A technique for freeing assignment of time slots for individual cell in TDD system

The paper proposes a TDD-CDMA system, whose TS assignment can be freely switched in an individual cell for increasing further the band efficiency in adapting to the local asymmetric transmission requirements. The inter-cell interference is analyzed for this kind of operation, in which one finds that the interference of BS to BS imposes the most difficulty for implementation. To solve this problem, the concept of frequency reuse is applied to attenuate the interference power in terms of radio frequency (RF) power to a certain amount. In addition, a digital interference canceller is proposed to cancel the remaining interference to a negligible level. Based on the Poisson model of the access, the system capacity is estimated. The results show that the capacities can be increased by a factor of 11% for the DL channel and 27% for the UL channel in comparison with the conventional system, i.e. the UL and DL channel transmissions are synchronized for all cells.