2011 Fiscal Year Final Research Report
Code design based on dynamical systems theory and its application to digital communications
| Project/Area Number |
20360174
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Communication/Network engineering
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| Research Institution | Kyushu University |
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Principal Investigator |
KOHDA Tohru 九州大学, 大学院・システム情報科学研究院, 特命教授 (20038102)
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| Co-Investigator(Kenkyū-buntansha) |
JITSUMATSU Yutaka 九州大学, 大学院・システム情報科学研究院, 准教授 (60336063)
OGATA Masato 九州産業大学, 工学部, 准教授 (90325548)
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| Project Period (FY) |
2008 – 2011
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| Keywords | カオス力学系 / 擬似直交系列 / 同期確立 / 時間・周波数同時表現 |
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| Research Abstract |
Orthogonal frequency division multiplexing(OFDM) system has attracted a lot of attention in wireless mobile communications, which has drawback that its receiver is sensitive to frequency offset caused by Doppler effect. We proposed quasi-orthogonal multicarrier CDMA system which does not require complete orthogonality between subcarreiers. Based on this result, we propose a Gabor-division(GD) CDMA system which is robust to time and frequency synchronization errors. Such a system has three desirable properties :(1) Markov spreading codes with negative auto-correlation can reduce the variance of multiple access interference(MAI) by a factor of 9/25.(2) Two dimensional code acquisition method estimates time and frequency offsets simultaneously.(3) Joint use of time and frequency domain spreading codes realizes almost flat spectrum. These properties imply that GD-CDMA system can solve the problem caused by Doppler frequency shift. Phase locked loop(PLL) circuit is widely employed in the receiver to maintain the synchronization of the phase of the transmitted signal and local oscillator. We have proposed a new method based on Newton' s method, which directly gives estimates of frequency and phase of incoming signal.
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