### Abstract

Multiple-access interference (MAI) depends on chip pulse shapes in chip-asynchronous direct sequence/code division multiple access (DS/CDMA) systems. The mean squared MAI averaged over relative time delays is expressed in a quadratic form, where a coefficient matrix is derived from the pulse shapes, while a variable vector consists of aperiodic autocorrelation functions of the signature sequences. This quadratic form gives a lower bound of the mean squared MAI, which is equivalent to the Welch bound if the pulse shape is a delta function. For any continuous pulse shapes, however, the mean squared MAI is shown to be reduced beyond the Welch bound. In case of rectangular pulse, the mean squared MAI is reduced by 13.4%, whereas the reduction ratio is 5.2% for band-limited pulses with excess bandwidth 0.5.

Original language | English |
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Title of host publication | Proceedings - 2006 IEEE International Symposium on Information Theory, ISIT 2006 |

Pages | 1524-1528 |

Number of pages | 5 |

DOIs | |

Publication status | Published - Dec 1 2006 |

Event | 2006 IEEE International Symposium on Information Theory, ISIT 2006 - Seattle, WA, United States Duration: Jul 9 2006 → Jul 14 2006 |

### Publication series

Name | IEEE International Symposium on Information Theory - Proceedings |
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ISSN (Print) | 2157-8101 |

### Other

Other | 2006 IEEE International Symposium on Information Theory, ISIT 2006 |
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Country | United States |

City | Seattle, WA |

Period | 7/9/06 → 7/14/06 |

### Fingerprint

### All Science Journal Classification (ASJC) codes

- Theoretical Computer Science
- Information Systems
- Modelling and Simulation
- Applied Mathematics

### Cite this

*Proceedings - 2006 IEEE International Symposium on Information Theory, ISIT 2006*(pp. 1524-1528). [4036222] (IEEE International Symposium on Information Theory - Proceedings). https://doi.org/10.1109/ISIT.2006.262123

**A lower bound on the mean squared correlations for band-limited asynchronous DS/CDMA systems.** / Jitsumatsu, Yutaka; Kohda, Tohru.

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

*Proceedings - 2006 IEEE International Symposium on Information Theory, ISIT 2006.*, 4036222, IEEE International Symposium on Information Theory - Proceedings, pp. 1524-1528, 2006 IEEE International Symposium on Information Theory, ISIT 2006, Seattle, WA, United States, 7/9/06. https://doi.org/10.1109/ISIT.2006.262123

}

TY - GEN

T1 - A lower bound on the mean squared correlations for band-limited asynchronous DS/CDMA systems

AU - Jitsumatsu, Yutaka

AU - Kohda, Tohru

PY - 2006/12/1

Y1 - 2006/12/1

N2 - Multiple-access interference (MAI) depends on chip pulse shapes in chip-asynchronous direct sequence/code division multiple access (DS/CDMA) systems. The mean squared MAI averaged over relative time delays is expressed in a quadratic form, where a coefficient matrix is derived from the pulse shapes, while a variable vector consists of aperiodic autocorrelation functions of the signature sequences. This quadratic form gives a lower bound of the mean squared MAI, which is equivalent to the Welch bound if the pulse shape is a delta function. For any continuous pulse shapes, however, the mean squared MAI is shown to be reduced beyond the Welch bound. In case of rectangular pulse, the mean squared MAI is reduced by 13.4%, whereas the reduction ratio is 5.2% for band-limited pulses with excess bandwidth 0.5.

AB - Multiple-access interference (MAI) depends on chip pulse shapes in chip-asynchronous direct sequence/code division multiple access (DS/CDMA) systems. The mean squared MAI averaged over relative time delays is expressed in a quadratic form, where a coefficient matrix is derived from the pulse shapes, while a variable vector consists of aperiodic autocorrelation functions of the signature sequences. This quadratic form gives a lower bound of the mean squared MAI, which is equivalent to the Welch bound if the pulse shape is a delta function. For any continuous pulse shapes, however, the mean squared MAI is shown to be reduced beyond the Welch bound. In case of rectangular pulse, the mean squared MAI is reduced by 13.4%, whereas the reduction ratio is 5.2% for band-limited pulses with excess bandwidth 0.5.

UR - http://www.scopus.com/inward/record.url?scp=34547261931&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34547261931&partnerID=8YFLogxK

U2 - 10.1109/ISIT.2006.262123

DO - 10.1109/ISIT.2006.262123

M3 - Conference contribution

SN - 1424405041

SN - 9781424405046

T3 - IEEE International Symposium on Information Theory - Proceedings

SP - 1524

EP - 1528

BT - Proceedings - 2006 IEEE International Symposium on Information Theory, ISIT 2006

ER -