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

Distributed optimisation for traffic management

This thesis reports on the development of a multi-agent approach to distributed traffic optimisation. In particular, I propose a solution to the dynamic traffic assignment problem in a decentralised manner and then I introduce the new infrastructurelessly decentralised traffic information system. By using this system, each vehicle agent is able to update the current traffic condition through vehicle-to-vehicle communication. For solving dynamic traffic assignment problem, I propose a novel completely decentralised multi-agent coordination algorithm, which is a synergy between dynamic distributed constraint optimisation problem (DynDCOP) algorithm and auction. Using this algorithm, vehicle agent is able to reduce its individual travel time as well as total travel time of overall system. This simulation is carried out in order to evaluate different traffic planning algorithms that include decentralised uncoordination, centralised coordination and decentralised coordination algorithms. Finally, the experimental results show that the performance of proposed decentalised coorindation algorithm is high in comparison to centralised coordination algorithm

THE RELATIONSHIP BETWEEN PUBLIC SERVICE MOTIVATION, WORK ENJOYMENT, AND TASK PERFORMANCE: A PRELIMINARY STUDY OF HEALTHCARE WORKERS IN VIETNAM

This study aimed to examine the impact of health workers' public service motivation during their participation in response to the Covid-19 pandemic at a time of the highest number of infections and deaths in Vietnam. This study was conducted through a cross-sectional survey using an intentional sampling technique (n=200). In addition, Structural Equation Modeling (SEM) was applied to illustrate the proposed hypotheses. We found that compassion in the workplace, self-sacrifice, and attraction to policy-making impacted work enjoyment positively and significantly. In particular, there was a positive and significant relationship between work enjoyment and task performance but no evidence of the relationship between Commitment to the public interest and work enjoyment. This study further demonstrates the importance of public service motivation of health workers in pandemic response, as previous studies have found. This finding suggests that the government and policymakers in Vietnam should develop policies to promote health workers' public service motivation during their engagement in response to the health crisis.&nbsp

CHARACTERISTICS OF QUATERNARY SEDIMENTARY FACIES IN RELATION TO WATER BEARING CAPACITY OF AQUIFERS AND AQUICLUDES IN RED RIVER DELTA, VIETNAM

Joint Research on Environmental Science and Technology for the Eart

SOCIAL ENTREPRENEURSHIP AND ITS BUSINESS MODELS IN FOOD INDUSTRY

The objective of the thesis is to understand social entrepreneurship phenomenon in the food industry and how it generates values for individuals, local communities, and society. The phenomenon is known as a sustainable method that can solve social problems. However, research on social entrepreneurship is more in general from different sectors and regions. Thus, studying in a particular context – food industry to find out what values food social enterprises create and how their business models operate would contribute another perspective for the academy world and provide practices for social entrepreneurs in food industry. A literature review describes central concepts to provide a fundamental knowledge of social entrepreneurship, business model and value creation emphasizing economic and social values. The study uses qualitative content analysis with a case of a non-profit organization (NGO) and theme in-depth interviews conducted with six social entrepreneurs from Southeast Asia and Africa. The findings indicate that innovation, network and human resource play an important role in social business models to generate values for farmers, consumers, and local communities.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

RELATIONSHIP BETWEEN EROSION AND ACCUMULATION OF SEDIMENTS IN COASTAL ZONE OF BINH THUAN PROVINCE-SOUTH CENTRAL OF VIETNAM

Joint Research on Environmental Science and Technology for the Eart

Measuring Adaptive Behaviors in Individuals with Autism Enrolled in Project-Based Therapy

As the number of individuals with Autism Spectrum Disorder (ASD) entering adulthood increases, this population faces limited resources to foster independent living. Therefore, it is crucial to explore innovative interventions that help this population develop the skills necessary to live more independently. This exploratory prospective cohort study evaluated the effectiveness of Autistry Studios, which focuses on improving adaptive behavior skills for adults and adolescents with ASD using project-based therapy. The study used the Brief Adaptive Behavior Scale (BABS), a novel quantitative assessment, to track the development of adaptive behaviors in individuals with ASD within the domains of Executive Functioning (EF), Socialization (SOC), and Self-Regulation (SR). The BABS specifically measures Frequency of adaptive behaviors (FRQ), the Lowest Level of Assistance (LoALow) required, and the Highest Level of Assistance (LoAHigh) required while engaging in project-based therapy. Paired-samples t-tests compared the mean of BABS scores for 11 participants across nine sessions at Autistry Studios. LoALow and LoAHigh Total scores improved significantly from session one to nine. Additional analyses found significant differences in the LoALow and LoAHigh scores in the domains of EF and SOC. Cohen’s d effect sizes for the difference between session one and nine for LoALow and LoAHigh scores were large to very large, suggesting practical improvement in all domains. The results indicate that Autistry’s pre-vocational, project-based therapy program is effective in improving adaptive behavior skills in adults and adolescents with ASD, as measured by the BABS assessment

Breast and cervical cancer screening : knowledge, attitudes, and practices of Vietnamese Canadian women living in Toronto, Ontario / by Tue Tran Nghi Nguyen.

Breast cancer is the most common cancer, and cervical cancer is the second most common cancer, among Vietnamese women in North America. This ranking replicates the order of cancer prevalence among women residing in Vietnam. Unfortunately, Unfortunately, Vietnamese women are less likely to report ever having had recommended screening procedures for these cancers and are more likely to be overdue for them than women in the general populations (Miller, Kolonel, & Bernstein, 1996). Many factors have been highlighted from previous studies to shed light into this cancer prevalence. These factors include but not limited to accessibility of service, lack of knowledge on breast and cervical cancers, inadequate number of female physicians, language barrier, etc. Therefore, the overall purpose of this project is to examine the knowledge, attitudes, and practices of Vietnamese Canadian women ages 40 to 60 toward breast and cervical cancer screenings. Objectives of the Study: 1. To identify the possible barriers in race or ethnicity, culture, and socioeconomic status (SES) that Vietnamese Canadian women face in their efforts to take preventive measures and participate in breast and cervical cancer screening. 2. To make recommendations and develop strategies for ethnic-focused breast and cervical cancer health promotion