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低轨卫星物联网随机码分多址技术 被引量:2
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作者 邱琳 陈舒怡 孟维晓 《无线电通信技术》 2021年第5期549-556,共8页
作为国家导向的数字新基建,卫星物联网可有效地对地面蜂窝网络进行补充,具有覆盖范围广、受环境条件影响小、较高的可靠性与稳定性等特点。传统的接入方式按照不同的网络层次可分为物理层的多址接入技术及MAC层的随机接入技术。然而分... 作为国家导向的数字新基建,卫星物联网可有效地对地面蜂窝网络进行补充,具有覆盖范围广、受环境条件影响小、较高的可靠性与稳定性等特点。传统的接入方式按照不同的网络层次可分为物理层的多址接入技术及MAC层的随机接入技术。然而分析现有的接入技术,针对卫星物联网这一特定场景的研究鲜有提及。在现有的ALOHA随机接入技术基础上,结合码分多址CDMA的思想,给出了基于码道划分的非授权随机接入方式,并针对该方式下的碰撞包丢弃与碰撞包重传两种方式下的系统性能进行仿真,分析了吞吐量、成功传输概率、平均重传时延及碰撞概率等几个主要参数指标。仿真结果显示,多码道随机接入情况下,系统的碰撞概率及吞吐量性能明显提升,更适用于大规模接入的卫星物联网。进一步对卫星物联网采用授权与免授权混合模式下的系统性能进行了理论及仿真分析,给出了系统吞吐量最大及碰撞概率最低时的码道数目理论值。 展开更多
关键词 卫星物联网 随机接入 码道正交 碰撞概率
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A NEW ML DETECTION ALGORITHM FOR ORTHOGONAL MULTICODE SYSTEM IN NAKAGAMI FADING CHANNEL
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作者 Wei Shengqun Cheng Yunpeng Wang Jinlong 《Journal of Electronics(China)》 2006年第2期184-188,共5页
Based on the Maximum-Likelihood (ML) criterion, this paper proposes a novel noncoherent detection algorithm for Orthogonal Multicode (OM) system in Nakagami fading channel. Some theoretical analysis and simulation res... Based on the Maximum-Likelihood (ML) criterion, this paper proposes a novel noncoherent detection algorithm for Orthogonal Multicode (OM) system in Nakagami fading channel. Some theoretical analysis and simulation results are presented. It is shown that the proposed ML algorithm is at least 0.7 dB better than the conventional Matched-Filter (MF) algorithm for uncoded systems, in both non-fading and fading channels. For the consideration of practical application, it is further simplified in complexity. Compared with the original ML algorithm, the simplified ML algorithm can provide significant reduction in complexity with small degradation in performance. 展开更多
关键词 Signal detection Orthogonal code Maximum-Likelihood (ML) Nakagami fading channel
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A CODE DESIGN CRITERIA FOR NOT FULLY CONNECTED CHANNEL
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作者 Xiao Haiyong Bi Guangguo Zhang Peng Jin Xiufeng 《Journal of Electronics(China)》 2006年第2期193-196,共4页
There are parallel channels which are not fully connected in practice, such as Frequency Division Multiplex (FDM or Orthogonal FDM) systems. Conventional space-time codes can be used for such parallel channels but not... There are parallel channels which are not fully connected in practice, such as Frequency Division Multiplex (FDM or Orthogonal FDM) systems. Conventional space-time codes can be used for such parallel channels but not the optimal. Based on the derivation of PEP expression for codes transmitted on parallel block fading channels, criteria of codes design for not fully connected channels are proposed and are compared with Tarokh's criteria for fully connected channel. New codes for such channels are provided by systematical and exhaustive search. Simulation results show that these codes offer better performance on parallel FDM channels than other known codes. 展开更多
关键词 Block fading channel Parallel channel Space-time codes Orthogonal Frequency Division Multiplex (OFDM) DIVERSITY
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