Search

In cyclic-prefix orthogonal frequency-division multiplexing (CP-OFDM) based radio access, the coexistence of different technologies without precise time-frequency synchronization is limited due to high out-of-band emissions. Therefore, spectrum enhancement techniques play a key role to relax the synchronization and power control requirements. This allows higher degree of opportunistic spectrum use with minimized interference. In addition, all transmitting devices have to fulfill specific transmitted signal quality requirements, including the maximum out-of-band radiated signal power. With OFDM based radio access, some additional signal processing for improved spectrum containment is commonly needed to achieve these requirements. Filtering and time-domain windowing are two fundamentally different approaches for spectrum enhancement. Filtered OFDM (F-OFDM) provides better spectrum localization than the timewindowing schemes (such as windowed overlap-add, WOLA), with the cost of higher complexity. This paper introduces lowcomplexity solutions for spectrally enhanced narrow-band OFDM transmitters based on the use of a look-up tables (LUTs). The proposed LUT approach, requiring only memory units and a low number of additions, allows to avoid all computationally expensive operations in on-line transmitter processing, as it builds the transmitted signal by summing the stored partial waveforms optimized off-line. In certain cases, completely multiplication and summation free designs are possible. The transmitters of narrowband Internet of things (NB-IoT) devices are natural applications for the proposed LUT approach, as they require additional digital baseband signal processing to reach the emission requirements. It is shown that the proposed LUT schemes can provide signicant savings in real-time computations of NB-IoT devices, while fulfilling the 3GPP requirements. acceptedVersion

5th generation mobile networks will have to cope with a high degree of heterogeneity in terms of: services, mobility, number of devices, etc. Thus diverse and often contradicting key performance indicators need to be supported, but having multiple radio access technologies for multi-service support below 6GHz will be too costly. FANTASTIC-5G will develop a new multi-service Air Interface (AI) through a modular design. To allow the system to adapt to the anticipated heterogeneity, some properties need to be pursued, like: simplicity, flexibility, scalability, versatility, efficiency and future-proofness. Based on these properties a selected set of use cases and link and network design will be presented. The paper will also comprise validation and system level simulations through some indicative results; and will conclude with the overall impact to 5G standardization.

The advent of a new generation of wireless cellular communication networks (5G) is currently being discussed both in research and standardization, while 4G is continuously evolving. Within the overall 5GPPP framework, FANTASTIC-5G is the project dealing with the design of the multi-service air interface for below 6 GHz. Ultimate target of the project is to allow the system to adapt to any means arising from diverse service requirements and device capabilities, various deployment and environment settings and mobility levels. Additionally, the ambition of the project is to have an impact to standardization. Therefore, we focus on technologies being relevant for standardization instead of proprietary elements. This paper provides some insights on the project itself and on the concepts being worked on.

5G will have to cope with a high degree of heterogeneity in terms of services, device classes, deployment types, environments and mobility levels. Consequently, diverse and often contradicting Key Performance Indicators (KPIs) need to be supported, such as high capacity/user-rates, low latency, high reliability, ubiquitous coverage, high mobility, massive number of devices and low cost/energy consumption. 4G is not designed to meet such a high degree of heterogeneity efficiently. Moreover, having multiple radio access technologies for multi-service support below 6GHz will be too costly. FANTASTIC-5G is a European project which will develop a new multi-service Air Interface (AI) for below 6 GHz through a modular design. To allow the system to adapt to the anticipated heterogeneity, the pursued properties are: flexibility, scalability, versatility, efficiency and future-proofness. To this end, the project will develop the technical AI components and integrate them into an overall AI framework where adaptation to the above described sources of heterogeneity will be accomplished. The work will also comprise intense validation and system level simulations. The consortium possesses the main stakeholders for innovation and impacting standardization, maintaining Europe at the forefront.

This paper describes some of the outcome of the FP7 project PHYDYAS, whose main objective was to propose a new physical layer that will enable introduction of cognitive radios and dynamic access spectrum management. During the project both a software simulator and a demonstrator have been developed. A description of the demonstrator and some simulation results that show the differences in spectral efficiency and the sensititvity to synchronisation errors between OFDM and FBMC are given. The simulator, which is written in Matlab, was used to evaluate the performance of both OFDM and FBMC in a WiMAX context, i.e. the frame format is kept as close as possible to WiMAX. From the simulation results it has been possible to analyze the performance differences between the two systems. In addition to that the simulator was used as a reference in the validation of the demonstrator. The transmitter in the demonstrator is implemented in hardware and operates in real time. The channel emulation and up-conversion to RF is done using commercially available instruments from Agilent which have been modified to fit to the task. In the demonstrator receiver the hardware front-end converts the signal to baseband and digitizes it. The OFDM/FBMC signal processing is done in near real time on a general purpose computer connected to the front- end hardware.