An abstraction level hierarchy models abstraction-concretization relationships between different types of specifications. The proposed model combines into a single, continuous partially ordered set, ...all types of specifications, such as requirement specifications, design specifications and even the program code. Information theoretic definitions were developed for the concepts of abstraction, concretization and abstraction level. The paper demonstrates how the model can be used to reason about software engineering issues. The purpose of this conceptual paper is to propose an underlying model for software engineering research.
This paper investigates the influence of a variable system load on the performance of the channel estimation in a multicarrier code division multiple access (MC-CDMA) transmission scheme. We consider ...channel estimation based on pilot symbols, which are periodically inserted into the MC-CDMA frame. Starting from the analytical expression of the decision variable, we show the impact of erroneous channel estimation as a function of system load. We derive a simple adaptation rule for the pilot symbol power in order to maintain the signal-to-noise ratio (SNR) loss due to channel estimation errors constant for all system loads. We show that this simple rule enables us to minimize the total transmitted power required at a given bit error rate (BER), particularly for systems with high spreading gain as used in mobile radio channels with high frequency diversity.
In our poster, we propose a hands-on activity intended to educate students to the notion that neither the claim that a software application is free of a certain bug, nor a scientific hypothesis can ...be proven. Yet, we can increase our confidence in either's validity by genuine attempts of falsification.
This paper gives an overview of some so-called link performance models used in system level simulations to determine the link packet error rate (PER) at reduced complexity. A subset of link ...performance models is evaluated in terms of PER prediction accuracy focusing on a single receive and transmit antenna OFDM link with different coding options and channel characteristics. The results demonstrate that a mutual-information based metric which accounts for the modulation alphabet is preferable in the considered cases and, furthermore, applicable to the large class of MIMO-OFDM transmission techniques with linear pre- and post-processing
Interviews with parents of children who were early readers and observation of reading performance in informal settings revealed a number of characteristics shared by the children, including early ...interest in alphabet letters and regular viewing of "Sesame Street" on television. (CL)
Shifting the MIMO Paradigm Gesbert, D.; Kountouris, M.; Heath, R.W. ...
IEEE signal processing magazine,
09/2007, Letnik:
24, Številka:
5
Magazine Article
Multi-user MIMO (MU-MIMO) networks reveal the unique opportunities arising from a joint optimization of antenna combining techniques with resource allocation protocols. Furthermore, it brings ...robustness with respect to multipath richness, allowing for compact antenna spacing at the BS and, crucially, yielding the diversity and multiplexing gains without the need for multiple antenna user terminals. To realize these gains, however, the BS should be informed with the user's channel coefficients, which may limit practical application to TDD or low-mobility settings. To circumvent this problem and reduce feedback load, combining MU-MIMO with opportunistic scheduling seems a promising direction. The success for this type of scheduler is strongly traffic and QoS-dependent, however.
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