2.1 Introduction for Long Term Evolution (LTE):
Long Term Evolution
(LTE) is a 4G wireless broadband technology developed by the Third Generation
Partnership Project (3GPP), an industry trade group.
3GPP engineers named
the technology "Long Term Evolution" because it represents the next
step (4G) in a progression from GSM, a 2G
standard, to UMTS, the 3G
technologies based upon GSM.
LTE provides
significantly increased peak data rates, with the potential for 100 Mbps
downstream and 30 Mbps upstream, reduced latency,
scalable bandwidth capacity, and backwards compatibility with existing GSM and
UMTS technology, Future developments to could yield peak throughput on the
order of 300 Mbps.
The upper layers of
LTE are based upon TCP/IP, which
will likely result in an all-IP network similar to the current state of wired
communications.
LTE will support
mixed data, voice, video and messaging traffic, and it uses OFDM
(Orthogonal Frequency Division Multiplexing) , and in later releases, MIMO
(Multiple Input Multiple Output) antenna technology similar to that used in the
IEEE 802.11n wireless
local area network (WLAN)
standard.
The higher signal to
noise ratio (SNR) at the
receiver enabled by MIMO, along with OFDM, provides improved coverage and
throughput, especially in dense urban areas.
2.2 Why LTE
Matters:
Smaller, faster and more portable are persistent trends in the digital world, the computing power that once required a room sized machine can now be found in laptops and handheld devices, and you can put stacks of CDs in your pocket in the form of a portable media player.
The same
trends affect the cellular market, and pose some interesting engineering challenges.
Cellular
long term evolution (LTE) is the next step forward in cellular 3G services, with
an expected market rollout in the 2009 time frame, LTE technology is a based on
a 3GPP standard that provides for a downlink speed of up to 100 megabits per
second (Mbps) and an uplink speed of up to 50 Mbps.
With multiple antennas, speeds can reach more than 320
Mbps on the downlink. Fixed wireless and wired standards are already
approaching or achieving 100 Mbps or faster, and LTE is a way for cellular
communications to operate at that high data rate.
2.3 Steps towards LTE :
The design target of the
first version of the LTE system was being finalized in June 2006. It aimed to
solve some of the old systems problems and reach more capabilities. The delays
have to be reduced in terms of both connection establishment and transmission
latency.
The user data rates are also increased. The cell edge data rates
have to be increased with more simplification for the hand over problem.
Flexible band width has to be valid to improve the spectral efficiency.
The system must be capable with the old systems to simplify the
network architecture. Finally it aimed to have lower power consumption for the
mobile terminal.
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