Impact of outdated channel estimates on a distributed link-selection scheme for AF relaying networks

We investigate the impact of outdated channel estimates on the outage performance of a distributed link-selection scheme recently proposed for variable-gain amplify-and-forward relaying networks. In this scheme, either the direct link or the relaying link is preselected before each transmission, based on a distributed mechanism. We begin by showing that an exact analysis is rather intricate, yielding a multifold integral-form solution. Motivated by this, we then derive a simple closed-form lower bound, which, importantly, proves to be a very tight approximation to the exact outage probability. We also assess the system diversity order via asymptotic analysis42185188COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESnão te

Distributed TAS/MRC and TAS/SC schemes for fixed-gain AF systems with multiantenna relay: outage performance

Although transmit-antenna selection (TAS) is an alternative low-cost strategy to capture the advantages of multiantenna systems, its application may require a large amount of feedback transmissions. Owing to this fact and in order to reduce such requirement, herein we analyze the outage performance of two distributed TAS (DAS) schemes. One scheme employs maximal-ratio combining (DAS/MRC) at the destination, whereas the other employs selection combining (DAS/SC). We consider a dual-hop fixed-gain amplify-and-forward relaying network, equipped with multi-antenna source/relay nodes and a single-antenna destination. A lower bound expression is derived for the outage probability of each investigated scheme. Importantly, the derived bounds prove to be very tight approximations to the exact outage performance. Also, capitalizing on a strikingly interesting property of Stirling numbers of the second kind, we provide closed-form asymptotic expressions for the obtained bounds. Our results show that the diversity order of the proposed distributed schemes is identical to that of their optimal centralized counterparts, namely N-t + min(N-rr, N-rt), with N-t, N-rr, and N-rt denoting the number of transmit antennas at the source, the number of receive antennas at the relay, and the number of transmit antennas at the relay, respectively. In addition, as the relay approaches the destination, the outage performance of the proposed schemes approaches the optimal one15643804392COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESnão te

An efficient power allocation scheme for multirelay systems with lossy intra-links

The so-called chief executive officer problem suggests that the source message can be recovered at the destination by merging a set of corrupted replicas forwarded by multiple relays, as long as these replicas are sufficiently correlated with the original message. In this paper, we build on Slepian-Wolf's correlated source coding theorem to design a simple, yet efficient power allocation scheme for a multirelay system, in which the direct link is unavailable to convey information. In such a system, the replicas forwarded by the relays are allowed to contain intra-link errors due to previous unreliable hops, and the destination is supposed to retrieve the source message by jointly decoding all received replicas. Importantly, the proposed power allocation is asymptotically optimal at high signal-to-noise ratio65415491560COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFINANCIADORA DE ESTUDOS E PROJETOS - FINEPFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPnão tem01.14.0231.002016/05847-0The authors would like to thank the European Union (FP7 project ICT-619555 RESCUE), the Brazilian Ministry of Education (CAPES), So Paulo Research Foundation (FAPESP, Grant No. 2016/05847-0), and Finep/Funttel (Grant No. 01.14.0231.00, under the Radiocommunication Reference Center project hosted by Inatel) for the financial support of this wor

Outage performance of spectrally efficient schemes for multiuser cognitive relaying networks with underlay spectrum sharing

We analyze the outage performance of two spectrally efficient schemes for exploiting multiuser diversity in cognitive relaying networks. We consider a secondary network composed by one source node communicating with the best one out of L available destinations, selected according to the channel quality of the direct links. If the transmission through the selected direct link drops below a given threshold, then a half-duplex decode-and-forward relaying transmission is invoked. At this stage, two schemes are considered. In the first scheme, the previously selected secondary destination employs maximal-ratio combining to handle the signals received from the secondary source and relay. In the second scheme, maximal-ratio combining is employed as well, but at a possibly different secondary destination, selected so as to maximize the signal-to-noise ratio at the combiner output. In both schemes, we consider an underlay spectrum-sharing mechanism. We derive exact analytical expressions for the outage probability of the proposed schemes and validate them by Monte Carlo simulations. An asymptotic analysis reveals that the proposed schemes can achieve full diversity order, equal to L+1. Importantly, we show that, at high signal-to-noise ratio, the mean spectral efficiency of the proposed schemes approximates that one attained by direct transmission131266296642COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESnão tem24th IEEE International symposium on personal, indoor and mobile radio communicatio

Outage analysis for decode-and-forward multirelay systems allowing intra-link errors

In the context of distributed source coding, the so-called many-help-one problem comprises a set of auxiliary sources aimed at helping the decoder retrieve a primary source. In this letter, we build on the newly derived admissible rate region of a certain binary many-help-one problem to obtain the outage probability (OP) of a decode-and-forward (DF) multirelay system that allows intra-link errors (IE) to be forwarded to the destination. In addition, for comparison, we obtain the OP of a conventional DF multirelay system, which discards any IEs. We show that, the more relays are employed, the more advantageous it is to forward the IEs, as opposed to discarding them66758761CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFINANCIADORA DE ESTUDOS E PROJETOS - FINEPFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP01.14.0231.00não tem2016/05847-0German Research Foundation (DFG) SFB 912; Federal Ministry of Education and Research within the programme "Twenty20 - Partnership for Innovation" 03ZZ0505

An adaptive transmission scheme for cognitive decode-and-forward relaying networks: half duplex, full duplex, or no cooperation

We propose an adaptive transmission scheme for cognitive decode-and-forward relaying networks, whereby, before each communication process, one out of three transmission modes is dynamically selected in order to maximize the instantaneous capacity of the system, namely, half-duplex (HD) relaying, full-duplex (FD) relaying, or direct transmission with no cooperation. The following key issues, relevant to underlay spectrum sharing and cooperative relaying, are considered: 1) the overall transmit power at the secondary network is constrained by both the maximum tolerable interference at the primary receiver and the maximum transmit power available at the secondary nodes; 2) under FD operation, the secondary relay is subject to residual self-interference, which is modeled as a fading channel; and 3) the signals coming from the secondary source and relay are handled at the secondary destination via maximal-ratio combining, in the HD relaying mode, and via a joint-decoding technique, in the FD relaying mode. We derive an exact analytical expression for the outage probability of the proposed scheme. Then, an approximate closed-form expression is proposed, and a corresponding asymptotic expression is derived. Monte Carlo simulations are run to validate the accuracy of the presented mathematical analysis and to showcase the tightness of the proposed approximation15855865602COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESnão temThis work was supported in part by the Brazilian Ministry of Education Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, in part by the Finnish Centre for International Mobility, and in part by the Tekes and Academy of Finlan