3g parameter initial parameter planning 06

Customer confidential 1 © NSN Siemens Networks 3G Radio Planning Essentials / NPO Capability Development

Initial Parameter Planning 3GRPESS – Module 6


Module 6 – Initial parameter planning

Objectives

After this module the participant shall be able to:-

• Understand the basic parameter settings required for

network launch


Module contents

• Scrambling Code Planning

• Neighbour List Planning

• Location, Routing and Service Area Planning

• UTRAN Registration Area Planning


Module contents






• 512 Primary scrambling codes are organised into 64 groups of 8 – Each Primary scrambling code has 15 Secondary scrambling codes – Each Primary & Secondary scrambling code has left and right Alternate scrambling codes

• Scrambling code planning refers to assigning the Primary scrambling codes • Each cell is assigned 1 Primary scrambling code • Scrambling code planning strategies can be defined that maximise the number of neighbours

belonging to the same code group, or that maximise the number of neighbours that belong to different code groups

– The difference between the two strategies remains unquantified in the field and is likely to depend upon UE implementation

• Scrambling code planning requires co-ordination at international borders • Scrambling code planning can be completed independently for each RF carrier • Scrambling code planning can be completed using a radio network planning tool or a home made

tool • Scrambling code plan should account for future network expansion

Introduction


Air-Interface BCCH Synchronisation (I)

Step 1 • Search for Primary Synchronisation Channel (P-SCH) • Same chip sequence within every timeslot of every cell of every operator • Chip sequence has length of 256 chips • Provides slot synchronisation

CP

2560 Chips 256 Chips

CP CP CP

P-SCH

Step 1 is the same for all scrambling code planning strategies


Air-Interface BCCH Synchronisation (II)

Step 2 • Search for Secondary Synchronisation Channel (S-SCH) • Different series of 15 chip sequences for each code group • Each chip sequence has a length of 256 chips • Select 1 out of 64 => relatively large probability of error • Relatively low UE processing requirement relative to step 3 • Only necessary to identify 3 consecutive chip sequences to identify code group • Provides frame synchronisation and identifies Primary scrambling code group

Cs1

2560 Chips 256 Chips

Cs2 Cs15 Cs1

Emphasis is placed on Step 2 if scrambling code plan maximises the number of neighbours with different scrambling code groups


Air-Interface BCCH Synchronisation (III) Step 3 • Search for CPICH • Identifies Primary scrambling code • Select 1 out of 8 => relatively low probability of error • Relatively high UE processing requirement relative to step 2 • Not necessary to correlate complete 38400 chip frame to identify scrambling code

CPICH

38400 Chips = 10 ms radio frame

Emphasis is placed on Step 3 if scrambling code plan maximises the number of neighbours with the same code group


Impact of Neighbour List Combining (I)

• When a UE is in soft handover then the RNC combines the neighbour lists belonging to the active set cells

• It is necessary that duplicate scrambling codes do not appear within those lists • Checks should be made to ensure that cells within potential active sets do not

have different neighbours with the same scrambling code

Active Radiolink

Active Radiolink

UE in soft handover

Neighbour to active set cell


Example scrambling code clash scenario 1

SC100 SC100


Impact of Neighbour List Combining (II)

• Checks should be made to ensure that no cells are neighboured to two or more cells which have neighbour lists including the same scrambling code for different target cells

Active Radiolink

UE in soft handover



SC100

SC100 Example scrambling code clash scenario 2


Example Scrambling Code Plan

• Area with 12 Node B • Strategy has been to

minimise the number of code groups used in neighbouring cells

• Two code groups enough up to 15 neighbours

IntraFreqNcell ScrCode

UE

Serving cell

Cluster of cells using 2 code

groups


Recommendations

• Isolation between cells assigned the same scrambling code should be maximised

– isolation between cells assigned the same scrambling code sufficiently great to ensure that a UE never simultaneously receives the same scrambling code from more than 1 cell

– isolation between cells assigned the same scrambling code sufficiently great to ensure that a UE never receives a scrambling code from one cell while expecting to receive the same scrambling code from second cell

• Specific scrambling codes should be excluded from the plan to allow for future network expansion.

• The same scrambling code plan should be assigned to each RF carrier • Scrambling code planning should be completed in conjunction with neighbour list

planning • Scrambling code audits should be completed in combination with neighbour list

audits • Checks should be made to ensure that no cells are neighboured to two or more

cells which have neighbour lists including the same scrambling code for different target cells


Module contents






Introduction • Neighbour lists:

– 3G intra-frequency – 3G inter-frequency – 3G inter-system – 2G inter-system

• High quality neighbour lists are critical to the performance of the network • Neighbour lists are usually refined during pre-launch or post-launch optimisation

– Neighbour list planning should be as accurate as possible – Impact upon pre-launch optimisation has to be recognised – Pre-launch optimisation often limited to specific drive route which may not identify all

neighbours – Neighbour list tuning usually achieves the greatest gains during pre-launch

optimisation

• Optimisation tools based upon RNC logging can also be used to refine neighbour lists subsequent to launch


3G Intra-Frequency Neigbour Lists • Intra-frequency neighbours are used for cell re-selection, soft handover, softer

handover and intra-frequency hard handover

• Missing neighbours result in unnecessarily poor signal to noise ratios

• Excessive number of neighbours – increase the UE measurement time – may lead to important neighbours being deleted during soft handover

• Intra-frequency neighbour lists are combined for both intra-RNC and inter-RNC soft handover (assuming inter-RNC soft handover is supported)

• Intra-frequency neighbour lists are transmitted in SIB11 and dedicated measurement control messages

CPICH Ec/Io SC100 SC200

Drop

Cell Selection

Time

Missing neighbours can be identified from UE log files as a decrease in CPICH Ec/Io until connection drops and then cell selection allows sudden improvement Example SC200 missing from neighbour list associated with SC100 UE movement


Neighbour List Combining Intra-Frequency Neighbours

• When a UE is in soft handover then the neighbour lists belonging to each of the active set cells are combined

• Not all vendors offer neighbour list combining

• The RNC generates a new intra-frequency neighbour list after every active set update procedure (events 1a, 1b and 1c)

• The RNC transmits the new intra-frequency neighbour list to the UE if the new list differs from the existing list

1. Active set cells 2. Neighbour cells which are common

to three active set cells 3. Neighbour cells which are common

to two active set cells 4. Neighbour cells which are defined

for only one active set cell

Generating a combined intra-frequency neighbour list

Update


Parameters • Intra-Frequency neighbours are defined using the ADJS parameter set • Each neighbour has its own set of ADJS parameters

WCELL

ADJS

WBTS

RNC

HOPS 100

32

RT NRT HSDPA

Structure of databuild

RAS05 ADJS parameters

• 3GPP allows the network to specify a maximum of 32 intra-frequency cells for the UE to measure

• Serving cell + 31 Intra-frequency neighbours when not in soft handover

• 2-3 serving cells + 30-29 neighbours in soft handover

• Size of SIB11 can limit the number of neighbours for cell re-selection

Intra-Frequency Neighbours


3G Inter-Frequency Neigbour Lists • Inter-frequency neighbours are used for inter-frequency cell re-selection and

inter-frequency handover • The NSN RNC allows a maximum of 48 inter-frequency neighbours to be

defined with a maximum of 32 on any one RF carrier – 3GPP specifies that a max. of 32 inter-frequency neighbours can be broadcast in

SIB11 • NSN does not support

– inter-frequency handover from CELL_FACH – inter-frequency handover while anchoring an RNC

• Excessive neighbours

– increase the UE measurement time – may lead to important neighbours being deleted during soft handover

• Inter-frequency neighbours are usually introduced after the network has been

launched and so refining them is usually a post launch optimisation task


Neighbour List Combining Inter-Frequency Neighbours

• When a UE is in intra-RNC soft handover then the neighbour lists belonging to each of the active set cells are combined

• Neighbour lists are not combined for inter-RNC soft handover because the NSN RNC does not support inter-frequency neighbour signalling across the Iur


• Neighbour lists are not updated once compressed mode measurements have begun, i.e. inter-frequency neighbour lists are dependant upon the active set cells when inter-frequency handover is triggered

1. Neighbour cells which are common to three active set cells

2. Neighbour cells which are common to two active set cells

3. Neighbour cells which are defined for only one active set cell

Generating a combined inter-frequency neighbour list

Inter-Frequency Neighbour List


Parameters Inter-Frequency Neighbours

• Intra-Frequency neighbours are defined using the ADJI parameter set • Each neighbour has its own set of ADJI parameters

WCELL

ADJI

WBTS

RNC

HOPI 100

48

RT NRT


RAS05 ADJI parameters



3G Inter-System Neigbour Lists

• GSM neighbours are used for inter-system cell re-selection and inter-system handover • 3GPP specifications allow a maximum of 32 inter-system neighbours to be defined • Inter-system neighbours are broadcast in SIB11 for cell re-selection and are transmitted

in dedicated measurement control messages for inter-system handover • NSN does not support

– inter-system handover from CELL_FACH – inter-system handover while anchoring an RNC

• The NSN RNC instructs the UE to measure all GSM neighbours for RSSI measurements but one specific neighbour for BSIC verification

• Excessive neighbours – increase the UE measurement time – may lead to important neighbours being deleted during soft handover

• GSM neighbour lists can be based upon existing BSC 2G neighbour lists when sites are co-sited

• If an operator has both GSM900 and DCS1800 networks then it is possible to define inter-system neighbours only for the GSM900 layer or only for the DCS1800 layer


Neighbour List Combining Inter-System Neighbours

• When a UE is in intra-RNC soft handover then the neighbour lists belonging to each of the active set cells are combined

• Neighbour lists are not combined for inter-RNC soft handover because the NSN RNC does not support inter-system neighbour signalling across the Iur


• Neighbour lists are not updated once compressed mode has begun, i.e. inter-system neighbour lists are dependant upon the active set cells when inter-system handover is triggered

1. Neighbour cells which are common to three active set cells

2. Neighbour cells which are common to two active set cells

3. Neighbour cells which are defined for only one active set cell

Generating a combined inter-system neighbour list

Inter-System Neighbour List


Parameters Inter-System Neighbours

• Intra-Frequency neighbours are defined using the ADJG parameter set • Each neighbour has its own set of ADJG parameters

WCELL

ADJG

WBTS

RNC

HOPG 100

32

RT NRT


RAS05 ADJG parameters



Maximum Neighbour List Lengths (I)

• SIB11 is used to instruct UE which cells to measure in RRC Idle, CELL_FACH and CELL_PCH • TS25.331 includes a contradiction made by 3GPP, i.e. SIB11 should be able to accommodate

information regarding 96 cells, but SIB11 cannot exceed 3552 bits and this is insufficient to accommodate information regarding 96 cells

• If a NSN RNC is configured with a cell which is configured with more neighbours than SIB11 can accommodate then the cell is blocked and an alarm is raised

• NSN has issued RNC Technical Note 46 to specify that when Hierarchical Cell Structure is disabled, a maximum of 47 cells should be configured. This is a worst case figure and in general more cells can be included

• RU10 RNC support activation of SI11bis, which enables transmission of all defined neighbours

Max

imum

Siz

e of

SIB

11

Adjs Adji

Adjg

Complete set of neighbours will not fit


Maximum Neighbour List Lengths (II)

• The size of SIB11 can be estimated from the number of intra-frequency, inter-frequency and inter-system neighbours

• The quantity of data associated with each neighbour can vary depending upon which information elements are included

AdjsQoffset1 or AdjsQoffset2 included

CPICH transmit power included

Size of single ADJS

Neither No 48 bits Either One No 48 or 56 bits (average of 55.2 bits)

Both No 56 or 64 bits (average of 62.1 bits) Neither Yes average of 54.2 bits

Either One Yes average of 61.1 bits Both Yes average of 68.0 bits

Example for intra-frequency neighbours


Maximum Neighbour List Lengths (III)

• Expression can be generated to identify whether or not a particular combination of neighbours is likely to exceed the capacity of SIB11

)63()6.73()1.61(222_113552_11

ADJGADJIADJSSizeSIBbitsSizeSIB

×+×+×+≈<

• RAS05 includes parameters ADJS, ADJI and ADJG parameters: • AdjsSIB • AdjiSIB • AdjgSIB

• These parameters allow larger neighbour lists to be defined for CELL_DCH by specifying whether or not specific neighbours should be included in SIB11


2G Inter-System Neigbour Lists (I) • BSC inter-system neighbours are used for inter-system cell re-selection and

inter-system handover • NSN’s implementation of the BSS allows the definition of 32 UMTS FDD

neighbours • The definition of 3G neighbours has an impact upon the maximum number of

GSM neighbours which can be defined within the BSC

Without 3G neighbours

With 3G neighbours

Without common BCCH

With common BCCH

32 31

31 30


2G Inter-System Neigbour Lists (II) • When a UE is in GSM idle mode, GPRS packet idle mode or GPRS packet

transfer mode then it reads the 3G neighbour list from SI2quater and PSI3quater system information messages

• When a UE is in GSM connected mode then it reads the 3G neighbour list from measurement information messages which are sent on the SACCH

• The length of a single SI2quater message is not sufficient to accommodate 32 inter-system neighbours

• A single SI2quater message is able to accommodate 10 3G neighbours. This means that it is beneficial if 3G neighbour lists can be limited to a length of 10

• If multiple SI2quater messages are required then the UE must wait until it has received the complete set before it is able to make a cell re-selection decision

• If neighbours are missing then UE may fail inter-system handovers and may remain on the GSM system longer than necessary

• If 3G sites are co-sited with 2G sites then 3G neighbour lists configured within the BSC can be based upon the existing 2G neighbour lists


Typical Neighbour List Lengths

• Neighbour list lengths are scenario dependant • Some examples

Urban

Suburban

3G intra-freq

14

10 10

Rural

3G inter-freq

3G inter-sys

2G inter-sys

14

10 10

14

10 10

16

12 12


Module contents






Introduction • Location Areas (LA) and Routing Areas (RA) are used by the core network to track the

location of a UE • LA are used by the CS domain whereas RA are used by the PS domain • Each core network service domain has its own independent state machine for each UE • The main CS service states are CS-DETACHED, CS-IDLE and CS-CONNECTED • The main PS service states are PS-DETACHED, PS-IDLE and PS-CONNECTED

Node B

MSC

UE

RNC

Iu cs

SGSN

Single RRC Connection

Iu ps

CS state

PS state

CS state

PS state

Two Iu Signalling Connections Mobility Management (MM) Sublayer

Connection Management (CM) Sublayer

Session Management (SM) Entity

Call Control (CC) Entity

Mobility Management (MM) Entity

GPRS Mobility Management (GMM) Entity

Access Stratum

Non-Access Stratum

UE Non-Access Stratum

• LA and RA are handled by the Non-Access Stratum layer within the UE and core network

Not registered Iu signalling connection Registered but no Iu

signalling connection


Location Areas • A UE in CS IDLE state does not have to update the CS core of its location

when moving within a LA • a LA consists of cells belonging to one or more RNCs that are connected to the

same CN node, i.e. one MSC/VLR • The minimum size of a Location Area (LA) is a single cell • The maximum size of a LA is the collection of cells connected to a single VLR • The mapping between a LA and its associated RNCs is handled by the

MSC/VLR • The mapping between a LA and its cells is handled by the RNC • A LA is identified globally using a Location Area Identification (LAI) • The LAI is a concatenation of the Mobile Country Code (MCC), Mobile Network

Code (MNC) and Location Area Code (LAC) 2 Bytes => 65336 values

Large number of LA per PLMN

00 00 and FF FE values are reserved


Routing Areas • A UE in PS IDLE state does not have to update the PS core of its location when

moving within a RA • a RA consists of cells belonging to one or more RNCs that are connected to the

same CN node, i.e. one SGSN • The minimum size of a Routing Area is a single cell • A RA is always contained within a single LA • it is possible for RA and LA to be defined to be equal • The mapping between a RA and its associated RNCs is handled by the SGSN • The mapping between a RA and its cells is handled by the RNC • A RA is identified globally using a Routing Area Identification (RAI) • The RAI is a concatenation of the LAI and the Routing Area Code (RAC)

1 Byte => 256 values

Maximum of 256 RA per of LA


Paging Channel

fach-PCH-InformationList { { transportFormatSet commonTransChTFS : { tti tti10 : { { rlc-Size fdd : { octetModeRLC-SizeInfoType2 sizeType1 : 4 }, numberOfTbSizeList { zero : NULL, one : NULL }, logicalChannelList allSizes : NULL } },

From SIB 5

Transmission Time Interval = 10 ms

Transport Block Size = (4 x 8) + 48 = 80 bits (equation from TS 25.331)

Maximum Transport Block Set Size = 1 * 80 = 80 bits

• NSN RAN provides an 8 kbps PCH transport channel on the S-CCPCH • 8 kbps is sufficient to include a single paging record per 10 ms • A single cell can thus page 100 UE per second • S-CCPCH can be shared with the FACH-c and FACH-u but PCH always has

priority • Paging completed over either a Location Area, Routing Area, RNC or Cell • Utilisation of paging capacity is maximised when paging is completed over a Cell

URA_PCH RRC state not currently supported and so paging does not occur over a URA


Strategies (I) • Small LA/RA

– Improves paging capacity because each IDLE state paging message is broadcast by fewer cells

– Increase in network signalling due to increased quantity of updates resulting from mobility

– Potential decrease in mobile terminated connection establishment success rate – (Potential decrease in mobile originated connection establishment success rate)

• LA and RA can be planned to be relatively large while levels of traffic are not too great

• Acceptable to plan location area across multiple RNC – Generates paging per RNC for UE which are in RRC Connected Mode

• LA and RA commonly planned to be of equal size

Cel


Strategies (II) • Possible to plan 2G and 3G networks using the LAI and RAI

– Requires unique 2G and 3G Cell Identities (CI) – Cell Global Identification (CGI) defined by

– core network is not able to distinguish between the two networks for paging purposes and both 2G and 3G paging appears on both the 2G and 3G networks

– less chance of a UE missing a paging message when it is completing inter-system cell re-selection

– increased quantity of paging on both systems and a requirement to co-ordinate cell identities. In practice it may be difficult to implement the same location areas for 2G and 3G as a result of them not having the same coverage areas and not all sites being co-sited

CGI must be unique


Strategies (III)

• LA and RA boundaries used for the 2G system are likely to be relatively mature and may have already been optimised in terms of their locations

• This means that they provide a good starting point for the definition of 3G LA and RA boundaries.

• LA and RA boundaries should not run close to and parallel to major roads nor railways otherwise there is a risk of relatively large numbers of updates.

• Likewise, boundaries should not traverse dense subscriber areas • Cells which are located at a LA or RA boundary and which experience large

numbers of updates should be monitored to evaluate the impact of the update procedures.

• It is only necessary to decrease the size of a RA area relative to a LA if there is a large quantity of paging from the PS service domain

• LA and RA boundaries should be accounted for during the cluster identification task associated with pre-launch optimisation

• Clusters should be defined such that LA and RA boundaries are crossed during drive tests. This helps to verify that the update procedures are successful and do not have a significant impact upon services


Service Areas • A Service Area (SA) is identified globally using its Service Area

Identifier (SAI) • The SAI is a concatenation of

– MCC + MNC + LAC + Service Area Code (SAC)

• Service areas are used for emergency service calls • The SAC can be configured on a per cell basis with a value equal

to the cell identity (CI). This helps to simplify system design

• RAN04 introduces the Service Area Broadcast (SAB) feature which makes use of a third S-CCPCH and Service Area Codes for SAB (SACB)

• A specific SAC can be assigned to multiple cells within a location area whereas a SACB must be unique for each cell within a location area.


Module contents






URA_PCH state

• RU10 RNC support URA_PCH state transition • The purpose of this state is to decrease the cell update signaling

due to cell reselection, which saves RNC and UE resources • When the UE is in Cell_FACH or Cell_PCH state

– Location is known by the cell level – Cell updates sent by the UE when a cell re-selection occurs

• If too many cell updates (MaxCellReselections) are received in a predefined time window (CellReselectionObservingTime), the UE is ordered to transfer to URA_PCH state in order to reduce cell update signalling between the UE and RNC

• In URA_PCH state UE sends URA update to RNC after re-selection to new URA area


URA planning

• The planning of URA involves a balance between paging load and signalling load

– Large URA : Paging load increases – Small URA : Frequent URA updates, signalling load and also UE power

consumption increases

• Multiple URA Ids can be configured for each cell

– Reduces possible ping-pong between URA areas

• Initially URA can be designed RNC wide

– Simple design, each RNC area with different URA Id

– URA can be optimised with counter info


Module 6 – Initial parameter planning

Summary

• The initial parameter planning includes configuration of

essential parameters that are required for network launch

• Groups of parameters that are dependent on the

network layout

• Most parameters are configured as default

3g parameter initial parameter planning 06

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