lte system interfaces 20110525 a 1.0
DESCRIPTION
LTE System InterfacesTRANSCRIPT
www.huawei.com
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
英文标题 :40-47pt
副标题 :26-30pt
字体颜色 : 反白内部使用字体 :
FrutigerNext LT
Medium
外部使用字体 : Arial
中文标题 :35-47pt
字体 : 黑体 副标题 :24-28pt
字体颜色 : 反白字体 : 细黑体
Security Level: Internal Use
LTE System Interfaces
2010-09
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On completion of this course, you should be able
to:
Know the overall architecture of E-UTRAN, function
split between CN and RAN
Know the radio interface protocol stack and the
function of each layer
Know the physical layer functions and basic
procedures
Know S1/X2 interface protocol stack and the
functions of the interfaces.
Objectives
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References
3GPP TS 《 36.211 》
3GPP TS 《 36.300 》
3GPP TS 《 36.410 》
3GPP TS 《 36.420 》
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1. Overview
2. Radio interface
3. S1 interface
4. X2 interface
Contents
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LTE/SAE Architecture
SGSN
GPRSGPRS
UMTSUMTS
E-UTRANE-UTRAN
cdma2000cdma2000
MME
HSS PCRF
Serving GW PDN GW
BTS BSC/PCU
NodeB RNC
eNodeB
S2b
S1-U
S6a
Gx
S5/8
Gb
Iu
S1-MMES12
S3
S4S11
SGi
S9S10
User planeControl plane
BTS
Internet
CorporateInternet
Operator ServiceNetwork
EPS (Evolved Packet System)
S6d
PDSNBSC
A10/A11
MME: Mobility management entity
PCRF: Policy and Charging Rules Function
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Functional Split between E-UTRAN and EPC
internet
eNB
RB Control
Connection Mobility Cont.
eNB MeasurementConfiguration & Provision
Dynamic Resource Allocation (Scheduler)
PDCP
PHY
MME
S-GW
S1MAC
Inter Cell RRM
Radio Admission Control
RLC
E-UTRAN EPC
RRC
Mobility Anchoring
EPS Bearer Control
Idle State Mobility Handling
NAS Security
P-GW
UE IP address allocation
Packet Filtering
eNB
MME / S-GW MME / S-GW
eNB
eNB
S1
S1
S1 S
1
X2
X2X2E-UTRAN
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General protocol model for E-UTRAN interfaces
General principle for S1/X2 is that the layers and planes are
logically independent of each other. Therefore, as and when
required, the standardization body can easily alter protocol
stacks and planes to fit future requirements.
Application Protocol
Transport Network
Layer
Physical Layer
Signalling Bearer(s)
Transport User
Network Plane
Control Plane User Plane
Transport User
Network Plane
Radio Network
Layer
Data Bearer(s)
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Control plane protocol stacks
SCTP
L2
L1
IP
L2
L1
IP
SCTP
S1-MME eNodeB MME
S1-AP S1-AP
NAS
MAC
L1
RLC
PDCP
UE
RRC
MAC
L1
RLC
PDCP
RRC
LTE-Uu
NAS Relay
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User plane protocol stacks
Serving GW PDN GW
S5/S8a
GTP-U GTP-U
UDP/IP UDP/IP
L2
Relay
L2
L1 L1
PDCP
RLC
MAC
L1
IP
Application
UDP/IP
L2
L1
GTP-U
IP
SGi S1-U LTE-Uu
eNodeB
RLC UDP/IP
L2
PDCP GTP-U
Relay
MAC
L1 L1
UE
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1. Overview
2. Radio interface
3. S1 interface
4. X2 interface
Contents
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Radio interface protocol stack
LTE does not have BMC entity
All types of RB need PDCP processing
NAS
relay
S1 Uu Uu S1
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RRC services and functions
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RRC services and functions Broadcast of System Information related to NAS and AS
Mobility functions including:
UE measurement reporting and control of the reporting for mobility;
UE cell selection and reselection and control of cell selection and
reselection;
Context transfer at handover.
Establishment, maintenance and release of an RRC connection
between the UE and E-UTRAN including:
Allocation of temporary identifiers between UE and E-UTRAN;
Configuration of signaling radio bearer(s) for RRC connection:
Security functions including key management;
Establishment, configuration, maintenance and release of point to
point Radio Bearers;
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RRC protocol states & state transitions
LTE supports 2 RRC states: RRC_IDLE and
RRC_CONNECTED
RRC_IDLE:
PLMN selection;
Broadcast of system information;
Paging;
Cell re-selection mobility;
No RRC context stored in the eNB
RRC_CONNECTED
UE has an E-UTRAN-RRC
connection;
E-UTRAN knows the cell which
the UE belongs to;
Network can transmit and/or
receive data to/from UE;
Neighbor cell measurements;
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Relation between RRC state and NAS states
EPS Mobility Management (EMM) state includes: EMM-DEREGISTERED
EMMREGISTERED
EPS Connection Management (ECM) state includes: ECM-IDLE
ECM-CONNECTED
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E-UTRAN identities
E-UTRAN Cell Global Identifier (ECGI): used to identify cells
globally.
The ECGI is constructed from the MCC (Mobile Country Code), MNC
(Mobile Network Code) and the ECI (E-UTRAN Cell Identifier).
ECI: used to identify cells within a PLMN.
ECI has a length of 28 bits and contains the eNB Identifier.
Global eNB Identifier: used to identify eNBs globally.
The Global eNB Identifier is constructed from the MCC (Mobile Country
Code), MNC (Mobile Network Code) and the eNB-Id (eNB Identifier).
eNB Identifier: used to identify eNBs within a PLMN.
The eNB Id is contained within the E-UTRAN Cell Identifier
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Segm.ARQ etc
Multiplexing UE1
Segm.ARQ etc
...
HARQ
Multiplexing UEn
HARQ
BCCH PCCH
Scheduling / Priority Handling
Logical Channels
Transport Channels
MAC
RLCSegm.
ARQ etcSegm.
ARQ etc
PDCPROHC ROHC ROHC ROHC
Radio Bearers
Security Security Security Security
...
Layer 2 in overall Layer 2 is split into the following sublayers:
Medium Access Control (MAC), Radio Link Control
(RLC) and Packet Data Convergence Protocol (PDCP)
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PDCP Sublayer
The main services and functions of the PDCP sublayer
Header compression and decompression for user plane data.
Security functions:
ciphering and deciphering;
integrity protection and verification
eNB
RLC
MAC
PHY
PDCP
RRC
NAS SignalingControl Plane
EncryptionIntegrity Checking
User PlaneIP Header Compression
EncryptionSequencing and Duplicate Detection
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RLC Sublayer
The main services and functions of the RLC sublayer include:
Transfer of upper layer PDUs supporting AM, UM and TM
Error Correction through ARQ (CRC check provided by the physical
layer)
Concatenation of SDUs for the same radio bearer;
Duplicate Detection;
Segmentation;
SDU discard;;
eNB
RLC
MAC
PHY
PDCP
RRC
NAS Signaling
TM (Transparent Mode)UM (Unacknowledged Mode)
AM (Acknowledged Mode)Segmentation and Re-Assembly
ConcatenationError Correction
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MAC Sublayer The main services and functions of the MAC sublayer include:
Mapping between logical channels and transport channels;
Multiplexing/demultiplexing of RLC PDUs belonging to one or
different radio bearers into/from transport blocks (TB) delivered
to/from the physical layer;
Priority handling between logical channels of one UE;
Priority handling between UEs;
Error correction through HARQ;
Padding;
Transport format selection;
eNB
RLC
MAC
PHY
PDCP
RRC
NAS Signaling
Channel Mapping and Multiplexing Error Correction - HARQQoS Based Scheduling
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Physical Layer
eNB
RLC
MAC
PHY
PDCP
RRC
NAS SignalingError Detection
FEC Encoding/Decoding Rate Matching
Mapping of Physical ChannelsPower Weighting
Modulation and DemodulationFrequency and Time Synchronization
Radio MeasurementsMIMO ProcessingTransmit Diversity
BeamformingRF Processing
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LTE channel mapping-downlink
DL-SCH
Physical Layer
MAC Layer
RLC Layer
PDCP Layer
RRC Layer
PhysicalChannels
TransportChannels
LogicalChannels
PDSCH
PDCCH
PHICHPCFIC
HPBCH
BCH PCH
BCCH PCCH CCCH DCCH DTCH
TM TM TM UM/AM UM/AM
Ciphering
Integrity
Ciphering
ROHC
RRC
ESM EMM IPNAS Layer
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LTE channel mapping-uplink
Physical Layer
MAC Layer
RLC Layer
PDCP Layer
RRC Layer
PhysicalChannels
TransportChannels
LogicalChannels
PUSCH
PUCCH
PRACH
RACH
CCCH
TM UM/AM UM/AM
Ciphering
Integrity
Ciphering
ROHC
RRC
ESM EMM IPNAS Layer
UL-SCH
DCCH DTCH
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Transport channels
Downlink:
Broadcast Channel (BCH)
fixed, pre-defined transport format;
Downlink Shared Channel (DL-SCH)
support for HARQ
support for dynamic link adaptation by varying the modulation,
coding and transmit power;
possibility to use beam forming;
support for both dynamic and semi-static resource allocation;
support for UE DRX to enable UE power saving;
support for MBMS transmission
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Transport channels
Downlink:
Paging Channel (PCH)
support for UE DRX to enable UE power saving
mapped to physical resources which can be used
dynamically also for traffic/other control channels
Multicast Channel (MCH)
support for MBSFN combining of MBMS transmission on
multiple cells
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Transport channels
Uplink:
Uplink Shared Channel (UL-SCH)
possibility to use beam forming
support for dynamic link adaptation by varying the transmit
power and potentially modulation and coding;
support for HARQ;
support for both dynamic and semi-static resource
allocation.
Random Access Channel(s) (RACH)
limited control information;
collision risk;
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Physical layer frame structure -FDD
Type 1, applicable to FDD
The downlink OFDM sub-carrier spacing is f = 15 kHz, a reduced
sub-carrier spacing f = 7.5 kHz is only for MBMS-dedicated cell
Slot (0.5ms)
Radio Frame Tf = 307200 x Ts = 10ms
Subframe (1ms)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Ts = 1/(15000x2048) = 32.552083ns
Tslot = 15360 x Ts
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Physical layer frame structure -TDD
Type 2 Radio Frame Tf = 307200 x Ts = 10ms
0
Special Subframe
2 3 4 5 7 8 9
DwPTS (Downlink Pilot Time Slot)
GP (Guard Period)
UpPTS (Uplink Pilot Time Slot)
Page 28
• Type 2, applicable to TDD
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Type 2 Radio Frame Switching Points
Configuration Switching Point Periodicity
Subframe Number
0 1 2 3 4 5 6 7 8 9
0 5ms D S U U U D S U U U
1 5ms D S U U D D S U U D
2 5ms D S U D D D S U D D
3 10ms D S U U U D D D D D
4 10ms D S U U D D D D D D
5 10ms D S U D D D D D D D
6 5ms D S U U U D S U U D
Page 29
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Physical layer frame structure-FDD(1/2)
In the case of 15 kHz sub-carrier spacing there are two cyclic-prefix lengths,
corresponding to seven and six OFDM symbols per slot respectively
Normal cyclic prefix:
TCP = 160Ts (OFDM symbol #0) , TCP = 144Ts (OFDM symbol #1 to #6)
Extended cyclic prefix: TCP-e = 512Ts (OFDM symbol #0 to OFDM symbol #5)
In case of 7.5 kHz sub-carrier spacing, there is only a single cyclic prefix
length TCP-low = 1024Ts, corresponding to 3 OFDM symbols per slot.
Radio Frame = 10ms
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
7 OFDMSymbols (Normal
Cyclic Prefix)
6 OFDM Symbols (Extended Cyclic
Prefix)
0 1 2 3 4 5 6
0 1 2 3 4 5
CP (Cyclic Prefix)
Ts
Ts
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Physical layer frame structure-FDD(2/2)
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LTE physical resource definition Basic definitions Resource element
Resource block
RBscN
ULsymbNConfiguration
Normal cyclic prefix 12 7
Extended cyclic prefix 12 6
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Physical layer processing
Bit level processing:
Transport block from MAC layer
24 bit CRC is the baseline
Channel coding: Turbo coding Channel coding
Rate matching
Code block concatenation
110 ,...,, Aaaa
110 ,...,, Bbbb
110 ,...,, rKrrr ccc
)(
1)(
1)(
0 ,...,, iDr
ir
ir r
ddd
110 ,...,, rErrr eee
110 ,...,, Gfff
Transport block CRC attachment
Code block segmentationCode block CRC attachment
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Physical layer processing
Symbol level processing:
The scrambling stage is applied to all downlink physical channels,
and serves the purpose of interference rejection
Modulation: QPSK, 16QAM, and 64QAM (64 QAM optional in UE)
Scrambling Modulation
Mapper
Layer Mapper
Precoding
Resource Element Mapper
OFDM Signal
Generation
Resource Element Mapper
OFDM Signal
Generation
Scrambling Modulation
Mapper
Codewords LayersAntenna
Ports
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Synchronization signals The primary and secondary synchronization signals are used in the cell
search procedure. The particular sequences which are transmitted for the
PSS and SSS in a given cell are used to indicate the physical layer cell
identity to the UE
The synchronization signals are always transmitted on the 62 centre sub
carriers and specified symbols.
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PSS and SSS Location for FDD
0 1 2 3 4 5 6
Bandwidth
0 1 2 3 4 5
Bandwidth
Normal CP
Extended CP
Radio Frame
Slots 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Repeated in slots 0 and 10
72 Subcarriers
PSS (Primary Synchronization Sequence)
SSS (Secondary Synchronization Sequence)
62 Subcarri
ers
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Synchronization signals There are 504 unique physical layer cell identities in LTE, grouped
into 168 groups of three identities.
The three identities in a group would usually be assigned to cells
under the control of the same eNodeB. Three PSS sequences are
used to indicate the cell identity within the group.
168 SSS sequences are used to indicate the identity of the group.
cell (1) (2)
(1)
(2)
Downlink Synchronization Signals
eNB
UEWhere:
NID = 3NID + NID
NID = 0,…..167NID = 0, 1, or 2
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Physical Cell Identities
eNB
eNB
eNB
PSS - One of 3 Identities
SSS - One of 168 Group Identities
504 Unique Cell Identities
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PSS Correlation
Subframe
Correlation
PSS0
PSS1
PSS2
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SSS Correlation
Subframe
SSS
SSS
Cyclic Shift based on Cell ID and Subframe (0 or 5)
Device can identify Cell ID and frame timing
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Example of SSS Indices
N 1ID m0 m1 N 1
ID m0 m1 N 1ID m0 m1 N 1
ID m0 m1 N 1ID m0 m1
0 0 1 34 4 6 68 9 12 102 15 19 136 22 27
1 1 2 35 5 7 69 10 13 103 16 20 137 23 28
2 2 3 36 6 8 70 11 14 104 17 21 138 24 29
3 3 4 37 7 9 71 12 15 105 18 22 139 25 30
. . . . .
. . . . 167 2 9
33 3 5 67 8 11 101 14 18 135 21 26
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Cell search procedure The first step of cell search is to do matched filtering between the
received signal and the sequences specified for the primary
synchronization signal, When the output of the matched filter
reaches its maximum, the terminal is likely to have found timing
on a 5 ms basis, and the identity within the cell-identity group.
The second step is to detects the cell-identity group, by observing
pairs of slots where the secondary synchronization signal is
transmitted, since each combination (s1, s2) in subframe zero
and five represents one of the cell identity groups uniquely
In the case of the initial synchronization, in addition to the
detection of synchronization signals, the UE proceeds to decode
the Physical Broadcast CHannel (PBCH), from which critical
system information is obtained.
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Cell Search
0 1 2 3 4 5 6 7 8 9
Frame - 10ms
5MHz (25 Resource Blocks)
PSS
SSS
PBCH
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Downlink Reference signals Cell-specific downlink reference signals
The reference signal is used to make channel estimation and carry out
downlink coherent detection and demodulation
The RS sequence also carries unambiguously one of the 504 different
cell identities
Cell-specific reference symbol arrangement in the case of normal CP
length for one antenna port:
R
R
R
R
R
R
R
R
Physical Cell ID = 0R
R
R
R
R
R
R
R
Physical Cell ID = 8
RS position is based on Physical Cell ID
(Physical Cell ID mod 6)
eNB eNB
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Downlink Reference signals Cell-specific downlink reference signals in case of 2 and 4 antenna port
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Downlink Physical channels
Physical broadcast channel (PBCH)
P-BCH transmitted only in the centred frequency, BW is 72
subcarriers
P-BCH use QPSK
P-BCH occupy symbol 7,8,9,10 of the centred 6RB
P-BCH is used to carry BCH for system information broadcast Only MIB (Master Information Block) which consists of a limited number of
the most frequently transmitted parameters essential for initial access to
the cell is carried on PBCH
Other System Information Blocks (SIBs) which, at the physical layer, are
multiplexed together with uncast data are transmitted on the Downlink
Shared Channel
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MIB
Sys
tem
B
andw
idthCRC
Channel CodingRate Matching
ScramblingModulation
Layer MappingPrecoding
Mapping to REs
10ms Frame
PBCH
PBCH-physical broadcast channel
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Downlink Physical channels
Physical downlink shared channel (PDSCH)
PDSCH is used to carry DL-SCH, PCH and BCH
User data, broadcast system information which is not carried
on the PBCH, and paging messages may be transmitted on
PDSCH
Physical multicast channel (PMCH)
PMCH is used to carry MCH for MBMS service
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Downlink Physical channels
Physical control format indicator channel (PCFICH)
Carries information about the number of OFDM symbols used
for transmission of PDCCHs in a subframe.
Three different CFI values are used in the first version of LTE.
In order to make the CFI sufficiently robust each codeword is
32 bits in length. These 32 bits are mapped to 16 resource
elements using QPSK modulation
In order to achieve frequency diversity, the 16 resource
elements carrying the PCFICH are distributed across the
frequency domain. This is done according to a predefined
pattern in the first OFDM symbol in each downlink subframe.
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Downlink Physical channels
Physical downlink control channel (PDCCH) Informs the UE about the resource allocation of PCH and DL-
SCH, and Hybrid ARQ information related to DL-SCH
Carries the uplink scheduling grant
Multiple PDCCHs can be transmitted in a subframe
The set of OFDM symbols possible to use for PDCCH in a
subframe is the first n OFDM symbols where n 3
Physical Hybrid ARQ Indicator Channel (PHICH) Carries Hybrid ARQ ACK/NAKs in response to uplink
transmissions.
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Downlink resource allocation sample
72 center RE
Control channelCFI/PHI/PDCCH
Sync channel PBCH
User 1 PDSCH User 2 PDSCH
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Uplink Reference signals Uplink Reference signal
Two types of uplink reference signals are supported:
Demodulation reference signal (DM RS), associated with transmission of
PUSCH or PUCCH, are primarily used for channel estimation for coherent
demodulation
Sounding reference signal (SRS), not associated with transmission of PUSCH
or PUCCH, primarily used for channel quality determination to enable
frequency-selective scheduling on the uplink
The uplink reference signals in LTE are based on Zadoff–Chu (ZC)
sequences, which satisfy these properties:
Good autocorrelation properties for accurate channel estimation.
Good cross-correlation properties between different RSs to reduce
interference from RSs transmitted on the same resources in other (or, in
some cases, the same) cells.
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Uplink Reference signals
Demodulation reference signal (DM RS)
The DM RSs associated with uplink PUSCH data or PUCCH control
transmissions are primarily provided for channel estimation for
coherent demodulation, and are present in every transmitted uplink
slot.
The DM RSs of a given UE occupy the same bandwidth as its
PUSCH/PUCCH data transmission (same RBs)
The position of uplink reference signals in a slot:
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Uplink Reference signals
Sounding reference signal (SRS)
The subframes in which SRS are transmitted by any UE within the cell
are indicated by cell-specific broadcast signalling
(‘srsSubframeConfiguration’)
The SRS transmissions are always in the last SC-FDMA symbol in the
configured subframes
The eNodeB in LTE may either request an individual SRS transmission
from a UE or configure a UE to transmit SRS periodically until
terminated
The specific SRS bandwidth to be used by a given UE is configured
through RRC signalling
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Uplink Physical channels
Physical uplink shared channel (PUSCH)
carries data from the Uplink Shared Channel (UL-SCH) transport
channel
Physical uplink control channel (PUCCH)
Carries Hybrid ARQ ACK/NAKs in response to downlink
transmission;
Carries Scheduling Request (SR);
Carries CQI reports.
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Uplink Physical channels Physical random access channel (PRACH)
Carries the random access preamble
One or several subframes is reserved for preamble transmission in a frame, and In the frequency domain, the random-access preamble has a bandwidth corresponding to six resource blocks
The physical layer random access burst consists of a cyclic prefix, a preamble, and a guard time to avoid interference
A fixed number (64) of preamble signatures is available
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Initial Procedures
PLMN/Cell Selection
Downlink Synchronization Complete
Power On Cell SearchRACH
Process
Uplink Synchronization Complete
Send Preamble
Identify RACH Preambles
Identify PRACH Format
ReceiveResponse
No
Decode Response
Yes
Send RRC Connection
Request
MAC Connection Resolution
SRB Established
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Uplink Physical channels Contention-based random access procedure
On request of higher layers which should provides: Random access channel parameters, a single preamble is transmitted using an random selected preamble sequence
network transmitting a timing advance command and assigns uplink resources to the terminal to be used in the third step
transmission of the mobile-terminal identity to the network, C-RNTI(LTE-CONNECTED) or a CN terminal identifier(IDLE)
contention-resolution message is transmitted on the DL-SCH, If the terminal has not yet been assigned a C-RNTI, the temporary identity from the second step is promoted to the C-RNTI, Terminals which do not find a match between the identity are considered failed
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LTE channel mapping
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1. Overview
2. Radio interface
3. S1 interface
4. X2 interface
Contents
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EPC EUTRAN
eNode
B
“S1-U”
“S1-MME”
S-GTW
MME
eNode
B
S-GTW
MME
S1 Interface architecture S1 functions:
S1 UE context management function: Establishment/release SAE bearer context, security context, UE S1
signaling connection ID(s), etc.
SAE bearer management functions
GTP-U tunnels management function
S1 Signalling link management function
Intra-LTE handover
Inter-3GPP RAT handover
Paging function
Network sharing function
NAS node selection function
Security function
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S1 Interface
eNB
IP
Layer 2
Layer 1
SCTP
S1AP
Control Plane
S1-MME
MME
IP
Layer 2
Layer 1
UDP
GTP-U
User Plane
eNB
S1-U
S-GW
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1. Overview
2. Radio interface
3. S1 interface
4. X2 interface
Contents
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X2 Interface architecture X2 functions:
Intra LTE-Access-System Mobility Support for UE in LTE_ACTIVE:
Context transfer from source eNB to target eNB;
Control of user plane tunnels between source eNB and target eNB;
Handover cancellation.
Load Management
Inter-cell Interference Coordination
Uplink Interference Load Management;
General X2 management and error handling functions:
Error indication.
Trace functions
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X2 Interface
eNB eNB
X2
IP
Layer 2
Layer 1
SCTP
X2AP
Control Plane
IP
Layer 2
Layer 1
UDP
GTP-U
User Plane
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