channel config ra
TRANSCRIPT
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LTE Radio Parameters RL60
Channel Configuration and Random
Access
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Module Objectives
After completing this module, the participant should be able to describe
discuss and analyze:
• UL and DL channels
• DL channel Configuration
• UL Channel Configuration and related Parameters
• Overall RA process• Contention-based and contention-free RA
• PRACH configuration options
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Module Contents
• Overview
• DL Channels and Signals• UL Channels and Signals
• Random Access
• RA Procedure
• Preamble Generation
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Overview - Channels
Upper Layers
RLC
MAC
PHY
Logical channels
Transport channels
B C C H
C C C H
P C C H
MT C H
M C C H
B C H
P C H
DL - S C H
RA C H
UL - S C H
P B C H
P D S C H
P HI C H
P D C C H
P C F I C H
P M C H
P U C C H
P RA C H
P U S C H
M C H
C C C H
D C C H
DT C H
ULDL
Air interface
D C C H
DT C H
S y n c h
R S
S R S
D R S
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DL Physical Channels Allocation
- RS: Reference Signal
• Occupies at least 8 RE per RB(84 RE for normal CP )
throughout the whole system bandwidth
- PSS/SSS: Primary/Secondary Synchronization 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
alternative during symbols 1 to 3 of each TTI
- PDCCH: Physical Downlink Control Channel
• Occupies the REs not used by PCFICH and PHICH andReference 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
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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
• SIB2 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
– 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
CQI, PMI, RI,
ACK/NACK
SR
RNTI
DL scheduling
UL Grant
UL Power Control
n x per cell
DL control
configuration
1x per cell
HARQ Info
CQI, PMI, RI,
ACK/NACK
Overview – Control Information
CQI: Channel Quality Indicator
PMI: Precoding Matrix Indicator
RI: Rank Indicator
SR: Scheduling Request
ACK: Acknowledgement
NACK: Negative Acknowledgement
RNTI: Radio Network Temporary Indicator
HARQ: 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
FDD CarrierBandwidth
[MHz]
Number ofPRB
1.4 6
3 15
5 25
10 50
15 75
20 100
ulChBw / dlChBw
Defines the UL and DL bandwidth and the
number of available Physical Resource Blocks
LNCEL1.4 MHz (14), 3 MHz (30), 5 MHz (50),
10 MHz (100), 15 MHz (150), 20 MHz (200)
10 MHz(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
N UL : earfcnUL
N DL : earfcnDL
Bandwid th
UL: u lChBw
DL: d lChBw
*Noffs-DL & Noffs-UL specified by
TS 36.101 for each band
earfcnUL/ earfcnDL
Absolute Radio Frequency Channel Number
LNCEL; 0...65535; 1; -
earfcnUL = earfcnDL + 18000
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EUTRA Channel Numbers
Examp le (band 12)
F UL = 708 MHz = 698 MHz + 0.1 (23100 – 23000) MHz
F DL = 738 MHz = 728 MHz + 0.1 (5100 – 5000) MHz
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Generic - Physical Layer 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)
• 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 synchronization using primary and secondary sync signal
Strongest Signal
Primary
Synchronization Signal
Secondary
Synchronization 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 IDgroups
Phy L Cell ID
phyCellId:Physical Cell Id
LNCEL; 0..503; 1; -
(Range; Step; Default)
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Generic - Time Structure (Frame Type 1)
19
144 Ts = 4.69 µs
160 Ts
CP Symbol C PSymbol C
PSymbol C PSymbol C
PSymbol C PSymbol C
PSymbol
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 Prefix
x2047-Ncp, … x2047
OFDM Symbol (Time Domain Samples)
x0, x1, …, x2047
Symbol Tsym = 2048 Ts = 66.67 µsTcp = Ncp Ts
Df = 15 kHz, UL/DL - Extended Prefix
Df = 7.5 kHz, UL/DL - Extended Prefix
Df = 15 kHz, UL/DL - Normal Prefix
Slot = 15360 Ts = 500µs
7.5kHz Only used for MBMS
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Generic – Time Structure and CP length
- 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)
Short cyclic prefix:
Long cyclic prefix:
Copy= Cyclic prefix
= Data
5.21 s
16.67 s
Ts: ‘sampling time’ of the overallchannel. Basic Time Unit.
Ts =1 sec
Subcarrier spacing X max FFT size
= 1 sec
15kHz X 2048
= 32.5nsec
Subcarrier spacing= 15kHz; max. FFT size= 2048
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Module Contents
• Overview
• DL Channels and Signals• UL Channels and Signals
• Random Access
• RA Procedure
• Preamble Generation
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DL - Channels and Signals Overview
Upper Layers
RLC
MAC
B C C H
C C C H
P C C H
MT C H
M C C H
B C H
P C H
DL - S C H
P B C
H
P D S C
H
P HI C
H
P D C
C H
P C F I C H
P M C
H
M C H
Air interface
D C C H
DT C H
S yn c
h
R S
PHY
HI
C F I
D C I
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180 kHz
0.5 ms
Secondary Synchronization Signal (SSS)
Primary Synchronization Signal (PSS)
DTX
Slot id: 0 1 2 . . ..10.. ..19 0 1
Synch Signals – Time and Frequency
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Incremental Time-Frequency Structure of Cell-specific Reference Signals
0l
0 R
0 R
0 R
0 R
6l 0l
0 R
0 R
0 R
0 R
6l
O n e a n t e n n a p
o r t
T w o a n t e n n a p o r
t s
Resource element (k,l )
Not used for transmission on this antenna port
Reference symbols on this antenna port
0l
0 R
0 R
0 R
0 R
6l 0l
0 R
0 R
0 R
0 R
6l 0l
1 R
1 R
1 R
1 R
6l 0l
1 R
1 R
1 R
1 R
6l
0l
0 R
0 R
0 R
0 R
6l 0l
0 R
0 R
0 R
0 R
6l 0l
1 R
1 R
1 R
1 R
6l 0l
1 R
1 R
1 R
1 R
6l
F o u r a n t e n n a p o r t s
0l 6l 0l
2 R
6l 0l 6l 0l 6l
2 R
2 R
2 R
3 R
3 R
3 R
3 R
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 ……….. 6 l=0 ……...... 6, 0 ……….. 6
l=0 ……...... 6, 0 ……….. 6
Antenna port 0 Antenna port 1 Antenna port 2 Antenna port 3
F o u r a n t e n n a p o r t s
T w o a n t e n n a p o r t s
O n e a n t e n n a p o r t
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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
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 B s
U s e d b a n d w i d t h
1 R B
One subframe (2 slots) 1 ms
Segmentation into four equal sized individually self-decodable units
PBCH
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Physical Layer DownlinkDL-Physical Data & Control Channels
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,>
PCFICH
• 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 ineach 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)
• 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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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, 1PHICH group. 12 symbols are to be transmitted.
- NRBDL : DL BW / RBs
- Ng = 1/6, 1/2, *1,* 2. setting: phichRes
prefixcyclicextendedfor82
prefixcyclicnormalfor8
DL
RBg
DL
RBggroup
PHICH
N N
N N N
+j -j -j +j7
+j +j -j -j6
+j -j +j -j5
+j +j +j +j4
+j -j+1 -1 -1 +13
+j +j+1 +1 -1 -12
+1 -1+1 -1 +1 -11
+1 +1+1 +1 +1 +10
Extended CPNormal CP
Orthogonal sequenceSequence
Index
+j -j -j +j7
+j +j -j -j6
+j -j +j -j5
+j +j +j +j4
+j -j+1 -1 -1 +13
+j +j+1 +1 -1 -12
+1 -1+1 -1 +1 -11
+1 +1+1 +1 +1 +10
Extended CPNormal CP
Orthogonal sequenceSequence
Index
Number of RBs
phichRes
#PHICH groups
LNCEL; 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 asmodifier 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
PhichDur
PHICH 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 exists
LNCEL; 1(0), 2 (1), 4 (2), 8 (3); -; 4 (2)
The target error probability for a missed detection of a PDCCH is 10-2
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DL - L1/L2 control info: PDCCH Resources
- The Maximum Number Of OFDM Symbols For PDCCH parameter defines how many OFDM symbols can
be used.
- eNB selects the actual value for each TTI, which is signaled to UE in PCFICH.
- Range: 1, 2, 3 (BW > 1.4 MHz);
- Range: 2, 3, 4 (BW = 1.4 MHz)
- setting: maxNrSymPdcch
- Usage Based PDCCH Adaptation) allows to maximize PDSCH throughput and reduce PDCCH blocking
by adjusting dynamically the number of symbols used for PDCCH
- Example shows dynamic ( ActldPdcch) case for MaximumNumberOfOFDMSymbolsForPDCCH=3 (yellow)
maxNrSymPdcch
LNCEL; 1..3; 1; 3
ActldPdcch
LNCEL; false, true:false
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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
F r e q u e n c y
Time
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Exercise: PDCCH Resources
Task:- 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 AL8 AL2 is 2 times the frequency of AL4
AL1 is 1/2 times the frequency of AL2
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Solution: PDCCH Resources
Task:
- 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 CCEs
26 CCEs are consumed for 9 PDCCH.
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Downlink carrier aggregation - 40 MHz
• A regular cell is paired with additional logical cell serving
the same site sector.
• LTE 1089 supports only inter-band carrier aggregation with
specific constraints with respect to bands that are allowed tobe paired.
• Only non-GBR data could be sent via secondary cell
• All cells handling CA (Carrier Aggregation) UEs serve
simultaneously also regular, non-CA UEs
• There is no carrier aggregation in the uplink direction
PRIMARYCELL
SECONDARY
CELL
CA capable UE
Carrier 1
Carrier 2
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Downlink carrier aggregation - 40 MHz
Cells to be paired for CA feature should belong to the same
sector:
• LCELL/sectorId is a new parameter introduced by
LTE1089
• For other than CA feature this information is
meaningless
• for the cells to be aggregated the same sectorId in LCELL
associated with the given LNCEL should be provided
• No more than 2 cells with the same sectorId could be
configured
LCELL
sectorId
LNBT
S
LNCEL
LCELLsectorId
CAREL
lcrId
LNCELSectorid Cell sector id
LNCEL; 0…255; -
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Downlink carrier aggregation - 40 MHz
• In the next step, logical cell that could be used
as a secondary one (from the primary cell point
of view) should be explicitly configured – inanother words, a relation between PCell and
SCell is created.
• This relation is realized via providing the lcrId
(matching with LNCEL/lcrId of the secondary
cell) in the new CAREL object under LNCEL of
the primary cell
• CAREL/lcrId should be unique within the site
LCELL
sectorI
d
LNBTS
LNCEL
LCELLsectorId
CAREL
lcrId
LNCELlcrId
PCell
SCell
LCRID Local cellresource ID of cell to
be aggregated
CAREL; 0…255; -
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Downlink carrier aggregation - 40 MHz
In case of Carrier Aggregation enabled still 420 users per given cell
could be active (like in non-CA case with 6 cells) however:
• At maximum 50 of them can
have secondary cell
configured (= added) and
• At maximum 50 others of
them can have this cell
configured as a secondary
one.
Cell
2
Cell
1
Max 420
Active UEs
C e l l s i n C a r r i e r a g g
r e g a t i o n
Max 50 CA PCell UEs
Max 50 CA PCell UEs
Max 50 CA
SCell UEs
Max 50 CA
SCell UEs
Cell 1 is SCell of Cell 2
Cell 2 is SCell of Cell 1
Max 420
Active UEs
Note:
This number could be
limited by
maxNumCaConfUeDc
parameter set in PCell
(by default equal to 20)
maxNumCaConfUeDc
Max number Carrier Aggr
configured UEs double carrier
LNBTS; 0…50; -20
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Downlink carrier aggregation - 40 MHz
There are two possible ways to activate the
secondary cell for the UEs for which
secondary cell was already added. The choice
depends on the setting of thesCellActivationMethod parameter:
•Blind (sCellActivationMethod = BLIND)
•Buffer based (sCellActivationMethod =
nonGBRBufferBased)
Period activation occassion
Configure UE with SCell
SCell configured, not
activated
Scell
activated
Start periodic
activation cycle
Compare nGBR buffer
against current
activation threshold
Scell activated
Restart
timer
Start
calculatingactivation
threshold
value
RRM signaling
nGBR buffer based
At sub frame n+8
Blind activation
sCellActivationMethod
SCell activation method
LNBTS :nonGBRBufferBased (0),blind (1); - nonGBRBufferBased
(0)
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DL Carrier Aggregation
Buffer based activation of the secondary cell
means that every sCellActivationCyclePeriod it is
checked whether all non-GBR data awaiting initialtransmission in the buffer of that UE is greater than
the certain dynamically calculated threshold.
amount of data that could be
transmitted solely by the
primary cell based on the
throughput reached in the
past by this UE Period activation occasion
Configure UE with SCell
SCell configured, not
activated
Scell
activatedStart periodic
activation cycle
Compare nGBR buffer
against currentactivation threshold
Scell activated
Restart
timer
Start
calculatingactivation
threshold
value
RRM signaling
nGBR buffer based
At sub frame n+8
Blind activation
sCellActivationCyclePeriodSCell activation cycle period
LNBTS : 0.5s (0), 1s (1), 2s
(2), 4s (3), 8s (4), 16s (5) : 2
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SCell activation:
buffered nGBR data
exceeds activaton
threshold
Simplified scenario is shown, with equal split of nGBR data between PCell and SCell
Time (individual TTIs)
n+8 TTI: start of
actual
transmission
over SCell
Not enough
buffered data to
use both PCell
and SCell
Sufficient amount of
data to use SCell
again
Not enough buffered
data to use both PCell
and SCell
SCell deactivation at the expiry
of sCellDeactivat ionTimerEnb
nGBR
data sent
over SCell
nGBR
data sent
over PCell
…….
Downlink carrier aggregation - 40 MHz
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Downlink carrier aggregation - 40 MHz
• The division factor is limited to the range of 10…90% to avoid possible deadlock.
• If any of the serving cells succeeds in allocating all of its data share in current TTI (while
the other cell does not), this indicates that this cell has high scheduling potential.
Therefore in the next TTI it will be given additional 10% of the throughput share
0% 10% 90% 100%
PCell SCell
Division factor
The buffered non-GBR data is divided between PCell and SCell according to non-
GBR throughput share achieved in the past
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Downlink carrier aggregation - 40 MHz
• Additional cell bandwidth combinations are supported on top of RL50 band combinations:
BW1 BW2
5 MHz 5 MHz
5 MHz 10 MHz
10 MHz 10 MHz5 MHz 15 MHz
5 MHz 20 MHz
10 MHz 15 MHz
10 MHz 20 MHz
15 MHz 15 MHz15 MHz 20 MHz
20 MHz 20 MHz
All these new RL60 combinations are supported
by FSMF only
Supported already in RL50; FSME/FSMF
Supported already in RL50; FSME/FSMF
Supported already in RL50; FSMF
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Downlink carrier aggregation - 40 MHz
Support for additional band combinations are provided in RL60 on top of RL50:
Band A Band B
Band 1 2100 Band 5 850
Band 1 2100 Band 8 900
Band 3 1800 Band 5 850
Band 3 1800 Band 8 900
Band 5 850 Band 12 US 700
Band 1 2100 Band 18 800 Lower
Band 1 2100 Band 7 2600
Band 2 1900 PCS Band 4 AWS
Band 2 1900 PCS Band 5 850
Band 2 1900 PCS Band 17 700
Band A Band B
Band 3 1800 Band 3 1800
Band 3 1800 Band 7 2600
Band 3 1800 Band 20 800
Band 4 AWS Band 4 AWS
Band 4 AWS Band 17 700
Band 5 850 Band 7 2600
Band 7 2600 Band 20 800
Band 4 AWS Band 12 Lower 700
Band 3 1800 Band 28 700
Band 4 AWS Band 7 2600
Band 7 2600 Band 7 2600
All the RL60 combinations are supported by FSMF only
R L
5 0
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Downlink carrier aggregation - 40 MHz
• From RL60 onwards, intra-band combinations for CA are also supported.
• Two cases of intra-band allocation could be here distinguished:
• Distinction between contiguous and non-contiguous way of intra-band
allocation affects e.g.:
• Allowed allocation of center frequencies of the two involved carriers,
• Handling of UE capabilities,
• Requirements posed on the synchronization between carriers.
contiguous intra-band
allocation of CA
component carriers
non-contiguous intra-band
allocation of CA
component carriers
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Module Contents
• Overview
• DL Channels and Signals• UL Channels and Signals
• Random Access
• RA Procedure
• Preamble Generation
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UL Channel Mapping
Upper Layers
RLC
MAC
PHY
R A C H
C C C H
D C C H
D T C H
Air interface
P R A C H
P U S C H
U L - S C H
P U C C H
U C I
DR S
S R S
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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 thechannel 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 stateinformation is called Channel Sounding; it is done using the
Sounding Reference Symbols, SRS (not considered in this
presentation)
(1) eNodeBtransmission
(3) UEfeedback
(2) UE CSImeasurement
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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 exceed10%
CQI index modulation
coding rate x1024
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 spatialmultiplexing
• 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
riEnable
Determines whether RI reporting isenabled (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 Loo p MIMO
Example: codebook for 2 TX antennas
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Precoding Matrix Indicator (PMI)
RL50: supports 4x2 closed loop 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/RItransmission is periodic reporting on
PUCCH
• If the UE is scheduled to send UL data inthe subframe where it should transmitperiodic CQI/PMI/RI, the periodic report ismoved to PUSCH and multiplexed with data
• The eNodeB configures the periodicity
parameters
• The size of a single report is limited up toabout 11 bits depending on the reportingmode
• Limited amount of frequency information
Aperiodic Reporting
• Aperiodic reports are explicitlytriggered by the eNodeB using a
specific bit in the PDCCH UL grant• Aperiodic report can be eitherpiggybacked with data or sent aloneon PUSCH
• Possibility for large and detailedreports (up to more than 64 bits)
The two modes can also be used to com plement
each other:
- The UE can be e.g. config ured to s end
Aper iodic repor ts only w hen i t is sch eduled,
whi le per iodic repor ts can provide co arse
channel informat ion on a regular basis
CQIAperEnable
enabling / disabling aperiodic CQI
/RI/PMI reporting on PUSCH.
LNCEL; false/true; true
cqiPerNp
CQI periodicityLNCEL; 2; 5; 10; 20; 20 ms
Categorization of CQI/PMI/rank reporting options
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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 PMI
Mode 2-0
24 bits
No PMI
Mode 3-0
30 bits
Multi PMI
1-2
60 bits
Single PMI
Mode 3-1
64 bits
Multi-PMI
Mode 2-2
38 bits
Wideband
No PMI
Mode 2-0
6 bits
Single PMI
Mode 2-1
11 bits
No PMI
Mode 1-0
4 bits
Single PMI
Mode 1-1
11 bits
Single or Multi-PMI = closed loopMIMO with PMI feedback
No PMI = Single antenna, TxDiv orOL MIMO
The maximum number of feedback bitsfor each option Assuming 20 MHz BWand 4*4 CL MIMO is listed excluding RI
- With Periodic reporting RI is sent inseparate subframes with potentiallylarger periodicity
- In Aperiodic reporting The RI isseparately coded with each CQI/PMIreport
*See TS 36.213
cqiAperMode
Aperiodic CQI feedback mode
LNCEL; FBT1(0) – Family modes 2-x, FBT2(1)- Family modes 3-x
(x defined by MIMO algorithm internal in eNodeB); FBT2 (1)
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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 with3 MHz BW (15 RBsmeans that the sub-band size is 2 RBsand 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 8
PRB index 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
BW /RB
Sub-bandsize
(RBs)
# bestSub-
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
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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 SubbandSize 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
cqiPerNp
CQI periodicity
LNCEL; 2; 5; 10; 20; 20 ms
* A sub-band index is also signaled
The UE shall report a type 1 report per bandwidth part。
Type 1 report supports CQI feedback for the UE selected sub-bands
Type 2 report supports wideband CQI and PMI feedback.
Type 3 report supports RI feedback
Type 4 report supports wideband CQI
Uplink Control Signaling:
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Uplink Control Signaling:
PUCCH vs. PUSCH
•PUCCH (Physical Uplink Control Channel)
• Used when the UE is not sending datasimultaneously
• Shared frequency and time resourcereserved exclusively for the UEstransmitting only L1/L2 control signals
• Optimized for large number ofsimultaneous UEs with relatively small
number of control signaling bits per UE(1…11)
• Very high multiplexing capacity, spectralefficiency 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 usedfor L1/L2 control signaling (based onscheduling 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 carr ier l imitat ion s :
Simultaneous transmission of PUCCH and PUSCH isnot allowed. Separate control resources for the caseswith and without UL data are required
*TDM = Time Domain Multiplexing
Zadoff-Chu sequences
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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 rootsequence can be obtained by changing the starting element
- Cyclic shift must be larger than time ambiguity of received sequence
UL Reference Signal
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U e e e ce S g a
Overview
Types of UL Reference Signals
- Demodulation Reference Signals (DM RS)
• PUSCH/PUCCH data estimation
- Sounding Reference Signals (SRS)
• Mainly UL channel estimation UL
DM RS is characterised by:- Sequence (Zadoff Chu codes)
- Sequence length: equal to the # of subcarriers used for PUSCH transmission
- Sequence group:
- 30 options
- Cell specific parameter
- Cyclic Shift: UE and cell specific parameter
UL DM RS allocation per slot for
Normal Cyclic Prefix
G f f
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Group hopping for UL reference signal
• This feature randomises the sequence used to generate the:
• Demodulation Reference Signal for the PUCCH
• Demodulation Reference Signal for the PUSCH
• Sounding Reference Signal (SRS)
• Helps to improve performance when the ‘PCI mod 30’ rule was not followed
during the PCI planning process
• reduces risk of potential issues caused by cross-talk between neighboringcells
• UE are informed whether group hopping is enabled or disabled using SIB2
content
actUlGrpHop
Activation of uplink group hopping
LNCEL; 0 (False); 1 (True); 0 False
G h i f UL f i l
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Group hopping for UL reference signal
• Uplink Reference Signals are:
• Demodulation Reference Signal for PUCCH
• Demodulation Reference Signal for PUSCH
• Sounding Reference Signal (SRS)
PUCCH Formats
1, 1a, 1bPUCCH Form ats 2, 2a,
2bPUSCH SRS
Group hopping for UL reference signal
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Group hopping for UL reference signal
Groups of Base Sequences
• All uplink Reference Signals are generated from the same set of base sequences
• There are 30 groups of base sequences
• Each group includes multiple sequences
• 1 sequence of
lengths 12, 24, 36,
48 and 60
• 2 sequences of
lengths 72, 84, 96, …
1200
Each group contains
G h i f UL f i l
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Group hopping for UL reference signal
Group Allocation
• The allocated group for a cell is not planned explicitly but is calculated from:
30mod)( sssgh f n f u
30modcellID
PUCCHss N f
30modssPUCCH
ssPUSCH
ss D f f
Group
PUCCH & SRS
PUSCH
PCI
Configurable Offset
(grpAssigPUSCH )
Psuedo random sequence initialized using
ROUNDDOWN [PCI / 30]
enabledishoppinggroupif 30mod2)8(
disabledishoppinggroupif 0)( 7
0 ssgh
i
iincn f
PUCCH, basics
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,
• 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 Multiplexing
CDM = Code Division Multiplexing
A/N = ACK/NACK
PUCCH UE Multiple Access Within a RB
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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 computersearched Zero-Autocorrelation (ZAC) sequences
RS RS RS
slot
SF=3
SF=4
Cyclic Orthogonal cover code
shift 0 1 2
0 0 12
1 6
2 1 13
3 7
4 2 14
5 8
6 3 15
7 98 4 16
9 10
10 5 17
11 11
block-wise spreading
CDM in
CS
domain
SF = 3 for Reference Signals and SF = 4 for ACK/NACKSF = Spreading Factor
deltaPucchShift
delta cyclic shift for PUCCH formats 1/1a/1b
LNCEL; 1..3; 1; 2 (i.e. 6 cyclic shifts)
*CDM = Code Division Multiplexing
PUCCH Formats
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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 type
PUCCH Format 1 Scheduling request
PUCCH Format 1a 1-bit ACK/NACK
PUCCH Format 1b 2-bit ACK/NACK
PUCCH Format 2 CQI
PUCCH Format 2a CQI + 1-bit ACK/NACK
PUCCH Format 2b CQI + 2-bit ACK/NACK
Number of Bits Multiplexing Capacity (UE/RB)
ON/OFF keying 36, *18, 12
1 36, *18, 122 36, *18, 12
20 12, *6, 4
21
22
12,* 6, 4
12, *6, 4
*typical value
Mapping of logical PUCCH resources into physical PUCCH resources
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Mapping of logical PUCCH resources into physical PUCCH resources
• 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=1 m=0
m=3 m=2
m=2 m=3
m=0 m=1
slot
system
bandwidthPUCCH
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
PUCCH Dimensioning (1/2)
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PUCCH Dimensioning (1/2)
- Scope: Dimensioning of the PUCCH region (how many RBs) to avoid excessive
overheads
- Necessary to calculate how many PUCCH resources (m) are needed for Formats1.x and
Formats 2.x
PUCCH Dimensioning (2/2)
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PUCCH Dimensioning (2/2)
- Total number of Resources required for PUCCH is the sum of the resources required for
scheduling requests, for CQI and for Dynamic ACK/NACK:
MaxPucchResourceSize = nCqiRb + roundup {[((maxNumOfCce) + n1PucchAn –
pucchnanCS * 3 / deltaPucchShift ) * deltaPucchShift] / (3*12)} + roundup(pucchnanCS / 8)
nCqiRb
reserved RBs per slot for
PUCCH formats 2/2a/2b
LNCEL; 1..98; 1; 2
pucchnanCS
Number of cyclic shifts for
PUCCH formats 1/1a/1b
in the mixed region
LNCEL; 0..7; 1; 0
(0 means no use of mixedformats )
n1PucchAn
Offset to calculate ACK/NACK
resources from PDCCH CCE
LNCEL; 0..2047; 1; 36
maxNumOfCce depends on dlChBw parameter:
- if dlChBw is 5MHz then maxNumOfCce is 21
- if dlChBw is 10MHz then maxNumOfCce is 43
- if dlChBw is 15MHz then maxNumOfCce is 65
- if dlChBw is 20MHz then maxNumOfCce is 87
deltaPucchShift
delta cyclic shift for PUCCH
formats 1/1a/1b
LNCEL; 1..3; 1; 2
Flexible Uplink Bandwidth
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p
• Achieved by increasing the bandwidth allocated toPUCCH, and not using the resources situated at
spectrum edge.
•LTE transmission bandwidth thus reduced, leaving
blanked areas at bandwidth edge.
•Blanked areas serve as a guard band for reducing
out of band emissions
Purpose of the feature is to define an area at the borders of uplink band
where PUSCH nor PUCCH are not allocated to any UE
0 1 2 3 4 5 6 7 8 9 1011 1213141516171819202122232425262728293031323334353637383940414243444546474849
Blankedarea
PUSCHresourcesPUCCHarea
Deployment possible with narrower spacing
WCDMA 5MHz LTE 5 MHz
blankedPucch
Blanked PUCCH resources):
LNCEL; 0..60; 1; 0
LTE786 modifies the receiver at the eNodeB. The blanked PUCCH PRBs are not received, therefore they do not influence the
received SINR. This means that the blanked resources do not contribute to the PUCCH RSSI nor SINR statistics, the
measurements of the PUSCH RSSI and SINR are performed on the reduced amount of PRBs
Example configuration (uplink bandwidth 10 MHz 50PRBs)
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PUCCH Format 1.x
area
Example configuration (uplink bandwidth 10 MHz, 50PRBs)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49
0 2 4 6 8 10 12 14 16 18 20 22 24 25 23 21 19 17 15 13 11 9 7 5 3 1
1 3 5 7 9
11 13 15 17 19 21 23 25 24 22 20 18 16 14 12 10 8 6 4 2 0
ulChBw = 10 MHz
0 1 2 3 4 5 6 7 8 9 1011 1213141516171819202122232425262728293031323334353637383940414243444546474849
0 2 4 6 8 9 7 5 3 1
1 3 5 7 9 8 6 4 2 0
nCqiRb = 20
blankedPucch =
16
Total PUSCH area: 40
PRBs
nCqiRb= 4
Total
PUCCH
area:
2x5PRB
No PUCCH blanking
PUCCH Format 2.x allocations
starting from PUCCH allocation
region 16 (PRB #8)
With PUCCH blanking
Actual blanked
area: 2x8PRB
Blanked
zone
Area
reserved
with nCqiRb
Frequency(PRBs)
Total PUSCH area: 24
PRBs
Total
PUCCH
area:
2x5PRB
PUSCH masking
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PUSCH masking
The PUSCH blanking feature allows to overcome the regulatory limitations of
certain zones in the uplink
This allows the opertors to deploy LTE in wider system bandwidth, rather than in
two separate smaller systems• Obvious benefits in downlink capacity and especially peak throughputs (user
experience, marketing reasons)
• No need for inter-frequency measurements and handovers (measurement gaps!),
load balancing etc.
uplink downlink uplink downlink
5 MHz + 10 MHz 20 MHz + PUSCH blanking
Combined capacity:
100Mbps (32+68)
Capacity:
142Mbps
PUSCH masking
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PUSCH masking
Each zone is determined by two parameters:
Length of the muted zone
First PRB that will be muted
ulsPuschMaskLength
LNCEL: Range: [1..100] (*)
Default: no
(*) actual values depend on ulChBw
These uplink resources
will never be allocated
11
PRBs
ulsPuschMaskStart
LNCEL : Range: [0..99] (*)
Default: no
(*) actual values depend on ulChBw
ulsPuschMaskStart =13
ulsPuschMaskLength = 11 11 PRBs muted: [#13 .. #23]
Sounding Reference Signal
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UE specific channel state
information (CSI) is derived
from:
- PUSCH
- sounding reference signals
(SRS)
The SRS configurations provide
UEs by two SRS classes which are
introduced by feature:
SRS class …
that assigns a multitude of
resources for a limited number of
UE’s
that provides sufficient SRS
resources for the proper
scheduling of the UEs
UE scheduling & SRS Configuration
SRS Configuration
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- The operator can choose an SRS configuration from a given set of predefined
configurations tailored for the usable PUSCH spectrum - srsConf igurat ion
- The SRS resources which are selected for the UEs are assigned by means of the RRC
Connection Reconfiguration and RRC Connection Reestablishment messages.
- The usage of measurements from SRS in closed loop uplink power control can be
enabled/disabled by setting the parameter Include SRS measurements In CL power
control (ulpcSrsEn ).
……
Wid b d SRS T i i N b d SRS T i i
SRS Bandwidths
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Wideband SRS Transmission
(Non Frequency hopping SRS )
Sounding reference signal
1 6 R B s
Subframe 1 Subframe 6 Subframe 1 Subframe 2
Narrowband SRS Transmission
(Frequency hopping SRS )
Minimum Narrow
SRS bandwidth
= 4 RBs
More
wideband
SRS
bandwidth
= 4 RBs 3
= 12 RBs
SRS BW
config.
SRS
BW0
SRS
BW1
SRS
BW2
SRS
BW3
0 48 24 12 4
1 48 16 8 4
2 40 20 4 4
3 36 12 4 4
4 32 16 8 4
5 24 4 4 4
6 20 4 4 4
7 16 4 4 4
System bandwidths 40 –60 RBs.
Parameter SRSConfiguration defines the srs configuration.
Each option defines the values of a set of 3GPP parameters (Csrs, Bsrs) dedicated to SRS. See Tables 5.5.3.2-x in TS.36.211.
Module Contents
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• Overview
• DL Channels and Signals
• UL Channels and Signals
• Random Access
• RA Procedure
• Preamble Generation
Overview
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Random access procedure is performed for the following events:
• Initial access from RRC_IDLE
• RRC Connection Re-establishment procedure
• Handover
• DL data arrival during RRC_CONNECTED requiring random access procedure
• UL data arrival during RRC_CONNECTED requiring random access procedure
• E.g. when UL synchronization status is "non-synchronized" or there are no
PUCCH resources for SR available
It takes two distinct forms:• Contention based (applicable to all five events);
• Non-contention based (applicable to only handover and DL data arrival)
Normal DL/UL transmission can take place after the random access procedure
In total there are 64 preambles per cell (pooled into 2 groups)
Preambles are grouped to indicate the length of the needed resource. A number of preambles are reserved for contention-free access
PRACH
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PRACH channel structure for preamble format type 0
UE sends the preamble to the network on PRACH:
• PRACH occupies 6 resource blocks (of 180 kHz) ina subframe (or set of consecutive subframes)
reserved for sending random access preamble to
the network.
• The length of TCP (Cyclic Prefix) TPRE (Preamble)
and TGT (Guard Time) depends on the preamble
format
• PRACH reserved PRBs cannot be used by PUSCH
i.e. they are out of scope for scheduling for data
transmission
PRACH Types
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PRACH types:
• Type 0: 1 ms duration
• Type 1: 2 ms
• Type 2: 2 ms
• Type 3: 3 ms
Format type 0 & type 1 supported
in RL60
PRACH Configuration
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Type, time resources are defined by:
.
*3GPP TS 36.211 Table 5.7.1-2
prachConfIndex
LNCEL; 3..24;1; 3
Range is restricted to two different
ranges: 3-8 and 19-24 (internal)
PRACH configuration index:
PRACH
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Where PRACH is placed in frequency domain:
• PRACH can be placed either on lower or upper edge of the
bandwidth• Therefore the possible range for prachFreqOffset is:
f r e q
tim
e
f r e q
tim
e
...
..
.
60UL
RB N n RA
PRBoffset
prachFreqOffset = roundup [maxPucchResourceSize /2]
If PRACH area is placed at the lower border of UL frequency
band then:
prachFreqOffset = MAXNRB – 6 - roundup
[maxPucchResourceSize /2]
If PRACH area is placed at the upper border of the UL frequency
band then:
The PRACH area (6 PRBs) should be next to PUCCH area either
at upper or lower border of frequency band to maximize the
PUSCH area but not overlap with PUCCH area
PUCCH
PRACH
Module Contents
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• Overview
• DL Channels and Signals
• UL Channels and Signals
• Random Access
• RA Procedure
• Preamble Generation
RA Procedure
- Random access procedure handled by MAC and PHY Layer through PRACH (in UL) and PDCCH (
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y y g ( ) (
in DL)
- RACH only carries the preambles and occupies 6 resource blocks in a subframe
•Process:
- UEs selects randomly a preamble from the list of preambles broadcasted in the BCCH
- UE calculates OLPC parameters ( Initial Tx Power)
- Checks contention parameters (i.e. max. number of retries)
- UE transmits initial RACH and waits for a response before retry. Open loop PC ensures that each
retry will be at a higher power level.
- Upon receipt of successful UL RACH preamble, eNB calculates power adjustment and timing
advance parameters together with an UL capacity grant ( so UE can send more info )
DL
PUSCH: UE specific data
PRACH
response
ULPreamble
Not detected
Preamble
NextPRACHresource
On the resources indicated by PDCCH
RACH only carries the preambles ( no additional signaling or user data like in WCDMA Rel 99)
The eNodeB may also schedule data in the resource blocks reserved for random access channel preamble
transmission.
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RA Procedure
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UE eNB
RA Preamble assignment0
Random Access Preamble 1
Random Access Response2
The contention free random access procedure
• E.g. during handover a temporary valid preamble will be issued.
• It is (temporarily) dedicated to this UE.
• No contention resolution is needed as the preamble shall not be used by other UEs.
Module Contents
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• Overview
• DL Channels and Signals
• UL Channels and Signals
• Random Access
• RA Procedure
• Preamble Generation
Preamble generation
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The random access preambles are generated from:
• Zadoff-Chu root sequences (838 in total) with zero correlation zone
• one or several sequences (length 839 each)Zadoff –Chu sequence is known as a CAZAC sequence (Constant Amplitude Zero
AutoCorrelation waveform).
There are 64 preambles sequences available in each cell. The set of 64 preamble
sequences in a cell is found by including first, in the order of increasing cyclic shift, all
the available cyclic shifts of a root Zadoff-Chu sequence
# root sequences = 838 in total
# preamble sequences = 64 per cell
Fig: Zadoff-Chu sequence. The real (upper)
and imaginary (lower) parts of the complex-
valued output (Wikipedia)
Fig:
example of
preambles
generation with
zero
autocorrelation
zone length equalto 279
(prachCS=14)
Preamble generation
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Zero correlation zone and Cyclic shift
• zero correlation zone decode PRACH even if sent on the same time/ frequency
• preamble signals generated based on two different ZC sequences are not correlated within the geographical range
related to prachCS
• the dimensioning of the cyclic shift, must be greater than the maximum round-trip delay
Required number of different root Zadoff –Chu sequences grows with Ncs (Cyclic Shift) and the cell radius:
Limits due to premable formatsLimits due to preamble formatsLimits due to preamble formats
Preamble Generation
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64 preambles made of Zadoff-Chu sequences with zero correlation zone:
• given by the logical index RACH_ROOT_SEQUENCE
• Zadoff Chu sequence u is given by
10, ZC
)1(
ZC
N nen x N
nun j
u
*3GPP TS 36.211 Table 5.7.2-4
rootSeqIndex
LNCEL;0…837;1; 0
• ZC sequence of length 839 (prime number) is used
• 838 different root sequences available. (PRACH Root
Sequence). Also different cyclic shifts can be useddepending on cell size
• Sub-carrier spacing is 1.25 kHz
)mod)(()( ZC, N C n xn x vuvu
Preamble Generation Root Zadoff-Chu sequence order
f bl f t 0 3
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First: take all available cyclic shifts of one root
Zadoff-Chu sequence:
If not enough: take next logical index and so on
CS ZC CS CS
CS
RA RA RA RA RAstart shift shift CS shift group shift
0,1,..., 1, 0 for unrestricted sets
0 0 for unrestricted sets
( mod ) for restricted sets0,1,..., 1
v
vN v N N N
N C
d v n v n N v n n n
• Cyclic shift given by
for preamble formats 0 – 3.:
*3GPP TS 36.211 Table 5.7.2-2
prachCS
Preamble cyclic shift (Ncs configuration)
LNCEL;0…15;1; 0
prachHSFlag
Unrestricted or restricted (high speed) set selection
LNCEL; true, false; false
Preamble generation
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-ExerciseCons ider a cell of 37 km radiu s.
Provid e a sensit iv e sett ing for th e cel l size dependent parameters
Support of high speed users
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• If prachHsFlag = true the following rootSeqIndex values can be selecteddepending on prachCS (restricted set)
Cell range Required amount ofroot sequences
prachCS Possible range for rootSeqIndex
< 1.0 km 4 0 24...816
< 1.4 km 6 1 30…810
< 2.0 km 6 2 36…804
< 2.6 km 8 3 42…796
< 3.4 km 9 4 52…787
< 4.3 km 11 5 64…779
< 5.4 km 14 6 76…764
< 6.7 km 17 7 90…749
< 8.6 km 20 8 116…732
< 10.6 km 26 9 136…704
< 13.2 km 32 11 168…676
< 17.2 km 44 11 204…526
< 21.5 km 64 12 264…566
< 27.7 km 64 13 328…498
< 32.8 km 64 14 384…450
Preamble generation – High Speed Case
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high-
speed set
no delay spread delay spread = 5,2 µs
With
preamble
guard
NCs
Configuration NCS
sign. per
root seq. #root seq. µs km µs km Guard NCS µs km µs km
0 15 18 4 14.3 2.15 9.1 1.37 2.25 12.75 12.2 1.82 7.0 1.04
1 18 15 6 17.2 2.57 12.0 1.79 2.25 15.75 15.0 2.25 9.8 1.47
2 22 12 6 21.0 3.15 15.8 2.37 2.25 19.75 18.8 2.82 13.6 2.04
3 26 10 8 24.8 3.72 19.6 2.94 2.25 23.75 22.6 3.40 17.4 2.62
4 32 8 9 30.5 4.58 25.3 3.80 2.25 29.75 28.4 4.26 23.2 3.48
5 38 7 11 36.2 5.44 31.0 4.66 2.25 35.75 34.1 5.11 28.9 4.33
6 46 6 14 43.9 6.58 38.7 5.80 2.25 43.75 41.7 6.26 36.5 5.48
7 55 4 17 52.4 7.87 47.2 7.09 2.25 52.75 50.3 7.54 45.1 6.76
8 68 4 20 64.8 9.73 59.6 8.95 2.25 65.75 62.7 9.40 57.5 8.62
9 82 3 26 78.2 11.73 73.0 10.95 2.25 79.75 76.0 11.41 70.8 10.6310 100 2 32 95.4 14.30 90.2 13.52 2.25 97.75 93.2 13.98 88.0 13.20
11 128 2 44 122.1 18.31 116.9 17.53 2.25 125.75 119.9 17.99 114.7 17.21
12 158 1 64 150.7 22.60 145.5 21.82 2.25 155.75 148.5 22.28 143.3 21.50
13 202 1 64 192.6 28.89 187.4 28.11 2.25 199.75 190.5 28.57 185.3 27.79
14 237 1 64 226.0 33.90 220.8 33.12 2.25 234.75 223.8 33.58 218.6 32.80
If prachHsFlag = true then hsScenario must be configured
hsScenario: defines highspeed scenario for a cell. Scenario 1 (open space scenario) and
scenario 3 (tunnel scenario). Scenarios are described in 36.141 Annex B.3
Preambles - Contention and Non-Contention
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Non ContentionBased
ContentionBased
64 preambles
per cell
raNondedPreamb Total number of non dedicated RApreamblesLNCEL; 4 (0), 8 (1), 12 (2), 16 (3), 20(4), 24 (5), 28 (6), 32 (7), 36 (8), 40(9), 44 (10), 48 (11), 52 (12), 56 (13),
60 (14), 64 (15); 1 ; 40 (9)
Remaining are NonContention Based
Dedicated
preambles
Non-Dedicated
preambles
Type A and B Grouping of Preambles
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The contention based Random Access preambles are grouped into:
• Type A - for requesting a normal UL resource.
• Type B - for requesting a larger resource due to Message Size AND Pathloss (PL)
criteria having been met.
raPreGrASizeRandom Access Preambles Group ASizeLNCEL; 4 (0), 8 (1), 12 (2), 16 (3), 20(4), 24 (5), 28 (6), 32 (7), 36 (8), 40(9), 44 (10), 48 (11), 52 (12), 56 (13),60 (14) ; 1 ; 32 (7)
raPreGrASize
raNondedPreambContention Based
64 preamblesper cell
raPreGrASizeType A Preambles
Type BPreambles
Remainingare Type B
raNondedPreamb ?
?
Type B Criteria
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The Type B Random Access preambles are used if:
• The message size is greater than raSmallVolUl.
AND • the pathloss is less than:
PCMAX – preambleInitialReceivedTargetPower - deltaPreambleMsg3 - messagePowerOffsetGroupB
Where:
PCMAX is the UE maximum output power.
raSmallVolUlSmall Size Random Access DataVolume In Uplink
LNCEL; 56 bits (0), 144 bits (1), 208bits (2), 256 bits (3) ;1 ; 144 bits (1)
deltaPreMsg3
Delta Preamble Random AccessMessage 3LNCEL; -1...6 ;1 ; 0
raMsgPoffGrB RA Message Power Offset For Group B SelectionLNCEL; -infinity (0), 0 dB (1), 5 dB (2), 8 dB (3), 10 dB(4), 12 dB (5), 15 dB (6), 18 dB (7) ;1 ; 10 dB (4)
ulpcIniPrePwr
Preamble Initial Received TargetPowerLNCEL; -120 dBm (0), -118 dBm (1), -116 dBm (2), -114 dBm (3), -112 dBm(4), -110 dBm (5), -108 dBm (6), -106dBm (7), -104 dBm (8), -102 dBm (9),-100 dBm (10), -98 dBm (11), -96 dBm(12), -94 dBm (13), -92 dBm (14), -90dBm (15);1 ; -104 dBm (8)
LTE962 - RACH Optimization
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• RACH Optimization feature deals with the
identification and resolution of conflicts and
inconsistencies due to incorrect configuration of
PRACH related parameters or PRACHparameters itself
• Differentiation of PRACH can be done in:
- Time Domain
• [prachConfIndex]
- Frequency Domain
• [prachFreqOff ]
- Code Domain• PRACH cyclic shift [prachCS]
• PRACH Root sequence [rootSeqIndex]
• RL50 gives possibility to configure PRACH related
parameters:
• as a part of eNB auto-configuration process
– for new deployments
• for existing sites by MANUAL triggeringoptimization process
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