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Implementation of the channel equalization algorithms used in FMT modulation
Krejča, Libor ; Krajsa, Ondřej (referee) ; Šilhavý, Pavel (advisor)
The objective of Diploma thesis is design of analysis tool for equalizers used in FMT modulation. The model of transmission channel was designed for simulations with FMT. The transmission path is modeled by test loop, which corresponds to DSL line. For this reason, some principles of DSL technology is described in the thesis. The principles of multicarrier modulation are introduced in first part. The multicarrier modulation with filter bank (FMT) is described in detail.The different methods of design the fiter bank are given and compared. Channel equalization are introduced in second part. The attention was focused on minimum mean square error filtering (MMSE). Decision feedback channel equalizer (DFE) is extended from linear MMSE equalizer. DFE equalizers were programmed in analysis tool. For computation of equalizer coeficients was used also equalizers based on adaptive algorithms and MMSE. The last part describes the results of DFE equalizers used in communication system with FMT modulation. Analysis tool was programmed in MATLAB with a graphical user interface. It allows to show mean square error, signal-to-noise ratio and transmission speed dependence on delay between original and distorted signal. Signal-to-noise ration is displayed also in individual subchannels and users can display mean square error dependence on different orders of DFE filters.
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Multitone Modulation Implemented via Filter Bank
Krajsa, Ondřej ; Vlček, Čestmír (referee) ; Róka, Rastislav (referee) ; Šilhavý, Pavel (advisor)
The work is focused on multitone modulation implemented by filter banks, which are alternative modulations to DMT and OFDM modulations. The paper describes the two proposed modulation schemes, non-overlapped FMT and half-overlapped FMT. This modulations utilize the benefits of implementing FFT algorithm in conjunction with a bank of polyphase filters that are derived from the prototype filter. To design the prototype filter a Matlab tool is developed. For both modulations the simulation models were created for xDSL systems and for wireless transmission channel. Non-overlapped FMT modulation proved to be a suitable modulation scheme for channels with narrowband interference and sharp edges in the transmission function of the channel. It was allowed by perfect separation of each subchannel and with preserving the orthogonality between subchannels using the FFT algorithm and utilization of appropriate filters. Half-overlapped FMT modulation allows as well as the DMT modulation optimal utilization of provided transmittion band, because the power spectral density of the signal is flat. But it is not suitable for transmission channels with roughly shaped by changes in the transmission function and narrowband interference. Optimization implementations were designed using parallel processing on the DSP Texas Instruments TMS320C67x series. It thus achieved almost ten-fold reduction in computational complexity. In FMT modulation both options ensure increased signal to noise ratio and thus allow the use of constellation diagrams with a large number of signal elements with the same transmit power and also higher transmission speed.
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Multitone Modulation Implemented via Filter Bank
Krajsa, Ondřej ; Vlček, Čestmír (referee) ; Róka, Rastislav (referee) ; Šilhavý, Pavel (advisor)
The work is focused on multitone modulation implemented by filter banks, which are alternative modulations to DMT and OFDM modulations. The paper describes the two proposed modulation schemes, non-overlapped FMT and half-overlapped FMT. This modulations utilize the benefits of implementing FFT algorithm in conjunction with a bank of polyphase filters that are derived from the prototype filter. To design the prototype filter a Matlab tool is developed. For both modulations the simulation models were created for xDSL systems and for wireless transmission channel. Non-overlapped FMT modulation proved to be a suitable modulation scheme for channels with narrowband interference and sharp edges in the transmission function of the channel. It was allowed by perfect separation of each subchannel and with preserving the orthogonality between subchannels using the FFT algorithm and utilization of appropriate filters. Half-overlapped FMT modulation allows as well as the DMT modulation optimal utilization of provided transmittion band, because the power spectral density of the signal is flat. But it is not suitable for transmission channels with roughly shaped by changes in the transmission function and narrowband interference. Optimization implementations were designed using parallel processing on the DSP Texas Instruments TMS320C67x series. It thus achieved almost ten-fold reduction in computational complexity. In FMT modulation both options ensure increased signal to noise ratio and thus allow the use of constellation diagrams with a large number of signal elements with the same transmit power and also higher transmission speed.
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Implementation of the channel equalization algorithms used in FMT modulation
Krejča, Libor ; Krajsa, Ondřej (referee) ; Šilhavý, Pavel (advisor)
The objective of Diploma thesis is design of analysis tool for equalizers used in FMT modulation. The model of transmission channel was designed for simulations with FMT. The transmission path is modeled by test loop, which corresponds to DSL line. For this reason, some principles of DSL technology is described in the thesis. The principles of multicarrier modulation are introduced in first part. The multicarrier modulation with filter bank (FMT) is described in detail.The different methods of design the fiter bank are given and compared. Channel equalization are introduced in second part. The attention was focused on minimum mean square error filtering (MMSE). Decision feedback channel equalizer (DFE) is extended from linear MMSE equalizer. DFE equalizers were programmed in analysis tool. For computation of equalizer coeficients was used also equalizers based on adaptive algorithms and MMSE. The last part describes the results of DFE equalizers used in communication system with FMT modulation. Analysis tool was programmed in MATLAB with a graphical user interface. It allows to show mean square error, signal-to-noise ratio and transmission speed dependence on delay between original and distorted signal. Signal-to-noise ration is displayed also in individual subchannels and users can display mean square error dependence on different orders of DFE filters.
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