| Summary: | 碩士 === 國立中興大學 === 電機工程學系所 === 99 === In the conventional point-to-point wireless communications, if the transmitted channel is blocked or channel link is invalid, the destination node is not able to receive the message from source node, and therefore the continuous communication is not guaranteed in the process of transmission. In recent years, new wireless network scheme known as "cooperative communication system" help each other to relay messages with the principle of mutual benefit cooperatively, and form a multi-channel virtual circuit in order that the wireless network is used more efficiently, such as: Cellular Networks and Mobile Ad Hoc Networks.
The cooperative communication system is a kind of the point–to–point communications network. Because each relay node causes a variety of random variables in the process of transmission, it becomes more complex that the destination node selects the best transmitted relay node. For the situation, we propose a new relay node selection algorithm to overcome effectively this problem in this paper.
In recent years, academics proposed a variety of solutions. In this paper, with the study of the best relay node algorithm, we select three kinds of relay node selection algorithms including the maximum signal-to-noise ratio (Maximum SNR) algorithm, the maximum diversity gain algorithm and the maximum harmonic mean algorithm for feature comparison analysis, and propose a new scheme - the signal to noise ratio algorithm of the smallest relay, simulate and compare by using Matlab to find the best relay node algorithm.
In other point of view, the algorithm we discussed mainly applies DF (decode-and-forward) protocol with the M-PSK modulation, and the source node transmits a continuous random variance transmission by a multi-path transmitted channel. At the beginning of information forwarded, we calculated the characteristics of the relay channel, the best instantaneous relay node that selected from relay nodes as the main transmission relay. If the best relay node can decode signal correctly and forward the signal to the destination node. The destination node combines the signals of the direct link and the best indirect links using MRC technique.
When signals are transmitted, the communication occurs in two time slots. The source broadcasts the information to N relays and the destination as well. The partial selection diversity is applied to select the best relay node, and the source uses the best relay node with DF to forward singles to the destination. The best instantaneous relay node is selected in a time slot. If DF is effective, the signal will be relayed to the destination node. Otherwise, none of relays transmits. The destination will combine two received signals from the source and the best relay. Therefore, the destination node is directly affected by the characteristics of relays.
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