Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks[omnet++code]

Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks

Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks THE performance of a wireless multipoint communication network has been limited by its inherent interference. Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks[omnet++code]To cope with the interference in cellular networks, interference mitigation techniques including interference cancellation at the receiver/transmitter as well as coordination schemes among multiple cells have been considered so far. On the other hand, there have also been a few attempts to investigate the stochastic characteristics of the interference in wireless Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks communication networks.

In it was shown that the distribution of the inter-cell interference (ICI) in a downlink cellular orthogonal frequency-division multiple-access (OFDMA) network with quadrature amplitude modulation (QAM) is close to a Gaussian distribution when all available subcarriers in each cell are fully loaded. Moreover, the recent work in proves that the worst-case additive noise in wireless networks with respect to the channel capacity has a Gaussian distribution. These observations motivate one to expect that the transmission rate in interference-dominated environments may substantially increase when a proper modulation scheme is Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks employed instead of QAM so that the resultant ICI has a non-Gaussian distribution. Recently, it was shown in that the distribution of the multiple-access interference similar to the ICI deviates far from the Gaussian distribution when frequency-shift keying (FSK) modulation is used in wireless multiple-access networks.

Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks

Unfortunately, FSK modulation suffers from low bandwidth efficiency although it provides high power efficiency In order to achieve high bandwidth efficiency as well as to make the ICI non-Gaussian, it is natural to consider a modulation scheme combining QAM with FSK, called frequency and quadrature-amplitude modulation (FQAM). Only a few of researches have focused on the error performance of uncoded or trellis-coded modulation systems with FQAM or its variants over additive white Gaussian noise (AWGN) and fading channelsHowever, to the best of our knowledge, FQAM has never been taken into Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks consideration from the viewpoint of increasing the channel capacity in interferencedominated environments.

In this paper, we propose a downlink cellular OFDMA network employing FQAM rather than conventional QAM, especially for cell-edge users, which effectively makes the ICI non-Gaussian. We first derive optimal maximum-likelihood (ML) metrics for soft- Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks decision decoding of the binary or non-binary error-correcting codes (ECCs) employed in the proposed FQAM-based OFDMA network. Since they require information on the pathloss effects and the modulated symbols of the interfering users, which are practically unavailable at the Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks receiver, we also propose their practical sub-optimal versions exploiting the non-Gaussian property of the ICI. Numerical results demonstrate that the distribution of the ICI in the proposed network deviates far from the Gaussian distribution