Research On Key Technologies Of Amorphous Cell Mobile Relay Communication Systems

Mobile relay nodes (MRNs), i.e., relays mounted on top of cars, trains or other public transportation vehicles, can provide reliable access points besides the fixed nodes for passengers in the vehicle and the crowd around the vehicle. The cell coverage is enhanced and the user experience is improved by deploying the MRNs. Not only the collaboration between the MRNs and the fixed nodes in the amorphous cell (AC) based on the MRNs can reduce the number of dead zones in the traditional cell and improve the cell capacity, but also the collaboration can reduce the number of the fixed nodes deployed and improve the energy efficiency of the system. The key technologies of the amorphous cell moile relay communication system are studied in this paper.Firstly, basic concepts and typical scenarios of the mobile relay communication system with the amor-phous cell are described in this article. Wireless mobile communication channels are analyzed and a new Rice fading channel simulation model suitable for the high speed railway environment is introduced. Based on the introduction of the overall system architecture and the relay node protocol stacks, the relay technologies are classified in detail and the key technologies of the mobile relay communication system with the amor-phous cell are summarized. The basic principles of the orthogonal frequency division multiplexing (OFDM) is further analyzed, and the advantages and disadvantages of the OFDM technology is discussed.Then, the channel estimation technology in the backhaul link under high speed mobile communication scenariois is studied. The baseband model of the OFDM system is discussed, and the classic channel esti-mation methods are summarized in terms of the pilot pattern design, channel estimation algorithms for pilot sub-carriers and the interpolation methods for channel state information in data sub-carriers. The new Rice fading channel simulation model is used for the simulation and comparison of a variety of classic channel estimation methods. In addition, the basis expansion model for fast time-varying channel is studied, and the complexity of the method for backhaul link channel estimation is analyzed. The pilot insertion pattern adopted to estimate basis coefficients is improved, and the channel estimation accuracy is effectively increased by utilizing the distributed pilot insertion pattern compared with that utilizing the traditional centralized pilot insertion pattern, which is vadilated by the simulation results.Finally, the resource allocation technology of the mobile relay communication system are studied. The direct transmission mode and the MRN aided transmission mode are introduced on the basis of the estab-lishment of a MRN aided multiuser transmission system model. Concepts and details of the implementation process of the transmission mode selection are elaborated, and the average system capacity is improved by carrying out the transmission mode selsection according to the simulation results. A hybrid power allocation algorithm based on the transmission mode selection is further proposed. Different power allocation schemes are assigned to users utilizing different transmission modes according to the proposed algorithm. The average system capacity is improved significantly by adopting the proposed hybrid power allocation algorithm that is proved by the simulation results.