Robust Lattice Alignment for K-user MIMO Interference Channels with Imperfect Channel Knowledge

In this paper, we consider a robust lattice alignment design for K-user quasi-static MIMO interference channels with imperfect channel knowledge. With random Gaussian inputs, the conventional interference alignment (IA) method has the feasibility problem when the channel is quasi-static. On the other hand, structured lattices can create structured interference as opposed to the random interference caused by random Gaussian symbols. The structured interference space can be exploited to transmit the desired signals over the gaps. However, the existing alignment methods on the lattice codes for quasi-static channels either require infinite SNR or symmetric interference channel coefficients. Furthermore, perfect channel state information (CSI) is required for these alignment methods, which is difficult to achieve in practice. In this paper, we propose a robust lattice alignment method for quasi-static MIMO interference channels with imperfect CSI at all SNR regimes, and a two-stage decoding algorithm to decode the desired signal from the structured interference space. We derive the achievable data rate based on the proposed robust lattice alignment method, where the design of the precoders, decorrelators, scaling coefficients and interference quantization coefficients is jointly formulated as a mixed integer and continuous optimization problem. The effect of imperfect CSI is also accommodated in the optimization formulation, and hence the derived solution is robust to imperfect CSI. We also design a low complex iterative optimization algorithm for our robust lattice alignment method by using the existing iterative IA algorithm that was designed for the conventional IA method. Numerical results verify the advantages of the proposed robust lattice alignment method

Utility of Tokyo Guidelines 2018 in early laparoscopic cholecystectomy for mild and moderate acute calculus cholecystitis: A retrospective cohort study

BackgroundTokyo Guidelines 2018 (TG18) proposed laparoscopic cholecystectomy (LC) for acute calculus cholecystitis (ACC) irrespective of the duration of symptoms. This retrospective study assessed the impact of utility of TG18 in early LC for ACC.MethodsFrom 2018 to 2020, 66 patients with mild (grade I) and moderate (grade II) ACC who underwent early surgery were studied. Subgroup analyses were based on timing of surgery and operation time.ResultsA total of 32 and 34 patients were operated within and beyond 7 days since ACC onset. More patients with grade II ACC were in the beyond 7 days group (P < 0.05). More patients with enlarged gallbladder were in the within 7 days group (P < 0.05). The duration of symptoms to admission, symptoms to LC, and operation time were longer in the beyond 7 days group (P < 0.05). There were no significant differences regarding intraoperative blood loss, conversion to bail-out procedures, complication rate, hospital stay, and cost between the two groups (P > 0.05). Longer operation time was significantly associated with duration of symptoms to admission, symptoms to LC, and conversion to laparoscopic subtotal cholecystectomy (LSC) (P < 0.05).ConclusionIn a subset of carefully selected patients, applying TG18 in early LC for mild and moderate ACC results in acceptable clinical outcomes. Standardized safe steps and conversion to LSC in difficult cases are important

Improved Multiuser Detectors Employing Genetic Algorithms in a Space-Time Block Coded System

Enhanced genetic algorithms (GA) applied in space-time block coded (STBC) multiuser detection (MUD) systems in Rayleigh flat-fading channels are reported in this paper. Firstly, an improved objective function, which is designed to help speed up the search for the optimal solution, is introduced. Secondly, a decorrelating detector (DD) and a minimum mean square error (MMSE) detector have been added to the GA STBC MUD receiver to create the seed chromosome in the initial population. This operation has improved the receiver performance further because some signal information has been intentionally embedded in the initial population. Simulation results show that the receiver employing the improved objective function and the DD or MMSE detector can converge faster with the same bit error rate (BER) performance than the receiver with the initial population chosen randomly. The total signal-to-noise ratio (SNR) improvement contributed by these two modifications can reach 4 dB. Hence the proposed GA receiver is a promising solution of the STBC MUD problem

System Performance of Concatenated STBC and Block Turbo Codes in Dispersive Fading Channels

A new scheme of concatenating the block turbo code (BTC) with the space-time block code (STBC) for an OFDM system in dispersive fading channels is investigated in this paper. The good error correcting capability of BTC and the large diversity gain characteristics of STBC can be achieved simultaneously. The resulting receiver outperforms the iterative convolutional Turbo receiver with maximum- a-posteriori-probability expectation maximization (MAP-EM) algorithm. Because of its ability to perform the encoding and decoding processes in parallel, the proposed system is easy to implement in real time

Iridoid Glucosides and Diterpenoids from <i>Caryopteris glutinosa</i>

Five new iridoid glucoside derivatives (<b>1</b>–<b>5</b>), three new diterpenoids (<b>7</b>, <b>12</b>, and <b>15</b>), and 11 known compounds were isolated from the aqueous EtOH extract of <i>Caryopteris glutinosa</i>. Cell-based estrogen biosynthesis assays indicated that caryopteriside C (<b>3</b>) and caryopterisoid B (<b>12</b>) promote the biosynthesis of estrogen E2, with EC₅₀ values of 11.1 and 8.0 μM, respectively, in human ovarian granulosa-like KGN cells via upregulating the expression of aromatase