| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2005: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2004: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2003: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
In this study, lost packet compensation protocol and modulation schemes / media access control schemes for the broadcasting system were investigated. (1) For lost packet compensation scheme, the push-type compensation protocol and the pull-type compensation protocol with the multi-code sense spread-spectrum scheme were proposed as feasible retransmission scheme for wireless broadcast systems. The compensation protocols for making up lack of the broadcast-packet with neighbor users mutually were analyzed on road-to-vehicle one-way communications. In particular, the probability of blocking and the average time for acquiring the broadcast packet were evaluated. Moreover, the optimum number of users in the inter vehicle communication (IVC) network is shown in the presence of shadowing and additive white gaussian noise. The push type compensation protocol is better than that of the pull type compensation protocol in the blocking probability. However, since the pull type compensation protoco
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l can detect the unsuccessful users, all users can complete compensation and suppress transmissions of useless packets. Moreover, the number of packet transmissions of the pull type compensation protocol is lower than that of the push type compensation protocol. (2) For media access control schemes, spread ALOHA schemes using code shift keying spread-spectrum communication (CSK/SS) system were investigated. (I) the dual-spreading sequence, which is multiplied the outer sequence (orthogonal sequence) by the inner sequence (M-sequence), and (II) the non-orthogonal sequence, which is constructed by concatenating M_<con> primitive orthogonal sequence, were proposed as the spreading sequence of CSK/SS. The CSK/SS ALOHA schemes outperform the conventional direct-sequence spread-spectrum (DS/SS) ALOHA scheme. The throughput of CSK/SS ALOHA with non-orthogonal sequences is 1.1 times greater than that with orthogonal sequences. Moreover, the throughput performance of the CSK/SS ALOHA with non-orthogonal sequences shows a 33.6% increase by applying Channel Load Sensing Protocol (CLSP). Less
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