Evolutionary trends of mobile systems: from 2G to 5G

Eng. University of Bologna 6-13th October 2017

Enrico BuracchiniTIM_INNOVATION

Systems beyond 3G: LTE & LTE-A

Outline- Part II• LTE

• LTE Advanced

• 5G overview

LTE SI (2004): Rationale & objectivesFROM 3GPP TR 25.913:• … to ensure competitiveness in an even longer time frame, i.e. for the next 10

years and beyond, a long-term evolution of the 3GPP radio-access technology needs to be considered.

• …Important parts of such a long-term evolution include reduced latency, higher user data rates, improved system capacity and coverage, and reduced cost for the operator. In order to achieve this, an evolution of the radio interface as well as the radio network architecture should be considered.

• ….Considering a desire for even higher data rates and also taking into account future additional 3G spectrum allocations the long-term 3GPP evolution should include an evolution towards support for wider transmission bandwidth than 5 MHz. At the same time, support for transmission bandwidths of 5MHz and less than 5MHz should be investigated in order to allow for more flexibility in whichever frequency bands the system may be deployed.

LTE SI (2004): Rationale & objectives FROM 3GPP TR 25.913• The objective of Evolved UTRA and UTRAN is to develop a

framework for the evolution of the 3GPP radio-access technology towards a high-data-rate, low-latency and packet-optimized radio-access technology. Thus the study should focus on supporting services provided from the PS-domain. In order to achieve this, studies should be carried out in at least the following areas:

» Related to the radio-interface physical layer (downlink and uplink):• e.g. means to support flexible transmission bandwidth up to 20 MHz,

introduction of new transmission schemes and advanced multi-antenna technologies

» Related to the radio interface layer 2 and 3:• e.g. signalling optimization

» Related to the UTRAN architecture:• identify the most optimum UTRAN network architecture and functional split

between RAN network nodes, not precluding considerations on the functional split between UTRAN and CN

LTE SI (2004): Rationale & objectivesFROM 3GPP TR 25.913

• The targets for the evolution of the radio-interface and radio-access network architecture should be:

– Significantly increased peak data rate e.g. 100 Mbps (downlink) and 50 Mbps (uplink)

– Increase "cell edge bitrate" whilst maintaining same site locations as deployed today

– Significantly improved spectrum efficiency ( e.g. 2-4 x Release 6)– Possibility for a Radio-access network latency (user-plane UE – RNC (or

corresponding node above Node B) - UE) below 10 ms– Significantly reduced C-plane latency (e.g. including the possibility to

exchange user-plane data starting from camped-state with a transition time of less than 100 ms (excluding downlink paging delay))

– Scalable bandwidth• 5, 10, 20 and possibly 15 MHz• to allow flexibility in narrow spectral allocations where the system

may be deployed

3GPP Requirements of LTE: main ones

RAN

UE

Coverage:5Km: full performance30Km: some degradations100Km: not prevented

DLPeak data rate: 100Mbps

ULPeak data rate: 50Mbps

UL

DL

Mobility:0-15Km/h: optimized15-120Km/h: high performance120-500Km/h: supported

Scalable BW:

1,25; 2,5; 5; 10; 20 MHz

User Plane Latency: 5msControl Plane Latency:50-100 ms

LTE: key enabling technologies

OFDM: Orthogonal Frequency Division Modulation• OFDM as modulation

– Spectrum is divided in several orthogonal sub-carriers : ∆f=1/Ts– Information flow is divided over the sub-carriers– Mo-demodulation by FFT/iFFT

• OFDM as mulitple access (OFDMA)– A group of sub-carriers can be allocated to different users inside the available

bandwidth

ffsingle-carrier mod.

fconventional multi-carrier modulation

O FDM

OFDM: Characteristics

…

Sub-carriersFFT

Time

Symbols

N subcarriers in W Bandwidth

Guard Intervals

…

Frequency

∆f=1/Ts

High resistance to multipath propagation

Low implementation complexity (IFFT/FFT)

Sharp power spectrum decrease at the band edges

Inter-Symbol Interference (ISI) is eliminated at the receiver by removing the cyclic prefix (i.e.

no need for channel equalizers or Rake receivers)

Space-time processing operations performed independently for each sub-carrier (lower

receiver complexity that single carrier transmission)

High Peak to Average Power Ratio (PAPR)

Power amplifiers with high linearity are required (critical issue on the terminal side)

Sensitivity to frequency offset and phase noise

Advantages

Disadvantages

OFDM: pros & cons

In 3GPP Long Term Evolution:– Orthogonal Frequency Division Multiple Access (OFDMA) is to be used in

downlink direction

– Single Carrier Frequency Division Multiple Access (SC-FDMA) is to be used in the uplink direction

OFDM in 3GPP Long Term Evolution

Downlink Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users. The subcarrier spacing in the OFDM downlink is 15 kHz and there is a maximum of 2048 subcarriers available. The transmission is divided in time into time slots of duration 0.5 ms and subframes of duration 1.0 ms. A radio frame is 10 ms long. Supported modulation formats on the downlink data channels are QPSK, 16QAM and 64QAM.

Uplink SC-FDMA was chosen in order to reduce Peak to Average Ratio (PAR), which has been identified as a critical issue for use of OFDMA in the uplink where power efficient user-terminal amplifiers are required. Another important requirement was to maximize the coverage. For each time interval, the base station scheduler assigns a unique time-frequency interval to a terminal for the transmission of user data, thereby ensuring intra-cell orthogonality.

Main Lte L1 parameters

Multi-Antenna techniques

x1

x2

x3

y1

y2

y3

Multiple input multiple output (MIMO) antenna technologies are required to achieve thehigher LTE bit-rate targets.

MIMO is simpler to implement with OFDMA than with CDMAMIMO can be used to provide both spatial multiplexing and spatial diversity

Spatial Multiplexing (more than one data stream)

Spatial Diversity (same stream)

E-UTRAN architecture• The E-UTRAN consists of eNBs, providing the E-UTRA user plane

(PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE.

• The eNBs are interconnected with each other by means of the X2 interface. • The eNBs are also connected by means of the S1 interface to the EPC (Evolved

Packet Core), more specifically to the MME (Mobility Management Entity) by means of the S1-MME and to the Serving Gateway (S-GW) by means of the S1-U.

eNB

MME / S-GW MME / S-GW

eNB

eNBS

1 S1

S1 S1

X2

X2X2

E-UTRAN

E-UTRAN architecture• The E-UTRAN consists of eNBs, providing the E-UTRA user plane

(PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE.

• The eNBs are interconnected with each other by means of the X2 interface. • The eNBs are also connected by means of the S1 interface to the EPC (Evolved

Packet Core), more specifically to the MME (Mobility Management Entity) by means of the S1-MME and to the Serving Gateway (S-GW) by means of the S1-U.

eNB

MME / S-GW MME / S-GW

eNB

eNBS

1 S1

S1 S1

X2

X2X2

E-UTRAN

eNB functionalities

• The eNB hosts the following functions:

Functions for RRM: Radio Bearer Control, Radio Admission Control, Connection MobilityControl, Dynamic allocation of resources to UEs in both uplink and downlink(scheduling)

IP header compression and encryption of user data stream

Selection of an MME at UE attachment

Routing of User Plane data towards S-GW

Scheduling and transmission of paging messages (originated from the MME)

Scheduling and transmission of broadcast information (originated from the MME or O&M)

Measurement and measurement reporting configuration for mobility and scheduling

MME and S-GW functionalities

• The MME hosts the following functions:

Distribution of paging messages to the eNBs

Security control

Idle state mobility control

SAE bearer control

Ciphering and integrity protection of NAS signalling

The Serving Gateway hosts the following functions:

Termination of U-plane packets for paging reasons

Switching of U-plane for support of UE mobility

NAS = Non-Access StratumSAE = System Architecture Evolution

Radio protocol architecture

• User plane: the protocol stack comprises PDCP, RLC, MAC and PHY sublayers (terminated in eNB on the network side) The PDCP, RLC and MAC perform the functions of header compression, ciphering, ARQ, scheduling and HARQ.

Control plane: the protocol stack comprises NAS,(terminated in MME), RRC, PDCP, RLC, MAC and PHYsublayers (terminated in eNB).

eNB

PHY

UE

PHY

MAC

RLC

MAC

PDCPPDCP

RLC

eNB

PHY

UE

PHY

MAC

RLC

MAC

MME

RLC

NAS NAS

RRC RRC

PDCP PDCP

* Details in 3GPP TS 36.300

LTE UE Categories

DLCat. UE Peak Throughput  [Mbit/s] 

@20MHz bandwidthspatial multiplexing 

DL layersCategory 1 10 1

Category 2 50 2

Category 3 100 2

Category 4 150 2

Category 5 300 4

Cat. UE Peak Throughput  [Mbit/s] @20MHz bandwidth

Category 1 5

Category 2 25

Category 3 50

Category 4 50

Category 5 75

UL16-QAM

64-QAM

4 Ant. RX

2 Ant. RX

3GPP

21

Tele

com

Ital

ia s

tric

tlyco

nfid

entia

land

pro

prie

tary

LTE evolution towards LTE Advanced

Rel-15 ??Rel-14 Jun. ‘17?

Rel-13 Mar. ‘16

Rel-12 Mar. ‘15

Rel-11 Mar. ‘13

Rel-10 Jun. ‘11

Rel-9 Mar. ‘10

Rel-8 Mar. ‘09

FDD and TDD mode

Flexible bandwidth (1.4MHz to 20MHz)

DL SU-MIMO (4 layers) and SDMA

UL TX diversity and SDMA

Inter-cell power control and interference management

Inter-eNB and Inter-RAT mobility

HeNB/CSG & SON support

eMBMS

Dual stream beamforming

Positioning

Enhanced HeNB/CSG support

Emergency services

CA (up to 5 CCs)

Enhanced MIMO (8 DL and 4 UL layers)

eICIC

Relays

Enhanced SON & MDT

DL and UL CoMP

In-device coexistence

Enhanced Physical Downlink Control Channel (ePDCCH)

Further eICIC

Small Cells Enhancements

Multi-antenna technology advancements

CoMP operation with non ideal-backhaul

advanced interference suppression techniques at the terminal

Low-cost and long-range for MTC

Device-to-device (D2D)

Carrier Aggregation advancements

LTE/UMTS-WiFi radio interworking

GrazieCarrier Aggregation

23

Tele

com

Ital

ia s

tric

tlyco

nfid

entia

land

pro

prie

tary

Carrier Aggregation

With carrier aggregation (CA), multiple component carriers (CC) are aggregated and jointly used for transmission to/from a single terminal.

Up to five component carriers, possibly each of different bandwidth, can be aggregated, allowing for transmission bandwidths up to 100 MHz.

Each CC can have different bandwidth (1.4, 3, 5, 10, 15, 20 MHz)

However RAN4 discussed conformance test for 5, 10, 15, 20 MHz.

Backwards compatibility is catered for as each CC uses the Rel-8 structure.

Hence, to a release-8/9 terminal each component carrier will appear as an LTE Rel-8 carrier, while a carrier-aggregation capable terminal can exploit the total aggregated bandwidth.

In the general case, a different number of CC can be aggregated for the downlink and uplink.

24

Tele

com

Ital

ia s

tric

tlyco

nfid

entia

land

pro

prie

tary

Carrier Aggregation benefits

Higher speeds: Aggregation of carriers increases spectrum resources, which provides higher speeds across the cell coverage.

Capacity gain: Aggregating multiple carriers increases spectrum but also includes trunking gains from dynamically scheduling traffic across the entire spectrum. This in turn increases cell capacity and network efficiency and improves the experience for all users.

Optimum utilization of an operator’s spectrum resources: The majority of operators have fragmented spectrum covering different bands and bandwidths, Carrier Aggregation helps combine these into more valuable spectrum resource.

25

Tele

com

Ital

ia s

tric

tlyco

nfid

entia

land

pro

prie

tary

Carrier Aggregation types

It should be noted that aggregated component carriers do not need to be contiguous in the frequency domain. Rather, with respect to the frequency location of the different component carriers, three different cases can be identified:

Intra-band aggregation with frequency-contiguous component carriers (rel 10)

Intra-band aggregation with non-contiguous component carriers (rel 11)

Inter-band aggregation with non-contiguous component carriers. (rel 10) => it generated a lot of work to specify different inter band band combination to meet requirements from different operators worldwide

26

555

Lte- Adv: Carrier Aggregation"4GPLUS"

800 MHz

~110 Mbps

55

5 5 5

5551800 MHz

2600 MHz

~110 Mbps

~70 Mbps

5 5 5

555

2600 MHz

+1800 MHz225 Mbps

1800 MHz

(o 2600 MHz)

+800 MHz

180Mbps

55

27

3-Carrier Aggregation

800 MHz 55

5551800 MHz

5 5 52600 MHz

300 Mbps

+

+

800 MHz 55

5 5 5

5551800 MHz

2600 MHz

GrazieMulti antenna Techniques

Multi User MIMO and Higher Order MIMO

29

Tele

com

Ital

ia s

tric

tlyco

nfid

entia

land

pro

prie

tary

► Throughput increment through simultaneous transmission/reception by exploiting an higher number of antennas at both eNB and/or UE

► MIMO 4x4 e 8x8 configurations require radiating systems with increasing dimension and complexity in both the UE side (impacting the device engineering) and the BS side (impacting sites design)

Single User MIMO

Multi User MIMO

MIMO 8x8 with CA on 100MHz

3 Gbps

300 Mbps

MIMO 8x8 on 10MHz

150 Mbps

MIMO 4x4 on 10MHz

75 Mbps

MIMO 2x2 on 10MHz

Multiple Input Multiple Output (MIMO)Configuration evolution

30

Tele

com

Ital

ia s

tric

tlyco

nfid

entia

land

pro

prie

tary

► Nine MIMO Transmission Modes (TM) are available in the 3GPP Rel-10 for LTE downlink (3GPP TS 36.211 and TS 36.213)

► TM 10 was added in Rel’11

DL TX mode Reference TX scheme 3GPP Release

Mode 1 Single antenna transmission LTE Rel.8

Mode 2 Transmit diversity LTE Rel.8

Mode 3 Open loop spatial multiplexing LTE Rel.8

Mode 4 Closed loop spatial multiplexing LTE Rel.8

Mode 5 Multi-user MIMO LTE Rel.8

Mode 6 Single Layer Closed loop precoding LTE Rel.8

Mode 7 Single Layer beamforming LTE Rel.8

Mode 8 Dual Layer beamforming LTE Rel.9

Mode 9 Up to 8 layer transmission LTE-A Rel.10

Mode 10 CoMP transmission LTE-A Rel.11

Coverage

Data throughput

Coverage & Data throughput

The TM can be divided in two main classes

► modes that are used for diversity in order to improve reliability and coverage (TM 2, 6 and 7)

► modes used to improve the peak data rate through the transmission of multiple parallel data layers (TM 3, 4, 5, 8 and 9)

Transmission Mode from LTE to LTE-AThe evolution of multi-antenna techniques in the standard

31

4.5G: CA + MIMO4x4 + High Order Modulations

500 Mbps (and

more…)

500 Mbps (and

more…)

DL 4x4 MIMODL 4x4 MIMO

256 QAM256 QAMCarrier Aggregation

Carrier Aggregation

+ 33% Throughput

QPSK

16 QAM

2 bits per symbol

4 bits per symbol

64 QAM6 bits per symbol

256QAM8 bits per symbol

+ 50% Throughput

+ 100% Throughput

4x Multiplexing Gain2x Gain wrt to DL MIMO2x2

Thanks for your kind attention