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


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


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.


Service Channel: PDSCH PDSCH: Physical Downlink Shared Channel PDSCH Bears service data, L3 signalling message,

paging and SIB information. Modulation: QPSK, 16QAM, 64QAM.


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.


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


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


Antenna port 5

5R

5R

5R

5R

5R

5R

5R

5R

5R

5R

5R

5R

0l 6l6l 0l


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.


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


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


0l 6l6l

CFI

0l


0l 6l6l

CFI

TDD FDD

TDD Downlink Channel Location

Content






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


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


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


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.


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


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.


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






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.)


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.


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


Random Access Based on CompetitivenessUE eNB

Random Access Preamble1

Random Access Response 2

Scheduled Transmission3

Contention Resolution 4


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.


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.


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.


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.


Random Access Based on Non-Competitiveness

UE eNB

RA Preamble assignment0

Random Access Preamble 1

Random Access Response2


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


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






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


Mask Index


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


Mask Index


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






UE attach

Attach flow

UE attach

NAS connection setup

Rrcconection setup

S1connection setup

UE attach

Attach/dettach signalling flow

zte lte random access

Documents

physical resource mapping

details of channel

channel mappingue power

downlink subframe

power control

uplink scheduling permission

downlink system bandwidth

scheduling information