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Power Control
Published in Jerry D. Gibson, The Communications Handbook, 2018
The growing demand for mobile communications is pushing the technological barriers of wireless communications. The available spectrum is becoming crowded and the old analog FDMA (frequency division multiple access) cellular systems no longer meet the growing demand for new services, higher quality, and spectral efficiency. A second generation of digital cellular mobile communication systems are being deployed all around the world. The second generation systems are represented by three major standards: the GSM, IS-136, and IS-95. The first two are TDMA-based digital cellular systems and offer a significant increase in spectral efficiency and quality of service as compared to the first generation systems, e.g., AMPS, NMT, and TACS. IS-95 is based on DS/CDMA technology. The standardization of the third generation systems, IMT-2000 (formerly known as FPLMTS), is being pursued at ITU. Similar efforts are being conducted at regional standardization bodies.
I
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
IS-54 an interim standard of the U.S.-based Telecommunications Industries Association (TIA) for a digital cellular communication system. One of a set of digital cellular systems commonly classified as second generation cellular systems. A standard originally designed to succeed the AMPS cellular standard. This interim standard has now been finalized in the standard known as IS-136. The standard is based on the use of the same channel structure as the AMPS standard (30 kHz channels), similar frequency reuse and concept of hand-off, but with the use of a digital modulation scheme, known as /4-shifted DQPSK, to transmit a digital signal at the rate of approximately 47 kbps on a 30 kHz channel. This signal typically carries three digital voice signals encoded at the rates of 8 kbps, excluding additional overhead bits that are used for the purpose of error correction. IS-95 an interim standard of the U.S.-based Telecommunications Industries Association (TIA) for digital cellular communication systems. One of a set of systems commonly classified as second-generation cellular systems. The standard is based on spread spectrum modulation employing CDMA. This standard makes use of the concepts of power control, soft hand-offs, pilot signals, pilot phase offsets, orthogonal CDMA, and Walsh functions.
Data over Power Line Operations
Published in Gilbert Held, Understanding Broadband over Power Line, 2016
CDMA represents a transmission method where individual data streams are encoded with PRNs and transmitted over the full spectrum allocated for this digital cellular technology. CDMA was originally known as IS-95 and competes with GSM (Global System for Mobile) technology for dominance in cellular communications. The original version of CDMA is now referred to as cdmaOne, and the wideband version of CDMA forms the basis for the evolving third-generation (3G) network. In between, there are several variations of CDMA. In examining CDMA, we will focus our attention on how it operates in comparison to frequency division and time division systems and the advantages associated with its use.
Development of hybrid wavelet-ANN model for hourly flood stage forecasting
Published in ISH Journal of Hydraulic Engineering, 2018
Ashlin Ann Alexander, Santosh G. Thampi, Chithra N. R.
Various reviews on input selection procedures in water resources applications indicate the importance of statistical approaches like autocorrelation analysis and partial autocorrelation analysis for selecting appropriate input variables. Autocorrelation analysis and partial autocorrelation analysis at 95% confidence bands for various lags (in hours) were performed on water level time series of each event identified in the study. The correlation between the original time series values and the corresponding k-lagged values is called autocorrelation of order k. But the identification of an autoregressive model (lags) is better done using partial autocorrelation function as it shuts off past the order of the model. Correlograms and partial autocorrelation function (PACF) plots for two events E3 and E8 are presented in Figures 3–6, respectively. From the autocorrelation statistics and partial autocorrelation statistics of the flood events considered for the study as shown in Table 2, 3 h antecedent water level values were found most significant (the average of all the PACF values) for making forecasts.
Normalised availability importance measures for complex systems
Published in International Journal of Mining, Reclamation and Environment, 2018
Ali Nouri Gharahasanlou, Mohammad Ataei, Reza Khalokakaie, Abbas Barabadi
The graphical trend test for DT2 is shown in Figure 3(A). This graph shows complete conformity to the results of the analytic tests. Decisions about the acceptance or rejection of the null hypothesis of ‘no-autocorrelation’, by the autocorrelation function (ACF) at 95% of confidence level, were made by using autocorrelograms (Figure 3(B)). In this graph ACF values are represented by columns and 95% confidence bounds are represented by upper and lower dashes. As can be seen, the AFC column on time lag is 0.127 and is placed in the confidence level. Therefore, the null hypothesis is accepted.