A Low Complexity Zero Threshold Detector for Bandwidth Efficient Hierarchical Modulated System

Abstract

In Digital video broadcasting (DVB), the global content and local content is transmitted using hierarchical modulated OFDM. However, conventional OFDM transmitter which is implemented using IFFT requires an addition of cyclic prefix to combat for intersymbol interference which in turn reduces the spectral efficiency. To overcome this shortcoming, in this paper, a wavelet based hierarchical modulated OFDM system is proposed for DVB and is well suited for transmitting both the global content and local content in single frequency network. Wavelet based system is bandwidth efficient and it avoids the insertion of cyclic prefix along with active OFDM symbol with same complexity in design as FFT based OFDM system. At the receiver, a conventional hierarchical modulated system requires separate decision rules for global and local content. The global content requires four decision rule but in case of local content, the decision rule used for detection increases as the order of the system increases. In this paper, a new detector is proposed which requires only a set of four zero threshold decision rules for both the global and local contents which reduces the complexity of the system tremendously.