We provide a counterexample to Cover’s conjecture that the feedback capacity CFB of an additive Gaussian noise channel under power constraint P be no greater than the nonfeedback capacity C of the same channel under power constraint 2P , i.e., CFB(P ) C(2P ). Index Terms|Additive Gaussian noise channels, channel capacity, conjecture, counterexample, feedback.

Feedback in a communication system enables the transmitter to employ channel adaptive signaling and avoid interference which leads to improvements in all performance metrics. In the case of a multiple-input multiple-output (MIMO) channel, research has repeatedly shown that by sending small number of information bits as feedback about the channel conditions to the transmitter, optimal channel ad...

In this paper, we propose a novel adaptive modulation and coding (AMC) algorithm dedicated to reduce the feedback frequency of the channel state information (CSI). There have been already plenty of works on AMC so as to exploit the bandwidth more efficiently with the CSI feedback to the transmitter. However, in some occasions, frequent CSI feedback is not favorable in these systems. This work c...

We study the optimization of the number of bits allocated by energy harvesting users for sending feedback to a common multiple-antenna access point (AP). The nodes need to distribute their feedback transmissions judiciously across time (and channel states) in order to maximize certain throughput goals. While the MISO channel capacity from the AP to a user is a strictly increasing function of th...

The utility of limited feedback for coding over an individual sequence of DMCs is investigated. This study complements recent results showing how limited or noisy feedback can boost the reliability of communication. A strategy with fixed input distribution P is given that asymptotically achieves rates arbitrarily close to the mutual information induced by P and the state-averaged channel. When ...

We study two problems in the theory of identi cation via channels. The rst problem concerns the identi cation via channels with noisy feedback. Whereas for Shannon's transmission problem the capacity of a discrete memoryless channel does not change with feedback, we know from [3] and [4] that the identi cation capacity is a ected by feedback. We study its dependence on the feedback channel. We ...

In this paper, we consider some long-standing problems in communication systems with access to noisy feedback. We introduce a new notion, the residual directed information, to capture the effective information flow (i.e. mutual information between the message and the channel outputs) in the forward channel. In light of this new concept, we investigate discrete memoryless channels (DMC) with noi...

Various scenarios are considered where some information is more important than other and needs better protection. A general theoretical framework for unequal error protection is developed in terms of exponential error bounds. It provides some fundamental limits and optimal strategies for such problems. New class of message-wise unequal error protection problems are also introduced. Even for dat...

It is known that perfect noiseless feedback can be used to improve the reliability of communication systems. We show how to make those gains robust to noise on the feedback link. We focus on feedback links that are themselves discrete memoryless channels. We demonstrate that Forney’s erasure-decoding exponent is achievable given any positive-capacity feedback channel. We also demonstrate that a...

this study seeks to examine how a company can select the best intermediary for its marketing channels with minimum of criteria and time. a theoretical framework is proposed based on the most important tasks of intermediary and the criteria to measure them. there are four basic tasks and thirty criteria in three independent levels. subsequently, an exploratory case study in iranian food industry...