Wireless Pers Commun (2008) 45:1–10 DOI 10.1007/s11277-007-9368-y Estimation of Channel Impulse Response Using Modiﬁed Ceiling Bounce Model in Non-Directed Indoor Optical Wireless Systems K. Smitha · Arumugam Sivabalan · Joseph John Published online: 13 October 2007 © Springer Science+Business Media, LLC. 2007 Abstract In this paper a modiﬁcation to the traditional Ceiling bounce model is proposed for use with non-directed indoor optical wireless systems which takes into account the trans- ceiver separation distances as well as their actual positions while computing the impulse response. This modiﬁcation is done by combining the results of DC gain computation and the statistical model along with the traditional Ceiling bounce approach. We show that the results of the proposed modiﬁcation agree better than the traditional Ceiling bounce model with the reported experimental results of Barry et al. (1993. IEEE Journal on Selected Areas in Communications, 11, 367–379). The modiﬁed Ceiling bounce model is used to study the effect of transceiver positions on the rms delay spread and channel impulse response. Keywords Modiﬁed Ceiling bounce model · Indoor channel impulse response · Diffuse indoor optical systems 1 Introduction The rapid growth in personal wireless communications, mobile computing, and multimedia terminals fuelled the demand for more capacity in wireless systems. This demand is the main driving force behind the development of wireless systems operating in infrared frequencies [1, 5, 6]. Non-directed, non-LOS systems, popularly known as diffuse systems may be con- sidered the most ﬂexible conﬁguration in that, they are robust to shadowing and blockage and do not require any alignment [7–10]. This type of topology overcomes the blocking problem by relying on the high reﬂectivity of common building materials, so that a significant fraction K. Smitha · A. Sivabalan (B ) · J. John Department of Electrical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India e-mail: sbalan@iitk.ac.in K. Smitha e-mail: mithusekhar81@yahoo.com J. John e-mail: jjohn@iitk.ac.in 123