| Summary: | 碩士 === 國立成功大學 === 電信管理研究所 === 94 === It is well known that code division multiple access (CDMA) is an interference-limited system. The sources of the interference mainly came from the co-channel interference and noise. The co-channel interference is caused by the same operator using the same frequency in the nearby area and it could be avoided by cell planning. As for the adjacent channel interference (ACI), it is caused by different operators using adjacent frequencies in the vicinity, and this phenomenon can’t be identified in advance. ACI doesn’t severely damage the system capacity as co-channel interference do. Since the resources of radio spectrums and the lands are limited, telecomm operators should endeavor to suppress the undesired interference to provide the optimal telecomm services. For this reason, the impact of ACI on system performance still can’t be ignored.
An interesting issue emerges from the circumstances that both frequency division duplex (FDD) and time division duplex (TDD) are used as coverage and capacity increasing systems in various environments. When both system modes are deployed in the same geographical area or, for indoor systems, in the same building, care needs to be taken in network planning. This statement is valid regardless of whether one or several operators are running the two modes. Consequently, the interference caused by two different systems due to using the adjacent channel in the same geographical area is worthy to discuss.
This thesis studies the impacts of ACI on uplink capacity in a wide-band code division multiple access (W-CDMA) system using both FDD mode and TDD mode. A simple model is proposed to estimate ACI and capacity loss. This method is based on an interference analysis that considers propagation loss with shadow fading and random distribution of mobile users. Simulation results indicate that ACI may cause up to 30% capacity reduction. However, with suitable arrangement for the location of base stations, the impacts of ACI on capacity can be reduced. The proposed method is useful for mobile operators to plan their radio networks when both FDD mode and TDD mode need to be deployed at adjacent channel frequencies.
|
|---|
