Research on the Effects of Adjacent Channel Interference on OFDM-based Systems
- Research on the Effects of Adjacent Channel Interference on OFDM-based Systems
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- Next generation mobile communication (NGMC) systems have been replaced from voice-oriented service to data-oriented service such as video, internet and multimedia according to the needs of the user. Therefore mobile communication system should provide high quality and fast services, and then it will require more bandwidth. However, because of the limited frequency resources, the importance of efficient management of frequency resources is on the rise.
Current wireless mobile communication systems have been evolved and developed in various forms such as cellular network, WiBro and WLAN. When various systems are mixed, system performance will be degraded due to interference between various systems. To prevent degradation of the performance of the systems, guard bands are set. However, the spectral efficiency will be reduced due to the over-estimated guard band. Therefore, analyzing the interference of the adjacent channel system and setting appropriate guard band are important issues.
In this thesis, the effect of adjacent channel interference is analyzed as follows. First, basic features of OFDM-based system are examined. Second, the methodology of system level performance evaluation and the interference analysis between adjacent channel systems are studied. Third, characteristics of base station, mobile station, channel and new technologies of NGMC system are modeled based on LTE uplink and downlink system. Fourth, we implement a system-level simulator to evaluate the performance of the system based on modeling. The effects of adjacent channel interferences are analyzed using the simulator. Moreover, in order to examine the effects of various environments such as the cell radius, center frequency, channel type and system deployment between two systems, we change the environments and analyze the effects of interference between OFDM-based systems.
As a result, the required ACIR and ACIR offset are obtained for the reference of 5% throughput loss. In the case of downlink, ACIR level should be secured from at least 30 dB to at most 43 dB depending on change of conditions such as cell radius, center frequency, channel environments. In the case of uplink, ACIR offset should be secured from at least -15 dB to at most 5 dB depending on change of environments.
These results provide the basic data needed to set up guard band between adjacent band systems and to calculate the required guard band in various environments when NGMC system is re-deployed.
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