An Adaptive Coverage Adjustment Mechanism for LTE Femtocell

Jui-Ming Chen, Li-Der Chou, Yu-Hong Lin

International Computer Symposium (ICS), 2010

OutlineIntroductionAdaptive coverage adjustment mechanismSimulation results Conclusions

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Introduction

Subscribers’ demand installation means that the femtocell deployment maybe not well planned.

Femtocell owners might turn up or down their femtocells arbitrarily.

A new femtocell uses the same frequency/band with its neighbors, UEs in the overlapped area will suffer from co-channel interference.

The adjacent mobile devices use the same or even adjacent channel, interference might also occurs.

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Adaptive coverage adjustment mechanism

Assume that all femtocells can communicate through backhaul network, such as the femtocell gateway or more upper layer infrastructure.

Due to the femtocells are installed indoor, UEs are assumed to have low mobility.

Cross-tier interference in the research is not considered.

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A. Femtocell initialization and clustering

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A

BC

Neighbor Signal Strength

A 20dbm

B 20dbm

Cluster A

Cluster A

A. Femtocell initialization and clustering

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A

C

Neighbor Signal Strength

A 20dbm

B 20dbm

B

Broadcasting messages through common pilot channel (CPICH), if the UEs in coverage can receive the message, they will respond an ACK with its signal quality, which includes whether the UE can be served, SINR, and user preference to femtocells.

B. Coverage level table

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C. Negotiation algorithm

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In clustering algorithm, when interference occurs, only the linked nodes on the graph should be adjusted at most.

There must be a femtocell FAPI that causes interference. FAPI can try to decrease its coverage level first to mitigate the interference.

The neighbors of FAPI have to decrease their coverage level to mitigate the interference.

C. Negotiation algorithm

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Cluster A

A

C

Neighbor Signal Strength

A 20dbm

B 20dbm

FAPI

C. Negotiation algorithm

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Cluster A

A

C

Neighbor Signal Strength

A 20dbm

B 20dbm

FAPI

To determine the quality of signal, we define a value f represent goodness of the combination.

Value f consider about whether the UE can be served, SINR of UEs, and user preference to femtocells, and the number of dropped user.

C. Negotiation algorithm

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A , f = 5

C, f = 10

B, f = 1

D, f = 9

Simulation results

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Conclusions

The mechanism attempts to mitigate the co-channel interference between femtocells that are deployed without well planned.

ACAM can find proper coverage combinations resulting in better signal quality and less interference over the whole network.

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每週一句The rest of the paper is organized as follows. Section 2

introduces the background … . Section 3 describe the proposed adaptive … . Section 4 … .

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