ZTE LTE Random Access
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Transcript of ZTE LTE Random Access
Random Access Special Topic
ZTE University
Objects
After the course,you will: Know the details of channel and channel mapping Understand UE power on procedure Master UE random access procedure Master UE initial attach procedure
Content
LTE channel introduction and channel mapping
UE power on procedure
UE random access procedure
Random access special scenarios application
UE attach signalling flow
LTE physical channel introduction
LTE downlink physical channel Broadcast channel : PBCH Control channel : PCFICH , PHICH , PDCCH Service channel : PDSCH MBMS channel : PMCH
LTE uplink physical channel Control channel : PUCCH Service channel : PUSCH Random access channel : PRACH
Downlink physical channel PBCH ( Physical Broadcast Channel )
BCCH includes MIB and SIB , MIB is mapping on PBCH,SIB is mapping on PDSCH.
PBCH is in the first 4 OFDM symbols of subframe 0 1 time slot on time domain, and 6 central RBs on frequecydomain,modulation is QPSK.
MIB includes downlink system bandwidth, system frame number (SFN), PHICH duration.
Physical resource mapping on each antenna
port
OFDM modulation
OFDM modulation
OFDM modulation
An 1
An 0
An P
Cell interference enhancing
Modulation mapping
Layer mapping
Pre-programming
BCH TB
CRC adding
Signal program-
ming
Rate matching
Downlink physical channel
Control Channel : PCFICH PCFICH : Physical Control Format Indicator Channel PCFICH are transmitted in each sub-frame, informing
UE of the OFDM symbols that PDCCH occupies in a sub-frame. The OFDM symbols are indicated by CFI which can be valued as 1, 2, 3, 4 (4 is reserved).
Modulation is QPSK。 PCFICH is mapped to the four resource-element groups
in the first OFDM symbol in a downlink subframe.
Signal program-
ming
Interference enhancing
Modulation mapping
Layer mapping
Pre-programming
RE mapping
OFDM symbol generating
CFI
Downlink physical channel
Control channel: PHICH PHICH: Physical Hybrid-ARQ Indicator Channel Send NAK/ACK responding information for the
PHICH , modulation is BPSK. Multiple PHICH can be sent in a group at the same time.
1 PHICH group=8 PHICHs (normal cp) 1 PHICH group=4 PHICHs (extend cp)
Repetition(RF=3)
ModulationLayer
MappingPrecoding RE mapping
OFDM modulation
Spreading & scrambling
ACK/NACK
Downlink physical channel
Control channel: PDCCH PDCCH: Physical Downlink Control Channel PDCCH sends scheduling information, transmission format,
resource allocation, uplink scheduling permission, power control and uplink-transmission-related ACK/NACK.
PDCCH is mapped to the first n (n<=4) OFDM symbols in each sub-frame. The value of n is indicated by CFI in the PCFICH channel.
PDCCH supports 4 types of physical-layer formats which occupy one, two, four, and eight CCEs respectively.
Downlink physical channel
Service Channel: PDSCH PDSCH: Physical Downlink Shared Channel PDSCH Bears service data, L3 signalling message,
paging and SIB information. Modulation: QPSK, 16QAM, 64QAM.
Downlink physical channel
MBMS Channel: PMCH Physical Multicast Channel (PMCH) If MBMS is support, MBMS sends cell MBMS broadcast
information. Modulation:QPSK, 16QAM, 64QAM。
Downlink channel mapping
BCCH PCCH CCCH DCCH DTCH MCCH MTCH
PCH DL-SCH MCHBCH
PBCH PDSCH PMCH
Logical channel
Transmission channel
Physical channel
PDCCH
Uplink physical channel Control Channel : PUCCH
PUCCH: Physical Uplink Control Channel PUCCH periodically feed back different CQI, PMI, RI,
HARQ-ACK 、 SR. For the same UE, PUCCH does not transmit with PUSCH. PUCCH format:
PUCCH format
Content Modylation Size1 SR N/A N/A1a ACK/NACK BPSK 11b ACK/NACK QPSK 22 CQI QPSK 202a CQI+ACK/NACK QPSK+BPSK 212b CQI+ACK/NACK QPSK+BPSK 22
Uplink physical channel
Service Channel: PUSCH PUSCH : Physical Uplink Shared Channel PUSCH Bears service data, L3 signalling message Modulation: QPSK, 16QAM, 64QAM. Localized resource allocation for PUSCH, consecutive
RBs are allocated to user’s PUSCH.
Uplink physical channel
PRACH: Physical Random Access Channel During the random access procedure, UE send preamble
on PRACH. PRACH occupies 6 RBs on frequency domain. PRACH time domain structure:
Preamble: CP + Sequence There is a guarding interval behind Preamble.
PreambleCP
CPT PRET
6RB
Uplink physical channel
PRACH Preamble generated by the Zadoff-Chu sequence in
zero-related region.
5 different preamble format:
10, ZC
)1(
ZC
Nnenx N
nunj
u
Uplink physical channel PRACH time damain format
Uplink physical channel PRACH
Format0~3 frequency domain location Subcarrier interval is 1.25KHz, 1/12 of normal subcarrier
bandwidth. 1 PRACH include 864 subcarrier (6×12×12=864). The length of preamble sequences is 839, mapped on the central
839 subcarrirs.83
9 su
bcar
rier
s
864
subc
arri
ers
12subcarriers
13 subcarriers
Uplink physical channel PRACH
Format4 frequency domain location Subcarrier interval 7.5KHz , half of normal subcarrier bandwidth. 1 PRACH include 144 subcarrier (6×12×2=144) . The length of preamble sequences is 139, mapped on the central
139 subcarrirs.
139
subc
arri
ers
144
subc
arri
ers
2subcarriers
3 subcarriers
Uplink channel mapping
CCCH DCCH DTCH
UL-SCH
PRACH PUSCH
RACH
PUCCH
Logical channel
Transmission channel
Physical channel
Physical layer signals
Downlink Physical Signal Reference Signal
Cell-Specific Reference Signal (CRS) MBSFN Reference Signal UE-Specific RS/Dedicate RS(DRS)
Synchronization Signal PSS : Primary Synchronization signal SSS : Secondary Synchronization signal
Uplink Physical Signal Demodulation RS(DMRS) Sounding RS(SRS)
Downlink physical layer signals
Function of downlink reference signal Downlink channel quality measurement Downlink channel estimate, for UE to demodulate data Downlink synchronization
Function of cell-specific reference signal Cell-specific reference signals shall be transmitted in all
downlink subframes in a cell supporting PDSCH transmission.
Cell-specific reference signals are transmitted on one or several of antenna ports 0 to 3.
Cell-specific reference signals are defined for subcarrier interval is 15kHz only.
Downlink physical layer signal
Cell-Specific Reference Signal The RS location has the relation with PCI, antenna port
number, OFDM symbol sequence, slot number, CP mode,etc.
Normal CP , Cell ID=0时Normal CP , Cell ID=0时
Extend CP , Cell ID=0时Extend CP , Cell ID=0时
Downlink physical layer signal MBSFN Reference Signal
Transmitted only when the PMCH is transmitted. MBSFN reference signals are transmitted on antenna port 4.
Defined for extended cyclic prefix only.
0l 5l 0l 5l
even-numbered slots odd-numbered slots
Antenna port 4
4R
4R
4R
4R
4R
4R
4R
4R
4R
4R
4R
4R
4R
4R
4R
4R
4R
4R
0l 2l 0l 2leven-numbered
slots
Antenna port 4
4R
4R
4R
4R
4R
4R
4R
4R
4R
odd-numberedslots
4R
4R
4R
4R
4R
4R
4R
4R
4R
Extended CP Δf=15kHzExtended CP Δf=7.5kHzExtended CP Δf=7.5kHz
Downlink physical layer signals UE-Specific Reference Signal
Send to a dedicated user, the eNodeB will indicate sending this signal or not, and indicate UE to demodulate use the signal or not.
Only transmitted on the RBs bearing PDSCH, using the antenna port 5.
0l
even-numbered slots odd-numbered slots
Antenna port 5
5R
5R
5R
5R
5R
5R
5R
5R
5R
5R
5R
5R
0l 6l6l 0l
even-numbered slots odd-numbered slots
Antenna port 5
5R
5R
0l 5l5l
5R
5R
5R
5R
5R
5R
5R
5R
5R
5R
Normal CP 15kHz Extend CP 15kHz
Downlink synchronization signals
LTE Synchronization Signal PSS : Primary Synchronization Signal SSS : Secondary Synchronization Signal
Function of Synchronization Signal Get Physical Cell ID
Dectect SSS to get PCI group number(0-167) Dectect PSS to get ID in group(0-2) PCI=3*group number+ID in group
Downlink synchronization PSS: 5ms synchronization SSS: 10ms synchronization
Identify it is a FDD or TDD system and CP mode.
Downlink synchronization signals
SCH includes P_SCH and S_SCH. The frequency-domain is located in the 72 subcarriers near direct current. Only 62 subcarriers are actually occupied. Other 10 subcarriers do not hold synchronization sequences.
There are two same P-SCHs in a wireless frame. Their time-domain is located in the last symbol of the slot no.0 and the last symbol of the slot no. 10.
There are also two S-SCHs in a wireless frame. But their synchronization symbols are different. The time-domain is located in the last symbol but one of the slot no.0, and the last symbol but one of the slot no. 10.
125 xx
Downlink synchronization signals
Slot 0 / Slot 10
Nc
subc
arri
ers
72 s
ubca
rrie
rs
Slot 1 / Slot 11
Control signalData
SSS
PSS
Slot 0 / Slot 10
Nc
subc
arri
ers
72 s
ubca
rrie
rs
Slot 1 / Slot 11
Control signaldata
SSS
PSS
DwPTS
FS1, Normal CP
FS2, Extend CP
Uplink physical layer signal
DMRS( for PUSCH) Generated by Zad-off Chu
seqence,maping on RE without any proceess.
Transmitted on 4th OFDM symbol of each slot, the bandwidth of DMRS is same with PRB for PUSCH.
Differerent users’ DMRS sequence will have different cyclic shift.
PUS
CH
Data
One Slot
DMRS
Normal CP
Uplink physical layer signal
Sounding RS: SRS Used for uplink channel quality estimate and selection, uplink
scheduling. Location: last SC-FDMA symbol of uplink subframe which configured
to send SRS, for UpPTS all the symbols can be used to transmit SRS. SRS sub-frame configuration: UE read the broadcast information to
get which subframe will send SRS. Duration: eNodeB will notice UE to send SRS once or all the time. Period: eNodeB will notice SRS transmiting period, it can support
2 、 5 、 10 、 20 、 40 、 80 、 160ms
FDD Downlink Channel Location
SSCH
PDCCH #0 #1 #3 #4 #5 #6 #7 #8 #9
PSCH PBCH PSCH
SSCH
#2 One subf rame(1ms)
PCFICH
PHICH
PDCCHPBCHP- SCH
S- SCH
PDSCH
Second sl ot(0.5ms)Fi rst sl ot(0.5ms)
FDD Downlink Channel Location
PBCH
SSCH
PDCCH CFI=3
PDSCH
CRS:Port 0-3
PSCH
0l
even-numbered slots odd-numbered slots
0l 6l6l
CFI
0l
even-numbered slots odd-numbered slots
0l 6l6l
CFI
TDD FDD
TDD Downlink Channel Location
Content
LTE channel introduction and channel mapping
UE power on procedure
UE random access procedure
Random access special scenarios application
UE attach signalling flow
Uplink initial synchronization:
UE sends preamble on PRACH
eNodeB detects preamble,
sends timing adjustment to UE.
UE adjusts the sending time
according to the timing
adjustment.
Uplink synchronization holding:
eNodeB detects the uplink
reference signal, generates the
time adjustment send to UE.
UE receives TA information and
adjusts the uplink sending time
to hold uplink synchronization.
Downlink initial synchronization:
UE searches cell, detects the
PSS and SSS to get the
downlink initial synchronization.
Downlink synchronization holding:
After cell search, UE measures
the downlink signal arrival time
periodically, adjusts the
downlink initial synchronization.
LTE Physical Layer Procedure: Synchronization
UE Power on Procedure
Power on
Cell Search
DecodingPBCH
DecodingPCFICH
Blind-DetPDCCH
DecodingPDSCH
UL Sync
LinkSetup
(format 1C) (D-BCH) RACH
UE Power on Procedure
PLMN selection and cell selection P-SCH 、 S-SCH and PBCH has the same width and
position for all system bandwidth options. So UE can do the cell search without kowning the system bandwith.
P-SCH, S-SCH and PBCH has the same width and position for all system bandwidth options
1.4 MHz
3 MHz
5 MHz
10 MHz
15 MHz
20 MHz
UE Power on Procedure
PLMN selection and cell selection
PLMN Selection
Location Registration
PLMNs available
PLMNselected
Location Registration response
Registration Area
changes
Indication to user
Manual Mode Automatic mode
Service requests
NAS Control
Radio measurements
Cell Selection and Reselection
UE Power on Procedure
PLMN selection UE scan the whole channel in the band according to its
frequecy capability to find a available PLMN. UE will search the cell with the strongest signal, and then read the cell broadcast information to get the PLMN. If UE read one or more than PLMN in one cell, UE will report all the PLMN as the high quality PLMN whose signal strength satisfy a dedicated threshold to the NAS layer. If UE can read PLMN ID, but the signal strength doesn’t satisfy a dedicated threshold, UE also will report PLMN to NAS layer with the measurment value.
PLMN selection result is given by NAS layer. After selecting PLMN, UE will select serving cell.
UE Power on Procedure
Cell search purpose Detect the Physical Cell-ID Get the downlink time and frequency synchronization Detect CP format : normal or extended format Detect eNodeB antenna port number Read PBCH (Master Information Block)
Get system bandwidth, system frame number (SFN), PHICH duration
UE Power on Procedure
Cell search type: Initial and Stored Information Cell Selection Initial Cell Selection: According to its capability, UE scan
the whole channel in the band and find the best serving cell on each carrier, if UE find, it wil select the cell as the serving cell.
Stored Information Cell Selection: UE select the cell according to the pre-stored cell frequency information.If UE finds a proper cell, it will select this one as the serving cell, or UE will initiate Initial Cell Selection.
UE Power on Procedure
Cell search
One subf rame(1ms)PCFICH
PHICH
PDCCHPBCHP-SCH
S-SCH
PDSCH
Second sl ot(0.5ms)Fi rst sl ot(0.5ms)
Start
End
Symbol timing, frequency shift estimating, sector ID
identifying
Frame synchronizing, cell group ID identifying, CP-
type blind detecting
RS identifying, cell identifying, antenna
configuration identifying
UE read the broadcast information
The main information block (MIB) contains a limited number of the most important and most common transmission parameters. It needs to obtain other information from this cell.
The SIB1 contains the scheduling information of other SIBs and relevant information of other cells.
The SystemInformation (SI) contains the carried SIB rather than the SystemInformationBlockType1.
The SIB2 contains all the configuration information of UE common radio resources.
The SIB3 contains the intra-frequency, inter-frequency or inter-RAT cell reselection information.
The SIB4 contains the information that is related to neighbor cells and only used for intra-frequency cell reselection, cell reselection parameters, and the cell blacklist.
The SIB5 contains the information of the inter-frequency E-UTRA network reselection.
The SIB6 contains the information of the inter-frequency UTRA network reselection.
The SIB7 contains the information of the inter-frequency GERAN (GSM/EDGE) network reselection.
The SIB8 contains the information of the inter-frequency CDMA2000 network reselection.
The SIB9 contains the name of the home eNodeB.
The SIB10 contains the ETWS primary notification information.
The SIB11 contains the ETWS auxiliary notification information.
The SIB12 contains the CMAS auxiliary notification information.
Content
LTE channel introduction and channel mapping
UE power on procedure
UE random access procedure
Random access special scenarios application
UE attach signalling flow
UE Random Access Procedure Random access characteristic
Exists in both TD-LTE and FDD-LTE. No relation with the scale of cell. Divided into competitive and non- competitive random
access. purpose of random access
During attach procedure UE status changed from idle to connected. During handover procedure Get/ recover uplink synchronization Request UE ID from eNodeB Request uplink resoure from eNodeB
UE Random Access Procedure
Random access process can be used in the following situations: Access at RRC_IDLE status Access when the wireless link fault occurs Access in changeover Access at RRC_Connected status
When there are downlink data (eg. The uplink is at non-synchronization status.)
When there are uplink data (eg. The uplink is at non-synchronization status or no PUCCH resource can be used for scheduling request.)
UE Random Access Procedure
Random access categories: Random access based on competitiveness
Used in the five mentioned situations UE selects a preamble sequence randomly in the available
preamble set in a competitive way. Possible collision: two UEs use the same preamble sequence. Perform the synchronization process through four steps. The
fourth step is used to solve the collision. Random access based on non-competitiveness
In handover or when the downlink data arrives The eNB allocates a preamble sequence. Perform the synchronization through three steps without solving
the collision.
UE Random Access Procedure
Preamble categories: Preamble ID number : depend on configuration,maxmum
64 ( 0~63)
Preamble A: 0~59 Preamble B: 4~59 Dedicated Preamble(remaining ID)
PRACH frequency domain location:
First RB Number is congiured by L3 on OMC.
60 ULRB NnRA
PRBoffset
UE Random Access Procedure
Random Access Based on CompetitivenessUE eNB
Random Access Preamble1
Random Access Response 2
Scheduled Transmission3
Contention Resolution 4
UE Random Access Procedure
MSG1 : send preamble sequence on PRACH According to root sequence number, cyclic shift and
preamble formats , UE generates the preamble sequence. Select preamble in group A/B randomly according to the
MSG3 size and pathloss information, then send the preamble on PRACH.
According to the target PRACH received power, preamble formats in BCCH and transmitting counter, UE caculates the PRACH initial emission power.
eNB : according to the received preamble measurement, estimates the distance between UE and eNB,generates the timing ajdustment.
UE Random Access Procedure
MSG2 : Random Access Response eNB Send RAR on the PDSCH, the location is indicated
by PDCCH and No HARQ. MSG2 content:
Preamble indication Timing adjustment information Temporary C-RNTI Msg3 resource allocation information
UE detects RA response in a time window after sending MSG1. If UE fails to receive the RA respondence in a time window, this RA process is terminated, otherwise it goes to step3.
UE Random Access Procedure
MSG3 According to MSG2 TPC indication, estimate pathloss and RB number
forPUSCH, UE cacaulates the MSG3 transmitting power. It’s open loop power control.
According to random access response, UE send MSG3 on dedicated resource. MSG3 needs HARQ.
MSG3 content: In attach : send RRC Connection Request on CCCH, include
NAS UE ID and establishment cause, but no NAS signalling message.
In RRC Connection Re-establishment: Send RRCConnection ReestablishmentRequest on CCCH no NAS message
In handover : send Handover Confirm on DCCH with UE C-RNTI. Other (uplink or downlink arrives):send UE C-RNTI.
UE Random Access Procedure
MSG4 : contention resolution Collision detect: eNB sends contention resolution ID ( UE
NAS ID ) on PDSCH or send C-RNTI on PDCCH to UE. With HARQ MSG4 content:
UE NAS ID Resource allocation information
UE: If UE finds its own NAS-layer ID is sending, UE sends ACK and
temporary C-RNTI becomes C-RNTI.Uplink synchronization finish.UE waits for being schedulled and send data on uplink.
If UE fails to detect NAS ID, there is a collision, UE waits a random time and do random access again.
UE Random Access Procedure
Random Access Based on Non-Competitiveness
UE eNB
RA Preamble assignment0
Random Access Preamble 1
Random Access Response2
UE Random Access Procedure
1) eNB send non-contention Random Access Preamble to UE,and this preamble is not broadcasted in the Broadcast information channel.
Random Access Based on Non-Competitiveness
UE Random Access Procedure
Random Access Based on Non-Competitiveness 2)UE send dedicated preamble on RACH. 3) eNB generates the RAR on MAC layer, and send the
RAR in DL-SCH,random access success.
Content
LTE channel introduction and channel mapping
UE power on procedure
UE random access procedure
Random access special scenarios application
UE attach signalling flow
UE eNB
1
2
Min delay
2msMsg2: RA response on PDSCH
Msg1: preamble
Msg0: Dedicated Preamble ID
Mask Index
Msg3: connection requirement, ect3
Delay about
5ms
0
Random Access Based on Non-Competitiveness: Scenario 4
eNB MSG0 Send Msg0 on PDCCH; Include Dedicated Preamble
and Mask Index; With HARQ; Initiated reason:
UE is out of synchronization on uplink,
Downlink data coming No need to allocateC-Rnti in
Msg2 UE
UE is Out of synchronization and monitoring to receive PDCCH order;
Send Msg1 with dedicated preamble
Msg3 is not useful , if there is data ,sending data , or sendingPadding。
Timer
Random Access Based on Non-Competitiveness: Scenario 4 ( UE leave) eNB send MSG0 on PDCCH
Msg0 is send on PDCCH; Include Dedicated Preamble
and Mask Index; With HARQ; Initiated reason :
UE is out of synchronization on uplink,
Start timer and timer is time out. purpose : suspecting UE
leaving, so release connection to avoid UE process hanging
No need to allocateC-Rnti in Msg2
UE UE hardware problem or power
off, not camping in the network.
UE eNB
2
Min delay
2msMsg2: RA response on PDSCH
Msg1: preamble
Msg0: Dedicated Preamble ID
Mask Index
Msg3: connection requirement, ect3
Delay about
5ms
0
Out of Sync
Timer
1
Timer
Random Access Based on Non-Competitiveness : Scenario 3
eNB send MSG0 on PDCCH Msg0 is send on PDCCH Include Dedicated Preamble
and Mask Index With HARQ Initiated reason :
Source eNB apply dedicated preamble from target eNB and then send preamble to UE.
UE Monitor to receive PDCCH
order. Send Msg1 with dedicated
preamble
UES-eNB
1
2
Min delay
2msMsg2: RA response on
PDSCH
Msg1: preamble
Msg0: Dedicated Preamble ID
Mask Index
Msg3: connection requirement, ect3
Delay about
5ms
T-eNB
0
Dedicated Preamble Mask Index
Measure Report
2
UE eNB
Msg1: preamble
Msg2: RA response on PDSCH
min delay
2ms
1
Msg3: connection requirement, ect
3
Delay about
5ms
Random Access Based on Competitiveness: Scenario 5
eNB No need MSG4 Send Temporary C-Rnti in RAR. MAC identifying Msg3 is for UE
re-synchronization; MAC notice L3 that UE re-
synchronization success. L3 send RRC Connection
Reconfiguration to re-setup connection.
UE Uplink data coming but uplink is
at non synchronization. Send RA request Include C-Rnti in Msg3,and
scrambling MSG3 by Temporary C-Rnti.
Content
LTE channel introduction and channel mapping
UE power on procedure
UE random access procedure
Random access special scenarios application
UE attach signalling flow
UE attach
Attach flow
UE attach
NAS connection setup
Rrcconection setup
S1connection setup
UE attach
Attach/dettach signalling flow