Contention Protocol for Intelligent Transport Systems

在本研究中，研究了广播系统的丢包补偿协议和调制方案/媒体访问控制方案。(1)对于丢包补偿方案，提出了推式补偿协议和带多码感扩频方案的拉式补偿协议作为无线广播系统可行的重传方案。分析了路车单向通信中与相邻用户相互弥补广播报文缺失的补偿协议。特别地，评估了阻塞概率和获取广播包的平均时间。此外，在存在阴影和加性高斯白噪声的情况下，给出了车辆间通信网络的最优用户数。在阻塞概率上，推式补偿协议优于拉式补偿协议。然而，由于拉式补偿协议可以检测到不成功的用户，因此所有用户都可以完成补偿并抑制无用数据包的传输。此外，拉式补偿协议的数据包传输数低于推式补偿协议。(2)针对媒体访问控制方案，研究了采用移码键控扩频通信（CSK/SS）系统的扩展ALOHA方案。提出了由外序列（正交序列）与内序列（m序列）相乘的双扩展序列和由M_<con>原始正交序列拼接而成的非正交序列作为CSK/SS的扩展序列。该方案优于传统的直接序列扩频（DS/SS） ALOHA方案。非正交序列的CSK/SS ALOHA通量是正交序列的1.1倍。此外，采用信道负载敏感协议（Channel Load Sensing Protocol， CLSP）后，非正交序列的CSK/SS ALOHA的吞吐量性能提高了33.6%。少

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 … More 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