Perancangan Sistem Komunikasi Orthogonal Frequency Division Multiplexing Berbasis Software Defined Radio

Benedicta Clarissa Cayaditta Wibawa, Ir. Sigit Basuki Wibowo, S.T., M.Eng., Ph.D., IPM. ; Ir. Wahyu Dewanto, M.T.

2025 | Skripsi | TEKNIK ELEKTRO

Pesatnya perkembangan teknologi telah mendorong sistem komunikasi digital menjadi fondasi transmisi data berkecepatan tinggi dengan konektivitas yang masif. Namun, dalam praktiknya, komunikasi digital masih menghadapi berbagai permasalahan seperti multipath fading, ISI, dan ICI yang menurunkan kualitas penerimaan sinyal. Teknologi sistem komunikasi multi-carrier, khususnya OFDM, digunakan untuk mengatasi tantangan tersebut karena mampu meningkatkan efisiensi spektrum dan meminimalkan gangguan.

OFDM konvensional berbasis perangkat keras memiliki keterbatasan fleksibilitas dan biaya sehingga digunakan pendekatan SDR yang menawarkan solusi adaptif dengan konfigurasi parameter melalui perangkat lunak. Pada penelitian ini, sistem komunikasi multi-carrier dirancang menggunakan platform SDR open-source GNU Radio yang memungkinkan perancangan, simulasi, dan pengujian secara menyeluruh.

Penelitian ini bertujuan untuk merancang dan menganalisis sistem komunikasi multi-carrier OFDM. Metodologi yang digunakan mencakup perancangan sistem komunikasi berbasis perangkat lunak GNU Radio dengan memanfaatkan blok-blok pemrosesan sinyal. Analisis performa dilakukan melalui evaluasi hasil simulasi sistem ideal dan sistem dengan penambahan multipath fading, serta implementasi pada SDR.

Hasil simulasi menunjukkan bahwa permasalahan multipath fading dapat diatasi melalui proses decoding yang mencakup sinkronisasi data menggunakan metode Schmidl dan Cox. Metode ini memanfaatkan korelasi preamble simbol sebelum data payload dikirim. Proses pemulihan data dilakukan melalui tahapan equalizer setelah FFT dengan estimasi kanal padat yang diinterpolasi menggunakan metode cubic spline. Metode cubic spline digunakan untuk memodelkan respons kanal antar subcarrier secara lebih halus dan presisi. Equalizer MMSE diterapkan untuk meminimalkan galat antara simbol asli dan simbol terima dengan mempertimbangkan variansi derau. Proses kompensasi fase juga dilakukan menggunakan metode CPE untuk mengatasi rotasi fase yang sering terjadi.

Secara keseluruhan, sistem yang dirancang berhasil melakukan proses transmisi dan penerimaan data yang mampu mengatasi multipath fading dan memulihkan bit sehingga sesuai dengan bit yang dikirimkan.

The rapid development of technology has established digital communication systems as a fundamental pillar for high-speed data transmission with massive connectivity. However, the implementation of digital communication still faces various challenges, such as multipath fading, ISI, and ICI, which degrade signal reception quality. To address these issues, multi-carrier communication technologies, particularly OFDM, are employed due to their ability to improve spectral efficiency and minimize interference. Conventional hardware-based OFDM implementations have limitations in terms of flexibility and cost so SDR offers a more adaptive solution by enabling system parameter configuration through software. This thesis aims to design and analyze a multi-carrier OFDM-based communication system using GNU Radio as an open-source software platform. The research methodology includes designing the digital communication system with GNU Radio signal processing blocks, simulating ideal channels and channels with multipath fading, and implementing the system on an SDR platform. The simulation results show that the multipath fading issue can be mitigated through decoding processes involving data synchronization using the Schmidl and Cox method, which performs preamble symbol correlation prior to payload transmission. Data recovery is conducted through an equalization stage after the FFT process, with dense channel estimation interpolated using the cubic spline method to model the channel response across subcarriers more accurately. Furthermore, a MMSE equalizer is applied to minimize the error between transmitted and received symbols, while phase compensation is performed using the CPE method to correct phase rotation. Overall, the designed system successfully performs data transmission and reception processes capable of recovering bits to match the transmitted data, thus enhancing the reliability of digital communication under noisy or distorted channel conditions.

The rapid development of technology has established digital communication systems as a fundamental pillar for high-speed data transmission with massive connectivity. However, the implementation of digital communication still faces various challenges, such as multipath fading, ISI, and ICI, which degrade signal reception quality. To address these issues, multi-carrier communication technologies, particularly OFDM, are employed due to their ability to improve spectral efficiency and minimize interference.

Conventional hardware-based OFDM implementations have limitations in terms of flexibility and cost so SDR offers a more adaptive solution by enabling system parameter configuration through software. This thesis aims to design and analyze a multi-carrier OFDM-based communication system using GNU Radio as an open-source software platform. The research methodology includes designing the digital communication system with GNU Radio signal processing blocks, simulating ideal channels and channels with multipath fading, and implementing the system on an SDR platform.

The simulation results show that the multipath fading issue can be mitigated through decoding processes involving data synchronization using the Schmidl and Cox method, which performs preamble symbol correlation prior to payload transmission. Data recovery is conducted through an equalization stage after the FFT process, with dense channel estimation interpolated using the cubic spline method to model the channel response across subcarriers more accurately. Furthermore, a MMSE equalizer is applied to minimize the error between transmitted and received symbols, while phase compensation is performed using the CPE method to correct phase rotation.

Overall, the designed system successfully performs data transmission and reception processes capable of recovering bits to match the transmitted data, thus enhancing the reliability of digital communication under noisy or distorted channel conditions.

Kata Kunci : OFDM, GNU Radio, Software Defined Radio, sinkronisasi Schmidl-Cox, equalizer MMSE, multipath fading.