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"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 For these channels the simple model of AWGN is no longer valid and one must consider more practical and complex channel models.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)"

"The BER performance of trellis coded (TC) 8PSK with 2-branch selection (SC) and maximal ratio combining (MRC) diversities on mobile satellite communication system, which channel characterized by Nakagami fading channel is investigated. The special case of 2 branch SC and MRC diversities on independent and spatially correlated Nakagami fading are analyzed in detail, It is shown that the BER performance of TC 8PSK with diversity is better than that system without diversity, and the BER performance of system with diversity increases with increasing the Nakagami fading parameter m. Although the correlation between branches causes signal-to-noise ratio (SNR) loss relative to uncorrelated fading case for 2 branches SC and MRC diversities, the SC and MRC diversities can lead the diversity gain, that is, the improvement of BER performance of TC 8PSK with diversity is obtained over the TC 8PSK without diversity. In addition, the effect of antenna separation which causes cross correlation between the fading signals envelops on the performance of TC 8PSK with 2 branch SC and MRC diversities is also considered."

"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."

"Untuk memperluas jangkauan layanan komunikasi VHF penerbangan saat ini, maka perlu dikembangkan sistem komunikasi VHF berbasis satelit. Penelitian ini bertujuan untuk mensimulasikan dan menganalisis komunikasi suara pada AMS(R)S frekwensi VHF (117,975 - 137 MHz) menggunakan satelit LEO sesuai dengan studi yang sedang berlangsung oleh ICAO dan ITU. Perhitungan link budget dengan parameter gain antenna pesawat = -1 dBi, gain antenna satelit = 8 dBi, RF pesawat = 16 watt dan RF satelit = 85 watt, mendapatkan nilai sensitivitas minimum penerima satelit = -107 dBm dan C/Nup maksimum = 25,56 dB serta nilai sensitivitas minimum penerima pesawat = -93 dBm dan C/Ndown maksimum = 38,65 dB. Jika dihitung link budget end-to-end (loopback: pesawat-satelit-pesawat) di dapat nilai maksimum C/Ntotal = 14,92 dB dan Eb/No = 14 dB. Penelitian komunikasi suara dilakukan dengan menggunakan ilustrasi kanal AWGN nilai Eb/No dari 4 dB hingga 10 dB sehingga didapatkan unjuk kerja audio link VHF yaitu nilai PNSR dan MSE. Dari hasil penelitian didapat bahwa nilai PSNR dan MSE sangat tergantung dari nilai Eb/No link kanal AWGN. Semakin tinggi nilai Eb/No makan nilai PSNR dan MSE semakin bagus. Sementara uji Mean Opinion Score dilakukan untuk menilai unjuk kerja link berdasar uji pendengaran langsung. Dari Uji MOS di dapat bahwa unjuk kerja yang menghasilkan nilai MOS di atas 3 adalah pada nilai Eb/No 8 dB ke atas untuk data tanpa kompresi, kompresi CELP-16 kbps dan keluarga Wavelet yaitu Daubechies-12, Coiflet-5, Symlet-10 dan Biorthogonal-2.6. Sementara kompresi CELP 9,6 kbps nilai MOS lebih dari 3 didapat pada nilai Eb/No 10 dB. Kompresi CELP 4,8 kbps tidak pernah mendapatkan nilai MOS lebih dari 3 walapun pada nilai Eb/No tertinggi 10 dB pada percobaan ini. Dari penelitian ini maka nilai Eb/No link satelit AMS(R)S VHF yang akan dibangun untuk komunikasi penerbangan harus mendapatkan nilai perhitungan link budget end-to-end komunikasi minimal sebesar 8 dB. Ini belum termasuk margin system yang biasanya ditetapkan sebesar 2 hingga 3 dB.

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To expand the coverage range of current VHF aviation communication services, it is necessary to develop a satellite-based VHF communication system. This research aims to simulate and analyse voice communication through AMS(R)S satellite VHF frequencies (117,975 - 137 MHz) using LEO orbit, in accordance with the ongoing studies by ICAO and ITU. Link budget calculations, considering the aircraft antenna gain of -1 dBi, satellite antenna gain of 8 dBi, aircraft RF of 16 watts, and satellite RF of 85 watts, yield a minimum satellite receiver sensitivity of -107 dBm and maximum C/Nup of 25.56 dB, as well as a minimum aircraft receiver sensitivity of -93 dBm and maximum C/Ndown of 38.65 dB. Calculating the end-to-end link budget (loopback: aircraft-satellite-aircraft) results in a maximum C/Ntotal of 14.92 dB and Eb/No of 14 dB. Research of voice communication is performed by using an AWGN channel illustration with Eb/No values ranging from 4 dB to 10 dB, thus obtaining the performance indicators of VHF audio link are PSNR and MSE values. The research results show that the PSNR and MSE values are highly dependent on the Eb/No values of the AWGN channel link. Higher Eb/No values result in better PSNR and MSE values. Mean Opinion Score (MOS) testing is conducted to evaluate the link performance based on direct listening tests. The MOS testing reveals that the performance yielding MOS scores above 3 is achieved with Eb/No values of 8 dB and above for uncompressed data, CELP-16 kbps compression and the mother wavelet compression, including Daubechies-12, Coiflet-5, Symlet-10, and Biorthogonal-2.6. Meanwhile, the CELP-9,6 kbps achieves a MOS score above 3 at an Eb/No value of 10 dB. The CELP compression at 4,8 kbps does not achieve a MOS score above 3, even at the highest Eb/No value of 10 dB in this experiment. Based on this research, the Eb/No value for the AMS(R)S VHF satellite link to be established for aviation communication should achieve a minimum end-to-end link budget calculation of 8 dB. This does not yet include the system margin typically set at 2 to 3 dB"