In the present article, we propose a novel selected mapping (SLM) scheme based on a Polar coding technique for peak to average power ratio (PAPR) reduction in orthogonal frequency division multiplexing with index modulation (OFDM-IM) systems. The proposed scheme by utilizing random frozen bits in polar codes generates different number of candidate sequences. Then the candidate sequence with the smallest PAPR is selected for transmission. The proposed scheme can be considered as one block in an OFDM-IM system that performs both PAPR reduction and error correction. For a fair comparison, the performance of an OFDM-IM system based on the proposed scheme is compared with a system that carries out the same operations with two separate blocks where a Polar encoder is cascaded with the one for PAPR reduction (such as conventional SLM or PTS), and a Polar coded OFDM-IM system without any PAPR reduction scheme. Moreover, based on our proposed SLM scheme, a novel receiver without using side information (SI) is proposed. This SI free receiver is based on the successive cancellation list (SCL) polar decoding scheme. Simulation results show that as the Polar code can bring both error correction and PAPR reduction capabilities by using our proposed scheme. Also, the proposed SI free receiver can achieve similar bit error rate (BER) performance as that of the ideal case in both additive Gaussian white noise (AWGN) and frequency selective channels.

Au@Pd core–shell nanoplates were synthesized successfully through the heterogeneous, epitaxial growth of Au on Pd nanoplates. The Pd nanoplates were prepared by reducing H₂PdCl₄ with PVP, and then served as seeds for the nucleation of Au atoms formed by reducing HAuCl₄ with citric acid. Characterization of the as-prepared Au–Pd nanoplates by scanning electron microscopy revealed that a Au shell was formed around the Pd nanoplate. In order to avoid agglomeration, the Au@Pd nanoplates were loaded onto reduced graphene to give a Au@Pd/rGO nanohybrid, which exhibited excellent electrocatalytic activity towards the redox of hydroquinone (HQ) and catechol (CC) simultaneously. The linear detection ranges were 0.01–400.00 μM for HQ and 0.10–400.00 μM for CC, with detection limits of 0.01 μM for HQ and 0.10 μM for CC. Because of the excellent performance, lower detection, wider linear range, and better selectivity, the prepared Au@Pd/rGO nanohybrid has more potential applications and has an expected application in the electrochemical sensing field.

Limited edge server resources and uneven distribution of traffic density in vehicular networks result in problems such as unbalanced network load and high task processing latency. To address these issues, we proposed an efficient caching and offloading resource allocation (ECORA) strategy in vehicular social networks. First, to improve the utilization of vehicular idle resources, a collaborative computation and storage resource allocation mechanism was designed using mobile social similarity. Next, with the optimization objective of minimizing the average task processing delay, we studied the combined resource allocation optimization problem and decoupled it into two sub-problems. For the service caching subproblem, we designed a stable matching algorithm by mobile social connections to dynamically update the cache resource allocation scheme for improving the task unloading efficiency. For the task offloading subproblem, a discrete cuckoo search algorithm based on differential evolution was designed to adaptively select the best task offloading scheme, which minimized the average task processing delay. Simulation results revealed that the ECORA strategy outperformed the resource allocation strategy based on particle swarm optimization and genetic algorithm, and reduced the average task processing delay by at least 7.59%. Meanwhile, the ECORA strategy can achieve superior network load balancing.

In this paper, a peak to average power ratio (PAPR) reduction scheme with low complexity and high performance for orthogonal frequency division multiplexing (OFDM) signals is proposed. The proposed scheme is a hybrid PAPR scheme that employs a two-stage cascade structure. The first stage is a post-IFFT stage that can construct a set of high-order quadrature amplitude modulation (QAM) sequences from QPSK or BPSK sequences with the smallest possible number of IFFTs. The second stage is based on an optimal Class-III selected mapping (SLM) scheme which consists of a bank of parallel blocks. Each of these blocks generates more candidate sequences from each of QAM sequences by passing it through a set of parallel sub-blocks that perform circular convolution with perfect sequences and circular shifting with optimum shift values. Simulation results show that the proposed scheme can outperform existing schemes in terms of PAPR reduction with lower complexity.

In this paper, a permutated partial transmit sequence (PTS) scheme is proposed to reduce the peak-to-average-power ratio (PAPR) in polar-coded orthogonal frequency division multiplexing with index modulation (OFDM-IM) systems without side-information (SI) transmission. For generating candidate signals, the proposed PTS method combines two operations of phase rotations and frequency-domain permutations by implementing circular shifting and factor multiplications in time domain, where the phase rotation factors are determined by the frozen bits of polar codes. Additionally, according to the transmitting and polar-coded structures, an SI-free decoder based on successive cancellation lists (SCL) algorithm is developed at the receiving end. Compared with conventional PTS and existing PAPR reduction schemes, the proposed PTS scheme exhibits significantly higher PAPR reduction performance with less complexity. Based on stimulation results, the proposed SI-free receiver is able to achieve error performance similar to that with the receiver utilizing perfect side information in both Additive White Gaussian noise (AWGN) and frequency selective channels.