is an entirely new standard optimized for mobility. 802.16e uses extensions to the MAC and PHY layers from 802.16a, while 802.20 uses new MAC and PHY layer designs. The result of this is that 802.16e-based product will be available well before any 802.20 products are on the market.
Although there is an obvious parallel between the technologies used by both standards and the type of user they are aiming to serve, there is a primary difference between the two. IEEE 802.20 is designed for users traveling at speeds of up to 250Kmh (155 mph), whereas 802.16e is aimed at users traveling at vehicular speed. So someone who is walking and needs broadband access via their PDA or laptop could do so using 802.16e-based technology. On the other hand, a user traveling on a high-speed train would require an 802.20-based product to gain wireless broadband access.
Another key difference is that the 802.16e standard is a last-mile solution. It is aimed at PDA and laptop users and is seen as an extension to existing fixed wireless infrastructure, whereas 802.20 will use adaptive antennas and IP to provide a fully mobile broadband alternative to planned cellular services such as 3G.
A final crucial difference between the two is that 802.16e will operate in the 2 GHz to 6 GHz licensed bands, whereas 802.20 works in licensed bands below 3.5 GHz.
How the standards are being implemented
Prior to ratification of both standards, there are ongoing attempts to implement devices based on them. Siemens has announced that it will develop Flash-OFDM equipment based on a prestandard version of IEEE 802.20. This can be used by wireless operators when they are implementing IEEE 802.20 wireless broadband technology. Using Flash-OFDM equipment enables carriers that don’t have the spectrum to install 3G cellular data services but still control spectrum in the 450 MHz range and utilize 802.20 products. The 450 MHz range was formerly used for analog services.
The first product based on a prestandard version of IEEE 802.16e is called Mobilis. By using Wi-LAN’s patented W-OFDM technology it offers throughput of up to 32Mbps and speeds approaching 110Kmh.
As a Summary of Comparing IEEE 802.16e and IEEE 802.20
Although there appear to be many similarities between IEEE 802.16e and 802.20 – mainly in terms of the architecture they employ and what they are trying to achieve – further examination of the standards shows significant differences between the two. Both standards aim to provide wireless broadband connectivity and both can be used by mobile users. However, 802.20 is aimed at users moving at high speed, whereas 802.16e can be used only by those traveling on foot. There are also additional differences with how each standard is deployed and implemented.
Siemens is developing Flash-OFDM equipment that is based on prestandard 802.20 technologies. The first product to utilize the IEEE 802.16e standard, Mobilis, already exists.