Analisis Implementasi Channel Coding pada OFDM untuk Mitigasi Efek Doppler di Lingkungan VANET
Abstract
Efek Doppler dapat menyebabkan time dan frekuensi selektif fading pada lingkungan VANET. Kondisi itu terjadi karena pergerakan kanal yang mudah berubah-ubah sehingga menyebabkan time-varying channel dan Doppler Spread menjadi lebih besar daripada periode simbol. Akibatnya, dapat merusak orthogonalitas antar subcarrier pada sistem OFDM yang menimbulkan ICI (Inter-Carrier-Interference) dan menurunkan BER (bit error ratio). Pada penelitian ini mengusulkan skema modulasi adaptif dengan channel coding berdasarkan perubahan gain kanal sesaat yang terkena fading pada setiap subcarriernya. Hal itu bertujuan untuk untuk meningkatkan nilai BER dan kapasistas kanal dalam sistem. Simulasi yang dilakukan dengan menguji modulasi addaptif pada tiga threshold dengan variasi frekuensi Doppler. Level threshold yang digunakan adalah 0.2 dan 0.4, 0.3 dan 0.5, serta 0.5 dan 0.7. Hasil simulasi menunjukkan bahwa modulassi adaptif dengan channel coding memiliki nilai SNR terendah dibandingkan dengan modulasi non-adaptif BPSK, QPSK, dan 16-QAM) yaitu membutuhkan SNR sebesar 16dB untuk mencapai BER 10-3. Sementara hasil uji threshold pada modulasi adaptif menunjukkan bahwa penetapan threshold 0.2 dan 0.4 menghasilkan kinerja BER yang optimal karena memiliki nilai SNR terendah dibandingkan dengan dua threshold yang lainnya dan mengalami peningkatan kapasitas terbesar yaitu 127% dibandingkan dengan modulasi non-adaptif (BPSK) pada frekuensi Doppler normalisasi, đť‘“đť‘‘ = 0.000128.
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DOI: http://dx.doi.org/10.32497/jtet.v10i1.2546
DOI (PDF): http://dx.doi.org/10.32497/jtet.v10i1.2546.g107310
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