Low-Complexity PAPR Minimization for Symbol Level Precoded Multi-User MISO-OFDM System

This paper proposes a method exploiting constructive interference (CI) to reduce the transmit signal’s peak-to-average power ratio (PAPR), while keeping the total transmission power as low as possible. An optimization problem that jointly performs power minimization and PAPR reduction is formulated, which is however difficult to solve directly due to the non-convex PAPR constraint. To obtain a feasible solution in low complexity, by using the vectorization method and introducing a regularization factor, we relax the PAPR constraint. The original optimization problem is transformed into a convex problem that can be solved with an improved fast iterative shrinkage-thresholding algorithm (FISTA). Numerical results are presented to show 1dB savings in terms of transmission power and 52% savings in terms of PAPR compared with state-of-the-art PAPR minimization techniques

Bromelain and Cardiovascular Risk Factors in Diabetes: An Exploratory Randomized, Placebo Controlled, Double Blind Clinical Trial

Objective: The objective of this trial was to assess whether the dietary supplement (bromelain) had the potential to reduce plasma fibrinogen and other Cardiovascular Disease (CVD) risk factors in patients with diabetes. Methods: This randomized placebo controlled, double blind, parallel design, efficacy study was carried out in China and investigated the effect of 12 weeks of bromelain (1.05g/day) on plasma fibrinogen . This randomized controlled trial (RCT) recruited 68 Chinese diabetic patients (32 males and 36 females; Han origin, mean age of 61.26 years (Standard Deviation, 12.62 years)) with at least one CVD risk factor. Patients were randomized into either bromelain or placebo group. While bromelain group received bromelain capsule, the placebo group received placebo capsule which consisted inert ingredient and has no treatment effect. Patients and researcher were blinded and did not know whether they received bromelain or placebo capsules. Plasma fibrinogen, CVD risk factors and anthropometric indicators were determined at baseline and at 12 weeks. Results: The change in the fibrinogen level in the placebo group at the end of the study showed a mean reduction of 0.36g/L (Standard Deviation (SD) 0.96g/L) compared with the mean reduction of 0.13g/L (SD 0.86g/L) for the bromelain group. However, there was no significant difference in the mean change in fibrinogen between the placebo and bromelain groups (mean difference=0.23g/L (SD 0.22g/L), p=0.291). Similarly, the difference in mean change in other CVD risk factors (blood lipids, blood pressure), blood glucose, C - reactive protein (CRP) and anthropometric measures between the bromelain and placebo groups was also not statistically significant. Conclusions: This RCT failed to show a beneficial effect in reducing fibrinogen or influencing other selected CVD risk factors but suggests other avenues for subsEquent research on bromelain

Probabilistic Constructive Interference Precoding for Imperfect CSIT

This paper proposes a stochastic-robust constructive interference (CI) precoding scheme for downlink multi-user MISO systems, assuming that channel state information (CSI) at the transmitter side (CSIT) is contaminated by Gaussian-distributed uncertainties. Our objective is to minimize the total transmit power under users' quality-of-service constraints: formulating CI at each user with high probabilities for a given target signal-to-noise ratio (SINR). We first analyze the probability of CI under imperfect CSIT. A series of approximations are then developed, transforming the intractable stochastic CI constraints into determined convex constraints. The non-convex stochastic-robust CI power minimization (CIPM) problem is then converted into second-order cone programming. We show that we could create tightened or relaxed approximations by changing the parameters, enabling us to find upper-bounds and lower-bounds for the original stochastic CIPM problem. The best parameter values corresponding to the tightest upper and lower bounds are also discussed and obtained. Simulation results show that the proposed methods reasonably approximate the stochastic CIPM problem. Using the given parameter values, it can guarantee the required probability of CI for each user under acceptable channel uncertainties and outperform the existing robust CI precoding in terms of both transmit power and feasibility rate. The small gap between the upper and lower bounds also shows that the proposed method does not cause too much performance loss

Multiplexing More Data Streams in the MU-MISO Downlink by Interference Exploitation Precoding

In this paper, we focus on the constructive interference (CI) precoding for the scenario when the number of streams simultaneously transmitted by the base station (BS) is larger than that of transmit antennas at the BS, and derive the optimal precoding structure by employing the pseudo inverse. We show that the optimal pre-scaling vector in IE precoding is equal to a linear combination of the right singular vectors that correspond to zero singular values of the coefficient matrix. By formulating the dual problem, we further show that the optimal precoding matrix can be expressed as a function of the dual variables in a closed form, and an equivalent quadratic programming (QP) formulation is derived for computational complexity reduction. Numerical results validate our analysis and demonstrate significant performance improvements for interference exploitation precoding in the considered scenario