Channel estimation with hard limiter receiver as key technology for low cost wireless systems

Future wireless indoor network applications require technologies that allow high data rate transmission in multipath propagation environment. The acceptance of new technologies will depend essentially on the expense of its realization. A key technology for link level cost reduction is the use of hard (amplitude) limiting receiver structures that substantially save the costs for the analogue domain of the receivers [J.P. Fonseka, 1996][A. Wittneben and U. Dettmar, 1997]. Technologies suited for multipath propagation, such as ML based detection or smart antennas training, require the knowledge of the complex channel impulse response (CIR) [J.G. Proakis, 1995][M. Kuhn, 2002]. A method on how to estimate the complex CIR in case of a hard limited receiver structure is needed. In this paper, an estimation method is presented that allows an estimation of the complex CIR on basis of phase samples. The new estimation technique is a two level approach, which exploits the finite-state nature of the transmission system. With the help of an appropriate training sequence an estimate of the desired phase and amplitude is performed. The second level procedure performs a subspace approach to estimate the CIR, which yields a well treatable overdetermined linear equation system. Simulation results for a GMSK transmission system highlight the suitability of this estimation method.