Jun Kitakado

Downlink beamforming performance for an SDMA terminal with joint detection

We discuss downlink beamforming methods in consideration of a terminal having a joint detector function for space division multiple access (SDMA) in both a multi-input single-output (MISO) channel and a multi-input multi-output (MIMO) channel. We investigate two methods; a general beamformer, which maximizes the desired signals power at the receiver (a transmit MRC diversity) and a null steering concept, which avoids the interference signal reaching the receiver. The computer simulation results show that the null steering concept yields better performance compared to the beam steering, even considering the joint detection at the receiver.

Space domain multistage interference canceller for SDMA

It is difficult for the adaptive array to reduce interference signals efficiently from the received signals when the interference signals and desired signal are closely located. This is a serious problem for a spatial division multiple access (SDMA) system using the multibeam adaptive array as a multiuser detector. We propose a space domain multistage interference canceller (SD-MIC) for the SDMA. Its performance is evaluated in frame error rate (FER) by computer simulations, considering uplink environment in the Japanese personal handy-phone system (PHS). The results show the remarkable improvement in high spatial correlation situations.

The SDMA/TDD base station for PHS mobile communication

Space division multiple access (SDMA) is a multiple access scheme for mobile communications that improves system capacity. We developed the SDMA base station (BS) and carried out several tests. We describe the configuration of the SDMA BS and the results of the tests. The result of the indoor measurement indicates that the SDMA BS has sufficient interference suppression performance. The results of the field test indicate that the traffic capacity is several times greater than existing systems and interference emitted from the SDMA BS is decreased. Therefore, it is confirmed that the SDMA BS achieves substantial improvements in spectrum efficiency without any degradation.

Spatial domain interference canceler using multistage adaptive array with precise timing estimation

In SDMA, a spatial domain interference canceler applying a multistage processing concept to the MMSE multibeam adaptive array has an attractive feature that weak power signals can be detected in the successive stages after removing other strong power signals which are already detected. This idea can be enhanced to the reference timing estimation required in the MMSE algorithm. In this paper the spatial domain interference canceler introducing multistage timing estimation is proposed and its performance is evaluated by computer simulations. The results show that the timing estimation performance is highly improved.