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Performance Evaluation of WiMAX/IEEE 802.16 OFDM Physical Layer - page 37 / 107

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Low receiver complexity as the transmitter combat the channel effect to some extends. Suitable for high­data­rate transmission High flexibility in terms of link adaptation Low complexity multiple access schemes such as orthogonal frequency­division multiple access (OFDMA) It is possible to use maximum likelihood detection with reasonable complexity[25]

On the other side, few drawbacks of OFDM are listed as follows An OFDM system is highly sensitive to timing and frequency offsets Demodulation of an OFDM signal with an offset in the frequency can lead to a high bit error rate.

[24].

An OFDM system with large number of subcarriers will have a higer peak to average power ratio (PAPR) compared to single carrier system. High PAPR of a system makes the implementation of Digital to ana(DgAC) and Analog to Digital Conversion (ADC) extremely dif icult [23].

3.3.6 APPLICATION

OFDM has gained a big interest since the beginning of the 1990s [26] as many of the implementation dif iculties have been overcome. OFDM has been in used or proposed for a number of wired and wireless applications. Digital Audio Broadcasting (DAB) was the first commercial use of OFDM technology [23]. OFDM has also been used for the Digital Video Broadcasting [27]. OFDM under the acronym of Discrete Multi Tone (DMT) has been selected for asymmetric digital subscriber line (ADSL) [32]. The specification for Wireless LAN standard such as IEEE 802.11a/g [29, 30] and ETSI HIPERLAN2 [31] has employed OFDM as their PHY technologies. IEEE 806.16 standard for Fixed/Mobile BWA has also accepted OFDM for PHY technologies.

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