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
• Shift from landline broadband to smart phone and
tablets for faster and ease of access to internet
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-GW
UE 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
19
Courtesy:Morley Mao
20. Power Management: UMTS
• State promotions have promotion delay
• State demotions incur tail times
20
Tail Time
Tail Time
Delay: 1.5s
Delay: 2s
Channel Radio
Power
IDLE Not
allocated
Almost
zero
CELL_FACH Shared,
Low Speed
Low
CELL_DCH Dedicated,
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 Entity
MME
(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
✔ Although subscribers are getting high speed internet connections at
home, office or even at malls, but once we are on roads or in mobility
those high speeds are difficult to achieve.
✔ 4G promises to give real mobile broadband to end user.
✔ Due to significant increase in overall mobile users, limited spectrum and
demand of new services, the requirement of new technology is there to
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 Band 1.8 - 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 services Broadband Ultra Broadband
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. ❖ Virtual navigation: 4G will provide users with virtual
navigation due to that a user can access a database of streets,
buildings, etc., of a large city. This requires high speed
transmission.
❖ Tele-medicine: It will also support the remote health
monitoring of patients via video conference assistance for a
doctor anytime and anywhere.
Applications of 4G
Communication
34. Wi-Fi
• The evolution of wireless LAN started with the
introduction of the 802.11b standard in 1999.
• Describes only narrow range of connectivity
ensuring Wireless Local Area Network
• IEEE 802.11 Standard
• Establish and enforce standards for
Interoperability and backward compatibility
36. Wi-Max
• Worldwide interoperability for microwave access
• An IP based wireless broadband access technology
• Performance similar to Wi-Fi (plug in like Ethernet)
with coverage and QoS of cellular networks(provide
roaming voice and data).
• Roger Marks founded 802.16 (Wi-Max) in 1998.
• Provide fixed and mobile internet access without
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.
40. LTE
• Evolve from 3rd
generation technology
• Supports higher data rate through wider bandwidth
• Provides low latency (radio delay<5ms)
• Implements scheduling at base station to maintain
channel quality
• All IP based network with reduction in cost per bit
• Flexibility in use of new and existing frequency
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
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)
• Improved latency UE-RNC-UE below 10ms (round
trip time)
• Support of scalable bandwidth- 1.4, 3, 5, 10, 15,
20MHz
• Support of paired and unpaired spectrum (FDD &
TDD)
• Uplink: QPSK, 16-QAM & 64-QAM (optional for
handset)
44. Similarities (Wi-Max & LTE)
• OFDMA (orthogonal frequency division multiple
access) on downlink
• MIMO (multiple input multiple output) and beam
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
Latency Time 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 100Mbps Upto 50Mbps Upto 11Mbps
SIM Not required SIM 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
48.
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
