Mauro Girotto

Cyclic block FMT modulation for broadband power line communications

A novel multi-carrier modulation scheme for broadband power line communication (PLC) is presented. The novel architecture is based on the Filtered Multitone (FMT) modulation concept. However, the novel modulation scheme uses the circular convolution instead of the linear convolution in the filtering operations. We refer to this new architecture as Cyclic Block Filtered Multitone Modulation (CB-FMT). CB-FMT can benefit from the high sub-channel frequency confinement and the design of an orthogonal prototype pulse is simplified w.r.t. conventional FMT. A simple frequency domain equalizer can be deployed in frequency selective channels. Furthermore, CB-FMT can offer high frequency notching capability which is an important requirement in PLC to fulfill EMC norms. Numerical results show that CB-FMT has higher achievable rate than OFDM for the same number of data sub-channels.

Cyclic block filtered multitone modulation

A filter bank modulation transceiver is presented. The idea is to obtain good sub-channel 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 cyclic block FMT (CB-FMT). This paper focuses on the principles, design, and implementation of CB-FMT. 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 sub-channel FD equalizer. The overall required implementation complexity is lower than in FMT. Furthermore, the orthogonal filter bank design is simplified. The sub-channel frequency confinement in CB-FMT yields compact power spectrum and lower peak-to-average power ratio than in OFDM. Furthermore, 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 time-variant frequency-selective fading.

Multitechnology (I-UWB and OFDM) Coexistent Communications on the Power Delivery Network

To improve the performance and to support novel command and control applications in the smart-grid context, novel or alternative transmission schemes can be used in combination with existent power-line communication (PLC) solutions that are based on multicarrier or narrowband single carrier modulation schemes. In this respect, it is fundamental to ensure the coexistence between different systems yet respecting electromagnetic-compatibility (EMC) constraints. We consider the deployment of impulsive-ultrawideband (I-UWB) modulation for low-data-rate PLC. First, we study the design of the modulation parameters as a function of the application scenario. We consider the in-home, the outdoor low-voltage, and the outdoor medium-voltage scenario. Furthermore, we discuss EMC aspects and, according to the norms, we derive the limits for the power spectral density of the I-UWB signal. Then, we study the coexistence between existing orthogonal frequency-division multiplexing (OFDM) PLC solutions and I-UWB when they (partly) share the spectrum. We focus on the physical layer and we perform the analysis in terms of maximum achievable rate. The results show that I-UWB is suitable for low-data-rate applications and, further, it can coexist with existing OFDM PLC systems.

Improved spectrum agility in narrow-band PLC with cyclic block FMT modulation

Narrow-Band power line communications (NB-PLC) operate in portions of the 3-500 kHz spectrum and have to obey certain spectral masks for EMC and coexistence issues. Although orthogonal frequency division multiplexing (OFDM) allows simple spectrum management by switching on-off the subchannels, its poor sub-channel 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, in this paper, we investigate the use of cyclic block filtered multitone (CB-FMT) modulation and compare it to pulse shaped OFDM (PS-OFDM) deployed in the G3-PLC and IEEE P1901.2 standards. The comparison shows that higher spectral efficiency and improved spectrum management can be achieved with CB-FMT.

EMC Regulations and Spectral Constraints for Multicarrier Modulation in PLC

This paper considers electromagnetic compatibility (EMC) aspects in the context of power line communication (PLC) systems. It offers a complete overview of both narrow band PLC and broad band PLC EMC norms. How to interpret and translate such norms and measurement procedures into typical constraints used by designers of communication systems is discussed. In particular, the constraints to the modulated signal spectrum are considered and the ability of pulse shaped OFDM (PS-OFDM), used in most of the PLC standards as IEEE P1901 and P1901.2, to fulfill them is analyzed. In addition, aiming to improve the spectrum management ability, a novel scheme named pulse shaped cyclic block filtered multitone modulation (PS-CB-FMT) is introduced and compared to PS-OFDM. It is shown that PS-CB-FMT offers better ability to fulfill the norms which translates in higher system capacity.

Performance of practical receiver schemes for impulsive UWB modulation on a real MV power line network

We consider the deployment of impulsive ultra wide band (I-UWB) modulation for power line communications (PLC) on medium voltage (MV) networks. We firstly describe several receiver structures, and practical channel detection algorithms based on a data-aided approach. The joint estimation of the channel response and the noise correlation is also considered. Then, we address the system performance on real MV channels. The channels have been measured in a real MV test network. Results are provided in terms of bit error rate, with a power spectral density constraint.

Orthogonal Design of Cyclic Block Filtered Multitone Modulation

The orthogonal design of a cyclic block filtered multititone modulation (CB-FMT) system is addressed. CB-FMT is a filter bank modulation scheme that uses frequency confined prototype pulses, similarly to FMT. Differently from FMT, where the linear convolution is used, the cyclic convolution is exploited in CB-FMT. This allows to efficiently implement the system via a concatenation of discrete Fourier transforms. The necessary and sufficient orthogonality conditions are derived in time domain and frequency domain. Then, these conditions are expressed in matrix form, and the prototype pulse coefficients are parameterized with hyper-spherical coordinates. The effect of a linear time-variant transmission medium is discussed. In such a scenario, the optimal filter bank orthogonal design is considered with the objective of maximizing either the in-band-to-out-band sub-channel energy ratio or the achievable rate. Numerical results and comparisons show the performance improvements attainable with several designed optimal pulses also with respect to the use of the baseline root-raised-cosine pulse.

Adaptive zero padded CB-FMT for LTE uplink transmission in the high mobility scenario

LTE is the most recent standard for the mobile cellular communication. To achieve high speed communications, multi-carrier modulations have been adopted both for the downlink and the uplink. In the LTE downlink, OFDMA (the multi-user version of OFDM) has been chosen. The LTE uplink uses instead SC-FDMA modulation, an OFDM alternative. In this work, the use of CB-FMT, jointly with SC-FDMA, is analyzed in the high mobility scenario. Numerical results show that CB-FMT outperforms SC-FDMA in several cases. Thus, an adaptive implementation architecture that allows to flexibly choose the modulation scheme is proposed to maximize the achievable rate. Furthermore, for compliance with existing LTE parameters, frequency domain zero padded CB-FMT is proposed, and the problem of designing optimal capacity wise waveforms is considered.