Resource and Mobility Management in the Network Layer of 5G Cellular Ultra-Dense Networks

© 2017 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] The provision of very high capacity is one of the big challenges of the 5G cellular technology. This challenge will not be met using traditional approaches like increasing spectral efficiency and bandwidth, as witnessed in previous technology generations. Cell densification will play a major role thanks to its ability to increase the spatial reuse of the available resources. However, this solution is accompanied by some additional management challenges. In this article, we analyze and present the most promising solutions identified in the METIS project for the most relevant network layer challenges of cell densification: resource, interference and mobility management.This work was performed in the framework of the FP7 project ICT-317669 METIS, which is partly funded by the European Union. The authors would like to acknowledge the contributions of their colleagues in METIS, although the views expressed are those of the authors and do not necessarily represent the project.Calabuig Soler, D.; Barmpounakis, S.; Giménez Colás, S.; Kousaridas, A.; Lakshmana, TR.; Lorca, J.; Lunden, P.... (2017). Resource and Mobility Management in the Network Layer of 5G Cellular Ultra-Dense Networks. IEEE Communications Magazine. 55(6):162-169. https://doi.org/10.1109/MCOM.2017.1600293S16216955

Coverage Analysis and Cooperative Hybrid Precoding for 5G Cellular Networks

5G innovations have been made in both the network deployment and the transceiver architectures in order to increase coverage, energy- and spectrum-efficiency. Future base stations (BSs) are expected to be densely deployed in places such as walls and lamp posts and cover a smaller area compared to current macro BS systems. Using large spectrum at millimeter-wave (mmWave) frequency bands and highly directional beamforming with large antenna arrays, 5G will bring gigabit-per-second data rate and low-latency communications and enable many novel services such as high-speed mmWave wireless interconnections between devices, vehicular communications, etc.. Moreover, mmWave communication systems will be based on novel hybrid beamforming architectures which have reduced hardware power consumption and cost. Thus, for better understanding of 5G performance and limitations, one of the main goals in this thesis is to analyze new models that give tractable performance metrics for dense small BS networks. Another goal in this thesis is to study mmWave hybrid beamforming schemes which enable joint transmissions in multi-cell multi-user systems. In the thesis, we show the advantages of small cells in increasing the coverage probability and reducing the path loss and shadowing, and we show the value of cooperation in terms of power consumption and outage. In [Paper A] we derive analytical expressions for the successful reception probability of the equal gain combining receiver in a network where interfering transmitters are distributed according to a Poisson point process and interfering signals are spatially correlated. The results show that the spatial correlation reduces the successful reception probability and the effect of the spatial correlation increases with the number of antennas.\ua0[Paper B] follows to study the performance of a partial zero forcing receiver. The results are simulated in an environment with blockages and are analyzed under both Rayleigh and Rician channels. The coverage probability is shown to be maximized when using a subset of antennas\u27 degree-of-freedom for useful signal enhancement and using the remaining degrees of freedom for canceling the interference from strongest interferers. Finally, in [Paper C], we propose a hybrid beamforming scheme which minimizes the total power consumption of a multi-cell multi-user network, subject to per-user quality-of-service constraints. The proposed scheme is based on decoupling the analog precoding and digital precoding. The analog precoders are only dependent on the local channel state information at each BS. Then, the digital precoders are obtained by solving a relaxed convex optimization for given analog precoders. Simulation results show that the proposed algorithm leads to almost the same RF transmit power as that of fully digital precoding, while saving considerable hardware power due to the reduced number of RF chains and digital-to-analog converters

Frequency Allocation in Non-Coherent Joint Transmission CoMP Networks

In this paper, we study the problem of joint transmission (JT) in coordinated multipoint (CoMP) networks from a new point of view where the system performance is optimized via frequency allocation for 5G small cells. Moreover, we investigate the implementation of hybrid automatic repeat request (HARQ), as an efficient scheme facing the feedback load problem in CoMP setups. The results are obtained for the cases with slow and fast fading conditions. Considering the channel state information (CSI) only at the receiver, we show that at low and medium signal to noise ratios (SNRs) sharing the frequency resources between users outperforms the case when the frequency resources are dedicated under non-coherent JT-CoMP setting. We find that the maximum long term throughput is achieved by either sharing the entire frequency resources between the users or allocating each user in a disjoint dedicated frequency resource. These extreme cases show the best performance in the SNR region of interest. Finally, as demonstrated analytically and numerically, HARQ feedback increases the long term throughput and reduces the outage probability substantially, with an affordable average delay

D4.3 Final Report on Network-Level Solutions

Research activities in METIS reported in this document focus on proposing solutions to the network-level challenges of future wireless communication networks. Thereby, a large variety of scenarios is considered and a set of technical concepts is proposed to serve the needs envisioned for the 2020 and beyond. This document provides the final findings on several network-level aspects and groups of solutions that are considered essential for designing future 5G solutions. Specifically, it elaborates on: -Interference management and resource allocation schemes -Mobility management and robustness enhancements -Context aware approaches -D2D and V2X mechanisms -Technology components focused on clustering -Dynamic reconfiguration enablers These novel network-level technology concepts are evaluated against requirements defined by METIS for future 5G systems. Moreover, functional enablers which can support the solutions mentioned aboveare proposed. We find that the network level solutions and technology components developed during the course of METIS complement the lower layer technology components and thereby effectively contribute to meeting 5G requirements and targets.Aydin, O.; Valentin, S.; Ren, Z.; Botsov, M.; Lakshmana, TR.; Sui, Y.; Sun, W.... (2015). D4.3 Final Report on Network-Level Solutions. http://hdl.handle.net/10251/7675