Efficient utilization of limited frequency resources is one of the most important subjects with the increase of the demands on mobile communication. In recent wireless communications, transmission of multiple information such as voices, images, videos, data, etc. are required. As the result, there are various requirements against data rate, QoS (Quality of Service), etc. Therefore, highly efficient and flexible utilization of frequency bands is demanded. In order to solve these subjects, the use of wireless communication systems that use wide frequency band is very effective, and many researches and developments on wireless communication systems such as wireless MAN (Metropolitan Area Network), LAN (Local Area Network) and PAN (Personal Area Network) using Spread Spectrum Communication, OFDM (Orthogonal Frequency Division Multiplexing), UWB (Ultra Wide Band), etc. being made. Moreover, researches and developments on MIMO (Multiple Input Multiple Output) and relay techniques are also widely made for further improvement of performance. The wideband signal is also effective for ranging and realization of secure communication systems.
展开▼
