Efficient LLR Calculation for Non-Binary Modulations over Fading Channels

Log-likelihood ratio (LLR) computation for non-binary modulations over fading channels is complicated. A measure of LLR accuracy on asymmetric binary channels is introduced to facilitate good LLR approximations for non-binary modulations. Considering piecewise linear LLR approximations, we prove convexity of optimizing the coefficients according to this measure. For the optimized approximate LLRs, we report negligible performance losses compared to true LLRs.Comment: Submitted to IEEE Transactions on Communication

Outcomes after pneumonectomy versus limited lung resection in adults with traumatic lung injury.

Pneumonectomy after traumatic lung injury (TLI) is associated with shock, increased pulmonary vascular resistance, and eventual right ventricular failure. Historically, trauma pneumonectomy (TP) mortality rates ranged between 53 and 100%. It is unclear if contemporary mortality rates have improved. Therefore, we evaluated outcomes associated with TP and limited lung resections (LLR) (i.e., lobectomy and segmentectomy) and aimed to identify predictors of mortality, hypothesizing that TP is associated with greater mortality versus LLR. We queried the Trauma Quality Improvement Program (2010-2016) and performed a multivariable logistic regression to determine the independent predictors of mortality in TLI patients undergoing TP versus LLR. TLI occurred in 287,276 patients. Of these, 889 required lung resection with 758 (85.3%) undergoing LLR and 131 (14.7%) undergoing TP. Patients undergoing TP had a higher median injury severity score (26.0 vs. 24.5, p = 0.03) but no difference in initial median systolic blood pressure (109 vs. 107 mmHg, p = 0.92) compared to LLR. Mortality was significantly higher for TP compared to LLR (64.9% vs 27.2%, p < 0.001). The strongest independent predictor for mortality was undergoing TP versus LLR (OR 4.89, CI 3.18-7.54, p < 0.001). TP continues to be associated with a higher mortality compared to LLR. Furthermore, TP is independently associated with a fivefold increased risk of mortality compared to LLR. Future investigations should focus on identifying parameters or treatment modalities that improve survivability after TP. We recommend that surgeons reserve TP as a last-resort management given the continued high morbidity and mortality associated with this procedure

The First Lunar Ranging Constraints on Gravity Sector SME Parameters

We present the first constraints on pure-gravity sector Standard-Model Extension (SME) parameters using Lunar Laser Ranging (LLR). LLR measures the round trip travel time of light between the Earth and the Moon. With 34+ years of LLR data, we have constrained six independent linear combinations of SME parameters at the level of $10^{-6}$ to $10^{-11}$. There is no evidence for Lorentz violation in the LLR dataset.Comment: 7 pages, presented at the Fourth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, August 200

Potential Capabilities of Lunar Laser Ranging for Geodesy and Relativity

Lunar Laser Ranging (LLR), which has been carried out for more than 35 years, is used to determine many parameters within the Earth-Moon system. This includes coordinates of terrestrial ranging stations and that of lunar retro-reflectors, as well as lunar orbit, gravity field, and its tidal acceleration. LLR data analysis also performs a number of gravitational physics experiments such as test of the equivalence principle, search for time variation of the gravitational constant, and determines value of several metric gravity parameters. These gravitational physics parameters cause both secular and periodic effects on the lunar orbit that are detectable with LLR. Furthermore, LLR contributes to the determination of Earth orientation parameters (EOP) such as nutation, precession (including relativistic precession), polar motion, and UT1. The corresponding LLR EOP series is three decades long. LLR can be used for the realization of both the terrestrial and selenocentric reference frames. The realization of a dynamically defined inertial reference frame, in contrast to the kinematically realized frame of VLBI, offers new possibilities for mutual cross-checking and confirmation. Finally, LLR also investigates the processes related to the Moon's interior dynamics. Here, we review the LLR technique focusing on its impact on Geodesy and Relativity. We discuss the modern observational accuracy and the level of existing LLR modeling. We present the near-term objectives and emphasize improvements needed to fully utilize the scientific potential of LLR.Comment: 7 pages, 7 figures, 2 tables. Talk given at `Dynamic Planet 2005: Monitoring and Understanding a Dynamic Planet with Geodetic and Oceanographic Tools,'' a Joint Assembly of International Associations: IAG, IAPSO and IABO, Cairns, Australia, 22-26 August 200

Successive Cancellation List Polar Decoder using Log-likelihood Ratios

Successive cancellation list (SCL) decoding algorithm is a powerful method that can help polar codes achieve excellent error-correcting performance. However, the current SCL algorithm and decoders are based on likelihood or log-likelihood forms, which render high hardware complexity. In this paper, we propose a log-likelihood-ratio (LLR)-based SCL (LLR-SCL) decoding algorithm, which only needs half the computation and storage complexity than the conventional one. Then, based on the proposed algorithm, we develop low-complexity VLSI architectures for LLR-SCL decoders. Analysis results show that the proposed LLR-SCL decoder achieves 50% reduction in hardware and 98% improvement in hardware efficiency.Comment: accepted by 2014 Asilomar Conference on Signals, Systems, and Computer

The Lender of Last Resort: Some Historical Insights

This paper discusses the role for a lender of last resort (LLR) in preventing banking panics (section I) , then briefly considers classical and more recent concepts of the LLR (section II). Section III examines historical evidence for the U.S. and other countries on the incidence of banking panics and LLR actions, and the record of alternative LLR arrangements in the U.S., Scotland and Canada, as well as the historical record on ailouts. Section IV offers some lessons from history.

Liquidity, Risk Taking, and the Lender of Last Resort

This paper studies the strategic interaction between a bank whose deposits are randomly withdrawn and a lender of last resort (LLR) that bases its decision on supervisory information on the quality of the bank’s assets. The bank is subject to a capital requirement and chooses the liquidity buffer that it wants to hold and the risk of its loan portfolio. The equilibrium choice of risk is shown to be decreasing in the capital requirement and increasing in the interest rate charged by the LLR. Moreover, when the LLR does not charge penalty rates, the bank chooses the same level of risk and a smaller liquidity buffer than in the absence of an LLR. Thus, in contrast with the general view, the existence of an LLR does not increase the incentives to take risk, while penalty rates do.