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Autori:  Girotto, Mauro 
Supervisore afferente all'Università:  TONELLO, ANDREA 
Centro di ricerca:  DIPARTIMENTO INGEGNERIA ELETTRICA GESTIONALE MECCANICA  DIEG 
Titolo:  Cyclic Block Filtered Multitone Modulation: Design and Performance Analysis 
Abstract (in inglese):  Nowadays, high data rate communication demand is growing. Thus, several communication technologies, both wireless and wireline, have adopted Filter Bank Modulation (FBM) at the physical layer. In a general FBM scheme, the high data rate stream is converted into a series of several parallel low data rate streams. These streams are modulated with a series of carrier signals. In frequency domain, the available bandwidth is partitioned in disjointed subchannels. If the subchannel number is sufficiently high, the subchannel frequency response is quasiflat and the equalizer can be simplified. Furthermore, FBM schemes have low complexity digital implementation and bit loading could be used to minimize the transmission power.
In this thesis, a FBM transceiver is presented. The idea is to obtain good subchannel frequency confinement as it is done by the family of exponentially modulated filter banks that is typically referred to as Filtered Multitone (FMT) modulation. However, differently from conventional FMT, the linear convolutions are replaced with circular convolutions. Since transmission occurs in blocks, the scheme is referred to as Cylic Block Filtered Multitone Modulation (CBFMT). This thesis focuses on the principles, design, implementation and performances analysis of CBFMT. In particular, it is shown that an efficient realization of both the transmitter and the receiver is possible in the frequency domain (FD), and it is based on the concatenation of an inner Discrete Fourier Transform (DFT) and a bank of outer DFTs. Such an implementation suggests a simple subchannel FD equalizer. The overall required implementation complexity is lower than in FMT. Furthermore, the orthogonal filter bank design is simplified. The subchannel frequency confinement in CBFMT yields compact power spectrum and lower peaktoaverage power ratio than in Orthogonal Frequency Division Multiplexing (OFDM).
Then, the orthogonal prototype pulse design problem is considered. The orthogonality conditions are derived in time domain and frequency domain. These conditions are translated in matrix form and pulse coefficients are parameterized with hyperspherical coordinates, a nonlinear combination of trigonometric functions. The mathematical analysis shows that exists an infinite number of solutions. Next, the orthogonality is discussed in presence of a transmission medium. In general, the channel could destroy the orthogonality. Finally, optimal orthogonal pulses are designed to maximize the inbandtoout band energy ratio and the achievable rate in timevariant channel scenario. These optimal pulses improve the performance of the baseline rootraisedcosine pulse.
Furthermore, the equalization task is discussed. Equalizers are necessary to restore the orthogonality when an equivalent filter is inserted between the transmitter and the receiver. This filter could represent the transmission medium, a real interpolation filter or the hardware nonideality. We discuss several equalizers, both for timeinvariant and timevariant channels. A cyclic prefix (CP) can be added to the transmitted signal. We show that when the CP length is greater than the channel impulse response length, perfect reconstruction (PR) is possible. For timeinvariant channels, a simple 1tap equalizer is sufficient to restore the orthogonality. We show that in the timevariant scenario, the 1tap equalizer is not sufficient to restore the orthogonality. Several equalizers are proposed for the timevariant case.
Finally, performances in real application scenarios are evaluated. We start from Power Line Communications. For inhome high data rate communications, broadband PLC (BBPLC) is used. BBPLC generally operates in the band 230 MHz. Transmission above 30 MHz is possible, but the electromagnetic compatibility (EMC) limits are more stringent than the limits in the band below 30 MHz. In the 230 MHz range there are several subbands dedicated to other communication systems, e.g. to amateur radio. A spectrum notching mask has to be fulfilled by the power spectral density (PSD) of the transmitted signal to grant coexistence. For command and control applications, narrowband PLC (NBPLC) is used. NBPLC operates in portions of the 3500 kHz spectrum and it has to obey certain spectral masks for EMC and coexistence issues, similarly to BBPLC. Although OFDM allows simple spectrum management by switching onoff the subchannels, its poor subchannel frequency selectivity translates into a poor spectrum usage. An agile use of the spectrum and higher spectral efficiency can be obtained with filter bank modulation. In particular, we investigate the use of CBFMT modulation and compare it to pulseshaped OFDM (PSOFDM) deployed in the G3PLC and IEEE P1901.2 standards for NBPLC. For BBPLC, we compare CBFMT with the HomePlug standard. The comparison shows that higher spectral efficiency and improved spectrum management can be achieved with CBFMT.
For the wireless scenario, the land mobile radio systems are considered. The transmitted signal propagates through a multipath channel. This propagation model is caused by several natural and manmade obstacles that introduce reflections, diffraction and scattering. Timeinvariant and timevariant scenarios are considered. The FD equalization allows the exploitation of the transmission medium time and frequency diversity; thus, it potentially yields lower symbol error rate and higher achievable rate in timevariant frequencyselective fading. 
Parole chiave:  Filter bank modulation; Multicarrier modulation; OFDM; FMT; Orthogonality; Equalization; Wireless; Power line communication 
MIUR :  Settore INGINF/03  Telecomunicazioni 
Lingua:  eng 
Data:  8apr2015 
Corso di dottorato:  Dottorato di ricerca in Ingegneria industriale e dell'informazione 
Ciclo di dottorato:  27 
Università di conseguimento titolo:  Università degli Studi di Udine 
Luogo di discussione:  Udine 
Citazione:  Girotto, M. Cyclic Block Filtered Multitone Modulation: Design and Performance Analysis. (Doctoral Thesis, Università degli Studi di Udine, 2015). 
In  01  Tesi di dottorato

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