A promising new wideband multiple-access scheme for future mobile communications systems

Recently, "Interleaved Frequency-Division Multiple-Access" (IFDMA) has been introduced as a new spread-spectrum multiple-access scheme far mobile comm unications which is suitable for both downlink and uplink applications. IFD MA combines spread-spectrum multicarrier transmission with frequency-divisi on multiple-access and, therefore, is capable of achieving frequency divers ity while multiple-access interference is avoided. Moreover, compared to ot her wideband multiple-access schemes IFDMA shows several additional advanta ges. The cost to achieve these advantages is to allow for intersymbol inter ference. However, the effects of intersymbol interference can be reduced si gnificantly by applying an equalizer at the IFDMA receiver. In this paper, the principle of IFDMA is reviewed and it is shown that IFDM A is a promising new wideband multiple-access scheme suitable for future mo bile communications systems. The frequency diversity achievable with IFDMA is determined as well as performance results for uncoded and coded transmis sion taking into account different equalization techniques. As a result, un coded IFDMA applying optimum equalization performs even better than uncoded multicarrier code-division multiple-access applying maximum-likelihood mul ti-user detection. In the case of coded IFDMA transmission coding gains up to 6.8 dB at a bit-error-rate of 10(-4) are achieved using a standard convo lutional code. An additional performance gain of up to 2.2 dB is possible i f equalization and decoding are considered jointly.