6-PCI Planning Slides

PCI Planning

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PCI Planning Contents PCI Planning  Initial Access Procedure  Cell Search Procedures  Physical layer Cell Identity  Minimising Groups/Codes

Graham Whyley Technical Master Trainer

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Initial Access Procedure UE Power ON Cell Search

Read SIB’s

Cell Selection

Random access

Step 1 – Primary Synchronization Signal · CodeID =code (0,1,2) Step 2 – Secondary Synchronization Signal (SSS)-Group · Find Physical Layer Cell ID · Cyclic Prefix Length detection · FDD or TDD Detection Step 3 – Reference Signal Detection / PBCH Detection (Receiving System Information)

3

Synchronization signals There are 2 synchronization signals in LTE downlink, Primary synchronization signal – PSS Secondary synchronization signal – SSS

3 PRB 6 x 180kHz =1.080Mhz 3 PRB

The PSS and SSS are both mapped always in Subframe 0 and 5 for FDD

4

PSS/SSS detection The PSS/SSS detection is a very early procedure that the UE should do, to get the cell ID of the system

There are 3 different sequences of PSS 168 different sequences of SSS

Physical layer Cell Identity = (3 × Group(0 to 167)) + Code 0-2

5

Cell Search Procedures Cell Search

Read SIB’s

Cell Selection

Random access

There are two different types of synchronization procedures. The first one is when the UE is not connected to LTE cell and wants to access LTE network. This happens when the UE is switched on or when the reception is restored after being in an area with no connection. The second type of synchronization procedure happens when the UE is already connected to LTE cell and detects a new cell. This means the UE will prepare for a handover to a new cell and will report this to the old cell. •

Both these procedures use two types of synchronization signals, that is the primary synchronization signal (PSS) and the secondary synchronization signal (SSS) which are broadcasted in each cell.

(P-SCH): for cell search and identification

•

S-SCH): for cell search and identification

6

Cell Acquisition After a mobile switches on, it runs a low-level acquisition procedure so as to identify the nearby LTE cells and discover how they are configured. In doing so, it receives the primary and secondary synchronization signals, reads the master information block from the physical broadcast channel and reads the remaining system information blocks from the physical downlink shared channel. Physical Cell layer identity • •



• •



Physical Cell layer identity The mobile starts by receiving the synchronization signals from all the nearby cells. From the primarysynchronization signal (PSS), it discovers the symbol timing and gets some incomplete information about the physical cell identity. From the secondary synchronization signal (SSS), it discovers the frame timing, the physical cell identity,

7

Initial Access Procedure Cell Search

Read SIB’s

Cell Selection

Random access

UE reads the MIB

Channel Bandwidth

UE reads the SIB 1

Scheduling Information Value Tag

UE reads the SIB

SIB2, SIB3, SIB4, SIB5, SIB6, SIB7, SIB8, SIB9, SIB10, SIB11, SIB12, SIB13 8


Read SIB’s

Cell Selection

Random access

SIB1 contains cell access related information (e.g. a PLMN identity list, tracking area code, cell identity, etc.), information for cell selection (e.g. minimum required Rx level in the cell and offset), p-Max, frequency band indicator, scheduling information, TDD configuration, SI-window length and system information value tag etc...

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Read SIB’s

Cell Selection

Random access

The SystemInformationBlockType3 (SIB3) contains cell re-selection information common for intrafrequency, inter-frequency and/or inter-RAT cell re-selection (i.e. applicable for more than one type of cell re-selection but not necessarily all) SIB3 also contains cell reselection priority information for the concerned carrier frequency or a set of frequencies ...

10


Read SIB’s

Cell Selection

Random access

The SystemInformationBlockType4 (SIB4) contains intra-frequency neighboring cell information for intra-LTE intra-frequency cell reselection, such as neighbour cell list, and black listed Cell list...

11


Read SIB’s

Cell Selection

Random access

The SystemInformationBlockType5 (SIB5) contains neighbour cell related information for interfrequency cell-reselection i.e. the information about neighbor E-UTRA frequencies

12


Read SIB’s

Cell Selection

Random access

The SystemInformationBlockType6 (SIB6) contains information relevant only for inter-RAT cell reselection i.e. information about UTRA frequencies and UTRA neighbouring cells relevant for cell re-selection

13


Read SIB’s

Cell Selection

Random access

The SystemInformationBlockType7 (SIB7) contains inter-RAT cell re-selection information only for GERAN. It includes cell re-selection parameters for each frequency. SIB7 also contains cell reselection priority information

14


Read SIB’s

Cell Selection

Random access

Random Access Preamble

Random Access Preamble

Random Access Response

Timing Advance/ C-RNTI

RRC Connection Request 15

Introduction to PCI planning • •



Physical layer Cell Identity (PCI) identifies a cell within a network  equivalent of UMTS scrambling code There are 504 Physical Layer Cell Identities  compared to 512 UMTS scrambling codes  PCI are organised in 168 groups of 3 codes  compared to 64 groups of 8 for UMTS scrambling codes Physical layer Cell Identity = (3 × Group(0 to 167)) + Code 0-2

Id = 0 Id = 2

Id = 6 Id = 8

Cluster Group Id = 1 Id = 3 Id = 5

Id = 7 Id = 9

Id = 11 Id = 4

Id = 10 16

Cell Search Physical layer Cell Identity = (3 × Group(0 to 167)) + Code 0-2

PSS Id = 0 Id = 2

Id = 6 Id = 8

Id = 1 Id = 3 Id = 5

SSS Id = 7

Id = 9 Id = 11

Id = 4

Id = 10

Read SIB’s Frequency Shift 17

Physical layer Cell Identity

Physical layer Cell Identity = (3 × Group(0 to 167)) + Code 0-2 = (3 x 2) + 2 =8

Group(0 to 167) Code (0-2)

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Physical layer Cell Identity

Physical layer Cell Identity = (3 × Group(145)) + Code 2 = 437

Physical layer Cell Identity = (3 × Group(145)) + Code 1 = 436

Id = 0 Id = 2

Id = 6

Id = 1 Id = 3 Id = 5


Id = 7 Id = 9

Id = 11 Id = 4

•

Id = 8

Id = 10

•


Physical Cell layer identity 19

Minimising Groups. Physical layer Cell Identity = (3 × Group(0 to 167)) + Code 0-2

PCI=0

PCI=1

PCI=2

PCI=3

PCI= 4

PCI= 5

Group =0

Group =0

Group =0

Group =1

Group =1

Group =1

Code =0

Code =1

Code =2

Code =0

Code =1

Code =2

Carrier 1 PCI=0

Carrier 1 PCI=2

Carrier 1 PCI=1

ONLY TWO GROUPS USED

Carrier 1 PCI=3

Carrier 1 PCI=4

Carrier 1 PCI=5

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Minimising Codes. Physical layer Cell Identity = (3 × Group(0 to 167)) + Code 0-2

PCI=0

PCI=6

PCI=9

PCI=12

PCI= 15

PCI= 18

Group =0

Group =2

Group =3

Group =4

Group =5

Group =6

Code =0

Code =0

Code =0

Code =0

Code =0

Code =0

Carrier 1 PCI=0

Carrier 1 PCI=9

Carrier 1 PCI=6

ONLY ONE CODE USED

Carrier 1 PCI=12

Carrier 1 PCI=15

Carrier 1 PCI=18

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Planning Overview •

PCI planning is analogous to scrambling code planning in UMTS: • • • •

a UE should never simultaneously receive the same PCI from more than 1 cell the isolation between cells using the same PCI should be maximised neighbour cells should not have the same PCI (collision free planning) neighbours of neighbours cell should not have the same PCI (confusion free planning)



Additionally, PCI planning should account for Frequency Shift

•

There should be some level of co-ordination across international borders when allocating PCI • avoids operators allocating the same PCI to cells on the same RF carrier and in neighbouring geographic areas

22

Cell Specific Reference Signals - ports 0 to 3 • Reference signals similar to CPICH in WCDMA • Reference signals are distributed in both the time and frequency domains – allows the propagation channel to be estimated across both domains • Used for cell search, channel estimation and neighbour cell monitoring • Reference signals reduce the maximum achievable user plane bit rate by occupying a subset of the resource block symbol locations Same PCI

Same PCI

12 sub-carriers

12 sub-carriers

Without MIMO

Antenna 1

1 ms

Antenna 1

1 ms 23

Reference Signal Receive Power RSRP (Reference Signal Receive Power) is the average power of Resource Elements (RE) that carry cell specific Reference Signals (RS) over the entire bandwidth, so RSRP is only measured in the symbols carrying RS Reference signals similar to CPICH in WCDMA

Reference signals reduce the maximum achievable user plane bit rate by occupying a subset of the resource block symbol locations

12 sub-carriers

Used for cell search, channel estimation and neighbour cell monitoring

Without MIMO

Reference signals are distributed in both the time and frequency domains

Antenna 1

1 ms Reference Signals occupy 8 out of 168 symbols

RSRP measures signal power from a specific sector while excluding noise and interference from other sectors

24

Sub channel RSRP (Reference Signal Receive Power) is the average power of Resource Elements (RE) that carry cell specific Reference Signals (RS) over the entire bandwidth, so RSRP is only measured in the symbols carrying Reference Signals

25

Reference Signal Received Power (RSRP)

26

Received Signal Strength Indicator RSSI is effectively a measurement of all of the power contained in the applicable spectrum (1.4, 3, 5, 10, 15 or 20MHz). This could be signals, control channels, data channels, adjacent cell power, background noise, everything. RSSI varies with LTE downlink bandwidth

Point of interest 27

Reference Signal Receive Quality RSRP provides information about signal strength and RSSI helps in determining interference and noise information. This is the reason, RSRQ (Reference Signal Receive Quality) measurement and calculation is based on both RSRP and RSSI

RSRQ is defined as the ratio N×RSRP / (EUTRA carrier RSSI)

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Reference Signal Received Quality (RSRQ)

LOADED UNLOADED RSRQ affected by cell loads.

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Reference Signal Receive Quality Bandwidth 1.4 (MHz) # of RBs 6 Subcarrier s

72

3

5

10

15

20

15

25

50

75

100

180 300 600 900 1200

Point of interest

RSRQ = n x RSRP/RSSI RSRQ = 10 log 25 + (-102.77 –(- 82 .71) =13.97 + (-20.06) =-6.09 30

Cell Specific Reference Signals (ports 0 to 3) Antenna 2

2+2 MIMO

Antenna 1

Antenna 2

Antenna 3

Antenna 4

4+4 MIMO

Antenna 1

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Down Link Reference Signals SNR & SINR

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DLRS SNR

DLRS SNR +40.3 DLRS SINR +33.7 POWER 33

DLRS SNR

DLRS SINR

34

Frequency shifts

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Frequency shifts The PCI determines the position of the Cell specific Reference Signal in the frequency domain There are six possible frequency shifts of RSs

Different ν shift, should be used in adjacent cells

Shift= 0 Shift= 1

Shift= 2

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Frequency shifts PCI

GROUP

CODE

CELL SPECIFIC FREQ SHIFT

0

0

0

0

1

0

1

1

2

0

2

2

3

1

0

3

4

1

1

4

5

1

2

5

6

2

0

0

CELL SPECIFIC FREQ SHIFT This determines the DLRS pattern (time frequency positions)

37

Frequency shifts PCI =0

PCI =0

PCI =0

PCI =6

PCI

GRO UP

CO DE


0

0

0

0

1

0

1

1

2

0

2

2

3

1

0

3

4

1

1

4

5

1

2

5

6

2

0

0


PCI =1

PCI =7 PCI =0

PCI =0

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Minimising Groups. Physical layer Cell Identity = (3 × Group(0 to 167)) + Code 0-2

PCI=0

PCI=1

PCI=2

PCI=3

Group =0

Group =0

Group =0

Group =1

Code =0

Code =1

FREQ SHIFT FREQ SHIFT =0 =1

Code =2

Group =1

Code =1

FREQ SHIFT FREQ SHIFT FREQ SHIFT =2 =3 =4

Carrier 1 PCI=0

Carrier 1PCI=2

Code =0

PCI= 4

Carrier 1 PCI=1

PCI= 5 Group =1

Code =2 FREQ SHIFT =5

Carrier 1 PCI=3

PCI

GRO UP

CO DE


0

0

0

0

1

0

1

1

2

0

2

2

3

1

0

3

4

1

1

4

5

1

2

5

6

2

0

0


Carrier 1PCI=4

Carrier 1 PCI=5

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Minimising Codes.

PCI=0

PCI=6

PCI=9

Group =0 Code =0

Group =2 Code =0

Group =3 Code =0


PCI=12 Group =4 Code =0

PCI= 15 Group =5 Code =0

PCI= 18 Group =6 Code =0


FREQ SHIFT =0

Carrier 1 Carrier 1

PCI=0

PCI=12

Carrier 1 PCI=9

Carrier 1 PCI=6

Carrier 1 PCI=15

Carrier 1 PCI=18

PCI

GRO UP

CO DE


0

0

0

0

1

0

1

1

2

0

2

2

3

1

0

3

4

1

1

4

5

1

2

5

6

2

0

0

7

2

1

1

8

2

2

2

9

3

0

3

10

3

1

4

11

3

2

5

12

4

0

0

13

4

1

1

14

4

2

2

15

5

0

3

16

5

1

4

17

5

2

5

18

6

0

0

Very poor PCI planning 40

Using a planning tool

Very poor DLRS SINR

41

MIMO

42

LTE Reference Symbols Without MIMO

Antenna 1

Antenna 2

Antenna 1

Antenna 2

2+2 MIMO

Antenna 1

Antenna 4

4+4 MIMO

Antenna 3

43

PCI mod 3’ •

When using 2x2 or 4x4 MIMO, the Resource Elements allocated to the Cell specific Reference Signal coincide every 3rd PCI value

•

In practice, it is not possible to ensure that all neighbours have different ‘PCI mod 3’ results so compromise is to allocate:

– 1 PCI group per 3 sector eNode B – 2 PCI groups per 6 sector eNode B

Signal coincide every 3rd PCI value

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Best Planning Practice •

In practice, it is not possible to ensure that all neighbours have different ‘PCI mod 3’ results so compromise is to allocate:

Group =0 Code =0 FS =0

PCI=0

Group =0

PCI=1

Code = 1 FS =0

– 1 PCI group per 3 sector eNode B

Group =0

PCI=2

Code = 2 FS =0

– 2 PCI groups per 6 sector eNode B PCI=0

PCI=1

PCI=2

Group =0

Group =0

Group =0

Code =0

Code = 1

Code =2

FS =0

FS =1

FS =2

• When using 3-sector sites, neighbouring eNode B should use adjacent PCI groups 45


Very poor DLRS SINR

46


47


48

Questions

49

Questions 1. When PCI planning is it best to: A. Minimising Codes. B. Minimising Groups. PCI=0

PCI=6

PCI=9

Group =0 Code =0

Group =2 Code =0

Group =3 Code =0


PCI=0

PCI=1

PCI=2

PCI=3

Group =0

Group =0

Group =0

Group =1

Code =0

Code =1


Code =2

Code =0

PCI= 4 Group =1

Code =1


PCI=12

Group =4 Code =0

PCI= 15

Group =5 Code =0

PCI= 18

Group =6 Code =0


FREQ SHIFT =0

PCI= 5 Group =1

Code =2 FREQ SHIFT =5

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Questions 2. When using 2x2 or 4x4 MIMO, the Resource Elements allocated to the Cell specific Reference Signal coincide every 3rd PCI value TRUE FALSE

51

Questions 3. The group = 3 and the code =2. What is the PCI? a. b. c. d. e.

5 3 9 11 None of the above

Physical layer Cell Identity = (3 × Group(0 to 167)) + Code 0-2 = 3x3 + 2 = 11

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Questions 4. Connected mode means the UE does cell selection and reselection, location registration, reception of system information and enable the UE to establish an RRC connection for signalling or data transfer (including CSFB and VoLTE) as well as be able to receive possible incoming connections (via paging). TRUE FALSE

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Questions 5. From the primary synchronization signal (PSS), it discovers the symbol timing and gets some incomplete information about the physical cell identity. From the secondary synchronization signal (SSS), it discovers the frame timing, the physical cell identity,. TRUE FALSE

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In Closing  Thank you for attending

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6-PCI Planning Slides

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