Research On Frequency Allocation Schemes In AFDD Mobile Communication System

With the development of communication system, the high data rate traffic plays more and more important part in future mobile communication system, and the high data rate traffic is characterized by the uplink rate being asymmetric to downlink rate. Furthermore, with increase of transmission rate, the power is also enhanced and the impact on human and environment is growing. By calculation it shows that: under the restriction of electromagnetic radiation, the uplink transmission rate is limited, while the downlink rate is much higher than that of uplink.Duplex technology is used to divide radio resource between uplink and downlink in mobile communication systems, and a proper duplex technology can meet the asymmetric transmission requirement between uplink and downlink, improving utilization efficiency of radio resource. At present, two duplex technologies can meet this requirement, and they are time division duplex -TDD and Asymmetric Frequency Division Duplex - AFDD. TDD is a traditional technology, which could meet the asymmetric transmission requirement but would bring cross time slot interference. AFDD is a novel duplex technology which has no cross time slot interference, and can allocate uplink and downlink resource flexibly according to users' requirement, mitigating inter-cell interference and improving frequency utilization efficiency.The fourth part of this paper proposed two frequency allocation schemes according to AFDD. They are based on inter-cell interference mitigation and user customization respectively. In the first scheme, the aim is to mitigate inter-cell interference. In the second scheme, the aim is to assign frequencies with the custom-built interference level to users according to their requirement. It's proved that the two schemes can achieve the expected results.