00_NSN_LTE_Presentation_PlanningTeam_May12-2013.pdf

LTE fundamentals and system architect Ahmad Talaat NSN Saudi - NPO

Contents • LTE Drivers • LTE Main Requirements • Network Architecture Evolution • Key Features and Basics • LTE Network Architecture • Highlight on some Important NSN Features

Contents • LTE Drivers • LTE Main Requirements • Network Architecture Evolution • Key Features and Basics • LTE Network Architecture • Highlight on some Important NSN Features

The way to the Long-Term Evolution (LTE): a 3GPP driven initiative

•LTE is 3GPP system for system for the years 2010 to 2020 & beyond. beyond.

•It shall especially compete with WiMAX 802.16e/m •It must keep the support for high & highest mobility users mobility users like in GSM/UMTS networks

•The architectural changes are changes are big compared to UMTS

•LTE commercial launch has launch has started early 2010.

LTE Drivers Wireline Evolution: pushes higher data rates

Wireless Data extensively used: Pushes more capacity

Driving to clear LTE Targets

Other Wireless technologies: Competition pushes new capabilities

Flat Rate pricing: pushes cost efficiency efficiency

What are the LTE challenges? The Users’ expectation…

..leads to the operator’s challenges

• Best price, transparent flat rate • Full Internet • Click-bang responsiveness

• reduce cost per bit • provide high data rate • provide low latency

User experience will have an impact on ARPU

Price per Mbyte has to be reduced to remain profitable

Throughput

Latency Cost per MByte

HSPA

LTE

HSPA

LTE

UMTS

HSPA

I-HSPA I-H SPA

LTE

LTE: lower cost per bit and improved end user experience

Reduction of network cost is necessary to remain profitable Revenues and Traffic decoupled Traffic   e   m   u    l   o   v   c    i    f    f   a   r    T

Revenue

Profitability

   t    i    b    /        €

Network cost

Time

Voice dominated Source: Light Reading (adapted)

Data dominated

Contents • LTE Drivers • LTE Main Requirements • Network Architecture Evolution • Key Features and Basics • LTE Network Architecture • Highlight on some Important NSN Features

LTE = Long Term Evolution • Next step for

GSM/WCDMA/HSPA and CDMA

 A true global roaming technology

• Peak data rates of 303 Mbps / 75 Mbps

Enhanced consumer experience

• Low latency 10-20 ms • Scalable bandwidth of 1.4 – 20 MHz

Easy to introduce on any frequency band

• OFDM technology • Flat, scalable IP based architecture

Decreased cost / GB

Schedule for 3GPP releases

• Next step for

 A true global roaming technology

GSM/WCDMA/HSPA and cdma2000 Specification UMTS/ WCDMA

HSDPA IMS

HSUPA MBMS WLAN IW

HSPA+ LTE Studies

LTE & EPC

LTE-A studies

LTE-A

3GPP Rel. 99/4

Rel. 5

Rel. 6

Rel. 7

Rel. 8

Rel. 9

Rel. 10

2003

2005

2000

2007

2008

2009

2011

year

•

LTE have been developed by the same standardization organization. The target has been simple multimode implementation and backwards compatibility.

•

HSPA and LTE have in common:

 –  –

Sampling rate using the same clocking frequency Same kind of Turbo coding

•

The harmonization of these parameters is important as sampling and Turbo decoding are typically done on hardware due to high processing requirements.

•

WiMAX and LTE do not have such harmonization. LTE-A: LTE-Advanced

Comparison of Throughput and Latency (1/2)

• Peak data rates of

Enhanced consumer experience:

303 Mbps / 75 Mbps

- drives subscriber uptake - allow for new applications

• Low latency 10-20 ms

- provide additional revenue streams

Max. peak data rate 350 300 250

Downlink Uplink

  s   p 200    b    M

Latency (Rountrip delay)*

150

GSM/ EDGE

100

HSPA Rel6

50 0 HSPA R6

Evolved HSPA (Rel. 7/8, 2x2 MIMO)

LTE 2x20 MHz (2x2 MIMO)

LTE 2x20 MHz (4x4 MIMO)

HSPAevo (Rel8) LTE min max

0

20

40

60

80

100

120

140

160

180

DSL (~20-50 ms, depending on operator) * Server near RAN

200 ms

Scalable Bandwidth Scalable bandwidth

Easy to introduce on any frequency band: Frequency Refarming (Cost efficient deployment on lower

• Scalable bandwidth of 1.4 – 20 MHz

frequency bands supported) Urban 2.6 GHz

LTE UMTS

2.1 GHz

or 2.6 GHz

LTE

2006

LTE

UMTS

2.1 GHz 2008

2010

2012

2014

2016

2018

2020

Rural UMTS

900 MHz GSM

LTE

or

2006

LTE

GSM

900 MHz

2008

2010

2012

2014

2016

2018

2020

Increased Spectral Efficiency LTE efficiency is 3 x HSPA R6 in downlink HSPA R7 and WiMAX have Similar Spectral Efficiency

• OFDMA technology increases Spectral efficiency

• All cases assume 2-antenna terminal reception • HSPA R7, WiMAX and LTE assume 2-antenna BTS transmiss ion (2x2 MIMO) 2.0 1.8 1.6

Downlink Uplink

ITU contribution from WiMAX Forum shows DL 1.3 & UL 0.8 bps/Hz/cell

1.4       l       l      e      c 1.2       /      z 1.0       H       /      s      p0.8       b 0.6 0.4

Reference:

0.2

- HSPA R6 and LTE R8 from 3GPP R1-071960

0.0

- HSPA R6 equalizer from 3GPP R1-063335

HSPA R6

HSPA R6 + UE equalizer 

HSPA R7

WiMAX

LTE R8

- HSPA R7 and WiMAX from NSN/Nokia simulations

Reduced Network Complexity

• Flat, scalable IP based architecture

Flat Architecture: 2 nodes architecture IP based Interfaces

Flat, IP based architecture Access

Core

Control

MME

IMS

HLR/HSS

Internet Evolved Node B

Gateway

LTE/SAE Requirements Summary 1.

Simplify the RAN: - Reduce the number of different types of RAN nodes, and their complexity. - Minimize the number of RAN interface types.

2.

Increase throughput: Peak data rates of UL/DL 50/100 Mbps

3.

Reduce latency (prerequisite for CS replacement).

4.

Improve spectrum efficiency: Capacity 2-4 x higher  than with Release 6 HSPA

5.

Frequency flexibility & bandwidth scalability: Frequency Refarming

6.

Migrate to a PS only domain in the core network: CSFB for initial phase

7.

Provide efficient support for a variety of different services. Traditional CS services will be supported via VoIP, etc: EPS bearers for IMS based Voice

8.

Minimise the presence of single points of failure in the network above the eNBs S1Flex interface

9.

Support for inter-working with existing 3G system & non-3GPP specified systems.

10. Operation in FDD & TDD modes 11. Improved terminal power efficiency  A more detailed list of the requirements and objectives for LTE can be found in TR 25.913.

Contents • LTE Drivers • LTE Main Requirements • Network Architecture Evolution • Key Features and Basics • LTE Network Architecture • Highlight on some Important NSN Features

NSN Network Architecture Evolution (1/4) 3GPP Rel 6 / HSPA Internet Node B

RNC

SGSN

GGSN User plane Control Plane

• Original 3G architecture. • 2 nodes in the RAN. • 2 nodes in the PS Core Network. • Every Node introduces additional delay. • Common path for User plane and Control plane data. • Air interface based on WCDMA. • RAN interfaces based on ATM. • Option for Iu-PS interface to be based on IP.

NSN Network Architecture Evolution (2/4) 3GPP Rel 7 / HSPA

SGSN GGSN

Internet Node B

RNC

Direct tunnel User plane Control Plane

• Separated path for Control Plane and User Plane data in the PS Core Network.

• Direct GTP tunnel from the GGSN to the RNC for User plane data: simplifies the Core Network and reduces Signalling.

• First step towards a flat network Architecture. • 30% core network OPEX and CAPEX savings with Direct Tunnel. • The SGSN still controls traffic plane handling, performs session and mobility management, and manages paging.

• Still 2 nodes in the RAN.

NSN Network Architecture Evolution (3/4) 3GPP Rel 7 / Internet HSPA

SGSN GGSN

Internet Node B (RNC Funct.)

Direct tunnel User plane Control Plane

• I-HSPA introduces the first true flat architecture to WCDMA. • Standardized in 3GPP Release 7 as: “Direct Tunnel with collapsed RNC”.

• Most part of the RNC functionalities are moved to the Node B. • Direct Tunnels runs now from the GGSN to the Node B. • Solution for cost-efficient broadband wireless access. • Improves the delay performance (less node in RAN). • Deployable with existing NSN WCDMA base stations. • Transmission savings

NSN Network Architecture Evolution (4/4) 3GPP Rel 8 / LTE

MME SAE GW

Internet Evolved Node B

Direct tunnel User plane Control Plane

• LTE takes the same Flat architecture from Internet HSPA. • Air interface based on OFDMA. • All-IP network. • New spectrum allocation (i.e 2600 MHz band) • Possibility to reuse spectrum (i.e. 900 MHZ)

NSN Network Architecture Evolution - Summary 3GPP Rel 6 / HSPA Internet Node B

RNC

3GPP Rel 7 / HSPA

SGSN

GGSN

SGSN GGSN

Internet Node B

3GPP Rel 7 / Internet HSPA

RNC

Direct tunnel SGSN GGSN

Internet Node B (RNC Funct.)

3GPP Rel 8 / LTE

Direct tunnel MME SAE GW

Internet Evolved Node B

Direct tunnel

Contents • LTE Drivers • LTE Main Requirements • Network Architecture Evolution • Key Features and Basics • LTE Network Architecture • Highlight on some Important NSN Features

LTE Radio Interface Key Features LTE Radio Access Network (EUTRAN)

Evolved Packet Core (EPC) SAE-GW MME

eNode-B

Serving GW

PDN GW

LTE Radio Interface Key Features

• Retransmission Handling (HARQ/ARQ) • Spectrum Flexibility • FDD & TDD modes • Multi-Antenna Transmission • Frequency and time Domain scheduling • Uplink (UL) Power Control

Packet Data Network

EUTRAN Key Features LTE Radio Access Network (EUTRAN)

Evolved Packet Core (EPC) SAE-GW MME

eNode-B

Serving GW

EUTRAN Key Features: • Evolved NodeB • IP transport layer • UL/DL resource scheduling • QoS Awareness • Self-configuration

PDN GW

Packet Data Network

EPC Key Features LTE Radio Access Network (EUTRAN)

Evolved Packet Core (EPC) SAE-GW MME

eNode-B

Serving GW

PDN GW

EPC Key Features: • IP transport layer • QoS Awareness • Packet Switched Domain only • 3GPP (GTP) or IETF (MIPv6) option • Prepare to connect to non-3GPP access networks

Packet Data Network

Multiple Access Methods

• Frequency Division

• Time Division

User 3

User ..

OFDMA

CDMA

TDMA

FDMA

User 2

User 1

• Frequency Division

• Code Division

• Orthogonal subcarriers

f

t

t

t

f

f

f

f

f

t

f

OFDM is the state-of-the-art and most efficient and robust air interface

f

The Rectangular Pulse Fourier Transform Time Domain

  e    d   u    t    i    l   p   m   a

  f   s 

Ts

  y    t    i   s   n   e    d   r   e   w   o   p    l   a   r    t   c   e   p   s

1

T  s

time

Inverse Fourier Transform

Frequency Domain

f s

frequency f/f s

 Advantages: + Simple to implement: there is no complex filter system required to detect such pulses and to generate them. + The pulse has a clearly defined duration. This is a major advantage in case of multipath propagation environments as it simplifies handling of inter-symbol interference.

Disadvantage: - it allocates a quite huge spectrum. However the spectral power density has null points exactly at multiples of the frequency fs = 1/Ts. This will be important in OFDM.

Air Interface - OFDM Basics • Data is sent in parallel across the set of subcarriers, each subcarrier only transports a part of the whole transmission

• The throughput is the sum of the data rates of each individual (or used) subcarriers while the power is distributed to all used subcarriers

• FFT ( Fast Fourier Transform) is used to create the orthogonal subcarriers. The number of subcarriers is determined by the FFT size ( by the bandwidth) Power

bandwidth

frequency

The OFDM Signal

OFDMA Parameters in LTE • Channel bandwidth: DL bandwidths ranging from 1.4 MHz to 20 MHz • Data subcarriers: the number of data subcarriers varies with the bandwidth  – 72 for 1.4 MHz to 1200 for 20 MHz

Resource Block and Resource Element • Physical Resource Block PBR or  Resource Block RB:  – 12 subcarriers in frequency domain x 1 slot period in time domain  – Capacity allocation based on Resource Blocks Subcarrier 1

0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6

  z    H    K    0    8    1

0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6

Resource Element RE:  – 1 subcarrier x 1 symbol period  – theoretical min. capacity allocation unit  – 1 RE is the equivalent of 1 modulation symbol on a subcarrier, i.e. 2 bits (QPSK), 4 bits (16QAM), 6 bits (64QAM).

0 1 2 3 4 5 6 0 1 2 3 4 5 6

Subcarrier 12 0 1 2 3 4 5 6 0 1 2 3 4 5 6 1 slot

1 slot

1 ms subframe

Resource Element

Physical Resource Blocks

12 subcarriers ..

•

 In both the DL & UL direction, data is allocated to users in terms of resource blocks (RBs).

•

a RB consists of 12 consecutive subcarriers in the frequency domain, reserved for the duration of 0.5 ms slot.

•

The smallest resource unit a scheduler can assign to a user is a scheduling block which consists of two consecutive resource blocks

.. Frequency Resource block

1 ms subframe or TTI

0.5 ms slot Time

During each TTI, resource blocks for different UEs are scheduled in the eNodeB

LTE Channel Options

Bandwidth options: 1.4, 1.6, 3, 3.2, 5, 10, 15 and 20 MHz

Subcarriers in frequency domain (15 kHz or 7.5 kHz subcarrier spacing)

Channel bandwidth (MHz)

1.4

3

5

10

15

20

Number of subcarriers

72

180

300

600

900

1200

Number of resource blocks

6

15

25

50

75

100

LTE RRM: Scheduling

• Motivation  – Bad channel condition avoidance

CDMA

OFDMA

Single Carrier transmission does not allow to allocate only particular frequency parts. Every fading gap effects the data.

The part of total available channel experiencing bad channel condition (fading) can be avoided during allocation procedure.

Contents • LTE Drivers • LTE Main Requirements • Network Architecture Evolution • Key Features and Basics • LTE Network Architecture • Highlight on some Important NSN Features

Network Architecture Evolution HSPA

Direct tunnel

I-HSPA

LTE

HSPA R6

HSPA R7

HSPA R7

LTE R8

GGSN

GGSN

GGSN

SAE GW

SGSN

RNC Node B (NB)

SGSN

SGSN

MME/SGSN

RNC Node B (NB)

Node B + RNC Functionality

• Flat architecture: single network element in user plane in radio network and core network

Evolved Node B (eNB)

User plane Control Plane

Evolved Packet System (EPS) Architecture - Subsystems • The EPS architecture goal is to optimize the system for packet data transfer. • There are no circuit switched components. The EPS architecture is made up of:  –  EPC: Evolved Packet Core, also referred as SAE  –  eUTRAN: Radio Access Network, also referred as LTE EPS Architecture LTE or eUTRAN

SAE or EPC

•

EPC provides access to external packet IP networks and performs a number of CN related functions (e.g. QoS, security, mobility and terminal context management) for idle and active terminals

•

eUTRAN performs all radio interface related functions

LTE/SAE Network Elements Main references to architecture in 3GPP specs.: TS23.401,TS23.402,TS36.300

Evolved UTRAN (E-UTRAN)

Evolved Packet Core (EPC) HSS

eNB Mobility Management Entity

Policy & Charging Rule Function

S6a

MME

X2

S10

S7

Rx+ PCRF

S11 S5/S8

S1-U LTE-Uu

LTE-UE

Evolved Node B (eNB)

Serving Gateway

SGi

PDN Gateway SAE Gateway

PDN

Contents • LTE Drivers • LTE Main Requirements • Network Architecture Evolution • Key Features and Basics • LTE Network Architecture • Highlight on some Important NSN Features

UL Physical Resource Block: DRS & SRS • The Demodulation Reference Signal is transmitted in the third SC-FDMA symbol (counting from zero) in all resource blocks allocated to the PUSCH carrying the user data.

12 subcarriers ..

.. Frequency 1 ms subframe or TTI

• This signal is needed for channel estimation, which in turn is essential for coherent demodulation of the UL signal in the eNodeB.

0.5 ms slot Time Sounding Reference Signal on last OFDM symbol of 1 subframe; Periodic or aperiodic transmission

Demodulation Reference Signal in subframes that carry PUSCH

• The Sounding Reference Signal

PUCCH: Physical UL Control Channel

SRS provides UL channel quality information as a basis for scheduling decisions in the base station. This signal is distributed in the last SC-FDMA symbol of subframes that carry neither PUSCH nor PUCCH data. [SRS is always disabled in FDD RL30 and before.]

RL30

Uplink Scheduler IAS: Interference Aware Scheduler UL Improvement in UL coverage by optimizing the cell edge performance

• Flexi eNodeB takes into account the noise and interference measurements together with the UE Tx power density (= UE TX power per PRB) when allocating PRBs in the frequency domain

• Cell edge users are assigned to frequency sub-bands with low measured inter-cell interference

• Up to 10% gain for cell edge users in low and medium loaded networks • Easier to implement than channel aware scheduling (no sounding reference signal used)

High Tx power density indicates cell edge users / strong interferers

eNode B measured interference

PRBs subband with high interference subband with low interference subband with medium interference

Feature ID(s): LTE619

RL40

LTE46, UL Channel Aware Scheduling • Channel Unaware Scheduling (CUS)  – random allocation of PRBs => averaging of inter-cell interference  – simple and robust, no UL channel sounding required  –  no FDPS gain • Interference Aware Scheduling (IAS, LTE619)  – rudimentary interference reduction via coarse segmentation  – scheduling criterion based on Tx power density =>Tx power per PRB  – no UL channel sounding required  – lower FDPS gain than CAS, LTE46 • Channel Aware Scheduling (CAS, LTE46)  – very similar implementation in RL15 and RL40  – sophisticated SRS- and PUSCH-based PRB allocation according to UE specific channel state information (CSI)

 –  –

 UL channel sounding required FDPS gain (low for a high # of PRBs allocated to a specific UE

)

LTE RRM: Connection Mobility Control Handover Types • Intra-RAT handover  – Intra eNodeB and Inter eNodeB handover  –  Above handovers can also be Inter-frequency handovers (RL20) i.e. to support different frequency bands and deployments within one frequency band but with different center frequencies

 – Data forwarding over X2 for inter eNodeB HO  – HO via S1 interface (RL20): HO in case of no X2 interface configured between serving eNB and target eNB

• Inter-RAT handover  – LTE to WCDMA: RL30  – WCDMA to LTE: RL40  – LTE to CDMA2000: RL40 (CDMA2000 to LTE not assigned)  – LTE  GSM and GSM  LTE: not assigned

Intra frequency handover via X2  A reliable and lossless mobility • Basic Mobility Feature • Event triggered handover based on DL measurements (ref. signals)

• Network evaluated HO decision • Operator configurable thresholds for • coverage based & • best cell based handover

• Data forwarding via X2 • Radio Admission Control (RAC) gives priority to HO related access over other scenarios

S1

X2

S-GW

MME

P-GW S1

Feature ID(s): LTE53

RL20

Intra LTE Handover via S1 Extended mobility option to X2 handover • Handover in case of • no X2 interface between eNodeBs, e.g. multi-vendor scenarios • eNodeBs connected to different CN elements • Operator configurable thresholds for • coverage based (A5) and • best cell based (A3) handover • DL Data forwarding via S1 •  Admission Control gives priority to HO related access over other scenarios

• Blacklists

RL20

Inter Frequency Handover Multi-band mobility • Network controlled • Event triggered based on DL measurement RSRP and RSRQ

• Inter frequency measurements triggered by events A1/A2

• Operator configurable thresholds for coverage based (A5), best cell based (A3) handover

• Service continuity for LTE deployment in different frequency bands as well as for LTE deployments within one frequency band but with different center frequencies • Blacklists Feature ID(s): LTE55

RL30

Inter RAT Handover to WCDMA • Coverage based inter-RAT PS handover • Only for multimode devices supporting LTE and WCDMA

• Event triggered handover based on DL measurement RSRP (reference signal received power)

• Operator configurable RSRP threshold • Network evaluated HO decision • Target cells are operator configurable •  An ANR functionality may be applied optionally

• Blacklisting • eNB initiates handover via EPC

Feature ID(s): LTE56

RL30

eNACC to GSM Network Assisted Cell Change to GSM Service continuity to GSM • Network change from LTE to GSM in RRC Connected Mode when LTE coverage (RSRP) is ending

• Prior to actual reselection process the measurements of 2G network are triggered

• Only applicable for NACC capable devices

• Inter RAT measurements triggered by events A1/A2

• Operator configurable handover threshold (event B2)

• Target cells for IRAT measurements can be configured by the operator

• Blacklisting of target cells is supported

LTE735: RRC Connection Reestablishment  Advanced failure handling • eNode B takes UE back to RRC

S-GW MME

CONNECTED

• UE initiated procedure • Typical scenarios: • Radio link failures (e.g. T310 expires)

• Handover failure (e.g. T304 expires)

• RRC connection reconfiguration failure

UE reverts back to source cell due to handover failure

RL30

Automated Neighbor Relation (ANR) Configuration •

Neighbour relations are important as wrong neighbour definitions cause HO failures and dropped calls Self configuration of relations avoids manual planning & maintenance

•

ANR covers 4 steps: 1)

Neighbour cell discovery

2)

Neighbour Site’s X2 transport configuration discovery (i.e. Neighbour Site IP@)

3)

X2 Connection Set-up with neighbour cell configuration update

4)  ANR Optimization

•

The scope within ANR is to establish an X2 connection between source and target nodes and for that it is necessary that source eNB knows the target eNB IP@

•

How the source eNB gets the IP@ differentiates the ANR features:  –

Central ANR (RL10)

 –

 ANR (RL20)

 –

 ANR- Fully UE based (RL30)

3GPP ANR Configuration Principle Neighbor

Site

Site

UE

eNB - B

connected

MME

eNB - A

New cell discovered New cell identified by ECGI

S1 : Request X2 Transport Configuration (ECGI)

relays request

S1: Request X2 Transport Configuration CM S1: Respond X2 Transport Configuration (IP@) relays response

S1 : Respond X2 Transport Configuration (IP@) CM Add Site & Cell parameter of eNB-A

X2 Setup : IPsec, SCTP, X2-AP [site & cell info] CM

CM Neighbor Cell Tables in both eNB updated

Add Site & Cell Parameter of eNB-B