Research On Signal Transmission Schemes In Physical Layer Of Cooperative MIMO Moible Ad Hoc Networks

Because mobile Ad hoc networks are able to be set up quickly without support of the existing fixed infrastructures and the nodes in a mobile Ad hoc network could join in or leave from the network dynamically, randomly and frequently, which will not affect the communication of other nodes of the network, it is concerned by more and more researchers and will become one of important network forms of future wireless communication. However, mobile Ad hoc networks still have several issues that are route selection, how to ensure the safety and reliability of communication, how to ensure quality of service, how to save energy consumption, in what way the system interconnect with the existing networks and so on to be resolved. For this reason, on the basis of some classical wireless communication techniques, this paper focused on the signal transmission mechanisms of mobile Ad hoc networks. Finally, three new signal transmission mechanisms suitable for three types of mobile Ad hoc networks were proposed. The main work is as follows:(1) Independent-receiver Phase-Inversion Symmetric Cooperative Multi-Input Multi-Output (I-PIS-CMIMO) mechanism. This mechanism absorbed the advantages of cooperative MIMO technology and symmetric phase inversion technique for the purpose of being suitable for the mobile Ad hoc network environment in which only a pair of sending and receiving nodes conduct half-duplex communication at the same time and two involved cooperative receiving nodes independently receive the signals sent by the corresponding cooperative transmitting nodes. Theoretical analysis and MATLAB simulation results demonstrated that I-PIS-CMIMO transmission mechanism made mobile Ad hoc networks get the three to nine times output SNR gain than traditional collaborative MIMO wireless networks, improved unit bandwidth channel capacity of the mobile Ad hoc network, and reduced the signal transmission error rate of the mobile Ad hoc network, so I-PIS-CMIMO transmission mechanism reached the purpose of optimizing cooperative MIMO mobile Ad hoc network performance.(2) Mixed-receiver Phase-Inversion Symmetric Cooperative Multi-Input Multi-Output (M-PIS-CMIMO) mechanism. This mechanism was also based on cooperative MIMO technology and symmetric phase inversion technique and suitable for the mobile Ad hoc network environment in which only a pair of sending and receiving nodes conduct half-duplex communication at the same time, but two involved cooperative receiving nodes could receive the all signals sent by the corresponding cooperative transmitting nodes. Theoretical analysis and MATLAB simulation results demonstrated that M-PIS-CMIMO transmission mechanism made mobile Ad hoc networks at least get the four times output SNR gain than traditional collaborative MIMO wireless networks, also improved unit bandwidth channel capacity of the mobile Ad hoc network, and reduced the signal transmission error rate of the mobile Ad hoc network. Although the overall performance optimization capability of M-PIS-CMIMO transmission mechanism was slightly lower than that of I-PIS-CMIMO transmission mechanism, its application environment was closer to a realistic wireless communication environment so that it would have more practical value.(3) Multi-user Detection receiver Phase-Inversion Symmetric Cooperative Multi-Input Multi-Output (MUD-PIS-CMIMO) mechanism. At the transmitting end, each node was assigned a unique spreading code sequence. At the receiving end, inter-symbol interference was eliminated and the original thansmitted signal was recovered by using adaptive variable step-size LMS blind multi-user detection technology. This mechanism was suitable for the mobile Ad hoc network environment in which pairs of sending and receiving nodes conduct half-duplex communication at the same time. MUD-PIS-CMIMO mechanism took into account not only the Gaussian white noise existing in the channel, also the mutual interference between multiple users, so it was closest to the actual wireless communication environment. Theoretical analysis and MATLAB simulation results demonstrated that MUD-PIS-CMIMO transmission mechanism made mobile CDMA-Ad hoc networks obtain the same output SNR gain as the networks using M-PIS-CMIMO transmission mechanism. Although its signal transmission error rate was slightly higher than I-PIS-CMIMO and M-PIS-CMIMO mechanisms, its superiority of increasing exponentially the channel capacity per bandwidth greatly improved the practical application performance of cooperative MIMO mobile Ad hoc networks.