Filtered Multitone Modulation System Balancing Technology Research

The endless development of communication technology and the design goal of personal communication promote the technology of Internet, multimedia and mobile communication to combine more and more tightly and demand that the next generation of wireless communication will provide high rate, reliable, integrated data communication service. When the data rates are more than several Mbps, the inter-symbol interference (ISI) is generated because the signal duration is shorter than the channel delay spread. In conventional single-carrier modulation, the system complexity will increase greatly due to the multi-taps equalizer used in high data rate wireless communication. The effects of the ISI are negligible so long as the delay spread of the multi-path channel is significantly shorter than the duration of one transmitted symbol. So, multi-carrier transmission technology can be used to overcome this limitation.As one of the multi-carrier transmission technologies, Orthogonal Frequency Division Multiplexing (OFDM) is a key technology in the next generation mobile communication system. It can reduce the effect of multi-path fading with high frequency efficiency. However there are some disadvantages in OFDM system, such as sensitivity to frequency offset caused by oscillator inaccuracy and time variance of wireless channel, the difficulty of symbol synchronization and high peak to average power ratio (PAPR) caused by summation of multiple sub-carriers, etc. All these issues restrict the applications of OFDM in wireless environments to some extent, so many researchers focus on these fields.Comparing to OFDM, Filtered Multi-tone (FMT) Modulation is a new multi-carrier technology. In FMT system., the spectrum of each sub-channel has a high level of spectral containment. So the Inter-channel Interference (ICI) of FMT is negligible compared to other noise, while it often appears in OFDM system because of its sensitivity to frequency offset. However, per sub-channel equalization is needed in order to reduce the remaining ISI introduced by the filter banks.