Implementasi Filter Pre-Emphasis untuk Transmisi Sinyal Audio pada Sistem Komunikasi FBMC-OQAM

Abstract

High speed data transmision demands broader bandwidth. This has an effect towards the limitation of frequencies spectrum allocation as well as interference. To solve this, multi carrier modulation is one of choices. Having better power spectral density compared to OFDM, the FBMC-OQAM has been chosen as the multi carrier modulation. The FBMC is equipped with Poly Phase Network filter, makes it able to achieve better PSD. Frequently used filter, which is pre-emphasis, is popular in speech processing that is possibly able to be extended in use. Pre-emphasis is also accompanied with de-emphasis filter, which is similar to FBMC. Pre-emphasis filter suppresses low frequency magnitudes and emphasizes higher frequency. By assuming that noise presents in higher frequency, an approachment to protect audio signal by itself is proposed. Random noise is broadband signal where frequencies can have ranges from lower to higher with smaller magnitudes compared to signal. By providing slots in audio higher frequency and magnitudes, random noise occupied those slots with relatively weak magnitudes then sent through the air. At the receiver, a deemphasis filter invert the process to restore signal by deemphasizing higher frequency and removing noise as well. The result shows better BER with this approachment. For example, when Eb/No was 13 dB, BER with and without pre-emphasis are approximately 0.0184 dB and 0.0187 dB, consecutively. It means there was 250 bits or approximately 32 points has been corrected. It shows that pre-emphasis can work along with PPN FBMC filter to gain better BER values. Intisari-Transmisi data berkecepatan tinggi membutuhkan bandwidth yang lebih lebar. Hal ini berdampak pada terbatasnya alokasi spektrum frekuensi dan interferens. Solusinya adalah dengan menggunakan modulasi multi-carrier. Modulasi FBMC-OQAM dipilih sebagai modulasi multi-carrier yang memiliki power spectral density (PSD) lebih baik daripada OFDM. Modulasi ini menggunakan filter poly phase network sehingga PSD lebih baik. Filter pre-emphasis sering digunakan dalam pengolahan sinyal wicara dan diperluas penggunaannya dalam makalah ini.Filter pre-emphasis dilengkapi dengan filter de-emphasis yang identik dengan skema FBMC. Filter ini menekan magnitude pada frekuensi rendah dan memperkuat frekuensi tinggi. Dengan asumsi derau berada pada frekuensi tinggi, sebuah pendekatan untuk melindungi sinyal audio oleh dirinya sendiri ditawarkan. Derau acak (random noise) adalah sinyal broadband yang frekuensinya mulai dari terendah hingga tertinggi, tetapi magnitudenya lebih rendah daripada sinyal audio. Dengan menyediakan ruang spektrum pada frekuensi tinggi sinyal audio yang memiliki magnitude tinggi setelah proses pre-emphasis, derau akan masuk, tetapi magnitudenya rendah, lalu dikirimkan. Pada sisi penerima, filter de-emphasis akan mengembalikan sinyal audio dengan menekan frekuensi tinggi, yang berarti juga menekan derau. Hasil simulasi menunjukkan nilai BER yang semakin baik. Sebagai contoh, untuk Eb/No 13 dB, nilai BER dengan dan tanpa pre-emphasis...

Implementation of Pre-Emphasis Analog Filter on Raspberry Pi Using Zero-Order Hold Discretization as a Pre-Processing to Humanoids’ Commands Recognition

“…It concludes that the analog passive preemphasis filter is always stable. Meanwhile, the zero value from (4), denoted with s0, is shown in (6) which also lies on the left side of the S-complex plane.…”

“…This filter can protect high frequencies from random noise in the air. When received, the signals are reconstructed back to voice data using the de-emphasis filter [6]. Hence, it shows that the role of this filter is significant as it provides a different representation of original signals to be used for feature extraction or data protection.…”

Performance Analysis of FBMC O-QAM System Using Varied Modulation Level

“…Post-processing O-QAM as shown in Fig. 8, has two slightly different structures depending on sub-channel numbers as below [16]. The first operation is the multiplication with the conjugate of θk, n the sequence followed by the operation taking the actual part.…”