252 research outputs found
Handover analysis over mobile WiMAX technology.
As new mobile devices and mobile applications continue to growth, so does the data traffic demand for broadband services access and the user needs toward mobility, thereby, wireless application became today the fastest solution and lowest cost implementation unlike traditional wired deployment such as optical fibers and digital lines. WiMAX technology satisfies this gap through its high network performance over the air interface and high data rates based on the IEEE 802.16-2004 standards, this original specification does not support mobility.
Therefore, the IEEE introduces a new standard that enables mobility profiles under 802.16e-2005, from which three different types of handovers process are introduced as hard handover (HHO), macro diversity handover (MDHO) and fast base station switching (FBSS) handover.
The objective of this master thesis is to analyze how the handover process affects network performance. The analysis propose three scenarios, built over OPNET simulator to measure the most critical wireless parameter and performance indicator such as throughput, handover success rate, packet drop, delay and network usage.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format
Characteristics of chicken slaughterhouse wastewater
The chicken slaughterhouse wastewater is a class of wastewater, which is heavily polluted with organic matters including proteins, blood residues, fats and lard. Therefore, the direct discharged of untreated chicken slaughterhouse wastewater into the environment is associated with the occurrence of eutrophication phenomenon. In the present study, the characteristics of chicken slaughterhouse wastewater were investigated to ascertain the role of these wastes in the adverse effect on the environment and natural water system. The parameter tested included biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solid (TSS), total nitrogen (TN), total organic carbon (TOC), orthophosphate (PO4 3-), temperature and pH. The results revealed available high concentrations of BOD (1,341 - 1,821 ± 242.7 mg L1 ), COD (3,154.19 - 7,719.3 ± 2,282.69 mg L-1), TSS (377.67 - 5,462 ± 2,696.1 mg L-1) which have exceeded the EQA1974 standard limits for disposal of wastewater into the environment. The concentrations of TN (162.6 -563.8 ± 215 mg L-1) and PO4 3- (7.047 - 17.111 ± 4.25 mg L-1) were within the range required for microalgae growth which confirm their role in the occurrence of eutrophication phenomenon. It can be concluded that the direct discharge of chicken slaughterhouse wastewater contributes negatively on the environmental biodiversity and thus they should be subjected for an effective treated before the final disposal
Exploring the intra-frame energy conservation capabilities of the horizontal simple packing algorithm in IEEE 802.16e networks: an analytical approach
The power saving capabilities of the mobile devices in broadband wireless networks constitute a challenging research topic that has attracted the attention of researchers recently, while it needs to be addressed at multiple layers. This work provides a novel analysis of the intra-frame energy conservation potentials of the IEEE 802.16e network. Specifically, the power saving capabilities of the worldwide interoperability for microwave access downlink sub-frame are thoroughly studied, employing the well-known simple packing algorithm as the mapping technique of the data requests. The accurate mathematical model, cross-validated via simulation, reveals the significant ability to conserve energy in this intra-frame fashion under different scenarios. To the best of our knowledge, this is the first work providing intra-frame power-saving potentials of IEEE 802.16 networks. Additionally, this is the first study following an analytic approach
On analyzing the intra-frame power saving potentials of the IEEE 802.16e downlink vertical mapping
Worldwide Interoperability for Microwave Access (WiMAX) is generally considered as a competitive candidate networking technology for the realization of the 4G vision. Among the key factors towards its successful and widespread deployment are the effective support of mobility and the provision of mechanisms for enabling service access at a high quality level in an efficient and cost-effective manner. Nonetheless, this effort should take into account and adequately address strict and severe energy limitations that the mobile devices are currently facing. Power saving constitutes an issue of vital importance, as mobile terminals continue to incorporate more and more functionalities and energy-hungry features in order to support the ever increasing user requirements and demands. The standard employs variations of power saving classes in a frame-to-frame basis, while recent power saving mechanisms proposed in related research literature limit their activity in whole frames, neglecting, thus, the intra-frame power saving capabilities. In this work, the intra-frame energy conservation potentials of the mobile WiMAX network are studied and a novel analytical approach is provided, focusing on the downlink direction where the bandwidth allocation involves idle intervals and dynamic inactivity periods. Specifically, we endeavour to accurately analyse the potential energy conservation capabilities in an intra-frame point of view, applying the well-known simple packing algorithm to distribute the available bandwidth to the various subscribers. Our analytical findings are thoroughly cross-validated via simulation, providing clear insights into the intra-frame energy reduction capabilities
Multicast broadcast services support in OFDMA-based WiMAX systems [Advances in mobile multimedia]
Multimedia stream service provided by broadband wireless networks has emerged as an important technology and has attracted much attention. An all-IP network architecture with reliable high-throughput air interface makes orthogonal frequency division multiplexing access (OFDMA)-based mobile worldwide interoperability for microwave access (mobile WiMAX) a viable technology for wireless multimedia services, such as voice over IP (VoIP), mobile TV, and so on. One of the main features in a WiMAX MAC layer is that it can provide'differentiated services among different traffic categories with individual QoS requirements. In this article, we first give an overview of the key aspects of WiMAX and describe multimedia broadcast multicast service (MBMS) architecture of the 3GPP. Then, we propose a multicast and broadcast service (MBS) architecture for WiMAX that is based on MBMS. Moreover, we enhance the MBS architecture for mobile WiMAX to overcome the shortcoming of limited video broadcast performance over the baseline MBS model. We also give examples to demonstrate that the proposed architecture can support better mobility and offer higher power efficiency
Assessment and Real Time Implementation of Wireless Communications Systems and Applications in Transportation Systems
Programa Oficial de Doutoramento en Tecnoloxías da Información e das Comunicacións en Redes Móbiles. 5029V01[Resumo]
Os sistemas de comunicación sen fíos de cuarta e quinta xeración (4G e 5G) utilizan unha capa física
(PHY) baseada en modulacións multiportadora para a transmisión de datos cun gran ancho de banda.
Este tipo de modulacións proporcionan unha alta eficiencia espectral á vez que permiten corrixir de
forma sinxela os efectos da canle radio.
Estes sistemas utilizan OFDMA como mecanismo para a repartición dos recursos radio dispoñibles
entre os diferentes usuarios. Este repartimento realízase asignando un subconxunto de subportadoras a
cada usuario nun instante de tempo determinado. Isto aporta unha gran flexibilidade ó sistema que lle
permite adaptarse tanto ós requisitos de calidade de servizo dos usuarios como ó estado da canle radio.
A capa de acceso ó medio (MAC) destes sistemas encárgase de configurar os diversos parámetros
proporcionados pola capa física OFDMA, ademais de xestionar os diversos fluxos de información de
cada usuario, transformando os paquetes de capas superiores en paquetes da capa física.
Neste traballo estúdase o deseño e implementación das capas MAC e PHY de sistemas de
comunicación 4G ademais da súa aplicabilidade en sistemas de transporte ferroviarios.
Por unha parte, abórdase o deseño e implementación en tempo real do estándar WiMAX. Estúdanse
os mecanismos necesarios para establecer comunicacións bidireccionais entre unha estación base e
múltiples dispositivos móbiles. Ademais, estúdase como realizar esta implementación nunha arquitectura
hardware baseada en DSPs e FPGAs, na que se implementan as capas MAC e PHY. Dado que esta
arquitectura ten uns recursos computacionais limitados, tamén se estudan as necesidades de cada módulo
do sistema para poder garantir o funcionamento en tempo real do sistema completo.
Por outra parte, tamén se estuda a aplicabilidade dos sistemas 4G a sistemas de transporte públicos.
Os sistemas de comunicacións e sinalización son unha parte vital para os sistemas de transporte
ferroviario e metro. As comunicacións sen fíos utilizadas por estes sistemas deben ser robustas e
proporcionar unha alta fiabilidade para permitir a supervisión, control e seguridade do tráfico ferroviario.
Para levar a cabo esta avaliación de viabilidade realízanse simulacións de redes de comunicacións
LTE en contornos de transporte ferroviarios, comprobando o cumprimento dos requisitos de fiabilidade
e seguridade. Realízanse diferentes simulacións do sistema de comunicacións para poder ser avaliadas e
seleccionar a configuración e arquitectura do sistema máis axeitada en función do escenario considerado.
Tamén se efectúan simulacións de redes baseadas en Wi-Fi, dado que é a solución máis utilizada nos
metros, para confrontar os resultados cos obtidos para LTE.
Para que os resultados das simulacións sexan realistas débense empregar modelos de propagación
radio axeitados. Nas simulacións utilízanse tanto modelos deterministas como modelos baseados nos
resultados de campañas de medida realizadas nestes escenarios.
Nas simulacións empréganse os diferentes fluxos de información destes escenarios para comprobar
que se cumpren os requisitos de calidade de servicio (QoS). Por exemplo, os fluxos críticos para o control
ferroviario, como European Train Control System (ETCS) ou Communication-Based Train Control (CBTC), necesitan unha alta fiabilidade e un retardo mínimo nas comunicacións para garantir o correcto
funcionamento do sistema.[Resumen]
Los sistemas de comunicación inalámbricos de cuarta y quinta generación (4G y 5G) utilizan una capa
física (PHY) basada en modulaciones multiportadora para la transmisión de datos con un gran ancho
de banda. Este tipo de modulaciones han demostrado tener una alta eficiencia espectral a la vez que
permiten corregir de forma sencilla los efectos del canal radio.
Estos sistemas utilizan OFDMA como mecanismo para el reparto de los recursos radio disponibles
entre los diferentes usuarios. Este reparto se realiza asignando un subconjunto de subportadoras a cada
usuario en un instante de tiempo determinado. Esto aporta una gran flexibilidad al sistema que le permite
adaptarse tanto a los requisitos de calidad de servicio de los usuarios como al estado del canal radio.
La capa de acceso al medio (MAC) de estos sistemas se encarga de configurar los diversos parámetros
proporcionados por la capa física OFDMA, además de gestionar los diversos flujos de información de
cada usuario, transformando los paquetes de capas superiores en paquetes de la capa física.
En este trabajo se estudia el diseño e implementación de las capas MAC y PHY de sistemas de
comunicación 4G además de su aplicabilidad en sistemas de transporte ferroviarios.
Por una parte, se aborda el diseño e implementación en tiempo real del estándar WiMAX. Se
estudian los mecanismos necesarios para establecer comunicaciones bidireccionales entre una estación
base y múltiples dispositivos móviles. Además, se estudia cómo realizar esta implementación en una
arquitectura hardware basada en DSPs y FPGAs, en la que se implementan las capas MAC y PHY. Dado
que esta arquitectura tiene unos recursos computacionales limitados, también se estudian las necesidades
de cada módulo del sistema para poder garantizar el funcionamiento en tiempo real del sistema completo.
Por otra parte, también se estudia la aplicabilidad de los sistemas 4G a sistemas de transporte
públicos. Los sistemas de comunicaciones y señalización son una parte vital para los sistemas de
transporte ferroviario y metro. Las comunicaciones inalámbricas utilizadas por estos sistemas deben ser
robustas y proporcionar una alta fiabilidad para permitir la supervisión, control y seguridad del tráfico
ferroviario.
Para llevar a cabo esta evaluación de viabilidad se realizan simulaciones de redes de comunicaciones
LTE en entornos de transporte ferroviarios, comprobando si se cumplen los requisitos de fiabilidad y
seguridad. Se realizan diferentes simulaciones del sistema de comunicaciones para poder ser evaluados y
seleccionar la configuración y arquitectura del sistema más adecuada en función del escenario planteado.
También se efectúan simulaciones de redes basadas en Wi-Fi, dado que es la solución más utilizada en
los metros, para comparar los resultados con los obtenidos para LTE.
Para que los resultados de las simulaciones sean realistas se deben utilizar modelos de propagación
radio apropiados. En las simulaciones se utilizan tanto modelos deterministas como modelos basados en
los resultados de campañas de medida realizadas en estos escenarios.
En las simulaciones se utilizan los diferentes flujos de información de estos escenarios para
comprobar que se cumplen sus requisitos de calidad de servicio. Por ejemplo, los flujos críticos para el control ferroviario, como European Train Control System (ETCS) o Communication-Based Train
Control (CBTC), necesitan una alta fiabilidad y un retardo bajo en las comunicaciones para garantizar el
correcto funcionamiento del sistema.[Abstract]
The fourth and fifth generation wireless communication systems (4G and 5G) use a physical layer (PHY)
based on multicarrier modulations for data transmission using high bandwidth. This type of modulations
has shown to provide high spectral efficiency while allowing low complexity radio channel equalization.
These systems use OFDMA as a mechanism for distributing the available radio resources among
different users. This allocation is done by assigning a subset of subcarriers to each user in a given instant
of time. This provides great flexibility to the system that allows it to adapt to both the quality of service
requirements of users and the radio channel state.
The media access layer (MAC) of these systems is in charge of configuring the multiple OFDMA
PHY layer parameters, in addition to managing the data flows of each user, transforming the higher layer
packets into PHY layer packets.
This work studies the design and implementation of MAC and PHY layers of 4G communication
systems as well as their applicability in rail transport systems.
On the one hand, the design and implementation in real time of the WiMAX standard is addressed.
The required mechanisms to establish bidirectional communications between a base station and several
mobile devices are also evaluated. Moreover, a MAC layer and PHY layer implementation is
presented, using a hardware architecture based in DSPs and FPGAs. Since this architecture has limited
computational resources, the requirements of each processing block of the system are also studied in
order to guarantee the real time operation of the complete system.
On the other hand, the applicability of 4G systems to public transportation systems is also studied.
Communications and signaling systems are a vital part of rail and metro transport systems. The
wireless communications used by these systems must be robust and provide high reliability to enable
the supervision, control and safety of rail traffic.
To carry out this feasibility assessment, LTE communications network simulations are performed in
rail transport environments to verify that reliability and safety requirements are met. Several simulations
are carried out in order to evaluate the system performance and select the most appropriate system
configuration in each case. Simulations of Wi-Fi based networks are also carried out, since it is the
most used solution in subways, to compare the results with those obtained for LTE.
To perform the simulations correctly, appropriate radio propagation models must be used. Both
deterministic models and models based on the results of measurement campaigns in these scenarios are
used in the simulations.
The simulations use the different information flows present in the railway transportation systems to
verify that its quality of service requirements are met. For example, critical flows for railway control,
such as the European Train Control System (ETCS) or Communication-Based Train Control (CBTC),
require high reliability and low delay communications to ensure the proper functioning of the system
Recommended from our members
Investigation of efficient resource allocation schemes for WiMAX networks
This thesis was submitted for the degree of Master of Philosophy and was awarded by Brunel University on 9 July 2008.WiMax (Worldwide Interoperability for Microwave Access) is a promising wireless technology with the aim of providing the last mile wireless broadband access designed for both fixed and mobile consumers as an alternative solution to the wired DSL and cable access schemes. The purpose of this research project is to investigate efficient resource allocation algorithms for WiMax. To achieve this goal, we investigate efficient PHY layer Partial Usage of SubCarriers (PUSC) allocation as well as MAC layer piggyback bandwidth request mechanisms. At the PHY layer we proposed improvements on the Uplink and Downlink PUSC subcarrier allocation scheme. For the Uplink PUSC we suggested a method by allocating different frequencies to neighbouring cells in combination with the Integer Frequency Reuse (IFR) and Fractional Frequency Reuse (FFR) in order to reduce interferences and collisions. The simulation results exhibit that collision rates can be reduced to zero for both IFR and FFR patterns with the proposed improvement by assuming that perfect power control is used in the system. In addition, there is no collision at cell edges. The results also show that FFR patterns achieve lower inter-cell interference and higher capacities as compared to the IFR patterns. For the Downlink PUSC we introduced an offset scheme with the purpose of increasing the number of users in the system. At the MAC layer we propose an improvement on the piggyback bandwidth request mechanism by increasing the size of the piggyback bandwidth request in order to reduce the number of bandwidth requests and hence improve the resource utilisation. The simulation results demonstrate that our improved scheme achieves higher throughput, less delay and packet loss rates as compared to the standardised piggyback bandwidth request mechanism
Simulation of Relay modes in IEEE 802.16j Mobile Multi-hop Relay (MMR) WIMAX Networks
Two different relay modes are defined in IEEE 802.16j WIMAX standard: transparent mode and non-transparent mode. The non transparent mode is used to extend the coverage area of base stations, where low cost relay station of equal capacity as that of base station is placed at suitable position. Time taken to accept mobile stations and Bandwidth allocation are main problems in non transparent mode. In this we have studied the IEEE 802.16j standard multi hop relay WIMAX networks. We have used relay stations to extend the coverage of base stations. We have also analyzed the throughput between mobile stations with in the coverage area and outside coverage area of base stations. We have simulated the IEEE 802.16j transparent and non transparent mode multi hop WIMAX relay networks using NCTUns Too
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