End-To-End Performance Analysis of Two-Hop Asynchronous Cooperative Diversity

International audienceFor mobile users without antenna arrays, transmission diversity can be achieved with cooperative space-time encoded transmissions. This paper present an end-to-end performance analysis of Two-Hop asynchronous cooperative diversity with regenerative relays over Rayleigh Block-Flat-Fading channel. We present a precoding frame-based scheme with packet-wise encoding which enables best synchronization and channel estimation. We derive the bit-error rate and the end-to-end bit-error rate expressions for binary phase-shift keying. We present the performance of the frame-error rate and the end-to-end frame-error rate. Finally, comparisons between three system configurations are presented. Numerical results show that the simulations coincide with the analytical results

Spectrally-efficient SIMO relay-aided underlay communications: An exact outage analysis

International audienceIn this paper, we carry out an exact outage analysis for a secondary (unlicensed) system operating under a strict primary (licensed) system outage constraint. We focus on single-user singleinput multiple-output (SIMO) secondary communications where the direct link is being assisted by a cluster of single-antenna decodeand-forward (DF) relay nodes acting in a half-duplex selective-andincremental relaying mode. Firstly, we derive a transmit power model for the secondary system where the source and relays adapt their transmit power based on: 1) a perfect acquisition of the underlying interference channel state information (I-CSI), and 2) an interference constraint that is either fixed or proportional to the primary system outage probability. Secondly, the cumulative distribution functions (CDF)s of the received signal-to-noise ratio (SNR) at the secondary receiving nodes are devised in a recursive and tractable closed-form expressions. These statistics are used to derive the exact end-to-end secondary system outage probability. The analytical and simulation results are then compared and interestingly shown to perfectly match, while revealing that with a moderate number of primary and secondary receive antennas, the secondary system spectral efficiency is amply enhanced as opposed to being severely degraded in the single receive antenna case

Exact Outage Probability Analysis for Relay-aided Underlay Cognitive Communications

International audienceIn a spectrum sharing underlay context, we investigatethe exact derivation of the outage probability for relay-aided cognitiveradio communications. To give more degrees of freedom to thesecondary system in acquiring a targeted quality-of-service (QoS)under the primary system interference constraint, the secondary linkis assisted by a set of relays acting in a two-hop decode-and-forwardselective relaying mode. By means of the cumulative distributionfunctions of the received signal-to-noise ratio (SNR) at the secondaryreceiver, we derive the end-to-end outage probability of the secondarysystem in its closed form. The analytical and simulation results arethen compared and interestingly shown to perfectly match over theentire interference threshold region

Securing Untrusted RF-EH Relay Networks Using Cooperative Jamming Signals

We propose a new scheme to secure a wireless-powered untrusted cooperative-communication network, where a legitimate source node (Alice) transmits her information messages to a legitimate destination node (Bob) through the multiple amplify-and-forward untrusted relays. The relay nodes are assumed to be honest but curious nodes; hence, they are trusted at the service level but are untrusted at the information level. To reduce the energy consumption of the network, only one relay node is selected in each time slot to forward Alice's information signal. We assume a power-splitting-based energy-harvesting scheme, where each relay node splits its received signal into information and energy streams. Since the relay nodes are assumed to be untrusted at the information level, they attempt to decode the information intended to Bob while harvesting energy at the same time. When the relaying mode is selected, the scheme is realized over two non-overlapping time phases. To prevent any information leakage to the untrusted relay nodes, Bob and a cooperative jammer (John) inject jamming (artificial noise) signals during the first phase. During the second phase, the untrusted relay nodes that will not be forwarding the information signal must harvest energy to accumulate more energy to help Alice in future time slots. Moreover, the cooperative jammer will jam the untrusted relays to further power their batteries and prevent them from decoding the information-forwarding relay signal in case they decided to cheat and decode it. We model the battery state transitions at each relay as a finite-state Markov chain and analyze it. Our numerical results show the security gains of our proposed scheme relative to two benchmark schemes.This work was supported by NPRP from the Qatar National Research Fund (a member of Qatar Foundation) under Grant 8-627-2-260. The statements made herein are solely the responsibility of the authors.Scopu

TAS Strategies for Incremental Cognitive MIMO Relaying: New Results and Accurate Comparison

In this paper, we thoroughly elaborate on the impact different transmit-antenna selection (TAS) strategies induce in terms of the outage performance of incremental cognitive multiple-input multiple-output (MIMO) relaying systems employing receive maximum-ratio combining (MRC). Our setup consists of three multi-antenna secondary nodes: a transmitter, a receiver and a decode-and-forward (DF) relay node acting in a half-duplex incremental relaying mode whereas the primary transmitter and receiver are equipped with a single antenna. Only a statistical channel-state information (CSI) is acquired by the secondary system transmitting nodes to adapt their transmit power. In this context, our contribution is fourfold. First, we focus on two TAS strategies that are driven by maxim