We develop a theoretical framework for achieving the maximum possible speed on constrained digital channels with a finite alphabet. A common inaccuracy that is made when computing the capacity of digital channels is to assume that the inputs and outputs of the channel are analog Gaussian random variables, and then based upon that assumption, invoke the Shannon capacity bound for an additive whi...

In the absence of accurate channel probability distribution information or in broadcast scenarios, code design for consistent channel-by-channel performance, rather than average performance, may be desirable. Root and Varaiya’s compound channel theorem promises the existence of universal codes that operate with a consistent proximity to channel mutual information on any instance of the compound...

We consider the problem of transmitting a Gaussian source on a slowly fading Gaussian channel, subject to the mean squared error distortion measure. The channel state information is known only at the receiver but not the transmitter. The source is assumed to be encoded in a successive refinement manner, and then transmitted over the channel using the broadcast strategy. In order to minimize the...

We demonstrate that the sum-rate capacity of a memoryless Gaussian network at high signal-to-signal ratio (SNR) can be asymptotically doubled when feedback is available. To demonstrate this phenomenon we study two networks: the one-to-two scalar Gaussian broadcast channel (BC) and the twoto-two scalar Gaussian interference channel (IC). For the broadcast channel we show that if the noise sequen...

We consider the problem of transmitting a Gaussian source on a slowly fading Gaussian channel, subject to the mean squared error distortion measure. The channel state information is known only at the receiver but not the transmitter. The source is assumed to be encoded in a successive refinement manner, and then transmitted over the channel using the broadcast strategy. In order to minimize the...

We consider a model nondispersive nonlinear optical fiber channel with additive white Gaussian noise at large SNR (signalto-noise ratio) in the intermediate power region. Using Feynman path-integral technique we for the first time find the optimal input signal distribution maximizing the channel’s per-sample mutual information. The finding of the optimal input signal distribution allows us to i...

In this paper, we revisit the problem of finding the average capacity of the Gaussian feedback channel. First, we consider the problem of finding the average capacity of the analog colored Gaussian noise channel where the noise has an arbitrary spectral density. We introduce a new approach to the problem where we solve the problem over a finite number of transmissions and then consider the limi...

We explore the capacity and generalized degrees of freedom of the two-user Gaussian X channel, i.e. a generalization of the 2 user interference channel where there is an independent message from each transmitter to each receiver. There are three main results in this paper. First, we characterize the sum capacity of the deterministic X channel model under a symmetric setting. Second, we characte...

Polar lattices, which are constructed from polar codes, are provably good for the additive white Gaussian noise (AWGN) channel. In this work, we propose a new polar lattice construction that achieves the secrecy capacity under the strong secrecy criterion over the mod-Λ Gaussian wiretap channel. This construction leads to an AWGN-good lattice and a secrecy-good lattice simultaneously. The desig...

This paper studies signal detection in multiuser systems where the uncertainty is due to fading as well as a strong co-channel interference of the same form as that of the desired signal. In particular, unlike for the desired signal, no pilot for the interference signal is available for measuring its fading channel state. Still, the interference is a non-Gaussian process and treating it as Gaus...