Partial Decode-and-forward Research Articles

Enhanced robust diagnosis of multiple‐type demagnetisation fault for permanent magnet synchronous motor based on D‐axis magnetic network model using magnetic field reconstruction

AbstractDemagnetisation fault (DF) is a common rotor fault in the permanent magnet synchronous motor (PMSM). DF can cause obvious changes in the magnetic field of PMSMs. As a result, previous DF diagnosis methods mainly depends on magnetic field analysis. However, conventional analysis methods based on the magnetic potential‐permeability method, sub‐domain method and magnetic equivalent circuit method are not suitable for DF condition. In addition, DF diagnosis is further complicated by various operating conditions. To address these issues, a robust DF diagnosis method is proposed for PMSM based on d‐axis magnetic network model using magnetic field reconstruction. The proposed fault diagnosis method employs magnetic field reconstruction to obtain the radial air‐gap flux density under the open‐circuit condition. Subsequently, a d‐axis magnetic network is established to solve the demagnetisation coefficient matrix in the DF state. Finally, the effectiveness of the proposed method is validated through simulations and experiments. Both results demonstrate that the proposed method can accurately recognise uniform DF and partial DF with multiple demagnetised permanent magnets, exhibiting great robustness against different operating conditions.

Partial cooperative NOMA for improving outage performance of edge users

ABSTRACT Providing reliable service to cell edge users has been a practical challenge for network operators due to the deep fading effects and limited base station (BS) resources. The low received signal strength causes the Quality of Service (QoS) degradation of the cell edge users and hence demands appropriate solutions to improve the user connectivity. To address this issue, this article proposes a two-tier partial cooperative relaying scheme, deployed in a non-orthogonal multiple access (NOMA)-based downlink network that serves the edge users with the minimum required QoS. Comparative performance analysis has been presented for two relaying schemes: amplify-and-forward (AF) and partial decode-and-forward (DF) in terms of outage probability and overall sum rate of the edge users. Additionally, the maximal ratio combining (MRC) diversity technique is integrated with the relaying network to further enhance the QoS of cell edge users. The impact of successive interference cancellation (SIC) on the outage performance has been thoroughly investigated. It has been established through extensive simulation that the partial DF technique is a promising relaying technique to improve the overall performance of cell edge users.

Maximizing the Partial Decode-and-Forward Rate in the Gaussian MIMO Relay Channel

It is known that circularly symmetric Gaussian signals are the optimal input signals for the partial decode-and-forward (PDF) coding scheme in the Gaussian multiple-input multiple-output (MIMO) relay channel, but there is currently no method to find the optimal covariance matrices nor to compute the optimal achievable PDF rate since the optimization is a non-convex problem in its original formulation. In this paper, we show that it is possible to find a convex reformulation of the problem by means of an approximation and a primal decomposition. We derive an explicit solution for the inner problem as well as an explicit gradient for the outer problem, so that the efficient cutting-plane method can be applied for solving the outer problem. Based on these ingredients, we propose a convergent algorithm whose output is an approximation of the globally optimal solution along with a certificate of accuracy in terms of a maximum distance to the true global optimum. In numerical simulations, this distance converged to values close to zero in all considered instances of the problem, showing that the proposed method manages to find the global optimum in all these instances.

Partial-DF Full-Duplex D2D-NOMA Systems for IoT With/Without an Eavesdropper

The massive connectivity and information exchange in the Internet of Things (IoT) pose great challenges to the bandwidth efficiency. To overcome this issue, this article investigates a cooperative full-duplex device-to-device system with nonorthogonal multiple access (NOMA) and partial decode-and-forward (P-DF). In the proposed system, the base station simultaneously transmits signals to all receiving nodes. Two kinds of scenes are considered depending on the locations of the users, where the cases with and without an eavesdropper are respectively studied. According to the P-DF protocol, three kinds of relay forwarding strategies are studied, where only the correctly decoded symbol will be forwarded to the user equipments to avoid performance loss. For the full-duplex relay, it is allowed to forward its own signal by superposing the partial correctly decoded symbol from the previous phase to other users, to further improve the spectral efficiency. Closed-form expressions of the ergodic sum rate, outage probability and secrecy rate are derived. Simulation results verify the analytical results especially in the high signal-to-noise ratio region, and show the superiority of our proposed P-DF-NOMA scheme in terms of outage probability performance.

Use of NOMA for maritime communication networks with P-DF relaying channel

In this paper, a partial de-code-and-forward (P-DF) cooperative relaying network (CRN) with non-orthogonal multiple access (P-DF-CRN-NOMA) for maritime space communications is proposed. Without loss of generality, three kinds of relay forwarding protocols are studied to characterize the superiority of the proposed P-DF-CRN-NOMA scheme, where, after receptions from the coastal base station (BS), the island relay forwards the successful decoded symbols to the ship user to avoid the performance loss provided by the high decoding requirement in decode-and-forward (DF). To further improve the system performance, as well as for a fairness comparison, the maximum ratio combining (MRC) is utilized at the ship user. Specifically, to present the impact of the channel qualities, the scenarios of the weak and strong links that from the source to destination (S-D) are both considered. The closed-form expressions for the outage probability of the P-DF-CRN-NOMA are derived considering the three proposed forwarding cases. Qualitative numerical results corroborating our theoretical analysis, especially for the high signal-to-noise ratio (SNR), show that the proposed P-DF-CRN-NOMA scheme significantly improves the outage probability performance in comparison to the conventional CRN-NOMA schemes. Furthermore, for an increased S-D link, the corresponding outage probability performance will be also better for all the cases.

An Efficient IR-HARQ Power Allocation for Relay-Aided Cellular Networks

Energy-efficient and reliable data transmission is a challenging task in wireless relay networks (WRNs). Energy efficiency in cellular networks has received significant attention because of the present need for reduced energy consumption, thereby maintaining the profitability of networks, which in turn makes these networks “greener”. The urban cell topography needs more energy to cover the total area of the cell. The base station does not cover the entire area in a given topography and adding more number of base stations is a cost prohibitive one. Energy-efficient relay placement model which calculates the maximum cell coverage is proposed in this work that covers all sectors and also an energy-efficient incremental redundancy-hybrid automatic repeat request (IR-HARQ) power allocation scheme to improve the reliability of the network by improving the overall network throughput is proposed. An IR-HARQ power allocation method maximizes the average incremental mutual information at each round, and its throughput quickly converges to the ergodic channel capacity as the number of retransmissions increases. Simulation results show that the proposed IR-HARQ power allocation achieves full channel capacity with average transmission delay and maintains good throughput under less power consumption. Also the impact of relaying performance on node distances between relay station and base station as well as between user and relay station and relay height for line of sight conditions are analyzed using full decode and forward (FDF) and partial decode and forward (PDF) relaying schemes. Compared to FDF scheme, PDF scheme provides better performance and allows more freedom in the relay placement for an increase in cell coverage.

A Novel Genetic Screen Identifies Modifiers of Age-Dependent Amyloid β Toxicity in the Drosophila Brain

The accumulation of amyloid β peptide (Aβ) in the brain of Alzheimer’s disease (AD) patients begins many years before clinical onset. Such process has been proposed to be pathogenic through the toxicity of Aβ soluble oligomers leading to synaptic dysfunction, phospho-tau aggregation and neuronal loss. Yet, a massive accumulation of Aβ can be found in approximately 30% of aged individuals with preserved cognitive function. Therefore, within the frame of the “amyloid hypothesis”, compensatory mechanisms and/or additional neurotoxic or protective factors need to be considered and investigated. Here we describe a modifier genetic screen in Drosophila designed to identify genes that modulate toxicity of Aβ42 in the CNS. The expression of Aβ42 led to its accumulation in the brain and a moderate impairment of negative geotaxis at 18 days post-eclosion (d.p.e) as compared with genetic or parental controls. These flies were mated with a collection of lines carrying chromosomal deletions and negative geotaxis was assessed at 5 and 18 d.p.e. Our screen is the first to take into account all of the following features, relevant to sporadic AD: (1) pan-neuronal expression of wild-type Aβ42; (2) a quantifiable complex behavior; (3) Aβ neurotoxicity associated with progressive accumulation of the peptide; and (4) improvement or worsening of climbing ability only evident in aged animals. One hundred and ninety-nine deficiency (Df) lines accounting for ~6300 genes were analyzed. Six lines, including the deletion of 52 Drosophila genes with human orthologs, significantly modified Aβ42 neurotoxicity in 18-day-old flies. So far, we have validated CG11796 and identified CG17249 as a strong candidate (whose human orthologs are HPD and PRCC, respectively) by using RNAi or mutant hemizygous lines. PRCC encodes proline-rich protein PRCC (ppPRCC) of unknown function associated with papillary renal cell carcinoma. HPD encodes 4-hydroxyphenylpyruvate dioxygenase (HPPD), a key enzyme in tyrosine degradation whose Df causes autosomal recessive Tyrosinemia type 3, characterized by mental retardation. Interestingly, lines with a partial Df of HPD ortholog showed increased intraneuronal accumulation of Aβ42 that coincided with geotaxis impairment. These previously undetected modifiers of Aβ42 neurotoxicity in Drosophila warrant further study to validate their possible role and significance in the pathogenesis of sporadic AD.

On the diversity gain region of the dynamic decode-and-forward relay-assisted Z-channel

In an interference-limited system, the interference forwarding by a relay enhances the interference level and thereby enables the cancellation of the interference. In this work, interference forwarding by a half-duplex dynamic decode-and-forward (HD DDF) relay in a two-user Z-channel is considered. In the two-user Z-channel, one user is interference-limited while the other user is interference-free. The diversity gain region (DGR), which characterizes the tradeoff between the achievable diversity orders between the two users, is an appropriate performance metric for the Z-channel. Closed-form expression for the achievable DGR with the interference forwarding by the HD DDF relay is presented. The multiplexing gain regions (MGRs) where the HD DDF protocol achieves better DGR over the direct transmission scheme, full-duplex decode-and-forward (FD DF) and FD partial DF relay assisted Z- channel are identified. The HD DDF protocol is shown to achieve better DGR than the FD DF and FD PDF relay for a large range of MGR. The achievable DGRs for the HD DDF, FD DF, and FD PDF relay-assisted Z-channel and direct transmission scheme are presented for various interference levels and multiplexing gain pairs.

Full-Duplex Decode-and-Forward Relay-Assisted Interference Management: A Diversity Gain Region Perspective

A two-user Z-channel with a full-duplex (FD) decode-and-forward (DF) relay, where one user is interference-limited while the other user is interference-free, is considered in this paper. The FD-DF relay can decode either a part of the interference or the entire interference. The former is called partial DF (PDF) protocol, and the latter is called complete DF (CDF) protocol. In the case of PDF protocol, the interference-limited user does partial interference cancellation. A closed-form expression for achievable diversity gain region (DGR) with the PDF protocol is presented. Furthermore, achievable DGR of the PDF protocol is optimized under the constraint that the interference-free receiver achieves optimal diversity gain. At low interference levels, the PDF protocol provides better DGR compared to both CDF protocol and direct transmission scheme. As the interference level increases, either the CDF protocol or the direct transmission scheme is shown to achieve better DGR compared to PDF protocol. The multiplexing gain regions where the PDF, CDF, and direct transmission schemes perform well are identified.

On the Maximum Achievable Partial Decode-and-Forward Rate for the Gaussian MIMO Relay Channel

This paper considers the so-called partial decode-and-forward (DF) strategy for the Gaussian multiple-input multiple-output (MIMO) relay channel. Unlike for the DF strategy or point-to-point (P2P) transmission from source to destination, for which Gaussian channel inputs are known to maximize the achievable rates, the input distribution that attains the maximum achievable partial DF rate for the Gaussian MIMO relay channel has remained unknown so far. For some special cases, e.g., for relay channels where the partial DF strategy reduces to the DF or P2P transmission, it could be deduced that Gaussian inputs maximize the rate that can be achieved with the partial DF strategy. For the general case, however, the problem has remained open until now. In this paper, we solve this problem by proving that the maximum achievable partial DF rate for the Gaussian MIMO relay channel is always attained by Gaussian channel inputs. Our proof relies on the channel enhancement technique, which was originally introduced by Weingarten et al. to derive the (private message) capacity region of the Gaussian MIMO broadcast channel. By combining this technique with a primal decomposition approach, we first establish that jointly Gaussian source and relay inputs maximize the achievable partial DF rate for the aligned Gaussian MIMO relay channel. Subsequently, we use a limiting argument to extend this result from the aligned to the general Gaussian MIMO relay channel.

Uplink User-Assisted Relaying in Cellular Networks

We use stochastic geometry to analyze the performance of a partial decode-and-forward (PDF) relaying scheme applied in a user-assisted relaying setting, where an active user relays data through another idle user in uplink cellular communication. We present the geometric model of a network deploying user-assisted relaying and propose two geometric cooperation policies for fast and slow fading channels. We analytically derive the cooperation probability for both policies. This cooperation probability is further used in the analytical derivation of the moments of intercell interference power caused by system-wide deployment of this user-assisted PDF relaying. We then model the intercell interference power statistics using the Gamma distribution by matching the first two moments analytically derived. This cooperation and interference analysis provides the theoretical basis for quantitatively evaluating the performance impact of user-assisted relaying in cellular networks. We then numerically evaluate the average transmission rate performance and show that user-assisted relaying can significantly improve per-user transmission rate despite of increased intercell interference. This transmission rate gain is significant for active users near the cell edge and further increases with higher idle user density, supporting user-assisted relaying as a viable solution to crowded population areas.

Capacity of a class of Dirty-Tape Gaussian orthogonal relay channel with state information at the source and relay

A Gaussian channel with additive interference that is causally known to the transmitter is called a Dirty-Tape Channel (DTC). In this paper, we consider a state-dependent dirty-tape Gaussian relay channel with orthogonal channels from the source to the relay and from the source and relay to the destination. The orthogonal channels are corrupted by two independent additive interferences causally known to both the source and relay. The lower and upper bounds of the channel capacity are established. The lower bound is obtained by employing superposition coding at the source, Partial Decode-and-Forward (PDF) relaying at the relay, and a strategy similar to that used by Shannon at the source and relay. The explicit capacity is characterised when the power of the relay is sufficiently large. Finally, several numerical examples are provided to illustrate the impact of additive interferences and the role of the relay in information transmission and in removing the interference.

General and new inner bound for multiple‐access relay channel and two certain capacity theorems

In this study, the authors obtain a general and new achievable rate region and some certain capacity theorems for multiple-access relay channel (MARC), using partial decode-and-forward (PDF) strategy at the relay, superposition coding at the transmitters and multiple-access and relay channel (RC) decoding schemes. (a) The authors general rate region (i) generalises the achievability part of Slepian-Wolf multiple-access capacity theorem to the MARC, (ii) extends the Cover-El Gamal best achievable rate for the RC with PDF strategy to the MARC, (iii) gives the Kramer-Wijengaarden anticipated rate region for the MARC and (iv) meets max-flow min-cut outer bound for some important classes of the MARC. (b) They extend the results to the Gaussian case as an important practical aspect of MARC and obtain (v) a general and new achievable rate region for Gaussian Slepian-Wolf MARC. Finally, they evaluate their inner bounds for Gaussian MARC numerically, and illustrate specifically that when the relay is closer to the transmitters, their rates are greater than the previous corresponding rates.

Relay Channel with Orthogonal Components and Structured Interference Known at the Source

A relay channel with orthogonal components that is affected by an interference signal that is noncausally available only at the source is studied. The interference signal has structure in that it is produced by another transmitter communicating with its own destination. Moreover, the interferer is not willing to adjust its communication strategy to minimize the interference. Knowledge of the interferer's signal may be acquired by the source, for instance, by exploiting HARQ retransmissions on the interferer's link. The source can then utilize the relay not only for communicating its own message, but also for cooperative interference mitigation at the destination by informing the relay about the interference signal. Proposed transmission strategies are based on partial decode-and-forward (PDF) relaying and leverage the interference structure. Achievable schemes are derived for discrete memoryless models, Gaussian and Ricean fading channels. Furthermore, optimal strategies are identified in some special cases. Finally, numerical results bring insight into the advantages of utilizing the interference structure at the source, relay or destination.

Physical‐layer network coding with limited feedback using orthogonal space–time block codes

SUMMARYThis paper introduces limited feedback technique into physical‐layer network coding (PLNC) scheme, which is the most spectrally efficient protocol in two‐way relay channels, consisted of one relay and two end nodes (sources). Decode‐and‐forward (DF) and partial‐decode‐and‐forward (PDF) strategies are considered for PLNC, and all nodes are assumed to have two antennas to allow transmission by Alamouti's orthogonal space–time block code to provide diversity. In DF, by limited feedback, one of the sources is informed about instantaneous channel state information (CSI) to increase the bit error rate (BER) performance at relay. The closed‐form upper and lower bounds on the bit error probability are derived for binary phase‐shift keying (BPSK) and quadrature PSK (QPSK) modulations and approved via computer simulations. In PDF strategy, each source has to know CSI between relay and the other source for decoding, which causes extra protocol complexity. Moreover, for the system in which all nodes have two antennas, classical PDF strategy does not satisfy orthogonality at the end nodes. Therefore, in this paper, a modified‐PDF (MPDF) strategy with limited feedback is proposed. In MPDF, for decoding at the end nodes, differential phase information between channel fading coefficients having maximum amplitudes is fed back to the sources by relay. This approach enables single‐symbol decoding, besides full diversity, and sources do not need to know CSI between relay and the other source. It is shown via computer simulations that MPDF strategy provides significantly better BER performance than the classical PDF for BPSK and QPSK modulations.Copyright © 2012 John Wiley & Sons, Ltd.

Capacity Bounds and Mapping Design for Binary Symmetric Relay Channels

Capacity bounds for a three-node binary symmetric relay channel with orthogonal components at the destination are studied. The cut-set upper bound and the rates achievable using decode-and-forward (DF), partial DF and compress-and-forward (CF) relaying are first evaluated. Then relaying strategies with finite memory-length are considered. An efficient algorithm for optimizing the relay functions is presented. The Boolean Fourier transform is then employed to unveil the structure of the optimized mappings. Interestingly, the optimized relay functions exhibit a simple structure. Numerical results illustrate that the rates achieved using the optimized low-dimensional functions are either comparable to those achieved by CF or superior to those achieved by DF relaying. In particular, the optimized low-dimensional relaying scheme can improve on DF relaying when the quality of the source-relay link is worse than or comparable to that of other links.

Precoder Design for Multi-Antenna Partial Decode-and-Forward (PDF) Cooperative Systems with Statistical CSIT and MMSE-SIC Receivers

Cooperative communication is an important technology in next generation wireless networks. Aside from conventional amplify-and-forward (AF) and decode-and-forward (DF) protocols, the partial decode-and-forward (PDF) protocol is an alternative relaying scheme that is especially promising for scenarios in which the relay node cannot reliably decode the complete source message. However, there are several important issues to be addressed regarding the application of PDF protocols. In this paper, we propose a PDF protocol and MIMO precoder designs at the source and relay nodes. The precoder designs are adapted based on statistical channel state information for correlated MIMO channels, and matched to practical minimum mean-square-error successive interference cancelation (MMSE-SIC) receivers at the relay and destination nodes. We show that under similar settings, the proposed MIMO precoder design with PDF protocol and MMSE-SIC receivers achieves substantial performance enhancement compared with conventional baselines.

Achievable rate region for multiple-access-relay-networks

The authors introduce a generalisation of the multiple-access-relay-channel (MARC) called multiple-access-relay-network (MARN). The MARC model was first introduced by Kramer et al. and consists of many transmitters, one receiver and only one relay. In the MARN, there are many transmitters, many relays and one receiver. The authors obtained an achievable rate region for MARN by considering partial decode-and-forward (PDF) strategy at the relays. They showed that the region obtained using PDF strategy subsumes the region obtained by Kramer et al. for MARC. In the proposed coding scheme, the authors take advantage of PDF strategy based on regular encoding/backward decoding strategy. They also define semi-deterministic MARN, in which the output of the link between each transmitter and each relay is a deterministic function of the transmitter's input. The authors obtained an inner bound (using our achievable rate region) and also an outer bound on the capacity region of the semi-deterministic MARN and compared them.

On the Gaussian MIMO Relay Channel With Full Channel State Information

This paper addresses the problem of source and relay transmit covariance optimization on the Gaussian MIMO relay channel with full channel state information (CSI), i.e., assuming perfect knowledge of all channels. For full-duplex relaying, we show that the cut-set bound on capacity can be computed as the solution of a convex problem, thus providing a tighter bound than previously published. For time division duplex (TDD) relaying, both upper and lower bounds on capacity are derived, and the transmit covariance matrices are optimized for decode-and-forward (DF) strategies with either partial or full decoding at the relay. A generic procedure is introduced to formulate these problems into a standard convex form, and to solve them efficiently. Suboptimum precoders are also proposed which have a specific matrix structure that either leads to a closed-form expression or at least reduces the dimension of the optimization problem. Practical aspects related to transmit power constraints and CSI availability are then discussed. Finally, simulations in a cellular downlink scenario show that the partial DF strategy can achieve a rate very close to capacity for realistic values of the source to relay SNR, and that the rate loss due to suboptimum precoder structures remains small for typical antenna configurations.

Secrecy Capacity of a Class of Orthogonal Relay Eavesdropper Channels

The secrecy capacity of relay channels with orthogonal components is studied in the presence of an additional passive eavesdropper node. The relay and destination receive signals from the source on two orthogonal channels such that the destination also receives transmissions from the relay on its channel. The eavesdropper can overhear either one or both of the orthogonal channels. Inner and outer bounds on the secrecy capacity are developed for both the discrete memoryless and the Gaussian channel models. For the discrete memoryless case, the secrecy capacity is shown to be achieved by a partial decode-and-forward (PDF) scheme when the eavesdropper can overhear only one of the two orthogonal channels. Two new outer bounds are presented for the Gaussian model using recent capacity results for a Gaussian multiantenna point-to-point channel with a multiantenna eavesdropper. The outer bounds are shown to be tight for two subclasses of channels. The first subclass is one in which the source and relay are clustered, and the eavesdropper receives signals only on the channel from the source and the relay to the destination, for which the PDF strategy is optimal. The second is a subclass in which the source does not transmit to the relay, for which a noise-forwarding strategy is optimal.