22 Rach Algo v10

7/23/2019 22 Rach Algo v10

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RACH Algorithm (draft)

Shay Laslo Amit

LTE Research Engineer

Mobility CTO Group

7/23/2019 22 Rach Algo v10


© 2013-2014 Cisco and/or its affiliates. All rights reserved.

Research Partners

Shay Laslo Amit RAN Research Engineer, Mobility CTO Group, Cisco System

Dr. Tuvia Apelewicz CEO Muxline Ltd

Ziv Nuss Practical Engineer , Mobility CTO Group, Cisco Systems

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Parameters – high level list

Trigger: Cells with RA Failures / RA Success Rate / Intensity

Sequence of potential diagnose / actions

Root Sequence Issues: RSI Planning, Cell R Not enough opportunities: RA Opportunities, T

Narrow UL interference: RACH Frequency O

High mobility cells: Preamble Format, #

Wide UL interference: RACH power setting

DL interference TBD DL Load (PDCCH) TBD

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Root Cause Analysis

RSI Planning Module (Including Cell Range)

CBRA/CFRA Split Module

RA Opportunities Module (Configuration Index) Interference Module

RACH Frequency Offset

RACH power settings

Preamble Format

RA back-off Module (RA Reattempt delay)

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Algo modules flow

Filter 1

Yes

Time from

last RSI

planning

No

Yes

Yes

Rollback

with logMaintenance window?

SP policy

Wait to maintenance window

If needed according to RAN vendorRB Threshold check & log

Filter 1

still triggered

Yes

Filt

still trig

No

Next cycle

No

RA back-off

Module

Filter 1

still triggered

Yes

No No

Interference

Module

Next

cycle

PDCCH

Utilization > Thr-3

x > t2 days

t1 <x< t2 days Small RSI

planning

Wait to next

bigger RSI

planning

Load

Balancing

Module

Available in all

RAN vendors

x < t1 days

RSI planning time filter (next slide)

CBRA/CFRA

Module

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Filter 1 and 2

Passing Filter 1 only when:

CBRA success rate which is below threshold-1 &

CBRA failures above threshold-2

Or, CFRA success rate is below threshold-4 &CBRA failures above threshold-5

Filter 2

Does success rate and failures of CFRA worse than CBRA

If answer is Yes, go to CFRA/CBRA module

Does success rate and failures of CFRA better than CBRA

If answer is No, go to RSI planning filter

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RSI Planning Time Filter

Last RSI

change

t1 t2

Too close to last

RSI change,

Go to next module

Far enough from last/next

RSI change,

Make small RSI changes

Close enough

RSI chang

Wait to next wide

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RSI Planning – High level

RSI planning should include the following

RSI planning should include clustering abilities

SON will work on separated clusters for control purposes

Motivation is to determine the real required amount of RSI per Amount of RSI according to cell range plus additional RSIs as m

First RSI should be

Between 1 to 419

Odd position, according to physical RSI table

All bank of RSI should be different then it’s 1st tier neighbor

Bank of RSI is recommended to be different than it’s 2nd tier ne If straight RSI separation neighbors isn’t possible due to #neigh

Make separation according to neighbors weights

Trigger neighbors removals to ANR or report on it in a GUI

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Clustering Method

SON has identified triggered cells regarding RACH performance

Those cells will be gathered into clusters for RSI planning

Several clustering methods was identified, still wasn’t chosen - TBD

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CBRA / CFRA Module

Rollback


SP policy



Filter 4

CBRA SR < CFRA SR

CBRA Fails >> CFRA Fails

Yes

Main

KPIs OK?

No

RB-3

Yes

No

Yes

2nd cycle

Filter 4

still triggered

No

Filter 5

CBRA SR > CFRA SR

CBRA Fails << CFRA Fails

Yes

No

Main

KPIs OK?

Yes

No

RB-4

Filter 5

still trigge

2nd cycle

In

CFRA enabled?

YesIncrease one step

NumberOfRAPreambles

No

Decrease one stepNumberOfRAPreambles

Available in all

RAN vendors

Input-1

Yes

No

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CBRA / CFRA Module tradeoff

64 signatures separated into two: Contention based RA & Contentio

Contention free are part of handover procedure only

Contention based mainly are for access and reestablishment

Normally more signatures kept for contention based RA

Tradeoff is between mobility and accessibility performance

It depends where the border line should be

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RA Opportunity Module

Rollback


SP policy



In OIncrease opportunities

Main

KPIs OK?

No

Yes

Yes

Y1 cycle

Filter 1

still triggered

No

RB-6

Action Time

Window Passed?

YesRB-5

It is possible to increase RA opportunities from 1 to 2,3,5,10 in one r

Tradeoff is between improved access, delay and capacity for UL dat

In some situations even DL throughput could be harmed

Available in all

RAN vendors

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Interference Module

Rollback


SP policy



In

Identified as Narrow

Interference?

Yes

No

Main

KPIs OK?

No

RB-7

Yes

Yes

2nd cycle

ncrease PRACH Freq

Offset by x to

cleaner RB

UL RSSI > Threshold

Yes

No

Main

KPIs OK?

No

RB-8

Yes

Ye

Wide Interference Algo

Y2 cycle

Available in all

RAN vendors

Check

RACH

location **

Check Uplink

Interference on

PRB level

** RACH location – On frequency domain (PRB)

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Interference Module tradeoff and Neighbors

Tradeoff is between accessibility and capacity

When moving RACH location to a cleaner RB we’re occupying reso

could be used for data usage and instead we’re using it for better ac

Neighbors - When narrow interference as been identified on RACH

neighboring cells, it’s possible to allocate different frequency shift fo

within those cells

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Identifying Narrow Interference

UL RSSI

Frequency (PRBs)

PUCCH PUCCHACH

ΔY1

PRB

Ref1

ΔY2

PRB

Ref2

The exact location of RACH PRBs on frequency domain is known (configura

The relative UL RSSI in RACH PRBs is compared to other reference PRBs

The reference PRBs shall be part of those in which it’s possible to shift the R

If the relative UL RSSI of RACH is higher than a threshold ΔYi

Then it’s possible to shift RACH PRBs to a cleaner “area”

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Wide Interference Algorithm

TBD

B k Off M d l

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Back-Off Module

Rollback


SP policy



In OIncrease raBackOff

Timer x steps

Main

KPIs OK?

No

Yes

Yes

Y3 cycle

Filter 1

still triggered

No

RB-10

Action Time

Window Passed?

YesRB-9

Timer which set a delays for too close RA re-attempts

Tradeoff is between potential increase in delay and overloading RAC

Available in all

RAN vendors

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Thanks

C l

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Colors

Ericsson

ALU

NSN

ALL

Documents

22 Rach Algo v10