IMPLEMENTASI MODEL KANAL LINTASAN JAMAK PADA SIMULATOR BIDANG DASAR OFDM

LUTHFI NURMAWAN, Ir. Budi Setiyanto, MT.

2013 | Skripsi | TEKNIK ELEKTRO

Orthogonal Frequency Division Multiplexing (OFDM) merupakan skema transmisi data paralel yang efisien. Pesat data tinggi dicapai dengan cara mengirimkan sejumlah sub pembawa yang saling ortogonal. Penelitian ini bertujuan untuk mengimplementasikan model simulator bidang dasar OFDM.Model diimplementasikan pada tiga komputer dengan antarmuka soundcard.Komputer pertama dimodelkan sebagai pengirim, komputer kedua dimodelkan sebagai kanal, dan komputer ketiga dimodelkan sebagai penerima. Model menggunakan pemeta 16-QAM, 32 titik IFFT/FFT, 32 subpembawa (24 subpembawa data, empat subpembawa pilot, dan empat subpembawa nol), dan awalan siklis (Cyclic Prefix, CP) sepanjang ¼ simbol. Lintasan jamak menggunakan standar 3rd Generation Partnership Project (3GPP) dengan model kanal PA, PB, dan VA. Sebelum masuk soundcard, isyarat diskret digandakan menjadi lima repetisi berurutan. Pendeteksian simbol di penerima dilakukan dengan metode korelasi.Estimasi kanal menggunakan metode kuadrat terkecil (Least Square, LS). Penelitian ini menganalisis pengaruh lintasan jamak terhadap pemulihan bit dan peran keberadaan LS. Hasil pengujian menunjukkan bahwa model kanal tanpa menggunakan estimasi kanal memberikan BER senilai 0,7604 dan MSE senilai 0,0837 pada model kanal tanpa lintasan jamak. Pada Pejalan A (PA), Pejalan B (PB), dan Kendaraan A (VA) masing-masing memberikan BER senilai 0,7604; 0,6354; dan 0,6563, dan MSE senilai 0,0757; 0,0529; dan 0,0560. Dengan menggunakan estimasi kanal LS, pada model kanal tanpa lintasan jamak, PA, PB, dan VA masing-masing BER turun menjadi 0; 0; 0,1458; dan 0,0729, dan MSE turun menjadi 4,67E-05; 5,92E-05; 0,0219; dan 0,0028.

Orthogonal Frequency Division Multiplexing (OFDM) is an efficient parallel data transmission scheme. High bit rate can be achieved by sending orthogonal subcarriers. The purpose of this research is to implement an OFDM baseband simulator model. This research is conducted with three computers and soundcard as its interface. The first computer acts as the transmitter, the second computer acts as channel model, and the third computer acts as receiver. This model is carried out with a 16-QAM mapper, 32-point IFFT/FFT, 32 subcarriers (24 data subcarriers, four pilot subcarriers, and four zero subcarriers), and Cyclic Prefix (CP) with ¼ of OFDM symbol length. The 3rd Generation Partnership Project (3GPP) is used as the standard of multipath with channel model of PA, PB, and VA. To ensure the capability of soundcard sending the signal is good, sample is quintupled to have five repetitions in a series. Symbol detection at the receiver is conducted offline by correlation method. Least Square (LS) algorithm is used for channel estimation. This research analyzes the effect of multipath to the recovered bit and the effect of using LS as channel estimation method. The numerical results are as follows. Without channel estimation, the BERs and MSEs for no multipath are 0.7604 and 0.0837, respectively. The BERs for Pedestrian A (PA), Pedestrian B (PB), and Vehicular A (VA) models are 0.7604, 0.6354, and 0.6563, respectively. The MSEs for PA, PB, and VA models are 0.0757, 0.0529, and 0.0560, respectively. By applying LS channel estimation, the BERs for no multipath, PA, PB, and VA models decreased to 0, 0, 0.1458, and 0.0729, and MSEs decreased to 4.67E-05, 5.92E-05, 0.0219, and 0.0028, respectively.

Kata Kunci : Model kanal, lintasan jamak, BER, MSE, LS.