UMTS TDD-CDMA adjacent channel interference cancellation using Kalman Filter

摘要

Inadequate filtering is the main cause of adjacent channel interference (ACI) between adjacent frequency bands. To avoid the lost of UMTS WCDMA systems' capacity, guard-bands have to be used to separate those bands. However, this solution is wasting a lot of frequency resources. In UMTS, ACI occurs in TDD mode more seriously than in FDD mode. The reason is because of the asynchronisation among switching points between up-links and down-link of different networks. In UMTS-TDD mode, ACI occurs between Mobile Station - Mobile Station, Base Station - Base Station, Mobile Station - Base Station, both in up-link and down-link tune-slots. Since UMTS-TDD mode uses only one common frequency band for both up-link and down-link, using guard-bands is really ineffective against ACI. In this paper, firstly, ACI is carefully researched in both UMTS-FDD and UMTS-TDD modes to see the limitations of current solutions. After that, an ACI cancellation algorithm applying Kalman filter is proposed. Simulations are then performed to show the advantages of this proposal over the current solutions.