LTE Architecture.pdf

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1. LTE
Garima Saini
Assistant Professor
Department of Electronics and Communication Engineering
National Institute of Technical Teachers Training Research

2. Cellular Networks Impact our Lives
2
More Mobile Connection
More Mobile
Information Sharing
More Mobile Users
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More Infrastructure
Deployment

3. •Widespread use of ‘internet’
•For better quality of services and speed
•Shiftfromlandlinebroadbandtosmartphoneand
tablets for faster and ease of access to internet

5. National Institute of Technical Teacher's
Training & Research, Chandigarh

6. http://www.radio-electronics.com/
Mobiledatathatisexpected
toincreaseto11.2Exabytes
(EB) per month by 2017.

8. ❖The basic term used to describe 4G is MAGIC.
4G
MAGIC:
• Mobile Multimedia
• Anytime Anywhere
• Global Mobility Support
• Integrated Wireless Solution
• Customized Personal Services

9. Cellular Core Network
eNodeB 3
S-GW 2
P-GW
LTE Infrastructure
9
S-GW 1
eNodeB
1
eNodeB 2
Internet and
Other IP Networks
GTP Tunnels
UE 2
UE 1
MME/PCRF/HSS
•UE: user equipment
•eNodeB: base station
•S-GW: serving
gateway
•P-GW: packet data
network gateway
•MME: mobility
management entity
•HSS: home subscriber
server
•PCRF: policy charging
and rule function

10. LTE Architecture (Cont’d)
10
•eNodeB, S-GW and P-
GW are involved in
session setup, handoff,
routing
User
Equipme
nt (UE)
Gateway
(S-GW)
Mobility
Management
Entity
(MME)
Network
Gateway
(P-GW)
Home
Subscriber
Server
(HSS)
Policy Control and
Charging Rules
Function (PCRF)
Station
(eNodeB)
Base Serving Packet Data
Control Plane
Data Plane

11. Access Procedure
•Cell Search
–Base station broadcasts
synchronization signals and
cell system information
(similar to WiFi)
–UE obtains physical layer
information
•UE acquires frequency and
synchronizes to a cell
•Determine the start of the
downlink frame
•Determine the cell identity
•Random access to establish
a radio link
11
Base
station
UE 2
UE 1

12. Clien
t
Base
station
Core
network
Step 1: random access request (pick one of 64 preambles)
Step 2: random access response
Step 3: transmission of mobile ID
Step 4: contention resolution msg
Only if UE is not known in Base station
Random Access
12
Adjust uplink
timing
If ID in msg matches UE ID, succeed.
If collision, ID will not match!

13. Base
station
Random Access (Cont’d)
13
UE 2
UE 1
Why not carrier sensing like
WiFi?
•Base station coverage is much
larger than WiFi AP
–UEs most likely cannot hear
each other
•How come base station can
hear UEs’ transmissions?
–Base station receivers are
much more sensitive and
expensive

14. Connection Setup
•Session Requests
–UE to base station
–Base station to MME
•MME obtains
subscriber info from
HSS, selects S-GW and
P-GW
–S-GW sends to P-GW
•P-GW obtains policy
from PCRF
14
S-GW
UE P-GW
Session
Request
MME

15. Connection Setup (Cont’d)
•Session Response
–Establishes GPRS
Tunnels (GTP) between
S-GW and P-GW,
between S-GW and UE
–Base station allocates
radio resources to UE
15
Session
Response
S-GW
UE P-GW
MME

16. Mobility Management
Handoff
•Handoff without
change of S-GW
–No change at P-GW
•Handoff with change
of S-GW or MME
•Inter-technology
handoff (LTE to 3G)
16
S-GWUE P-GW
MME

17. Mobility Management (Cont’d)
Paging
•If S-GW receives a
packet to a UE in IDLE
state, inform MME
•MME pages UE
through base station
17
S-GW
UE P-GW
MME
RRC_IDLE Packet received
Paging
Request

18. Outline
•Basic Architecture of LTE
•Access Procedure
–Why no carrier sensing
•Connection Setup
–Unlike WiFi, need to keep the same IP address at
different attachment points
•Mobility Management
•Power Management and Mobile Apps
•Differences between 3G and LTE
•Conclusion
18

19. Power Management: LTE
•UE runs radio resource
control (RRC) state
machine
•Two states: IDLE,
CONNECTED
•Discontinuous
reception (DRX):
monitor one subframe
per DRX cylce; receiver
sleeps in other
subframes
19Courtesy:Morley Mao

20. Power Management: UMTS
•State promotions have promotion delay
•State demotions incur tail times
20
Tail Time
Tail Time
Delay: 1.5sDelay: 2s
Channel Radio
Power
IDLE Not
allocated
Almost
zero
CELL_FACH Shared,
Low Speed
Low
CELL_DCHDedicated,
High Speed
High
Courtesy: Feng Qian

21. Example in Detail: RRC State Machine
for a Large Commercial 3G Network
21
Promo Delay: 2 Sec
DCH Tail: 5 sec
FACH Tail: 12 sec
DCH: High Power State (high throughput and power consumption)
FACH: Low Power State (low throughput and power consumption)
IDLE: No radio resource allocated
Tail Time
Waiting inactivity timers to expire
Courtesy: Feng Qian

22. Example in Detail: Pandora Music
22
Problem: High resource overhead of periodic audience measurements (every 1 min)
Recommendation: Delay transfers and batch them with delay-sensitive transfers
Courtesy: Feng Qian

23. Why Power Consumptions of RRC States so
different?
•IDLE: procedures based on reception rather
than transmission
–Reception of System Information messages
–Cell selection registration (requires RRC
connection establishment)
–Reception of paging messages with a DRX cycle
(may trigger RRC connection establishment)
–Location and routing area updates (requires RRC
connection establishment)
23

24. UMTS RRC State Machine (Cont’d)
•CELL_FACH: need to continuously receive
(search for UE identity in messages on FACH),
data can be sent by RNC any time
–Can transfer small data
–UE and network resource required low
–Cell re-selections when a UE moves
–Inter-system and inter-frequency handoff possible
–Can receive paging messages without a DRX cycle
24

25. UMTS RRC State Machine (Cont’d)
•CELL_DCH: need to continuously receive, and
sent whenever there is data
–Possible to transfer large quantities of uplink and
downlink data
–UE and network resource requirement is relatively
high
–Soft handover possible for dedicated channels and
Inter-system and inter-frequency handover possible
–Paging messages without a DRX cycle are used for
paging purposes
25

26. GGSN
SGSN
RNC
Node B eNodeB
RNC functions moved to eNodeB.
• No central radio controller node
• OFDM radio, no soft handover
• Operator demand to simplify
Mobility Management EntityMME
(not user plane
functions)
Control plane/user plane split for better
scalability
• MME control plane only
• Typically centralized and pooled
PGW
SGW
PDN GateWay
Serving GateWay
PGW/SGW
• Deployed according to traffic demand
• Only 2 user plane nodes (non-roaming
case)
•Functional changes compared to the current UMTS
Architecture
LTE vs UMTS (3G): Architecture
26

27. Need of 4G communication
✔Althoughsubscribersaregettinghighspeedinternetconnectionsat
home,officeorevenatmalls,butonceweareonroadsorinmobility
those high speeds are difficult to achieve.
✔4G promises to give real mobile broadband to end user.
✔Duetosignificantincreaseinoverallmobileusers,limitedspectrumand
demandofnewservices,therequirementofnewtechnologyisthereto
cater quality services to the users.

28. .
❖ 4G technology support interactive multimedia, voice,
streaming video & other broadband.
❖IP based mobile system.
❖High speed.
❖High capacity.
❖Global mobility and scalable mobile services.
❖Devices : more user friendly interface.
Features of 4G communications

29. .
Technology 3G 4G
Frequency Band1.8 - 2.5 GHz 2 - 8 GHz
Bandwidth 5-20 MHz
Approx.
100 MHz
Data rate Up to 2Mbps
Up to 100 Mbps
or 1Gbps
Switching
Circuit/Packet
switching
Packet switching
Internet servicesBroadbandUltra Broadband
Comparison of 3G with 4G communication

30. Comparison of 3G with 4G
communication

31. Disadvantages of 4G communication
❖Battery draining issues: As the speed of 4G is higher than
3G network, it drains the battery at faster speed too.
❖Limited Phone network: This is a new technology in India.
The deployment of new towers will take time and user will
experience the missing 4G network.
❖ 4G devices needed to avail 4G services.

32. Applications of 4G
Communication
❖ Better usage of multimedia applications .
❖ Virtual Presence: 4G system gives mobile users virtual
presence i.e. always on connection that keep user involved in
activities.
❖ Traffic control
❖ Sensors on public vehicles

33. ❖ Virtualnavigation:4Gwillprovideuserswithvirtual
navigationduetothatausercanaccessadatabaseofstreets,
buildings,etc.,ofalargecity.Thisrequireshighspeed
transmission.
❖ Tele-medicine:Itwillalsosupporttheremotehealth
monitoringofpatientsviavideoconferenceassistancefora
doctor anytime and anywhere.
Applications of 4G
Communication

34. Wi-Fi
•TheevolutionofwirelessLANstartedwiththe
introduction of the 802.11b standard in 1999.
•Describesonlynarrowrangeofconnectivity
ensuring Wireless Local Area Network
• IEEE 802.11 Standard
• Establishand enforcestandardsfor
Interoperability and backward compatibility

35. Wi-Fi Standards

36. Wi-Max
•Worldwide interoperability for microwave access
•An IP based wireless broadband access technology
•PerformancesimilartoWi-Fi(pluginlikeEthernet)
withcoverageandQoSofcellularnetworks(provide
roaming voice and data).
•Roger Marks founded 802.16 (Wi-Max) in 1998.
•Providefixedandmobileinternetaccesswithout
the need for direct LOS

37. WiMAX: Principles
•The design of WiMAX network is based on the
following major principles:
•Spectrum: able to be deployed in both licensed and
unlicensed spectra.
•Topology: supports different Radio Access Network
(RAN) topologies.
• Interworking: independent RAN architecture to
enable seamless integration and interworking with
WiFi, 3GPP and 3GPP2 networks and existing IP
operator core network.
• Mobility management: possibility to extend the
fixed access to mobility and broadband multimedia
services delivery.

38. Wi-Max Architecture

40. LTE
•Evolve from 3
rd
generation technology
•Supports higher data rate through wider bandwidth
•Provides low latency (radio delay<5ms)
•Implementsschedulingatbasestationtomaintain
channel quality
•All IP based network with reduction in cost per bit
•Flexibilityinuseofnewandexistingfrequency
bands (spectrum flexibility)

41. •Low power consumption
•Supports mobility speeds up to 35km/hr with 500km/
hr under consideration
•Provide open interface to support multi vendor
deployments
•Provide robustness-no single point of failure
•Support multi-RAT(radio access technology) with
resource controlled from the network
•Support of seamless mobility to latency system as
well as to other emerging systems including inter-
RAT handover and service based RAT services
•Maintain appropriate level of security
•LTE makes use of new e-NodeB’s and get rid of the
use of RNC
•Simple network architecture with open interfaces

42. LTE Architecture

43. LTE Specification
•Higher peak data rate
•Downlink: 100Mbps
(150Mbps peak based on 2x2 MIMO)
(300Mbps peak based on 4x4 MIMO)
Uplink: 50Mbps(75Mbps peak) (5Mbps individually)
•ImprovedlatencyUE-RNC-UEbelow10ms(round
trip time)
•Supportofscalablebandwidth-1.4,3,5,10,15,
20MHz
•Supportofpairedandunpairedspectrum(FDD&
TDD)
•Uplink:QPSK,16-QAM&64-QAM(optionalfor
handset)
•Downlink:QPSK16QAM&64QAM

44. Similarities (Wi-Max & LTE)
•OFDMA (orthogonalfrequencydivisionmultiple
access) on downlink
•MIMO(multipleinputmultipleoutput)andbeam
forming
•Backward compatibility
•Speed
•Error correcting codes- viterbi and turbo coding
•IP based technology
•Scalable bandwidth

45. Comparision
Points of
difference
Wi-Max LTE Wi-Fi
Subcarrier
Spacing
It can be variable
due to which
capacity can be
vary
Constant at
15kHz
For 64
subcarrier it is
314.5kHz
LatencyTime b/w user-BS-
user is 50ms
Time b/w UE-
RNC-UE is
10ms
Approx 100ms
Channel
utilization
Optimizes for
maximum
channel usage by
processing all the
information in
wide channel
Organize the
available
spectrum into
smaller chunks
Upto 70 to
80% utilization

46. Points of
difference
Wi-Max LTE Wi-Fi
Evolution Completely new
technology with
upgrading in
generations but
not an exact
evolution
Evolve from
WCDMA to
HSPA to LTE
with a core
backbone of GSM
Not an exact
evolution
(3G based)
Duplexing
Mode
Use only TDD
but in 802.16m
release 1.5 add
FDD
Use FDD and
TDD
use TDD
Uplink
Signaling
OFDMA SC-FDMA OFDMA

47. Points of
difference
Wi-Max LTE Wi-Fi
Speed Upto 100MbpsUpto 50MbpsUpto 11Mbps
SIM Not requiredSIM required Not required
Backward
Frequency
Not
compatible
like mobile
technology
Compatible
with GSM,
GPRS, UMTS,
EDGE,
WCDMA,
HSPA, CDMA-
ONE,
CDMA-2000,
Not
compatible
like mobile
technology

49. Future Development
LTE-A Wi-Max 2.0
Carrier aggregation Higher spectrum efficiency and
higher order MIMO
Relaying to improve coverage
and reduce development cost
Higher peak and user data rates
Extended multi-antenna
transmission
Seamless WiFi-WiMax
handover
Coordinated multipoint (CoMP)
transmission and reception
Support for femto cells

50. THANK
YOU