A Study on Spatial Wireless Channel Control Techniques in Broadband Ubiquitous Wireless Networks

In this research, we have developed received interference suppression, radiated interference suppression and electromagnetic field distribution control techniques to autonomously organize broadband ubiquitous networks in which many wireless nodes are densely located in a limited space, and obtained the following results. [Received interference suppression technique] We have developed a soft canceller with minimum mean square error (SC/MMSE) based turbo equalizer for suppression of received interference. Moreover, we have developed a dynamic spectrum control technique in which transmitted spectrum is dynamically mapped onto spectrum with higher channel quality to escape from severe interference. These results confirm that the proposed technique is effective in enhancement of robustness to interference. [Radiated interference suppression technique] We have developed a flexible routing technique for wireless mesh networks that can keep field strength of the electromagnetic wave radiated to outside a smart space below an acceptable level, and confirmed that the technique is effective in flexible construction of electromagnetic field distribution in an area. [Adaptive access control] We have developed multiuser multi-input multi-output (MIMO) techniques to enhance efficiency of radio resource usage. In this research, we have developed a precoding technique in the transmitter node to spatially separate transmitted signals destined to different terminals and confirmed by computer simulation and experimental evaluations that the proposed technique is effective in enhancement of system throughput in multiuser environments. We have also developed a dynamic spectrum control combined with a MIMO technique to further enhance flexibility of radio resource management, and confirmed that the proposed scheme is effective in control of radio resource assignment more flexible than only the dynamic spectrum employed or only multiuser MIMO employed cases.