Comprehensive proceedings can be downloaded here. 

Presentations are downloadable next to the presentation title when they have been provided by the presenter.
All Wednesday presentations are downloadable here.
Thursday presentations are downloadable here.

Wednesday, 17 May 2017
(Merikoski Hall)

Opening Plenary

Keynote: Heikki Rantanen, Finnish MoD, "Radio Technical Evolution in the Finnish SDR Program" 
Keynote: Michael Street, NATO, "NATO Update on Ground Tactical Interoperability"

Perspective on Tactical Communications

SDR Standards and the SCA 1 

Philippe Cambraye, European Defense Agency, "SDR Standards"
Howen Fernando, JTNC, "JTNC Standards"
Eric Nicollet, Thales, "WInnForum SDR Standards"
Steve Bernier, NordiaSoft, "Performance Study Comparing SCA version 4.1 and SCAv2.2.2"

Over the last decade, more than four hundred thousand military radios have been produced based on the SCA standard for Software Defined Radios. Since 2006, radio manufacturers from around the world have been using the version 2.2.2 of the SCA specification to build radios. With so many radio projects and developers using the SCA, a number of relatively minor issues with the specification have been uncovered over time. Furthermore, the rise of heterogeneous multicore processors has also created some room for improvement of the SCA specification.

Between 2010 and 2016, the US DoD Joint Tactical Networking Center (JTNC) along with the Wireless Innovation Forum have launched a number of work groups to review the SCA specification. After several thousand hours of work, a few internal releases of the specification, and some experimentation, the SCA specification culminated into version 4.1 in August 2015.

Industry is now facing a transition phase. Manufacturers and governments are starting to consider version 4.1. Above all, the main question to answer is whether the new release of the specification can make a difference from an operational standpoint. How can the new version of the specification make radios boot faster and perform better for platforms at both ends of the spectrum regarding the size-weight-and-power (SWaP) characteristics.

This briefing will introduce a performance study that both NordiaSoft and Thales have launched together to investigate the latest release of the SCA specification. The study consists in a comparison of the performance metrics for several typical scenarios using both SCA version 2.2 and SCA version 4.1. The briefing will presents several metrics and offer a starting point for more discussion and further investigations. 

System and Architecture 1

Nina Machado Figueira - Captain - Ph.D. Computer Science, Brazilian Army Technological Center, "Software Defined Radio applied to Mission Oriented Sensors Array – A proposal to advanced  Embedded Systems architecture"  (paper)

The variety of Embedded Systems (manned and unmanned), sensors and waveforms available for communication, require the development of an architecture that facilitates the portability of sensorial processing applications (SPA). It is also desirable that this architecture enables the adaptability of the waveform and SPA according to the operating context. Thus, considering an embedded system with a Mission Oriented Sensors Array (MOSA) and transmitting data through an SDR, this will enable an architecture that  integrates the SPA with a control system of the SDR. One of the advantages of this standardization remains in the development and portability of adaptive systems, modifying the waveform and SPA to the operating conditions. The data channel features and the requested Quality of Service (QoS) are examples of operational conditions in the context of this work. One way to achieve this standardization is to use the SCA architecture in conjunction with the structure of a MOSA. Thus, an architecture integrating a MOSA with an SDR will be presented, both in an SCA environment, that promotes greater interoperability and portability of hardware and software. The introduction of this article presents the SDR Project of the Brazilian Ministry of Defense. Section 2 presents MOSA within an SCA architecture. Section 3 describes the interaction of MOSA with SDR (SCA). Section 4 presents a case study involving MOSA and SDR in defense application. Section 5 presents the final considerations.

Gunjan Verma, US Army Research Labs, Fikadu Dagefu, Army Research Labs, USA, Predrag Spasojevic, Rutgers University, USA, Brian Sadler, Army Research Labs, USA "Effect of coarse frequency synchrony on spread spectrum codes having a zero correlation zone"

In direct sequence code division multiple access (DS-CDMA), the choice of spreading code determines most relevant properties of the resulting communications system. Classical spreading codes (like Gold codes) have non-zero cross-correlations, giving rise to multiple access interference (MAI) and, in the case of power mismatch, the near-far problem. In conventional multiuser communications scenarios (e.g. cellular), there is thus a reliance on tight synchronization (time and power) in order to minimize the effect of MAI. However, in infrastructure-poor, rapid-deployment scenarios relevant to Army applications, alternative coding schemes are desirable for robust multiuser communications.

A promising avenue towards reducing such synchronization requirements is the use of loosely synchronous (LS) codes to enable quasi-synchronous(QS) multicarrier (MC) DS CDMA. Such a scheme has two principal advantages. One, these codes are characterized by a zero cross-correlation zone (ZCZ), a measure of the extent to which two nodes can be unsynchronized in time but still retain perfect code orthogonality. Loosening the time synchronization requirement reduces hardware and coordination costs, while perfect orthogonality eliminates, in principle, MAI and thus the need for power control. Two, the use of multiple carriers extends the time duration of the ZCZ, thereby further relaxing the time synchronization requirement in proportion to the number of subcarriers. Such ideas have been advanced in the literature.

However, frequency offset between nodes destroys perfect code orthogonality, a problem worsened when using multiple carriers. In reality, a node that is coarsely time synchronized will also be coarsely frequency synchronized, so the presence of frequency offset in LS codes is a legitimate practical concern that has received comparatively little attention.

A well-known (and nearly optimal, in the sense of the number of spreading codes generated) construction technique for a code family with a ZCZ is based on the concatenation of several constituent complementary sequences and their mates each of which is multiplied by the entries of a Hadamard matrix. This procedure gives rise to a large number of ZCZ code families, each family parameterized by a choice of the complementary sequence pair and Hadamard matrix used. While the resulting code families have identical properties in time (e.g., the existence of a ZCZ over which ideal auto-correlation and cross-correlation properties hold), each has different performance with respect to frequency offset. In particular, some families are more sensitive to frequency-offset induced orthogonality loss than others.

In this work, we conduct a comprehensive numerical search over a large collection of ZCZ code families for a subset of manageable code sizes and characterize the worst-achievable and best-achievable performance in terms of frequency-offset induced orthogonality loss. We also implement these codes on software-defined radios (which have non-trivial frequency offsets) and use them for multiuser experiments in quasi-synchronous environments.

Ran Cheng, Li Zhou, Qi Tang, Yu Zhao, Shan Wang, Jibo Wei, National University of Defense Technology, China, "Can SCA 4.1 Replace STRS in Space Applications" (paper)

Software Defined Radio (SDR) has gained a great deal of attentions in both civil and military applications. As the most important SDR standard, Software Communications Architecture (SCA) has been accepted and extensively adopted in the development of radio systems since it was first released. Recently, implementing SDR in space environment has become an emerging issue. Due to the high-complexity and low-efficiency of CORBA, SCA 2.2.2 was found unable to well align with the mission requirements of Size, Weight and Power (SWaP) constrained platforms. In order to benefit from the SDR technology in space applications, a new standard, Space Telecommunications Radio System (STRS), was developed by NASA to avoid the drawbacks of SCA 2.2.2. However, SCA 4.1, the latest release version of SCA, is envisioned to have the potential to be deployed in more constrained scenarios since CORBA is no more a necessity and a number of lightweight designs are adopted. Nonetheless, whether SCA 4.1 can meet the requirements of space applications is still an unsolved issue. In this paper, we focus on this problem and make a comparison between SCA 4.1 and STRS in two aspects, namely, the static memory occupation and dynamic transmission efficiency. The experiments are carried out on our space radio testbed by adjusting inter-components communication variables under different transfer mechanisms. In specific, inter-components communication variables cover the size of data packages, the amount of data and the number of components, etc. The transfer mechanisms include Message Queue and sharing memory, etc. In order to compare the performance of SCA 4.1 and STRS, we adopt four measurement indicators, i.e., memory occupation size, inter-components communication delay, waveform deployment delay and waveform switching delay.

In this paper, we have studied the feasibility and efficiency of SCA 4.1 in our space SDR testbed. Numerous experiments were carried out with independent variables mentioned above using a control variate method. We think this work has filled the blank of performance comparison between SCA 4.1 and STRS in space applications. In the future presentation, we will show some interesting results and detail that whether SCA 4.1 is an efficient substitute of STRS in space environment.

Ran Cheng, Yu Zhao, Li Zhou, Qi Tang, Dongtang Ma, Shan Wang, Jibo Wei, National University of Defense Technology, China, "Investigation of High-Efficient Transfer Mechanisms for SCA 4.1" (paper)

As a defacto Software Defined Radio (SDR) standard, SCA is rapidly advancing in recent years in terms of scalability, flexibility, extensibility and adaptability. CORBA is widely adopted in former SCA standards to improve portability and interoperability. However, the latest version, SCA 4.1, eliminates the dependence on CORBA by introducing the concept of transfer mechanism. SCA 4.1 does not prohibit the usage of CORBA, meanwhile, it enables to use reconfigurable transfer mechanisms with common APIs, thus providing more flexibility. With the reconfigurable feature, SCA 4.1 is expected to have better performance in the size, weight and power (SWaP) constrained conditions. In this paper, we introduce a reconfigurable transfer framework and investigates the performance among different transfer mechanisms.

Middleware, a special transfer mechanism, is the encapsulation of low-level transfer functions and services, and is mainly applied in distributed platforms. However, in a single node radio, such as a handheld device, middleware based inter-component communication is not necessary and low-level POSIX transfer functions supported by the operating system might be more efficient. Therefore, there are two questions here: 1) which middleware matches SCA 4.1 the best? 2) What is the performance difference between a middleware and an unencapsulated low-level POSIX transfer function? To answer the first question, we conduct the performance comparison among OmniORB, Andriod RPC and ZeroMQ, which are the typical middleware of Object Request Broker (ORB), Remote Procedure Call (RPC) and Message-Oriented Middleware (MOM), respectively. Andriod RPC is a lightweight middleware developed by Andriod Interface Definition Language (AIDL). ZeroMQ is a concurrency framework which integrates multiple transport modes. In addition, we consider the performance of TAO as a benchmark in our experiments. For the second question, we compare the performance of a middleware and the low-level POSIX transfer functions, including message queue and socket. 

The contribution of this paper is summarized as follows. Firstly, we compare the efficiency of four typical middleware in the framework of SCA 4.1, namely, TAO, OmniORB, Andriod RPC and ZeroMQ. Secondly, we find that the encapsulation of low-level transfer mechanisms in a middleware would result in loss of efficiency. In the end, we propose a self-defined transfer mechanism by encapsulating low-level POSIX functions in standard APIs, which is demonstrated to be more efficient compared with other transfer techniques in our experiments.

Thursday, 18 May 2017

Opening Plenary

Heikki Kokkinen, FairSpectrum, "Europe moves towards Dynamic Spectrum Access" 

In Dynamic Spectrum Access (DSA), the utilization of radio spectrum is controlled by electronic means in contrast to static sharing, where the frequencies, time, and location of radio transmissions are set in radio licenses. the European Commission (EC), the European Telecommunications Standards Institute (ETSI), the European Conference of Postal and Telecommunications Administrations (CEPT), and national legislative and regulative bodies have worked on harmonised rules for DSA in Europe. Many European countries, including the UK, France, Italy, the Netherlands, Finland, and Russia have piloted DSA. This presentation discusses what has been learnt in the pilots, how the different DSA systems address the requirements in European spectrum sharing, and what could be expected in the future.

Fairspectrum provides commercial TVWS geolocation database service in the UK, and pre-LSA spectrum coordination service for 2.3 GHz wireless cameras in the Netherlands. Fairspectrum has participated in TVWS pilots in Finland and in the UK; in LSA pilots in Italy, Finland, and Russia; and in CBRS pilots in Finland. Fairspectrum contributes to 5G spectrum sharing in an EC Horizon 2020 project called Coherent and in the 5G Public Private Partnership (5G-PPP) spectrum group. Fairspectrum won the collaborative spectrum sharing award of the EC in the end of 2016. Fairspectrum is a member of ETSI, 3GPP, and Wireless Innovation Forum. In these activities Fairspectrum has gained a substantial understanding of DSA in Europe. 

In this presentation, we go through the lessons learnt in the DSA deployments and pilots, where we have been involved in. We take an objective view of TVWS, LSA, and CBRS system specifications, highlighting the differentiating features of each system. We present a few case studies consisting of specific European countries and frequency bands, which have potential for DSA use. We discuss DSA in 5G. We go through motivators and obstacles for DSA in Europe. We discuss how various stakeholders in a DSA system could maximize the benefit from it.

European organizations have put a lot effort into preparing for DSA. The pilots have tested system architecture, interoperability, maturity

of technology, interference protection criteria, involvement of different stakeholders, regulative, and legislative aspects. TVWS started DSA by tackling the terrestrial TV frequency band and developing a new device class, TVWS devices, with a global ambition. LSA was developed from the Mobile Network Operator (MNO) perspective for the European market. With a three-tier approach CBRS combines TVWS-type license exempt use and LSA-type operated networks primarily for mobile devices and networks on the US market. For the DSA industry, it would be beneficial to gain global adoption and as little band specificity as possible. Though in the short term, DSA deployments seem to be quite the opposite.

TBA, US DoD CIO, "USA Spectrum Strategy"

Spectrum Sharing 1

Spectrum Sharing 2 

Seppo Yrjola, Nokia, "Analysis of blockchain use cases in the CBRS spectrum sharing concept" 

The Blockchain (BC) technology has received religious attention in the financial and internet domains, and recently interest has spread to adjacent sectors like communications. This paper seeks to identify the impact of the BC technology in novel spectrum sharing concepts using the Citizens Broadband Radio Service (CBRS) concept as an example. This study discussed the implementation considerations of the CBRS spectrum sharing concept, and how the BC technology can be applied as a potential solution. We argue that the BC technology has potential to significantly reduce transaction costs in the spectrum sharing through automatization of business-to-business complex multi-step workflows in contracting, brokering and data exchange. It codifies and controls negotiation principles required in contracting like consensus, provenance, immutability and finality. Furthermore, flexibility and scalability introduced into regulation and spectrum management lower the entry barrier and enables new entrants to access local spectrum based on their specific business needs. The BC contribute to transition from administrative to market-based spectrum management. Results of our analysis shows that the automatization with cryptographic verifiability increase and build trust between key stakeholders and devices, which is essential trigger for any sharing concept. We believe that the integration of BCs in the spectrum management and control processes have potential to transform traditional mobile broadband ecosystem, bring in new players and impact future system designs. Increased system dynamics in spectrum sharing will introduce a need for near real time network management capabilities that could benefit of Internet of Things (IoT) type peer-to-peer (P2P) BC transactions of data, assets or services. Technology harmonization and integration with legacy in ecosystems will be essential to ensure economies of scale and fast time to market. Hybrid and private BC options will help in meeting the confidentiality requirements. This paper serves as a starting point for analyzing the applicability of the BC technology and its key characteristics around the CBRS. Future work is needed to dwell deeper into studying and validating the core characteristics of the BC for the key stakeholders and their particular use case requirements in the CBRS context. Potential deployment considerations in the CBRS context calls for focused research in the areas of legal enforceability, transactional confidentiality, and consensus mechanism determination. The successful deployment of the BC technologies has potential to significantly improve the efficiency of the dynamic spectrum sharing concepts, influence the regulatory and management approaches of spectrum and create new business opportunities. This calls for a collaborative effort from the government, industry and academia to build and validate dynamic capabilities and technology enablers needed.

Zhuoran Cai, China Shandong Institute of Aerospace Electronics Technology, "A New Spectrum Sensing Method Based on PSO-SVM" (paper)

In the cognitive radio system, spectrum sensing for detecting the presence of primary users in a licensed spectrum is a fundamental problem. Energy detection is the most popular spectrum sensing scheme used to differentiate the case where the primary user’s signal is present from the case where there is only noise. In fact, the nature of spectrum sensing can be taken as a binary classification problem, and energy detection is a linear classifier. If the signal-to-noise ratio (SNR) of the received signal is low, and the number of received signal samples for sensing is small, the binary classification problem is linearly inseparable. In this situation the performance of energy detection will decrease seriously. In this paper, a novel approach for obtaining a nonlinear threshold based on support vector machine with particle swarm optimization (PSO-SVM) to replace the linear threshold used in traditional energy detection is proposed. Simulations demonstrate that the performance of the proposed algorithm is much better than that of traditional energy detection.

Lee Pucker, Wireless Innovation Forum, "WInnForum CBRS Standards"

System and Architecture 2

Raul Torrego, IK4-IKERLAN, "Deterministic and cognitive wireless communication system with jamming-resistant capabilities for tactical or industrial communications" (paper)

This work presents a jamming-resistant and deterministic wireless communication system, which is intended to be used in tactical or industrial communications. These kind of applications require data communication to be bounded in the time and reliability domains, no matter which is the harshness of the environment or the presence of malicious interferences. In harsh propagation environments, communication systems suffer from severe signal degradation, including delay spread, deep fading and Doppler spread. Besides, they must also deal with other system’s interference and jammer attacks.

Unfortunately, traditional wireless communication systems are not able to overcome all these difficulties and, at the same time, fulfill with the aforementioned requirements. As a consequence, it is necessary to deploy new wireless communication systems like the one presented in this work, based on cognitive radio technology. The proposed wireless communication system, shown in Fig. 1, is based on a custom Orthogonal Frequency Division Multiplexing (OFDM) modem design which has been implemented on the programmable logic of a Xilinx Zynq Field Programmable Gate Array (FPGA). The modem is fully customizable, in case it is needed to add new features, and it is similar to the IEEE 802.11a/g physical layer standard. On top of this modem, a deterministic, real-time and cognitive Medium Access Control (MAC) layer has been implemented and evaluated. Based on a Time Division Multiple Access (TDMA) MAC, which ensures deterministic communications in the absence of interference, cognitive capabilities have been added. Unlike traditional cognitive radios, which are used in order to enhance spectrum utilization, the presented wireless communication system is able to detect interference (malicious or coming from other wireless communication systems) and switch the communication to an unoccupied and safe frequency band. Simulations in OPNET and measurements on real hardware have been carried out, which demonstrate the capability of the system to guarantee deterministic data delivery time even in the presence of interference.

A test setup has been prepared with the communication system configured with a frame length of 3.85 ms and a data lifetime of 30 ms. Besides, a jammer generating interferences has been added. In an scenario in which only the frequency the communication system is working is interfered, a single frequency hop is forced and a recovery time bounded between 8.5 and 12.5 ms is achieved. If both, the frequency in which the communication system is working and the one into the first hop is performed are interfered, thus forcing two frequency hops, the achieved recovery time is bounded between 20 and 23.7 ms. In both scenarios the 30 ms data lifetime is fulfilled.

Hassan El-Sallabi, Signal and Information Technology Corps, Qatar Armed Forces, "Reconfigurable Antenna based System for Spectrum Monitoring and Radio Direction Finding" (paper)

Existing spectrum monitoring and direction finding systems are based on conventional phased array antennas. These antenna elements have fixed antenna pattern and fixed operating frequency range. To extend the operating frequency range, the system may have different antenna sizes and spacing between antenna elements to cover different frequency bands. The antenna array geometry has a major role in accuracy of determining direction of arriving radio signals, whether it is 1D, 2D or 3D configuration. However, the new reconfigurable antenna technology offers a wide range of applications including spectrum monitoring and direction finding systems. Reconfigurable antenna has the capability to change its characteristics such radiation pattern, polarization and operating frequency by changing the path distribution of surface current. The distribution of current in an antenna and its geometry determines how the antenna radiates its energy into a radio channel, or how it receives radio frequency energy from it.

In this work, we present a proposal of spectrum and direction finding system based on reconfigurable antenna. The proposed system may have a vast range of applications in military and civilian commercial applications. The main advantage of the proposed system lies in providing lower complexity and smaller physical size compared to existing techniques based on phase difference between multiple antenna elements or systems based on mechanically rotating antenna. The proposed system is based on reconfigurable antenna that is configured for wideband scenario to monitor the spectrum. The system has database with known licensed operating frequencies. Once the system identifies a signal operates at frequency not in its database, the system configures the antenna to resonate at the detected unknown frequency. Then, the proposed system reconfigures its antennas to generate multiple directional antenna pattern states with multiple pointing directions that cover the azimuthal 360 degrees. The proposed system cycles the antenna pattern of wide beam width to determine coarse direction of signal arriving direction. The re-configurability of pointing direction of antenna patterns may also take place in polar plane to find elevation angle of direction of radio signal. These multiple pointing directions of antenna pattern states have a predefined reference to determine the direction of incoming signal through processing in signal processing unit of the system. Once the coarse direction is determined, then, the system moves to narrow beam width mode. The reconfigurable antenna is configured to narrow beam width with predefined pointing directions and starts cycling between them to cover the coarse angular range identified in previous stage. The system selects the most potential narrow beam widths that that have strongest received signal strength of arrived signals. The known pointing directions of narrow beam widths and weights of signal level of each narrow beam radiation pattern are used in estimate the direction of incoming signal. This can be used to estimate both azimuth and elevation of radio arriving direction.

Andre Puschmann, Paul Sutton, Ismael Gomez, Software Radio Systems, "Implementing NB-IoT in software radio - experiences using the srsLTE software radio tools"  (paper)

NB-IoT is the 3GPP standard for machine-to-machine communications, recently finalized within LTE release 13. This work presents an implementation of the NB-IoT standard, developed using the srsLTE software radio suite within the FP7 FLEX-IoT project. Since 2008, the FIRE (Future Internet Research and Experimentation) initiative has bridged the gap between visionary research and large-scale experimentation on new networking and service architectures and paradigms. The FLEX (FIRE LTE testbeds for open EXperimentation) project provides an open and operational LTE experimental facility based on a combination of configurable commercial equipment, configurable core network software, open-source components and sophisticated emulation and mobility functionalities. Under the FLEX-IoT project, SRS has integrated their high performance software radio UE (srsUE) as an extension to the FLEX testbed facilities and extended the FLEX testbed facilities to include the NB-IoT features of 3GPP LTE release 13 for LPWAN.

Antonis G. Gotsis, Konstantinos Maliatsos, Panagiotis Vasileiou, Stelios Stefanatos, Feron Technologies P.C., Marios Poulakis, Angeliki Alexiou, University of Piraeus, Department of Digital Systems (GREECE), "Experimenting with Flexible D2D Communications in Current and Future LTE networks: A D2D Radio Technology Primer & Software Modem Implementation" (paper)

Device-centric communications or simply D2D allow for two user equipment devices to communicate directly, hence allowing single-hop communication instead of the conventional two-hop cellular architecture, where the base station is always the one end of each communication pair. D2D communications is a disrupting paradigm in the cellular world, going hand-in-hand with 3GPP LTE evolution and 5G rise in the context of LTE-Advanced Pro and NR radio technologies. D2D in 3GPP has both an evolutionary flavor as it benefits the performance of existing services, by leveraging latency reduction and traffic offloading features, and a revolutionary flavor as it enables new applications, namely public safety, commercial social networking apps, and vehicle communications. The current work has a two-fold scope: to provide a comprehensive summary of the recent outcomes and ongoing activities around D2D support in 4G/5G, as well as present a D2D software modem implementation using the host-digitizer SDR model.

In the first part of the paper, we will provide a concise technology introduction to 3GPP D2D radio, as it has evolved from its first appearance in the 3GPP standard Release 12, to its enhancement in Release 13, and eventually to its V2X version planned to appear in the upcoming Release 14. In particular, we will focus on the two defined D2D operation modes: the “discovery” mode, where a D2D-enabled cellular handset (UE) announces its presence in the proximity area and/or monitors the presence of other proximal UEs by sending/blindly recovering short messages using a light (PHY-only) stack; the “communication” mode, where more data-hungry applications like VoIP/Video Streaming are supported, using a complete protocol stack. For each mode, we will present the key D2D radio technology challenges and aspects, including the related signals, channels and procedures. We will also cover the D2D-specific radio resources allocation introduced in the standard for managing intra-D2D and inter D2D-Cellular operation. Since D2D has been decided to operate within the underlying LTE network, efficient co-existence mechanisms should be defined in order to protect the traditional cellular UEs. Finally, we will provide basic link-level performance evaluation results based on our open (and first to the best of our knowledge) 3GPP D2D radio standard software implementation.

In the second part of the paper we will describe our developed D2D software modem prototype using SDR. To the best of our knowledge, this is the first attempt in realizing a standard-compliant 3GPP D2D software modem. The modem comprises: i) a transceiver implementation of the basic 3GPP D2D PHY and MAC functionalities running in GPP hosts; ii) an interface with a USRP board for signal transmission/reception. The software modem architecture will be described along with the detailing of the basic building blocks. An evaluation of the real-time capabilities of the prototype modem will be presented, based on extensive benchmarking carried out in various computational platforms. A demonstration of the software modem operation in a EU Future Internet Research Experimentation (FIRE) platform will be also performed. Potential extensions of the software modem in order to cater for the emerging V2X paradigm will be finally reported.

Acknowledgement: The research leading to these results has received funding from the European Union’s Seventh Framework Programme under grant agreement no 612050 (FLEX Project). The presented activities have been performed in the context of FLEX Open Call 2 Project “FLEX-D: Experimenting with Flexible D2D communications Over LTE”.