Meeting Real-Time Constraint of Spectrum Management in TV Black-Space Access

The TV set feedback feature standardized in the next generation TV system, ATSC 3.0, would enable opportunistic access of active TV channels in future Cognitive Radio Networks. This new dynamic spectrum access approach is named as black-space access, as it is complementary of current TV white space, which stands for inactive TV channels. TV black-space access can significantly increase the available spectrum of Cognitive Radio Networks in populated urban markets, where spectrum shortage is most severe while TV whitespace is very limited. However, to enable TV black-space access, secondary user has to evacuate a TV channel in a timely manner when TV user comes in. Such strict real-time constraint is an unique challenge of spectrum management infrastructure of Cognitive Radio Networks. In this paper, the real-time performance of spectrum management with regard to the degree of centralization of infrastructure is modeled and tested. Based on collected empirical network latency and database response time, we analyze the average evacuation time under four structures of spectrum management infrastructure: fully distribution, city-wide centralization, national-wide centralization, and semi-national centralization. The results show that national wide centralization may not meet the real-time requirement, while semi-national centralization that use multiple co-located independent spectrum manager can achieve real-time performance while keep most of the operational advantage of fully centralized structure.Comment: 9 pages, 7 figures, Technical Repor

OPTYMALIZACJA W BARDZO DUŻYCH BAZACH DANYCH POPRZEZ PARTYCJONOWANIE TABEL

Very large databases like data warehouse slow down over time. This is usually due to a large daily increase in the data in the individual tables, counted in millions of records per day. How do we make sure our queries do not slow down over time? Table partitioning comes in handy, and, when used correctly, can ensure the smooth operation of very large databases with billions of records, even after several years.Bardzo duże bazy danych typu hurtownie danych z czasem zwalniają. Przyczyną zazwyczaj jest duży dzienny przyrost danych w pojedynczych tabelach liczony w milionach rekordów. Co sprawić aby z czasem nasze zapytania nie działały wolniej. Z pomocą przychodzi partycjonowanie tabel, które użyte w prawidłowy sposób może zapewnić sprawne działanie bardzo dużych bazy danych z miliardami rekordów nawet po kilku latach

Meeting Real-Time Constraint of Spectrum Management in TV Black-Space Access

The TV set feedback feature standardized in the next generation TV system, ATSC 3.0, would enable opportunistic access of active TV channels in future Cognitive Radio Networks. This new dynamic spectrum access approach is named as black-space access, as it is complementary of current TV white space, which stands for inactive TV channels. TV black-space access can significantly increase the available spectrum of Cognitive Radio Networks in populated urban markets, where spectrum shortage is most severe while TV whitespace is very limited. However, to enable TV black-space access, secondary user has to evacuate a TV channel in a timely manner when TV user comes in. Such strict real-time constraint is an unique challenge of spectrum management infrastructure of Cognitive Radio Networks. In this paper, the real-time performance of spectrum management with regard to the degree of centralization of infrastructure is modeled and tested. Based on collected empirical network latency and database response time, we analyze the average evacuation time under four structures of spectrum management infrastructure: fully distribution, city-wide centralization, national-wide centralization, and semi-national centralization. The results show that national wide centralization may not meet the real-time requirement, while semi-national centralization that use multiple co-located independent spectrum manager can achieve real-time performance while keep most of the operational advantage of fully centralized structure

Optimising Sargable Conjunctive Predicate Queries in the Context of Big Data

With the continued increase in the volume of data, the volume dimension of big data has become a significant factor in estimating query time. When all other factors are held constant, query time increases as the volume of data increases and vice versa. To enhance query time, several techniques have come out of research efforts in this direction. One of such techniques is factorisation of query predicates. Factorisation has been used as a query optimization technique for the general class of predicates but has been found inapplicable to the subclass of sargable conjunctive equality predicates. Experiments performed exposed a peculiar nature of sargable conjunctive equality predicates based on which insight, the concatenated predicate model was formulated as capable of optimising sargable conjunctive equality predicates. Equations from research results were combined in a way that theorems describing the application and optimality of the concatenated predicate model were derived and proved

Implementación de un algoritmo memético para optimizar la asignación de tablas a unidades de almacenamiento de bases de datos relacionales

En la actualidad, los sistemas de bases de datos son considerados como un componente fundamental para casi cualquier organización, ya que estos sistemas permiten acceder a información puntual de forma segura y rápida, lo cual es clave para una correcta toma de decisiones y una adecuada atención a los usuarios. Sin embargo, debido al rápido desarrollo de las tecnologías de información, cada vez más sistemas de información generan enormes cantidades de datos y necesitan lidiar con estos de forma eficiente y, dado que las bases de datos relacionales juegan un rol vital en muchos sistemas de información, el rendimiento de estos mismos sistemas depende directamente del rendimiento del sistema de base de datos. En ese sentido, se considera crítico aplicar diversos métodos para optimizar el rendimiento del sistema de base de datos. Uno de estos métodos es la asignación de tablas, el cual consiste en distribuir de manera adecuada a las tablas de una base de datos en los dispositivos de almacenamiento disponibles. Dicho método es útil porque permite mejorar el rendimiento del sistema de base de datos y aprovechar de mejor manera los recursos de hardware disponibles. Sin embargo, muchas veces esta tarea se realiza considerando sólo algunas variables o factores al momento de tomar una decisión. Asimismo, existe una ausencia en el empleo de esta técnica por parte de muchos sistemas modernos. Esto, sumado al hecho de que la asignación suele realizarse de manera manual y también a que los estudios presentes en el estado del arte utilizan, en su gran mayoría, soluciones basadas en heurísticas o cálculos simples, las cuales pueden no brindar buenos resultados, conducen a que se realice una deficiente asignación de tablas a unidades de almacenamiento. Esta situación provoca un bajo rendimiento del sistema de base de datos, un deficiente funcionamiento de la entrada y salida de disco y que las tareas de administración sean más propensas a errores. Ante esta situación, se torna necesario el uso de métodos que automaticen y optimicen esta tarea, en ese sentido, el presente trabajo de tesis propone el diseño y la implementación de un algoritmo memético que permita optimizar la asignación de tablas a unidades de almacenamiento de bases de datos relacionales