Frequency-segregated dynamic channel allocation for asynchronized TDMA/TDD frame among base stations

We propose a novel dynamic channel allocation (DCA) algorithm with a distributed control scheme for mobile radio systems in which the TDMA/TDD frames of inter-base station links are not synchronized. TDMA/TDD is one of the best radio access technologies for mobile radio systems such as PHS and DECT because the same frequency is used by the forward and reverse links and many hardware parts can be commonly used in the transmitter and the receiver. A distributed control scheme significantly facilitates dynamic channel allocation, however, it makes it difficult to synchronize TDMA frames among the base stations. This asynchronization degrades the frequency utilization because one slot may interfere with two slots of a near-by base station. Furthermore, the EIRP difference between the forward and reverse links of TDMA/TDD severely degrades the frequency utilization factor if the TDMA frame phase is not synchronized. This paper proposes a frequency-segregated dynamic channel allocation scheme that makes it possible to use some of the inactive forward link channel resources for asynchronized TDMA/TDD. Those resources cannot be utilized because of excessive interference that cannot be avoided by a conventional DCA algorithm. The proposed DCA algorithm is evaluated by computer simulations. The results indicate that the proposed DCA algorithm improves blocking probability characteristics by 10-20%. This algorithm compensates the defects of TDMA/TDD due to the asynchronized frame and unbalanced EIRP.