The Wiretapped Diamond-Relay Channel

Abstract

In this paper, we study a diamond-relay channel where the source is connected to M relays through orthogonal links and the relays transmit to the destination over a wireless multiple-access channel in the presence of an eavesdropper. The eavesdropper not only observes the relay transmissions through another multiple-access channel, but also observes a certain number of source-relay links. The legitimate terminals know neither the eavesdropper's channel state information nor the location of source-relay links revealed to the eavesdropper except the total number of such links.For this wiretapped diamond-relay channel, we establish the optimal secure degrees of freedom. In the achievability part, our proposed scheme uses the source-relay links to transmit a judiciously constructed combination of message symbols, artificial noise symbols as well as fictitious message symbols associated with secure network coding. The relays use a combination of beamforming and interference alignment in their transmission scheme. For the converse part, we take a genie-aided approach assuming that the location of wiretapped links is known. I. INTRODUCTIONCloud Radio-Access Network (C-RAN) is a promising architecture to meet the demand for higher data rates in next generation wireless networks. In these systems, the base-stations act as relays and are connected via high-speed backhaul links to a cloud network. Encoding and decoding operations happen centrally in the cloud. The study of fundamental information theoretic limits and optimal coding techniques for such systems is a fertile area of research.Motivated by C-RAN, we study a model where the source is connected to M relay terminals using orthogonal links with a fixed capacity. The relays transmit to the destination over a wireless multipleaccess channel. Such a setup is known as the diamond-relay network [1]- [5]. We study this model in the presence of an eavesdropper who can eavesdrop the orthogonal links from the source to the relays as DRAFT a way that only a single source-relay link is active in each sub-scheme. April 8, 2018 DRAFT 5 Note that for N = 1, ds = min α, M −1 M can be shown to be achievable by time-sharing between (α, ds) = (0, 0) and (α, ds) = ( M −1 M , M −1 M ). For N ≥ 2, ds = min N α, Nα+M −1 M +1

Optimal Secure GDoF of Symmetric Gaussian Wiretap Channel with a Helper

“…In those settings, the messages are transmitted over the channels with secrecy constraints, which often incur a penalty in capacity (cf. [10], [13], [19], [24], [25], [28], [29], [31], [33], [37], [38], [40]). One way to minimize the capacity penalty incurred by secrecy constraints is to add helper(s) into the channels (see, e.g., [25], [33], [34], [36], [39], [41]- [45]).…”