Abstract
α-OFDM, a generalization of theOFDMmodulation, is proposed. This newmodulation enhances the outage capacity performance of bursty communications. The α-OFDM scheme is easily implementable as it only requires an additional time symbol rotation after the IDFT stage and a subsequent phase rotation of the cyclic prefix. The physical effect of the induced rotation is to slide the DFT window over the frequency spectrum. When successively used with different angles α at the symbol rate, α-OFDM provides frequency diversity in block fading channels. Interestingly, simulation results show a substantial gain in terms of outage capacity and outage BER in comparison with classical OFDM modulation schemes. The framework is extended to multiantenna and multicellular OFDM-based standards. Practical simulations, in the context of 3GPP-LTE, called hereafter α-LTE, sustain our theoretical claims.
Highlights
With the recent growth of wireless communications and the increasing demand for high transmission rates, orthogonal frequency division multiplexing (OFDM) is being considered the desirable modulation scheme of most future wireless communication technologies
The rest of the paper unfolds as follows: in Section 2, we study the mathematical extension of circulant matrices, which is at the heart of the classical OFDM modulation and we introduce the novel α-OFDM scheme
We study the outage capacity and bit error rate (BER) gain assuming that we were allowed to slide the spectrum over those bands while still sending data on Nu consecutive subcarriers
Summary
With the recent growth of wireless communications and the increasing demand for high transmission rates, orthogonal frequency division multiplexing (OFDM) is being considered the desirable modulation scheme of most future wireless communication technologies. The main advantage in practice lies in the flat fading aspect of the channel that facilitates equalization at the receiver side This property originates from the cyclic prefix (CP) addition, prior to signal transmission, that allows to model the channel as a circulant matrix in the time-domain [4]. A desirable method to cope with the outage problem in OFDM is to provide diversity in the frequency domain; this is accomplished by the cyclic delay diversity method [8] by EURASIP Journal on Advances in Signal Processing introducing different symbol delays on an array of transmit antennas All those methods require additional antennas to provide channel diversity or are still difficult to implement in practice.
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