Strong interference case from an adjacent Femtocell

Document Number: IEEE C80216m-09/0631Date Submitted: 2009-03-02

Source:

Mamadou Kone, Ming-Hung Tao, Ying-Chuan Hsiao Email: itri404759@itri.org.tw ITRI

Venue: IEEE Session #60, Vancouver, CanadaBase Contributions:

Re: CR for tgmsdd

Purpose: Discussion and ApprovalNotice:

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Motivation

• MS under strong interference poses challenging interference mitigation issues

• The Section 17.8 propose some solutions:– MS to report the interference to the serving BS– The serving BS and/or the network may request the

interfering Femtocell BS to mitigate the interference

• However none of this solution addresses the following scenario:– MS may not be able to access the network at all– MS may be able to report but still the communication of

two femto BSs over the air is not defined…

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First case: MS has no access to the network

• Therefore MS cannot report the interference back to its serving BS

Back Haul communication

FBS2

FBS1

MS1

Second case: MS has a weak interference

• MS may be able to report the interference, but the serving BS cannot join with the interfering BS– No air interface between two Femto BSs– If different provider, so no backhaul communication– Which femto BS should block its resource?

Back Haul communicationNo air interface communication

FBS1

MS1 FBS2

First case solution: Use interfering Femto BS

• Femto BS detects an MS A-Preamble over the air– Decode the A-Preamble to find out the serving BS ID – Use the backhaul to communicate with the serving BS to

mitigate interference– If not belonging to the same provider, femtoBS may use

the back haul to inform Macro BS of the matter to resolve the interference issue.

• Propose to make a change of the subsection “17.4.2 Femto BS detection” to solve that matter.

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Second case solution: Use the network to resolve the interference

• A femto BS is informed by its MS of the existence of adjacent interfering femto BS:– Femto BS contact the Macro BS through the back haul– The network is informed of the situation

• The network solve properly this kind of issue by contacting the different femto BS:– Redefine their resources profiles by blocking some to

avoid interference– Contact onf of them to reduce its transmission power if

necessary.

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Suggested Text

Insert the following paragraph into Section 17.8, on page 136.--------Start of Text---------17.4.2 Femtocell BS detection A Femtocell BS may monitor UL signal from an MS which is served by overlay macro BS/

Femtocell BS. The monitoring is initiated by overlay macro BS or femto BS to detect the existence of the MS in its coverage. Then the Femtocell BS can inform the macro BS over the backhaul that the MS is in its coverage and subsequently handover to Femtocell BS or interference mitigation can be accomplished.

17.8 Interference Avoidance and Interference Mitigation

Large interference from an inaccessible Femtocell may trigger the interfering femto BS to report the MS femto BS ID to Macro BS. Then the network may redefine the two femto BS resources configuration and or request to one of them to mitigate the interference by reducing transmission power.

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