11/8/2012

1

Arief Hamdani Gunawan

1.1. Introduction to LTEIntroduction to LTE

2.2. OFDMAOFDMA

3.3. SCSC--FDMAFDMA

4.4. LTE Network and ProtocolLTE Network and Protocol

5. LTE Radio Procedures5. LTE Radio Procedures

6. LTE Uplink Physical Channels and 6. LTE Uplink Physical Channels and

SignalsSignals

7. LTE Mobility7. LTE Mobility

8. LTE Test and Measurement8. LTE Test and Measurement

Day Two

Arief Hamdani Gunawan

11/8/2012

2

Session 5: LTE Radio Procedures•LTE Initial Access

•Downlink physical channels and signals

•Cell search in LTE

•Primary Synchronization Signal

•Secondary Synchronization Signal

•Cell search in LTE, reference signals

•Downlink Reference Signals

•Cell Search in LTE, essential system information

•System Information Broadcast in LTE

•Random Access Procedure

•How to derive information in LTE

•Hybrid ARQ in Downlink

•Default EPS Bearer Setup

LTE Initial Access

11/8/2012

3

Downlink physical channels and signals

6

DL Physical Layer Procedures

• Cell search and synchronization

• Scheduling

– Dilakukan di base station (eNodeB)

– PDCCH (Phy DL Control Channel) menginformasikan alokasi time/freq resource

dan format transmisi yang digunakan kepada user.

– Scheduler mengevaluasi berbagai tipe informasi (parameter QoS, pengukuran

dari UE, kapabilitas UE, buffer status)

• Link Adaptation

– Skema modulasi dan coding untuk shared data channel diadaptasi sesuai

dengan kualitas link radio.

– Untuk tujuan ini, UE secara teratur melaporkan Channel Quality Indicator

(CQI) ke eNodeB.

• Hybrid ARQ (Automatic Repeat Request)

11/8/2012

4

Cell Search in LTE

8

Synchronization & Cell Search

• UE yang ingin mengakses suatu sel LTE, terlebih dahulu harus melakukan

prosedur Cell Search.

• Cell Search terdiri dari serangkaian tahapan sinkronisasi, dimana UE

menentukan parameter waktu & frekuensi yang diperlukan untuk

mendemodulasi sinyal DL dan untuk mengirimkan sinyal UL dengan timing

yang tepat.

• Tiga kebutuhan sinkronisasi utama:

– Symbol timing acquisition

– Carrier frequency synchronization

– Sampling clock synchronization

11/8/2012

5

9

Case StudyCase Study

Cell Search for Multiple Bandwidths - Problem

• LTE offers system flexibility by supporting systems and UEs of multiple bandwidths.

• Challenge in synchronization & bandwidth detection.

• Unbalance traffic loads may result

10

Case Study Case Study

Cell Search for Multiple Bandwidths - Solution

Step 1:

Cell search using synchronization channel

�detect center 1.25 spectrum

of entire 20-MHz spectrum

Step 2:

BCH reception

Step 3:

UE shifts to the center of carrier frequency assigned

by the system and initiates data transmission

Source: 3GPP R1-061651, “3GPP TR 25.814 v 1.5.0”

•The UE first detect the central

part of the spectrum regardless of

the transmission bandwidth

capability of the UE and that of the

cell site (BTS).

•UE moves to the transmission

bandwidth according to the UE

capability for actual

communication

11/8/2012

6

11

Synchronization Sequence

Dua prosedur cell search dalam LTE :

• INITIAL SYNCHRONIZATION

– UE mendeteksi suatu sel LTE dan mendekode semua informasi yang

diperlukan untuk registrasi.

– Diperlukan pada saat UE di-ON-kan atau ketika kehilangan koneksi dengan

serving cell.

• NEW CELL IDENTIFICATION

– Dilakukan ketika UE sudah terhubung ke suatu sel LTE dan sedang dalam

proses mendeteksi suatu sel tetangga baru.

– Dalam hal ini UE melaporkan hasil pengukuran yang terkait dengan sel baru ke

serving cell, sebagai persiapan untuk handover.

12

RS : Reference Signal

PBCH : Physical Broadcast Channel

PSS : non-coherent detection

SSS : non-coherent/coherent detection

Cell Search procedure

• PSS (Primary Synchronization Signal) dan SSS (Secondary Synchronization Signal) adalah kanal-kanal fisik

yang di-broadcast dalam setiap sel.

• Pendeteksian dua kanal ini :

– memungkinkan dilakukannya sinkronisasi waktu & frekwensi.

– memberikan identitas phy layer dari sel dan panjang cyclic prefix kepada UE.

– memberitahu UE apakah sel menggunakan FDD atau TDD.

11/8/2012

7

Primary Synchronization Signal

Secondary Synchronization Signal

11/8/2012

8

15

PSS and SSS frame and slot structure in FDD

16

PSS and SSS frame and slot structure in TDD

11/8/2012

9

Cell search in LTE, reference signals

Downlink reference signals

11/8/2012

10

19

Reference Signals & Channel Estimation

• Berbeda dengan jaringan berorientasi paket, LTE tidak menggunakan PHY Preamble untuk

memfasilitasi estimasi carrier offset, estimasi kanal, sinkronisasi waktu, dsb.

• Sebaliknya LTE menggunakan sinyal referensi khusus yang disisipkan dalam PRB.

• Sinyal referensi tsb dikirimkan selama simbol OFDM pertama dan kelima dari setiap slot

untuk short CP, dan simbol OFDM pertama dan ke-empat untuk long CP.

• Simbol-simbol referensi dikirimkan setiap selang 6 subcarrier.

• Dalam LTE downlink, terdapat 3 tipe RS :

– Cell-specific RS

– UE-specific RS

– MBSFN-specific RS

20

DL Reference Signal Structure for 2 & 4 Antenna Transmission

11/8/2012

11

21

RS-aided Channel Estimation

• Problem estimasi kanal berhubungan dengan model kanal yang diasumsikan, yang

ditentukan oleh karakteristik propagasi fisik, termasuk jumlah antena Tx/Rx,

bandwidth transmisi, carrier frequency, konfigurasi sel dan kecepatan relatif antara

eNodeB dan UE.

• Kondisi propagasi mencirikan fungsi korelasi kanal dalam 3-dimensi, yaitu : domain

frekwensi, domain waktu dan domain ruang (spatial).

• Frequency-Domain Channel Estimation

– menggunakan Linear Interpolation Estimator

– menggunakan IFFT Estimator

• Time-Domain Channel Estimation

– menggunakan Finite & Infinite Length MMSE (Min Mean Squared Error)

– menggunakan Normalized Least-Mean-Square

• Spatial-Domain Channel Estimation

Cell search in LTE, essential system information

11/8/2012

12

23

P-SCH and S-SCH

Physical Downlink Shared Channel

Physical Downlink Control Channel

Physical Broadcast Channel

Physical Control Format Indicator Channel

Physical Multicast Channel

Physical Hybrid ARQ Indicator Channel

P-SCH : Primary Synchronization Channel

S-SCH : Secondary Synchronization Channel

Downlink Physical Channels and Signals

24

LTE Downlink Physical Channels 1

11/8/2012

13

25

LTE Downlink Physical Channels 2

System information broadcast in LTE

11/8/2012

14

Random Access Procedure

How to derive information in LTE?

11/8/2012

15

Indicating PDCCH format

30

Channel Coding & Link Adaptation

• Prinsip link adaptation menjadi landasan perancangan suatu interface radio yang

efisien untuk trafik data berbasis paket-switched.

• Link adaptation dalam LTE dilakukan dengan mengatur laju data informasi yang

dikirim (skema modulasi dan channel coding rate) secara dinamis, sesuai dengan

kualitas radio link.

• Link adaptation mempunyai hubungan yang sangat erat dengan perancangan

skema channel coding yang digunakan untuk FEC.

• Skema channel coding untuk FEC yang digunakan dalam LTE :

– Convolutional Coding

– Turbo Coding

– LDPC (Low Density Parity Check) coding

• Fitur advanced channel coding yang ditambahkan dalam LTE adalah : HARQ

(Hybrid Automatic Repeat Request).

11/8/2012

16

31

Link Adaptation

• UE: Reports the finest possible

granularity

– The reporting scheme and

granularity depend on the radio

channel quality variation!

• ENB: Receives mobility and

quality information

– Incremental feedback

information forms a rough

picture of the radio channel with

the first report (s). The

granularity gets finer and finer

with each report.

32

Adaptive Modulation

• Adaptive Modulation & Coding

memastikan error rate tetap dibawah

limit yang dapat diterima, dengan

pengaturan modulasi dan coding rate

secara dinamis.

• Level modulasi yang lebih rendah

meningkatkan link budget dan fade

margin.

• Perubahan lingkungan propagasi

menyebabkan perubahan skema

modulasi dan coding.

• Dalam perencanaan kapasitas, variasi

kanal propagasi jangka-panjang harus

diperhitungkan.

11/8/2012

17

33

Typical SNR Performance of LTE Modulation and Coding

34

Adaptive Modulation & Coding

11/8/2012

18

QoS parameters for QCI

Hybrid ARQ in the downlink

• ACK/NACK for data packets transmitted in the downlink is the same as for HSDPA,

where the UE is able to request retransmission of incorrectly received data

packets,

– ACK/NACK is transmitted in UL, either on PUCCH (Physical Uplink Control Channel) or

multiplexed within PUSCH (Physical Uplink Shared Channel) see description of those UL

channels for details),

– ACK/NACK transmission refers to the data packet received four sub-frames (= 4 ms)

before,

– 8 HARQ processes can be used in parallel in downlink.

11/8/2012

19

Hybrid ARQ Operation

Default EPS bearer setup

11/8/2012

20

Session 6: Uplink Physical Channels and Signals•Scheduling of UL Data

•UL Frequency Hopping

•Demodulation Reference Signal (DRS) in the UL

•Sounding Reference Signal (SRS) in the UL

•PUSCH power control & timing relation

•Acknowledging UL data packets on PHICH

•Physical UL Control Channel

Uplink physical channels and signals

11/8/2012

21

Scheduling of uplink data

42

Physical Random Access Channel

Physical Uplink Shared Channel

Physical Uplink Control Channel

Uplink Physical Channels and Signals

• PUSCH (Physical Uplink Shared Channel): used for uplink shared data transmission.

• PUCCH (Physical Uplink Control Channel): used to carry ACK/NACK, CQI for downlink

transmission and scheduling request for uplink transmission.

11/8/2012

22

43

Uplink Data Transmission

• Pada uplink, data dialokasikan dalam beberapa resource block (RB).

• Ukuran RB untuk uplink sama dengan yang digunakan untuk downlink,

tetapi untuk menyederhanakan disain DFT dalam pemrosesan sinyal

uplink, tidak semua kelipatan bulat digunakan (hanya kelipatan 2, 3 dan 5).

• Interval waktu transmisi uplink adalah 1 ms (sama dengan downlink).

• User data dibawa pada Physical Uplink Shared Channel (PUSCH), yang

ditentukan oleh BW transmisi dan pola frequency hoping.

• Physical Uplink Control Channel (PUCCH) membawa informasi kontrol

uplink, seperti : laporan CQI dan informasi ACK/NACK, yang terkait dengan

paket-paket data yang diterima pada arah downlink.

UL frequency hopping

Intra- and inter-subframe hopping,

• Intra-subframe hopping. UE hops to another frequency allocation from one slot to another within one subframe,

• Inter-subframe hopping. Frequency allocation changes from one subframeto another one,

Two types of hopping,

• Type I. Explicit frequency offset is used in the 2nd slot, can be configured and is indicated to the UE by resource block assignment / hopping resource allocation field in DCI format 0,

• Type II. Use of pre-defined hopping pattern, allocated BW is divided into sub-bands, hopping is done from one sub-band to another from one slot or subframe depending on configured frequency hopping scheme.

Screenshots of R&S® SMU200A Vector Signal Generator

11/8/2012

23

Demodulation Reference Signal (DRS) in the UL

Sounding Reference Signal (SRS) in the UL

11/8/2012

24

PUSCH power control & timing relation

48

Random Access

• Suatu LTE UE (User Equipment) hanya dapat di-scheduled untuk transmisi uplink, apabila uplink transmission timing-nya sinkron.

• Oleh karena itu LTE RACH (Random Access Channel) memainkan peran penting sebagai interface antara non-synchronized UE dan skema transmisi othogonal pada akses radio uplink LTE.

• Prosedur LTE random access mempunyai dua bentuk, yaitu : contention-based atau contention-free.

• Dalam prosedur contention-based, suatu random access preamble signature dipilih secara acak oleh UE, yang kemungkinan dapat menyebabkan lebih dari satu UE mengirimkan signature yang sama secara simultan.

• Dalam prosedur contention-free, eNodeB memiliki opsi untuk mencegah terjadinya contention dengan mengalokasikan suatu dedicated signature kepada UE.

11/8/2012

25

Contention-based Random Access Procedure

49

Step 1 : Preamble transmission

Step 2 : Random Access

Response

Step 3 : L2/L3 message

Step 4 : Contention resolution

message

Contention-free Random Access Procedure

50

Prosedur contention-free

random access dapat

diterapkan dalam hal

diperlukan low latency, seperti

handover dan new downlink

data.

11/8/2012

26

51

UL Transmission Procedures

• Uplink scheduling

– Dilakukan oleh base station (eNodeB)

– PDCCH (Phy DL Control Channel) menginformasikan alokasi time/freq resource dan format transmisi yang digunakan kepada user.

– Scheduler mengevaluasi berbagai tipe informasi (parameter QoS, pengukurandari UE, kapabilitas UE, buffer status)

• Uplink Adaptation

– Untuk keperluan adaptasi uplink, dapat digunakan : transmission power control, adaptive modulation & channel coding rate, serta adaptive transmission BW.

• Uplink timing control

– Diperlukan untuk menyelaraskan waktu transmisi dari UE-UE yang berbeda, dengan receiver window dari eNodeB.

• Hybrid ARQ

Acknowledging UL data packets on PHICH

11/8/2012

27

Physical Uplink Control Channel

PUCCH carries Uplink Control Information (UCI), when no PUSCH is available,

• If PUSCH is available, means resources have been allocated to the UE for data transmission, UCI are multiplexed with user data,

UCI are Scheduling Requests (SR), ACK/NACK information related to DL data packets, CQI, Pre-coding Matrix Information (PMI) and Rank Indication (RI) for MIMO,

PUCCH is transmitted on reserved frequency regions, configured by higher layers, which are located at the edge of the available bandwidth

• Minimizing effects of a possible frequency-selective fading affecting the radio channel,

• Inter-slot hopping is used on PUCCH,

• A RB can be configured to support a mix of PUCCH formats (2/2a/2b and 1/1a/1b) or exclusively 2/2a/2b,

PUCCH

• CQI / PMI / RI are only signaled via PUCCH when periodic reporting is requested, scheduled

and a periodic reporting is only done via PUSCH

11/8/2012

28

Physical Channel Procedure (1/2)

Physical Channel Procedure (2/2)

11/8/2012

29

Test1

2

3

4

A

B

C

D

E

Carries the DL-SCH and

PCH

SCH symbol timing

detection, frequency

offset detection

Cell ID detection,

radio frame detection

RB assignment, transport

format, RSN#, HARQ

Proc#, TCP Command,

Cyclic shift for DMRS, UE

identification

Operation BW, CP length,

MIMO config, cell ID, etc

5

Answer

Carries the DL-SCH and PCH

SCH symbol timing detection,

frequency offset detection

Cell ID detection,

radio frame detection

RB assignment, transport format,

RSN#, HARQ Proc#, TCP Command,

Cyclic shift for DMRS, UE

identification

Operation BW, CP length, MIMO

config, cell ID, etc

11/8/2012

30

Session 7: LTE Mobility•Handover (Intra-MME / Serving Gateway)

•LTE Interworking with 2G/3G: Two RRC States:

Connected and Idle

•LTE Interworking with CDMA2000 1xRTT and

HRPD

•MIMO

•LTE MIMO downlink modes

•LTE downlink transmitter chain

•Downlink transmitter diversity - Space Frequency

Block Coding (2 Tx antenna case)

•Downlink Spatial Multiplexing - codebook based

precoding

•LTE MIMO UL Schemes

• EPS uses the concept of EPS bearers to route IP traffic from a gateway in the PDN to the UE.

• A bearer is an IP packet flow with a defined Quality of Service (QoS) between the gateway and the UE.

• The E-UTRAN and EPC together set up and release bearers as required by applications.

SGSN

GPRS Core

3GPP

anchor

SAE

anchor

MME

UPE

Operator’s

IP Services

(e.g. IMS, PSS, etc,)

eNB

eNB eNB

eNB

Evolved RAN (LTE)

GERAN

UTRAN

Trusted non 3GPP

IP Access

EPDG

WLAN

Access Network

EPC (SAE)

IASA

GB

Iu

S3

S4S7

Rx+

S5a S5bS1

S2a

S2b

SGi

S6

WLAN 3GPP

IP Access

Logical High Level Architecture for The Evolved System

11/8/2012

31

SAE Bearer Model

User and bearer

information exchange for

inter 3GPP access system

mobility

Transfer of subscription and

authentication data for user

access to the evolved system (AAA

interface)

C-Plane : S1-C between eNB and MME

U-Plane : S1-U between eNB and UPE

MME : Mobility Management Entity

UPE : User Plane Entity

3GPP Anchor : Mobility anchor between 2G/3G and LTE access systems (based on GTP)

SAE Anchor : Mobility anchor between 3GPP access systems (2G/3G/LTE) and non-3GPP access systems (e.g. WLAN, WiMAX).

Overview of the evolved system architecture

11/8/2012

32

SAE Architecture – Functions per Element

SAE Architecture 3GPP2 Operator

detailed view, non-roaming case, 3GPP2 accesses

11/8/2012

33

SAE Roaming support

extending today’s successful model

SAE impact on IMS

overview

11/8/2012

34

Handover (Intra-MME/Serving Gateway)

LTE Interworking with 2G/3G

Two RRC states: CONNECTED & IDLE

11/8/2012

35

LTE Interworking with CDMA2000 1xRTT

and HRPD (High Rate Packet Data)

Introduction to MIMO:gains to exploit from multiple antenna usage

Transmit diversity (TxD)

• Combat fading

• Replicas of the same signal sent on several Tx antennas

• Get a higher SNR at the Rx

Spatial multiplexing (SM)

• Different data streams sent simultaneously on different antennas

• Higher data rate

• No diversity gain

• Limitation due to path correlation

Beamforming

11/8/2012

36

71

Multiple Antenna Technique:

Four Basic Model

72

Multiple Antenna Technique

Two popular techniques in MIMO wireless systems:

Spatial Diversity: Increased SNR

• Receive and transmit diversity mitigates

fading and improves link quality

Spatial Multiplexing: Increased rate

• Spatial multiplexing yields substantial

increase spectral efficiency

11/8/2012

37

73

Spatial Diversity

Transmit Diversity

• Space-time Code (STC): Redundant data sent over time and space domains

(antennas).

• Receive SNR increase about linearity with diversity order Nr Nt

• Provide diversity gain to combat fading

• Optional in 802.16d (2x2 Alamouti STBC), used in 3G CDMA

74

Spatial Multiplexing

MIMO Multiplexing

• Data is not redundant – less diversity but less repetition

• Provides multiplexing gain to increase data-rate

• Low (no) diversity compared with STC

11/8/2012

38

75

MIMO Operation

76

Diversity & MIMO

11/8/2012

39

LTE MIMO: downlink modes

• Transmit diversity:– Space Frequency Block Coding (SFBC)

– Increasing robustness of transmission

• Spatial multiplexing:– Transmission of different data streams simultaneously over

multiple spatial layers

– Codebook based precoding

– Open loop mode for high mobile speeds possible

• Cyclic delay diversity (CDD):– Addition of antenna specific cyclic shifts

– Results in additional multipath / increased frequency diversity

LTE downlink transmitter chain

11/8/2012

40

Downlink transmit diversitySpace-Frequency Block Coding (2 Tx antenna case)

Downlink spatial multiplexingcodebook based precoding

11/8/2012

41

LTE MIMO: uplink schemes

• Uplink transmit antenna selection:– 1 RF chain, 2 TX antennas at UE

side

– Closed loop selection of transmit antenna

– eNodeB signals antenna selection to UE

– Optional for UE to support

• Multi-user MIMO / collaborative MIMO:– Simultaneous transmission from 2

Ues on same time/frequency resource

– Each UE with single transmit antenna

– eNodeB selects UEs with close-to orthogonal radio channels

82

Multi User Scheduling

• Scheduler (untuk transmisi unicast) secara dinamis mengontrol resource waktudan frekwensi mana yang akan dialokasikan kepada suatu user pada suatu waktutertentu.

• DL control signalling memberitahu UE, resource dan format transmisi seperti apayang sudah dialokasikan.

• Scheduler dapat secara dinamis memilih strategi multiplexing terbaik daribeberapa metode yang ada, misalnya : localized atau distributed allocation.

• Scheduling berinteraksi erat dengan link adaptation dan HARQ.

• Pertimbangan scheduling antara lain didasarkan pada :

– minimum & maximum data rate

– daya yang tersedia untuk di-share

– Persyaratan target BER

– parameter QoS

– laporan CQI (Channel Quality Indicator)

– kapabilitas UE

11/8/2012

42

83

Channel-Dependent Scheduling

• Shared channel transmission

• Select user and data rate on

instantaneous channel quality

– Time-domain adaptation used

already in HSPA

• Scheduling in time and frequency

domain

– Link adaptation in time domain

only

84

Packet-scheduling framework

• Packet scheduler adalah entitas

pengendali untuk seluruh proses

scheduling.

• Berkonsultasi dengan modul LA (Link

Adaptation) untuk memperoleh estimasi

data rate yang dapat disuport untuk user

tertentu dalam sel.

• LA dapat menggunakan frequency-

selective CQI feedback dari user, untuk

memastikan estimasi data rate yang sesuai

dengan target BLER tertentu.

• Modul Offset calculation dalam proses

link-adaptation dapat digunakan untuk

menstabilkan performansi BLER dalam

kondisi LA yang tidak pasti.

11/8/2012

43

Session 8: LTE Test and Measurement•LTE RF Testing aspects

•eNB Modulation quality measurements

•ACLR in DL (FDD)

•eNB Performance Requirements

•UE RF Testing Aspects

•Transmit Modulation

•Inband Emission

•IQ Component

•ACLR Measurement

•Receiver characteristics

•LTE Wireless device testing from R&D upto conformance

•Stages of LTE terminal testing

•LTE Terminal Interoperability testing

•Test Scenarios for LTE Terminal IOT

•LTE Conformance Testing

•LTE Terminal Certification

•LTE Field Trials

System architecture for 3GPP access networks

11/8/2012

44

PCRF

• It is responsible for policy control decision-making, as

well as for controlling the flow-based charging

functionalities in the Policy Control Enforcement

Function (PCEF) which resides in the P-GW.

• The PCRF provides the QoS authorization (QoS class

identifier and bitrates) that decides how a certain

data flow will be treated in the PCEF and ensures

that this is in accordance with the user’s subscription

profile.

P-GW

• The P-GW is responsible for IP address allocation for the UE,

as well as QoS enforcement and flow-based charging

according to rules from the PCRF.

• The P-GW is responsible for the filtering of downlink user IP

packets into the different QoS based bearers. This is

performed based on Traffic Flow Templates (TFTs).

• The P-GW performs QoS enforcement for Guaranteed Bit Rate

(GBR) bearers.

• It also serves as the mobility anchor for inter-working with

non-3GPP technologies such as CDMA2000 and WiMAX

networks.

11/8/2012

45

S-GW

• All user IP packets are transferred through the S-GW, which serves as the local mobility anchor for the data bearers when the UE moves between eNodeBs.

• It also retains the information about the bearers when the UE is in idle state (known as ECM-IDLE) and temporarily buffers downlink data while the MME initiates paging of the UE to re-establish the bearers.

• In addition, the S-GW performs some administrative functions in the visited network such as collecting information for charging (e.g. the volume of data sent to or received from the user), and legal interception.

• It also serves as the mobility anchor for inter-working with other 3GPP technologies such as GPRS and UMTS.

MME

• The MME is the control node which processes the signaling

between the UE and the CN.

• The protocols running between the UE and the CN are known

as the Non-Access Stratum (NAS) protocols.

• The main functions supported by the MME are classified as:

– Functions related to bearer management. This includes the

establishment, maintenance and release of the bearers, and is

handled by the session management layer in the NAS protocol.

– Functions related to connection management. This includes the

establishment of the connection and security between the network

and UE, and is handled by the connection or mobility management

layer in the NAS protocol layer.

11/8/2012

46

HSS

• Home Subscription Server (HSS) is the subscription data repository for all permanent user data. It also records the location of the user in the level of visited network control node, such as MME. It is a database server maintained centrally in the home operator’s premises.

• The HSS stores the master copy of the subscriber profi le, which contains information about the services that are applicable to the user, including information about the allowed PDN connections, and whether roaming to a particular visited network is allowed or not. For supporting mobility between non-3GPP ANs, the HSS also stores the Identities of those P-GWs that are in use. The permanent key, which is used to calculate the authentication vectors that are sent to a visited network for user authentication and deriving subsequent keys for encryption and integrity protection, is stored in the Authentication Center (AuC), which is typically part of the HSS.

• In all signaling related to these functions, the HSS interacts with the MME. The HSS will need to be able to connect with every MME in the whole network, where its UEs are allowed to move. For each UE, the HSS records will point to one serving MME at a time, and as soon as a new MME reports that it is serving the UE, the HSS will cancel the location from the previous MME.

EPS Connection Management

• To reduce the overhead in the E-UTRAN and processing in the UE, all UE-related information in the access network can be released during long periods of data inactivity.

• This state is called EPS Connection Management IDLE (ECM-IDLE). The MME retains the UE context and the information about the established bearers during these idle periods.

• To allow the network to contact an ECM-IDLE UE, the UE updates the network as to its new location whenever it moves out of its current Tracking Area (TA); this procedure is called a ‘Tracking Area Update’. The MME is responsible for keeping track of the user location while the UE is in ECM-IDLE.

• When there is a need to deliver downlink data to an ECM-IDLE UE, the MME sends a paging message to all the eNodeBs in its current TA, and the eNodeBs page the UE over the radio interface. On receipt of a paging message, the UE performs a service request procedure which results in moving the UE to ECM-CONNECTED state.

11/8/2012

47

MME connections to other logical nodes

and main functions

S-GW connections to other logical nodes

and main functions

11/8/2012

48

P-GW connections to other logical nodes

and main functions

Each PCRF may be associated with one or more AF, P-GW and S-GW. There is only

one PCRF associated with each PDN connection that a single UE has.

PCRF connections to other logical nodes

and main functions

11/8/2012

49

LTE RF Testing AspectsBase station (eNodeB) according to 3GPP

• Measurements are performed using Fixed Reference Channels (FRC) and EUTRA Test Models (E-TM),

• Tx characteristic (= Downlink)– Base station output power

– Output power dynamics: RE Power Control dynamic range, total power dynamic range,

– Transmit ON/OFF power: Transmitter OFF power, transmitter transient period,

– Transmitted signal quality: FrequencyError, Error Vector Magnitude (EVM), Time alignment between transmitter antennas, DL RS power, etc. …

– Unwanted emissions: Occupied Bandwidth, Adjacent Channel Leakage Power Ratio (ACLR), Operating band unwanted emissions, etc. …

– Transmitter spurious emissions and intermodulation,

• Rx characteristics (= Uplink): Reference sensitivity level, Dynamic range, In-channel selectivity, Adjacent channel selectivity (ACS) and narrow-band blocking, Blocking, Receiver spurious emissions, Receiver intermodulation

• Performance requirements,– …for PUSCH: Fading conditions, UL

timing adjustment, high speed train, HARQ-ACK multiplexed in PUSCH,

– …for PUCCH: DTX to ACK performance, ACK missed detection PUCCH format 1a (single user), CQI missed detection for PUCCH format 2, ACK missed detection PUCCH format 1a (multiple user)

– PRACH performance: FALSE detection probability, detection requirements

3GPP TS 36.104: Base Station (BS) radio transmission and reception

eNB modulation quality measurements

• Frequency error– If frequency error is larger than a few subcarrier, demodulation at the UE

might not work properly and cause network interference,

– Quick test: OBW, Limit for frequency error after demodulation 0.05 ppm + 12 Hz (1ms),

• Error Vector Magnitude (EVM),– Amount of distortion effecting the receiver to demodulate the signal properly,

– Limit changes for modulation schemes QPSK (17.5%), 16QAM (12.5%), 64QAM (8%),

• Time alignment,– Only TX test defined for multiple antennas, measurement is to measure the

time delay between the signals for the two transmitting antennas, delay shall not exceed 65 ns,

• DL RS power– “Comparable” to WCDMA measurement CPICH RSCP; absolute DL RS power is

indicated on SIB Type 2, measured DL RS power shall be in the range of ±2.1 dB,

11/8/2012

50

ACLR in DL (FDD)

ACLR in DL (FDD):

No filter definition in LTE!

11/8/2012

51

eNB performance requirementsPRACH and preamble testing I

• PRACH testing is one of the performance requirements

defined in 3GPP TS 36.141 E-UTRA BS conformance testing,

– Total probability of FALSE detection of preamble (Pfa 0.1% or less),

– Probability of detection of preamble (Pd = 99% at defined SNR),

– Two modes of testing: normal and high-speed mode,

• Different SNR and fading profiles are used (table shows settings for

normal mode),

eNB performance requirementsPRACH and preamble testing I

– Depending on the mode different preambles are used to check

detection probability (table shows preamble to be used for normal

mode),

11/8/2012

52

eNB performance requirementsPRACH and preamble testing II

• According to 3GPP TS 36.211 the NCS

value is not set directly instead it is

translated to a NCS configuration

value,

• This value is set in the signal

generator R&S® SMx or R&S® AMU,

Screenshot taken

from R&S®

SMU200A Vector

Signal Generator

UE RF testing

11/8/2012

53

LTE RF Testing AspectsUser Equipment (UE) according to 3GPP

Tx characteristic

• Transmit power,

• Output power dynamics,

• Transmit Signal Quality,– Frequency error, EVM vs.

subcarrier, EVM vs. symbol, LO leakage, IQ imbalance, Inbandemission, spectrum flatness,

• Output RF spectrum emissions,– Occupied bandwidth, Spectrum

Emission Mask (SEM), Adjacent Channel Leakage Power Ratio (ACLR),

• Spurious Emission,

• Transmit Intermodulation,

Rx characteristics

• Reference sensitivity level,

• UE maximum input level,

• Adjacent channel selectivity,

• Blocking characteristics,

• Intermodulation characteristics,

• Spurious emissions,

Performance requirements

• Demodulation FDD PDSCH (FRC),

• Demodulation FDD PCFICH/PDCCH (FRC)

3GPP TS 36.101: User Equipment (UE) radio transmission and reception

Transmit modulation

According to 3GPP specification LO leakage (or IQ origin offset) is removed from evaluated

signal before calculating EVM and in-band emission.

11/8/2012

54

In-band emission

IQ component

• Also known is LO leakage, IQ offset, etc.,

• Measure of carrier feedthrough present in the signal,

• Removed from measured waveform, before calculating EVM and in-band emission

(3GPP TS 36.101 V8.3.0, Annex F),

• In difference to DL the DC subcarrier in UL is used for transmission, but subcarriers

are shifted half of subcarrier spacing (= 7.5 kHz) to be symmetric around DC

carrier,

• Due to this frequency shift energy of the LO falls into the two central subcarrier

11/8/2012

55

ACLR measurement I

Receiver characteristics

• Throughput shall be >95% for…

– Reference Sensitivity Level,

– Adjacent Channel Selectivity,

– Blocking Characteristics,

• …using the well-defined DL reference

channels according to 3GPP specification

11/8/2012

56

LTE wireless device testing

from R&D up to conformance

Stages of LTE terminal testing

11/8/2012

57

LTE terminal interoperability testingmotivation

• Interoperability testing is used to verify– Connectivity of the UE with the

real network (by means of base station simulators)

– Service quality, end-to-end performance

– Different LTE features and parametrizations

– Interworking between LTE and legacy technologies

• The complete UE protocol stack is tested.

• IOT test scenarios are based on requirements from real network operation and typical use cases.

LTE terminal interoperability testingexample test scenarios

• Registration

• UE initiated detach

• Network initiated detach

• Mobile originated EPS bearer establishment

• Mobile terminated EPS bearer establishment

• Cell (re-)selection

• GUTI reallocation

• Tracking are update

• …

• Plus: end-to-end scenarios (video streaming, VoIP, …)

• Plus: intra-LTE mobility, inter-RAT mobility

11/8/2012

58

Test scenarios for LTE terminal IOTdifferent sources for maximum test coverage

LTE conformance testingmotivation

• Verifying compliance of terminals to 3GPP LTE standard– by validated test cases

implemented on registered test platforms

– in order to ensure worldwide interoperability of the terminal within every mobile network

• 3GPP RAN5 defines conformance test specifications for– RF

– Radio Resource Management (RRM)

– Signaling

• Certification organizations (e.g. GCF) define certification criteria based on RAN5 test specifications

11/8/2012

59

LTE field trial testing and

coverage measurements

LTE field trialsrequirements from different deployment scenarios

• Bandwidths from 1.4 MHz to 20 MHz

• Different LTE FDD and TDD frequency bands

• Combination with legacy technologies

(GSM/EDGE, WCDMA/HSPA, CDMA2000 1xEV-

DO)

• Spectrum clearance and refarming scenarios

• Femto cell / Home eNB scenarios

11/8/2012

60

LTE field trialsscope of test tools

• Field trials provide input for:– Calibration and verification of

planning tools for different deployment scenarios

– Network optimization (capacity and quality)

– Quality of service verification

– Definition of Key Performance Indicators (KPIs) and verification, also from subscriber’s point of view

• Parallel use of scanners / measurement receivers for comparison with UE and base station behaviour

• Support of IOT activities

Example result from the fieldscanner measurements for LTE

11/8/2012

61

10 Steps to Determine 3G/4G

IP Data Throughput

1. Will my device connect?

2. Do I have a good quality

transmitter?

3. Do I have a good quality

receiver?

4. Can I achieve max E2E

tput under ideal

conditions with UDP

5. What about with TCP and

simultaneous UL/DL?

6. What happens if I try real

application?

7. What happens under non-

ideal conditions?

8. Is it robust?

9. Does it work closed loop?

10. How good is my battery

life?

Step 1: Will my device connect?

11/8/2012

62

Step 1: Will my device connect?

• Is the UE able to sync to the DL?

•Can I get through the connection set-up

• Can I ping my UE?

• If not take a log and de-bug message exchange

•Make edits as required with Message editor

2. Do I have a good quality Transmitter?

RF test

• High data throughput testing relies on good quality UL

transmissions

• Look for the following:– Ensure you have appropriate

power and attenuation settings

– High EVM for high order modulation schemes

– High EVM at the band edge

– Spurs both in band and out of band

– Linearity issues/ spectral growth

– Switching transients, LO settling time

– Repeat tests with any “other” radio’s active

11/8/2012

63

3GPP Tx Measurements

UL RF Measurements

11/8/2012

64

3. Do I have a good quality receiver?

• High Data throughput testing relies on good a quality receiver

• Look for the following:

– sensitivity for different modulation schemes

– Max input level performance

– susceptibility to interference (simultaneous UL/DL, other radios, spurs from digital board, …)

3. Do I have a good quality receiver?

11/8/2012

65

DL Data Throughput for TD LTE(20MHz channel, 2x2 MIMO, UL/DL config 5, special subframe config 6)

Measurement Technique: UDP vs FTP (TCP)

UDP

+ Unacknowledged

+ removes flow control complexity

+ removes higher layer acks

+ Less susceptible latency

- Not the full story for file transfers

- Not suitable for used in shared

networks

FTP

+ Simulates real-world file transfers

+Transferred files can be viewed and/or compared

- Adds flow control complexity

- Add higher layer acks and retransmissions

- TCP Control algorithms sensitive

to multiple parameters

- Test system configuration can

affect results

11/8/2012

66

5. Can I achieve max E2E tput under ideal conditions

with TCP?

• TCP adds higher layer support for error detection, re-transmissions, congestion control and flow control

• TCP flow control algorithms interpret “lost” packets as congestion

• Careful consideration of parameters such as window size, number of parallel process, segment size etc. need to be considered

TCP “Flapping”

11/8/2012

67

6. What happens if I try a real application? …

(Voice, video, ftp …)

7. What happens under non-ideal conditions?

•Typically fade the DL and use robust

UL

•Perform test mode and E2E testing

•Measure MAC (BLER & Tput) and IP

layer throughput

•Use TCP with care!

11/8/2012

68

8. Is it robust? …

• E2E IP tests PHY, MAC, PDCP, and IP layers all working

together at full rate

• Check processor can handle multiple real time activities – add

SMS and voice calls during E2E IP

• Check there are no memory overflow/leakage issues

9. Does it work closed loop?

•BLER/Tput Testing

•Supports Test Mode and E2E Testing

11/8/2012

69

10. How good is my battery life?

Case StudyCase StudyAutomated Measurements Give Repeatable 21Mbps Results!

11/8/2012

70

Case StudyCase StudyDevice Performance: MIPS Matter!

Case StudyCase StudyCat14 (21Mbps) Devices – Better the second time around

11/8/2012

71

Case StudyCase StudyNot All HSDPA Cat 6 Devices Have the Same Throughput

Final Note

11/8/2012

72

The End

Thank You