Cooperative Water Filling (CoopWF) Algorithm for Small Cell Networks

International Conference on ICT Convergence 2013

Toha Ardi Nugraha, Soo Young Shin

Department of IT Convergence, Kumoh National Institute of Technology

This paper proposes a new power allocation algorithm withpre-coding in cooperative small cell networks (SCNs). Apower allocation algorithm based on cooperative water-filling (CoopWF) is proposed and block diagonalization (BD)precoding is adopted to cancel the inter-user interferences.The proposed scheme is easily implementable to SCNs suchas femto-cell, metro-cell, and pico-cell. Simulation resultsshow that the proposed CoopWF algorithm provides bettermean capacity compared to the existing power allocationalgorithm.

Abstract

• Small cell network (SCN) such as femto-cell, metro-cell or pico-cell is aneffective solution for increasing the capacity of wireless communicationsystems especially in the indoor public areas.

• SCN is generally implemented via a optical fiber backbone and allows areliable fast exchange of information among SCNs

• In SCN, a cooperative communication can be easily implemented.• Cooperative communication is an effective strategy to mitigate inter- cell

interference and also it can dramatically improve the system performance

Problem Statement

• A power allocation algorithm based on cooperative water-filling (CoopWF) is proposed and block diagonalization (BD)precoding is adopted

• This paper propose cooperative power allocation algorithmwith BD precoding for small cell networks.

• The proposed algorithm is implemented and simulated in themulti-user MIMO (MU-MIMO) SCN to measure the meansystem capacity.

Objectives

• Cooperative communication can be represented by Multi-cell MIMO system model asshown in Fig.1

• Several small cells having Nt transmit antennas and uj user equipment's (UEs) havingNr receive antennas.

• The two users are randomly located within the overlapping of the cell edge zone (seeFig.1) with the radius of each small cell (R) is 20 meter.

• The indoor path-loss, for a small cell is modeled as a modified COST-231 indoorpropagation model.

• The received signal at the uj UE is given by

• The received signal for the user uj after BD is

Cooperative Water Filling

The paper evaluate the performance ofthe cooperative small cells with thenumber of C = 2 and 3 as shown in Fig.1

The number of antennas at each small cell astransmitter Nt = 2 and each user device asreceiver is equipped with Nr = 2 antennas.

Small Cell Network Architectures

When SNR is 0 dB, the meancapacity of our proposealgorithm with C=3 cellsimproved about 0.3 Mbpscompare to the previousalgorithm with the samenumber of cooperative smallcell networks.

Simulation Result

This paper proposes a power allocation algorithm with blockdiagonalization (BD) precoding in cooperative small cell networks.The proposed scheme is easily implementable to small cell networkssuch as femtocell, metro-cell, and pico-cell. In our simulation result,we have shown that the proposed algorithm could improve meancapacity. The simulation result is in line with the concept of waterfilling that improved spectral efficiency on the low SNR. From thesimulation result, when SNR is -10 dB until 0 dB, the mean capacity ofour propose algorithm with C=3 cells increased about 0.4 Mbpscompare to the previous algorithm with C=3 cells.

Conclusion