Konstantinos Manolakis

Design aspects for 5G V2X physical layer

Next generation 5G communication systems will need to employ a range of diverse technologies in order to support vehicle-to-everything (V2X) use cases, ultimately leading to accident-free, cooperative autonomous vehicles that use the available roadway efficiently. V2X is considered as one of the most challenging applications of 5G, as it requires ultra-reliable and low-latency communication for safety-critical use cases and has to provide high data rates in many scenarios. This paper discusses design aspects for the radio access in 5G V2X. Selected key technologies and their integration towards future 5G V2X physical layer are addressed. We discuss channel modeling in the context of 5G V2X use cases and we present first results for frame structure and numerology design, coexistence with earlier systems, multi-link synchronization, and multi-antenna transmission techniques.

Low-latency synchronization for OFDM-based visible light communication

5G wireless systems are envisioned to provide ultra-high data rates, increased robustness and low latency for new applications such as machine-to-machine (M2M) and car-to-car (C2C) communications. This paper considers high-speed visible light communication (VLC) as a candidate serving technology to fulfill this set of requirements. Synchronization as the first step towards reliable data detection is studied here thoroughly aiming at high robustness and low complexity. Three schemes are reviewed, namely Schmidl-Cox and Park autocorrelation as well as a cross-correlation based approach, all using a predefined preamble. All schemes are examined concerning their robustness against multipath propagation and their precision in time estimation versus the preamble length. It is found that the simple Schmidl-Cox scheme, originally designed for complex-valued radio waveforms, can be applied also for real-valued optical wireless waveforms. Based on these investigations, an optimized preamble structure is finally proposed. Preamble boosting and fine synchronization can also be applied to reach a similar performance like optimal cross-correlation at reduced complexity. We study the fundamental trade-off between the preamble duration and the minimum signal-to-noise ratio (SNR) required for reliable synchronization and observe that ultra-low latency needs sufficient SNR.

Analysis of Synchronization Impairments for Cooperative Base Stations Using OFDM

Base station cooperation is envisioned as a key technology for future cellular networks, as it has the potential to eliminate intercell interference and to enhance spectral efficiency. To date, there is still lack of understanding of how imperfect carrier and sampling frequency synchronization between transmitters and receivers limit the potential gains and what the actual system requirements are. In this paper, OFDM signal model is established for multiuser multicellular networks, describing the joint effect of multiple carrier and sampling frequency offsets. It is shown that the impact of sampling offsets is much smaller than the impact of carrier frequency offsets. The model is extended to the downlink of base-coordinated networks and closed-form expressions are derived for the mean power of users’ self-signal, interuser, and intercarrier interference, whereas it is shown that interuser interference is the main source of degradation. The SIR is inverse to the base stations’ carrier frequency variance and to the square of time since the last precoder update, whereas it grows with the number of base stations and drops with the number of users. Through user selection, the derived SIR upper bound can be approached. Finally, system design recommendations for meeting synchronization requirements are provided.

Cooperative Cellular Networks: Overcoming the Effects of Real-World Impairments

The fifth generation (5G) of mobile communication systems will need to support new applications with a variety of requirements, including high data rates, low latency, improved reliability, and sup-port for a large number of devices. We believe that these demands can be satisfied by the combined use of additional spectrum at higher frequencies, small cells, a more advanced air interface, and spectrally efficient transmission using multiple antennas. Base station (BS) cooperation is an advanced multiantenna technique that has the potential to eliminate intercell interference and enhance spectral efficiency. But attaining effective BS cooperation is challenged by a number of real-world channel and synchronization impairments.

Fifth-Generation Technologies for the Connected Car: Capable Systems for Vehicle-to-Anything Communications

Two strong technology trends, one in the mobile communications industry and the other in the automotive industry, are becoming interwoven and will jointly provide new capabilities and functionality for upcoming intelligent transport systems (ITSs) and future driving. The automotive industry is on a path where vehicles are continuously becoming more aware of their environment due to the addition of various types of integrated sensors. At the same time, the amount of automation in vehicles increases, which, with some intermediate steps, will eventually culminate in fully automated driving without human intervention. Along this path, the amount of interactions rises, both in-between vehicles and between vehicles and other road users, and with an increasingly intelligent road infrastructure. As a consequence, the significance and reliance on capable communication systems for vehicleto-anything (V2X) communication is becoming a key asset that will enhance the performance of automated driving and increase further road traffic safety with combination of sensor-based technologies [1].

Sidelink-assisted handover for cellular network

Direct device-to-device (D2D) communication is considered as a key technology and enabler for a multitude of new services in future fifth generation (5G) networks. Especially safety and emergency applications will require fast and reliable handover, seamless D2D connectivity and proper radio access to the cellular network. This paper proposes a novel handover scheme, which takes advantage of the D2D sidelink in order to assist the handover procedure, provide connectivity and maintain synchronization among multiple radio links. The scheme is in particular beneficial for cases including users with partial cellular coverage, for which standard handover is not possible, provides connectivity to out-of-coverage users and further assists them in accessing again the cellular network. In a network-controlled implementation the proposed scheme can be used for flexible handover, allowing multi-link coexistence and avoiding large delays of inter-cellular D2D. Sequence diagrams and procedure flow charts are provided for selected scenarios.