technology (i.e. cdma 1x-advanced), which included an advanced vocoder,
mobile receive diversity, an advanced receiver with interference cancella-
tion, and advanced power control. It may be noted that, although 1xEV-DV
was standardized, it never took off as a technology due to the reluctance of
the operator community to adopt the technology and the absence of proper
eco-systems.
A disruptive technology known as mobile WiMAX based on orthog-
onal frequency-division multiplexing (OFDM) technology was standar-
dized in 2006, and was dubbed the first 4G multiple access system. This
technology was based on the IEEE 802.16e standard and offered scalable
bandwidth up to 20 MHz, higher peak rates, and better spectral efficien-
cies than those provided by 3.5G systems. With the emergence of packet-
based wireless broadband systems such as WiMAX, it was evident that a
comprehensive evolution of UMTS would be required in order for it to
remain competitive in the long term. As a result, work began on Evolved
UMTS Terrestrial Radio Access (E-UTRA) based on the OFDM air
interface. The Long Term Evolution (LTE Rel-8) system supports high
peak data rates and provides low latency, improved system capacity and
coverage, reduced operating costs, efficient multi-antenna support, effi-
cient support for packet data transmission, flexible bandwidth of up to 20
MHz, and seamless integration with existing systems. The CDMA-based
HSPA technology is also being enhanced to support quad carriers (band-
width up to 20 MHz), MIMO, and higher-order modulation both on the
downlink and on the uplink. A 4G proposal called Ultra Mobile
Broadband (UMB) based on OFDM was also adopted by 3GPP2, but it
failed to make any impact.
Both WiMAX and LTE are currently being enhanced (LTE-Advanced
and 802.16m) so as to support even higher peak rates, higher throughput
and coverage, and lower latencies resulting in a better user experience.
Further, LTE-Advanced and 802.16m also enable one to meet or exceed
IMT-Advanced requirements. Finally, the 4.5G wireless broadband sys-
tems will be standardized in 3GPP Rel-12 in the 2013–2017 timeframe. It
is clear that 4.5G systems will further enhance the 4G systems in terms of
user experience, sector spectral efficiency, and peak rates, but the exact
features for 4.5G systems are still being decided.
2 wireless broadband technology
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