3gpp r8 lte overview
Post on 24-Oct-2014
3.970 views
TRANSCRIPT
3GPP R8 LTE Overview
조봉열, Bong Youl (Brian) Cho
Intel Corporation
LTE/MIMO 표준기술 2
Books on LTE
LTE/MIMO 표준기술 3
Books on LTE – cont’d
LTE/MIMO 표준기술 4
Contents
LTE Overview
LTE Radio Interface Architecture
LTE Downlink Transmission
LTE Uplink Transmission
Summary
LTE Overview
LTE/MIMO 표준기술 6
Terminology
LTE (Long Term Evolution)
Evolution of 3GPP Radio Access Technology
E-UTRA
SAE (System Architecture Evolution)
Evolution of 3GPP Core Network Technology
EPC (Evolved Packet Core)
EPS (Evolved Packet System)
Evolution of the complete 3GPP UMTS Radio Access, Packet
Core and its integration into legacy 3GPP/non-3GPP networks
E-UTRAN + EPC
LTE/MIMO 표준기술 7
3GPP LTE
LTE focus is on:
enhancement of the Universal Terrestrial Radio Access (UTRA)
optimisation of the UTRAN architecture
With HSPA (downlink and uplink), UTRA will remain highly competitive for several years
LTE project aims to ensure the continued competitiveness of the 3GPP technologies for the future (started at Nov. 2004)
Motivations
Need for PS optimized system Evolve UMTS towards packet only system
Need for higher data rates Can be achieved with HSDPA/HSUPA and/or new air interface defined by 3GPP LTE
Need for high quality of services Use of licensed frequencies to guarantee quality of services
Always-on experience (reduce control plane latency significantly)
Reduce round trip delay
Need for cheaper infrastructure Simplify architecture, reduce number of network elements
Most data users are less mobile
LTE/MIMO 표준기술 8
Detailed Requirements* Peak data rate
Instantaneous downlink peak data rate of 100 Mb/s within a 20 MHz downlink
spectrum allocation (5 bps/Hz)
Instantaneous uplink peak data rate of 50 Mb/s within a 20MHz uplink spectrum
allocation(2.5 bps/Hz)
Control-plane latency
Transition time of less than 100 ms from a camped state, such as Release 6
Idle Mode, to an active state such as Release 6 CELL_DCH
Transition time of less than 50 ms between a dormant state such as Release 6
CELL_PCH and an active state such as Release 6 CELL_DCH
Control-plane capacity
At least 200 users per cell should be supported in the active state for spectrum
allocations up to 5 MHz
User-plane latency
Less than 5 ms in unload condition (ie single user with single data stream) for
small IP packet
* 3GPP TR 25.913, Technical Specification Group RAN: Requirements for Evolved UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN), Release 8, Version 8.0.0, Dec. 2008
LTE/MIMO 표준기술 9
Detailed Requirements Average user throughput
Downlink: average user throughput per MHz, 3 to 4 times Release 6 HSDPA
Uplink: average user throughput per MHz, 2 to 3 times Release 6 Enhanced Uplink
Cell edge user throughput
Downlink: user throughput per MHz at 5% of CDF, 2 to 3 times Release 6 HSDPA
Uplink: user throughput per MHz at 5% of CDF, 2 to 3 times Release 6 Enhanced Uplink
Spectrum efficiency
Downlink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 3 to 4 times Release 6 HSDPA )
Uplink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 2 to 3 times Release 6 Enhanced Uplink
Mobility
E-UTRAN should be optimized for low mobile speed from 0 to 15 km/h
Higher mobile speed between 15 and 120 km/h should be supported with high performance
Mobility across the cellular network shall be maintained at speeds from 120 km/h to 350 km/h (or even up to 500 km/h depending on the frequency band)
Coverage
Throughput, spectrum efficiency and mobility targets above should be met up to 5 km cells, and with a slight degradation up to 30 km cells. Cells range up to 100 km should not be precluded.
LTE/MIMO 표준기술 10
Detailed Requirements Spectrum flexibility
E-UTRA shall operate in spectrum allocations of different sizes, including 1.25 MHz, 2.5
MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz in both the uplink and downlink. Operation
in paired and unpaired spectrum shall be supported
Co-existence and Inter-working with 3GPP RAT (UTRAN, GERAN)
Architecture and migration
Single E-UTRAN architecture
The E-UTRAN architecture shall be packet based, although provision should be made
to support systems supporting real-time and conversational class traffic
E-UTRAN architecture shall support an end-to-end QoS
Backhaul communication protocols should be optimized
Radio Resource Management requirements
Enhanced support for end to end QoS
Support of load sharing and policy management across different Radio Access
Technologies
Complexity
Minimize the number of options
No redundant mandatory features
LTE/MIMO 표준기술 11
LTE System Performance
Peak Data Rate
150.8
302.8
51.0
75.4
1) ~14% reference signal overhead (4 Tx antennas in DL)
~10% common channel overhead (1 UE/subframe)
~7% waveform overhead (CP)
~10% guard band
~(1/1) code rate
2) ~14% reference signal overhead (1 Tx antenna in UL)
~0.6% random access overhead
~7% waveform overhead (CP)
~10% guard band
~(1/1) code rate
1)
2)
LTE/MIMO 표준기술 12
LTE System Performance – cont’d
Downlink Spectral Efficiency
Uplink Spectral Efficiency
LTE/MIMO 표준기술 13
LTE Key Features Downlink: OFDMA (Orthogonal Frequency Division Multiple Access)
Less critical AMP efficiency in BS side
Concerns on high RX complexity in terminal side
Uplink: SC-FDMA (Single Carrier-FDMA)
Less critical RX complexity in BS side
Critical AMP complexity in terminal side (Cost, power Consumption, UL coverage)
Single node RAN (eNB)
Support FDD (frame type 1) & TDD (frame type 2 for TD-SCDMA evolution) <cf> H-FDD MS
User data rates
DL (baseline): 150.8 Mbps @ 20 MHz BW w/ 2x2 SU-MIMO
UL (baseline): 75.4 Mbps @ 20 MHz BW w/ non-MIMO or 1x2 MU-MIMO
Radio frame: 10 ms (= 20 slots), Sub-frame: 1 ms (= 2 slots), Slot: 0.5 ms
TTI: 1 ms
HARQ
Incremental redundancy is used as the soft combining strategy
Retransmission time: 8 ms
Modulation
DL/UL data channel = QPSK/16QAM/64QAM
Hard handover-based mobility
Making MS cheap as much as possible by
moving all the burdens from MS to BS
LTE/MIMO 표준기술 14
LTE Key Features – cont’d MIMO SM (Spatial Multiplexing), Beamforming, Antenna Diversity
Min requirement: 2 eNB antennas & 2 UE rx antennas
DL: Single-User MIMO up to 4x4 supportable, MU-MIMO
UL: MU-MIMO
Resource block
12 subcarriers with subcarrier BW of 15kHz “180kHz”
24 subcarriers with subcarrier BW of 7.5kHz (only for MBMS)
Subcarrier operation
Frequency selective by localized subcarrier
Frequency diversity by distributed subcarrier & frequency hopping
Frequency hopping
Intra-TTI: UL (once per 0.5ms slot), DL (once per 66us symbol)
Inter-TTI: across retransmissions
Bearer services
Packet only – no circuit switched voice or data services are supported
Voice must use VoIP or CS-Fallback
MBSFN
Multicast/Broadcast over a Single Frequency Network
To support a Multimedia Broadcast and Multicast System (MBMS)
Time-synchronized common waveform is transmitted from multiple cells for a given duration
The signal at MS will appear exactly as a signal transmitted from a single cell site and subject to multi-path
Not only “improve the received signal strength” but also “eliminate inter-cell interference”
LTE/MIMO 표준기술 15
Resource & Channel Estimation in OFDM
Time-frequency grid
Time-frequency grid with known reference symbols
LTE/MIMO 표준기술 16
E-UTRAN Architecture*
eNB
MME / S-GW MME / S-GW
eNB
eNB
S1
S1
S1
S1
X2X2
X2
E-UTRAN
LTE/MIMO 표준기술 17
Functional Split b/w E-UTRAN and EPC*
internet
eNB
RB Control
Connection Mobility Cont.
eNB Measurement
Configuration & Provision
Dynamic Resource
Allocation (Scheduler)
PDCP
PHY
MME
S-GW
S1
MAC
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
LTE/MIMO 표준기술 18
Security KeyReceiver
AuthenticationRelay
Base StationHandover Function
Service FlowManagement
RRC
BSPMIP Client
AAA Client
Authenticator
Location Register
Idle-Mode &Paging Control
DHCP Proxy/Relay
Service Flow Authenticator
Security KeyDistributor
ASN GW
WiMAX R3
WiMAX R6
Data Path Function/FA
WiMAXControl Functions(Similar to 3GPP MME)
WiMAXData-Path Functions
(Similar to 3GPP S-GW)
WiMAX R4
CSN
ASN
Compare with WiMAX ASN-GW
LTE/MIMO 표준기술 19
EPS is all PS (IP) based
* Qualcomm
2G initial
architecture
(GSM)
(1991)
2G+3G
architecture
(GPRS/EDGE/UMTS)
(2000)
IMS
Introduction
(2004)
EPS
architecture
(2008)
LTE/MIMO 표준기술 20
3GPP Architecture EvolutionTowards Flat Architecture
* NSN
LTE/MIMO 표준기술 21
Duplexing
FDD
TDD
LTE/MIMO 표준기술 22
LTE Modulation Schemes
LTE/MIMO 표준기술 23
UE-eNB Communication Link
“Single and same link of communication for DL and UL”
DL serving cell = UL serving cell
No UL nor DL macro-diversity
Hard handover-based mobility
- UE assisted (based on measurement reports) and network controlled
(explicit handover command) by default
- During handover, UE uses a RACH-based mobility procedure to access
the target cell
- Handover is initiated by the UE when it detects a Radio Link failure
condition
Load indicator for inter-cell load control and interference coordination
- Transmitted over X2 interface
LTE/MIMO 표준기술 24
OFDMA: Interference Coordination
Cell-A
Cell-B
Cell-C
A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3 C4A5
B5 C5
A1 A2 A3 A4 B3 B4 C1 C2 C3 C4A5 B5 C5
C2 C3 C4 C5
Pow
er
B2
C1
A5A4 B5B4A3A2A1 B3B2B1
good users weak users
good user weak user
weak users good users
B1
LTE/MIMO 표준기술 25
ICIC* in LTE Standards Inter-cell interference coordination (ICIC)
To aid downlink ICIC
Relative narrowband transmission-power indicator
A cell can provide this information to neighboring cells, indicating the part of the
bandwidth where it intends to limit the transmission power. A cell receiving the indication
can schedule its downlink transmissions within this band, reducing the output power or
completely freeing the resources on complementary parts of the spectrum
To aid uplink ICIC
High interference indicator
The high-interference indicator provides information to neighboring cells about the part of
the cell bandwidth upon which the cell intends to schedule its cell-edge users. Because
cell-edge users are susceptible to inter-cell interference, upon receiving the high-
interference indicator, a cell might want to avoid scheduling certain subsets of its own
users on this part of the bandwidth.
Overload indicator
The overload indicator provides information on the uplink interference level experienced
in each part of the cell bandwidth. A cell receiving the overload indicator may reduce the
interference generated on some of these resource blocks by adjusting its scheduling
strategy
LTE/MIMO 표준기술 26
OFDMA: Frequency Selective Gain
Loading gain by “frequency selective scheduling”
Localized subcarrier assignment Distributed subcarrier assignment
LTE/MIMO 표준기술 27
Multi-cell Broadcast in OFDM System
Broadcast vs. Unicast transmission
Equivalence between simulcast transmission and multi-path propagation
LTE/MIMO 표준기술 28
E-UTRA Frequency Band*
* 3GPP TS 36.101, E-UTRA: UE radio transmission and reception, Release 9, V9.0.0, June 2009
Korea?
Korea?
Japan, Korea?
Europe?
China?
US?
China?
LTE/MIMO 표준기술 29
LTE Spectrum Fragmentation
LTE/MIMO 표준기술 30
E-UTRA Channel Bandwidth*
1RB = 180kHz 6RBs = 1.08MHz, 100RBs = 18MHz
6RBs (72 subcarriers) with 128 FFT, 100RBs (1200 subcarriers) with 2048 FFT
* 3GPP TS 36.101, E-UTRA: UE radio transmission and reception, Release 9, V9.0.0, June 2009
LTE/MIMO 표준기술 31
OFDM Parameters
LTE Radio Interface Architecture
LTE/MIMO 표준기술 33
LTE Protocol Architecture (DL)
LTE/MIMO 표준기술 34
PDCP and RLC
PDCP
Header compression and corresponding decompression
Ciphering and deciphering
Integrity protection and verification
RLC
Transferring PDUs from higher layers, i.e. from RRC or PDCP
Error correction with ARQ, concatenation/segmentation, in-sequence
delivery and duplicate detection
Protocol error handling (e.g. signalling error)
LTE/MIMO 표준기술 35
EPS Bearer Service Architecture
LTE/MIMO 표준기술 36
EPS Bearer Terminology
Quality of service
GBR bearer: Guaranteed bit rate
Non-GBR bearer: No guaranteed bit rate
Establishment time
Default bearer
Established when UE connects to PDN
Provides always-on connectivity
Always non-GBR
Dedicated bearer established later
Can be GBR or non-GBR
Every EPS bearer
QoS class identifier (QCI): This is a number which describes the error rate and
delay that are associated with the service.
Allocation and retention priority (ARP): This determines whether a bearer can be
dropped if the network gets congested, or whether it can cause other bearers to be
dropped. Emergency calls might be associated with a high ARP, for example.
LTE/MIMO 표준기술 37
QCI (QoS Class Identifier)
LTE/MIMO 표준기술 38
Logical Channels: “type of information it carries”
Control Channels
Broadcast Control Channel (BCCH)
used for transmission of system information from the network to all UEs in a cell
Paging Control Channel (PCCH)
used for paging of UEs whose location on cell level is not known to the network
Common Control Channel (CCCH)
used for transmission of control information in conjunction with random access, i.e., used for UEs having no RRC connection
Dedicated Control Channel (DCCH)
used for transmission of control information to/from a UE, i.e., used for UEs having RRC connection (e.g. handover messages)
Multicast Control Channel (MCCH)
used for transmission of control information required for reception of MTCH
Traffic Channels
Dedicated Traffic Channel (DTCH)
used for transmission of user data to/from a UE
Multicast Traffic Channel (MTCH)
used for transmission of MBMS services
LTE/MIMO 표준기술 39
Transport Channels: “how”, “with what characteristics”
Downlink
Broadcast Channel (BCH)
A fixed TF
Used for transmission of parts of BCCH, so called MIB
Paging Channel (PCH)
Used for transmission of paging information from PCCH
Supports discontinuous reception (DRX)
Downlink Shared Channel (DL-SCH)
Main transport channel used for transmission of downlink data in LTE
Used also for transmission of parts of BCCH, so called SIB
Supports discontinuous reception (DRX)
Multicast Channel (MCH)
Used to support MBMS
Uplink
Uplink Shared Channel (UL-SCH)
Uplink counterpart to the DL-SCH
Random Access Channel(s) (RACH)
Transport channel which doesn’t carry transport blocks
Collision risk
LTE/MIMO 표준기술 40
DL Physical Channels Physical Downlink Shared Channel (PDSCH)
실제 downlink user data를 전송하기 위한 transport channel인 DL-SCH와 paging 정보를 전송하기 위한 transport channel인 PCH가 매핑
동적 방송 정보인 SI (System Information) 값들도 RRC 메시지 형태로 DL-SCH를 통해 전송되므로 이 역시 PDSCH로 매핑이 경우는 전체 셀 영역으로 도달될 수 있는 능력이 요구되기도 함
Physical Broadcast Channel (PBCH)
UE가 cell search과정을 마친 후에 최초로 검출하는 채널로서, 다른 물리 계층 채널들을 수신하기 위하여 반드시 필요한 기본적인 시스템 정보들인 MIB (Master Information Block)를 전송하기 위한 transport channel인 BCH가 매핑
Physical Multicast Channel (PMCH)
방송형 데이터를 전송하기 위한 transport channel 인 MCH가 매핑
Physical Control Format Indicator Channel (PCFICH)
매 subframe마다 전송, only one PCFICH in each cell
Informs UE about CFI which indicates the number of OFDM symbols used for PDCCHs transmission
Physical Downlink Control Channel (PDCCH)
Informs UE about resource allocation of PCH and DL-SCH
HARQ information related to DL-SCH
UL scheduling grant
Physical HARQ Indicator Channel (PHICH)
Carries HARQ ACK/NACKs in response to UL transmission
LTE/MIMO 표준기술 41
UL Physical Channels
Physical Uplink Shared Channel (PUSCH)
Uplink counterpart of PDSCH
Carries UL-SCH
Physical Uplink Control Channel (PUCCH)
Carries HARQ ACK/NAKs in response to DL transmission
Carries Scheduling Request (SR)
Carries channel status reports such as CQI, PMI and RI
At most one PUCCH per UE
Physical Random Access Channel (PRACH)
Carries the random access preamble
LTE/MIMO 표준기술 42
LTE Channel Mapping
Downlink
Uplink
LTE/MIMO 표준기술 43
<cf> WCDMA DL Channel Mapping
BCCH PCCH CCCH DCCH CTCH DTCH
BCH(DL)
PCH(DL)
RACH(UL)
FACH(DL)
DSCH(DL)
CPCH(UL)
DCH(UL&DL)
P- CCPCH S- CCPCH PRACH PDSCH PCPCH DPDCHSCH,CPICH,AICH,
PICH,DPCCH
Logical Ch
Transport Ch
Physical Ch
Control Plane User Plane
LTE/MIMO 표준기술 44
BCCH and PCH on PDSCH
* Qualcomm
LTE Downlink Transmission
LTE/MIMO 표준기술 46
Frame Structure: Type 1 for FDD
where, Ts = 1/(15000 x 2048) seconds “the smallest time unit in LTE”
Tf = 307200 x Ts = 10 ms
#0 #1 #2 #3 #19
One slot, Tslot = 15360Ts = 0.5 ms
One radio frame, Tf = 307200Ts=10 ms
#18
One subframe
LTE/MIMO 표준기술 47
Frame Structure: Type 2 for TDD
One slot,
Tslot=15360Ts
GP UpPTSDwPTS
One radio frame, Tf = 307200Ts = 10 ms
One half-frame, 153600Ts = 5 ms
30720Ts
One subframe,
30720Ts
GP UpPTSDwPTS
Subframe #2 Subframe #3 Subframe #4Subframe #0 Subframe #5 Subframe #7 Subframe #8 Subframe #9
LTE/MIMO 표준기술 48
Frame Structure: FDD/TDD
LTE/MIMO 표준기술 49
DL Slot Structure
: Downlink bandwidth configuration,
expressed in units of
: Resource block size in the
frequency domain, expressed as a
number of subcarriers
: Number of OFDM symbols in an
downlink slot
RBscN
RBscN
DLRBN
DLsymbN
DLsymbN OFDM symbols
One downlink slot slotT
0l 1DLsymb Nl
RB
scD
LR
BN
N
sub
carr
iers
RB
scN
sub
carr
iers
RBsc
DLsymb NN
Resource block
resource elements
Resource element ),( lk
0k
1RBsc
DLRB NNk
The minimum RB the eNB uses for LTEscheduling is “1ms (1subframe) x 180kHz(12subcarriers @ 15kHz spacing)”
LTE/MIMO 표준기술 50
Definitions Resource Grid
Defined as subcarriers in frequency domain and OFDM symbols in time domain
The quantity depends on the DL transmission BW configured in the cell and shall fulfill
The set of allowed values for is given by TS 36.101, TS 36.104
Resource Block (1 RB = 180 kHz)
Defined as “consecutive” subcarriers in frequency domain and “consecutive” OFDM
symbols in time domain
Corresponding to one slot in the time domain and 180 kHz in the frequency domain
Resource Element
Uniquely defined by the index pair in a slot where and
are the indices in the frequency and time domain, respectively
1106 DL
RB N
RB
sc
DL
RB NN DL
symbN
RBscN
lk,
DL
RBN
DL
RBN
DL
symbN
1,...,0 DL
symb Nl1,...,0 RB
sc
DL
RB NNk
LTE/MIMO 표준기술 51
Normal CP & Extended CP
LTE/MIMO 표준기술 52
Resource Blocks Allocation
* Award Solutions
LTE/MIMO 표준기술 53
Resource-element groups (REG)
Basic unit for mapping of PCFICH,
PHICH, and PDCCH
Resource-element groups are used
for defining the mapping of control
channels to resource elements.
Mapping of a symbol-quadruplet
onto a resource
-element group is defined such that
elements are mapped to resource
elements of the resource-element
group not used for cell-specific
reference signals in increasing order
of l and k
)3(),2(),1(),( iziziziz
)(iz
),( lk
n+
0n
+1
n+
2n
+3
n+
4
n+
5n
+6
n+
7
n+
0n
+1
n+
2n
+3
n+
4n
+5
n+
6
LTE/MIMO 표준기술 54
DL Physical Channel Processing
scrambling of coded bits in each of the code words to be transmitted on a physical channel
modulation of scrambled bits to generate complex-valued modulation symbols
mapping of the complex-valued modulation symbols onto one or several transmission layers
precoding of the complex-valued modulation symbols on each layer for transmission on the antenna ports
mapping of complex-valued modulation symbols for each antenna port to resource elements
generation of complex-valued time-domain OFDM signal for each antenna port
OFDM signal
generationLayer
Mapper
Scrambling
Precoding
Modulation
Mapper
Modulation
Mapper
Resource
element mapper
OFDM signal
generationScrambling
code words layers antenna ports
Resource
element mapper
LTE/MIMO 표준기술 55
Channel Coding
Turbo code
PCCC (exactly the same as in WCDMA/HSPA)
QPP (quadratic polynomial permutation) interleaver
LTE/MIMO 표준기술 56
000
001
011
010
110
111
101
111
000 001 011 010 110 111 101 111
64-QAM
0 1
0
1
QPSK
00 01 11 10
00
01
11
10
16-QAM
Modulation
PDSCH, PMCH: QPSK, 16QAM, 64QAM
PBCH, PCFICH, PDCCH: QPSK
PHICH: BPSK on I/Q
LTE/MIMO 표준기술 57
DL Layer Mapping and Precoding
Explained in MIMO session
LTE/MIMO 표준기술 58
DL OFDM Signal Generation
OFDM Parameters
N = 2048 for f=15kHz
N = 4096 for f=7.5kHz
Check with resource block parameters
(160+2048) x Ts = 71.88us
(144+2048) x Ts = 71.35us
71.88us + 71.35us x 6 = 0.5ms
Normal Cyclic Prefix = 160 Ts = 5.2 usNormal Cyclic Prefix = 144 Ts = 4.7 us Extended Cyclic Prefix = 512 Ts = 16.7 usExtended Cyclic Prefix for MBMS = 1024 Ts = 33.3 us
s,CP0 TNNt l
LTE/MIMO 표준기술 59
DL Physical Channels & Signals
Physical channels
Physical Downlink Shared Channel (PDSCH)
Physical Broadcast Channel (PBCH)
Physical Multicast Channel (PMCH)
Physical Control Format Indicator Channel (PCFICH)
Physical Downlink Control Channel (PDCCH)
Physical HARQ Indicator Channel (PHICH)
Physical signals
Reference Signals
Cell-specific RS, associated with non-MBSFN transmission
Aid coherent detection (pilot)
Reference channel for CQI from UE to eNB
MBSFN RS, associated with MBSFN transmission
UE-specific RS
Synchronization Signals
Carries frequency and symbol timing synchronization
PSS (Primary SS) and SSS (Secondary SS)
LTE/MIMO 표준기술 60
Equivalent Channel/Signal Mapping
Across Different Systems
LTE WCDMA/HSPA WiMAX
PDSCH HS-PDSCH, SCCPCH DL Data Burst
PBCH PCCPCH DCD, Preamble
PMCH DL Data Burst
PCFICH FCH
PDCCH HS-SCCH, E-AGCH,
E-RGCH
DL-MAP, UL-MAP
PHICH E-HICH DL Data Burst
Cell-specific
Reference Signal
CPICH Pilot Signal (common)
UE-specific Reference
Signal
With secondary
scrambling code
Pilot Signal (dedicated)
Sync Signal SCH Preamble
LTE/MIMO 표준기술 61
DL Reference Signals
Cell-specific reference signals
Are transmitted in every downlink subframe, and span entire cell BW
Used for coherent demodulation of any downlink transmission “except” when so-
called non-codebook-based beamforming is used
Used for initial cell search
Used for downlink signal strength measurements for scheduling and handover
Using antenna ports {0, 1, 2, 3}
MBSFN reference signals
Used for channel estimation for coherent demodulation of signals being transmitted
by means of MBSFN
Using antenna port 4
UE-specific reference signals
Is specifically intended for channel estimation for coherent demodulation of DL-SCH
when non-codebook-based beamforming is used.
Are transmitted only within the RB assigned for DL-SCH to that specific UE
Using antenna port 5
* Antenna port is different from physical antenna. One designated RS per antenna port.
LTE/MIMO 표준기술 62
Cell-Specific Reference Signals
When estimating the channel for a certain RB, UE may not only use the
reference symbols within that RB but also, in frequency domain, neighbor
RBs, as well as reference symbols of previously received slots/subframes
Pseudo-random sequence generation
is the slot number within a radio frame.
is the OFDM symbol number within the slot.
The pseudo-random sequence c(i) is a length-31 Gold sequence.
The complex values of cell-specific reference symbols is based on length-31
Gold pseudo-random sequence. The length-31 Gold psuedo-random
sequence is generated with the seed, based on the slot number, symbol
number, cell identity, and cyclic prefix type.
12,...,1,0 ,)12(212
1)2(21
2
1)( DLmax,
RB, s Nmmcjmcmr nl
LTE/MIMO 표준기술 63
Cell-Specific Reference Signals – cont’d
While the sequence itself if 231-1
bits in length, the number of bits
from the sequence selected for
transmission is based on the largest
channel bandwidth, which is
currently 20 MHz.
* Qualcomm
LTE/MIMO 표준기술 64
Relationship with Cell Identity
504 unique Cell ID:
168(N1) Cell ID groups, 3 (N2) Cell ID within each group
Cell ID = 3xN1+N2 = 0 ~ 503 index
504 pseudo-random sequences
One to one mapping between the Cell ID and Pseudo-random sequences
Cell-specific Frequency Shift (N1 mod 6)
1 RE shift from current RS position in case of next Cell ID index
Each shift corresponds to 84 different cell identities, that is 6 shifts jointly cover all
504 cell identities.
Effective with RS boosting to enhance reference signal SIR by avoiding the collision
of boosted RSs from neighboring cells (assuming time synchronization)
LTE/MIMO 표준기술 65
Cell-Specific RS Mapping
0l
0R
0R
0R
0R
6l 0l
0R
0R
0R
0R
6l
One
ante
nna
port
Tw
o a
nte
nna
port
s
Resource element (k,l)
Not used for transmission on this antenan port
Reference symbols on this antenna port
0l
0R
0R
0R
0R
6l 0l
0R
0R
0R
0R
6l 0l
1R
1R
1R
1R
6l 0l
1R
1R
1R
1R
6l
0l
0R
0R
0R
0R
6l 0l
0R
0R
0R
0R
6l 0l
1R
1R
1R
1R
6l 0l
1R
1R
1R
1R
6l
Four
ante
nna
port
s
0l 6l 0l
2R
6l 0l 6l 0l 6l
2R
2R
2R
3R 3R
3R 3R
even-numbered slots odd-numbered slots
Antenna port 0
even-numbered slots odd-numbered slots
Antenna port 1
even-numbered slots odd-numbered slots
Antenna port 2
even-numbered slots odd-numbered slots
Antenna port 3
Overhead Normal CP Extended CP
1 Tx ant 4.76% 5.56%
2 Tx ant 9.52% 11.11%
4 Tx ant 14.29% 15.87%
LTE/MIMO 표준기술 66
MBSFN RS Mapping
LTE/MIMO 표준기술 67
MBSFN RS Mapping
LTE/MIMO 표준기술 68
UE-specific RS on top of Cell-specific RS
UE-specific RS (antenna port 5)
12 symbols per RB pair
DL CQI estimation is always based on cell-specific RS (common RS)
LTE/MIMO 표준기술 69
Cell ID with PSS & SSS
504 unique physical-layer cell identities
168 unique physical-layer cell-identity groups (0~167)
3 physical-layer identity within physical-layer cell-identity group (0~2)
Primary SS (PSS) and Secondary SS (SSS)
SSS (Cell ID Group)
PSS (Cell ID index
within a Group)
Physical Layer Cell ID
• • •
0 1 2 • • •
0 1 2 …
0 1 2 3 … 167• • • • •
• • •
0 1 2
• • • • • • • • •
0 1 2 3 4 5 501 502 503
LTE/MIMO 표준기술 70
Synchronization Signals
SS is using single antenna port
However, SS can be with UE-transparent transmit antenna scheme (e.g.
PVS, TSTD, CDD)
Primary SS (PSS) and Secondary SS (SSS)
0.5ms slot
LTE/MIMO 표준기술 71
Primary Synchronization Signal The sequence used for the primary synchronization signal is generated from a frequency-
domain Zadoff-Chu sequence (Length-62)
For frame structure type 1, PSS is mapped to the last OFDM symbol in slots 0 and 10
No need to know CP length
The sequence is mapped to REs (6 RBs) according to
Cell ID detection within a cell ID group (3 hypotheses)
Half-frame timing detection (Repeat the same sequence twice)
61,...,32,31
30,...,1,0)(
63
)2)(1(
63
)1(
ne
nend
nnuj
nunj
u
61,...,0 ,1 ,2
31 , DLsymb
RBsc
DLRB
, nNlNN
nknda lk
LTE/MIMO 표준기술 72
Secondary Synchronization Signal The sequence used for the second synchronization signal is an interleaved concatenation
of two length-31 binary sequences (X and Y)
The concatenated sequence is scrambled with a scrambling sequence given by PSS
The combination of two length-31 sequences defining SSS differs between slot 0 (SSS1)
and slot 10 (SSS2) according to
where
Blind detection of CP-length (2 FFT operations are needed)
The same antenna port as for the primary sync signal
Mapped to 6 RBs
5 subframein )(
0 subframein )()12(
5 subframein )(
0 subframein )()2(
)(11
)(0
)(11
)(1
0)(
1
0)(
0
10
01
1
0
nzncns
nzncnsnd
ncns
ncnsnd
mm
mm
m
m
300 n
LTE/MIMO 표준기술 73
Synchronization Signals – cont’d Cell ID group detection (the set of valid combination of X and Y for SSS are 168)
Frame boundary detection (the m-sequences X and Y are swapped b/w SSS1 and SSS2)
LTE/MIMO 표준기술 74
Structure of SSS
LTE/MIMO 표준기술 75
LTE Cell Search Primary SSSymbol timing acquisitionFrequency synchronizationCell ID detection within a cell group ID (3 hypotheses)Half-frame boundary detection
Secondary SSCell group ID detection (168 hypotheses)Frame boundary detection (2 hypotheses)CP-length detection (2 hypotheses)
BCH40ms BCH period timing detectioneNB # of tx antenna detectionMIB acquisition (Operation BW, SFN, etc…)
PCFICH PDCCH reception
SIB acquisition within PDSCH
Map Cell ID to cell-specific RS
Random access with PRACH
LTE/MIMO 표준기술 76
PCFICH
The number of OFDM symbols used for control channel can be varying per TTI
CFI (Control Format Indication)
Information about the number of OFDM symbols (1~4) used for transmission of PDCCHs in a
subframe
PCFICH carries CFI
2 bits 32 bits (block coding) 32 bits (cell specific scrambling) 16 symbols (QPSK)
Mapping to resource elements: 4 REG (16 RE excluding RS) in the 1st OFDM symbol
Spread over the whole system bandwidth
To avoid the collisions in neighboring cells, the location depends on cell identity
Transmit diversity is applied which is identical to the scheme applied to BCH
LTE/MIMO 표준기술 77
PCFICH Processing
LTE/MIMO 표준기술 78
PHICH
HARQ ACK/NAK in response to UL transmission
HI codewords with length of 12 REs = 4 (Walsh spreading) x 3 (repetition)
3 groups of 4 contiguous REs (not used for RS and PCFICH)
BPSK modulation with I/Q multiplexing
SF4 x 2 (I/Q) = 8 PHICHs in normal CP
Cell-specific scrambling
Tx diversity, the same antenna ports as PBCH
Typically, PHICH is transmitted in the first OFDM symbol only
For FDD, an uplink transport block received in subframe n should be acknowledged on the
PHICH in subframe n+4
LTE/MIMO 표준기술 79
PHICH Processing
LTE/MIMO 표준기술 80
PCFICH/PHICH RE Mapping
symbol
Su
bc
arrie
r
Example for 5 MHz BW LTE
LTE/MIMO 표준기술 81
PDCCH PDCCH is used to carry DCI where DCI includes;
Downlink scheduling assignments, including PDSCH resource indication, transport
format, HARQ-related information, and control information related to SM (if
applicable).
Uplink scheduling grants, including PUSCH resource indication, transport format, and
HARQ-related information.
Uplink power control commands
DL assignment
Regular unicast data – RB assignment, transport block size, retransmission sequence
number
Scheduling of paging messages – acts as a “PICH”
Scheduling of SIBs
Scheduling of RA responses
UL power control commands
UL grant
Regular unicast data
Request for aperiodic CQI reports
Power control command, cyclic shift of DM RS
LTE/MIMO 표준기술 82
PDCCH DCI Format
DCI Formats
Usage Details
0 UL grant For scheduling of PUSCH
1
DL assign-ment
For scheduling of one PDSCH codeword (SIMO, TxD)
1AFor compact scheduling of one PDSCH codeword (SIMO, TxD) and random access procedure initiated by a PDCCH order
1BFor compact scheduling of one PDSCH codeword with precoding information (CL single-rank)
1CFor very compact scheduling of one PDSCH codeword (paging, RACH response and dynamic BCCH scheduling)
1DFor compact scheduling of one PDSCH codeword with precoding & power offset information
2 For scheduling PDSCH to UEs configured in CL SM
2A For scheduling PDSCH to UEs configured in OL SM
3Power control
For transmission of TPC commands for PUCCH/PUSCH with 2-bit power adjustment
3AFor transmission of TPC commands for PUCCH/PUSCH with single bit power adjustment
LTE/MIMO 표준기술 83
Downlink Assignment
Major contents of different DCI formats: not exhaustive
DCI format 0/1A indication [1 bit]
Distributed transmission flag [1 bit]
Resource-block allocation [variable]
For the first (or only) transport block
MCS [5 bit]
New-data indicator [1 bit]
Redundancy version [2 bit]
For the second transport block (present in DCI format 2 only)
MCS [5 bit]
New-data indicator [1 bit]
Redundancy version [2 bit]
HARQ process number [3 bit for FDD]
Information related to SM (present in DCI format 2 only)
Pre-coding information [3 bit for 2 antennas, 6 bit for 4 antennas in CL-SM]
Number of transmission layer
HARQ swap flag [1 bit]
Transmit power control (TPC) for PUCCH [2 bit]
Identity (RNTI) of the terminal for which the PDCCH transmission is intended [16 bit]
LTE/MIMO 표준기술 84
Uplink Grants
Major contents of DCI format 0 for UL grants: not exhaustive
DCI format 0/1A indication [1 bit]
Hopping flag [1 bit]
Resource-block allocation [variable]
MCS [5 bit]
New-data indicator [1 bit]
Phase rotation of UL demodulation reference signal [3 bit]
Channel-status request flag [1 bit]
Transmit power control (TPC) for PUSCH [2 bit]
Identity (RNTI) of the terminal for which the PDCCH transmission is intended [16 bit]
The time b/w reception of an UL scheduling grant on a PDCCH and the
corresponding transmission on UL-SCH are fixed
For FDD, the time relation is the same as for PHICH
Uplink grant received in downlink subframe n applies to uplink subframe n+4
LTE/MIMO 표준기술 85
PDCCH Processing
C-RNTI DL-SCH
SI-RNTI BCCH
P-RNTI PCH
RA-RNTI RA Response
TPC-RNTI TPC
LTE/MIMO 표준기술 86
System Information Master information block (MIB) includes the following information:
Downlink cell bandwidth [4 bit]
PHICH duration [1 bit]
PHICH resource [2 bit]
System Frame Number (SFN) except two LBSs
Etc…
LTE defines different SIBs:
SIB1 includes info mainly related to whether an UE is allowed to camp on the cell. This includes info about the
operator(s) and about the cell (e.g. PLMN identity list, tracking area code, cell identity, minimum required Rx
level in the cell, etc), DL-UL subframe configuration in TDD case, and the scheduling of the remaining SIBs.
SIB1 is transmitted every 80ms.
SIB2 includes info that UEs need in order to be able to access the cell. This includes info about the UL cell
BW, random access parameters, and UL power control parameters. SIBs also includes radio resource
configuration of common channels (RACH, BCCH, PCCH, PRACH, PDSCH, PUSCH, PUCCH, and SRS).
SIB3 mainly includes info related to cell-reselection.
SIB4-8 include neighbor-cell-related info. (E-UTRAN, UTRAN, GERAN, cdma2000)
SIB9 contains a home eNB identifier
SIB10/11 contains ETWS (Earthquake and Tsunami Warning System) notification
More to be added
MIB mapped to PBCH
Other SIBs mapped to PDSCH
LTE/MIMO 표준기술 87
BCH on PBCH To broadcast a certain set of cell and/or system-specific information
Requirement to be broadcast in the entire coverage area of the cell
BCH transmission
The coded BCH transport block is mapped to four subframes (slot #1 in subframe #0) within a 40ms interval
40ms timing is blindly detected (no explicit signaling indicating 40ms timing)
Each subframe is assumed to be self-decodable, i.e. the BCH can be decoded from a single reception, assuming sufficiently good channel conditions
LTE/MIMO 표준기술 88
BCH on PBCH – cont’d Single (fixed-size) transport block per TTI (40 ms)
No HARQ
Cell-specific scrambling, QPSK with ½ tail-biting Conv. Code, Tx diversity(1,2,4)
BCH mapped to 4 OFDM symbols within a subframe in time-domain at 6 RBs
(72 subcarriers) excluding DC in freq-domain
PBCH is mapped into RE assuming RS from 4 antennas are used at eNB,
irrespective of the actual number of TX antenna
Different transmit diversity schemes per # of antennas
# of ant=2: SFBC
# of ant=4: SFBC + FSTD (Frequency Switching Transmit Diversity)
No explicit bits in the PBCH to signal the number of TX antennas at eNB
PBCH encoding chain includes CRC masking dependent on the number of
configured TX antennas at eNB
Blind detection of the number of TX antenna using CRC masking by UE
LTE/MIMO 표준기술 89
PBCH Processing
LTE/MIMO 표준기술 90
LTE Cell SearchPrimary SSSymbol timing acquisitionFrequency synchronizationCell ID detection within a cell group ID (3 hypotheses)Half-frame boundary detection
Secondary SSCell group ID detection (168 hypotheses)Frame boundary detection (2 hypotheses)CP-length detection (2 hypotheses)
BCH40ms BCH period timing detectioneNB # of tx antenna detectionMIB acquisition (Operation BW, SFN, etc…)
PCFICH PDCCH reception
SIB acquisition within PDSCH
Map Cell ID to cell-specific RS
Random access with PRACH
LTE/MIMO 표준기술 91
LTE Cell Search – cont’d*
PSS/SSS, BCH, (RACH)
1.4
3
LTE/MIMO 표준기술 92
PDSCH Processing
1) RS
2) PSS & SSS
and BCH
3) PCFICH
4) PHICH
5) PDCCH
6) PDSCH
LTE/MIMO 표준기술 93
Resource Block Allocations
Localized allocation
Distributed allocation
„Simple bitmap‟ whose size is equal to the number of RBs of the system
Merit: The most flexible signaling of resource block allocation
Demerit: High overhead
Not used in LTE
LTE has 3 resource allocation type
Type0: grouped bitmap
Type1: grouped bitmap, enable 1 RB allocation
Type2: VRB/PRB for localized & distributed
LTE/MIMO 표준기술 94
Resource Allocation Type0
Reduce the size of bitmap by grouping (RBG)
Bitmap points the group, not the individual RB
Cannot allocate 1RB in wide system BW
5MHz LTE example
LTE/MIMO 표준기술 95
Resource Allocation Type1
Reduce the size of bitmap by grouping (RBG)
Bitmap points the individual RB within a selected subset
The number of subsets is equal to RBG size in type0
Can allocate 1RB in wide system BW
3 fields
Subset ID: used to indicate the selected RBG subset among P subsets
Frequency shift bit: one bit to indicate whether to consider a shift of PRB within an RBG
Bitmap: each bit of the bitmap addresses a single PRB in the selected RBG subset
10MHz LTE example
LTE/MIMO 표준기술 96
Resource Allocation Type2
Does not rely on a bitmap
Basically „frequency-contiguous‟ allocation
Using VRB to PRB mapping, distributed allocation can be enabled
2 values
Start: a RIV (resource indication value) defines the index of the starting VRB
Length: length of virtually contiguously allocated resource blocks
5MHz LTE example
LTE/MIMO 표준기술 97
PRB and VRB (LVRB, DVRB) Physical resource blocks are numbered from 0 to in the frequency domain.
The relation between the physical resource block number in the frequency domain
and resource elements in a slot is given by
A virtual resource block is of the same size as a physical resource block.
Two types of virtual resource blocks are defined: LVRB and DVRB
Virtual resource blocks of localized type are mapped directly to PRBs such that virtual
resource block corresponds to physical resource block .
Virtual resource blocks are numbered from 0 to , where .
1DLRB N
PRBn
),( lk
RBsc
PRBN
kn
VRBn VRBPRB nn
1DLVRB N DL
RBDLVRB NN
LTE/MIMO 표준기술 98
DVRB
Virtual resource blocks of distributed type are mapped to PRBs as follows
Consecutive VRBs are not mapped to PRBs that are consecutive in the frequency domain
Even a single VRB pair is distributed in the frequency domain
The exact size of the frequency gap depends on the overall downlink cell BW
LTE/MIMO 표준기술 99
Resource Allocation Overhead
LTE/MIMO 표준기술 100
DL Frame Structure Type 1
LTE/MIMO 표준기술 101
DL constellation & frame summary
* Agilent
LTE Uplink Transmission
LTE/MIMO 표준기술 103
UL Slot Structure : Uplink bandwidth configuration,
expressed in units of
: Resource block size in the
frequency domain, expressed as a
number of subcarriers
: Number of SC-FDMA symbols in
an uplink slot
RBscN
RBscN
ULRBN
ULsymbN
ULsymbN SC-FDMA symbols
One uplink slot slotT
0l 1ULsymb Nl
RB
scU
LR
BN
N
sub
carr
iers
RB
scN
sub
carr
iers
RBsc
ULsymb NN
Resource block
resource elements
Resource element ),( lk
0k
1RBsc
ULRB NNk
LTE/MIMO 표준기술 104
Definitions Resource Grid
Defined as subcarriers in frequency domain and SC-FDMA symbols in time domain
The quantity depends on the UL transmission BW configured in the cell and shall fulfill
The set of allowed values for is given by TS 36.101, TS 36.104
Resource Block
Defined as “consecutive” subcarriers in frequency domain and “consecutive” SC-
FDMA symbols in time domain
Corresponding to one slot in the time domain and 180 kHz in the frequency domain
Resource Element
Uniquely defined by the index pair in a slot where and
are the indices in the frequency and time domain, respectively
1106 ULRB N
RB
sc
UL
RB NNUL
symbN
RBscN
lk,
UL
RBN
UL
RBN
UL
symbN
1,...,0 ULsymb Nl1,...,0 RB
scULRB NNk
LTE/MIMO 표준기술 105
UL Physical Channels & Signals
UL physical channels
Physical Uplink Shared Channel (PUSCH)
Physical Uplink Control Channel (PUCCH)
Physical Random Access Channel (PRACH)
UL physical signals
An uplink physical signal is used by the physical layer but does not
carry information originating from higher layers
Two types of reference signals
UL demodulation reference signal (DRS) for PUSCH, PUCCH
UL sounding reference signal (SRS) not associated with PUSCH,
PUCCH transmission
LTE/MIMO 표준기술 106
LTE WCDMA/HSPA WiMAX
PUSCH (E-DPDCH) UL Data Burst
PUCCH HS-DPCCH CQICH, ACKCH,
BW Request
Ranging
PRACH PRACH Initial Ranging
Demodulation RS (E-DPCCH) Pilot Signal
Sounding RS Sounding Signal
Equivalent Channel/Signal Mapping
Across Different Systems
LTE/MIMO 표준기술 107
UL Reference Signals
UL RS should preferably have the following properties:
Favorable auto- and cross-correlation properties
Limited power variation in freq-domain to allow for similar channel-estimation quality for all
frequencies
Limited power variation in time-domain (low cubic metric) for high PA efficiency
Sufficiently many RS sequences of the same length to avoid an unreasonable planning effort
Zadoff-Chu Sequence
Appeared in IEEE Trans. Inform. Theory in 1972
Poly-phase sequence
Constant amplitude zero auto correlation (CAZAC) sequence의 일종 Cyclic autocorrelations are zero for all non-zero lags, Non-zero cross-correlations
Constant power in both the frequency and the time domain
No restriction on code length N
- Sequence number p is relatively prime to N
- Sequence length: N
- Number of sequences: N-1
,
,)(
)1(2
2 2
npnN
j
pnN
j
p
e
eng
when N is even
when N is odd
LTE/MIMO 표준기술 108
DRS
DRS is made from Z-C sequence*, and the DRS sequence length is the same
with the number of subcarriers in an assigned RBs
DRS is defined with the following parameters
Sequence group (30 options): cell specific parameter
Sequence (2 options for sequence lengths of 6PRBs or longer): cell specific
parameter
Cyclic shift (12 options): both terminal and cell specific components
Sequence length: given by the UL allocation
Typically,
Cyclic shifts are used to multiplex RSs from different UEs within a cell.
Different sequence groups are used in neighboring cells.
LTE/MIMO 표준기술 109
DRS Location within a Subframe
DRS for PUSCH
Normal CP 적용 시 PUSCH RS는 한 슬롯 당 중앙의 SC-FDMA 심볼에 위치Extended CP 적용 시 PUSCH RS는 한 슬롯 당 3번째 SC-FDMA 심볼에 위치
DRS for PUCCH
Format 1x
Format 2x
LTE/MIMO 표준기술 110
SRS
기지국이 각 단말의 상향링크 채널 정보를 추정할 수 있도록 단말이 전송하는 RS
Reference for channel quality information
CQ measurement for frequency/time aware scheduling
CQ measurement for link adaptation
CQ measurement for power control
CQ measurement for MIMO
Timing measurement
Reference signal sequence is defined by a cyclic shift of a base sequence (ZC)
SRS 전송주기/대역폭은 각 단말마다 고유하게 할당
From as often as once in every 2ms to as infrequently as once in every 160ms (320ms)
At least 4 RBs
SRS는 서브프레임의 마지막 SC-FDMA 심볼로 전송
SRS multiplexing by
Time, Frequency, Cyclic shifts, and transmission comb (2 combs distributed SC-FDMA)
To avoid the collision b/w SRS and PUSCH transmission from other UEs, SRS
transmissions should not extend into the frequency band reserved for PUCCH.
nrnr vu)(
,SRS
RSsc,
)(, 0),()( Mnnrenr vu
njvu
LTE/MIMO 표준기술 111
SRS – cont’d
Non-frequency-hopping (wideband) SRS and frequency-hopping SRS
Multiplexing of SRS transmissions from different UEs
LTE/MIMO 표준기술 112
Uplink L1/L2 Control Signaling
Uplink L1/L2 control signaling consists of:
HARQ acknowledgements for received DL-SCH transport blocks
UE reports downlink channel conditions including CQI, PMI, and RI
Scheduling requests
Channel feedback report
CQI (Channel Quality Indicator)
RI (Rank Indicator)
PMI (Precoding Matrix Indicator)
LTE/MIMO 표준기술 113
CQI
CQI Table
MCS where transport block could be received with transport block error rate 0.1
*Note that there are many more
possibilities for MCS and TBS size
values than 15 indicated by CQI
feedback.
Reported CQI is calculated assuming the particular RI value
CQI is a function of frequency, time, and space
CQI index Modulation Coding rate x 1024 Bits per RE
0 Out of range
1 QPSK 78 0.1523
2 QPSK 120 0.2344
3 QPSK 193 0.3770
4 QPSK 308 0.6016
5 QPSK 449 0.8770
6 QPSK 602 1.1758
7 16QAM 378 1.4766
8 16QAM 490 1.9141
9 16QAM 616 2.4063
10 64QAM 466 2.7305
11 64QAM 567 3.3223
12 64QAM 666 3.9023
13 64QAM 772 4.5234
14 64QAM 873 5.1151
15 64QAM 948 5.5547
LTE/MIMO 표준기술 114
UL L1/L2 Control Signaling Transmission
Two different methods for transmission of UL L1/L2 control signaling
No simultaneous transmission of UL-SCH
UE doesn’t have a valid scheduling grant, that is, no resources have been
assigned for UL-SCH in the current subframe
PUCCH is used for transmission of UL L1/L2 control signaling
Simultaneous transmission of UL-SCH
UE has a valid scheduling grant, that is, resources have been assigned for UL-
SCH in the current subframe
UL L1/L2 control signaling is time multiplexed with the coded UL-SCH onto
PUSCH prior to SC-FDMA modulation
Only HARQ acknowledgement and channel-status reports are transmitted
No need to request a SR. Instead, in-band buffer status reports are sent in
MAC headers
The basis for channel-status reports on PUSCH is aperiodic reports
If a periodic report is configured to be transmitted on PUCCH in a frame when
US is scheduled to transmit PUSCH, then the periodic report is rerouted to
PUSCH resources
LTE/MIMO 표준기술 115
UL L1/L2 control signaling on PUCCH
The reasons for locating PUCCH resources at the edges of the spectrum
To maximize frequency diversity
To retain single-carrier property
Multiple UEs can share the same PUCCH resource block
Format 1: length-12 orthogonal phase rotation sequence + length-4 orthogonal cover
Format 2: length-12 orthogonal phase rotation sequence
PUCCH is never transmitted simultaneously with PUSCH from the same UE
2 consecutive PUCCH slots inTime-Frequency Hopping at the slotboundary
LTE/MIMO 표준기술 116
PUCCH Formats
PUCCH
format
Modulation
scheme
Number of bits
per subframeUsage
Multiplexing
capacity
(UE/RB)
1 N/A N/A SR 36, 18*, 12
1a BPSK 1 ACK/NACK 36, 18*, 12
1b QPSK 2 ACK/NACK 36, 18*, 12
2 QPSK 20 CQI 12, 6*, 4
2a QPSK+BPSK 21 CQI + ACK/NACK 12, 6*, 4
2b QPSK+QPSK 22 CQI + ACK/NACK 12, 6*, 4
* Typical value with 6 different rotations (choosing every second cyclic shift)
PUCCH Format 2/2a/2b is located at the outermost RBs of system BW
ACK/NACK for persistently scheduled PDSCH and SRI are located next
ACK/NACK for dynamically scheduled PDSCH are located innermost RBs
LTE/MIMO 표준기술 117
PUCCH Resource Mapping
Format 1
4 symbols are modulated by BPSK/QPSK
BPSK/QPSK symbol is multiplied by a length-4 orthogonal cover sequence (a length-3 orthogonal cover when there is SRS), and then it modulates the rotated length-12 sequence.
Reference signals also employ one orthogonal cover sequence
PUCCH capacity: up to 3 x 12 = 36 different UEs per each cell-specific sequence(assuming all 12 rotations being available Practically, only 6 rotations.)
Format 2
5 symbols are modulated by QPSK after being multiplied by a phase rotated length-12 cell specific sequence.
Resource consumption of one channel-status report is 3x of HARQ acknowledgement
LTE/MIMO 표준기술 118
PUCCH Format1 Processing
LTE/MIMO 표준기술 119
PUCCH Format2 Processing
LTE/MIMO 표준기술 120
PUSCH Processing
LTE/MIMO 표준기술 121
PUSCH Frequency Hopping
PUSCH transmission
Localized transmission w/o frequency hopping
Frequency Selective Scheduling Gain
Localized transmission with “frequency hopping”
Frequency Diversity Gain, Inter-cell Interference Randomization
Two types of PUSCH frequency hopping
Subband-based hopping according to cell-specific hopping patterns
Hopping based on explicit hopping information in the scheduling grant
LTE/MIMO 표준기술 122
Hopping based on cell-specific patterns
Subbands are defined
In 10 MHz BW case, the overall UL BW corresponds to 50 RBs and there are a total of 4 subbands, each consisting
of 11 RBs. The remaining 6 RBs are used for PUCCH transmission.
The resource defined by a scheduling grant (VRBs) is not the actual set of RBs for transmission.
The resource to use for transmission (PRBs) is the resource provided in the scheduling grant “shifted” a
number of subbands according to a cell-specific hopping pattern.
LTE/MIMO 표준기술 123
More on hopping w/ cell-specific patterns
Example for predefined hopping for PUSCH with 20 RBs and M=4
(subband hopping + mirroring)
LTE/MIMO 표준기술 124
Hopping based on explicit information
Explicit hopping information provided in the scheduling grant is about the “offset” of the
resource in the second slot, relative to the resource in the first slot
Selection b/w hopping based on cell-specific hopping patterns or hopping based on explicit
information can be done dynamically.
Cell BW less than 50 RBs
1 bit in scheduling grant indicating to specify which scheme is to be used
When hopping based on explicit information is selected, the offset is always half of BW
Cell BS equal or larger than 50 RBs
2 bits in scheduling grant
One of the combinations indicate that hopping should be based on cell-specific hopping patterns
Three remaining combinations indicate hopping of 1/2, +1/4, and -1/4 of BW
LTE/MIMO 표준기술 125
UL SC-FDMA Signal Generation
This section applies to all uplink physical signals and physical channels
except the physical random access channel
SC-FDMA parameters
where N = 2048
Check with numbers in Table 5.2.3-1.
{(160+2048) x Ts} + 6 x {(144+2048) x Ts} = 0.5 ms
6 x {(512+2048) x Ts} = 0.5 ms
s,CP0 TNNt l
LTE/MIMO 표준기술 126
PRACH PRACH는 RA 과정에서 단말이 기지국으로 전송하는 preamble이다
6RB를 차지하며 부반송파 간격은 1.25kHz (format #4는 7.5kHz)
64 preamble sequences for each cell 64 random access opportunities per PRACH resource
Sequence부분은 길이 839의 Z-C sequence로 구성 (format #4는 길이 139)
Phase modulation: Due to the ideal auto-correlation property, there is no intra-cell interference from multiple
random access attempt using preambles derived from the same Z-C root sequence.
Five types of preamble formats to accommodate a wide range of scenarios
Higher layers control the preamble format
일반적 환경 (~15km)
넓은 반경의 셀 환경과 같이 시간 지연이 긴 경우 (~100km)
SINR이 낮은 상황을 고려하여 sequence repetition (~30km)
SINR이 낮은 상황을 고려하여 sequence repetition (~100km)
TDD 모드용
LTE/MIMO 표준기술 127
Different Preamble Formats
LTE/MIMO 표준기술 128
PRACH Location
One PRACH resource of 6 RBs per subframe (for FDD)
Multiple UEs can access same PRACH resource by using different preambles
PRACH may or may not present in every subframe and every frame
PRACH-Configuration-Index parameter indicates frame number and subframe numbers
where the PRACH resource is available.
Starting frequency is specified by the network ( )
No frequency hopping for PRACH
LTE/MIMO 표준기술 129
LTE Cell Search & Random AccessPrimary SSSymbol timing acquisitionFrequency synchronizationCell ID detection within a cell group ID (3 hypotheses)Half-frame boundary detection
Secondary SSCell group ID detection (168 hypotheses)Frame boundary detection (2 hypotheses)CP-length detection (2 hypotheses)
BCH40ms BCH period timing detectioneNB # of tx antenna detectionMIB acquisition (Operation BW, SFN, etc…)
PCFICH PDCCH reception
SIB acquisition within PDSCH
Map Cell ID to cell-specific RS
Random access with PRACH
LTE/MIMO 표준기술 130
UL Frame Structure Type 1*
1 RB
LTE/MIMO 표준기술 131
UL 16QAM SC-FDMA
* Agilent
Summary
LTE/MIMO 표준기술 133
E-UTRA UE Capabilities*
LTE/MIMO 표준기술 134
Final Message** Signals Ahead