Exploiting diversity in wireless channels with bit-interleaved coded modulation and iterative decoding (BICM-ID)

This dissertation studies a state-of-the-art bandwidth-efficient coded modulation technique, known as bit interleaved coded modulation with iterative decoding (BICM-ID), together with various diversity techniques to dramatically improve the performance of digital communication systems over wireless channels. For BICM-ID over a single-antenna frequency non-selective fading channel, the problem of mapping over multiple symbols, i.e., multi-dimensional (multi-D) mapping, with 8-PSK constellation is investigated. An explicit algorithm to construct a good multi-D mapping of 8-PSK to improve the asymptotic performance of BICM-ID systems is introduced. By comparing the performance of the proposed mapping with an unachievable lower bound, it is conjectured that the proposed mapping is the global optimal mapping. The superiority of the proposed mapping over the best conventional (1-dimensional complex) mapping and the multi-D mapping found previously by computer search is thoroughly demonstrated. In addition to the mapping issue in single-antenna BICM-ID systems, the use of signal space diversity (SSD), also known as linear constellation precoding (LCP), is considered in BICM-ID over frequency non-selective fading channels. The performance analysis of BICM-ID and complex N-dimensional signal space diversity is carried out to study its performance limitation, the choice of the rotation matrix and the design of a low-complexity receiver. Based on the design criterion obtained from a tight error bound, the optimality of the rotation matrix is established. It is shown that using the class of optimal rotation matrices, the performance of BICM-ID systems over a frequency non-selective Rayleigh fading channel approaches that of the BICM-ID systems over an additive white Gaussian noise (AWGN) channel when the dimension of the signal constellation increases. Furthermore, by exploiting the sigma mapping for any M-ary quadrature amplitude modulation (QAM) constellation, a very simple sub-optimal, yet effective iterative receiver structure suitable for signal constellations with large dimensions is proposed. Simulation results in various cases and conditions indicate that the proposed receiver can achieve the analytical performance bounds with low complexity. The application of BICM-ID with SSD is then extended to the case of cascaded Rayleigh fading, which is more suitable to model mobile-to-mobile communication channels. By deriving the error bound on the asymptotic performance, it is first illustrated that for a small modulation constellation, a cascaded Rayleigh fading causes a much more severe performance degradation than a conventional Rayleigh fading. However, BICM-ID employing SSD with a sufficiently large constellation can close the performance gap between the Rayleigh and cascaded Rayleigh fading channels, and their performance can closely approach that over an AWGN channel. In the next step, the use of SSD in BICM-ID over frequency selective Rayleigh fading channels employing a multi-carrier modulation technique known as orthogonal frequency division multiplexing (OFDM) is studied. Under the assumption of correlated fading over subcarriers, a tight bound on the asymptotic error performance for the general case of applying SSD over all N subcarriers is derived and used to establish the best achievable asymptotic performance by SSD. It is then shown that precoding over subgroups of at least L subcarriers per group, where L is the number of channel taps, is sufficient to obtain this best asymptotic error performance, while significantly reducing the receiver complexity. The optimal joint subcarrier grouping and rotation matrix design is subsequently determined by solving the Vandermonde linear system. Illustrative examples show a good agreement between various analytical and simulation results. Further, by combining the ideas of multi-D mapping and subcarrier grouping, a novel power and bandwidth-efficient bit-interleaved coded modulation with OFDM and iterative decoding (BI-COFDM-ID) in which multi-D mapping is performed over a group of subcarriers for broadband transmission in a frequency selective fading environment is proposed. A tight bound on the asymptotic error performance is developed, which shows that subcarrier mapping and grouping have independent impacts on the overall error performance, and hence they can be independently optimized. Specifically, it is demonstrated that the optimal subcarrier mapping is similar to the optimal multi-D mapping for BICM-ID in frequency non-selective Rayleigh fading environment, whereas the optimal subcarrier grouping is the same with that of OFDM with SSD. Furthermore, analytical and simulation results show that the proposed system with the combined optimal subcarrier mapping and grouping can achieve the full channel diversity without using SSD and provide significant coding gains as compared to the previously studied BI-COFDM-ID with the same power, bandwidth and receiver complexity. Finally, the investigation is extended to the application of BICM-ID over a multiple-input multiple-output (MIMO) system equipped with multiple antennas at both the transmitter and the receiver to exploit both time and spatial diversities, where neither the transmitter nor the receiver knows the channel fading coefficients. The concentration is on the class of unitary constellation, due to its advantages in terms of both information-theoretic capacity and error probability. The tight error bound with respect to the asymptotic performance is also derived for any given unitary constellation and mapping rule. Design criteria regarding the choice of unitary constellation and mapping are then established. Furthermore, by using the unitary constellation obtained from orthogonal design with quadrature phase-shift keying (QPSK or 4-PSK) and 8-PSK, two different mapping rules are proposed. The first mapping rule gives the most suitable mapping for systems that do not implement iterative processing, which is similar to a Gray mapping in coherent channels. The second mapping rule yields the best mapping for systems with iterative decoding. Analytical and simulation results show that with the proposed mappings of the unitary constellations obtained from orthogonal designs, the asymptotic error performance of the iterative systems can closely approach a lower bound which is applicable to any unitary constellation and mapping

Signal mapping designs for bit-interleaved coded modulation with iterative decoding (BICM-ID)

Bit-interleaved coded modulation with iterative decoding (BICM-ID)is a spectral efficient coded modulation technique to improve the performance of digital communication systems. It has been widely known that for fixed signal constellation, interleaver and error control code, signal mapping plays an important role in determining the error performance of a BICM-ID system. This thesis concentrates on signal mapping designs for BICM-ID systems. To this end, the distance criteria to find the best mapping in terms of the asymptotic performance are first analytically derived for different channel models. Such criteria are then used to find good mappings for various two-dimensional 8-ary constellations. The usefulness of the proposed mappings of 8-ary constellations is verified by both the error floor bound and simulation results. Moreover, new mappings are also proposed for BICM-ID systems employing the quadrature phase shift keying (QPSK) constellation. The new mappings are obtained by considering many QPSK symbols over a multiple symbol interval, which essentially creates hypercube constellations. Analytical and simulation results show that the use of the proposed mappings together with very simple convolutional codes can offer significant coding gains over the conventional BICM-ID systems for all the channel models considered. Such coding gains are achieved without any bandwidth nor power expansion and with a very small increase in the system complexity

Innovations in Water Management for Sustainable Development of Higher Education Institutions: Experience from Ton Duc Thang University, Vietnam

Ton Duc Thang University (TDTU), which was established in 1997, is a fully autonomous public university in Vietnam. After over 22 years of development, TDTU is now the number one university in Vietnam for all aspects. In 2019, TDTU was ranked the 1st in Vietnam and ranked 165th in the world on sustainable development by UI GreenMetric World University Rankings (UI GreenMetric). Among six categories of UI GreenMetric, including: setting and infrastructure, energy and climate change, waste, water, transport, and education, the water category of TDTU achieved 725 points out of 1000 maximum points (72.50%). This paper presents water management of TDTU, focusing on water conservation, water recycling, the use of water efficient appliances and piped water consumption. Specifically, the paper highlights innovations in water management that TDTU has implemented during the past few years. The paper concludes that sustainable water management makes great contribution to sustainable development of a higher education institutio

Class based Influence Functions for Error Detection

Influence functions (IFs) are a powerful tool for detecting anomalous examples in large scale datasets. However, they are unstable when applied to deep networks. In this paper, we provide an explanation for the instability of IFs and develop a solution to this problem. We show that IFs are unreliable when the two data points belong to two different classes. Our solution leverages class information to improve the stability of IFs. Extensive experiments show that our modification significantly improves the performance and stability of IFs while incurring no additional computational cost.Comment: Thang Nguyen-Duc, Hoang Thanh-Tung, and Quan Hung Tran are co-first authors of this paper. 12 pages, 12 figures. Accepted to ACL 202

A modern purification by accelerated solvent extraction and centrifugal partition chromatography and biological evaluation of capsaicin from Capsicum chinense

A special alkaloid compound known as capsaicin, which can only be found in the fruit of the Capsicum plant, was isolated and tested for its anti-inflammatory activity. The purpose of this work is to establish a simple and quick approach for capsaicin purification utilizing centrifugal partition chromatography (CPC) as well as an effective method - accelerated solvent extraction (ASE), for extracting capsaicin from Capsicum chinense. After purification, capsaicin was validated by HPLC-DAD at 281 nm to be > 90% purity. The in vivo anti-inflammatory activity of the isolated capsaicin was also investigated, and the IC50 value of the capsaicin was determined to be 57.61 µg/mL. The current work emphasizes how an ASE and CPC system may combine to extract high-purity capsaicin from Capsicum chinense, which have the anti-inflammatory activity, as we evaluated in the experiment

Improving Treatment Outcome of Pemphigus Vulgaris on Vietnamese Patients by Using Desmoglein Elisa Test

BACKGROUND: Pemphigus Vulgaris (PV) is a chronic disease, is characterized by the presence of flacid bullous in skin and mucosa. There are 2 main autoantibodies against desmoglein3 (Dsg3) and desmoglein1 (Dsg1). AIM: The aims of this study were to evaluate the before and after treatment outcome with corticosteroid, using Desmoglein ELISA test. METHOD: Forty patients with Pemphigus include 36 PV and 4 PF (28 women, 12 women) were enrolled. The titers of Dsg in pemphigus patients by using ELISA test were done before and 1-month treatment RESULTS: Both anti-Dsg1 and anti-Dsg3 levels were significantly reduced after treatment (P < 0.05). The severity of skin lesions was correlated with anti-Dsg1 antibody level and the severity of oral lesions was significantly correlated with anti-Dsg 3 antibody levels (p < 0.05) CONCLUSION: It is recommended that we can predict and improve the outcome of treatment by using Desmoglein ELISA test

The effectiveness of local surgical technique in treatment of axillary bromhidrosis

BACKGROUND: Up to now, surgical excision of apocrine glands still has been a method that yields high treatment results and low rate of odour recurrent for patients, but many people worry about some serious complications that have been observed postoperatively, such as hematoma and skin necrosis. These prolong wound healing, leading to unsightly scars in the axillary fossae. AIM: We conducted this research to investigate the effects and complications of our surgical technique for axillary bromhidrosis. METHODS: Forty-three patients with axillary bromhidrosis were treated. An elliptical incision was made at a central portion of the area marked, with both tips of the ellipse along the axillary crease. The elliptical skin with the subcutaneous tissue was removed en lock. The adjacent skin was undermined to the periphery of the hair-bearing area with straight scissors. The undermined subcutaneous tissue was removed with curved scissors, and the skin was defatted to become a full-thickness skin flap. Any suspected hemorrhagic spots were immediately coagulated electrosurgically. Appropriate drains were placed, and the treated area was covered with thick gauze to each axilla. Arm movement was strictly controlled in the first 3 days post-operatively. RESULTS: Thirty-one patients have been followed up and evaluated for 6 months. 56 out of 62 axillae (90.3%) showed good to excellent results for malodor elimination. All patients reported a reduction in axillary sweating. There were two axillae of skin necrosis and three axillae of hematoma, with one patient receiving an anticoagulant from a cardiologist after the first day of surgery, to treat heart valve disease. The Dermatology Life Quality Index (DLQI) score decreased significantly, and the quality of life improved after the operation. CONCLUSION: Our technique is a simple surgical procedure and easy to perform helping to achieve results for high malodor elimination, with almost no serious complications. Patient’s life quality improved significantly after the operation

Successful Treatment of Freckles by Alex Trivantage Laser Wavelight 755 nm in Vietnamese Patients

OBJECTIVES: This study aims to evaluate the effectiveness of Alex Trivantage laser wavelength 755 nm (ATL) in the treatment of freckles at Hanoi Hospital of Dermatology and Venereology, Vietnam. PATIENTS AND METHODS: A group of 30 patients with freckles were treated by ATL (Alex Trivantage-Candela Co America) with spots size 3 mm, wavelength 755 mm, and energy 5-6 j/cm2. All the patients were treated 2 times with 4-weeks interval. The results were evaluated at 4, 8, and 12 weeks after treatment. The colour of the lesions was evaluated by using Von-Luchan’s chromatic scale and Visia® complex analysis system. Brown spot index (BSI) was calculated by the VISA complexion analysis system devices. The data was analysed by SPSS 16.0. RESULTS: After 2 times of treatment, the lesion colour of all of the patients had been improved. The good and very good levels of improvement were noted in 63.3% of patients; there was 26.7% of them had partial improvement. Brown spots index was significantly improved (39.13 ± 20.66 before and 54.23 ± 16.78 after treatment; p < 0.001). Hyperpigmentation was noted in 6.7% of patients. CONCLUSION: freckles have been improved by treatment with Alex trivantage laser wavelength 755 nm with safety

Using Patch Testing to Improve Therapeutic Outcome in the Treatment of Hand Eczema in Vietnamese Patients

BACKGROUND: Hand eczema is a common chronic and relapsing skin disease with various clinical features. Hand eczema aetiology can be allergic contact dermatitis (ACD), irritant contact dermatitis (ICD), atopic dermatitis (AD) and unknown or combination causes. If the causative agents are not detected treatment of hand eczema will be a failure. A patch test can be useful to detect causative agents in suspected allergic contact hand eczema. Then patients will avoid contacting them. This results in the improvement of hand eczema. In Vietnam, patch test has not been used before, so we conduct this study. AIM: To identify causative allergens by using patch test with 28 standard allergens in consecutive patients. METHODS: A group of 300 HE patients from the National Hospital of Dermatology and Venereology (NHDV) in Vietnam were enrolled in this study. They were divided into 4 groups-ACD, ICD, AD and unknown aetiology. The patient was patch tested with 28 standard allergens to identify the causative agents. RESULTS: Among the 300 HE enrolled patients, ACD accounted for 72.7%, AD and ICD had the same rate of 12.7%. 39.3% of the patients had a positive patch test. Reaction to nickel sulfate was the most common (10.3%), followed by potassium dichromate (9.7%), cobalt (4%) and fragrance mix (3.1%). About one-third of the cases had relevant clinical reactions correlated with the contact agents and clinical history. Males reacted to cement, thiuram mix and formaldehyde more than females, while females reacted to a nickel more than males. CONCLUSIONS: Hand eczema has variable clinical features and diverse aetiology. ACD is an important cause of hand eczema that can be managed with a patch test to detect causative allergens. Nearly 40% of HE cases had positive patch test. Relevant patch test reactions were seen in one-third of the patients. We propose using patch test detect causative agents in suspected allergic contact hand eczema. Then patients will avoid contacting them. This results in the improvement of hand eczema

The Effectiveness of Narrow Band Uvb (Nb-Uvb) In the Treatment of Pityriasis Lichenoides Chronica (PLC) In Vietnam

AIM: This prospective clinical study presents the experiences with NB-UVB monotherapy in the treatment of PLC on Vietnamese patients. METHODS: We enrolled at National Hospital of Dermatology and Venereology (NHDV), Vietnam, 29 PLC patients with generalised disease involving at least 60% of the total body surface (based on Nine’s Rule) and/or failed to respond to other modalities of treatment. Patients were treated with NB-UVB followed the guideline of the psoriatic treatment of AAD-2010, three times weekly. RESULTS: A complete response (CR) was seen in 24 out of 29 PLC patients (82.8%) with a mean cumulative dose of 9760.5 mJ/cm2 after a mean treatment period of 4.6 weeks (13.8 ± 7.4 exposures). Mild side effects were observed: 69% erythema minimum, 55.2% irritation related to dry skin. No severe side effects were seen during the study. No relapses occurred in 24 CR patients within a mean period of 3 months after the last treatment. CONCLUSION: NB-UVB therapy is an effective and safe option for the treatment and management of PLC