Long Term Evolution/LT

E Access Network for EPC/SAE Networks

INAM ULLAHHead of Product Development

TURNOTECH

Why LTE/SAE? LTE Overview LTE technical objectives SAE architechture LTE Radio interface LTE RAN Interfaces Functions of eNB

Contents

Packet Switched data is becoming more and more dominant

VoIP is the most efficient method to transfer voice data Need for PS optimised system Amount of data is continuously growingNeed for higher data rates at lower cost Users demand better quality to accept new servicesHigh quality needs to be quaranteed Alternative solution for non-3GPP technologies (WiMAX)

needed LTE will enhance the system to satisfy these requirements.

Why LTE

3GPP Long Term Evolution/LTE, wireless communication standard by 3GPP for high-speed data for mobile phones and data terminals.

LTE is the Radio Access Network for Evolved Packet Core (EPC/EPS/SAE)

Its an Evolution from GSM/GPRS/EDGE and UMTS/HSPA network technologies, for increasing the capacity and speed using new modulation /DSP (Digital Signal Processing) techniques

Its wireless interface is incompatible with 2G and 3G networks, and so it must be operated on a separate wireless spectrum ( not Handovers)

LTE Overview

User throughput [/MHz]: Downlink: 3 to 4 times Release 6 HSDPA Uplink: 2 to 3 times Release 6 Enhanced Uplink

Downlink Capacity: Peak data rate of 100 Mbps in 20 MHz maximum bandwidth

Uplink capacity: Peak data rate of 50 Mbps in 20 MHz maximum bandwidth

Latency: Transition time less than 5 ms in ideal conditions (user plane), 100 ms control plane (fast connection setup)

Mobility: Optimised for low speed but supporting 120 km/h Most data users are less mobile!

Simplified architecture: Simpler E-UTRAN architecture: no RNC, no CS domain,

Scalable bandwidth: 1.25MHz to 20MHz: Deployment possible in GSM bands.

LTE Objectives

SAE Architecture

Evolved Radio Access Network (eRAN) Consists of the eNodeB (eNB) Offers Radio Resource Control (RRC) functionality Radio Resource Management, admission control, scheduling, ciphering/deciphering of user and

control plane data, and compression/decompression in DL/UL user plane packet headers Serving Gateway (SGW)

Routes and forwards user data packets Acts as the mobility anchor for the user plane

During inter-eNB handovers Between LTE and other 3GPP technologies

Pages idle state UE when DL data arrives for the UE Packet Data Network Gateway (PDN GW)

Provides connectivity to the UE to external packet data networks A UE may have simultaneous connectivity with more than one PDN GW Performs policy enforcement, packet filtering, and charge support Acts as mobility anchor between 3GPP and no-3GPP technologies

Mobility Management Entity (MME) Manages and stores UE contexts

UE/user identities, UE mobility state, user security parameters Paging message distribution

SAE/EPS Network Components

LTE Architecture

LTE vs UMTS

Flat Architecture

OFDM (Orthogonal Frequency Division Multiplex): OFDM technology has been incorporated into LTE because it enables high data bandwidths to be transmitted efficiently while still providing a high degree of resilience to reflections and interference.

SC-FDMA (Single Carrier - Frequency Division Multiple Access) is used in the uplink. SC-FDMA is used in view of the fact that its peak to average power ratio is small and the more constant power enables high RF power amplifier efficiency in the mobile handsets - an important factor for battery power equipment. 

MIMO (Multiple Input Multiple Output): One of the main problems that previous telecommunications systems has encountered is that of multiple signals arising from the many reflections that are encountered. By using MIMO, these additional signal paths can be used to advantage and are able to be used to increase the throughput.

LTE radio interface

Terminates RRC, RLC and MAC protocols and takes care of Radio Resource Management functions Controls radio bearers Controls radio admissions Controls mobility connections Allocates radio resources dynamically (scheduling) Receives measurement reports from UE

Selects MME at UE attachment Schedules and transmits paging messages coming from MME Schedules and transmits broadcast information coming from MME &

O&M Decides measurement report configuration for mobility and scheduling Does IP header compression and encryption of user data streams

Functions of eNB

LTE RAN Interfaces

Interfaces using IP over E1/T1/ATM/Ethernet /…X2 interface between eNBs for handovers

Handover in 10 msNo soft handovers

S1 Interface for Load sharing S1 divided to S1-U (to UPE) and S1-C (to CPE)

Single node failure has limited effects

LTE RAN Interfaces

Provides non guaranteed delivery of user plane PDUs between the eNB and the SGW.

The transport network layer is built on IP transport and GTP-U is used on top of UDP/IP to carry the user plane PDUs between the eNB and the S-GW.

S1- Interface (User Interface)

The SCTP layer provides the guaranteed delivery of application layer messages.

The transport network layer is built on IP transport, similarly to the user plane but for the reliable transport of signaling messages SCTP is added on top of IP.

The application layer signaling protocol is referred to as S1-AP (S1 Application Protocol).

S1 interface ( control plane )

The X2 control plane interface (X2-CP) The application layer signaling protocol is referred to as X2-AP (X2

Application Protocol). The transport network layer of X-2 is built on SCTP on top of IP.

Functions Intra LTE-Access-System Mobility Support for UE in EMM-

CONNECTED: Context transfer from source eNB to target eNB; Control of user plane tunnels between source eNB and target eNB; Handover cancellation.

Uplink Load Management General X2 management and error handling functions:

Error indication.

X2 Interface

LTE Distributed Intelligence

The eNBs are connected directly to the core network gateway via a newly defined "S1 interface". In addition to this the new eNBs also connect to adjacent eNBs in a mesh via an "X2 interface". This provides a much greater level of direct interconnectivity. It also enables many calls to be routed very directly as a large number of calls and connections are to other mobiles in the same or adjacent cells. The new structure allows many calls to be routed far more directly and with only minimum interaction with the core network.

In addition to the new Layer 1 and Layer 2 functionality, eNBs handle several other functions. This includes the radio resource control including admission control, load balancing and radio mobility control including handover decisions for the mobile or user equipment (UE).

The additional levels of flexibility and functionality given to the new eNBs mean that they are more complex than the UMTS and previous generations of base-station. However the new 3G LTE SAE network structure enables far higher levels of performance. In addition to this their flexibility enables them to be updated to handle new upgrades to the system including the transition from 4G LTE to 4G LTE Advanced.

Continued..

The new System Architecture Evolution, SAE for LTE provides a new approach for the core network, enabling far higher levels of data to be transported to enable it to support the much higher data rates that will be possible with LTE. In addition to this, other features that enable the CAPEX and OPEX to be reduced when compared to existing systems, thereby enabling higher levels of efficiency to be achieved.

Continued..

LTE Channels

Physical channels: convey info from higher layersPhysical Downlink Shared Channel (PDSCH) - data and multimedia transport - very high data rates supported - BPSK, 16 QAM, 64 QAM Physical Downlink Control Channel (PDCCH) - Specific UE information- Only available modulation (QPSK) robustness preferredCommon Control Physical Channel (CCPCH) - Cell wide control information- Only QPSK available- Transmitted as closed as the center frequency as possible

DL CHANNELS and SIGNALS

1) Broadcast channel (BCH)2) Downlink Shared channel (DL-SCH) - Link adaptation - Suitable for using beam forming - Discontinuous receiving/ power saving 3) Paging channel (PGH)4) Multicast channel (MCH)

TRANSPORT CHANNELS

Physical Uplink Shared Channel (PUSCH) - BPSK, 16 QAM, 64 QAMPhysical Uplink Control Channel (PUCCH) - Convey channel quality information- ACK- Scheduling requestUplink Shared channel (UL-SCH) Random Access Channel (RACH)

UL CHANNELS

Support for relay node base stations Coordinated multipoint (CoMP) transmission and reception UE Dual TX antenna solutions for SU-MIMO and diversity MIMO Scalable system bandwidth exceeding 20 MHz, Up to 100 MHz Carrier aggregation of contiguous and non-contiguous spectrum allocations Local area optimization of air interface Nomadic / Local Area network and mobility solutions Flexible spectrum usage Cognitive radio Automatic and autonomous network configuration and operation Support of autonomous network and device test, measurement tied to network management

and optimization Enhanced precoding and forward error correction Interference management and suppression Asymmetric bandwidth assignment for FDD Hybrid OFDMA and SC-FDMA in uplink UL/DL inter eNB coordinated MIMO SONs, Self Organized Networks methodologies Multiple carrier spectrum access.

LTE Advanced