Pengembangan Protocol Selective Retransmission Untuk Komunikasi Paket Pada Kanal Akustik Bawah Air

Satriagung, Muhammad Erlangga (2026) Pengembangan Protocol Selective Retransmission Untuk Komunikasi Paket Pada Kanal Akustik Bawah Air. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Komunikasi akustik bawah air menghadapi tantangan berupa bandwidth terbatas, bit error tinggi, dan delay propagasi besar, sehingga protokol retransmisi konvensional seperti Go Back N menjadi kurang efisien. Penelitian ini merancang dan menguji protokol Selective Repeat Automatic Repeat reQuest (SR ARQ) berbasis kontrol akses time-slotted pada modem akustik OFDM dengan 128 subcarrier, modulasi BPSK, dan deteksi error CRC 16. Protokol dirancang untuk mendukung komunikasi broadcast multiuser dan divalidasi pada tautan point to point. Validasi dilakukan melalui simulasi link level, pengujian udara secara real-time menggunakan dua Raspberry Pi, serta pengujian bawah air di kolam uji. Namun, pada pengujian bawah air terdapat kendala noise power amplifier sehingga pengujian menggunakan laptop dengan post-processing offline. Hasil simulasi menunjukkan modem dan protokol berfungsi sesuai rancangan, dengan BER mendekati nol dan rasio pengiriman frame mencapai 100% pada rentang SNR kerja. Pengujian udara berhasil mengirimkan pesan secara utuh hingga jarak 2 m. Pada pengujian bawah air, sinkronisasi frame bekerja baik dengan deteksi preamble 100% hingga jarak 50 m dan SNR in-band 27–33 dB. Namun, decode payload offline belum lolos CRC akibat indikasi kehilangan sampel pada pipeline pemutaran berkas. Penelitian ini memvalidasi rancangan modem dan protokol serta merekomendasikan pipeline real-time dan penambahan FEC.
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Underwater acoustic communication faces challenges such as limited bandwidth, high bit error rate, and large propagation delay, making conventional retransmission protocols such as Go Back N less efficient. This study designs and evaluates a Selective Repeat Automatic Repeat reQuest (SR ARQ) protocol based on time-slotted medium access control over an OFDM acoustic modem with 128 subcarriers, BPSK modulation, and CRC 16 error detection. The protocol is designed to support multiuser broadcast communication and is validated over a point-to-point link. The validation is conducted through link-level simulation, real-time in-air testing using two Raspberry Pi devices, and underwater testing in a test tank. The simulation results show that the modem and protocol operate as designed, with the BER approaching zero and the frame delivery ratio reaching 100% within the working SNR range. The real-time in-air test successfully delivered the complete message at distances of up to 2 m. In the underwater test, frame synchronization performed well, with 100% preamble detection up to 50 m and an in-band SNR of 27–33 dB. However, payload decoding during offline post-processing did not pass CRC, which is indicated to be caused by sample loss in the file playback pipeline. This study validates the modem and protocol design and recommends a real-time processing pipeline and the addition of FEC for future development.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	CRC 16, Komunikasi Akustik Bawah Air, OFDM, Selective Repeat ARQ, Slot MAC. CRC 16, OFDM, Selective Repeat ARQ, Slot MAC, Underwater Acoustic Communication.
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK5101 Telecommunication
Divisions:	Faculty of Intelligent Electrical and Informatics Technology (ELECTICS) > Telecommunication Engineering > 20202-(S1) Undergraduate Thesis
Depositing User:	Muhammad Erlangga Satriagung
Date Deposited:	24 Jul 2026 06:53
Last Modified:	24 Jul 2026 06:53
URI:	http://repository.its.ac.id/id/eprint/136951

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