Real-time lut-less magnitude modulation for peak power control of single carrier RRC filtered signals

In this paper a novel multistage polyphase magnitude modulation (MPMM) scheme is proposed for efficiently controlling the envelope´s peak power of single carrier band limited signals, using root-raised cosine (RRC) pulse shaping. A new LUT-less approach of the concept of magnitude modulation (MM) is developed. As opposed to traditional MM solutions, based on look-up-tables (LUT), in the present proposal, the multiplier coefficients that magnitude modulate the data stream prior to RRC filtering are computed in real time by a low-complexity polyphase filter system. In addition, the proposed technique is independent of the modulation being used, making it possible to extend the MM concept to higher order and/or non-constant amplitude constellations. Also, any number of base-system blocks can be added in a serial cascade, allowing to almost eliminate the back-off, even at very low filter roll-off values. Increased sensitivity to noise due to MM is compensated by using error control coding. Experimental results show an overall back-off gain (back-off gain minus BER loss) greater than 4.5 dB and 3.6 dB for 8-PSK and 16-QAM respectively, considering 0.2 roll-off RRC filtering.