- Wednesday, 14 June, 16:00-17:30, Room Theatre Piki Hall
- Session Chair: Kenta Umebayashi (Tokyo University of Agriculture and Technology, Japan)
Yeon-Geun Lim, Taehun Jung, Kwang Soon Kim and Chan-Byoung Chae (Yonsei University, Korea)
Fifth generation (5G) communication systems include enhanced mobile broadband, massive machine-type communication, and ultra-reliable low-latency communication. To support various 5G applications, researchers have considered multiple scalable subcarrier spacing and transmission time interval (TTI). In this paper, we introduce a concept of waveform multiplexing for frequency multiplexing of numerologies. Waveform multiplexing consists of different waveforms on subbands with scalable subcarrier spacing and TTI operating on one frequency band. The Waveform multiplexing also possesses dynamic cyclic prefix and minimum guard band, which are the key features for the high spectral efficiency. We verify the performance and the potential of the waveform multiplexing using 3-dimensional(3D) ray-tracing based system-level evaluation in realistic environments and 3D channels.
Laddu Praneeth Roshan Jayasinghe, Antti Tölli and Jarkko Kaleva (University of Oulu, Finland); Ganesh Venkatraman (University of Oulu & CWC, University of Oulu, Finland); Matti Latva-aho (UoOulu, Finland)
Traffic aware precoder/decoder design in multi-cell multi-user multiple-input multiple-output systems is considered with the objective of weighted queue minimization, where the original non-convex optimization problem is solved via successive convex approximation. Centralized pilot reuse algorithms for mitigating the pilot contamination are investigated to reflect the traffic aware optimization objective. Distinctive feature of the proposed pilot reuse algorithms is to utilize the user buffer state information jointly with the traditional large scale fading values when allocating the limited pilot resources among the served users. Numerical examples compare the performance of the proposed pilot reuse algorithms for varying number of available pilots and different traffic arrival models. The results demonstrate that significant performance gains are available when the pilot allocation strategy is designed to reflect closely the overall system optimization objective.
Mohammad Majidzadeh, Aleksi Moilanen, Nuutti Tervo, Harri Pennanen and Antti Tölli (University of Oulu, Finland); Matti Latva-aho (UoOulu, Finland)
Hybrid analog-digital beamforming has been recognized as a promising solution for a practical implementation of massive multiple-input multiple-output (MIMO) systems based on millimeter-wave technology. In this paper, three hybrid beamforming algorithms are proposed for single-user MIMO systems with partially connected radio frequency (RF) architecture, including a singular value decomposition (SVD) matching algorithm, an iterative orthogonalization algorithm, and a transmit-receive zero forcing (ZF) algorithm. The rate performance of the proposed algorithms is compared with fully digital and analog beamforming in a realistic geometry-based stochastic channel model. The simulation results show that the transmit-receive ZF is superior among hybrid methods, and it provides performance relatively close to that of the digital beamforming. In conclusion, carefully designed partially connected hybrid beamforming can obtain an excellent balance between hardware complexity and performance.
Heshani Gamage and Nandana Rajatheva (University of Oulu, Finland); Matti Latva-aho (UoOulu, Finland)
In this paper we analyze candidate coding schemes for enhanced mobile broadband communication (eMBB) of new radio (NR) in the 5th generation (5G) standard corresponding the activities in 3GPP. The schemes are evaluated in terms of block error rate (BLER), bit error rate (BER), computational complexity, and flexibility. These are the parameters under consideration for selection under different services where suitable performance is to be analyzed. We consider turbo, low density parity check (LDPC), and polar codes as candidate schemes. These are investigated in terms of obtaining suitable rates, block lengths by proper design for fair comparison. The simulations have been carried out in order to obtain BLER / BER performance for various code rates and block lengths.
Nazar Ali (Khaifa University, United Arab Emirates (UAE)); Ahmed Kulaib (Khalifa University, United Arab Emirates (UAE)); Ehab Salahat (Australian National University, Australia); Raed Shubair (Khalifa University (KU) & Massachusetts Institute of Technology (MIT), United Arab Emirates (UAE))
Wireless communications literature is very rich with empirical studies and measurement campaigns that study the nature of the wireless propagation channel. However, despite their undoubted usefulness, many of these studies have omitted a fundamental yet significant feature of the physical signal propagation, that is, wireless propagation asymmetry. This feature seems to stand in stark contrast to electromagnetic reciprocity theorem, and to the innumerable seminal research papers that adopt channel symmetry as an axiom, and hence rendering their modeling, unexpectedly, inaccurate. Besides, asymmetry is unquestionably an important characteristic of wireless propagation channels, which needs to be accurately modeled for vehicular/mobile communications, 5G networks, and associated applications such as indoor/outdoor localization. This paper presents a modest study that reports the potential causes of propagation asymmetry, based on reliably obtained data from well-controlled field measurements. We empirically prove that wireless channels are symmetric in the absence of symmetry impairments, which is an unrealistic assumption for practical wireless propagation scenarios. Key conclusions and recommendation are summarized. We believe that this study will be inspiring for the academic community and it will trigger further investigations within wireless propagation assumptions.
Lorenzo Combi and Umberto Spagnolini (Politecnico di Milano, Italy)
In this paper we consider a centralized radio access network (C-RAN) architecture with a fully analog fronthaul link between remote antenna units (RAUs) and baseband units (BBUs) based on the radio over fiber (RoF) paradigm. Beamforming to separate uplink signals received from a pool of users is splitted between RAU and BBU. Optical beamforming is performed at the RAU site with the aim of reducing the number of fronthaul channels and the corresponding analog/digital converters at the BBU, as mandatory for millimeter wave (mmWave) radio communication. Digital baseband processing completes the beamforming at the BBU and compensates for optical beamforming imperfections. In this paper the minimum mean square error (MMSE) beamforming is considered, paired with all-analog fronthauling for uplink. Spatial sparsity of the mmWave channel is leveraged for fronthaul compression through phase-only approximation of the dominant eigenvectors of the channel. Validation is on the radio-link capabilities employing multiple antennas to meet the demand for massive MIMO technology.