LTE AND ITS EVOLUTION

ByJeevan Prakash-Mtech(1311EE05)

Motivation for LTE Need to ensure the continuity of

competitiveness of the 3G system for the future.

User demand for higher data rates and quality of service.

Packet switch optimized system. Continued demand for cost

reduction(CAPEX and OPEX) Low complexity.

LTE Overview

Fig1: GSM to LTE

Fig: Circuit and packet domains

LTE evolution

Fig3: LTE and its Evolution

Transmission Technologies Downlink --- OFDMA Uplink--- SC-FDMA

Fig4: OFDMA and SCFDMA

Channel Dependent Scheduling Channel-dependent scheduling in a mobile-

communication system deals with the question of how to share, between different users (different terminals), the radio resource(s) available in the system to achieve as efficient resource utilization as possible.

Fig5: Downlink channel-dependent scheduling in the time and frequency domains

ICIC-InterCell Interference Coordination

LTE is designed for frequency reuse 1 (To maximize spectrum efficiency), which means that all the neighbor cells are using same frequency channels and therefore there is no cell-planning to deal with the interference issues.

There is a high probability that a resource block scheduled to cell edge user, is also being transmitted by neighbor cell, resulting in high interference, eventually low throughput or call drops. Fig6: ICIC

ICIC- Cont. The LTE specification includes several

messages that can be communicated between eNodeBs using the X2 interface.

Fig7: X2 and s1 interface

Hybrid ARQ Hybrid automatic repeat request (hybrid

ARQ or HARQ) is a combination of high-rate forward error-correcting coding and ARQ error-control.

In practice, incorrectly received coded data blocks are often stored at the receiver rather than discarded, and when the retransmitted block is received, the two blocks are combined. This is called Hybrid ARQ with soft combining

Multi Antenna Support MIMO is used to increase the overall

bitrate.

Fig8: Multiple antennas

Spectrum Flexibility LTE supports both FDD and TDD within a

single radio-access technology, leading to a minimum of deviation between FDD and TDD for LTE-based radio access.

Half-duplex FDD reduces terminal complexity as no duplex filter is needed in the terminal.

Fig9: Frequency- and time-division duplex

Increased peak data rate, DL 3 Gbps, UL 1.5 Gbps

Higher spectral efficiency, from a maximum of 16bps/Hz in R8 to 30 bps/Hz in R10

Increased number of simultaneously active subscribers

Improved performance at cell edges, e.g. for DL 2x2 MIMO at least 2.40 bps/Hz/cell.

Multi Antenna Transmission

Carrier Aggregation To increase the capacity-increase the bandwidth Bandwidth can be extended by carrier

aggregation Multiple component carriers are aggregated and

jointly used for transmission to/from a single terminal

Fig10: Carrier aggregation

Cont.. Using contiguous component carriers

within the same operating frequency band called intra-band contiguous.

Fig11: Carrier aggregation-intra and inter bands

Relaying Relaying implies that the terminal

communicates with the network via a relay node that is wirelessly connected to a donor cell using the LTE radio-interface technology.

Fig12: Example of Relaying

References 4G LTE/LTE ADVANCED FOR MOBILE BROADB

AND by Erik Dahlman, Stefan Parkvall, and Johan Sköld, Elsevier press,2011

http://www.3gpp.org/technologies/keywords-acronyms/100-the-evolved-packet-core

http://www.3gpp.org/technologies/keywords-acronyms/98-lte

http://www.3gpp.org/technologies/keywords-acronyms/97-lte-advanced

http://3gppltee.blogspot.in/2012/09/what-is-icic-inter-cell-interference.html

Thank you