Optimization of Information Rate Upper and Lower Bounds for Channels with Memory

—We consider the problem of minimizing upper bounds and maximizing lower bounds on information rates of stationary and ergodic discrete-time channels with memory. The channels we consider can have a finite number of states, such as partial response channels, or they can have an infinite state space, such as timevarying fading channels. We optimize recently proposed information rate bounds for such channels, which make use of auxiliary finite-state machine channels (FSMCs). Our main contribution in this paper is to provide iterative expectation–maximization (EM) type algorithms to optimize the parameters of the auxiliary FSMC to tighten these bounds. We provide an explicit, iterative algorithm that improves the upper bound at each iteration. We also provide an effective method for iteratively optimizing the lower bound. To demonstrate the effectiveness of our algorithms, we provide several examples of partial response and fading channels where the proposed optimization techniques...

• Type: Journal
• Year: 2007
• Where: CORR
• Authors: Parastoo Sadeghi, Pascal O. Vontobel, Ramtin Shams
• Keywords: Algorithms, CORR 2007, Education, Information Rate, Lower Bound