Atoll Lte

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Inter-cell Interference Coordination in Atoll LTE

Atoll 2.8.1

October 2009

Forsk 2009 Confidential Do not share without prior permission Slide 2 of 16


Inter-cell interference coordination (ICIC)A means to improve signal quality at cell edges

Useful in co-channel scenarios

Compromise between improved cell-edge C/(I+N) or throughput

Categories of inter-cell interference coordination schemesStatic ICIC

Fractional frequency allocation approach

Fractions of the channel bandwidth allocated to sectors of an eNB

to serve cell-edge users

The allocation does not change over time

F2 F3F1F1

F3 F2

F1

F3 F2

Ch 1

Ch 1 Ch 1 Ch 1



Categories of inter-cell interference coordination schemes (contd.)Dynamic ICIC

Scheduling/Resource allocation approach

Signalling between eNBs

(X2 interface) to identify the resource blocks allocated by each sector to cell-edge users

Interference at cell-edges avoided by allocating different resource blocks to cell-edge users in different sectors

Collisions may be avoided in both frequency and time

Allocation may be adapted over time to match traffic requirements



Inter-cell interference coordination in Atoll LTEDownlink static ICIC based on fractional frequency reuse

Fixed, 1/3rd fractioning of channels in cell-edge areas

Cell-edge area determination based on path loss difference between the best server and the second best server

Fractional frequency allocation linked to PSS ID

Automatic fractional frequency planning possible through automatic physical cell ID allocation



Inter-cell interference coordination in Atoll LTEFixed, 1/3rd fractioning of channels in cell-edge areas

Cell-edge area determination based on path loss difference between the best server and the second best server

User in cell-edge if:

PL2ndBS

PLBS

PLThreshold


Inter-cell interference coordination in Atoll LTEFractional frequency allocation linked to PSS ID

Physical Cell ID (0 to 503) PSS ID (0, 1, 2) and SSS ID (0 to 167)

PSS ID 0 Fraction 0

PSS ID 1 Fraction 1

PSS ID 2 Fraction 2

Fractions of channel bandwidth available for cell-edge users Better C/(I+N)

Entire channel bandwidth available for near-cell users Higher throughput


Fraction 0 (F1)Fraction 0 (F1)

Non fractioned Non fractioned AreaArea

(F1 + F2 + F3)(F1 + F2 + F3)

Fraction 1 (F2)Fraction 1 (F2)Non fractioned Non fractioned

AreaArea(F1 + F2 + F3)(F1 + F2 + F3)

Fraction 2 (F3)Fraction 2 (F3)

Non fractioned Non fractioned AreaArea

(F1 + F2 + F3)(F1 + F2 + F3)



Inter-cell interference coordination in Atoll LTEFractional frequency reuse settings in Atoll LTE

Determines which 1/3rd

of the channel bandwidth is used by the cell

Determines cell-edge areas

ICIC support

Amount of downlink traffic load of cell-edge users

Monte Carlo simulation output or O&M stats



Inter-cell interference coordination in Atoll LTEAutomatic fractional frequency planning

(Automatic Physical Cell ID Allocation)

Based on an iterative cost-based algorithm

Automatic Physical Cell id allocation allocates PSS IDs

Collision between PSS IDs is taken into account in the cost calculation



Inter-cell interference coordination in Atoll LTEAutomatic fractional frequency planning

(Automatic Physical Cell ID Allocation)

Different Physical Cell ID allocation plans are tried and a cost

calculated for each

The best Physical Cell ID allocation plan is the one with the lowest cost

The cost is calculated for cells with the following relations

Neighbours

Distance between cells < min reuse distance



Inter-cell interference coordination in Atoll LTEInterference calculation

For both interfering and interfered cells, the ICIC ratio provides the switching point in time between the ICIC and non-ICIC parts of the frame

The positions of the switching points determines the received interference

From fractional channel to fractional channel

From fractional channel to full channel

From full channel to fractional channel

From full channel to full channel

Interferer switching point Server switching point

Longer ICIC part

(More cell-edge traffic)

Shorter ICIC part

(Less cell-edge traffic)



Inter-cell interference coordination in Atoll LTEVariation of the switching point with ICIC ratio

ICIC ratio: 0%

Switching point at the start of the frame

ICIC ratio: 50%

Switching point at 75% of the frame

ICIC ratio: 100%

Switching point at the end of the frame



Inter-cell interference coordination in Atoll LTEPDSCH C/(I+N) without ICIC



Inter-cell interference coordination in Atoll LTEPDSCH C/(I+N) with ICIC



Inter-cell interference coordination in Atoll LTEDownlink throughput without ICIC



Inter-cell interference coordination in Atoll LTEDownlink throughput with ICIC



Future improvementsStatic inter-cell interference coordination in uplink

Dynamic inter-cell interference coordination

Inter-cell Interference Coordinationin Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTEInter-cell Interference Coordination in Atoll LTE

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