期刊名称：International Journal of Engineering and Computer Science
印刷版ISSN：2319-7242
出版年度：2015
卷号：4
期号：10
页码：14817-14830
DOI：10.18535/ijecs/v4i10.34
出版社：IJECS
摘要：The communication through water is different scenario from the communication on the land, while transmission through the waterthe delays are frequently happens when the signals received from geographically separated nodes. Moreover, UWA communicationsenable high motion agility and flexibility of the nodes, and allow interactive system query and instantaneous system response. TheUWA environment is commonly viewed as one of the most challenging environments for wireless communications and networking.It differs from the terrestrial radio environment in many different aspects. Although tremendous progress has been made in the pastliterature but still the synchronism issues is concerned area in the field of UWA communications. To resolve the issue of thesynchronism issues usage of the OFDM communication system is employed and transmissions at the source node by precedingevery OFDM block with an extremely long cyclic prefix (CP) which reduces the transmission rates dramatically. One may increasethe OFDM block length accordingly to compensate for the rate loss which also degrades the performance due to the significantlytime-varying nature of UWA channels. In this paper, we develop a new OFDM-based scheme to combat the asynchronism problemin cooperative UWA systems without adding a long CP (in the order of the long relative delays) at the transmitter. By adding amuch more manageable (short) CP at the source, we obtain a delay diversity structure at the destination for effective processing andexploitation of spatial diversity by utilizing a low complexity Viterbi decoder at the destination, e.g., for a binary phase shift keying(BPSK) modulated system, we need a two-state Viterbi decoder. We provide pair wise error probability (PEP) analysis of the systemfor both time-invariant and block fading channels showing that the system achieves full spatial diversity. Finally the simulationresults shows that performance of the proposed method is good over the conventional state of the art methods and extensivesimulations that the proposed scheme offers a significantly improved error rate performance for time-varying channels (typical inUWA communications) compared to the existing approaches.
