Interference cancellation for OFDM systems with hierarchical modulation over non-linear satellite channels

This paper presents an efficient technique to eliminate the inter-layer interference (ILI) inherent in hierarchical modulation (HM) schemes operating over nonlinear satellite channels. The HM considered in this work is used in conjunction with an orthogonal frequency division multiplexing (OFDM) system. The proposed technique is based on an enhanced version of the selective mapping (SLM) scheme used for peak-to-average power ratio (PAPR) reduction. The enhanced SLM is constructed by using a new metric, which is more informative than the conventional PAPR metric. Simulation results confirmed that a noticeable bit error rate (BER) and interference reductions can be achieved by using the proposed technique.

1. INTRODUCTION

In the digital video broadcasting-satellite services to hand-held (DVB-SH) standard, hierarchical modulation (HM) is selected as an alternative to conventional modulation schemes such as quadrature phase shift keying (QPSK) and quadrature amplitude modulation (16-QAM) [1]. HM is one of the promising technologies to upgrade existing systems with backward compatibility, i.e., receivers that have been designed to use conventional modulation schemes will remain functional by detecting the data in the high priority constellation points [2]–[4]. Furthermore, the additional complexity and cost for HM-based systems are relatively low [5], [6]. However, HM usually suffers from the interference between the enhancement-layer (EL) and basic-layer (BL) streams, which is denoted as inter-layer interference (ILI) [7], [8].