lte ( 4th generation mobile )

8/4/2019 LTE ( 4th Generation Mobile )

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Mahmoud Abdel-Aziz [email protected]


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Mobile System Generations


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1G (Early 1980s)

Analog speech communications. Analog FDMA.

Ex: AMPS

2G (Early 1990s)

Digital modulation of speech

communications.

Advanced security and roaming. TDMA and narrowband CDMA.

Ex: GSM, IS-95 (cdmaOne), and PDC


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3G (Late 1990s)

Global harmonization and roaming.

Wideband CDMA

Ex: UMTS, cdma2000, and TD-SCDMA


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3GPP Evolution

Release 99 (Mar. 2000): UMTS/WCDMARel-5 (Mar. 2002): HSDPA

Rel-6 (Mar. 2005): HSUPA

Rel-7 (2007): DL MIMO, IMS (IP MultimediaSubsystem),

optimized real-time services (VoIP, gaming, push-to-talk).

Long Term Evolution (LTE)

3GPP work on the Evolution of the 3G Mobile

System started in November 2004. Standardized in the form of Rel-8.

Spec finalized and approved in January 2008.

Target deployment in 2010.

LTE-Advanced study phase in progress.


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Requirements of LTEPeak data rate

100 Mbps DL/ 50 Mbps UL within 20MHz bandwidth.

Up to 200 active users in a cell (5 MHz) Less than 5 ms user-plane latency Mobility

Optimized for 0 ~ 15 km/h. 15 ~ 120 km/h supported with high

performance. Supported up to 350 km/h or even up

to 500 km/h.


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LTE EnablingTechnologies

OFDM (Orthogonal Frequency DivisionMultiplexing).

Frequency domain equalization.

SC-FDMA (Single Carrier FDMA).

MIMO (Multi-Input Multi-Output).

Multicarrier channel-dependentresource scheduling.

Fractional frequency reuse.


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Single Carrier FDMA (SC-FDMA)

SC-FDMA is a new single carrier multiple

access technique which has similar structureand performance to OFDMA.

Utilizes single carrier modulation andorthogonal frequency multiplexing using DFT-

spreading in the transmitter and frequencydomain equalization in the receiver.

A salient advantage of SC-FDMA overOFDM/OFDMA is low PAPR.

Efficient transmitter and improved cell-edge performance.


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Protocol Architecture


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e worArchitecture

* E-UTRAN (Evolved Universal Terrestrial Radio

Access Network)


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eNB ( eNodeB )

All radio interface-related functions

MME

Manages mobility, UE identity, andsecurity parameters.

S-GW Node that terminates the interface

towards E-UTRAN.

P-GW Node that terminates the interface

towards PDN.


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LTE Physical Channels

DL Physical Broadcast Channel (PBCH) Physical Control Format Indicator Channel (PCFICH) Physical Downlink Control Channel (PDCCH)

Physical Hybrid ARQ Indicator Channel (PHICH)

Physical Downlink Shared Channel (PDSCH) Physical Multicast Channel (PMCH)

UL Physical Uplink Control Channel (PUCCH)

Physical Uplink Shared Channel (PUSCH)

Physical Random Access Channel (PRACH)


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Physical layer transport channels offer

information transfer to medium access control(MAC) and higher layers.

DL

Broadcast Channel (BCH)

Downlink Shared Channel (DL-SCH) Paging Channel (PCH)

Multicast Channel (MCH)

UL

Uplink Shared Channel (UL-SCH) Random Access Channel (RACH)

LTE TransportChannels


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LTE Logical Channels Logical channels are offered by the MAC

layer.Control Channels: Control-plane information

Broadcast Control Channel (BCCH)

Paging Control Channel (PCCH) Common Control Channel (CCCH) Multicast Control Channel (MCCH) Dedicated Control Channel (DCCH)

Traffic Channels: User-plane information Dedicated Traffic Channel (DTCH) Multicast Traffic Channel (MTCH)


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MIMO enhancementsImproved MIMO transmission

Gain for additional diversity becomes smaller- Anyway not always wanted e.g. frequency selective

scheduling

Gain from spatial multiplexing only is questionable

- limited to hotspot and indoor environments (small cells,scattered propagation environment, very low user mobility)

- Still the only way to achieve the very high peak data rates

Spatial multiplexing in general needs high SNR regions

Use of beam forming combined with spatial multiplexingwithin different beams could be most beneficial .


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MIMO Enhancements for LTE-Advanced


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Downlink MIMO transmission

- 4 UE receive antennas and 4x4

MIMO could become baseline-Downlink peak data rates achievedby the use of 8x8 MIMO

(reference signals for 8 antennas

required)Uplink MIMO transmission

- 2 UE transmit antennas and 2x2MIMO could become baseline

- Uplink peak data rates achieved bythe use of 4x4 MIMO

Increase peak data rate, but also

coverage and capacity .


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LTE VS. WIMAX


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