In this paper outage performance of a secondary user (SU) is evaluated under an amplify and forward (AF) relay selection scheme with an imperfect channel state information (CSI) while the SU shares spectrum in an underlay cognitive radio network (CRN). In underlay, the SU coexists with primary user (PU) in the same band provided the interference produced by SU at the PU receiver is below an int...

Cognitive radio (CR) systems allow unlicensed secondary users to transmit on the licensed frequency bands without degrading the transmissions of licensed primary users. Combining CR with other emerging techniques such as multi-antenna relaying may bring many benefits for the secondary transmissions. In this study, the authors propose and investigate a new relay-based cooperation scheme for a CR...

In order to compare the performances of three transmission schemes of keyinterest able to reach the maximum diversity order, guarantee of robust transmission, we used a dual-polarization channel model to take into account polarization diversity and transmit/receive correlation. These schemes under study were i)two systems using full channel state information (CSI) at the transmitter side (Tx-CS...

In this paper, the feasibility of a new downlink transmission mode in massive multi-input multi-output (MIMO) systems is investigated with two types of users, i.e., the users with only statistical channel state information (CSI) and the users with imperfect instantaneous CSI. The problem of downlink precoding design with mixed utilization of statistical and imperfect instantaneous CSI is addres...

In this article, the effect of power and rate adaptation on the spectral efficiency of orthogonal frequency division multiplexing (OFDM) systems using M-ary quadrature amplitude modulation (MQAM) is investigated in the presence of frequency selective and very rapidly time-varying fading channels, under power and instantaneous bit error rate (BER) constraints. Lower bounds on the maximum spectra...

We investigate the performance of multi-user multiple-input-single-output (MU-MISO) downlink in the presence of the mutual coupling effect at the transmitter. Contrary to traditional approaches that aim at eliminating this effect, in this paper we propose a joint analog-digital (AD) beamforming scheme that exploits this effect to further improve the system performance. A jointly optimal AD beam...

This work identifies the optimal sum degrees-of-freedom (DoF) of the K-user MISO Broadcast Channel (BC), in the presence of delayed channel-state information at the transmitter (CSIT) and additional current CSIT of imperfect precision. In a setting where the current channel estimation error scales — in the high SNR regime — as SNR−α for α ∈ [0, 1], the optimal sum-DoF takes the simple form (1 −...

This paper proposes a new algorithm to improve the throughput of the MIMO interference channel, under imperfect channel state information (CSI). Each transmitter and receiver has respectively and antennas and network operates in a time division duplex mode. With the knowledge of channel estimation error variance, mean of signal-to-interference-plus-noise ratio (SINR) is approximated. Each trans...

Multiple input multiple output (MIMO) systems provide dramatic capacity gain through an increased spatial dimension. However, the capacity gain is reduced if the channel state information (CSI) is not perfectly known. Thus, to improve MIMO system performance, CSI at the transmitter (CSIT) and receiver (CSIR) should be used efficiently. Uncertainties in CSI arise mainly due to imperfect channel ...

Energy harvesting is a promising technology to overcome the energy bottleneck in batterypowered heterogeneous sensor networks (HSNs). In an energy harvesting HSN, heterogeneous sensor nodes harvest energy to power themselves, and use the harvested energy for data transmission. This paper investigates a multiple-input single-output wireless powered HSN with imperfect channel state information (C...