Search results for "IONT"
showing 10 items of 382 documents
What Symbionts Teach us about Modularity
2013
The main goal of Synthetic Biology is to apply engineering principles to biotechnology in order to make life easier to engineer. These engineering principles include modularity: decoupling of complex systems into smaller, orthogonal subsystems that can be used in a range of different applications. The successful use of modules in engineering is expected to be reproduced in synthetic biological systems. But the difficulties experienced up to date with synthetic biology approaches question the short-term feasibility of designing life. Considering the “engineerable” nature of life, here we discuss the existence of modularity in natural living systems, particularly in symbiotic interactions, an…
A metaphysical approach to holobiont individuality: Holobionts as emergent individuals
2019
Holobionts are symbiotic assemblages composed by a host plus its microbiome. The status of holobionts as individuals has recently been a subject of continuous controversy, which has given rise to two main positions: on the one hand, holobiont advocates argue that holobionts are biological individuals; on the other, holobiont detractors argue that they are just mere chimeras or ecological communities, but not individuals. Both parties in the dispute develop their argu-ments from the framework of the philosophy of biology, in terms of what it takes for a ?conglomerate? to be considered an interesting individual from a biological point of view. However, the debates about holobiont individualit…
Optimal MAC PDU Size in IEEE 802.16
2008
In the IEEE 802.16 the number of errors and the MAC PDU size have an impact on the performance of the network. We present a way to estimate the optimal PDU size and we run a number of simulation scenarios to study these parameters and how they impact on the performance of application protocols. The simulation results reveal that the channel bit error rate has a major impact on the optimal PDU size in the IEEE 802.16 networks. Also, the ARQ block rearrangement influences the performance.
Performance Evaluation of the IEEE 802.16 ARQ Mechanism
2007
The IEEE 802.16 technology defines the ARQ mechanism that enables a connection to resend data at the MAC level if an error is detected. In this paper, we analyze the key features and parameters of the ARQ mechanism. In particular, we consider a choice for the ARQ feedback type, a scheduling of the ARQ feedbacks and retransmissions, the ARQ block rearrangement, ARQ transmission window and ARQ block size. We run a number of simulation scenarios to study these parameters and how they impact a performance of application protocols. The simulation results reveal that the ARQ mechanism plays an important role in transmitting data over wireless channels in the IEEE 802.16 networks.
Performance comparison of HARQ and ARQ mechanisms in IEEE 802.16 networks
2008
The IEEE 802.16 technology defines several link level mechanisms to retransmit erroneous data. In this paper we compare the performance of the ARQ and HARQ mechanisms in the IEEE 802.16 networks. Our simulations results show that in general HARQ provides a better performance. However, ARQ can compete successfully with it due to a smaller signaling overhead. Furthermore, since ARQ does not require a dedicated uplink signaling channel for the acknowledgments messages, it results in better resources utilization in the uplink direction.
Link Adaptation Thresholds for the IEEE 802.16 Base Station
2008
The IEEE 802.16 technology defines a number of modulation and coding schemes that the base station can use to achieve the best tradeoff between the spectrum efficiency and the resulting application level throughput. However, the 802.16 specification does not define any particular link level adaptation algorithm, neither does it specify the SNR thresholds to switch between modulation and coding schemes. In this paper we consider a link adaptation model and conduct a number of simulation runs to find transition thresholds for ARQ and HARQ retransmission mechanisms. All the simulations are done with the 802.16 extension for the NS-2 simulator.
Increasing the VoIP Capacity through MAP Overhead Reduction in the IEEE 802.16 OFDMa Systems
2010
One of the main issues with supporting VoIP service over 802.16 networks is the signalling overhead caused by the downlink MAP messages due to frequent transmissions and small packets. To decrease the MAP overhead, the 802.16 standard proposes some mechanisms, such as the compressed MAP and sub-MAPs. In this paper, we show by means of extensive dynamic simulations that sub-MAPs can reduce dramatically the signalling overhead associated with VoIP traffic and significantly improve overall VoIP capacity. At the same time, since sub-MAPs are more sensitive to packet drops, they tend to increase the number of HARQ retransmissions in downlink and transmission delays in the uplink direction.
ARQ parameters for VoIP in IEEE 802.16 networks
2009
IEEE 802.16 standard defines two data retransmission mechanisms. HARQ provides fast retransmissions in cost of slightly increased overhead. On the contrary, ARQ has less overhead in cost of bit longer delays. It is therefore often used with BE connections. In addition to delay tolerant applications, BE can also be used for real-time services. Therefore, in this paper we analyze the ARQ mechanism and provide guidelines on how to set the ARQ parameters to achieve a good balance between the VoIP delay and packet loss.
Wavelet-based video compression: A glimpse of the future?
2004
Masteroppgave i informasjons- og kommunikasjonsteknologi 2004 - Høgskolen i Agder, Grimstad Even though wavelet-based video compression has been an area of research for more than a decade, motion estimation and compensation has been considered complex and inefficient until recently. We have carried out a thorough investigation of existing research work in this field, and found that fundamental problem with wavelet-based temporal removal while obtaining highly scalability (the wavelet-properties of multiresolution structure in combination with embedded coding), has been solved by performing motion compensated temporal filtering within the wavelet domain of a overcomplete three-dimensional li…
Development of a Matlab Toolbox for Mobile Fading Channel Simulators
2007
Masteroppgave i informasjons- og kommunikasjonsteknologi 2007 – Høgskolen i Agder, Grimstad Knowledge of channel behaviours in mobile radio communication is extensively recommended for the study of transmitter/receiver performances. Our intention in this master's thesis is to develop various kinds of mobile fading channel simulators using Matlab. The developed channel simulators were combined into a user-friendly toolbox from which users can easily select well-known channel models to test and to study the performance of mobile communication systems. The toolbox can be integrated into the new release of Matlab software. The toolbox contains channel simulators for spatial shadowing processes,…