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Journey of Cables – From Coppers to Optical Fiber
Published in Vikas Kumar Jha, Bishwajeet Pandey, Ciro Rodriguez Rodriguez, Network Evolution and Applications, 2023
Vikas Kumar Jha, Bishwajeet Pandey, Ciro Rodriguez Rodriguez
Majority of the long-distance communication was provided by analog systems only using frequency-division multiplexing until the early 1980s. However, the development of fiber optics has a very important role in rapidly replacing those analog systems with digital systems, whereas the digital transmission is also carried over the coaxial and microwave systems, where the telephone signals are first converted to digital (quantized and discrete time format) from an analog signal. Digital signal transmission is different from analog one; it has a series of discrete pulses that represent bits as 1 and 0 rather than being a continuously variable wave form. The Bit 1 is represented as high voltage and the Bit 0, as null or low voltage in electrical networks. Whereas Bit 1 is represented by the presence of light and Bit 0 is represented by the absence of light in the optical networks. It is comparatively easier to reproduce the digital signal than an analog signal, and the signal transmission is simpler. Digital transmission needed the signal regenerators rather than dumb amplifiers of analog transmission. The T-1 line of the digital transmission is characterized to carry data at a rate of 1.544 Mbps, and an E-1 line can transport data at a rate of 2.048 Mbps.
Satellite communications
Published in Matthew N. O. Sadiku, Optical and Wireless Communications, 2018
Mesh topology was used by the first satellite networks to be implemented. With time, there was a decline in the use of this topology, but it remains an effective means of transferring information with the least delay. Mesh topology applies to either temporary connections or dedicated links to connect two earth stations. As shown in Figure 8.6b, all full-duplex point-to-point connectivities are possible and provided, as typical of a mesh configuration. If there are N nodes, the number of connections is equal to the permutation of N(N – 1)/2. Mesh networks are implemented at C and Ku bands. The transmission rate ranges from about 64 kbps to 2.048 Mbps (E1 speed). Users have implemented 45 Mbps.
Introduction
Published in P. S. Neelakanta, ATM Telecommunications, 2018
The European counterpart of T-hierarchy is called the CEPT (Conference Europeanne des Postes et Telecommunications) system. It designates rates commencing at the E1 levels. The E-1 level is derived from PCM coding on 30 channels (instead of the 24 channels of its T-1 counterpart). The E-1 rate is 2.048 Mbps. Table 1.1 lists the T and CEPT digital hierarchies.
10T FinFET based SRAM cell with improved stability for low power applications
Published in International Journal of Electronics, 2022
Figure 2 shows the design of cells using CMOS (Yang et al., 2014) in which transistors have the same connections as a conventional cell. The source terminal of E1 is tied to a virtual supply voltage rail VVdd. Enhancement in reading the data can be done by transistors E1–E4, which forms a buffer. RBL and RWL are charged before starting the read operation. If the value on storage node q is ‘0ʹ, then the RBL remains precharged otherwise it will discharge via E2–E3–E4. During the read operation, VVdd is kept at the actual supply voltage for the high value of read SNM, but in the write operation, it is lowered to increase the WSNM. The topology is novel because it can operate the cell in the sub-threshold regime. Before writing the data, both the bit lines are charged to the pre-determined values and the word line to VDD. The cross-coupled inverters weaken during the subthreshold write because of the floating of VVdd. Here, E1 helps in reducing the leakage from the read bit line. Both the transistors E2 and E3 are in OFF condition in the retention mode. For both values of q ‘0ʹor ‘1ʹ, the node qbb is at ‘1ʹ and helps in reducing the leakage.
A Simple and Instructive Experiment Illustrating the Statistical Concepts of Correlated Electrical Noise
Published in IETE Journal of Education, 2022
The vertical scales of both channels were set at the most sensitive 1 mV per division scale and their attenuation ratio at 1:1. The time-base sweep was fixed at 500 ms per division corresponding to the sampling rate of 10 kSa/s. The scope was let run at its ac-coupled normal mode without filtering nor limiting its bandwidth. Under these settings and after a 30 mn warming-up period, the displayed rms values of the channel noises become almost stable within ± 2 µV. The displayed rms values vary swiftly at much higher sampling rates and are thus immeasurable. The rms values of the channel noises e1(t) and e2(t) and those created ee1 + e2(t) and ee1-e2(t) were measured with the channels being open to ambient and shielded by BNC socket coaxial terminators generally used for impedance matching and wave propagation studies in coaxial cables.
Evaluation of multi-GNSS high-rate relative positioning for monitoring dynamic structural movements in the urban environment
Published in Geomatics, Natural Hazards and Risk, 2020
Mosbeh R. Kaloop, Cemal O. Yigit, Ahmed El-Mowafy, Mert Bezcioglu, Ahmet A. Dindar, Jong Wan Hu
Five dual-frequency CHC I80 GNSS receivers were used to test the performance of high-rate GNSS positioning for SHM under different elevation cut-off angle. The four GNSS receivers mentioned above that were mounted on the shake table to collect GNSS observations with 10°, 20°, 30° and 40° satellite cut-off angle. The fifth GNSS receiver was installed approximately 60 m away from the shake table as a base-station for the relative GNSS positioning. GPS (L1 and L2), GLONASS (L1 and L2) and Galileo (E1 and E5) satellite observations were collected at a 20 Hz (0.05 s) sampling rate. The experiment was carried out on 4 April 2019, at the Gebze Technical University and lasted approximately 2 h. The experiment was conducted under open-sky and with calm weather conditions. In order to evaluate the performance of the relative positioning under different satellite elevation cut-off angle, a broad harmonic oscillation set with different amplitudes and frequencies was generated to cover a wide range of possible structural movements. Six experiments with different harmonic oscillations were selected and performed where GNSS results were compared with reference LVDT data. Table 1 summarizes these harmonic oscillation events with their frequency and amplitude values. Furthermore, superimposed harmonic oscillation with three frequencies, namely 0.8, 3.4 and 7.6 Hz, were generated.