02 channel config gc
TRANSCRIPT
1 © Nokia Siemens Networks RA41212EN20GLA1
LTE Radio Parameters RL20Channel Configuration
3 © Nokia Siemens Networks RA41212EN20GLA1
1. LTE Functionalities and Overview2. Channel Configuration3. General parameter DB structure and System Information
Broadcast4. Random Access5. Radio Admission Control (RAC)6. Radio Bearer Control & DRX /DTX Management7. LTE Mobility Management8. UL/DL Scheduler9. MIMO Mode Control (MIMO-MC)10.Power Control
Presentation / Author / Date
Contents
4 © Nokia Siemens Networks RA41212EN20GLA1
Module Contents
• Overview• DL Channels and Signals• UL Channels and Signals
5 © Nokia Siemens Networks RA41212EN20GLA1
Overview - ChannelsUpper Layers
RLC
MAC
PHY
Logical channels
Transport channels
BC
CH
CC
CH
PC
CH
MTC
H
MC
CH
BC
H
PC
H
DL-
SC
H
RA
CH
UL-S
CH
PB
CH
PD
SC
H
PH
ICH
PD
CC
H
PC
FICH
PM
CH
PU
CC
H
PR
AC
H
PU
SC
H
MC
H
CC
CH
DC
CH
DTC
HULDL
Air interface
DC
CH
DTC
H
Synch
RS
SR
S
DR
S
6 © Nokia Siemens Networks RA41212EN20GLA1
DL Physical Channels Allocation• RS/DTX: Reference Signal
– Occupies at least 8 RE per RB(84 RE for normal CP ) throughout the whole system bandwidth
• PSS/SSS: Primary/Secondary Synchronisation Signal
– Occupies the central 72 subcarriers across 2 symbols
• PBCH: Physical Broadcast Channel– Occupies the central 72 subcarriers across 4
symbols• PCFICH: Physical Control Format Indication
Channel– Occupies up to 16 RE per TTI
• PHICH: Physical HARQ Indication Channel– Occupies 12 RE, and Tx during 1st symbol of
each TTI or alternativ during symbols 1 to 3 of each TTI
• PDCCH: Physical Downlink Control Channel– Occupies the REs not used by PCFICH and
PHICH and Reference Signals within the first 1, 2 or 3 symbols of each TTI
• PDSCH: Physical Downlink Shared Channel– Is allocated the RE not used by signals or
other physical channels
RB
7 © Nokia Siemens Networks RA41212EN20GLA1
UL Physical Channels and Reference Signals• PUSCH: Physical Uplink Shared Channel
– Intended for user data (carries traffic for multiple UEs) and control data
– If control data is to be sent when traffic data is being transmitted, UE multiplexes both streams together
• PUCCH: Physical Uplink Control Channel– Carries H-ARQ Ack/Nack indications, uplink scheduling
request, CQIs and MIMO feedback– Only control information is sent. The UE uses Resources
Element at the edges of the channel
• PRACH: Physical Random Access Channel– For Random Access attempts. PDCCH indicates the
resource elements for PRACH use– System Information contains a list of allowed preambles
(64 per cell) and the required length of the preamble.
• DRS: Demodulation Reference Signal– For uplink demodulation and channel estimate
• SRS: Sounding Reference Signal (not included in RL20)– For uplink channel aware scheduling
RACH
CCCH DCCH DTCH
UL-SCH
PRACH PUSCH PUCCH
Logical
Transport
PHYS.
RLC
MAC
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eNode B
PDCCH
PDSCH
CQI, PMI, RI,
ACK/NACK
SR
RNTIDL schedulingUL GrantUL Power Controln x per cell
DL control configuration
1x per cell
PCFICH
PHICH
HARQ Info
PUSCHPUCCH
CQI, PMI, RI,
ACK/NACK
Overview – Control Information
CQI: Channel Quality Indicator PMI: Precoding Matrix IndicatorRI: Rank IndicatorSR: Scheduling Request
ACK: Acknowledgement NACK: Negative AcknowledgementRNTI: Radio Network Temporary IndicatorHARQ: Hybrid Automatic Retransmission reQuest
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Generic - Bandwidth• Channel bandwidth: Bandwidths ranging from 1.4 MHz to 20 MHz• Data subcarriers: They vary with the bandwidth
– 72 for 1.4MHz to 1200 for 20MHz
ulChBw / dlChBwDefines the UL and DL bandwidth and the number of available Physical Resource BlocksLNCEL; 5MHz(2), 10MHz(3), 15MHz(4), 20MHz(5); 10 MHz(3)
FDD CarrierBandwidth
[MHz]
Number ofPRB
1.4 6
3 15
5 25
10 50
15 75
20 100
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Generic - Carrier Frequency and Bandwidth (FDD)
100 kHz
... ...
FUL = FUL_low + 0.1(NUL – NOffs-UL)
FDL = FDL_low + 0.1(NDL – NOffs-DL)
EARFCN NUL : earfcnULNDL : earfcnDL
BandwidthUL: ulChBwDL: dlChBw
*Noffs-DL & Noffs-UL specified by TS 36.101 for each band
earfcnUL/ earfcnDLAbsolute Radio Frequency Channel Number
LNCEL; 0...65535; 1; -
Note: Supported bands RL20: Band 1, 3, 4, 5, 6, 7, 9, 10,18, 19, 20, 24
earfcnUL = earfcnDL + 18000
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EUTRA Channel Numbers
Example (band 12) FUL = 708 MHz = 698 MHz + 0.1 (23100 – 23000) MHz FDL = 738 MHz = 728 MHz + 0.1 (5100 – 5000) MHz
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Generic - Physical Layer Cell Id• Physical Layer Cell Identity is used to differentiate neighbor cells • It consists of the two parts; Physical layer Cell Identity Group and Physical layer Identity • Physical Layer Cell Identity = 3 x Physical layer Cell Identity Group + Physical layer Identity• Decoded during synchronisation using primary and secondary sync signal
Strongest Signal
Primary Synchronization Signal
Secondary Synchronisation Signal
L1 id, slot (0/10)
Physical Layer Cell ID, Frame
Alignment
Cell ID Group 0(3 L1 id’s)
Group 167
Cell ID Group i(3 L1 id’s) 168 Cell ID
groups
Phy L Cell ID
• As a result of cell search the UE should acquire:– PHY cell ID– 10ms and 5ms timing– CP length– Duplex mode (TDD/FDD)
phyCellId:Physical Cell IdLNCEL; 0..503; 1; - (Range; Step; Default)
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PCI PlanningRecommendations
In priority order, number 1 most important (all four should be fulfilled, ideally)
1. Avoid assigning the same PCI to neighbour cells
2. Avoid assigning the same mod3 (PCI) to ‘neighbour’ cells
3. Avoid assigning the same mod6(PCI) to ‘neighbour’ cells
4. Avoid assigning the same mod30 (PCI) to ‘neighbour’ cells
Id = 5
Id = 4
Id = 3Id = 11
Id = 10
Id = 9
Id = 8
Id = 7
Id = 6Id = 2
Id = 1
Id = 0
Example 1 PCI Identity Plan
Example 2 PCI Identity PlanPCI = Physical Cell Identity
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Generic - Time Structure (Frame Type 1)
19
144 Ts = 4.69 µs160 Ts
CP Symbol CP Symbol CP Symbol CP Symbol CP Symbol CP Symbol CP Symbol
CP Symbol
512 Ts = 16.7 µs
CP Symbol CP Symbol CP Symbol CP Symbol CP Symbol
CP Symbol
1024 Ts = 33.3 µs
CP Symbol CP Symbol
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 0
Radio frame = 10 ms
subframe = 1 ms
Cyclic Prefixx2047-Ncp, … x2047
OFDM Symbol (Time Domain Samples)x0, x1, …, x2047
Symbol Tsym = 2048 Ts = 66.67 µsTcp = Ncp Ts
f = 15 kHz, UL/DL - Extended Prefix
f = 7.5 kHz, UL/DL - Extended Prefix
f = 15 kHz, UL/DL - Normal Prefix
Slot = 15360 Ts = 500µs
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Generic – Time Structure and CP length
Short cyclic prefix:
Long cyclic prefix:
Copy= Cyclic prefix
= Data
5.21 s
16.67 s
• Subframe length is 1 ms for all bandwidths• Slot length is 0.5 ms
– 1 Subframe= 2 slots• Slot carries 7 symbols with normal cyclic prefix or 6 symbols with extended prefix
– CP length depends on the symbol position within the slot:▪ Normal CP: symbol 0 in each slot has CP= 160 x Ts (5.21μs and remaining symbols CP= 144 x Ts ( 4.7μs)▪ Extended CP: CP length for all symbols in the slot is 512 x Ts ( 16.67µs)
Ts: ‘sampling time’ of the overall channel. Basic Time Unit.
Ts =1 sec
Subcarrier spacing X max FFT size
=1 sec
15kHz X 2048
= 32.5nsec
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Module Contents
• Overview• DL Channels and Signals• UL Channels and Signals
17 © Nokia Siemens Networks RA41212EN20GLA1
DL - Channels and Signals OverviewUpper Layers
RLC
MAC
BC
CH
CC
CH
PCC
H
MTC
H
MC
CH
BC
H
PCH
DL-
SCH
PBC
H
PDSC
H
PHIC
H
PDC
CH
PCFIC
H
PMC
HM
CH
Air interface
DC
CH
DTC
H
Synch
RS
PHYH
I
CFI
DCI
18 © Nokia Siemens Networks RA41212EN20GLA1
180 kHz
0.5 ms
Secondary Synchronisation Signal (SSS)
Primary Synchronisation Signal (PSS)
DTX
Slot id: 0 1 2 . . ..10.. ..19 0 1
Synch Signals – Time and Frequency
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Reference Signals
• Common Reference Signals (CRS):– Cell-specific– FDM/TDMuxed– Defined per antenna port– F-density 6 sub-carriers (or 3 sub-carriers if staggered structure is considered)– BW invariant mapping to REs– Used for:
▪ Channel estimation (in case of CRS-based transmission with known/signaled precoding)
▪ Mobility measurements▪ Auxiliary UE functions like:
• Time tracking• Frequency tracking• Cell ID verification• CP length verification
*Staggered structure with multiple antenna ports (see next slide)
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Incremental Time-Frequency Structure of Cell-specific Reference Signal
0l0R
0R
0R
0R
6l 0l0R
0R
0R
0R
6l
One
ant
enna
por
tTw
o an
tenn
a po
rts
Resource element (k,l)
Not used for transmission on this antenna port
Reference symbols on this antenna port
0l0R
0R
0R
0R
6l 0l0R
0R
0R
0R
6l 0l
1R
1R
1R
1R
6l 0l
1R
1R
1R
1R
6l
0l0R
0R
0R
0R
6l 0l0R
0R
0R
0R
6l 0l
1R
1R
1R
1R
6l 0l
1R
1R
1R
1R
6l
Four
ant
enna
por
ts
0l 6l 0l
2R
6l 0l 6l 0l 6l2R
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
Resource Element (RE) k, l
Not used for transmission on this antenna port (DTX)
Reference symbols (RS) on this antenna port
l=0 ……...... 6, 0 ……….. 6l=0 ……...... 6, 0 ……….. 6
l=0 ……...... 6, 0 ……….. 6
Antenna port 0 Antenna port 1 Antenna port 2 Antenna port 3
Four
ant
enna
por
ts
T
wo
ante
nna
port
s
O
ne a
nten
na p
ort
21 © Nokia Siemens Networks RA41212EN20GLA1
Physical Broadcast Channel
• PBCH carriers essential system information like:– DL BW configuration– PHICH configuration– System Frame Number (8 MSB bits)
• PBCH enables blind detection of:– DL antenna configuration {1TX, 2TX, 4TX} via CRC masking*– 40 ms timing (2 LSB bits of SFN) via 40ms scrambling
* for decoding the CRC (Cyclic Redundancy Check) each MIB is masked with a codeword representing the number of transmit antenna ports.
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Physical Layer Downlink DL-Physical Data & Control Channels
PBCPBCHH
PBCH
Synchronization signals
Reserved for reference singals
Remark: PBCH does not use blocks reserved for reference signals
Code and rate-matching (repetition) to number of bits available on PBCH in 40 ms
One MIB (information bits + spare bits + CRC)
40 ms transmission time interval of PBCH
One radio frame
6 R
Bs
Use
d ba
ndw
idth
1 R
B
One subframe (2 slots) 1 ms
Segmentation into four equal sized individually self-decodable units
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Physical Layer Downlink DL-Physical Data & Control Channels
PCFICHPCFICH• General
– Physical Control Format Indicator Channel (PCFICH) carries the CFI (Control Format Indicator)▪ (Indicates the number of OFDM symbols used for transmission of control channel information in each subframe)
– Carriers dedicated to MBSFN have no physical control channel and therefore no PCFICH– 4 code words defined
▪ 3 CFIs used and one reserved for future use (see table below)
CFI CFI codeword <b0, b1, b2,……b31>1 <0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1>
2 <1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0>
3 <1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,>
4 (reserved) <0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,>
• Transmitted – In the first OFDM symbol in a subframe– The 32 bits of the CFI are mapped to 16 REs using QPSK modulation– PCFICH is transmitted on the same antenna ports as the PBCH (1Tx, SFBC, SFBC-FSTD)– Cell specific offset is added – Cell specific scrambling
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PCFICH Mapping to Resource Elements
• The mapping is done in terms of quadruplets of modulation symbols for each antenna port
• A quadruplet is defined as d(4i), d(4i+1), d(4i+2), d(4i+3)• Reference symbols REs are always reserved for at least 2Tx antennas• The four quadruplets shall be mapped to four resource element groups (REG)
(aka mini-CCE) in the first OFDM symbol– Example: 72 subcarriers case (1.4 MHz):
DLRB
cellID
RBsc 2mod2 NNNk
Starting position depends on cell id
Distance between mini-CCEs
Ant 0
Ant 1
frequency
d0 d1 d2 d3
-d1 d0 -d3 d2* * * *
22 RBsc
DLRB NN
Ant 0
Ant 1
frequency
d0 d1
d2 d3
-d1 d0
-d3 d2
* ** *
Ant 2
Ant 3
frequency
Resource
element group
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PHICH• For HARQ ACK/NACK signaling the PHICH is deployed. • A PHICH is defined by its PHICH group number and an
orthogonal sequence number within the group.• PHICH modulation is BPSK. Applying I/Q separation
and an SF=4 yields 8 orthogonal sequences for normal CP. SF 2 is in use in case of extended CP, hence there are 4 orthogonal sequences. I,e. in total there may be 8 .. 224 PHICHs in one subframe.
• Example: BW=15 subcarriers normal CP, Ng=1/6, 1 PHICH group. 12 symbols are to be transmitted.
• NRBDL : DL BW / RBs
• Ng = 1/6, 1/2, *1,* 2. setting: phichRes
prefix cyclic extendedfor 82
prefix cyclic normalfor 8DLRBg
DLRBggroup
PHICHNN
NNN
+j -j -j +j7
+j +j -j -j6
+j -j +j -j5
+j +j +j +j 4
+j -j+1 -1 -1 +13
+j +j+1 +1 -1 -12+1 -1+1 -1 +1 -11
+1 +1+1 +1 +1 +1 0
Extended CPNormal CP
Orthogonal sequenceSequence Index
+j -j -j +j7
+j +j -j -j6
+j -j +j -j5
+j +j +j +j 4
+j -j+1 -1 -1 +13
+j +j+1 +1 -1 -12+1 -1+1 -1 +1 -11
+1 +1+1 +1 +1 +1 0
Extended CPNormal CP
Orthogonal sequenceSequence Index
Number of RBs
phichRes#PHICH groupsLNCEL; 1/6; ½; 1; 2; 1/6
phichRes 1/6 1/2 1 2
#PHICH groups 3 7 13 25
# scheduled UE 24 56 104 200
e.g. 20 MHz*Necessary with semi-persistent scheduling
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PHICH Association and Resource Indication
• PHICH duration:– 1 or 3 OFDM symbols in normal subframes (indicated via PBCH)
• PHICH linked to UL PRB• Scattered grouping - spreads out the PHICH of adjacent PRBs to different
PHICH groups• When DM-RS Cyclic Shift index is configured in UL grant, use DM-RS CS
index as modifier to adjust PHICH allocation– Avoid PHICH collision e.g. in case of UL MU-MIMO– Balance power among PHICH groups
• PHICH indexing: – Both index of the group and within the group depend on first UL PRB index and
UL DM-RS Cyclic Shift
PhichDurPHICH on symb. 1 / 1- 3
LNCEL; Normal (0), Extended (1); 1; Normal(0)
DM-RS CS: Demodulation Reference Signal Cyclic Shift
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PDCCH Overview
• The PDCCH carries the UL & DL scheduling assignments• A PDCCH is transmitted on an aggregation of one 1, 2, 4 or 8 control channel
elements (CCE). A CCE consists of 36 REs• The aggregations of CCEs have a tree structure, where an aggregation consisting
of n CCEs starts on position (i mod n), where i is the CCE number• Further restrictions on the aggregations are defined with a Hashing function
pdcchAggDefUEPDCCH LA UE default aggregation; used, when enableAmcPdcch disabled or no valid CQI existsLNCEL; 1(0), 2 (1), 4 (2), 8 (3); -; 4 (2)
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DL - L1/L2 control info: PDCCH Resources• The MaximumNumberOfOFDMSymbolsForPDCCH parameter defines how many
OFDM symbols can be used. • eNB selects the actual value for each TTI, which is signalled to UE in PCFICH. • Range: 1, 2, 3 (BW > 1.4 MHz); • Range: 2, 3, 4 (BW = 1.4 MHz)• setting: maxNrSymPdcch• Example shows dynamic case for
MaximumNumberOfOFDMSymbolsForPDCCH=3 (yellow)
maxNrSymPdcchLNCEL; 1..3; 1; 3
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Downlink Control Information (DCI)• A DCI transports control information for one MAC ID, which is implicitly signaled in
the CRC.– Format 0
▪ Used for defining the transmission of PUSCH assignments– Format 1
▪ Used for defining the transmission of PDSCH assignments for single codeword (SCW) operation– Format 1A
▪ Compact form for the transmission of PDSCH assignments for SCW operation*. Has same size as format 0– Format 1B
▪ Compact form like 1A but supports closed-loop rank 1 precoding – Format 1C
▪ Signaling for PCH, RACH & BCCH on DL SCH (aka dynamic BCCH) – Format 1D
▪ Like DCI 1A but supports power offsets for DL MU-MIMO and TPMI– Format 2
▪ Used for defining the transmission of DL-SCH assignments for Closed-Loop MIMO operation– Format 2A
▪ Used for defining the transmission of DL-SCH assignments for Open-Loop MIMO operation– Format 3
▪ Used for TPC commands for PUCCH and PUSCH with 2-bit power adjustments. Has same size as format 0– Format 3A
▪ Used for TPC commands for PUCCH and PUSCH with 1-bit power adjustments. Has same size as format 0
DCI Format 1 (all):PDSCH resource assignment
when no Spatial Multiplexing used
DCI formats 2 & 2A:provide PDSCH assignments
for closed loop or open loop spatial multiplexing
* allocating a dedicated preamble signature to a UE for contention-free random access
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Physical Layer Downlink Summary DL-Physical Data & Control Channel
SSS
PSS
PBCH
PCFICH
PHICH
PDCCH
Reference signals
PDSCH UE1
PDSCH UE2
Freq
uenc
y
Time
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Exercise: PDCCH ResourcesTask:• Consider cell configuration: BW=50 PRB, 2 antenna ports, normal CP • MaximumNumberOfOFDMSymbolsForPDCCH=2• Ng = 1/6
Calculate the number of available PDCCHs.Assume for frequency of occurancies of different aggregation levels (AL)AL4 is 2 times the frequency of AL8AL2 is 2 times the frequency of AL4AL1 is 1/2 times the frequency of AL2
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Solution: PDCCH ResourcesTask:• Consider cell configuration: BW=50 PRB, 2 antenna ports, normal CP • MaximumNumberOfOFDMSymbolsForPDCCH=2• Ng = 1/6
Calculate the max number of PDCCHs.
Solution:- 1st symbol yields 2 REGs per PRB x 50 PRB = 100 REGs (because of the reference signals)- 2nd yields 3 x 50 = 150 REGs. Total: 250 REGs. (no reference signals )- 4 REGs for PCFICH, 2x3=6 for PHICH 240 REGs remain for PDCCH- 240 div 9 = 26 CCEs are available- For 1 distribution 1xAL8 + 2xAL4 + 4xAL2+2xAL1- Aggregation level 8 1x = 8 CCEs- Aggregation level 4 2x = 8 CCEs- Aggregation level 2 4x = 8 CCEs- Aggregation level 1 2x = 2 CCEs26 CCEs are consumed for 9 PDCCH.
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Module Contents
• Overview• DL Channels and Signals• UL Channels and Signals
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UL Channel Mapping
Upper Layers
RLC
MAC
PHYR
AC
H
CC
CH
DC
CH
DTC
H
Air interface
PR
AC
H
PU
SC
HU
L-S
CH
PU
CC
H
UC
I
DR
S
SR
S
35 © Nokia Siemens Networks RA41212EN20GLA1
UE Channel state information (CSI) feedback types in LTE
• The purpose of CSI feedback is to provide the eNodeB information about DL channel state to help in the scheduling decision.
• Compared to the WCDMA/HSPA, the main new feature in the channel feedback is the frequency selectivity of the report
• CSI is measured by the UE and signaled to the eNodeB using PUCCH or PUSCH
• Channel state information in LTE can be divided into three categories:
– CQI - Channel Quality Indicator– RI - Rank Indicator– PMI - Precoding Matrix Indicator• In general the CSI reported by the UE is just a
recommendation – The eNodeB does not need to follow it• The corresponding procedure for providing UL
channel state information is called Channel Sounding; it is done using the Sounding Reference Symbols, SRS (not considered in this presentation)
(1) eNodeB transmission
(3) UE feedback
(2) UE CSI measurement
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Channel Quality Indicator (CQI)
• The most important part of channel feedback is the CQI
• The CQI is defined as a table containing 16 entries with modulation and coding schemes (MCSs)
• The UE shall report back the highest CQI index corresponding to the MCS for which the transport block BLER shall not exceed 10%
CQI index modulation
coding rate x 1024
efficiency
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 5.1152
15 64QAM 948 5.5547
UE reports highest MCS that it can decode with a TB Error rate < 10% taking into account UE’s receiver
characteristic
* Efficiency is defined as number of bits per resource elements
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Rank Indicator (RI)
• Rank Indicator is only relevant when the UE is operating in MIMO modes with spatial multiplexing
– For single antenna operation or TX diversity it is not used
• RI is the UEs recommendation for the number of layers to be used in spatial multiplexing
• The RI can have values {1 or 2} with 2-by-2 antenna configuration and {1, 2, 3, or 4} with 4-by-by antenna configuration
• The RI is always associated to one or more CQI reports
riEnableDetermines whether RI reporting is enabled (true) or not (false) LNCEL; true (1); false(0); false (0)
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Precoding Matrix Indicator (PMI)
• PMI provides information about the preferred Precoding Matrix• Just like RI, also PMI is relevant to MIMO operation only
– MIMO operation with PMI feedback is called Closed Loop MIMO
Example: codebook for 2 TX antennas
* PMI not used in RL10, but used in RL20, to support CL Spatial Mux MIMO
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Periodic and Aperiodic Reporting• The channel feedback reporting in LTE is divided into two main
categories: Periodic and Aperiodic
Periodic reporting
• The baseline mode for CQI/PMI/RI transmission is periodic reporting on PUCCH
• If the UE is scheduled to send UL data in the subframe where it should transmit periodic CQI/PMI/RI, the periodic report is moved to PUSCH and multiplexed with data
• The eNodeB configures the periodicity parameters
• The size of a single report is limited up to about 11 bits depending on the reporting mode
• Limited amount of frequency information
Aperiodic Reporting• Aperiodic reports are explicitly triggered by the eNodeB using a specific bit in the PDCCH UL grant
• Aperiodic report can be either piggybacked with data or sent alone on PUSCH
• Possibility for large and detailed reports (up to more than 60 bits)
The two modes can also be used to complement each other:- The UE can be e.g. configured to send Aperiodic reports only when it is scheduled, while periodic reports can provide coarse channel information on a regular basis
CQIAperEnableenabling / disabling aperiodic CQI /RI/PMI reporting on PUSCH. LNCEL; false/true; true
cqiPerNpCQI periodicity LNCEL; 2; 5; 10; 20; 20 ms
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Categorization of CQI/PMI/rank reporting options
LTE CQI reporting
family tree
Periodic
Frequency selective
Aperiodic
Single CQI Full FeedbackBest-M Average
No PMIMode 2-024 bits
No PMIMode 3-030 bits
Multi PMI1-2
60 bits
Single PMIMode 3-164 bits
Multi-PMIMode 2-238 bits
Wideband
No PMIMode 2-0
6 bits
Single PMIMode 2-111 bits
No PMIMode 1-0
4 bits
Single PMIMode 1-111 bits
Single or Multi-PMI = closed loop MIMO with PMI feedbackNo PMI = Single antenna, TxDiv or OL MIMO
The maximum number of feedback bits for each option Assuming 20 MHz BW and 4*4 CL MIMO is listed excluding RI - With Periodic reporting RI is sent in separate subframes with potentially larger periodicity- In Aperiodic reporting The RI is separately coded with each CQI/PMI report
*See TS 36.213
cqiAperModeAperiodic CQI feedback modeLNCEL; FBT1(0) – familly modes 2-x, FBT2(1)- familiy modes 3-x (x defined by MIMO algorithm internal in eNodeB); FBT2 (1)
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CQI Aperiodic Reporting on PUSCH (1/2)• Compared to the WCDMA/HSPA, the main new feature in the channel
feedback is the frequency selectivity of the report– This is an enabler for the Frequency Domain packet Scheduling (FDPS)
• Since providing a full 4-bit CQI for all the PRBs would mean excessive UL signaling overhead, some feedback compression schemes are used
• In order to reduce feedback, the CQI is reported per subband basis– The size of the subbands varies depending on the reporting mode and system
bandwidth • The main compression methods are:
– Wideband feedback– Best-M average also called UE selected subband feedback– Full Feedback also called Higher Layer Configured subband feedback
• Additionally, Delta compression can be used – E.g. in MIMO case the CQI for the 2nd Code Word can be signaled as a 3-bit
delta relative to the CQI of the CQI of the 1st CW
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CQI Aperiodic Reporting on PUSCH (2/2)• Wideband feedback
– Only a single CQI value is fed back for the whole system band– Cannot be utilized in FDPS
• Best-M average also called UE selected sub-band feedback– For the M best sub-band an average CQI value is reported
• Full Feedback also called Higher Layer Configured sub-band feedback– A separate CQI is reported for each sub-band using Delta compression
An example of Best-M Average reporting with 3 MHz BW (15 RBs means that the sub-band size is 2 RBs and the best 3 sub-bands are reported)
M = 3 best Subbands are selected and an average CQI value is reported
Channel SINR
Subband index 1 2 3 4 5 6 7 8PRB index 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
BW / RB
Sub-band size
(RBs)
# best Sub-
bandsM
6-7 NA NA
8-10 2 1
11-26 2 3
27-63 3 5
64-110 4 6
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CQI Periodic Reporting on PUCCH or PUSCH• Wideband feedback or UE selected sub-band• Period configurable
– 2, 5, 10, 20ms
• Wideband feedback similar to aperiodic reporting • UE selected sub-band:
– A single CQI result per report– The total number of sub-bands is divided into J fractions called bandwidth parts – Only the best sub-band per BW part is reported – Example: for 3 MHz there are 4 RBs per sub-band so there are 15/4 = 4 sub-bands.
Those 4 sub-bands are divided into 2 BW parts which means that there are 2 sub-bands per BW part.*
• Configured by higher layer signaling BW / RB Subband Size k (RBs)
BW Parts (J)
6-7 NA NA
8-10 4 1
11-26 4 2
27-63 6 3
64-110 8 4
cqiPerNpCQI periodicity LNCEL; 2; 5; 10; 20; 20 ms
* A sub-band index is also signaled
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Zadoff-Chu sequences• Zadoff-Chu sequences are used as
– UL demodulation and sounding reference signals– random access preamble sequence– DL primary synchronization signal
• ZC sequences are CAZAC (constant amplitude zero autocorrelation) sequences
– Low cubic metric and flat frequency response• The elements of ZC sequence are points from unit circle• It is possible to create ZC sequences of any length with
relatively simple formulas• Depending on sequence length different number of base/root
sequences can be formed – Sequence with prime number of elements is optimal– Root sequence can be considered as circular. Different cyclic shifts of
a root sequence can be obtained by changing the starting element▪ Cyclic shift must be larger than time ambiguity of received sequence
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Uplink Control Signaling: PUCCH vs. PUSCH
• PUCCH (Physical Uplink Control Channel)
– Used when the UE is not sending data simultaneously
– Shared frequency and time resource reserved exclusively for the UEs transmitting only L1/L2 control signals
– Optimized for large number of simultaneous UEs with relatively small number of control signaling bits per UE (1…11)
– Very high multiplexing capacity, spectral efficiency e.g.
▪ 18 UEs/RB transmitting ACK/NACK (PUCCH Format 1a/1b)
▪ 6 UEs/RB transmitting 11-bit CQI + 2-bit A/N (PUCCH Format 2b)
• PUSCH (Physical Uplink Shared Channel)
– Used when the UE transmits also data
– UE-specific resource that can be used for L1/L2 control signaling (based on scheduling decisions made by Node B)
– Capable to transmit control signals with large range of supported control sizes (1… 64 bits)
– TDM between control and data (multiplexing is made prior DFT)
Single carrier limitations:Simultaneous transmission of PUCCH and PUSCH is not allowed. Separate control resources for the cases with and without UL data are required
*TDM = Time Domain Multiplexing
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PUCCH, basics
• PUCCH (from single-UE perspective)– Frequency resource of one RB– Time resource of one sub-frame (A/N repetition is also supported)
• Slot based frequency hopping is always used– It provides the sufficient degree of frequency diversity– Hopping takes place on the band edges, symmetrically over the center
frequency
• Multiplexing between UEs– FDM btw RBs– CDM inside the RB
slot
systembandwidth
Resource block
PUCCH
* FDM = Frequency Division MultiplexingCDM = Code Division Multiplexing A/N = ACK/NACK
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PUCCH, UE Multiple Access Within a RB
• UEs are separated using of CDM (within an RB)• Two orthogonal CDM techniques are applied on PUCCH
– CDM using cyclic shifts of CAZAC* sequence– CDM using block-wise spreading with the orthogonal cover sequence
• Multiplexing example: PUCCH Format 1/1a/1b (e.g., A/N)– Both CDM techniques are in use -> 18 parallel resources
*) The applied sequences are not true CAZAC but computer searched Zero-Autocorrelation (ZAC) sequences
RS RS RS
slot
SF=3
SF=4
Cyclic Orthogonal cover codeshift 0 1 2
0 0 121 62 1 133 74 2 145 86 3 157 98 4 169 10
10 5 1711 11
block-wise spreading
CDM inCS
domain
SF = 3 for Reference Signals and SF = 4 for ACK/NACKSF = Spreading Factor
deltaPucchShiftdelta cyclic shift for PUCCH formats 1/1a/1b LNCEL; 1..3; 1; 2 (i.e. 6 cyclic shifts)
*CDM = Code Division Multiplexing
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PUCCH Formats
• Format 1/1a/1b– Length-12 CAZAC sequence modulation + block-wise
spreading -> 1 symbol (1 or 2 bits per slot)
• Format 2/2a/2b– Length-12 CAZAC sequence modulation (& no block-wise
spreading) -> 5 symbols per slot
PUCCH formats Control typePUCCH Format 1 Scheduling requestPUCCH Format 1a 1-bit ACK/NACKPUCCH Format 1b 2-bit ACK/NACKPUCCH Format 2 CQIPUCCH Format 2a CQI + 1-bit ACK/NACKPUCCH Format 2b CQI + 2-bit ACK/NACK
Number of Bits Multiplexing Capacity (UE/RB)ON/OFF keying 36, *18, 12
1 36, *18, 12 2 36, *18, 12
20 12, *6, 42122
12,* 6, 412, *6, 4
*typical value
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Mapping of logical PUCCH resources into physical PUCCH resources
m=1 m=0m=3 m=2
m=2 m=3m=0 m=1
slot
systembandwidth PUCCH
• Periodic CQI is located at the outermost RBs– These resources are allocated explicitly via RRC
• SR and persistent A/N are next to Periodic CQI– These resources are allocated explicitly via RRC
• Dynamic A/N is located at the innermost PUCCH RBs– Allocated implicitly based on PDCCH allocation
m = 0 & 1 may contain formats 2/2a or 2b (e.g. CQI) -> fixed allocation
m = 2 & 3 may contain formats 1/1a or 1b (e.g. ACK)-> dynamic allocation