Điện tử viễn thông chap 1 STC LTE eNB overview khotailieu
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Distribution
ED01
English
Jae ho, Lee
Customer Training Center
Contents
Intro
Network Architecture
Multiple Access
Frame Structure
Multiple Antenna Technique
LTE Evolution
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Intro
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LTE Definition and History
R99
Rel4
WCDMA
Rel5
HSDPA
Rel6
HSPA
Rel7
Rel8
Rel1
0
HSPA evolution
LTE
LTE-advanced
LTE Background
Demand for high-datarates
Reduced Latency
Enhancement of
UTRA & UTRAN
Improved system
capacity & coverage
Reduced cost
for the operator
UTRA : Universal Terrestrial Radio Access
UTRAN: UTRA Radio Access Network
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Requirements of LTE (1/2)
[Ref: TR 25.913]
Peak data rate
100 Mbps (DL) / 50 Mbps (UL)
Baseline: 20 MHz BW, 1TX & 2RX UE
Less than 50msec
Dormant
(Cell_PCH)
Active
(Cell_DCH)
Significantly reduced latency
Control-plane latency
– Idle ↔ active : < 100 ms
– dormant ↔ Active: < 50 ms
Less than 100msec
Camped-state
(idle)
User-plane latency : < 5 ms in unload condition for small IP packet
Significantly improved throughput & spectrum efficiency
2 ~ 4 times Release 6 HSPA
Spectrum flexibility
Scalable bandwidth: 1.4/3/5/10/15/20 MHz
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Requirements of LTE (2/2)
[Ref: TR 25.913]
Mobility
Optimized for low mobile speed 0 ~ 15 km/h
15 ~ 120 km/h should be supported with high performance
Connection maintained at speeds 120 ~ 350 km/h (or even up to
500 km/h)
Support for inter-working with existing 3G systems and non3GPP systems
Reduced CAPEX and OPEX including backhaul
Efficient support of the various types of services, especially
from the PS-domain
Web-browsing, FTP, video-streaming, VoIP
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LTE Standard Specifications
Free Download from />Specification index
TS 36.100 series
Description of contents
Equipment Requirements:
Terminals, Base stations, and Repeaters
Layer 1 (Physical layer):
TS 36.200 series
Physical channels, Modulation, Multiplexing, Channel
coding, etc.
Layers 2 and 3:
TS 36.300 series
Medium Access Control, Radio Link Control, and Radio
Resource Control.
TS 36.400 series
TS 36.500 series
Network Signaling & Interfaces:
Architecture, S1, X2 Interfaces, etc.
UE equipment conformance testing
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TD-LTE Fundamental
LTE FDD
A paired frequency band allocation
Uplink and downlink selected from different frequency bands
LTE TDD
Enables use of unpaired frequency bands
The same frequency band for UL and DL, divided in time
Channel Reciprocity
TD-LTE and LTE FDD Difference
solely a physical layer manifestation and therefore invisible to
higher layers
there are no operational differences between the two modes in the
system architecture.
FDD
TDD
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E-UTRA Operating Band
FDD - frequency division duplex
TDD - time division duplex
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HARQ and control signaling
HARQ ACK/NACK
For FDD, the acknowledgement of data received in sub-frame n is
transmitted in sub-frame n+4
For TDD, the acknowledgement obviously cannot be transmitted until
an uplink sub-frame occurs
Multiple UL ACK/NACK Transmission
For, DL heavy case, the reception of several downlink sub-frames may
need to be acknowledged in a single uplink sub-frame.
ACK/NACK Bundling
- Combines the acknowledgements in time domain from multiple
hybrid-ARQ processes
ACK/NACK Multiplexing
- Combines the acknowledgements in codeword domain from multiple
hybrid-ARQ processes.
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Network Architecture
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WiMAX + LTE Network Architecture
P-GW (HA)
WSM
LSM-C
ACR
Base Station
Smartphone
S-GW
Base Station
Mobile Phone
MME
Base Station
Embedded Laptop
Base Station
Dongle type
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LTE Network Architecture II
Radio Network Controller
3G UMTS •• RNC:
SGSN: Serving GPRS Support Node
•
•
•
•
•
LTE
• GGSN: Gateway GPRS Support Node
eNB: evolved NodeB
MME: Mobility Management Entity
S-GW: Serving Gateway
P-GW: PDN (Packet Data Network) Gateway
EPC: Evolved Packet Core
EPC
GGSN
MME
S-GW/P-GW
MME
S-GW/P-GW
S1
S1
SGSN
S1
S1
RNC
X2
RNC
eNB
NodeB
NodeB
NodeB
X2
X2
NodeB
E-UTRAN
eNB
eNB
* Source: 3GPP TS 36.300
Entity
Function
eNB
All radio interface functions, Resource allocation
MME
Manages mobility, UE identity, Security parameters
S-GW
Terminates the interface towards E-UTRAN
P-GW
Terminates the interface towards PDN, UE IP address allocation
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Interface & Protocol Stack
User plane Protocol Stack
Application
IP
IP
Relay
Relay
PDCP
GTP-U
GTP-U
GTP-U
PDCP
GTP-U
RLC
RLC
UDP/IP
UDP/IP
UDP/IP
UDP/IP
MAC
MAC
L2
L2
L2
L2
L1
L1
L1
L1
L1
L1
LTE-Uu
S1-U
UE
eNodeB
S5/S8
a
Serving GW
SGi
PDN GW
Control plane Protocol Stack
NAS
NAS
Relay
RRC
S1-AP
PDCP
RRC
PDCP
S1-AP
SCTP
RLC
RLC
IP
IP
MAC
MAC
L2
L2
L1
L1
L1
L1
UE
LTE-Uu
eNodeB
SCTP
S1-MME
MME
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E-UTRAN & EPC functions
eNB
• RRM: Radio Resource Management
• RB: Radio Bearer
• RRC: Radio Resource Control
• PDCP: Packet Data Convergence Protocol
• NAS: Non-Access Stratum
• EPS: Evolved Packet System
Inter Cell RRM
RB Control
Connection Mobility Cont.
MME
Radio Admission Control
NAS Security
eNB Measurement
Configuration & Provision
Dynamic Resource
Allocation (Scheduler)
S1MME
Idle State Mobility
Handling
EPS Bearer Control
RRC
PDCP
S-GW
P-GW
RLC
MAC
S1-U
S1
PHY
Mobility
Anchoring
UE IP address
allocation
Packet Filtering
internet
E-UTRAN
EPC
Yellow boxes → logical nodes
White boxes → functional entities of the control plane
Blue boxes → radio protocol layers
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Multiple Access
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LTE Key Parameters
Frequency
Range
UMTS FDD bands and UMTS TDD bands
Channel
Bandwidth,
1Resource Block
(RB) = 180KHz
1.4MHz
3MHz
5MHz
10MHz
15MHz
20MHz
6 RBs
15RBs
25RBs
50RBs
75RBs
100RBs
Modulation
scheme
Downlink: QPSK, 16QAM, 64QAM
Uplink: QPSK, 16QAM, 64QAM (optional for handset)
Multiple Access
Downlink: OFDMA
Uplink: SC-FDMA
MIMO
- Transmit diversity, Cyclic delay diversity (Max. 4 antenna at Base
station and handset)
- Spatial multiplexing, Multiuser MIMO
Peak Data rate
Downlink: 150Mbps (UE category 4, 2x2 MIMO, 20MHz)
300Mbps (UE category 5, 4x4 MIMO, 20MHz)
Uplink: 75Mbps (20MHz)
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Brief Introduction of OFDMA
* Source: 3GPP TS25.892
Each sub-carrier carries a separate low-rate stream of data
Sub-carriers
→ Orthogonal frequencies & independently modulated
Symbol duration >> channel delay spread
→ Much less ISI (Inter-Symbol Interference)
A guard time is added to each symbol
→ Cyclic Prefix in LTE
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Advantages & Disadvantages of OFDMA
Advantages
Scalable data rate
Simpler channel equalizer than CDMA
Robust against multipath fading by using CP
Dynamic resource allocation considering channel information
→ Maximize throughput
Disadvantages
High PAPR (Peak-to-Average Power Ratio)
Sensitive to frequency offset and clock offset
Requires guard interval
→ Reduces throughput
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CDMA & OFDM vs. OFDMA
CDMA vs. OFDMA
Attribute
CDMA
Transmission bandwidth
Symbol period
Separation of users
OFDMA
Full system bandwidth
Variable up to full system bandwidth
Very long :
Very short :
Defined by subcarrier spacing and
inverse of the system bandwidth
independent of system bandwidth
Orthogonal spreading codes
Frequency and time
OFDM vs. OFDMA
Freq.
Freq.
Time
Time
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DL/UL Multiplexing
DL Orthogonal Frequency Division Multiple Access (OFDMA)
No Inter Symbol and multipath interference
Frequency selective scheduling
Far improved MIMO performance
UL Single-Carrier FDMA (SC-FDMA)
No interference between intra cell users
Low PAPR (Peak to Average Ratio)
IDFT: Invers Discrete Fourier Transform
DFT: Discrete Fourier Transform
S0 S1 S2 ……S10 S11
Freq.
Freq.
IDFT
IDFT
DFT
S0 S1 S2 ……S10 S11
Downlink OFDMA
S0 S1 S2 ……S10 S11
Uplink SC-FDMA
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Brief Introduction of SC-FDMA
OFDMA vs. SC-FDMA
In OFDMA, each sub-carrier only carries information related to one
specific symbol
In SC-FDMA, each sub-carrier contains information of ALL
transmitted symbols
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Frame Structure
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LTE Frame Structure
Frame Structure Type 1: for FDD
Each radio frame is 10ms long and consists of 20 slots of length
0.5ms, numbered from 0 to 19
One radio frame, Tf = 307200Ts=10 ms
One slot, Tslot = 15360Ts = 0.5 ms
#0
#1
#2
#3
#18
#19
One subframe
Frame Structure Type 2: for TDD
Special fields DwPTS, GP, and UpPTS in subframe #1 (always)
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Frame Structure (TDD)
Special Sub-frame
DwPTS: used for downlink data transmission. (varied from three up
to twelve OFDM symbols)
GP: guard period for the downlink-to-uplink
• Guard period must cover the maximum roundtrip propagation delay within
the cell
• selected by taking eNB-to-eNB interference into account
• two to ten OFDM symbols, sufficient for cell sizes up to and beyond 100 km.
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