| Project/Area Number |
05805034
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
情報通信工学
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| Research Institution | Waseda University |
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Principal Investigator |
TAKAHATA Fumio Waseda University School of Science and Engineering, Professor, 理工学部, 教授 (20206866)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1994: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1993: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Spread Spectrum / Packet Communications / ALOHA System / Direct Sequence / Chirp / Carrier Recovery / Symbol Timing Recovery / Throughtput / 一括復調方式 / 熱雑音 / フェージング |
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| Research Abstract |
A spread ALOHA system using a unified spread spectrum code is discussed in terms of its performance, design and transmission efficiency. The system is outlined and then the bit error performance under two conditions is derived by a theoretical analysis and an approximate method. The comparison it with the results obtained by means of computer simulation indicates that the theoretical results coincide perfectly with the simulated ones and that the approximayte results coincide with the simulated results in the low E_b/N_0 range. A demondulator is designed focussing on symbol timing recovery and carrier recovery. It is proposed that the provision of a short preamble enables to apply a synchronous cyclic addition to these recoveries. It is concluded as a result of performance evaluation concerming symbol timing detection and carrier offset estimation that the proposed scheme improves the performance remarkably. The transmission efficiency obtained in the spread ALOHA system is derived for
… More
three cases. Comparing quantitatively the transmission efficiency in the first case with that of the conventional slotted ALOHA system under the condition at the same frequency bandwidth, it is concluded that the spread ALOHA system gives a good performance with the lower transmitting power compared with that of the slotted ALOHA system. As for the other two cases, the system using a unified spread spectrum code is compared with that using different spread spectrum codes in terms of transmission efficiency and it becomes obvious that the former system provides better performance for the long packet length than the latter one. Finally it is proposed to realize a spread-ALOHA system by using a chirp signal. Correlation process using the chirp matched filter is theoretically described at first and signal processings to be performed in the receiving side are clarified, in particular focussing on the block demodulator. The quantitative evaluation under various conditions is discussed concerning bit error rate performance obtained by means of computer simulation. Less
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