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 multicell 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.

Resource Allocation for Cognitive Satellite Communications with Incumbent Terrestrial Networks

The goal of this paper is to propose Radio Resource Management (RRM) techniques, i.e. carrier, power and bandwidth allocation, for a shared spectrum utilization scenario where the satellite system aims at exploiting the spectrum allocated to terrestrial networks as the incumbent users without imposing harmful interference to them. In the context of SANSA, this work brings new RRM techniques that can be easily extrapolated for enabling the shared satellite downlink/uplink and terrestrial backhaul network. In connection to specific tasks within the framework of SANSA this work is related to WP3, Tasks 3.1, 3.2 and 3.3.

BP-MR: Backpressure Routing for the Heterogeneous Multi-Radio Backhaul of Small Cells

Dense deployments of small cells (SC) will help satisfying the explosive growth of mobile data usage. However the deployment of such networks implies several challenges where point-to-point (PTP) and point-to-multipoint (PMP) wirelesss technologies will be combined forming multipoint-to-multipoint (MP2MP) wireless mesh backhauls. In this initial work produced within the SANSA project, we propose Backpressure for Multi-Radio (BP-MR), a distributed dynamic routing and load balancing protocol designed for MP2MP wireless mesh bakchauls where each node may embed a different number of multi-technology wireless interfaces.

In BP-MR, each SC maintains a data queue per interface and carries out the routing process in two stages. The first one distributes ingress packets with the goal of reducing the Head of Line (HoL) blocking effect in a multi-radio SC. The second stage determines the actual outgoing interface and the next-hop for each packet  at the head of the queues. Simulation results show improvements in throughput and latency with respect to other state-of-the-art approaches as a consequence of an improved wireless link usage efficiency. Future work within SANSA project will consider the enhancement of this protocol in the proposed LTE hybrid backhaul network.

Multicast Multigroup Beamforming for Per-antenna Power Constrained Large-scale Arrays

Large in the number of transmit elements, multi-antenna arrays with per-element limitations are in the focus of the present work. In this context, physical layer multigroup multicasting under per-antenna power constrains is investigated herein. To address this complex optimization problem, low complexity alternatives to semi-definite relaxation are proposed. The goal is to optimize the per-antenna power constrained transmitter in a maximum fairness sense, which is formulated as a non-convex quadratically constrained quadratic problem. Therefore, the recently developed tool of feasible point pursuit and successive convex approximation is extended to account for practical per-antenna power constraints. Interestingly, the novel iterative method exhibits not only superior performance in terms of approaching the relaxed upper bound, but also a significant complexity reduction, as the dimensions of the optimization variables increase. Consequently, multicast multigroup beamforming for large-scale array transmitters with per-antenna dedicated amplifiers is rendered computationally efficient and accurate. A preliminary performance evaluation in large-scale systems for which the semi-definite relaxation constantly yields non rank-1 solutions is presented.

In the context of SANSA, this work employs smart antenna systems to provide point to multipoint access for terrestrial networks. The goal is to maximize the fairness in the system by managing the interference among the users. As the title suggests, such a framework suits well with multicasting scenarios considered in SANSA. More specifically, it is closely related to WP3, Tasks 3.1 and 3.2 as well as WP4, Task 4.3.

Power Control for Satellite Uplink and Terrestrial Fixed-Service Co-existence in Ka-band

A fundamental problem facing the next generation of Satellite Communications (SatComs) is the spectrum congestion and how the scarce spectral resources are allocated to meet the demand for higher rate and reliable broadband communications. In this context, this paper addresses the satellite uplink where satellite terminals reuse frequency bands of Fixed-Service (FS) terrestrial microwave links which are the incumbent users in the Ka band. In this scenario, the transmit power of the satellite terminals has to be controlled such that the aggregated interference caused at the FS system is kept below some acceptable threshold. In this paper, we review simple and efficient power allocation techniques available in the literature and, with slight adaptations, we evaluate them to the proposed satellite uplink and terrestrial FS co-existence scenario. The presented numerical results highlight the tradeoff between the level of channel state information and the rates that can be achieved at the satellite network.

In the context of SANSA, this work brings new techniques in power allocation for the shared satellite uplink and terrestrial backhaul network access so as to avoid interference to the terrestrial Ka band backhaul network and the same time achieve a high and fair per user throughput. In connection to specific tasks within the framework of SANSA this work is related to WP3, Tasks 3.1, 3.2 and 3.3