Adaptive modulation techniques for duplex OFDM transmission

The design tradeoffs of turbo-coded burst-by-burst adaptive orthogonal freq uency division multiplex (OFDM) wideband transceivers are analyzed. We demo nstrate that upon aiming for a higher throughput a higher proportion of low -quality OFDM subcarriers has to be used for the transmission of inherently vulnerable high-order modem modes, transmitting several bits per subcarrie r, Upon invoking turbo coding and adjusting the modem mode switching regime near-error-free performance can be achieved at the cost of a reduced throu ghput. Various blind modem mode detection techniques have also been investi gated and the most complex channel coding trellis-based detection algorithm was found to be the most powerful. Last, the design tradeoffs of spectral pre-equalization have been explored and qualtified, We concluded that AOFDM provides a convenient framework for adjusting the required target integrit y and throughput both with and without turbo channel coding.