Real-World Evaluation of Full-Duplex Millimeter Wave Communication Systems

Noteworthy strides continue to be made in the development of full-duplex millimeter wave (mmWave) communication systems, but most of this progress has been built on theoretical models and validated through simulation. In this work, we conduct a long overdue real-world evaluation of full-duplex mmWave systems using off-the-shelf 60 GHz phased arrays. Using an experimental full-duplex base station, we collect over 200,000 measurements of self-interference by electronically sweeping its transmit and receive beams across a dense spatial profile, shedding light on the effects of the environment, array positioning, and beam steering direction. We then call attention to five key challenges faced by practical full-duplex mmWave systems and, with these in mind, propose a general framework for beamforming-based full-duplex solutions. Guided by this framework, we introduce a novel solution called STEER+, a more robust version of recent work called STEER, and experimentally evaluate both in a real-world setting with actual downlink and uplink users. Rather than purely minimize self-interference as with STEER, STEER+ makes use of additional measurements to maximize spectral efficiency, which proves to make it much less sensitive to one's choice of design parameters. We experimentally show that STEER+ can reliably reduce self-interference to near or below the noise floor while maintaining high SNR on the downlink and uplink, thus enabling full-duplex operation purely via beamforming.Comment: This paper has been submitted to the IEEE for review and possible publication; copyright may change without notic

Massive MIMO Channel Estimation for Millimeter Wave Systems via Matrix Completion

Millimeter Wave (mmWave) massive Multiple Input Multiple Output (MIMO) systems realizing directive beamforming require reliable estimation of the wireless propagation channel. However, mmWave channels are characterized by high variability that severely challenges their recovery over short training periods. Current channel estimation techniques exploit either the channel sparsity in the beamspace domain or its low rank property in the antenna domain, nevertheless, they still require large numbers of training symbols for satisfactory performance. In this paper, we present a novel channel estimation algorithm that jointly exploits the latter two properties of mmWave channels to provide more accurate recovery, especially for shorter training intervals. The proposed iterative algorithm is based on the Alternating Direction Method of Multipliers (ADMM) and provides the global optimum solution to the considered convex mmWave channel estimation problem with fast convergence properties.Comment: 5 pages, 3 figures, accepted to IEEE SP

Full-Duplex Wireless for 6G: Progress Brings New Opportunities and Challenges

The use of in-band full-duplex (FD) enables nodes to simultaneously transmit and receive on the same frequency band, which challenges the traditional assumption in wireless network design. The full-duplex capability enhances spectral efficiency and decreases latency, which are two key drivers pushing the performance expectations of next-generation mobile networks. In less than ten years, in-band FD has advanced from being demonstrated in research labs to being implemented in standards and products, presenting new opportunities to utilize its foundational concepts. Some of the most significant opportunities include using FD to enable wireless networks to sense the physical environment, integrate sensing and communication applications, develop integrated access and backhaul solutions, and work with smart signal propagation environments powered by reconfigurable intelligent surfaces. However, these new opportunities also come with new challenges for large-scale commercial deployment of FD technology, such as managing self-interference, combating cross-link interference in multi-cell networks, and coexistence of dynamic time division duplex, subband FD and FD networks.Comment: 21 pages, 15 figures, accepted to an IEEE Journa

Performance Analysis of Multi-User MIMO Schemes under Realistic 3GPP 3-D Channel Model for 5G mmWave Cellular Networks

Novel techniques such as mmWave transmission and massive MIMO have proven to present many attractive features able to support high data demand for 5G NR technologies. Towards the standardization of 5G networks, channel modeling has become an important step in order to test the reliability of theoretical studies. In this paper, we study the performance of a 5G network at mmWave range for the downlink. We consider a single trisectorized base station equipped with planar arrays, and we model users as a spatial Poisson process in a hexagonal grid. We adopt the latest 3GPP channel model described in TR 38.901 and we provide a thorough description and step-by-step tutorial of it along with our customizations and MATLAB scripts for channel generation in the presented scenario. Moreover, we evaluate the performance of Multi-User Multi-Layer MIMO techniques, such as Signal-to-Leakage-plus-Noise Ratio (SLNR) precoding and MMSE combined with different system configurations by means of achievable per-user rate

Millimetriaaltopohjainen runkoyhteys ultratiheille langattomille verkoille - Itseasentuvien verkkoelementtien analyysi

The amount of wireless traffic and number of connected devices are expected to explode in the coming future. By the year 2020 the amount of data traffic is forecasted to grow 1000 times from 2010 levels and the amount of connected devices is expected to reach 50 billion. One reason to these numbers is massive increase in machine type communications. 5G networks have been envisioned to address these challenges. In the 5G network concept the networks are getting denser than ever before. Millimeter wave communications play an important role in backhauling of the mobile traffic as deploying optical fiber to every small node is most likely going to be too cost intensive for operators. Efficient deployment of an ultra-dense wireless network requires that the devices support so called “plug and play” installation. In practice it means that a mechanic installing a new radio node should only perform physical mounting of the device. Antenna alignment and link setup processes should be fully automated. The purpose of this thesis is to study practical issues and possible solutions of realizing the plug and play installation in a cost efficient way. This study will define scenarios and functional requirements of adding access nodes to backhaul networks. Technical evaluation of link discovery process and cost analysis on plug and play installation of access nodes are conducted.Tulevaisuudessa langattomien laitteiden määrän ja niiden generoiman liikenteen odotetaan kasvavan räjähdysmäisesti. Vuoteen 2020 mennessä verkoissa siirrettävien datamäärien on ennustettu kasvavan tuhatkertaisiksi vuoden 2010 tasosta, ja liitettyjen laitteiden määrän odotetaan nousevan 50 miljardiin. Yksi syy näihin on koneiden välisen viestinnän massiivinen kasvu. 5G-verkkoja on kaavailtu vastaamaan edellä mainittuihin haasteisiin. Osana 5G-konseptia verkkojen odotetaan rakentuvan tiheämmiksi kuin koskaan aiemmin. Millimetriaaltoihin pohjautuvat linkit tulevat olemaan merkittävässä roolissa mobiilidatan siirtämisessä radionoodeista runkoverkkoon, koska optisen kuidun rakentaminen jokaiselle pienelle noodille tulisi mitä luultavimmin operaattoreille liian kalliiksi. Ultratiheiden verkkojen tehokas rakentaminen vaatii, että asennettavat laitteet tukevan niin sanottua itseasennusta. Käytännössä se tarkoittaa sitä, että asentajan täytyy ainoastaan suorittaa radionoodin fyysinen asennus. Antenniensuuntaus- ja linkinmuodostusprosessien tulisi olla täysin automatisoituja. Tämän diplomityön tarkoituksena on tutkia kustannustehokkaaseen itseasennukseen liittyviä käytännön ongelmia sekä mahdollisia ratkaisuita. Tutkimus määrittelee skenaariot ja funktionaaliset vaatimukset radionoodien lisäämiseksi osaksi operaattorin verkkoa. Työ sisältää linkkienmuodostusprosessin teknisen evaluoinnin, sekä kustannusanalyysin tiheiden verkkojen rakentamisesta hyödyntäen itseasennustekniikkaa

Interference Exploitation via Symbol-Level Precoding: Overview, State-of-the-Art and Future Directions

Interference is traditionally viewed as a performance limiting factor in wireless communication systems, which is to be minimized or mitigated. Nevertheless, a recent line of work has shown that by manipulating the interfering signals such that they add up constructively at the receiver side, known interference can be made beneficial and further improve the system performance in a variety of wireless scenarios, achieved by symbol-level precoding (SLP). This paper aims to provide a tutorial on interference exploitation techniques from the perspective of precoding design in a multi-antenna wireless communication system, by beginning with the classification of constructive interference (CI) and destructive interference (DI). The definition for CI is presented and the corresponding mathematical characterization is formulated for popular modulation types, based on which optimization-based precoding techniques are discussed. In addition, the extension of CI precoding to other application scenarios as well as for hardware efficiency is also described. Proof-of-concept testbeds are demonstrated for the potential practical implementation of CI precoding, and finally a list of open problems and practical challenges are presented to inspire and motivate further research directions in this area

Terahertz Communications for 6G and Beyond Wireless Networks: Challenges, Key Advancements, and Opportunities

The unprecedented increase in wireless data traffic, predicted to occur within the next decade, is motivating academia and industries to look beyond contemporary wireless standards and conceptualize the sixth-generation (6G) wireless networks. Among various promising solutions, terahertz (THz) communications (THzCom) is recognized as a highly promising technology for the 6G and beyond era, due to its unique potential to support terabit-per-second transmission in emerging applications. This article delves into key areas for developing end-to-end THzCom systems, focusing on physical, link, and network layers. Specifically, we discuss the areas of THz spectrum management, THz antennas and beamforming, and the integration of other 6G-enabling technologies for THzCom. For each area, we identify the challenges imposed by the unique properties of the THz band. We then present main advancements and outline perspective research directions in each area to stimulate future research efforts for realizing THzCom in 6G and beyond wireless networks.Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

A Comprehensive Survey on Resource Allocation for CRAN in 5G and Beyond Networks

The diverse service requirements coming with the advent of sophisticated applications as well as a large number of connected devices demand for revolutionary changes in the traditional distributed radio access network (RAN). To this end, Cloud-RAN (CRAN) is considered as an important paradigm to enhance the performance of the upcoming fifth generation (5G) and beyond wireless networks in terms of capacity, latency, and connectivity to a large number of devices. Out of several potential enablers, efficient resource allocation can mitigate various challenges related to user assignment, power allocation, and spectrum management in a CRAN, and is the focus of this paper. Herein, we provide a comprehensive review of resource allocation schemes in a CRAN along with a detailed optimization taxonomy on various aspects of resource allocation. More importantly, we identity and discuss the key elements for efficient resource allocation and management in CRAN, namely: user assignment, remote radio heads (RRH) selection, throughput maximization, spectrum management, network utility, and power allocation. Furthermore, we present emerging use-cases including heterogeneous CRAN, millimeter-wave CRAN, virtualized CRAN, Non- Orthogonal Multiple Access (NoMA)-based CRAN and fullduplex enabled CRAN to illustrate how their performance can be enhanced by adopting CRAN technology. We then classify and discuss objectives and constraints involved in CRAN-based 5G and beyond networks. Moreover, a detailed taxonomy of optimization methods and solution approaches with different objectives is presented and discussed. Finally, we conclude the paper with several open research issues and future directions