4.1 planning for network integration

Planning for Network Implementation

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© Nokia Siemens Networks GDC Jakarta / World Class NPI / December 2012

Implementation

• PCI Planning• PRACH Planning• UL DM RS Planning• TAC Planning

PCI Planning

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© Nokia Siemens Networks

PCI PlanningWhat is the PCI?•Physical Layer Cell Identity (PCI) identifies a cell within a network•There are 504 Physical Layer Cell Identities -> PCI is not unique!

Physical Layer Cell Identity = (3 × NID1) + NID2

NID1: Physical Layer Cell Identity group. Defines SSS sequence. Range 0 to 167

NID2: Identity within the group. Defines PSS sequence. Range 0 to 2

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NID2: .

•PCI is not the E-UTRAN Cell Identifier (ECI)• ECI is unique within a network• ECI does not need to be planned. ECI value is set by the system

• Physical Cell Identity is defined by the parameter phyCellID:Parameter Object Range Default

phyCellID LNCEL 0 to 503 Not Applicable

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

• A UE should never receive simultaneously the same identity from more than a cell• Maximum isolation required between cells with the same PCI• 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 needs to follow the ‘module’ rules : module3, module6 and module30• If mod3 rule is true then mod6 and mod30 are true

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• If mod3 rule is true then mod6 and mod30 are true• If mod6 is true then mod30 is true• If mod6 is not true then mod3 is not true• If mod30 is not true then mode6 is not true

•There should be some level of co-ordination across international borders when allocating PCIs• To avoid operators allocating the same identity to cells on the same RF carrier and in neighbouring geographic

areas

PCI PlanningImpact in Reference Signal Positions (1/2)• Reference signals are used for channel estimation, cell selection, cell reselection and handover

• The PCI determines the position of the cell specific reference signals (RS) in frequency domain – Position of RS in time domain is fixed: symbols 0 and 4 of the PRB– Each RB reserves REs for 4, 8, or 12 RS depending on whether this is 1, 2, or 4 antenna ports, respectively

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PCI PlanningImpact in Reference Signal Positions (2/2)• RS in frequency domain can have 6 different positions per PRB across two groups

– RS positions are repeated after two consecutive Groups

Physical Layer Cell Identity = (3 × NID1) + NID2

NID1: Physical Layer Cell Identity group. Determined by SSS sequence. Range 0 to 167

NID2: Identity within the group. Determined by PSS sequence. Range 0 to 2

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Resource elements allocated to Reference Signals

PCI PlanningModule 3 Rule

Rule: • Avoid assigning to the cells of one eNB PCIs with the same module 3

Reason:

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Reason:• PSS defines NID2. There are 3 NID2 in a group so PSS is generated using 1 of 3 different sequences• If two cells of the same eNB have the same mod3(PCI) it means they have the same NID2 (i.e. 0, 1 or 2)

and the same PSS sequence – PSS is used in cell search and synchronization procedures: Different PSS sequences facilitate cell

search and synch procedures

PCI PlanningMIMO 2x2

• When using 2 antennas the number of RS is doubled

• The position of the RS within each antenna pair (Ant0, Ant1) is fixed

• With MIMO case, not following mod3(PCI) implies RS occupies the same REs

• RS SINR is poor reducing the

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• RS SINR is poor reducing the achievable throughput

RE used as RS in Ant0 are unused in Ant1 and vice-versa

PCI Planning‘Module 3’ Rule•Module 3 rule should be extended to the neighbour cells outside the same eNB

– Difficult to avoid mod3 collision in real networks as Mod3 is limited to 3 values (e.g. the cells of the same 3 sector site)

FDD case:• eNBs are not frame synchronised so even if two neighbour cells from different eNBs transmit the same

PSS sequence it is likely that they don’t interfere in time

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TDD case:• Frame synchronised: Bad SNR from RS if inter-site cells have same mod3(PCI)• Tests show DL throughput is affected. Solution: Good planning to reduce overlapping areas

• Trade off: RS-RS interference vs. RS-PDSCH interference– RS-RS interference: causes channel estimation degradation -> affects throughput– RS-PDSCH interference: causes data symbol puncturing lowering effective coding rate -> PDSCH throughput is

also affected

TD-LTE PCI mod3 overlap between sites

•Test between 2 sites with one cell each•Original PCIs (left) where changed to PCIs (right) so both sites have same mod3 (PCI)=1

Effects: • SINR reduction: 17 to -2dB

Original scenario: PCI 45 and PCI47

Modified scenario: PCI 400 and PCI403

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• SINR reduction: 17 to -2dB• Throughput is only reduced from

17Mbps to ~14Mbps

• More info: LTE Optimization Training (RF measurement and Optimization chapter):

• https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/426475080

Impact of PCImod3 collision on tput, TD -LTE

• Case: UE at the border of two cells who have the sa me PCImod3, RSRP from both cells = -67dBm in both measurement cases (only PCI changed)

• NSN 7210 TD dongle, 2.6GHz, 10MHz bandwidth

10

12

14

16

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0

2

4

6

8

10

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53

tput

, Mbp

s

seconds

no PCImod3 collision

PCImod3 collision

PCI Planning‘Module 6’ Rule

Rule: • If mod3(PCI) can’t be fulfilled, avoid assigning the same mod6(PCI) to the cells of the same site

Reason:• 1Tx case: PSS sequence is not unique within the cells of a site but its position the in frequency domain is

still different -> not RS interference

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• 2Tx case: RS to RS interference can not be avoided. The only way to avoid it when using MIMO2x2 is with the mod3(PCI) rule

Summary:• For 2Tx case the cells of the same site should have different mod3 (PCI). For 1Tx case the mod6(PCI)

should be different

• Reason: To have frequency shifts for RS of different cells as they are frame-synchronized (cells of the same site) and avoid RS interference in DL.

PCI Planning: ‘Module30’ Rule‘Module 30’ Rule: • If mod6(PCI) can’t be fulfilled, avoid assigning the same module30(PCI) to the cells of the same site

Reason: •mod30 is required in other planning areas like the UL Demodulation reference signal planning

Example

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Example•There are 30 groups of sequences ‘u’ for PUSCH. Each cell within a site should have sequences from different groups •If the PCIs for cells of the same site have different mod30 then ‘u’ (group sequence number) is different and it is not necessary to plan the grpAssigPUSCH parameter

( ) 30modSCHgrpAssigPU+= PCIu

PCI PlanningRecommendations, wrap up

In priority order, number 1 most important (all four should be fulfilled, ideally)

1. Avoid assigning the same PCI to neighbour cells

2. Avoid assigning the same mod3 (PCI) to ‘neighbour’ cells

Id = 5

Id = 4

Id = 3Id = 11

Id = 10

Id = 9

Id = 8

Id = 7

Id = 6Id = 2

Id = 1

Id = 0

Example 1 PCI Identity Plan

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‘neighbour’ cells

3. Avoid assigning the same mod6(PCI) to ‘neighbour’ cells

4. Avoid assigning the same mod30 (PCI) to ‘neighbour’ cells

Example 2 PCI Identity Plan

PCI Planning6 sector sites• In 6 sectors sites is not possible to assign PCIs with different module 3 as we have 6 cells and only 3

different possibilities

• If increasing sectorisation (from 3 to 6 sectors) then every second group of identities should be allocated within the initial plan

– To allow eNodeB to be allocated identities from two adjacent groups when the number of cells is increased from 3 to 6

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Rule:•Planning should be done assigning PCIs from two consecutive groups and avoi ding that the consecutive cell (i+1) has the same module 3(PCI) •By assigning PCIs from two consecutive groups the ‘module6’ rule is followed

PCI Planning Methods

•Manual• Valid for small amount of sites (e.g. trials)

• No need for additional tools, just follow the rules considering the site distance and cell azimuths• phyCellID parameter is needed in the data fill

• Atoll or other planning tools (e.g. Asset)• PCI planning supported

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• PCI planning supported

• NetAct Optimizer• PCI planning together with other SON features planning like PRACH management

• NSN Internal tools (e.g. Alpha)• PCI planning and UL DM RS planning: • https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/434150579

PRACH Planning

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PRACH PlanningPrinciplePRACH configuration two cells must be different wit hin the PRACH re-use distance to increase the RACH decoding success rate

PRACH transmission can be separated by:

• Time (prachConfIndex)– PRACH-PUSCH interference: If PRACH resources are separated in time within eNB– PRACH-PRACH interference: If same PRACH resources are used for the cells of an eNodeB. – PRACH-PRACH interference is preferred to PRACH-PUSCH interference so prachConfIndex of the cells on one

site should be the same

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• Frequency (prachFreqOff)– Allocation of PRACH area should be next to PUCCH area either at upper or lower border of frequency band,

however should not overlap with PUCCH area– Avoid separation of PUSCH in two areas by PRACH (scheduler can only handle one PUSCH area)– For simplicity use same configuration for all cells

• Sequence (PRACH CS and RootSeqIndex)– Use different sequences for all neighbour cells

Preamble Formats• 3GPP (TS36.211) specifies 4 random access formats for FDD and TDD plus an additional format

(Format 4) specific for TDD that uses the UpPTS

• FDD: Only Formats 0 and 1 are supported in initial releases (up to RL30)

• TDD: Only Formats 0 ,1, 2 and 4 are supported in RL15TD

Recommendation:

UpPTS: Uplink Pilot Timeslot. TDD specific

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Recommendation: • Select Format0 for cell ranges

<14.53 km • Select Format1 for cell ranges

<77.34 km• Select Format2 for cell ranges <29

km (TDD only)• Select Format4 for cell ranges

<1.4 km (TDD only)

km4.12

1031038.9 86

=⋅⋅⋅ −

Preamble Format 4TDD-only

• 3GPP (TS36.211) specifies a special random access format 4 for TDD• Preamble format 4 is allocated in UpPTS increasing the UL throughput as more resources can be

reserved in the normal UL subframes for PUSCH

sT µ5.14CP = sT µ133SEQ =

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• Maximum cell radius with preamble format 4 is about 1.4km • Restrictions when using preamble format 4:

• Only root sequences 0-137 are allowed ( rootSeqIndex 0….137)• Allowed values of prachCS are 4...6. Setting prachCS =6 gives the maximum cel l range

<1.4km• prachFreqOff must be set to 0 with preamble format 4• prachHsFlag must be set to false with preamble format 4

PRACH Configuration IndexprachConfIndex (FDD)• The parameter defines the Allowed System

Frame for random access attempts, the Sub-frame numbers for random access attempts and the Preamble format

• Supported values in RL10 up to RL30:– For Preamble Format 0: 3 to 8– For Preamble Format 1: 19 to 24

Extract of the random access preamble configurations table (only for supported preamble formats 0 and 1)

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• RACH Density indicates how many RACH resources are per 10ms frame.

• Only RACH density values of 1 and 2 are supported up to RL30.E.g.– RACH density=1 Only one random access

attempt per frame – RACH density=2 Two random access attempts

per frame

Recommendation: Configure the same PRACH configuration Indexes at cells belonging to the same site . E.g.: � 3 or 4 or 5 if RACH density=1 and 6 or 7or 8 if

RACH density=2 (Preamble Format 0)

PRACH Configuration IndexprachConfIndex (TDD)

Supported values in RL15TD:• Preamble Format 0: 3 to 7• Preamble Format 1: 23 to 25• Preamble Format 2: 33 to 35• Preamble Format 4: 51 to 53

Restrictions:• If tddFrameConf=1 no limitation for

prachConfIndex•

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Recommendation: Configure the same PRACH configuration Indexes at cells belonging to t he same site . E.g.:

� 3 if tddFrameConf=1 and Preamble Format 0

• If tddFrameConf=2, prachConfIndex is limited to 3, 4 and 6 or 51 to 53

• If tddSpecSubfConf is set to ‘7’ (ssp7), prachConfIndex is restricted to 3…7 or 51…53

• If tddSpecSubfConf is set to ‘5’ (ssp5) prachConfIndex is not restricted

RACH Density

• Based on the expected RACH procedures per second and the maximum collision probability of the RACH preambles it is possible to estimate the RACH density as follows:

100*1001ln*64*)1(

)__(

−−=

UEcollp

LoadRachexx

UEp

• Recommendation: use PRACH density 1 for start

• Since PRACH performance measurement counters are av ailable it will be possible to evaluate the amount of PRACH / RACH procedures in time and adapt /optimize the settings

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UEcollpprocedures in time and adapt /optimize the settings

• Features: RL30 PRACH Management SON feature: an aspect of this feature is to adjust the PRACH density to the traffic in the cell -> not in RL30

PRACH Frequency OffsetprachFreqOff•Indicates the first PRB available for PRACH in the UL frequency band• PRACH area (6 PRBs) should be next to PUCCH area either at upper or lower border of frequency band

to maximize the PUSCH area but not overlap with PUCCH area• Parameter is configured based on the PUCCH region i.e. its value depends on how many PUCCH

resources are available.

• If PRACH area is placed at the lower border of UL frequency band then:

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PRACH-Frequency Offset= roundup [PUCCH resources/2]

• If PRACH area is placed at the upper border of the UL frequency band then:

PRACH-Frequency Offset= NRB -6- roundup [PUCCH resources/2]

• TDD specific : prachFreqOff =0 when preamble format 4 is used

NRB: Number of Resource Blocks

PRACH Cyclic ShiftPrachCS• PrachCS defines the configuration used for the preamble generation. i.e. how many cyclic shifts are

needed to generate the preamble

• PrachCS depends on the cell size – Different cell ranges correspond to different PrachCS

• Simplification: To assume all cells have same size (limited by the prachConfIndex)

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Recommendation: Select PrachCS based on the cell range E.g. if estimated cell range is 15km then PrachCS: 12If all cells in the network are assumed to have sam e cell range them PrachCS is the same for the whole network

PrachCS and rootSeqIndexFormats 0, 1 and 2

• PrachCS defines the number of cyclic shifts (in terms of number of samples) used to generate multiple preamble sequences from a single root sequence

• Example based on PrachCS=12 -> number of cyclic shifts: 119 – Root sequence length is 839 so a cyclic shift of 119

samples allows ROUNDDOWN (839/119)= 7 cyclic shifts before making a complete rotation (signatures per root sequence)

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sequence)

• 64 preambles are transmitted in the PRACH frame. If one root is not enough to generate all 64 preambles then more root sequences are necessary– To ensure having 64 preamble sequences within the cell it

is necessary to have ROUNDUP (64/7)= 10 root sequences per cell Preamble formats 0 ,1 and 2

PrachCS and rootSeqIndexTDD specific (Format 4)

• PrachCS defines the number of cyclic shifts (in terms of number of samples) used to generate multiple preamble sequences from a single root sequ ence

• Example based on PrachCS=6 -> number of cyclic shifts: 15 – Root sequence length for preamble 4 is 139 so a cyclic shift of 15 samples allows ROUNDDOWN (139/15)= 9

cyclic shifts before making a complete rotation (signatures per root sequence)

• 64 preambles are transmitted in the PRACH frame. If one root is not enough to generate all 64 preambles then more root sequences are necessary– To ensure having 64 preamble sequences within the cell it is necessary to have ROUNDUP (64/9)= 8 root

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– To ensure having 64 preamble sequences within the cell it is necessary to have ROUNDUP (64/9)= 8 root sequences per cell

Preamble format 4

PRACH Cyclic ShiftrootSeqIndex

• RootSeqIndex points to the first root sequence to be used when generating the set of 64 preamble sequences.

• Each logical rootSeqIndex is associated with a single physical root sequence number.

• In case more than one root sequence is necessary the consecutive number is selected until the full set is generated

Logical root sequence number

Physical root sequence index (in increasing order o f the corresponding logical sequence number)

0–23 129, 710, 140, 699, 120, 719, 210, 629, 168, 671, 84, 755, 105, 734, 93, 746, 70, 769, 60, 7792, 837, 1, 838

24–29 56, 783, 112, 727, 148, 691

30–35 80, 759, 42, 797, 40, 799

Extract from 3GPP TS 36.211 Table 5.7.2.-4 ( Preamb le Formats 0-3). Mapping between logical and physical root sequences.

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until the full set is generated36–41 35, 804, 73, 766, 146, 693

42–51 31, 808, 28, 811, 30, 809, 27, 812, 29, 810

52–63 24, 815, 48, 791, 68, 771, 74, 765, 178, 661, 136, 703

…. …..

64–75 86, 753, 78, 761, 43, 796, 39, 800, 20, 819, 21, 818

810–815 309, 530, 265, 574, 233, 606

816–819 367, 472, 296, 543

820–837 336, 503, 305, 534, 373, 466, 280, 559, 279, 560, 419, 420, 240, 599, 258, 581, 229, 610

Recommendation: Use different rootSeqIndex across neighbouring cells means to ensure neighbour cells will use different preamble sequences

TDD specific : rootSeqIndex is limited to 0…137 when preamble format 4 is used

PRACH Cyclic ShiftrootSeqIndex (TDD specific)

• Same recommendation applies in case of TDD– Use different rootSeqIndex across neighbouring cells means to ensure neighbour cells

will use different preamble sequences • Differences are:

– rootSeqIndex is limited to 0…137 when preamble format 4 is used– the table for mapping of logical to physical root sequence numbers:

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Extract from 3GPP TS 36.211 Table 5.7.2.-5 ( Preamb le Formats 4). Mapping between logical and physical root sequences.

PRACH PlanningWrap UpSteps: - Define the prachConfIndex

• Depends on preamble format (cell range)• It should be the same for each cell of a site

- Define the prachFreqOff• Depends on the PUCCH region• It can be assumed to be the same for all cells of a network (simplification)

- Define the prachCS

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- Define the prachCS• Depends on the cell range• If for simplicity same cell range is assumed for all network then prachCS is the same for all cells

- Define the rootSeqIndex• It points to the first root sequence • It needs to be different for neighbour cells• rootSeqIndex separation between cells depends on how many are necessary per cell (depends on

PrachCS)

Exercise

• Plan the PRACH Parameters for the sites attached in the excel

• Assumptions:

– PUCCH resources = 7– Cell range = 5 km (all cells have same

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– Cell range = 5 km (all cells have same range)

– One PRACH opportunity for 10ms

– 20MH BW– FDD

PRACH planning exercise

PRACH Management Feature (LTE 581)RL30 and RL25TD• Automatic assignment of PRACH parameters during the initial eNB auto-configuration process using

NetAct Optimizer (i.e. PRACH auto planning):

• prachConfIndex• prachFreqOff

• Assignment done for all cells of an eNB considering own cell data and configuration data from ‘surrounding’ eNBs

• prachCS• rootSeqIndex

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Feature delimitation• No PRACH / RACH optimization Based e.g. on counter or PM counter results• In RL30 runs only once during initial auto-configuration process: only new eNBs in planned state can

use it . It is not possible for actual (upgraded) RL30 eNBs

Benefit• No manual PRACH planning for new eNBs/cells required

More info: https://sharenet-ims.inside.nokiasiemensnetworks.co m/Overview/D433080674

- UlseqHop

UL Reference Signal Planning

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- UlseqHop- UlGrpHop- grpAssigPUSCH- ulRsCs- Sequence Group Number (u)

UL Reference SignalOverviewTypes of UL Reference Signals• Demodulation Reference Signals (DM RS)

– PUSCH/PUCCH data estimation

• Sounding Reference Signals (SRS)– Mainly UL channel estimation UL (RL40)

DM RS is characterised by:

UL DM RS allocation per slot for Normal Cyclic Prefix

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DM RS is characterised by:• Sequence (Zadoff Chu codes)

• Sequence length: equal to the # of subcarriers used for PUSCH transmission

• Sequence group:� 30 options� Cell specific parameter

• Cyclic Shift: UE and cell specific parameter

UL DM Reference SignalNeed for Planning

Issue:• DM RS occupy always the same slot in time domain• In frequency domain DM RS of a given UE occupies the

same PRBs as its PUSCH/PUCCH data transmission• Possible inter cell interference for RS due to simultaneous

UL allocations on neighbour cells– No intra cell interference because users are separated

in frequency

UL DM RS allocation per slot for Normal Cyclic Prefix

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in frequency– Possible inter cell interference

Scope of planning:• DM RS in co-sited cells needs to be different

TDD case: Since sites are frame synchronised cells should be planned as if they were sectors of the same site. Same recommendation as for FDD applies.

• UL reference signal sequences in LTE are of form:

Where:• n : frequency index. Depends on #PRBs allocated• phi(n): Phase-shift function specified as:

– 3 or more PRBs: extended ZC sequences

number of RBs

3 4 5

Nzc 31 47 59

0 1 2 21 2 3 42 3 5 63 4 6 84 5 8 105 6 9 116 7 11 137 8 12 158 9 14 179 10 15 1910 11 17 2111 12 18 2312 13 20 2513 14 21 2714 15 23 29

seq id, u

q

UL RS SequenceRS Sequence Groups

( )njenr πφ=)(

( ) ( )zcN

nnqn

1+=φ

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– Nzc: prime number– Index n is wrapped around to extend the sequence length to a

multiple of 12

• Example: ZC seq id u=10 for PRB length 5 is generated as (q=21)

14 15 23 2915 16 24 3016 17 26 3217 18 27 3418 19 29 3619 20 30 3820 21 32 4021 22 33 4222 23 35 4423 24 36 4624 25 38 4825 26 39 4926 27 41 5127 28 42 5328 29 44 5529 30 45 57

Zadoff Chu Sequences for PRBs 3, 4 and 5

( ) ( )0,58,57,...,1,0,

59

121 =+= n

nnnφ

The cyclic extension (index wrap-around) is needed to make a sequence length of 5x12=60 from ZC sequence length of 59

• RS sequences for PUSCH have different lengths depending the UL bandwidth allocated for a UE

• 30 possible sequences for each PRB allocation length of 1-100 PRBs• Sequences are grouped into 30 groups so they can be assigned to cells• Sequence group number ‘u’:

RS Sequences and RS Sequence Groups Sequence Group Id, ‘u’


grpAssigPUSCH : group assignment for PUSCH Range [0…29], step 1

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Cyclic Shift• Additional sequences can be derived from a basic sequence by applying a cyclic shift• Cyclic shifts of an extended ZC sequence are not fully orthogonal, but have low cross-

correlation• The actual UL reference signal cyclic shift ncs used by UE is different for every 0.5ms time

slot

[ ] 12mod)( sPRS)2(

DMRS)1(

DMRScs nnnnn ++=

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Cell-specific static cyclic shift defined by LNCEL/ulRsCs and broadcast on BCCH

TTI-specific cyclic shift signalled to UE on PDCCH DCI0 in each uplink scheduling grant (defined by scheduler)

Pseudorandom cyclic shift offset that changes every time slot. Depends on the PCI, slot number ns and u via LNCEL/grpAssigPUSCH

ulRsCs ndmrs10 01 22 33 44 65 86 97 10

DCI0 CS field

ndmrs2

000 0001 6010 3011 4100 2101 8110 10111 9

uN

c +⋅

= 32

30

cellID

init

UL DM Reference SignalHopping Techniques• Sequence Hopping

– Intra-Subframe hopping between two sequences within a sequence group for allocations larger than 5PRBs

– Only enabled is Sequence Group hopping in disabled

– Not enabled in RL10/RL20/RL30: ulSeqHop= false

• Sequence Group Hopping

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– In each slot, the UL RS sequences to use within a cell are taken from one specific group– If group varies between slots: Group hopping

– Group Hopping not enabled in RL10/RL20/RL30: UlGrpHop = false� Group is the same for all slots

• Cyclic Shift Hopping– Always used– Cell specific cyclic shift added on top of UE specific cyclic shift

PlanningFrom Theory to Practice… (1/2)Theory:• It should be possible to assign to the cells of one site the same sequence group ‘u’ and ‘differentiate’

the sequences using different cell specific cyclic shifts i.e. allocating different ulRsCs

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Remember!: Cyclic shifts of an extended ZC sequence are not fully orthogonal, but have low cross-correlation

PlanningFrom Theory to Practice… (2/2)Practice:• It doesn’t seem to work

• UL Throughput gets considerably affected if UL traffic in neighbour cell– From 40 Mbps to ~ 22 Mbps in the example

PCI grpAssigPusch sequence id u ulRsCs cinit75 0 15 0 7976 29 15 4 79

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PlanningNew rule• Allocate different sequence group u for every cell, including cells of the same site

– Cross-correlation properties between sequences from two different groups are good because of sequence grouping in the 3GPP spec

• ulRsCs does not matter (it is only relevant for sequences within one seq group u)

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Planning Results• UL Throughput still suffers from UL interference in neighbour cell but the effect is lower

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PCI grpAssigPusch sequence id u ulRsCs cinit75 0 15 0 7976 0 16 0 80

Pros an cons of the ‘new’ planning rule

• [+]: Results seem to be better• [+]: Less parameters to plan, only PCI planning needed

– UlRsCs only relevant when using sequences of the same group

– ‘u’ will be different if PCI module 3 rule is followed. In that case ‘grpAssigPUSCH ’ value is not relevant

( )+=

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• [-]: Reduced group reuse distance compared to the case of assigning the same group per each site


UL DM RS PlanningWrap up• Principle: DM RS needs to be different in cells of the same eNodeB• Current planning approach:

– Assign different sequence group number ‘u’ to the c ells of the same site . Range: [0…29]. grpAssigPUSCH can be constant =no need for planning


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– If cells of the site follow the PCImod3 rule, the sequence group number ‘u’ will be different

– If PCImod3 rule is not followed, check PCImod30 rule � If problems use grpAssigPUSCH to differentiate the ‘u’ - sequence group number-

– If same ‘u’ has to be used in neighbouring cells and cannot be changed using grpAssigPUSCH then assign different ulRsCs to the cells of a site. Range [0…7]

UL DM RS Planning example•Using grpAssigPUSCH to tune PCI based sequence allocation in case of PCImod30 collision

Delta_ SS = grpAssigPUSCH

If grpAssigPUSCH=0 then u=0 interfering

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then u=0 interfering with the cell below. grpAssigPUSCH is used to avoid this

Tracking Area Planning

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Introduction (1/2)

• When the UE is in idle mode its location is known by the MME with the accuracy of a tracking area

• Each eNodeB can contain cells belonging to different tracking areas

• One cell only belongs to one tracking area code (TAC)

• A tracking area can be shared by multiple MME

• Tracking Area Identity (TAI) = PLMN ID (mcc, mnc) + TAC all broadcasted in SIB1

• Reserved TAC values: 0000 and FFFE( in hex) i.e. 0 and 65534

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S1 Application Protocol Paging Message extracted from 3GPP TS 36.413

Tracking areas are the equivalent of Location Areas and Routing Areas for LTE

Introduction (2/2)

• The normal tracking area updating procedure is used when a UE moves into a tracking area within which it is not registered

• The periodic tracking area updating procedure is used to periodically notify the availability of the UE to the network (based upon T3412)

• Tracking area updates are also used for Further details in 3GPP

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• registration during inter-system changes

• MME load balancing

Further details in 3GPP TS 24.301

• Large tracking areas result in• Increased paging load• Reduced requirement for tracking area updates resul ting from mobility

Planning Guidelines• Tracking areas should be planned to be relatively large (100 eNodeB, 3 cells/eNodeB) rather than

relatively small

• Their size should be reduced subsequently if the paging load becomes high

• Tracking areas should not run close to and parallel to major roads nor railways. Likewise, boundaries should not traverse dense subscriber areas

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• Cells which are located at a tracking area boundary and which experience large numbers of updates should be monitored to evaluate the impact of the update procedures

• Existing 2G and 3G location area should be used as a basis for defining LTE tracking area boundaries

Tracking Area Lists

• A UE can be registered in multiple tracking areas to avoid unnecessary tracking areas updates at the tracking area borders. This is done via the TA list i.e. a list of allowed TA delivered to the UE in the attach and TAU procedures

• TA list can contain a maximum of 16 different tracking area identities (TAI)

• MME supports maximum 8000 TA lists

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• The TA list is configured in the MME TA1LSTNX.xml file

• If the same TAI belongs to multiple TA Lists. The MME will send to the UE (during attach or TAU) the TA List with lowest value

Example of TA1LSTNX.xml file showing two TAI

• Unclear if TA List configuration is radio planning or EPC task

Tracking Area PlanningRAN sharing case•In case of RAN sharing, recommendation of re-using existing LA from 3G/2G is not valid as TAC is the same for all PLMN Ids

• LNCEL: tac has multiplicity one i.e. no multiple entries possible

• LNCEL: furtherPlmndIdL allows up to 5 entries• Together with primary PLMN ID (LNBTS: mcc, mnc & mncLength) there can be up to 6 PLMN Ids)

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• Feature RAN sharing Multi Operator Core Network (MOCN-LTE4) currently supports only 2 PLMNs • Planned Feature RL50 (LTE1051) will support up to 6 operators MOCN

Thank You

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4.1 planning for network integration

Documents