Channel Config RA
January 15, 2017 | Author: Sadok Ben ALi | Category: N/A
Short Description
Download Channel Config RA...
Description
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
5
•
Overview
•
DL Channels and Signals
•
UL Channels and Signals
•
Random Access
•
RA Procedure
•
Preamble Generation
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Overview - Channels Upper Layers DL
UL
RLC DCCH
DTCH
CCCH
MTCH
MCCH
DTCH
DCCH
CCCH
PCCH
BCCH
Logical channels
MAC UL-SCH
RACH
MCH
DL-SCH
PCH
BCH
Transport channels
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DRS
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PUSCH
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PUCCH
Air interface
PRACH
PMCH
RS
Synch
PDCCH
PCFICH
PHICH
PDSCH
PBCH
SRS
PHY
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 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
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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
CCCH
DCCH
DTCH
Logical RLC
• 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
Transport
RACH
UL-SCH
• PRACH: Physical Random Access Channel
MAC
• 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 –
PHYS. PRACH
For uplink demodulation and channel estimate
• SRS: Sounding Reference Signal –
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For uplink channel aware scheduling
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PUSCH
PUCCH
Overview – Control Information CQI, PMI, RI, ACK/NACK
CQI, PMI, RI, ACK/NACK SR
eNode B
DL control configuration 1x per cell RNTI DL scheduling
UL Grant UL Power Control n x per cell HARQ Info
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 Carrier Bandwidth [MHz]
Number of PRB
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) 10
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Generic - Carrier Frequency and Bandwidth (FDD)
...
100 kHz
...
FDL = FDL_low + 0.1(NDL – NOffs-DL) FUL = FUL_low + 0.1(NUL – NOffs-UL)
earfcnUL/ earfcnDL
EARFCN
Absolute Radio Frequency Channel Number
NUL : earfcnUL
LNCEL; 0...65535; 1; -
NDL : earfcnDL Bandwidth
earfcnUL = earfcnDL + 18000
UL: ulChBw DL: dlChBw
*Noffs-DL & Noffs-UL specified by TS 36.101 for each band
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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 12
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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 synchronization using primary and secondary sync signal - As a result of cell search the UE should acquire: • PHY cell ID • 10ms and 5ms timing • CP length • Duplex mode (TDD/FDD)
Cell ID Group 0 (3 L1 id’s)
phyCellId: Physical Cell Id LNCEL; 0..503; 1; (Range; Step; Default)
168 Cell ID groups
Cell ID Group i (3 L1 id’s)
Strongest Signal
Primary Synchronization Signal
L1 id, slot (0/10)
Secondary Synchronization Signal Group 167 Phy L Cell ID Physical Layer Cell ID, Frame Alignment
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Generic - Time Structure (Frame Type 1) Radio frame = 10 ms 19
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
0
subframe = 1 ms
Df = 15 kHz, UL/DL - Normal Prefix
Symbol
CP
Symbol
CP
Symbol
CP
Symbol
CP
Symbol
CP
CP Symbol
CP
Slot = 15360 Ts = 500µs
Symbol
144 Ts = 4.69 µs 160 Ts
Df = 15 kHz, UL/DL - Extended Prefix CP Symbol
CP Symbol
CP Symbol
CP Symbol
CP Symbol
CP Symbol
512 Ts = 16.7 µs
Tcp = Ncp Ts Cyclic Prefix x2047-Ncp, … x2047
Symbol Tsym = 2048 Ts = 66.67 µs OFDM Symbol (Time Domain Samples) x0, x1, …, x2047
Df = 7.5 kHz, UL/DL - Extended Prefix CP
Symbol
CP
Symbol
CP
Symbol
1024 Ts = 33.3 µs
7.5kHz Only used for MBMS 14
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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:
Ts: ‘sampling time’ of the overall channel. Basic Time Unit.
5.21 s
Ts =
Long cyclic prefix:
=
16.67 s
= Data
1 sec Subcarrier spacing X max FFT size 1 sec 15kHz X 2048
= Cyclic prefix
Copy
= 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 MTCH
MCCH
DTCH
DCCH
CCCH
PCCH
BCCH
MAC
HI
CFI
DCI
PHICH
PCFICH
PDCCH
MCH
DL-SCH
PCH
BCH
PHY
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RS
Synch
PMCH
PDSCH
PBCH
Air interface
Synch Signals – Time and Frequency Slot id: 0 1 2 . .
..10..
..19 0 1
DTX Secondary Synchronization Signal (SSS) Primary Synchronization Signal (PSS)
180 kHz 0.5 ms 18
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R0
One antenna port
One antenna port
Incremental Time-Frequency Structure of Cell-specific Reference Signals
R0
R0
R0
R0
R0
R0
R0
l0
l6 l0
l=0 ……...... 6, 0 ………..
l6
6
Resource Element (RE) k, l
R0
Two antenna ports
Two antenna ports
Resource element (k,l)
R0
R0
R0
R1
R0
R0
R0
R0
Four antenna ports
Four antenna ports
l=0 ……...... 6, 0 ………..
6
R0
l0
R0
Antenna port 0
odd-numbered slots
l0
even-numbered slots
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R3
R2
R3
R2 l6
odd-numbered slots
Antenna port 1
R3
R2
R1 l6 l0
Antenna port 1
Antenna port 0
R2
R1
R1 l6
6
R1
R1
R0
l6
R1
R1
l6 l0
even-numbered slots
R1 l6 l0
R1
R0
Reference symbols (RS) on this antenna port
Reference symbols on this antenna port
l=0 ……...... 6, 0 ………..
R0
R0
l0
l6
Not used for transmission on this antenna port (DTX)
Not used for transmission on this antenna port
R1
R1
l6 l0
R0
R1
R1
R0
l0
R1
R1
l0
R3 l6 l0
Antenna port 2 even-numbered slots
l6
odd-numbered slots
Antenna port 2
l0
l6 l0
Antenna port 3 even-numbered slots
odd-numbered slots
Antenna port 3
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l6
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 One MIB (information bits + spare bits + CRC)
Code and rate-matching (repetition) to number of bits available on PBCH in 40 ms
Segmentation into four equal sized individually self-decodable units
6 RBs
Used bandwidth
40 ms transmission time interval of PBCH
One radio frame
PBCH
1 RB
Synchronization signals Reserved for reference singals Remark: PBCH does not use blocks reserved for reference signals
One subframe (2 slots) 1 ms
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Physical Layer Downlink DL-Physical Data & Control Channels
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 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 codeword
CFI 1
2
3
4 (reserved)
• Transmitted – – – – – 22
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 RA41213EN60GLA0
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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 *Necessary with semi-persistent scheduling
DL N N g RB 8 group N PHICH DL 2 N N g RB 8
Sequence Index
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Normal CP
Extended CP
0
+1 +1 +1 +1
+1 +1
1
+1 -1 +1 -1
+1 -1
2
+1 +1 -1 -1
+j +j
3
+1 -1 -1 +1
+j -j
4
+j +j +j +j
5
+j -j +j -j
6
+j +j -j -j
7
+j -j -j +j
e.g. 20 MHz
phichRes
phichRes
1/6
1/2
1
2
#PHICH groups LNCEL; 1/6; ½; 1; 2; 1/6
#PHICH groups
3
7
13
25
# scheduled UE
24
56
104
200
for normal cyclic prefix for extended cyclic prefix
Number of RBs
23
Orthogonal sequence
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PHICH Association and Resource Indication PhichDur PHICH on symb. 1 / 1- 3 LNCEL; Normal (0), Extended (1); 1; Normal(0)
- 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
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
pdcchAggDefUE PDCCH 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 25
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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. maxNrSymPdcch eNB selects the actual value for each TTI, which is signaled to UE in PCFICH. LNCEL; 1..3; 1; 3 Range: 1, 2, 3 (BW > 1.4 MHz);
-
Range: 2, 3, 4 (BW = 1.4 MHz)
ActldPdcch
-
setting: maxNrSymPdcch
LNCEL; false, true:false
-
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)
-
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Frequency
Physical Layer Downlink Summary DL-Physical Data & Control Channel
SSS PSS PBCH PCFICH
PHICH PDCCH Reference signals PDSCH UE1 PDSCH UE2 Time 27
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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. 29
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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 to be 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
PRIMARY CELL
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
LNBT S LCELL
LNCEL
sectorId
CAREL lcrId
No more than 2 cells with the same sectorId could be configured
LNCEL Sectorid Cell sector id
sectorId
LNCEL; 0…255; -
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LCELL
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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 – in another 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
LNBTS
PCell
LCELL
LNCEL
sectorI d
CAREL lcrId
LCRID Local cell resource ID of cell to be aggregated CAREL; 0…255; -
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LNCEL
LCELL
lcrId
sectorId
SCell
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:
have secondary cell configured (= added) and
• At maximum 50 others of them can have this cell configured as a secondary one.
Note: This number could be limited by maxNumCaConfUeDc parameter set in PCell (by default equal to 20)
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Cells in Carrier aggregation
• At maximum 50 of them can Max 50 CA
Max 420 Active UEs
SCell UEs
Cell 1
Max 50 CA PCell UEs Cell 1 is SCell of Cell 2 Cell 2 is SCell of Cell 1 Max 50 CA PCell UEs Max 50 CA
Cell 2
Max 420 Active UEs
SCell UEs
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 the sCellActivationMethod parameter:
Configure UE with SCell RRM signaling
SCell configured, not activated nGBR buffer based
•Blind (sCellActivationMethod = BLIND) •Buffer based (sCellActivationMethod = nonGBRBufferBased)
Start calculating activation threshold value
Start periodic activation cycle
LNBTS :nonGBRBufferBased (0), blind (1); - nonGBRBufferBased (0)
Restart timer Compare nGBR buffer against current activation threshold
Scell activated At subframe n+8
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Scell activated
Period activation occassion
sCellActivationMethod SCell activation method
Blind activation
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DL Carrier Aggregation Configure UE with SCell RRM signaling
Buffer based activation of the secondary cell means that every sCellActivationCyclePeriod it is checked whether all non-GBR data awaiting initial transmission 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
Start calculating activation threshold value
SCell configured, not activated nGBR buffer based
Start periodic activation cycle
Blind activation
Scell activated
Period activation occasion
Restart timer
sCellActivationCyclePeriod SCell activation cycle period
Compare nGBR buffer against current activation threshold
LNBTS : 0.5s (0), 1s (1), 2s (2), 4s (3), 8s (4), 16s (5) : 2 Scell activated At subframe n+8 35
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Downlink carrier aggregation - 40 MHz Simplified scenario is shown, with equal split of nGBR data between PCell and SCell
SCell activation: buffered nGBR data exceeds activaton threshold
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 sCellDeactivationTimerEnb ……. nGBR data sent over PCell 36
nGBR data sent over SCell RA41213EN60GLA0
Time (individual TTIs)
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Downlink carrier aggregation - 40 MHz The buffered non-GBR data is divided between PCell and SCell according to nonGBR throughput share achieved in the past
•
The division factor is limited to the range of 10…90% to avoid possible deadlock. Division factor PCell
SCell
0% 10%
•
37
90% 100%
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
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Downlink carrier aggregation - 40 MHz •
Additional cell bandwidth combinations are supported on top of RL50 band combinations:
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BW1
BW2
5 MHz
5 MHz
Supported already in RL50; FSME/FSMF
5 MHz
10 MHz
Supported already in RL50; FSMF
10 MHz
10 MHz
Supported already in RL50; FSME/FSMF
5 MHz
15 MHz
5 MHz
20 MHz
10 MHz
15 MHz
10 MHz
20 MHz
15 MHz
15 MHz
15 MHz
20 MHz
20 MHz
20 MHz
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All these new RL60 combinations are supported by FSMF only
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Downlink carrier aggregation - 40 MHz
All the RL60 combinations are supported by FSMF only
Support for additional band combinations are provided in RL60 on top of RL50:
RL50
Band A
39
Band B
Band A
Band B
Band 1
2100
Band 5
850
Band 3
1800
Band 3
1800
Band 1
2100
Band 8
900
Band 3
1800
Band 7
2600
Band 3
1800
Band 5
850
Band 3
1800
Band 20
800
Band 3
1800
Band 8
900
Band 4
AWS
Band 4
AWS
Band 5
850
Band 12
US 700
Band 4
AWS
Band 17
700
Band 1
2100
Band 18
800 Lower
Band 5
850
Band 7
2600
Band 1
2100
Band 7
2600
Band 7
2600
Band 20
800
Band 2
1900 PCS
Band 4
AWS
Band 4
AWS
Band 12
Lower 700
Band 2
1900 PCS
Band 5
850
Band 3
1800
Band 28
700
Band 2
1900 PCS
Band 17
700
Band 4
AWS
Band 7
2600
Band 7
2600
Band 7
2600
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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:
contiguous intra-band allocation of CA component carriers
•
non-contiguous intra-band allocation of CA component carriers
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.
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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
DCCH
DTCH
CCCH
RLC
RACH
UCI
UL-SCH
MAC
PRACH
PUCCH
SRS
DRS
PUSCH
PHY
Air interface
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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 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:
(1) eNodeB transmission
• CQI - Channel Quality Indicator • RI - Rank Indicator • PMI - Precoding Matrix Indicator
(2) UE CSI measurement (3) UE feedback
- 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)
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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%
UE reports highest MCS that it can decode with a TB Error rate < 10% taking into account UE’s receiver characteristic
CQI index
modulatio n
0
coding rate x 1024 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
* Efficiency is defined as number of bits per resource elements 44
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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
riEnable Determines 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 46
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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 cqiPerNp CQI periodicity LNCEL; 2; 5; 10; 20; 20 ms
CQIAperEnable
enabling / disabling aperiodic CQI /RI/PMI reporting on PUSCH. LNCEL; false/true; true
Periodic reporting
Aperiodic Reporting
• The baseline mode for CQI/PMI/RI
• Aperiodic reports are explicitly triggered by the eNodeB using a specific bit in the PDCCH UL grant
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 48
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• Aperiodic report can be either piggybacked with data or sent alone on PUSCH • Possibility for large and detailed reports (up to more than 64 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
© Nokia Solutions and Networks 2014
Categorization of CQI/PMI/rank reporting options cqiAperMode Aperiodic CQI feedback mode
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
LNCEL; FBT1(0) – Family modes 2-x, FBT2(1)- Family modes 3-x (x defined by MIMO algorithm internal in eNodeB); FBT2 (1) Single or Multi-PMI = closed loop MIMO with PMI feedback No PMI = Single antenna, TxDiv or OL MIMO
LTE CQI reporting family tree
Aperiodic
Periodic
Wideband
Frequency selective
No PMI
Single PMI
No PMI
Single PMI
Mode 1-0
Mode 1-1
Mode 2-0
Mode 2-1
4 bits
11 bits
6 bits
11 bits
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Single CQI
Best-M Average
Full Feedback
Multi PMI
No PMI
Multi-PMI
No PMI
Single PMI
1-2
Mode 2-0
Mode 2-2
Mode 3-0
Mode 3-1
60 bits
24 bits
38 bits
30 bits
64 bits
©*See Nokia Solutions TS 36.213and Networks 2014
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 M = 3 best Subbands are selected and an average CQI value is reported
An example of Best-M Average reporting with 3 MHz BW (15 RBs means that the subband size is 2 RBs and the best 3 subbands are reported)
Subband index PRB index
BW / RB
Subband size (RBs)
# best Subbands M
6-7
NA
NA
8-10
2
1
11-26
2
3
27-63
3
5
64-110
4
6
Channel SINR
1 1
2
2 3
4
3 5
6
4 7
8
5 9 10
6 11 12
7 13 14
8 15
- Full Feedback also called Higher Layer Configured sub-band feedback • A separate CQI is reported for each sub-band using Delta compression 50
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CQI Periodic Reporting on PUCCH or PUSCH - Wideband feedback or UE selected sub-band
- Period configurable
cqiPerNp
• 2, 5, 10, 20ms
CQI periodicity
LNCEL; 2; 5; 10; 20; 20 ms
- 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.* BW / RB Subband - Configured by higher layer signaling * 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
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BW Parts (J)
Size k (RBs) 6-7
NA
NA
8-10
4
1
11-26
4
2
27-63
6
3
64-110
8
4
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Uplink Control Signaling: PUCCH vs. PUSCH
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
•PUCCH (Physical Uplink Control Channel) • Used when the UE is not sending data • PUSCH (Physical Uplink Shared Channel) simultaneously – Used when the UE transmits also data • Shared frequency and time resource – UE-specific resource that can be used reserved exclusively for the UEs for L1/L2 control signaling (based on transmitting only L1/L2 control signals scheduling decisions made by Node B) • Optimized for large number of simultaneous UEs with relatively small – Capable to transmit control signals with number of control signaling bits per UE large range of supported control sizes (1…11) (1… 64 bits) • Very high multiplexing capacity, spectral – TDM between control and data efficiency e.g. (multiplexing is made prior DFT) - 18 UEs/RB transmitting ACK/NACK (PUCCH Format 1a/1b) - 6 UEs/RB transmitting 11-bit CQI + 2bit A/N (PUCCH Format 2b)
*TDM = Time Domain Multiplexing
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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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UL Reference Signal Overview UL DM RS allocation per slot for Normal Cyclic Prefix
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
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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 neighboring cells
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
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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, 1b
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PUCCH Formats 2, 2a, 2b
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SRS
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
Each group contains
• •
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1 sequence of lengths 12, 24, 36, 48 and 60 2 sequences of lengths 72, 84, 96, … 1200
Group hopping for UL reference signal Group Allocation •
The allocated group for a cell is not planned explicitly but is calculated from:
u f gh ( ns ) f ss mod 30
Group
PCI PUCCH & SRS
0 fgh (ns )
i 0 c(8ns i) 2i mod 30 7
if group hopping is disabled
cell f ssPUCCH N ID mod 30
if group hopping is enabled
PUSCH
f ssPUSCH f ssPUCCH D ss mod 30 Psuedo random sequence initialized using ROUNDDOWN [PCI / 30]
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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
Resource block
* FDM = Frequency Division Multiplexing
system bandwidth
PUCCH
CDM = 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
deltaPucchShift delta cyclic shift for PUCCH formats 1/1a/1b LNCEL; 1..3; 1; 2 (i.e. 6 cyclic shifts)
• 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 SF = 3 for Reference Signals and SF = 4 for ACK/NACK SF = Spreading Factor
Cyclic shift
SF=4 SF=3 RS
RS
CDM in CS domain
RS
slot
*CDM = Code Division Multiplexing
block-wise spreading
0 1 2 3 4 5 6 7 8 9 10 11
Orthogonal cover code 0 1 0 6 1 7 2 8 3 9 4 10 5 11
* The applied sequences are not true CAZAC but computer searched Zero-Autocorrelation (ZAC) sequences
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2 12 13 14 15 16 17
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 PUCCH Format 1 PUCCH Format 1a PUCCH Format 1b PUCCH Format 2 PUCCH Format 2a PUCCH Format 2b
Control type Scheduling request 1-bit ACK/NACK 2-bit ACK/NACK CQI CQI + 1-bit ACK/NACK CQI + 2-bit ACK/NACK
Number of Bits ON/OFF keying 1 2 20 21 22
Multiplexing Capacity (UE/RB) 36, *18, 12 36, *18, 12 36, *18, 12 12, *6, 4 12,* 6, 4 12, *6, 4
*typical value
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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 = 0 & 1 may contain formats 2/2a or 2b (e.g. CQI) -> fixed allocation m = 2 & 3 may contain
m=1 m=3
m=0 m=2
system bandwidth
PUCCH
formats 1/1a or 1b (e.g. ACK) -> dynamic allocation
m=2 m=0
m=3 m=1
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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
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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 mixed formats )
deltaPucchShift delta cyclic shift for PUCCH formats 1/1a/1b LNCEL; 1..3; 1; 2
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
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Flexible Uplink Bandwidth 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 •Achieved by increasing the bandwidth allocated to PUCCH, 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
WCDMA 5MHz
LTE 5 MHz
Deployment possible with narrower spacing
blankedPucch Blanked PUCCH resources): LNCEL; 0..60; 1; 0 0 1 2 3 4 5 6 7 8 9 1011 1213141516171819202122232425262728293031323334353637383940414243444546474849
Blanked area
PUCCH area
PUSCH resources
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
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Example configuration (uplink bandwidth 10 MHz, 50PRBs) No PUCCH blanking
PUCCH Format 1.x area
ulChBw = 10 MHz
Frequency (PRBs)
0 1 2 3 4 5 6 7 8 9 1011 1213141516171819202122232425262728293031323334353637383940414243444546474849 0 2 4 6 8 1 3 5 7 9
Total PUCCH area: 2x5PRB
nCqiRb =4
9 7 5 3 1
Total PUSCH area: 40 PRBs
8 6 4 2 0
With PUCCH blanking
Area reserved with nCqiRb
nCqiRb = 20
blankedPucch = 16
PUCCH Format 2.x allocations starting from PUCCH allocation region 16 (PRB #8)
Actual blanked area: 2x8PRB
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
Total PUSCH area: 24 PRBs
0 2 4 6 8 10 12 14 16 18 20 22 24 1 3 5 7 9
11 13 15 17 19 21 23 25
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25 23 21 19 17 15 13 11 9 7 5 3 1
24 22 20 18 16 14 12 10 8 6 4 2 0
Total PUCCH area: 2x5PRB
© Nokia Solutions and Networks 2014
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. 5 MHz + 10 MHz
downlink
uplink
Combined capacity: 100Mbps (32+68)
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20 MHz + PUSCH blanking
downlink
uplink
Capacity: 142Mbps
© Nokia Solutions and Networks 2014
PUSCH masking
Each zone is determined by two parameters:
First PRB that will be muted
ulsPuschMaskStart LNCEL : Range: [0..99] (*) Default: no (*) actual values depend on ulChBw
These uplink resources will never be allocated
11 PRBs
Length of the muted zone ulsPuschMaskLength LNCEL: Range: [1..100] (*) Default: no (*) actual values depend on ulChBw
ulsPuschMaskStart =13 ulsPuschMaskLength = 11
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11 PRBs muted: [#13 .. #23]
Sounding Reference Signal UE scheduling & SRS Configuration 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 specific channel state information (CSI) is derived from: - PUSCH - sounding reference signals (SRS)
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SRS Configuration - The operator can choose an SRS configuration from a given set of predefined configurations tailored for the usable PUSCH spectrum - srsConfiguration - 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).
……
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SRS Bandwidths Wideband SRS Transmission
Narrowband SRS Transmission
(Non Frequency hopping SRS )
(Frequency hopping SRS )
Subframe 1
Subframe 6 Subframe 1
System bandwidths 40–60 RBs.
Subframe 2
More
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
16 RBs
wideband SRS bandwidth = 4 RBs × 3
= 12 RBs
Minimum Narrow
Sounding reference signal
SRS bandwidth
= 4 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. 71
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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 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
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PRACH
UE sends the preamble to the network on PRACH: • PRACH occupies 6 resource blocks (of 180 kHz) in a 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 channel structure for preamble format type 0
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PRACH Types
PRACH types:
• Type 0: 1 ms duration • Type 1: 2 ms • Type 2: 2 ms • Type 3: 3 ms
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PRACH Configuration Type, time resources are defined by: PRACH configuration index: prachConfIndex LNCEL; 3..24;1; 3 Range is restricted to two different ranges: 3-8 and 19-24 (internal)
.
*3GPP TS 36.211 Table 5.7.1-2 76
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PRACH 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: RA UL 0 nPRBoffset NRB 6
... If PRACH area is placed at the lower border of UL frequency band then:
PRACH PUCCH
prachFreqOffset = roundup [maxPucchResourceSize /2] If PRACH area is placed at the upper border of the UL frequency band then:
prachFreqOffset = MAXNRB – 6 - roundup [maxPucchResourceSize /2]
freq
freq
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
.. .
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tim e
Module Contents •
Overview
•
DL Channels and Signals
•
UL Channels and Signals
•
Random Access
• RA Procedure • Preamble Generation
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RA Procedure - Random access procedure handled by MAC and PHY Layer through PRACH (in UL) and PDCCH ( 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 ) PRACH response
Not detected DL
On the resources indicated by PDCCH
Next PRACH resource UL
PUSCH: UE specific data Preamble
Preamble
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
The contention based random access procedure follows these steps: (1)
(2)
(3)
(4)
A preamble will be selected by UE and transmitted in the available subframe. Based on correlation the eNB may detect the access and furthermore can measure the timing of the UE transmission. The eNB answers using the same preamble and at this point a timing advance will be fixed. Information on the scheduled resource will be exchanged and a temporary C-RNTI will be assigned.
raRespWinSize
Window size for RA response (in TTI) LNCEL; 2 (0), 3 (1), 4 (2), 5 (3), 6 (4), 7 (5), 8 (6), 10 (7); 10 TTIs (7) UE
1
The UE sends its id. The type of id depends on the state. In case of idle state NAS info has to be provided (IMSI, TMSI) else the C-RNTI is used. The contention resolution is performed, i.e. the eNB addresses the UE using the C-RNTI.
eNB
Random Access Preamble
Random Access Response
3
Scheduled Transmission
Contention Resolution
ulpcRarespTpc TPC command indicated in message 2 related to message 3 power LNCEL; -6...8dB;2dB; 4dB
raContResoT Max. Time for cont. resol. LNCEL; 8ms (0), 16ms (1), 24ms (2), 32ms (3), 40ms (4), 48ms (5), 56ms (6), 64ms (7); 64ms (7)
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4
RA Procedure
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. UE
0
eNB
RA Preamble assignment
Random Access Preamble
2
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Random Access Response
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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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Preamble generation # root sequences = 838 in total # preamble sequences = 64 per cell
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
Fig: example of preambles generation with zero autocorrelation zone length equal to 279 (prachCS=14)
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Fig: Zadoff-Chu sequence. The real (upper) and imaginary (lower) parts of the complexvalued output (Wikipedia)
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Preamble generation 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 preamble premable formats
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Preamble Generation 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
xu n e
j
un ( n1) N ZC
, 0 n N ZC 1
xu ,v (n) xu ((n Cv ) mod N ZC )
• ZC sequence of length 839 (prime number) is used • 838 different root sequences available. (PRACH Root Sequence). Also different cyclic shifts can be used depending on cell size • Sub-carrier spacing is 1.25 kHz
rootSeqIndex LNCEL;0…837;1; 0
*3GPP TS 36.211 Table 5.7.2-4
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Preamble Generation
Root Zadoff-Chu sequence order for preamble formats 0 – 3.:
First: take all available cyclic shifts of one root Zadoff-Chu sequence: If not enough: take next logical index and so on prachCS Preamble cyclic shift (Ncs configuration) LNCEL;0…15;1; 0
prachHSFlag
Unrestricted or restricted (high speed) set selection LNCEL; true, false; false
• Cyclic shift given by
vN CS Cv 0 RA RA v nshift (v mod nshift d ) N CS start
v 0,1,..., N ZC N CS 1, N CS 0 for unrestricted sets N CS 0 for unrestricted sets RA RA RA for restricted sets v 0,1,..., nshift ngroup nshift 1
*3GPP TS 36.211 Table 5.7.2-2
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Preamble generation
-Exercise Consider a cell of 37 km radius. Provide a sensitive setting for the cell size dependent parameters
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Support of high speed users •
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If prachHsFlag = true the following rootSeqIndex values can be selected depending on prachCS (restricted set) Cell range
Required amount of root 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
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Preamble generation – High Speed Case 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
highspeed set no delay spread
With preamble delay spread = 5,2 µs guard
NCs Configuration NCS
sign. per root seq.
#root seq. µs
km
µs
km
Guard
NCS
µs
km
µs
km
0 1 2 3 4 5 6 7 8 9 10 11 12 13
15 18 22 26 32 38 46 55 68 82 100 128 158 202
18 15 12 10 8 7 6 4 4 3 2 2 1 1
4 6 6 8 9 11 14 17 20 26 32 44 64 64
14.3 17.2 21.0 24.8 30.5 36.2 43.9 52.4 64.8 78.2 95.4 122.1 150.7 192.6
2.15 2.57 3.15 3.72 4.58 5.44 6.58 7.87 9.73 11.73 14.30 18.31 22.60 28.89
9.1 12.0 15.8 19.6 25.3 31.0 38.7 47.2 59.6 73.0 90.2 116.9 145.5 187.4
1.37 1.79 2.37 2.94 3.80 4.66 5.80 7.09 8.95 10.95 13.52 17.53 21.82 28.11
2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25
12.75 15.75 19.75 23.75 29.75 35.75 43.75 52.75 65.75 79.75 97.75 125.75 155.75 199.75
12.2 15.0 18.8 22.6 28.4 34.1 41.7 50.3 62.7 76.0 93.2 119.9 148.5 190.5
1.82 2.25 2.82 3.40 4.26 5.11 6.26 7.54 9.40 11.41 13.98 17.99 22.28 28.57
7.0 9.8 13.6 17.4 23.2 28.9 36.5 45.1 57.5 70.8 88.0 114.7 143.3 185.3
1.04 1.47 2.04 2.62 3.48 4.33 5.48 6.76 8.62 10.63 13.20 17.21 21.50 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
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Preambles - Contention and Non-Contention
64 preambles per cell raNondedPreamb Total number of non dedicated RA preambles LNCEL; 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)
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Remaining are Non Contention Based Contention Based
Non Contention Based
Non-Dedicated preambles
Dedicated preambles
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Type A and B Grouping of Preambles 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.
raPreGrASize raNondedPreamb
? ?
64 preambles per cell
raNondedPreamb Contention Based raPreGrASize Random Access Preambles Group A Size LNCEL; 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)
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Remaining are Type B raPreGrASize Type A Preambles
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Type B Preambles
Type B Criteria The Type B Random Access preambles are used if: • The message size is greater than raSmallVolUl. AND • the pathloss is less than:
raSmallVolUl Small Size Random Access Data Volume In Uplink LNCEL; 56 bits (0), 144 bits (1), 208 bits (2), 256 bits (3) ;1 ; 144 bits (1)
PCMAX – preambleInitialReceivedTargetPower - deltaPreambleMsg3 - messagePowerOffsetGroupB Where: PCMAX is the UE maximum output power. ulpcIniPrePwr Preamble Initial Received Target Power LNCEL; -120 dBm (0), -118 dBm (1), 116 dBm (2), -114 dBm (3), -112 dBm (4), -110 dBm (5), -108 dBm (6), -106 dBm (7), -104 dBm (8), -102 dBm (9), -100 dBm (10), -98 dBm (11), -96 dBm (12), -94 dBm (13), -92 dBm (14), -90 dBm (15);1 ; -104 dBm (8)
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deltaPreMsg3 Delta Preamble Random Access Message 3 LNCEL; -1...6 ;1 ; 0
raMsgPoffGrB RA Message Power Offset For Group B Selection LNCEL; -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)
© Nokia Solutions and Networks 2014
LTE962 - RACH Optimization •
RACH Optimization feature deals with the identification and resolution of conflicts and inconsistencies due to incorrect configuration of PRACH related parameters or PRACH parameters 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 triggering optimization process
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