Throughput performance enhancement for multiuser diversity OFDMA using MMSE equalization without guard interval

In recent year, to achieve a high data rate and high quality multimedia service in wireless communication systems, orthogonal frequency division multiplexing (OFDM) is attractive and widely studied. Moreover, orthogonal frequency division multiple access (OFDMA) which is combined OFDM and frequency division multiple access (FDMA) provides each user with a fraction of the available number of subcarriers. The diversity that exists between users is called multiuser diversity and can be exploited by the sender to enhance the capacity of wireless network. In a multiuser diversity OFDMA, exploiting channel fluctuation diversity is in essence done by selecting the user with the strong subcarrier channels. Therefore, the multiuser diversity techniques promise dramatically increased system throughput and spectral efficiency. In multipath fading environment, severe fading of the signal amplitude and intersymbol interference (ISI) due to the frequency selectivity of the channel cause an unacceptable degradation of error performance. In an OFDM system, ISI is eliminated by inserting guard interval (GI) longer than the delay spread of the channel. On the other hand, this operation is degraded the throughput performance. In this paper, we propose to improve the throughput performance for multiuser diversity OFDMA without GI. Previously, we have proposed ISI and inter-carrier interference (ICI) compensation method. In addition, the minimum mean square error (MMSE) equalization can suppress the noise enhancement due to ISI and ICI. Therefore, we employ these methods to eliminate ISI and ICI and try to improve the throughput performance.