### Abstract

In this paper, we propose an iterative lowcomplexity carrier frequency offset (CFO) compensation algorithm based on the conjugate gradient (CG) method for uplink orthogonal frequency division multiple access systems. In general, a linear minimum mean square error (MMSE) CFO compensation algorithm is simple and efficient, but it requires an inverse operation to compute the MMSE solution of the CFOinduced inter-carrier interference (ICI) matrix whose size equals the number of subcarriers. Thus, the computational complexity becomes prohibitively high when the number of subcarriers is large. To address this issue, we employ the iterative CG method to solve linear equations whose matrix is Hermitian positivedefinite. First, we derive the eigenvalue distribution of the CFOinduced ICI matrix. Based on the distribution, we present several observations which lead to the iteration number required for the convergence. Especially, the analysis shows that for an interleaved carrier assignment scheme, the maximum iteration number to compute an exact solution is at most the same as the number of mobile units. Simulation results exhibit that the proposed scheme can yield almost the same bit error rate performance of the MMSE compensation algorithm with substantially reduced computational complexity and memory requirements.

Original language | English |
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Title of host publication | IEEE International Conference on Communications |

DOIs | |

Publication status | Published - 2011 Sep 2 |

Event | 2011 IEEE International Conference on Communications, ICC 2011 - Kyoto, Japan Duration: 2011 Jun 5 → 2011 Jun 9 |

### Other

Other | 2011 IEEE International Conference on Communications, ICC 2011 |
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Country | Japan |

City | Kyoto |

Period | 11/6/5 → 11/6/9 |

### Fingerprint

### ASJC Scopus subject areas

- Electrical and Electronic Engineering
- Computer Networks and Communications

### Cite this

*IEEE International Conference on Communications*[5962693] https://doi.org/10.1109/icc.2011.5962693

**CFO compensation for uplink OFDMA systems with conjugated gradient.** / Lee, Kilbom; Lee, Inkyu.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*IEEE International Conference on Communications.*, 5962693, 2011 IEEE International Conference on Communications, ICC 2011, Kyoto, Japan, 11/6/5. https://doi.org/10.1109/icc.2011.5962693

}

TY - GEN

T1 - CFO compensation for uplink OFDMA systems with conjugated gradient

AU - Lee, Kilbom

AU - Lee, Inkyu

PY - 2011/9/2

Y1 - 2011/9/2

N2 - In this paper, we propose an iterative lowcomplexity carrier frequency offset (CFO) compensation algorithm based on the conjugate gradient (CG) method for uplink orthogonal frequency division multiple access systems. In general, a linear minimum mean square error (MMSE) CFO compensation algorithm is simple and efficient, but it requires an inverse operation to compute the MMSE solution of the CFOinduced inter-carrier interference (ICI) matrix whose size equals the number of subcarriers. Thus, the computational complexity becomes prohibitively high when the number of subcarriers is large. To address this issue, we employ the iterative CG method to solve linear equations whose matrix is Hermitian positivedefinite. First, we derive the eigenvalue distribution of the CFOinduced ICI matrix. Based on the distribution, we present several observations which lead to the iteration number required for the convergence. Especially, the analysis shows that for an interleaved carrier assignment scheme, the maximum iteration number to compute an exact solution is at most the same as the number of mobile units. Simulation results exhibit that the proposed scheme can yield almost the same bit error rate performance of the MMSE compensation algorithm with substantially reduced computational complexity and memory requirements.

AB - In this paper, we propose an iterative lowcomplexity carrier frequency offset (CFO) compensation algorithm based on the conjugate gradient (CG) method for uplink orthogonal frequency division multiple access systems. In general, a linear minimum mean square error (MMSE) CFO compensation algorithm is simple and efficient, but it requires an inverse operation to compute the MMSE solution of the CFOinduced inter-carrier interference (ICI) matrix whose size equals the number of subcarriers. Thus, the computational complexity becomes prohibitively high when the number of subcarriers is large. To address this issue, we employ the iterative CG method to solve linear equations whose matrix is Hermitian positivedefinite. First, we derive the eigenvalue distribution of the CFOinduced ICI matrix. Based on the distribution, we present several observations which lead to the iteration number required for the convergence. Especially, the analysis shows that for an interleaved carrier assignment scheme, the maximum iteration number to compute an exact solution is at most the same as the number of mobile units. Simulation results exhibit that the proposed scheme can yield almost the same bit error rate performance of the MMSE compensation algorithm with substantially reduced computational complexity and memory requirements.

UR - http://www.scopus.com/inward/record.url?scp=80052163724&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=80052163724&partnerID=8YFLogxK

U2 - 10.1109/icc.2011.5962693

DO - 10.1109/icc.2011.5962693

M3 - Conference contribution

SN - 9781612842332

BT - IEEE International Conference on Communications

ER -