5GNOW: Intermediate Transceiver and Frame Structure Concepts and Results Thorsten Wild 1 , Gerhard Wunder 2 , Frank Schaich 1 , Yejian Chen 1 , Martin Kasparick 2 , Marcin Dryjanski 3 , Slawomir Pietrzyk 3 , Nicola Michailow 4 , Maximilian Matthé 4 , Ivan Gaspar 4 , Ainoa Navarro 4 , Luciano Mendes 4 , Andreas Festag 4 , Gerhard Fettweis 4 , Jean-Baptiste Doré 5 , Nicolas Cassiau 5 , Dimitri Kténas 5 , Vincent Berg 5 , Bertalan Eged 6 , Peter Vago 6 1 Alcatel Lucent Bell Labs, Stuttgart, Germany, {firstname.lastname}@alcatel-lucent.com 2 Fraunhofer Heinrich Hertz Institute (HHI), Berlin, Germany, {firstname.lastname}@hhi.fraunhofer.com 3 IS-Wireless, Warsaw, Poland, {first_letter.lastname}@is-wireless.com 4 Vodafone Chair, TU Dresden, Germany, {firstname.lastname}@if.et.tu-dresden.de 5 CEA-Leti, Minatec Campus, Grenoble, France, {firstname.lastname}@cea.fr 6 National Instruments, Budapest Hungary, {firstname.lastname}@ni.com Abstract—This paper provides intermediate transceiver and frame structure concepts and corresponding results for the European FP7 research project 5GNOW. The Unified Frame Structure concept is presented which supports an integrated 5G air interface, capable of dealing both with broadband data services and small packet services within the same band. Waveforms which tolerate higher levels of robustness, e.g. w.r.t. time-frequency misalignment than OFDM are required. In this paper encouraging candidate waveform technologies are presented and discussed with respective results. This goes along with modern multiple access technologies using multi-layered signals and advanced multi-user receivers. Furthermore, random access strategies are discussed, as well as 5GNOW networking interfaces. The intermediate results of 5GNOW lay the ground for designing a new 5G air interface beyond LTE-A, which suits the diverse needs of future applications, like machine-type- communication (MTC). Keywords—5G, waveforms, air interface, frame structure, OFDM, FBMC, UFMC, GFDM, non-orthogonal, asynchronous I. INTRODUCTION The advent of the Internet of Things (IoT) and its integration with human-initiated transmissions such as 3D video streaming etc. poses new challenges to next generation wireless air interfaces. The former demands supporting a large number of nodes under the premises of low cost and life time (e.g. greater than 10 years) with particular traffic characteristics, e.g. sporadic transmissions; the latter demands Gigabit Wireless connectivity. In addition, visions like the Tactile Internet require a support of very low latencies. The main paradigm of the 5GNOW project is that the underlying design principles –synchronism and orthogonality– of the PHY layer of today’s LTE-A radio access network constitute a major obstacle for this envisioned service architecture [1]. This paper provides a summary of intermediate 5G results, leading to the intermediate 5GNOW transceiver and frame structure concept, which is able to address the wide range of application scenarios having to be supported in future wireless systems. II. 5GNOW UNIFIED FRAME STRUCTURE Fig. 1 depicts the Unified Frame Structure Concept [1], aiming at handling the very heterogeneous service and device classes within one wireless access frame structure. High-volume broadband traffic (Type I) will operate as in LTE-A with synchronicity, whenever possible, using scheduled access. At cell edges, with coordinated multi-point transmission and reception (CoMP), it is not always possible to establish synchronicity to all cells, so the system has to operate with relaxed synchronicity requirements (Type II traffic). For sporadic, small packet services, as occurring in MTC, a general relaxation of time-frequency alignment reduces signaling overhead and battery consumption (Type III traffic). Multiple signal layers may superimpose, which is handled by advanced multi-user / multi-cell receivers. For low-end sensor devices, it may be helpful to spread the transmission over a longer time and to allow completely asynchronous transmission (Type IV) traffic. The unified frame concept shall be main part of the standardization processes to be initiated in the future. III. 5GNOW WAVEFORM AND MULTIPLE ACCESSS APPROACHES The widely adopted OFDM waveform, used in 4G systems has high spectral side lobe levels, due to rectangular symbol shapes in time. This results in a high sensitivity to time- frequency misalignment. In 5G systems, in order to support the Unified Frame Structure concept, new waveform alternatives are required [1]. With waveforms which are robust against Type I Type II Layer Time Type III and Type IV Frequency Fig. 1. Unified Frame Structure