Transcript Evolved Packet System: The Next Generation Mobile Network

Evolved Packet System: The Next
Generation Mobile Network for 4G
systems
Presented by: Dr. Khaled Ali
Outline
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Introduction
Evolved Packet System Architecture
LTE Radio Network
Evolved Packet Core (EPC) Network
QoS Control in the EPS
Conclusion
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EPS Systems
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Introduction
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Different access and core networks
Different QoS control mechanisms
Different mobility management mechanism
High deployment and maintenance cost
High cost per bit
Legacy CS
services
IP
network
CN
GERAN
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UTRAN
CN
CDMA200
HRPD
WiMAX
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EPS Systems
WLAN
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Introduction
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Unified core network architecture for
heterogeneous access networks
New radio access network
Maintaining a competitive wireless
system from 2010-2020
3GPP system architecture evolution
(SAE) Objectives:
– Evolved- (UMTS) Terrestrial Radio
Access Network; Long Term Evolution
(LTE)
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OFDMA downlink radio technology
SC-FDMA uplink radio technology
Increased data rates
Lower latency
Reduced connection setup time
Low cost per bit
Evolved Packet
System (EPS)
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EPC
UTRAN
IP
network
E-UTRAN
CDMA200
HRPD
– Evolved Packet Core (EPC) network
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Legacy CS
services
GERAN
All IP
Supporting 3GPP and non-3GPP radio
access technologies
Seamless service continuity for multi-mode
terminals
EPS Systems
WiMAX
WLAN
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EPS Network Architecture
• E-UTRAN (LTE)
– enhanced Node B (eNB)
– User Equipment (UE)
• EPC
– Serving Gateway (S-GW)
– Packet Data Network Gateway (P-GW)
– Mobility Management Entity (MME)
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EPS Systems
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LTE Radio Network: Features
• Simplified flat radio network architecture
• Flexible and expandable spectrum bandwidth
• High data throughput (Macro eNB& Home eNB)
• Support for multi-antenna scheme (up to 4x4 MIMO )
• Time-frequency scheduling on shared-channel
• Cost-reduction per bit
• Reduced latency
• Seamless inter radio access technology (inter-RAT)
mobility
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EPS Systems
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LTE Radio Protocol Structure
Segmentation,ARQ
ARQ
Segmentation,
ARQ
Segmentation,
Segmentation,
ARQ
RLC and MAC sublayers:
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Payload Selection
Data packet segmentation
Scheduling mobile users and data
flows
Retransmission and multiplexing of
data flows
PHY sublayer:
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QPSK, 16-QAM, 64-QAM
OFDMA modulation
Antenna assignment
Resource allocation
Priority handling,
MAC
Payload Selection
Multiplexing
Retransmission
Control
Scheduler
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RLC
Code rate
Modulation Scheme
HARQ
PHY
Coding, rate matching
Modulation
Uplink Only
DFT
Antenna and
resource allocation
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EPS Systems
Antenna mapping
OFDM modulation
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LTE Bandwidth Flexibility
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Operates in different frequency bands
Can be deployed with different
bandwidths in order to operate in
spectrum of different sizes
Efficient migration of other radio
technologies to LTE
Enabling asymmetric spectrum
utilization
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EPS Systems
1.4 MHz
20 MHz
fDL
fDL/UL
fUL
Paired spectrum
Unpaired spectrum
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LTE: OFDM
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Large degree of freedom
Channel coding is mandatory for
combating fading
Multi-path propagation controlled
by cyclic prefix
OFDM receivers design has less
complexity than Rake receivers
Flexible spectrum expansion
High peak-to-average ratio
Doppler effect
f1
f2 ………………………………………
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1 resource block = 180 kHz = 12 or 14 sub carriers
Frequency
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EPS Systems
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LTE Frame Structure
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FDD and TDD schemes
Single radio interface
Virtually, identical PHY layer
processing
Low cost implementation
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FDD:
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Two carrier frequencies, fUL
and fDL
10 subframes for each UL
and DL
Simultaneous transmission
TDD:
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One radio frame, Tframe = 10ms
One subframe, Tsubframe = 1ms
FDD
UL
fUL
DL
fDL
Subframe #0
#1
#2
(Special subframe)
#3
#4
#5
#6
#7
#8
#9
(Special subframe)
UL
TDD
DL
fUL/fDL
DwPTS GP UpPTS
Single carrier frequency
Seven different uplinkdownlink configurations
DwPTS,
Guard periods
UpPTS
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Sounding signals and random
access
EPS Systems
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LTE Scheduling
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Uplink and downlink transmission are scheduled by the eNB MAC scheduler
UE requests uplink transmission resources from eNB through Scheduling Request
(SR) mechanism
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Dedicated SR (D-SR)
Random Access SR (RA-SR)
Buffer Status Report (BSR) after SR mechanism is required
Distribute available radio resources in the frequency domain
Dynamical change of the allocated resources every 1ms
In addition to the resource block, the scheduler defines the modulation and coding
schemes, MIMO or beamformaing
Providing the desired QoS on a shared channel
QoS class, Queuing delay of the available data, instantaneous channel conditions
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EPS Systems
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LTE Scheduling: Channel Quality Indicator (CQI)
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Varying radio-channel quality in
space, time and frequency
Channel-dependent scheduling
in time and frequency domain
can be exploited
Efficient radio resources
utilization
Fast channel variation tracking
,utilized by the scheduler
Certain mobile users are
scheduled for transmission for
each 1 ms subframe
Uplink sounding reference signal
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EPS Systems
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LTE Retransmission Handling
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Occasional Tx errors
No bit error propagation to upper layers,
drop or reTX
Physical layer attaches 24-bit CRC
checksum to the data unit
HARQ at the MAC layer retransmits the
corrupted transport blocks
Multiple stop-and-wait HARQ process
Single-bit HARQ feedback ACK/NACK
with a fixed timing relation to the
corresponding Tx
Simple, low latency, low overhead,
reliable
Complemented by ARQ at the RLC layer
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EPS Systems
UL ARQ
TX
Local NAK
RLC STATUS
DL HARQ
Rx
UL HARQ
Tx
UL ARQ
RX
Sliding
Window ARQ
RLC PDU
Stop and wait
HARQ
HARQ ACK/
NACK
UL HARQ
Rx
RLC STATUS as DL
HARQ data
DL HARQ
Tx
Transport block
Uplink L1
Downlink L1
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EPC Network
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All IP core network
Evolution of GPRS
Integration with non3GPP systems
Supports PMIPv6
mobility
Mobility Management
Entity (MME) node
Serving Gateway (S-GW)
Packet Data Gateway (PGW)
Evolved Packet Data
Gateway (ePDG)
Policy and Charging Rule
Function (PCRF) from
(IMS)
MSC
GERAN
Legacy CS
services
3GPP
SGSN
UTRAN
MME
EPS-3GPP
GGSN
S-GW
P-GW
PCRF
E-UTRAN
IP
network
HSS/AAA
ePDG
Non-3GPP
WLAN
CDMA200
HRPD
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MSC
Control Interfaces
EPS Systems
WiMAX
Data Interfaces
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QoS Control in EPS networks
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Operators are moving from Single to multiservice offering
Number of broadband subscribers and
their traffic volume are rapidly increasing
EPS QoS concept standardized in 3GPP Rel.
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Enable
service
and
subscriber
differentiation
Bearer; the central element of EPS QoS
concept
The Bearers and their assigned QoS
parameters are managed through a set of
network initiated signaling procedures
EPS QoS concept is a class-based
Network initiated QoS concept + class
based approach gives operators full control
over the QoS provided for the offered
services
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Subscriber differentiation
Service differentiation
Business Vs. Standard
Post- VS. Pre-paid
Flat rate abusers
etc.
Public Internet
VPN
P2P file sharing
Video streaming
IMS voice
CS
Mobile-TV
etc.
EPS Systems
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QoS Control in EPS networks: EPS Bearer
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Identifies packet flows that receives a
common treatment
Packet flows are defined by a fivetuple based packet filters
One bearer exist per a combination of
QoS class and IP address of a terminal
A terminal can have multiple IP
address; one for each Access Point
Name (APN)
Tunnel Header
DSCP
GBR vs. non-GBR Bearers
Default vs. Dedicate Bearers
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EPS Systems
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QoS Control in EPS networks: QoS Parameters
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QoS Class Identifier (QCI)
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Allocation and Retention Priority (ARP)
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specifies the user-plane treatment for a packet on a specified bearer
Specifies the control plane treatment a bearer receives
Maximum Bit Rate (MBR)
Guaranteed Bit Rate (GBR)
Aggregate Maximum Bit Rate (AMBR)
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defined by group of non-GBR bearers for differentiated subscription
QoS Control in EPS networks: QoS Mechanism
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Control-Plane Signaling
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PCRF issues Policy and Charging Control (PCC) rules to the gateway
User-Plane Functions (3GPP and O&M configuration through signaling Procedures)
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Classified into
– Packet-Flow Level Functions
– Bearer-Level Functions
– DSCP-Level Functions
EPS Systems
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QoS Control in EPS networks: Dedicated Bearer Set up
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Network-Initiated QoS Control
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Network initiates the signal for establishing
a dedicated bearer with a specific QoS
Triggered by AP or DPI
Client is access QoS unaware
Needs a policy controller
Client
(access QoS
unaware)
Terminal
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Terminal initiates the signaling for
establishing the dedicated bearer
The networks initiates the signaling to the
RAN
The client must be aware of the QoS model
of the access networks
No need for a policy controller
AF/ DPI
Initiate dedicated bearer (UL packet filters)
Network
RAN
Terminal-Initiated QoS Control
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Service layer signaling (SIP)
Initiate dedicated bearer (QoS info)
Network-Initiated
Client
(access QoS
aware)
Service layer signaling (SIP)
AF/ DPI
Initiate dedicated bearer (QoS info + DL packet filters)
Terminal
Network
RAN
Initiate dedicated bearer (QoS info)
Terminal-Initiated
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Conclusion
• Unified Core Network
• New Radio Access Network for 4G systems
• Enhanced scheduling and retransmission
mechanism
• Bearer-based QoS control paradigm
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EPS Systems
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