On the Capacity of Interference Channel With Causal and Noncausal Generalized Feedback at the Cognitive Transmitter

Abstract

In this paper, taking into account the effect of link delays, we investigate the capacity region of the Cognitive Interference Channel (C-IFC), where cognition can be obtained from either causal or non-causal generalized feedback. For this purpose, we introduce the Causal Cognitive Interference Channel With Delay (CC-IFC-WD) in which the cognitive user's transmission can depend on L future received symbols as well as the past ones. We show that the CC-IFC-WD model is equivalent to a classical Causal C-IFC (CC-IFC) with link delays. Moreover, CC-IFC-WD extends both genie-aided and causal cognitive radio channels and bridges the gap between them. First, we derive an outer bound on the capacity region for the arbitrary value of L and specialize this general outer bound to the strong interference case. Then, under strong interference conditions, we tighten the outer bound. To derive the achievable rate regions, we concentrate on three special cases: 1) Classical CC-IFC (L = 0), 2) CC-IFC without delay (L = 1), and 3) CC-IFC with unlimited look-ahead in which the cognitive user non-causally knows its entire received sequence. In each case, we obtain a new inner bound on the capacity region. The derived achievable rate regions under special conditions reduce to several previously known results. Moreover, we show that the coding strategy which we use to derive an achievable rate region for the classical CC-IFC achieves the capacity for the classes of degraded and semi-deterministic classical CC-IFC under strong interference conditions. Furthermore, we extend our achievable rate regions to the Gaussian case. Providing some numerical examples for Gaussian CC-IFC-WD, we compare the performances of the different strategies and investigate the rate gain of the cognitive link for different delay values. We show that one can achieve larger rate regions in the "without delay" and "unlimited lookahead" cases than in the classical CC-IFC; this improvement is likely due to the fact that, in the former two cases, the cognitive user can cooperate more effectively with the primary user by knowing the current and future received symbols.Index Terms-Causal cognitive radio, Gel'fand-Pinsker coding, generalized block Markov coding, interference channel, instantaneous relaying, non-causal decode-and-forward. and has published more than 230 technical papers in communication and information theory and cryptography in international journals and conferences proceedings. His current research interests include areas of communication theory, information theory and cryptography with special emphasis on network information theory and security for multiuser wireless communications. At the same time, during his academic activities, he has been involved in different political positions. First Vice President of I. R. Iran, Vice President of I. R. Iran and Head of Management and Planning Organization, Minister of ICT of I. R. Iran and Chancellor of University of Tehran, are the most recent ones.

New outer bounds for the interference channel with unilateral source cooperation

“…However, these bounds involve several auxiliary random variables and it is thus not clear how to evaluate them for the Gaussian noise channel. The authors of [6] also proposed an achievable scheme, whose rate region, as pointed out in [6,Rem. 2,point 6], is no smaller than that in [4, Sec.…”

“…V] specialized to unilateral source cooperation. However, in [6], no performance guarantees in terms of constant gap were given. In [7], the capacity of the IC with unilateral source cooperation was characterized to within 2 bits (per user) for a large set of channel parameters that, roughly speaking, excludes the case of weak interference at both receivers.…”

The Two-User Causal Cognitive Interference Channel: Novel Outer Bounds and Constant Gap Result for the Symmetric Gaussian Noise Channel in Weak Interference

“…Although, to the best of our knowledge, the work in [16] gives the best known bounds for this channel, their evaluation is not straightforward. For example, the outer bound involves several auxiliary random variables that are jointly distributed with the inputs and for which no cardinality bounds on the corresponding alphabets are known; the inner bound is characterized by many constraints and auxiliary random variables whose optimization is not immediate.…”

Approximate sum-capacity of full- and half-duplex asymmetric interference channels with unilateral source cooperation

“…Cognitive channels were also studied in [14]; here the authors analyzed the causal cognitive IC with delay. The zerodelay case coincides with the causal cognitive model studied in this work; the main contribution is a capacity characterization for the degraded semi-deterministic channel in the strong interference regime.…”