Channel estimation, synchronisation and contention resolution in wireless communication networks

In the past decade, the number of wireless communications users is increasing at an unprecedented rate. However, limited radio resources must accommodate the increasing number of users. Hence, the efficient use of radio spectrum is a critical issue that needs to be addressed. In order to improve the spectral efficiency for the wireless communication networks, we investigate two promising technologies, the relaying and the multiple access schemes. In the physical (PHY) layer of the open systems interconnect (OSI) model, the relaying schemes are capable to improve the transmission reliability and expand transmission coverage via cooperative communications by using relay nodes. Hence, the two-way relay network (TWRN), a cooperative communications network, is investigated in the first part of the thesis. In the media access control (MAC) layer of the OSI model, the multiple access schemes are able to schedule multiple transmissions by efficiently allocating limited radio resources. As a result, the contention-based multiple access schemes for contention resolution are explored in the second part of the thesis. In the first part of the thesis, the channel estimation for the two-way relay networks (TWRNs) is investigated. Firstly, the channel estimation issue is considered under the assumption of the perfect synchronisation. Then, the channel estimation is conducted, by relaxing the assumption of perfect synchronisation. Another challenge facing the wireless communication systems is the contention and interference due to multiple transmissions from multiple nodes, sharing the common communication medium. To improve the spectral efficiency in the media access control layer, a self-adaptive backoff (SAB) algorithm is proposed to resolve contention in the contention-based multiple access networks

Formal design of data warehouse and OLAP systems : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Information Systems at Massey University, Palmerston North, New Zealand

A data warehouse is a single data store, where data from multiple data sources is integrated for online business analytical processing (OLAP) of an entire organisation. The rationale being single and integrated is to ensure a consistent view of the organisational business performance independent from different angels of business perspectives. Due to its wide coverage of subjects, data warehouse design is a highly complex, lengthy and error-prone process. Furthermore, the business analytical tasks change over time, which results in changes in the requirements for the OLAP systems. Thus, data warehouse and OLAP systems are rather dynamic and the design process is continuous. In this thesis, we propose a method that is integrated, formal and application-tailored to overcome the complexity problem, deal with the system dynamics, improve the quality of the system and the chance of success. Our method comprises three important parts: the general ASMs method with types, the application tailored design framework for data warehouse and OLAP, and the schema integration method with a set of provably correct refinement rules. By using the ASM method, we are able to model both data and operations in a uniform conceptual framework, which enables us to design an integrated approach for data warehouse and OLAP design. The freedom given by the ASM method allows us to model the system at an abstract level that is easy to understand for both users and designers. More specifically, the language allows us to use the terms from the user domain not biased by the terms used in computer systems. The pseudo-code like transition rules, which gives the simplest form of operational semantics in ASMs, give the closeness to programming languages for designers to understand. Furthermore, these rules are rooted in mathematics to assist in improving the quality of the system design. By extending the ASMs with types, the modelling language is tailored for data warehouse with the terms that are well developed for data-intensive applications, which makes it easy to model the schema evolution as refinements in the dynamic data warehouse design. By providing the application-tailored design framework, we break down the design complexity by business processes (also called subjects in data warehousing) and design concerns. By designing the data warehouse by subjects, our method resembles Kimball's "bottom-up" approach. However, with the schema integration method, our method resolves the stovepipe issue of the approach. By building up a data warehouse iteratively in an integrated framework, our method not only results in an integrated data warehouse, but also resolves the issues of complexity and delayed ROI (Return On Investment) in Inmon's "top-down" approach. By dealing with the user change requests in the same way as new subjects, and modelling data and operations explicitly in a three-tier architecture, namely the data sources, the data warehouse and the OLAP (online Analytical Processing), our method facilitates dynamic design with system integrity. By introducing a notion of refinement specific to schema evolution, namely schema refinement, for capturing the notion of schema dominance in schema integration, we are able to build a set of correctness-proven refinement rules. By providing the set of refinement rules, we simplify the designers's work in correctness design verification. Nevertheless, we do not aim for a complete set due to the fact that there are many different ways for schema integration, and neither a prescribed way of integration to allow designer favored design. Furthermore, given its °exibility in the process, our method can be extended for new emerging design issues easily

The Impact of Platform Social Responsibility on Consumer Trust

The concept of social responsibility has been widely applied incorporates business philosophy to gain the trust of consumers. With the rise of two-side platforms, platforms have popped up the limelight along with the hot topic of the sharing economy. Despite this, we do not know much about the underlying mechanisms of consumer trust. A questionnaire survey was conducted with 263 consumers from China to explore the consequences of platform social responsibility on consumer trust. The results demonstrate that the implementation of social responsibility by platforms significantly increases consumer trust. Additionally, consumer confusion plays a mediating effect, and platform network externality plays a moderating role. Briefly, the platform does not play a dominant role in regulating supply and demand as we might think since the consciousness of consumer groups is rising. Their autonomy to collect information and make decisions after perception cannot be ignored. The study shows that sharing economy platforms should take their social responsibilities into consideration, rather than taking them as a subsidiary role. Platforms should see consumer trust as a key end rather than a means to promote profits

Time-Dependent Performance Modeling for Platooning Communications at Intersection

With the development of internet of vehicles, platooning strategy has been widely studied as the potential approach to ensure the safety of autonomous driving. Vehicles in the form of platoon adopt 802.11p to exchange messages through vehicle to vehicle (V2V) communications. When multiple platoons arrive at an intersection, the leader vehicle of each platoon adjusts its movement characteristics to ensure that it can cross the intersection and thus the following vehicles have to adjust their movement characteristics accordingly. In this case, the time-varying connectivity among vehicles leads to the significant non-stationary performance change in platooning communications, which may incur safety issues. In this paper, we construct the time-dependent model to evaluate the platooning communication performance at the intersection based on the initial movement characteristics. We first consider the movement behaviors of vehicles at the intersection including turning, accelerating, decelerating and stopping as well as the periodic change of traffic lights to construct movement model, and then establish a hearing network to reflect the time-varying connectivity among vehicles. Afterwards, we adopt the pointwise stationary fluid flow approximation (PSFFA) to model the non-stationary behavior of transmission queue. Then, we consider four access categories (ACs) and continuous backoff freezing of 802.11p to construct the models to describe the time-dependent access process of 802.11p. Finally, based on the time-dependent model, the packet transmission delay and packet delivery ratio are derived. The accuracy of our proposed model is verified by comparing the simulation results with analytical results.Comment: This paper has been accepted by IEEE Internet of Things Journa

A phage-displayed peptide recognizing porcine aminopeptidase N is a potent small molecule inhibitor of PEDV entry

Three phage-displayed peptides designated H, S and F that recognize porcine aminopeptidase N (pAPN), the cellular receptor of porcine transmissible gastroenteritis virus (TGEV) were able to inhibit cell infection by TGEV. These same peptides had no inhibitory effects on infection of Vero cells by porcine epidemic diarrhea virus (PEDV). However, when PEDV, TGEV and porcine pseudorabies virus were incubated with peptide H (HVTTTFAPPPPR), only infection of Vero cells by PEDV was inhibited. Immunofluorescence assays indicated that inhibition of PEDV infection by peptide H was independent of pAPN. Western blots demonstrated that peptide H interacted with PEDV spike protein and that pre-treatment of PEDV with peptide H led to a higher inhibition than synchronous incubation with cells. These results indicate direct interaction with the virus is necessary to inhibit infectivity. Temperature shift assays demonstrated that peptide H inhibited pre-attachment of the virus to the cells

4-(4-Nitro­benzene­sulfonamido)pyridinium bromide

In the title compound, C11H10N3O4S+·Br−, the benzene ring makes an angle of 88.4 (2)° with the pyridinium ring. The dihedral angle between the nitro group and the benzene ring is 16.5 (2)°. The ions in the crystal structure are linked by a combination of inter­molecular N—H⋯Br and non-conventional C—H⋯Br and C—H⋯O hydrogen bonds, forming a three-dimensional network