Project SPECMORE

Abstract

SPECMORE project targets at effective use of the scarce frequency spectrum to enable an application which is strategic for the society. The application is broadband public safety and emergency communication service. It is considered vital to deploy such a service in the 400 MHz frequency band, in coexistence with legacy narrowband public safety and emergency services and civilian Professional Mobile Radio (PMR) applications. The new Broadband PMR system has to be designed in such a way that it does not cause interference to the incumbent ones.

While targeting at maximizing the efficiency of spectrum use, the considered coexistence scenario imposes challenging requirements at waveform design and practical RF circuit implementation levels. The existing OFDM based broadband wireless techniques are not suitable. To remove the interferences between the legacy narrowband and new broadband systems, high spectral containment of the transmitted waveform and related receiver processing are necessary. Furthermore, both systems use frequency-division duplexing (FDD) principle, and in the broadband case, the duplex distance gets too small to be handled by traditional techniques.

The main technical challenges to be addressed are related to maintaining the excellent spectral containment of available filter bank multicarrier waveforms with practical RF circuitry. For solving the duplexing issue, the project will use the so-called full-duplex RF approach, which consists of subtracting the transmitted signal, after proper amplitude weighting and phase alignment, from the simultaneously received signal. A mixed analogue-digital processing approach is required to implement this scheme effectively.

Furthermore, using the 400 MHz band together with advanced multi-antenna and relaying techniques makes it possible to build up the needed network coverage in an energy efficient manner with a low number of base stations.

Even though the focus is on the Broadband PMR system development, the results of the project are expected to find applications also in the commercial cellular system developments (3GPP and 5G) and they would also facilitate the practical implementation of the cognitive radio ideas.