• Thursday, 15 June, 9:00-10:30, Room Theatre Small Stage
  • Session Chair: Pekka Pirinen (University of Oulu, Finland)


09:00 Minimum Power Based Relay Selection for Orthogonal Multiple Access Relay Networks

Ayswarya Padmanabhan (University of Oulu & CWC - Radio Technologies, Finland); Valtteri Tervo, Jiguang He and Markku Juntti (University of Oulu, Finland); Tad Matsumoto (Japan Advanced Institute of Science and Technology, Japan)

We analyze the performance of a multi-source multi-helper transmission with lossy forward (LF) relaying. In LF, estimates at the relay are encoded and forwarded to the destination for improving the reliability of the received sequence transmitted from the multiple source nodes. Unlike the conventional decode-and-forward (DF) relaying, LF sends the data even in the case where decoding is not error-free. We extend the results of the channel with multiple sources and a single helper to perform relay selection by utilizing the union of rate regions. A power minimization problem is formulated using the above strategy and solved by exploiting the successive convex approximation (SCA) technique. Numerical results are presented to show that the proposed relay selection method achieves the same performance as the exhaustive search.


09:18 Channel Estimation for Diffusive MIMO Molecular Communications

Seyed Mohammadreza Rouzegar and Umberto Spagnolini (Politecnico di Milano, Italy)

In diffusion-based communication, as for molecular systems, the achievable data rate is very low due to the slow nature of diffusion and existence of severe inter-symbol-interference (ISI). Multiple-input multiple-output (MIMO) technique can be used to improve the data rate. Knowledge of channel impulse response (CIR) is essential for equalization and detection in MIMO systems. This paper presents a training-based CIR estimation for diffusive MIMO (D-MIMO) channels. Maximum likelihood and least-squares estimators are derived, and the training sequences are designed to minimize the corresponding Cram´er-Rao bound. Sub-optimal estimators are compared to Cram´er-Rao bound to validate their performance.


09:36 Energy-Efficient Transmission Strategies for Multiantenna Downlink

Kien-Giang Nguyen, Oskari Tervo, Quang-Doanh Vu and Markku Juntti (University of Oulu, Finland); Le-Nam Tran (Maynooth University, Ireland)

Energy efficiency (EE) is becoming one of the important criteria in wireless transmission design. This paper discusses the recently proposed energy-efficient transmit beamforming designs for multicell multiuser multiple-input single-output (MISO) systems, including maximizing overall network EE, sum weighted EE and fairness EE. Generally, the EE optimization problems are NP-hard nonconvex programs for which finding the globally optimal solutions is challenging. For low-complexity suboptimal approaches, there is a class of solutions conventionally developed based on parametric transformations. However, those have been revealed problematic in terms of computational complexity and convergence. To overcome these issues, novel algorithms have been recently developed based on the state-of-the-art successive convex approximation (SCA) framework. Here we sum up the basic concepts of the algorithms and provide numerical results which illustrate the solution quality compared to the existing methods.


09:54 Enhanced Sparse Bayesian Learning-based Channel Estimation for Massive MIMO-OFDM Systems

Hayder Al-Salihi and Mohammad Reza Nakhai (King's College London, United Kingdom (Great Britain)); Tuan Anh Le (Middlesex University, United Kingdom (Great Britain))

Pilot contamination limits the potential benefits of massive multiple input multiple output (MIMO) systems. To mitigate pilot contamination, in this paper, an efficient channel estimation approach is proposed for massive MIMO systems, using sparse Bayesian learning (SBL) namely coupled hierarchical Gaussian framework where the sparsity of each coefficient is controlled by its own hyperparameter and the hyperparameters of its immediate neighbours. The simulation results show that the proposed method can reconstruct original channel coefficients more effectively compared to the conventional channel estimators in terms of channel estimation accuracy in the presence of pilot contamination.


10:12 Patch Antenna Design for Full-Duplex Transceivers

Juan Laco and Fernando Gregorio (Universidad Nacional del Sur, Argentina); Gustavo J. González (CONICET & Universidad Nacional del Sur, Argentina); Juan E. Cousseau (Universidad Nacional del Sur, Argentina); Taneli Riihonen and Risto Wichman (Aalto University School of Electrical Engineering, Finland)

We present the design, implementation and validation (by measurements) of a two-element antenna array for inband full-duplex (FD) applications. The antenna array is designed to provide large isolation between its transmission and reception ports by changing the polarization of the channels and by designing a suitable radiation pattern for the transmission antennas. Especially, the design of the antenna array is developed by tuning the characteristic S-parameters of the antenna elements so that isolation levels larger than 55 dB are achieved without degrading the far-field transmission pattern. Simulation and measurement results show that the proposed antenna design could be a promising solution for full-duplex applications, i.e., FD access points and/or FD sensing nodes in cognitive radio systems.