A Promising New Wideband Multiple‐Access Scheme for Future Mobile Communications Systems
Michael Schnell, Isabella De Broeck, Uli Sorger · European Transactions on Telecommunications · 1999
Abstract Recently, “Interleaved Frequency‐Division Multiple‐Access” (IFDMA) has been introduced as a new spread‐spectrum multiple‐access scheme for mobile communications which is suitable for both downlink and uplink applications. IFDMA combines spread‐spectrum multicarrier transmission with frequency‐division multiple‐access and, therefore, is capable of achieving frequency diversity while multiple‐access interference is avoided. Moreover, compared to other wideband multiple‐access schemes IFDMA shows several additional advantages. The cost to achieve these advantages is to allow for intersymbol interference. However, the effects of intersymbol interference can be reduced significantly by applying an equalizer at the IFDMA receiver. In this paper, the principle of IFDMA is reviewed and it is shown that IFDMA is a promising new wideband multiple‐access scheme suitable for future mobile communications systems. The frequency diversity achievable with IFDMA is determined as well as performance results for uncoded and coded transmission taking into account different equalization techniques. As a result, uncoded IFDMA applying optimum equalization performs even better than uncoded multicarrier code‐division multiple‐access applying maximum‐likelihood multi‐user detection. In the case of coded IFDMA transmission coding gains up to 6.8 dB at a bit‐error‐rate of 10−‐4are achieved using a standard convolutional code. An additional performance gain of up to 2.2 dB is possible if equalization and decoding are considered jointly.