Multilevel Shaping Research Articles

Dirty Paper Coding Based on Polar Codes and Probabilistic Shaping

A precoding technique based on polar codes and probabilistic shaping is introduced for dirty paper coding. Two variants of the precoding use multi-level shaping and sign-bit shaping in one dimension. The decoder uses multi-stage successive-cancellation list decoding with list-passing across the bit levels. The approach achieves approximately the same frame error rates as polar codes with multi-level shaping over standard additive white Gaussian noise channels at a block length of 256 symbols and with different amplitude shift keying (ASK) constellations.

Common-Ground Photovoltaic Inverters for Leakage Current Mitigation: Comparative Review

In photovoltaic systems, parasitic capacitance is often formed between PV panels and the ground. Because of the switching nature of PV converters, a high-frequency voltage is usually generated over these parasitic capacitances; this, in turn, can result in a common-mode current known as leakage current. This current can badly reach a high value if a resonance circuit is excited through the PV’s parasitic capacitance and the converter’s inductive components. Transformers are usually used for leakage current mitigation. However, this decreases the efficiency and increases the cost, size, and weight of the PV systems. Number of strategies have been introduced to mitigate the leakage current in transformer-less converters. Among these strategies, using common-ground converters is considered the most effective solution as it offers a solid connection between the negative terminal of PV modules and the neutral of the grid side; thus, complete mitigation of the leakage current is achieved. Number of common-ground inverters have been recently presented. These inverters are different in their size, cost, boosting capability, the possibility of producing DC currents, and their capability to offer multilevel shaping of output voltage. This work introduces a comprehensive review and classification for various common-ground PV inverters. Therefore, a clear picture of the advantages and disadvantages of these inverters is clarified. This provides a useful indication for a trade-off between gaining some of the advantages and losing others in PV systems. In addition, the potentials for optimization based on different performance indicators are identified.

A Novel Dual-Input High-Gain Transformerless Multilevel Single-Phase Microinverter for PV Systems

This article proposes a novel single-phase microinverter that is fit to process the power of two photovoltaic (PV) modules in a modular way. The proposed topology combines a full-bridge inverter integrated with two dc–dc boost converters, in addition to a dc link that consists of switched capacitor (SC) networks. The operating modes of the proposed topology are illustrated. The voltage stress of all components is identified. A modulation technique along with a control system is developed for a proper operation of the proposed topology. A comparative study with other topologies is introduced, and the following merits for the proposed one are presented: 1) The power of two PV modules can be harvested individually or simultaneously without any circulating current issues; 2) very high gain can be acquired, and, thus, no series connection of PV modules is required for grid-tied applications; 3) transformerless operation; 4) multilevel shaping of the output voltage, and, thus, reduced filter size is required; and 5) self-balancing for the dc-link capacitors, and, thus, simple control systems can be used. The performance of the seven-level version of the proposed topology is validated using real-time simulation and experimental prototype under grid-tied and stand-alone conditions, respectively.

Correction to: Top-down, Bottom-up and Sideways: the Multilayered Complexities of Multi-level Actors Shaping Forest Governance and REDD+ Arrangements in Madre de Dios, Peru.

The article Top-down, bottom-up and sideways: the multilayered complexities of multi-level actors shaping forest governance and REDD+ arrangements in Madre de Dios, Peru, written by Dawn Rodriguez-Ward, Anne M. Larson, Harold Gordillo Ruesta, was originally published electronically on the publisher's internet portal (currently SpringerLink) on 3 January 2018 without open access. With the author(s)' decision to opt for Open Choice the copyright of the article changed on (25 April 2018) to

Multilevel signaling and pulse shaping for spectrum efficiency in subcarrier multiplexing transmission

Subcarrier multiplexing (SCM) transmission has been widely used for analog video transmission in CATV systems. As digital video technology rapidly advances, there is a strong need to transmit digital video over the same SCM system. Since digital video such as HDTV requires a much larger bandwidth, multilevel signaling becomes an important approach. As the number of levels increases, however, the noise margin decreases and the system is more subject to adjacent channel interference (ACI). In this paper, we analyze the spectrum efficiency and power penalty of multilevel SCM transmission. We found that using pulse shaping can make multilevel signaling attractive. Depending on the ACI that can be tolerated, results show that multilevel amplitude-shift keying (ASK) of 5-7 b/symbol can give the optimum spectrum efficiency using the raised-cosine pulse. The price paid is a slight power penalty of 0.4 dB to reduce intersymbol interference (ISI) to zero. >