Presence Of CFO Research Articles

AlignTrack: Push the SNR Limit of LoRa Collision Decoding

LoRa has been shown as a promising Low-Power Wide Area Network (LPWAN) technology to connect millions of devices for the Internet of Things by providing long-distance low-power communication when the SNR is very low. Real LoRa networks, however, suffer from severe packet collisions. Existing collision resolution approaches introduce a high SNR loss, i.e., require a much higher SNR than LoRa. To push the limit of LoRa collision decoding, we present AlignTrack, the first LoRa collision decoding approach that can work in the SNR limit of the original LoRa. Our key finding is that a LoRa chirp aligned with a decoding window should lead to the highest peak in the frequency domain and thus has the least SNR loss. By aligning a moving window with different packets, we separate packets by identifying the aligned chirp in each window. We theoretically prove this leads to the minimal SNR loss. In practical implementation, we address two key challenges: (1) accurately detecting the start of each packet, and (2) separating collided packets in each window in the presence of CFO and inter-packet interference. We implement AlignTrack on HackRF One and compare its performance with the state-of-the-arts. The evaluation results show that AlignTrack improves network throughput by 1.68 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> compared with NScale and 3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> compared with CoLoRa.

Magnetically tunable enhanced performance of CoFe2O4–PVDF nanocomposite film-based piezoelectric nanogenerator

Flexible piezoelectric nanogenerator (PENG) using a poly(vinylidene fluoride)–cobalt ferrite (PVDF–CFO) nanocomposite film is prepared in which the output power of the PENG device can be tuned by the application of an external magnetic field. Ferromagnetic CFO nanoparticles were prepared by the hydrothermal method and are incorporated in the PVDF matrix using the drop casting technique. The presence of CFO in the PVDF matrix enhances the ferroelectric β phase fraction of PVDF from 59% to 75% and also provides magnetic tunability to the PENG device. With the application of a 2.1 kG field, there is 2.33 times increment in instantaneous output power of the PENG, which is attributed to a decrease in the resistance of the nanocomposite film due to the alignment of the magnetic moment of CFO nanoparticles leading to a reduction in the scattering of mobile charges. These outcomes open up a possibility in piezomagnetotronic materials through the realization of magneto-sensitive multifunctional PENGs, which can be scaled up for fabricating compact, high-performance, portable devices for smart sensor applications.

The oligodendroglial histological features are not independently predictive of patient prognosis in lower-grade gliomas.

The relevance of oligodendroglial histological features to patient prognoses is controversial. 93 LrGGs resected for about 2 decades were re-assessed based on WHO2007 with special interest to pure oligodendroglial diagnosis (oligodendroglioma or anaplastic oligodendroglioma) and presence of CFO features. Those histological features, patients OS, and tumor chromosomal/genetic characteristics were correlated each other in each of the 3 IDH-1p/19q-based molecular groups. There was significant association between 1p19q status with the oligodendroglial histological diagnosis as well as presence of CFO in the entire cohort. The oligodendroglial diagnosis was associated with longer OS in IDHmut/codel group; however, this association was not significant in the multivariate analyses. In IDHmut/noncodel and IDH-wildtype groups, the oligodendroglial diagnosis was not associated with patient OS. Presence of CFO was not associated with patient OS in any molecular groups. Gain of 8q was associated with the oligodendroglial diagnosis in IDHmut/noncodel group. Neither the oligodendroglial diagnosis nor CFO was predictive for the methylation status of the MGMT gene in any molecular groups. The oligodendroglial histological features are not independently predictive of either patient prognosis or chemotherapeutic response in LrGGs, leaving the possibility of marginal favorable association only in IDHmut/codel tumors.

BER analysis and interference mitigation for GO‐OFDMA transmission

SummaryCarrier frequency offset (CFO) results in multiaccess interference and intersymbol interference and degrades the bit error rate performance. Mitigating the effects of CFO always burdens the receiver with respect to architecture and power. This disadvantage increases with increase in number of users. In the present work, bit error rate analysis of multiuser group orthogonal–orthogonal frequency division multiple access scheme for variable rate and single rate over pedestrian channel in the presence of CFO is presented. Through analysis, it is proved that by incorporating carrier interferometry codes in the scheme, CFO effects can be removed without burdening receiver. It is also shown by analysis that effect of CFO is rate dependent. Finally, simulation results are provided to confirm the analytical results.

CRLB-Achieving I/Q Mismatch Estimator for Low-IF Receiver Using Repetitive Training Sequence in the Presence of CFO

This paper presents a method for estimating the in-phase/quadrature-phase (I/Q) mismatch in low-intermediate frequency receivers for orthogonal frequency division multiplexing (OFDM) signals in the presence of carrier-frequency offset. The proposed estimator operates on the repetitive training sequence of the OFDM packet preamble. To derive a practical maximum-likelihood estimator, an invertible mapping operation is applied on the observation vectors, so that a closed-form expression of the likelihood function can be obtained. The proposed estimator is shown to achieve the Cramer Rao lower bound at high image signal power levels. The error variance of the estimator is analyzed, which closely matches simulation results. The uncoded bit-error-rate is shown via simulation to be approximately that of an ideal receiver without I/Q mismatch.