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A Review of OFDMA and Single-Carrier FDMA and Some Recent Results

Ciochina C., Sari H.

Advances in Electronics and Telecommunications

2010

Vol. 1, no. 1

35--40

The controversial debate on OFDM vs. singlecarrier (SC) transmission started back in the 1980s at the time of the European Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB) projects. The same debate took place in wireless communications a decade later, and OFDM transmission with TDMA was adopted in the IEEE 802.11a specifications for wireless local area networks (WiFi) and by the WiMAX Forum for fixed WiMAX systems. Later, orthogonal frequency-division multiple access (OFDMA) was adopted by the WiMAX Forum for mobile WiMAX systems and more recently by the 3GPP for the downlink of Long Term Evolution (LTE) systems. In contrast, single-carrier FDMA was adopted for the uplink of LTE. In this overview paper, we will review these historic developments and give some recent results on OFDMA and Single-Carrier FDMA.

Potentiometric determination of pKa values of 1,4,5,8-tetrahydroxy-9-oxo-10-pentyl- 9,10-dihydro-acridine-2,3,6,7-tetracarboxylic acid (TPAT) extracted from Laurus Nobilis

Ibaoglu K., Sari H., Tuzen M., Mendil D., Soylak M.

Chemia Analityczna

2004

Vol. 49, No. 5

635-642

The pKa values of 1,4,5,8-tetrahydroxy-9-oxo-10-pentyl-9,10-dihydro-acridine-2,3,6,7-tetracarboxylic acid (TPAT) extracted from Laurus nobilis were determined by Molspin potentiometric titration at 25°C in the presence of 0.1 mol dm-3 NaCl. The pKa values were calculated using SUPERQUAD computer program. Initially deprotonation occurs in carboxylic groups, then at the nitrogen atom of the alkyl group, and finally at the hydroxylic groups of TPAT. The following pKa values were computed: 2.65, 3.36, 4.08, 5.43, 6.84, 9.30, 10.42 and 10.53.

Wyznaczono wartości pKa kwasu 1,4,5,8-tetrahydroksy-9-okso-1O-pentylo-9,10-dihydro-akrydyno-2,3,6,7-tetrakarboksylowego (TPAT) wyekstrahowanego z Laurus nobilis. Wyznaczanie pK przeprowadzono metodą potencjometry c zn ego miareczkowania Molspin'a wtemp. 25°C w obecności 0,1 mol dm(-3) NaCl. Wartości pK. obliczono przy użyciu programu komputerowego SUPERQUAD. W pierwszym rzędzie dysocjacji kwasowej ulegają grupy karboksylowe, później grupa =NH+ i na końcu grupy hydroksylowe. Dla poszczególnych stopni dysocjacji kwasowej wyliczono następujące wartości pK (a): 2,65; 3,36; 4,08; 5,43; 6,84:9,30; 10,42 and 10,53.