02 Channel Config GC

1 © Nokia Siemens Networks RA41212EN20GLA1

LTE Radio Parameters RL20Channel Configuration


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


Module Contents

• Overview• DL Channels and Signals• UL Channels and Signals


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


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


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


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


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


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


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


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)


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


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


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


Module Contents



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


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


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)


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


Antenna port 1


Antenna port 2


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


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.


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


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


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


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


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


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)


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


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


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


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


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.


Module Contents



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


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


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


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)


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


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


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


No PMIMode 1-0

4 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)


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


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


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


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


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


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


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


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


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

02 Channel Config GC

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