Comparative study of pilot symbol assisted modem schemes

The performance of a range of 1, 2 and 4 bit/symbol pilot symbol assisted modulation (PSAM) arrangements employing first-order linear, low pass, polynomial and optimum higher-order linear interpolation schemes is analysed in contrast to that of the equivalent non-coherent modems. Both the non-coherent modems as well as the coherent PSAM schemes exhibited a residual bit error rate (BER), but the best compromise in terms of performance, system delay and complexity was attributable to the first-order linear interpolator. In case of short interpolation buffers the polynomial interpolator slightly outperformed the low-pass and the higher-order linear optimum interpolators, but this advantage eroded in the case of longer buffers. The higher complexity of the minimum mean squared error interpolator is not justifiable in terms of performance improvements. The low-complexity linearly interpolated PSAM schemes have an improved performance in comparison to the differential schemes in the case of higher order constellations, such as 4- and 16-level quadrature amplitude modulation (QAM)