Hasil Pencarian  ::  Simpan CSV :: Kembali

"Buku yang berjudul "Communication system engineering handbook" ini merupakan sebuah buku panduan mengenai sistem teknik komunikasi. "

"ABSTRAKPermintaan untuk transfer data seluler telah mendorong pengembangan teknologi, termasuk komunikasi nirkabel optik, seperti komunikasi cahaya tampak atau visible light communication (VLC). Kondisi tersebut turut memberikan kontribusi konsumsi daya yang jauh lebih tinggi, yang berarti peningkatan emisi karbon. VLC adalah solusi alternatif untuk komunikasi hijau karena aplikasi potensial untuk penerangan dan transfer data secara bersamaan. Dalam penelitian ini, penulis mempelajari sistem VLC sederhana, yang terdiri dari dua sisi, untuk memahami kinerjanya untuk transmisi data digital. Bagian pertama dari ujung transmisi terdiri dari mikrokontroler dan LED. Bagian kedua dari ujung penerima terdiri dari tiga jenis fotodioda (fotodioda, PIN, dan Avalanche photodiode) dan mikrokontroler. Penelitian ini mempertimbangkan modulasi OOK, ruang gelap untuk menghindari kebisingan dari sumber cahaya lainnya, dan tiga variabel spektrum panjang gelombang, clock rate, dan jarak. Pengamatan parameter bit-error-rate atau BER dan daya menunjukkan bahwa BER rata-rata LED dalam warna putih memiliki BER lebih kecil daripada LED merah, hijau, dan biru, yang masing-masing 0,377, 0,412, 0,387, dan 0,387. Daya yang diterima oleh masing-masing jenis fotodioda menunjukkan LED dalam warna putih memiliki daya lebih besar dibandingkan LED merah, hijau, dan biru.

---

ABSTRACT

Demand for mobile data transfer has driven developing technologies, including optical wireless communications, such as visible light communication (VLC). The high demand has contributed much higher power consumption, which means an increase in carbon emission as well. VLC is an alternative solution for green communication because of its potential applications for both lighting and data transfer simultaneously. In this study, the authors study a simple VLC system, which consists of two sides, to understand its performance for digital data transmission. The first part of the transmitting end consists of a microcontroller and an LED. The second part of the receiving end consists of three types of photodiodes (photodiodes, PINs, and Avalanche photodiodes) and microcontrollers. This research considers OOK modulation, a darkroom to avoid noise from other light sources, and three variables of wavelength spectrums, clock rates, and distances. Parameter observation of bit-error-rate or BER and power shows that the average BER of LED in white color has smaller BER than red, green, and blue LED, which 0.377, 0.412, 0.387, and 0.387, respectively. The power received by each type of photodiode shows LED in white has more power than the red, green, and blue LED."

"The simplest model that is frequently used for a transmission channel is the additive white Gaussian noise (AWGN) channel model. In this model the received signal is the sum of the transmitted signal and Gaussian noise. The simple channel model has great theoretical and practical importance and is an accurate model for many communication channels, such as satellite and deep space communication channels. In many communication systems, however, the channels are subject to various impairments in addition to the additive noise. For these channels the simple model of AWGN is no longer valid and one must consider more practical and complex channel models. One of the such channel types which frequently occur in radio communication is the fading channel.

In mobile radio communication system, the propagation between a base and a mobile station is not only by a direct line-of-sight path, but via many paths. These propagation paths depend largely on the. scattered reflection from many obstacles near the base and mobile stations. The received signal, at any place, consist of a large number of waves arriving from many directions. These multipath waves interfere and produce a varying field strength. The base station receiver experience similar fading as the mobile transmitter moves. The signal fluctuation rate is proportional to the vehicle speed. In many fading channels, in addition to the diffused multipath fading, there exists a dominant line-of-sight (direct) signal component. Denoting the direct component by Acos(2πfct), the received signal then can be written as r(t)= (A + a1 (t)) cos(2πfct) + aQ sin(2πfct)"

"Trellis coded modulation (TCM) formats with their excellent bandwidth and power efficiency have been widely employed in various communication systems. For mobile satellite communications, trellis coded (TC) M-ary phase shift keying (MPSK) is the primary candidate modulation technique. In the first generation mobile satellite systems, co-channel interference (CCI) does not pose a serious problem. However, second generation systems are expected to reuse frequency to increase the orbit slot spectral efficiency. Then the CCI from adjacent beams and adjacent satellite will be dominant factor determining the system performance and overall capacity. Mobile satellite communication is also suffered from strong variations of the received signal power due to the multipath fading. Typically, mobile satellite channels are modeled as Rician or Nakagami fading; that is the received signal consists of a constant line of sight signal component and a Rayleigh distributed diffuse signal component. Therefore, the performance of system on mobile satellite channels is subject to both fading and CCI.TCM and antenna diversity are two attractive methods to combat fading and CC1 effects in the mobile satellite communication systems. The research focuses on the using of TCM and antenna diversity to combat the fading and CCI effects on mobile satellite system, and analyze their performance characterized by bit error rate (BER). Because of multipath propagation , the mobile satellite communication channel is modeled as a Rician or Nakagami fading channel. This report, the BER performance of TC asymmetric MPSK with CCI and TC asymmetric MPSK with diversity on mobile satellite communication systems will be investigated and analyzed.First, the BER performance of TC- asymmetric MPSK in the presence of undesired CCI with multiple interferers and fading channel is investigated. The fading statistic for desired signal is Nakagami fading and the undesired interference signals are Rayleigh fading. We assume that all the interferers are unmodulated because most of errors are produced by Rayleigh fading itself rather than the modulating sequence. This model assumes that all interfering signals have aligned symbol timing and no cross channel interference symbol interfering (ISi) effects. The desired signal is assumed to have Nakagami distribution implying that a dominant multipath exists in transmission. The desired and the interfering carrier have no phase coherence. We derive the BER performance of TC asymmetric MPSK in the presence CCI and fading channels by using the first error event method. It is shown that the BER performance of TC asymmetric MPSK in the presence of CCI is better than that of system with asymmetric MPSK. The BER performance of TC asymmetric MPSK is improved as increasing either the Nakagami fading parameter or the value of signal-to-interference ratio (SIR). As the Nakagami fading parameter is increased the phase signal of MPSK is also increased.Second, the BER performance of TC MPSK with 2 branch selection combining (SC) and maximal ratio combining (MRC) diversities on independent and spatially correlated Nakagami fading channel are investigated. The upper bound bounds using the transfer function bounding technique are derived and several numerical results are shown. Is shown that the BER performance of TC 8PSK with MRC diversity is better than that of system with SC diversity. Although the correlation between branches causes the signal-to-noise ratio (SNR) loss (relative to independent fading case) for SC and MRC diversities, the diversity can lead to achieve the diversity gain compared to the system without diversity.Third, the BER performance of TC 8PSK in the presence of undesired CCI with multiple interferers and fading channel is investigated by using computer simulation. The fading statistic for desired signal is Nakagami fading and the undesired interference signals are characterized by Rayleigh fading. The I3ER performance of TC 8PSK in the presence CC1 and fading channels is simulated by using the first error event method. It is shown from the result that the simulation result of the performance of TC 8PSK in the presence CCI and fading channels is closed to the analytical result."