From GSM to LTE: An Introduction to Mobile Networks and Mobile Broadband

5.2 Standards, Evolution and Profiles

WiMAX comprises a number of standards documents. The 802.16 standard, in general, addresses the physical layer (layer 1) and the data link layer (layer 2) of the network. In its initial version, 802.16a, the standard only supported line-of-sight connections between devices in the frequency range between 10 and 66 GHz. If WiMAX is operated in point-to-multipoint mode for Internet access, most SSs in cities and even rural areas will not have a free line of sight (LOS) to a WiMAX base station because of obstructing buildings or landscape. WiMAX was thus extended in the 802.16d standard for non-line of sight (NLOS) operation for the frequency range between 2 and −11 GHz. A single base station uses only a fraction of the frequency ranges given above. The system is very flexible and typical bandwidths per base station are between 3.5 and 25 MHz. The bandwidth allocated to a base station depends mainly on regulatory requirements and available spectrum, as there are many other wireless systems used in the 2–11 GHz frequency range, like UMTS, 802.11 WLAN and Bluetooth. In 2004, 802.16a and 802.16d were combined to form the IEEE 802.16-2004 standard, which thus includes network operation in both LOS and NLOS environments.

The first version of the 802.16 standard addresses only nonmoving or low-mobility users. SSs either use internal antennas or roof-mounted external antennas if further away from the base station. The 802.16e standard adds mobility to ...