JVC Professional APRIL 2007 NAB-2007 The ProHD Report
Copyright 2007 JVC Professional Products Company All rights reserved Page 27 of 43
WiMAX wireless broadband is (almost) here
WiMAX is a new wireless digital communications system intended for wireless
"metropolitan area networks" (MAN). Theoretically, WiMAX can provide
broadband wireless access (BWA) up to 30 miles for fixed stations, and 3 - 10 miles
for mobile stations. In contrast, the older WiFi/802.11 wireless local area network
standard is limited in most cases to only 100 - 300 feet. WiMAX operates on both
licensed and non-licensed frequencies, providing a regulated environment.
WiMAX is a second-generation protocol that allows for more efficient bandwidth
use, interference avoidance, and is intended to allow higher data rates over longer
distances. WiMAX is expected to be a very well recognized term to describe
wireless Internet access throughout the world in the near future. However, much of
the talk remains about one way delivery services to consumers (IPTV, mobile video
etc.) although it is a fully two-way system.
But, as we can easily recognize, the powerful microwave WiMAX transmitter at the
base station may reach for up to 30 miles, a small powerless transmitter in your
laptop may only reach part of the way back to the fixed station. Thus, practical
implementations may offer a bidirectional reach of one to several miles. A stationary
ENG Van may have no problem in connecting upstream, while a moving ENG Van
may be more challenging.
Frequency bands are available in the 10-66GHz range for licensed users,
while the unlicensed users are delegated to selected areas within the 2-11GHz
spectrum. Between Base Stations and fixed users (i.e. homes), the connectivity is
the most robust as there are no moving target variables. Between Base Stations and
mobile users, the range is severely limited.
WiMAX offers a theoretical bandwidth of maximum 75Mbps. This bandwidth
may be achieved using 64QAM 3/4 modulation, but only under optimal transmission
conditions. WiMAX supports a wide range of modulation schemes to enable the
maximum bandwidth under any specific condition.
WiMAX offers a theoretical maximum range of 30 miles with a direct line of
sight. Near-line-of-sight (NLOS) seriously limits the range. In addition, some of the
frequencies utilized by WiMAX are subject to rainfade interference. The unlicensed
WiMAX frequencies are subject to RF interference from competing technologies and
competing WiMAX networks.