LTE, WiMAX and 4G

Mobile Communication and Mobile Computing

Prof. Dr. Alexander Schill

http://www.rn.inf.tu-dresden.de

Department of Computer Science Institute for System Architecture, Chair for Computer Networks

LTE: Characteristics

•  LTE = Long Term Evolution •  European implementation of IMT (International Mobile

Telecommunications) by ETSI (European Telecommunication Standards Institute)

•  Packet oriented propagation only •  High data rates

-  Up to 300 Mbit/s Downlink -  Up to 75 Mbit/s Uplink

•  Flexible frequency assignment -  About 40 frequency ranges -  Varying frequency blocks (1.4, 3, 5, 10 and 20 MHz)

•  small latency of 5ms between mobile phone and conventional telephone network

•  optimized for travelling speeds of up to 15 km/h (but up to 500km/h possible with reduced quality)

2

LTE – User Equipment

•  Examples of LTE-enabled devices -  iPhone, Samsung Galaxy LTE,

Samsung LTE Stick •  Five device categories

Category   1   2   3   4   5  

Peak  data  rate  Mbit/s  

DL   10   50   100   150   300  

UL   5   25   50   50   75  

RF  bandwidth   20  MHz  

ModulaAon   QPSK,  16QAM   QPSK,  16QAM,  64QAM  

2  Rx  diversity   Assumed  in  performance  requirements  

2x2  MIMO   Not  supported  

Mandatory  

4x4  MIMO   Not  supported   Mandatory   3

LTE: Frequency bands

•  Germany (currently) -  5 bands: 800 MHz, 900 MHz, 1800 MHz, 2000 MHz, 2600MHz -  Rural Areas -  800 MHz

-  Urban Areas -  800 MHz -  1800 MHz -> partially reassignment from GSM

-  2600 MHz for crowded areas in cities (stations, shopping malls, etc.)

•  USA: 700MHz, 1700MHz and 2100 MHz •  Europe: 800 MHz and others •  Bands 700, 800, 1800 and 2600 MHz will potentially

allow world wide roaming in the future

4

LTE: German frequency bands

•  frequency spectrum of the digital dividend: better building penetration & propagation features > higher range

•  frequency spectrum of the IMT extension band: Enough blocks for 20 MHz bandwidth > Higher data rate

5

Duplex gap* 12 MHz 820 MHz 832 MHz

5 MHz frequency block

(72 Mhz) 790 MHz 862 MHz

10 x 5 MHz blocks uncoupled 2570 MHz 2620 MHz

5 MHz frequency block

(190 Mhz) 2500 MHz 2690 MHz

* The Duplex gap is meant as a fallback position for wireless production technology.

LTE – Reference Architecture

UE eNodeB S-GW P-GW

MME

LTE - Uu S1-U S5/S8

S1-MME S11

HSSS6a

PCRF

Gx

SGiPSTN

eUTRAN Core Network

•  NodeB + RNC (3G) merged into `evolved NodeB´ (eNodeB) •  Core network -  Serving Gateway (S-GW) -  Mobility Management Entity (MME) -  PDN (Packet Data Network) Gateway (P-GW) -  Home Subscriber Server (HSS) -  Policy Control and Charging Rules Function (PCRF) 6

Tasks of eNodeB: Overview

•  eNodeB manages one or several cells

•  Major tasks: -  IP header compression -  Encryption -  Radio resource

management -  Connectivity to core

network -  Bearer management -  UE mobility

Core Network

E-UTRAN

eNodeB

eNodeB

eNodeB

MME S-GW MME S-GW

comm. between eNodeBs

signaling to MMEs bearer path

7

LTE: TDD and FDD

•  two versions of LTE provide solutions for coupled/uncoupled frequency blocks

•  transmitted signals divided into subframes (time units of 1 ms) •  FDD (Frequency division duplex) -separated frequency blocks for UL/DL •  TDD (Time division duplex) – one frequency block alternately used for

UL/DL: - Downlink subframes, Uplink subframes and Special Frames -  “Special Frame” = one subframe for each switching from down to up

link; contains DwPTS (Downlink Pilot Timeslot), GP (Guard Period – avoids overlay of sent and received messages) and UpPTS (Uplink Pilot Timeslot)

8

subframe = 1 millisecond

0 5 4 3 2 1 6 9 8 7

Uplink (UL)

Downlink (DL)

0 5 4 3 2 1 6 9 8 7

Uplink (UL)

Downlink (DL)

Special Frame

DwPTS Guard Period

UpPTS

FDD

TDD

LTE: Use of OFDM for Multiplexing

LTE transmission is based on OFDM (Orthogonal frequency-division multiplexing)

•  in OFDM data is distributed over a large number of closely spaced orthogonal subcarriers -  (two subcarriers are orthogonal if the maximum amplitude of one

subcarrier is reached while the other subcarriers amplitude is zero) -  Subcarriers modulated with conventional modulation scheme (QAM)

•  Pro: robust against interference because interference on subcarrier does not influence the whole frequency band, improved spectrum efficiency and lower bandwidth demand with OFDM

•  Con: expense for coding and decoding and therefore the power consumption increases with the number of subcarriers

9

OFDM with 3 subcarriers

f f

FDM with 3 subcarriers

LTE: Specific enhancements of OFDM

LTE uses specific enhancements of OFDM with a focus on efficient simultaneous access of multiple users:

OFDMA (Orthogonal frequency-division multiple access)

for Down Link •  subsets of subcarriers are assigned to individual users, so

simultaneous (lower data rate) transmissions are enabled for several concurrent users on the same subcarrier

SC-FDMA (Single Carrier FDMA) for Up Link •  multiple access on the same carrier realized by insertion

of user-specific coefficients by the sender before Fourier transformation, and respective decoding by the receiver (roughly comparable to CDMA). More energy-efficient for battery-driven mobile devices.

10

LTE Bearer

UE P-­‐GWeNodeB S-­‐GW

UL-TFT

Application/service  layer

UL-­‐TFT

DL-TFT

DL-TFT

Radio  bearer S1  bearer S5/S8  bearer

RB-­‐ID  <-­‐-­‐>  S1-­‐TEID S1-­‐TEID  <-­‐-­‐>  S5/S8-­‐TEID

•  Different QoS requirements of applications (VoIP, browsing, file download) are mapped to bearers

•  Bearers cross multiple interfaces, each part is individually mapped to lower layer bearer with own bearer id

•  Each node manages binding between bearer ids •  Packet filters (Traffic Flow Templates (TFT)) assign IP packets to bearers

(e.g. based on IP header information and TCP port numbers) 11

Standardized QoS class identifier for LTE

QCI   Resource  Type  

Priority   Packet  Delay  Budget(ms)  

Packet  Error  Loss  Rate  

Example  Service  

1   GBR   2   100   10-­‐2   ConversaAonal  voice  

2   GBR   4   150   10-­‐3   ConversaAonal  video  (live  streaming)  

3   GBR   5   300   10-­‐6   Non-­‐conversaAonal  video  (buffered  streaming)  

4   GBR   3   50   10-­‐3   Real-­‐Ame  gaming  

5   Non-­‐GBR   1   100   10-­‐6   IMS  signaling  

6   Non-­‐GBR   7   100   10-­‐3   Voice,  video  (live  streaming),  interacAve  gaming  

7   Non-­‐GBR   6   300   10-­‐6   Video  (buffered  streaming)  

8   Non-­‐GBR   8   300   10-­‐6   TCP-­‐based  (for  example,  WWW,  e-­‐mail),  chat,  FTP,  p2p  file  sharing,  progressive  video  and  others  

9   Non-­‐GBR   9   300   10-­‐6  

GBR … guarantied bit rate, IMS … IP Multimedia Subsystem 12

LTE Interworking

UE E-UTRAN S-GW P-GW

MME

LTE - Uu S1-U S5/S8

S1-MMES11

3G-SGSN

S3 S4

non-3GPP networks (CDMA2000, WiMAX,…)

UTRAN(GSM, UMTS)

•  Interworking and mobility with other 3GPP defined networks as well as non-3GPP defined networks

•  Service Gateway (S-GW) is mobility anchor for other 3GPP networks

13

LTE Advanced

•  Specified as LTE Release 10 •  Improved performance

-  Data rate up to 1 GBit/s -  End-to-end delay 20 – 30 ms

•  Enhancements -  Carrier aggregation -  up to 5 * 20 MHz -> 100MHz -  Possible in contiguous and non-contiguous spectrum allocations

-  Multiple Input, Multiple Output (MIMO) -  Up to 4 LTE antennas in LTE devices to use MIMO also for Uplink -  Base stations can be equipped with up to 8 antennas

-  Support for relay node base stations -  Additional intermediate base stations -  Improve signal quality at cell borders

-  Support of low power nodes for picocells and femtocells (extremely small cells) for crowded areas

14

WiMAX / IEEE 802.16

•  WiMAX: Worldwide Interoperability for Microwave Access, standardized by IEEE 802.16 and WiMAX-Forum (large industry consortium)

•  IEEE 802.16 FBWA (Fixed Broadband Wireless Access) initially was an alternative for broadband cable services like DSL; frequency range: 10-66 GHz, in assumption of LOS (line of sight)

•  Enhancement IEEE 802.16a; frequency band: 2-11 GHz, NLOS (non line of sight)

•  Enhancement IEEE 802.16e: MBWA (Mobile Broadband Wireless Access); frequency band: 2-6 GHz, NLOS

•  Enhancement IEEE 802.16m: Mobile High Speed Communication; projected for up to 1 Gbit/s

15

WiMAX/IEEE 802.16: overview

Standard 802.16 802.16a 802.16e 802.16m Spectrum, GHz 10-66 2-11 2-6 2-6

LOS-condition LOS NLOS NLOS NLOS Bit rate, MBit/s 32-134 up to 75 up to 100 up to 1000

(theoretical) Range, km up to 5

up to 50 (cellular)

2-5 2-5

Channel bandwith, MHz

20, 25 and 28

Variable: 1,5–20

1,5 -20 1,5-20

Modulation QPSK, 16QAM, 64QAM

OFDM, QPSK,

16QAM, 64QAM

OFDM, QPSK, 16QAM, 64QAM

OFDM, QPSK, 16QAM, 64QAM,

128QAM

16

(N)LOS – (Non) Line-of-Sight

WiMAX: Frequencies worldwide

17

For Germany especially: 3,41-3,452 GHz and 3,51-3,552 GHz

WiMAX: Modulation

18

•  WiMAX: strong dependency of applicable modulation technique on effective channel capacity, spectrum efficiency, range, signal-noise-ratio:

•  BPSK – Binary Phase Shift Keying

•  QPSK – Quadrature Phase Shift Keying

•  16QAM – Quadrature Amplitude Modulation

•  64QAM – Quadrature Amplitude Modulation

(typical example distribution (percentage) of users in different coverage areas)

802.16 Medium Access

•  TDMA (Time Division Multiple Access) -  Each communication channel gets fixed slot for data

transmission •  DAMA (Demand Assigned Multiple Access) -  2 Phases: -  Reservation: every station tries to acquire slot for

each transmission phase (collision possible) -  Data transmission: within reserved slot guaranteed

collision free transmission •  Duplex connection -  FDD (Frequency Division Duplex): simultaneous use of

different frequencies -  TDD (Time Division Duplex): Switching between up-

and downlink on the same frequency

19

WiMAX: Cellular backbone

20

Network

Point to Point Backbone

Point to Multipoint

WiMAX cell

UMTS cell

802.16 PHY 802.16

OFDM-PHY e.g Gigabit

Ethernet

1)  Last Mile (point to point) or 2)  Point to Multipoint network •  Base Station (BS) is the central point for the

Mobile Stations (MS) •  Sending in Downlink-direction: Broad-, Multi-, Unicast •  Connection of a MS to BS is characterized via Channel ID (CID),

-  Channel id gives the possibility for the BS to receive multicast messages

802.16 Network topologies

21

MS/BS

MS/BS

BS

MS

MS MS MS

Network

802.16 Network topologies

3) Mesh network •  MS can communicate directly •  Mesh BS: connected with a network outside the mesh •  other differentiation

-  neighbor: direct connection to a node -  neighborhood: all other neighbors -  extended neighborhood: remote neighborhoods

22 Mesh MS

Mesh BS

Mesh MS Mesh MS

Mesh MS

Mesh MS Mesh MS Network

MBWA (Mobile Broadband Wireless Access); 802.20

•  Working Group 802.20 originated from 802.16

-  goal: Specification of PHY and MAC for Packet-based MBWA-System

-  Should close the gap between WLAN and slower but highly mobile networks (UMTS)

-  But never reached operational state, so practically not relevant anymore

•  Summary: Overall judgement of WiMAX -  Interesting approach especially for last mile in remote

neighborhoods with weakly developed infrastructure

-  However, even in such areas, 3G and 4G are emerging, and also due to lack of flexible and affordable end devices, WiMAX is strongly declining 23

UMTS/HSPA/HSPA+ WiMAX MBWA LTE (advanced)

Mobility Handover, Roaming ---------------- Handover, Roaming, Mobile IP ---

Max Speed 300 km/h 120 km/h 300 km/h 500 km/h

Switching type circuit and packet ---------------- Packet switching ----------------

Peak data rates Down Link

2/14,4/28 Mbit/s (5MHz channel)

365 Mbit/s (2x 20MHz channel, variations)

– 100 - 300 Mbit/s (1.4-20 MHz channel)

Cell sizes pico(1)-, micro(2)-, macro(3)-cells variable

pico(1)-, micro(2)-, macro(3)-cells

pico(1)-, micro(2)-, macro(3)-cells

QoS End-to-end QoS Different classes

End-to-end QoS Different classes

End-to-end QoS

End-to-end QoS Different classes

Scalability ---------------- variable data rate ~ Multiple users per BS --------------

Air Interface CDMA adaptive Modulation MIMO

OFDM(A), adaptive Modulation MIMO

OFDM Adaptive Modulation

OFDM, SC-FDMA adaptive Modulation MIMO

Security AES AES, X.509 AES SNOW 3G

Technology comparison

24

(1)<100m, (2)~500m, (3)>1km

4G Characteristics: Summary

•  high mobility Ú Handover, Roaming, velocity up to more than 300 km/h

•  switching technique Ú pure packet switching •  integrated multi-media-services Ú VoIP, TVoIP, VoD,

Streaming •  high data rate (up to 1Gbit/s) Ú even at high mobility

should be like DSL •  Size of cell Ú variable and scalable •  QoS Ú prioritization of specific multimedia data •  scalability Ú available and reliable with many users •  air interface Ú OFDM (better spectrum efficiency) •  security Ú up to date standards (e.g. AES) •  Extension / integration of UMTS, LTE and WLAN

approaches

25

Technology comparison 3G to 4G

26

LTE (3G) LTE Advanced (4G)

Peak data rate Down Link (DL) 300 Mbit/s 1 Gbit/s

Peak data rate Up Link (UL) 75 Mbit/s 500 Mbit/s

Transmission bandwidth DL 20 Mhz (max.) 100 Mhz

Transmission bandwidth UL

20 Mhz (max.)

40 Mhz (requirements as defined by ITU)

Coverage Full performance up to 5km

Same as LTE requirement. Should be optimized or deployed in local areas/micro cell environments.

Scalable bandwidths 1.4, 3, 5, 10 and 20 MHz 20-100 MHz

Scalability variable data rate Multiple users per BS

variable data rate Multiple users per BS

Capacity 200 active participants per cell at 5 MHz

3 times higher than that in LTE

Summary: Data rates and mobility

27

High-speed

/Wide-area

Medium-speed

/Urban area

Walking

/Local area

Standing

/Indoors

3G/

IMT 2G

Source: www.3g.co.uk

Mobility

0.1 1 10 100 200 1000 Bitrate, MBit/s

LTE 4G/

LTE advanced

Wireless LANs

Personal area access

Some further readings

•  Eds.: Sesia, S., Toufik, I., Baker, M.: LTE – The UMTS Long Term Evolution – From Theory to Practice, Whiley, 2009

•  LTE: www.gsmworld.com www.ltemobile.de www.apwpt.org

•  WiMAX technology: www.wimaxforum.org

•  IEEE web sites for 802.16 and 802.20: grouper.ieee.org/groups/802/16/ and …/802/20

28