Konstantinos Ntougias

Dynamic LSA for 5G networks the ADEL perspective

Exploiting additional radio spectrum is key to respond to the unprecedented capacity demands of mobile broadband communication systems in recent years. In fact, most of the frequency bands suitable for mobile communications are already in use by other radio services, and spectrum refarming is usually not possible or constitutes a highly time-consuming procedure. At the same time, several field measurement campaigns have shown that the occupied spectrum below 6GHz is severely underutilized, i.e. there exist “spectrum holes” in the time, frequency, and space dimensions, pointing to the possibility of using spectrum sharing as a mean to better exploit additional spectral resources. Licensed shared access (LSA) is a recent spectrum licensing paradigm that allows licensees to share the licensed spectrum of incumbents without causing harmful interference and ensuring a certain quality-of-service (QoS) for both types of players. The EU-funded project ADEL aims to enhance the current LSA paradigm by introducing 1) dynamic radio resource management (RRM), 2) sensing reasoning, based on database-assisted collaborative sensor networking, and 3) an extension to the LSA architecture that allows a more effective RRM, increasing QoS satisfaction and policy enforcement for all players, finally leading to an overall improved spectrum utilization. The key features of ADELs enhanced LSA paradigm are outlined throughout the remainder of this paper.

Coordinated MIMO with single-fed load-controlled parasitic antenna arrays

In this work, we present a method that enables the application of robust, low-complexity, arbitrary channel-aware precoding at single-fed load-controlled parasitic antenna arrays. Moreover, we describe the extension of this technique to multi-cell setups. Finally, we evaluate the sum-rate throughput performance of several multi-cell precoding schemes through numerical simulations based on realistic radiation patterns generated by antenna design software as well as on a scattering environment model. The results of the simulations confirm the expected performance gains over conventional single-fed configurations.

Robust low-complexity arbitrary user- and symbol-level multi-cell precoding with single-fed load-controlled parasitic antenna arrays

In this work, we present a novel technique that enables us to perform robust, low-complexity, arbitrary channel-aware precoding with single-fed load-controlled parasitic antenna arrays. Moreover, we describe the extension of this method to symbol-level and multi-cell precoding scenarios. Finally, we evaluate the sum-rate (SR) throughput performance of multi-cell zero-forcing (ZF) precoding through numerical simulations based on realistic radiation patterns generated by antenna design software as well as on a scattering environment model. Both user-level and symbol-level variants of this precoding method are considered. In addition, a power allocation (PA) scheme which is known for maximizing the SR capacity of coordinated ZF precoding under per base station power constraints is applied in both cases. The simulation results showcase the validity of the proposed approach and illustrate the superiority of symbol-level ZF precoding against its user-level counterpart as well as of the employed PA scheme over the uniform PA method.

Spectrum sharing in hybrid terrestrial-satellite backhaul networks in the Ka band

This work evaluates interference mitigation mechanisms to enable the operation of self-organizing hybrid terrestrial-satellite networks with aggressive frequency reuse between terrestrial and also satellite links. The objective is to take advantage of the improved capacity and resilience to congestion of such networks while assuring and efficient use of the spectrum. In particular, single- and multi-user hybrid analog-digital beamforming (HADB) techniques are considered as well as hybrid carrier allocation. The simulation results show network spectral efficiency improvements, with respect to conventional terrestrial backhaul systems, up to 2× when applying carrier allocation, and between 3.5× to 9× applying HADB in different environments.

Low-complexity air-interface-agnostic cooperative parasitic multi-antenna spectrum sharing system

Responding to the IEEE DySPAN 2015 5G Spectrum Sharing Challenge, in this paper we propose a SU system that is equipped with a parasitic antenna array and incorporates a low-rate feedback technique in order to accomplish highly efficient spectrum sharing. This approach optimizes the performance of both the PU and SU systems, in terms of the achieved throughputs, without the latter system having knowledge of the former systems link features.

Interference avoidance and mitigation techniques for hybrid satellite-terrestrial networks

In this chapter, we described interference avoidance and mitigation techniques for hybrid satellite-terrestrial MBH systems. More specifically, we considered a hybrid backhaul setup where the satellite segment off-loads the terrestrial one and enhances the overall capacity of the system. Moreover, we assumed that these two segments share the same spectrum, in order to utilize more efficiently this scarce and expensive resource. In addition, in the proposed system, the backhaul nodes are equipped with antenna arrays instead of drum antennas and make use of multiantenna communication techniques.

Large load-controlled multiple-active multiple-passive antenna arrays: Transmit beamforming and multi-user precoding

In this work, we present the design of a novel large load-controlled multiple-active multiple-passive (LC-MAMP) antenna array that operates at 19.25 GHz. In addition, we describe a method that enables us to perform robust, low-complexity, arbitrary channel-dependent precoding with such arrays as well as a communication protocol that limits the computational complexity associated with beam tracking and dynamic load computation in static or low-mobility scenarios, such as indoor wireless access or wireless terrestrial backhaul use cases. Finally, we study the application of various user- and symbol-level precoding schemes in coordinated multiple-input multiple-output setups equipped with LC-MAMP arrays and we evaluate their performance through numerical simulations using a realistic channel model. The simulation results show that LC-MAMPs outperform equivalent digital antenna arrays.

Single- and multiple-RF load controlled parasitic antenna arrays operating at Cm-wave frequencies: Design and applications for 5G wireless access / backhaul

MIMO technology is expected to play a key role in the endeavour to reach the capacity target of 5G systems, in conjunction with the use of frequencies above 6 GHz. This communication paradigm is anticipated to be utilised also in the wireless backhaul domain, in order to meet the high capacity requirements of the future wireless transport networks. The performance of the considered MIMO transmission methods is determined by the number of antennas that can be deployed on the transmitting nodes, which in turn is limited by cost and energy consumption constraints. Load controlled parasitic antenna arrays represent a type of antenna systems which are able to boost the performance of these communication schemes, while employing a small number of antennas. In this paper, we present the design of single- and multiple-fed parasitic antenna arrays operating at the 19 GHz frequency band. Moreover, we describe a simple and robust technique that allows us to perform arbitrary channel-dependent precoding with such arrays. Furthermore, we study a low-complexity communication protocol that can be applied to setups that are equipped with such antenna systems and used in low-mobility scenarios, such as wireless backhaul applications. The numerical simulation results showcase the validity of these approaches for both wireless access and backhaul applications and demonstrate the superiority of the parasitic antenna arrays over equivalent, regarding the number of their antenna elements, antenna systems.

Enhancing LTE with Cloud-RAN and Load-Controlled Parasitic Antenna Arrays

Cloud radio access network systems, consisting of remote radio heads densely distributed in a coverage area and connected by optical fibers to a cloud infrastructure with large computational capabilities, have the potential to meet the ambitious objectives of next generation mobile networks. Actual implementations of C-RANs tackle fundamental technical and economic challenges. In this article, we present an end-to-end solution for practically implementable C-RANs by providing innovative solutions to key issues such as the design of cost-effective hardware and power-effective signals for RRHs, efficient design and distribution of data and control traffic for coordinated communications, and conception of a flexible and elastic architecture supporting dynamic allocation of both the densely distributed RRHs and the centralized processing resources in the cloud to create virtual base stations. More specifically, we propose a novel antenna array architecture called load-controlled parasitic antenna array (LCPAA) where multiple antennas are fed by a single RF chain. Energy- and spectral-efficient modulation as well as signaling schemes that are easy to implement are also provided. Additionally, the design presented for the fronthaul enables flexibility and elasticity in resource allocation to support BS virtualization. A layered design of information control for the proposed end-to-end solution is presented. The feasibility and effectiveness of such an LCPAA-enabled C-RAN system setup has been validated through an over-the-air demonstration.

Low-feedback cooperative opportunistic transmission for dynamic licensed shared access

In order to meet the exponentially growing capacity demands of future mobile radio communication systems, the synergy of spectrum sharing methods, multi-antenna transmission schemes, small-cell offloading, and cooperative communication techniques is suggested. In this context, the mitigation of harmful interference, the provision of quality of service (QoS) guarantees, and the minimization of backhaul and channel state information (CSI) overhead are key challenges that have to be addressed. In this paper, we study the performance of a Licensed Shared Access (LSA) system comprised of a macro-cell sector (incumbent operator) and three partially overlapping small cells (licensee operator) placed within that sector. The small cells utilize a new low-feedback cooperative opportunistic beamforming (OBF) with proportional fair scheduling (PFS) transmission scheme to ensure that the proposed system is able to reach the mentioned goals above. Simulation results show that this system attains a substantial fraction of the available sum-rate capacity with minimal feedback.