The switch to LTE is driven by a num-
ber of factors, including the need for
higher bit rates. In order to increase the
bit rate, the following options exist:
oƞ 5SEƞHIGHERORDERƞMODULATIONƞFORƞBITƞ
rates larger than the bandwidth).
oƞ 5SEƞHIGHERƞBANDWIDTHSƞ
oƞ )MPROVEƞ#)ƞUSINGƞMETHODSƞINCLUD-
ing Tx/Rx diversity, beam forming,
and interference reduction tech-
niques such as:
– More complex receivers, such as
GRAKEs used in HSPA, reducing
self-interference
– New radio access technologies,
such as OFDMA/SC-FDMA used
in LTE/eUTRAN, which reduce self-
interference (to a near-zero level)
– Making smarter use of C/I (spatial
multiplexing, a.k.a. MIMO)
One of the main advantages of LTE
is that it uses variations on all of the
above strategies.
“LTE offers a simple,
cost-effective
migration path.”
Orthogonal Frequency Division Mul-
tiplexing (OFDM) is the radio access
technology used for downlink in LTE
(for the uplink it is SC-FDMA). OFDM
meets the LTE requirement for spectrum
flexibility and enables cost-efficient so-
lutions for very wide carriers with high
peak rates.
LTE is characterized by simplicity, with
flexible carrier bandwidths and features
that simplify the building and manage-
ment of cellular networks. Besides,
LTE will be deployed in parallel with
simplified, IP-based core and transport
networks that are comparatively easy to
build and maintain.
Key characteristics of LTE:
oƞ &LEXIBLEƞBANDWIDTHƞUSAGEƞFROMƞ
1.4MHz to 20MHz)
oƞ /RTHOGONALITYƞINƞUPLINKƞANDƞDOWNLINKƞ
(no intra-cell interference)
oƞ !DVANCEDƞCODINGƞANDƞMODULATIONƞ
(QPSK, 16QAM, 64QAM depending
on channel quality, several coding
schemes)
oƞ &$$ƞANDƞ4$$ƞSUPPORT
oƞ !DVANCEDƞANTENNAƞTECHNOLOGYƞ
(MIMO)
LTE promises to offer a simple, cost-
effective migration path for current and
future 3G systems. With a focus on
services from the packet-switched do-
main, it is currently the most advanced
step along the road to 4G.
THE NEXT STEP IN THE
EVOLUTION OF WIRELESS
By ANDERS WANNSTROM and LISA SIGLER
Long Term Evolution (LTE) is the next big step beyond HSPA in the
development of 3GPP technologies. It is being standardized in 3GPP
Release 8. Designed to meet the skyrocketing demand for mobile
broadband, LTE networks will deliver downlink peak rates of at least
100 Mbit/s, and the technology allows for speeds over 200 Mbit/s.
LTE:
Photo: Fotograf Paulina
[6] 1.2009 TEMS
™
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