Long Term Evolution

Advantages

LTE is a standard for wireless communication of high-speed data

High throughput Low latency FDD and TDD Seamless Connection Plug and play Simple architecture

Frequency Band: The LTE standard covers a range of many different bands. In North America, 700, 750, 800,850, 1900 and 2600 MHz are used 2500 MHz in South America 800, 900, 1800, 2600 MHz in Europe 1800 and 2600 MHz in Asia and 1800 MHz and 2300 MHz in Australia New Zealand.

As a result, phones from one country may not work in other countries. Users will need a multi-band capable phone for roaming internationally.

LTE Architecture

The User Equipment (UE) The Evolved UMTS Terrestrial Radio Access

Network (E-UTRAN) The Evolved Packet Core (EPC)

E-UTRAN

Interface between the UE and EPC

It contains the evolved base stations, called

eNodeB or eNB

Sends and receives radio transmission All low-level operations like handover command S1 interface X2 interface

Evolved Packet Core

Home Subscriber Server (HSS) The Packet Data Network (PDN) Gateway (P-GW)

communicates with the outside world , policy enforcement, packet filtering

The serving gateway (S-GW) acts as a router, and forwards data between the base station and the PDN gateway

The mobility management entity (MME): Choosing SGW Generation and allocation of temporary identities to UE

Information flows between the different protocols are known as channels and signals:

Logical Channels Transport Channels Physical Channels

LTE Protocol Stack Layers Physical Layer MAC Layer :

Mapping between logical channels and transport channels

Multiplexing and de-multiplexing of MAC SDUs

Scheduling information Error correction through

HARQ Priority handling,

dynamic scheduling, Priority handling between logical channels, Logical Channel prioritization

Radio Link Control (RLC): ARQ error correction Segmentation/concatenation of PDUs Reordering for in-sequence delivery Duplicate detection

Radio Resource Control (RRC): Broadcast system information related to the access stratum

and transport of the non-access stratum (NAS) messages, paging, establishment and release of the RRC connection, security key management, handover, UE measurements

Packet Data Convergence Protocol (PDCP): For the RRC layer it provides transport of its data with

ciphering and integrity protection For the IP layer transport of the IP packets, header

compression, ciphering, duplicate detection and retransmission of its own SDUs during handover

Non Access Stratum (NAS) Protocols: NAS protocols support the mobility of the UE and the

session management procedures to establish and maintain IP connectivity between the UE and a PDN GW

OFDM and SC-FDMA

To overcome multi path fading LTE uses OFDM for downlink

Drawbacks of OFDM High peak-to-average power ratio Sensitive to frequency offset, hence to Doppler-shift as

well SC-FDMA Technology for uplink

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