9.intelligent underlay overlay

1 © NOKIA 2000 BSSPARS9 Jun 00

Intelligent Underlay Overlay

BSSPAR for S9

INTELLIGENT UNDERLAY OVERLAYTerminology 1/3

• Regular BCCH-TRX

• super-reuse TRX

• different frequence reuse patterns

• Super reuse frequencies form the underlay network where frequencies are reused very intensively to produce the extended capacity

• interference limited dominance areas in super-reuse TRXs

• selection between regular/super-reuse TRXs based on C/I ratio

• call setup to regular TRX

• inter cell HO always to regular TRX

Using Intelligent Underlay-Overlay concept with microcells

• Microcells to hot spots (microcells using only super frequencies are called child cells)

• Calls are established only in the regular TRXs

• Microcell interference is estimated by using closest regular TRX as a reference (compare C/I based handover candidate evaluation)

INTELLIGENT UNDERLAY OVERLAYSuperReuse and Regular frequencies

In order to avoid interference caused by tight frequency reuse, the super reuse frequencies are intended to serve MS which are close to the BTS.

Regular frequency is used when the mobile is further away from the BTS where RxLev would be low and co channel interference high.

trxFrequencyType (FRT) 0 … 16 TRX

Intelligent Underlay-Overlay

Super layer (reuse = e.g. 7)

Regular layer (reuse = 12)

Super layer (reuse = e.g. 7)

Regular layer (reuse = 12)Regular layer (reuse = e.g. 12) Regular layer (reuse = e.g. 12)

Service region of super layer controlled by interference (superReuseGoodCIThreshold)

Call handed over from super layer to regular layer when interference becomes excessive (superReuseBadCIThreshold)

<-------- Interference region ---------->

INTELLIGENT UNDERLAY OVERLAY

OVERLAYREGULAR FREQUENCY

• one TRX used as a super reuse frequency ( f1 )

• f1’ is also a super reuse frequency in the adjacent cell

• one TRX used as a regular frequency ( f4)

• f8 is a regular frequency and is in the adjacent cell to f4

• SuperReuseGoodCIthreshold is 15 dBm

EXAMPLE: HANDOVER TO SUPER REUSE CELL (1/6)

INTERFERENCE

UNDERLAYSUPER REUSE FREQUENCY

EXAMPLE: HANDOVER TO SUPER REUSE CELL (2/6)

• a call on progress

• serving cell frequency is f8

• a mobile moving further from f8

• downlink RXlev measurements:

• f1= -105dBm

• f4= -105 dBm

• f1’= -90 dbm

• f8= -90 dBmf8

INTELLIGENT UNDERLAY OVERLAY EXAMPLE: HANDOVER TO SUPER REUSE CELL (3/6)

• f1= -89dBm

• f4= -89dBm

• f1’= -95 dbm

• f8= -95 dBm

• handover is executed to f4

• Note: f1 can not be chosen, call is always handed over to regular frequency first

• f1= -89dBm

• f4= -89dBm

• f1’= -95 dbm

• f8= -95 dBm

• while getting getting closer to the BTS

• ...f1 is chosen as a handover candidate, because C/I ratio 16 dB (SuperReuseGoodCiThreshold = 15 dB)

• (C/I for f1 is calculated by using f8 as a reference for f’1)

• f1= -80dBm

• f4= -80dBm

• f1’= -96 dbm

• f8= -96 dBm

• call is handed over to f1 (HANDOVER FROM REGULAR TO SUPER)

• f1= -80dBm

• f4= -80dBm

• f1’= -96 dbm

• f8= -96 dBm

INTELLIGENT UNDERLAY OVERLAYCoverage/Capacity concept (1/2)

• RESULT:regular frequencies provide coverage on the edge of the cell

INTELLIGENT UNDERLAY OVERLAY Coverage/Capacity concept (2/2)

• RESULT:regular frequencies provide coverage on the edge of the cell super reuse gives capacity (provided that IUO is deployed properly)

• In regular TRX the C/I ratio is evaluated to all super-reuse groups of own cell and to all groups of neighbour child cells

• In super-reuse TRX the C/I ratio is evaluated only to own super-reuse frequency group. If enableInterFrtIuoHo is used, then also C/I ratio for all super-reuse groups of own cell and to all groups of neighbour child cells is evaluated.

• Assumption: TRX belonging to the same FRT experience same C/I

INTELLIGENT UNDERLAY OVERLAYC/I evaluation(1/4)

regular layer

super layer

regular layer

super layerC/I

INTELLIGENT UNDERLAY OVERLAYC/I evaluation (2/4)

• Directly measured interference level is used when the interfering cell is a regular cell which is adjacent to the serving cell and has the same set of super-reuse frequencies as the serving cell. Also the location of the interfering cell is close enough to cause interference. In this situation, the downlink RXLEV of the interfering cell corresponds directly to the interference level on the super-reuse TRX caused by the interfering cell.

rx_level(f3)

IUO HO f1 <-> f2

interference

CIEstType=0

INTELLIGENT UNDERLAY OVERLAY C/I evaluation (3/4)

•BCCH Frequency of the InterferingCell Cannot be Measured by the MS

•The BCCH is Not a Super ReuseTRX, but has InterferingFrequency

•The BCCH is a Super Reuse TRX( Child Cell )

• A Different Cell has to be Taken asReference Cell

• Reference Cell gives Similar 'FieldStrength Pattern' in the Area

• The Parameter C/IEstType=1

• Parameter LevelAdjustment canbe used for compensation.

BCCH = f 1

Super Reuse Frequency = f 1

BCCH = f 3

• up to 10 interfering cells

INTELLIGENT UNDERLAY OVERLAY C/I evaluation (4/4)

C/I estimation weight (W1 - W10)C/I estimation type (T1 - T10) 0 (meas) / 1 (estim)

0 … 10Level adjustment (L1 - L10) -63 … 63 (dB)

CellIdentificationOfInterferingCell (C1…C10)

LocationAreaCodeOfInterferingCell (LAC 1…10)

superReuseEstMethod AVE / MAX / ICE /NONE HOC

allInterferingCellsAveraged Yes / No

intfCellAvgWindowSize 1 … 32 (SACCH period)

intfCellNbrOfZeroResults 0 … 31 HOC

• Traffic control between regular and super-reuse frequencies:

• Underlay Overlay handover

• Underlay Overlay Assignment (TCH assignment to super TRX)

• Direct Access

• Conventional radio criteria + other reasons than radio criteria (traffic reason

handover, umbrella handover…..)

NOTE: when a call is on a super-reuse TRX, the HO causes Downlink quality,

Downlink interference and Uplink interference are not considered conventional

radio criteria.

INTELLIGENT UNDERLAY OVERLAYHO types (1/10)

HO Caused by Radio Criteria or by other reasons

• the target layer is always regular, therefore:

Intra-cell HO within a regular frequency group (if enableIntraHoInterfUL/DL)

Inter-cell HO from a regular cell (super/regular layer) to another regular cell

(regular layer)

Inter-cell HO from a child cell to a regular (parent) cell (regular layer)

Child cells

regular layer

super layer

regular layer

super layer

Underlay Overlay Handover

• SuperReuseGood/BadCiThreshold comparison

• only possible when C/I of the target cell can be evaluated:

regular layer -----> super layer (intracell )

-----> child (inter cell)

super layer -----> regular layer (intracell)

-----> super layer (intracell, intra or inter FRT (* if enableInterFrtIuoHo))

-----> child (intercell *)

child cell -----> parent cell (regular layer)

-----> child cell

• HO procedure:

Measurement processingC/I evaluationThreshold comparison (suitable target cell selection)target cell selection

(parent cell)

INTELLIGENT UNDERLAY OVERLAY Inter Super-reused Layer Handover

enableInterFrtIuoHo REG Handover between super-reuse frequency groupsis enabled, but a handover back to a regular frequency group is always preferable

DIS Handover between super-reuse frequency groups is disabled

SUP Handover between super-reuse frequency groupsis enabled and it is preferable in case of bad C/I ratio

In order to minimise the number of imperative handovers without degrade of service quality, a handover between the super reused layers (an intra-cell handover) is performed

Other super reuse TRX has to fulfill the C/I requirement

regular layer

super layer

regular layer

super layer

Underlay Overlay handover

Child cells

NOTE: UO handover from child cell -----> super layer of regular cell: not possible !! UO handover from super layer ------> super layer (intercell) : not possible!!

Bad C/I Ratio: CI_RATIO <= SuperReuseBadCiThreshold

• if CI_RATIO(k) >= SuperReuseGoodCiThreshold

AV_RANGE_HO <= msDistanceHoThresholdParam

• enableInterFrtIuoHo = REG or SUP

then ho is triggered to super layer or regular

• else (CI_RATIO(k) < SuperReuseGoodCiThreshold or enableInterFrtIuoHo = DIS or AV_RANGE_HO <= msDistanceHoThresholdParam )

ho is triggered to regular layer

Underlay Overlay handover Call on super layer (regular cell)

regular layer

super layer

regular layer

super layer

Underlay Overlay handover

Child cells

NOTE: UO handover from child cell -----> super layer of regular cell: not possible !! UO handover from super layer ------> super layer (intercell) : not possible!!

Intercell UO ho from super layer ------> regular layer only when no other possibility

• if CI_RATIO(k) >= SuperReuseGoodCiThreshold

AV_RXQUAL_UL/DL < Ho_Threshold_Quality_UL/DL

AV_RANGE_HO <= msDistanceHoThresholdParam

then : if super TRX on regular cell ---> ho triggered

if child ----> AV_RXLEV_NCELL(n) > RxLevMinCell(n) + Max(0,Pa)

PBGT(n) > HoMarginPBGT(n)

Underlay Overlay handover Call on regular layer

• child has priority on super-reuse TRX in regular cell

• child cells ranked according to priority level & load factor, signal strenght, C/I ratio

• super-reuse groups ranked according to C/I ratio

• minBsicDecodeTime

• several Ho reasons: DL interference

DL Quality

Bad C/I Ratio

UL Interference

UL Quality

ms-bs distance (if msDistanceBehaviour other than 0, 255)

Underlay Overlay handover Call on super layer (regular cell or child cell)

• different priorities between target layers according to Ho reasons:

DL interference /DL Quality : ---> regular layer (intracell or parent)

---> super layer (intracell or child)

---> regular layer (imperative intercell HO)

UL interference : ---> super layer (intragroup, if enableIntraHoInterfUL)

----> regular layer (intracell)

---> super layer (intracell or child)

---> regular layer (imperative intercell HO)

Bad C/I Ratio : enableInterFrtIuoHo= REG --->priority to regular layer

SUP ----> priority to super layer

DIS ----> regular layer only

ms-bs Distance: ----> regular layer only

• handover from child cell to parent is imperative, parents ranked according to

• child cells have priority on super-reuse trx (in regular cell)

• childs ranked according to priority & load, signal strenght, C/I ratio

• super-reuse TRXs ranked according to C/I ratio

SDCCH4 Channels7-8 Channels12 Channels…..

Regular Layer6-7 TSL14 TSL22 TSL…..

Super Reuse Layer8 TSL16 TSL24 TSL…..

TCH Assignment to Super-TRX

• When Regular Layer is Congested, TCH Can Be Allocated in the Super Reuse

• Directed Retry

• EnaTchAssignSuper <> 0

• EnaTchAssignSuper Defines a Time for BSIC Decoding of Interfering Cells

• Directed Retry to Other Cells

• Increased Probability of Congestion on the SDCCH ! --- > Feature to Be Used with Care

Call Set-Up

MinBsicDecodeTime

SDCCH4 Channels7-8 Channels12 Channels…..

Regular LayerRegular Layer

Super Reuse Layer8 TSL16 TSL24 TSL…..

Set-Up

MinBsicDecodeTime

EnaTchAssignSuper

DR To Other Cells

enaTchAssSuperIUO 0 … 32 (SACCH period)

minBsicDecodeTime 0 … 128 (SACCH period) HOC

INTELLIGENT UNDERLAY OVERLAYDirect Access to super layer

C/I evaluation by-passed!!

Gives extra capacity and in case the mobile is near to the BTS unnecessary TCH reservation from the regular TRX will be avoided.

BSCregularsuper

Direct Access level

-109……-47 dBmTRX

INTELLIGENT UNDERLAY OVERLAY Direct Access to super layer

During the call setup phase a TCH on a super-reuse TRX (on the regular cell or the child) may be assigned for the call when the downlink signal level on the super-reuse TRX is well above the worst expected interference level:

RXLEVEL_DL > DirectAccessLevel(k)

RX_QUAL_UL/DL < Ho_Threshold_Quality_UL/DL

The parameter directAccessLevel (controlled on transceiver basis) is the level that must be exceeded for the direct access to the super-reuse TRX.

INTELLIGENT UNDERLAY OVERLAY Direct Access to super layer

The BSC may allocate a TCH on a super-reuse TRX for an inter-cell handover attempt if the downlink signal level of the super-reuse TRX is good enough and the cause of the handover attempt is:

- Turn around corner

- Fast/slow moving MS

- Better cell (PBGT or Umbrella)

Two new handover types:

regular layer

super layer

regular layer

super layer

Child cells

Parameters (1/2)

enableInterFrtIuoHo

Parameter Value

REG / SUP / DIS

allInterferingCellsAveraged Yes / No

intfCellAvgWindowSize 1 … 32 (SACCH period)

intfCellNbrOfZeroResults 0 … 31

enaTchAssSuperIUO 1 … 32 (SACCH period)

superReuseEstMethod AVE / MAX / ICE /NONE

minIntIuoHoReqBQ

minIntUnsuccIuoHo

minBsicDecodeTime

0 … 255

0 … 128 (SACCH period)

Parameters (2/2)INTELLIGENT UNDERLAY OVERLAY

C/I estimation weight (W1 - W10)

Parameter Value

C/I estimation type (T1 - T10) 0 (meas) / 1 (estim)

-127 … 127 (dB)superReuseGoodCIThreshold

C/I ratioPxNx

0 … 320 … 32

superReuseBadCIThresholdC/I ratio

-127 … 127 (dB)0 … 320 … 32

0 … 10Level adjustment (L1 - L10) -63 … 63 (dB)

directAccessLeveltrxFrequencyType

N / -47 … -109 (dBm)0 … 16 TRX

INTELLIGENT UNDERLAY OVERLAY with Frequency Hopping : IFH

BCCH BCCH

TCH TCH

TCHTCH

Regular layer

Super-reused layer

f4f5f6

RF Hopping

BCCH BCCH

TCH TCH

TCHTCH

BB Hopping

• Improved radio spectrum efficiency

• Adds the benefits of interference averaging by frequency hopping to the capacity gains of IUO to further boost performance

• Frequency hopping combined with IUO means capacity increase by controlled C/I and decreased reuse pattern

• Applicable for both Radio Frequency and Base Band Hopping

• All the super-reuse TRXs in a cell have to belong to the same IUO frequency group

INTELLIGENT FREQUENCY HOPPING

• Intelligent Frequency Hopping is an optional feature

• Both layers of a sector can be set hopping separately by using regular hopping mode and super hopping mode

• In RF hopping both layers, overlay (regular) and underlay (super), shall have their own mobile allocation (MA) attached

• The parameters for this feature can be modified only when the frequency hopping for intelligent underlay overlay and intelligent underlay overlay are both on

INTELLIGENT FREQUENCY HOPPINGParameters

Parameter Value

BB / RF / NunderlayHoppingMode0 … 621 … 62

underlayMAIOoffsetunderlayMaioStepunderlayMA 0 … 128underlayHSN 0, 1 … 63 BTS

INTELLIGENT UNDERLAY OVERLAYHO types

regular layer

super layer

regular layer

super layer

9.intelligent underlay overlay

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