CUWLS

Coexistence of Ultra-Wideband and Licensed Systems

 Partecipanti

Mappa

 Word cloud

Esplora la "nuvola delle parole (Word Cloud) per avere un'idea di massima del progetto.

 Obiettivo del progetto (Objective)

'Most of the communication systems that are in use today are licensed systems. Due to the spectrum getting crowded with many licensed systems, there is a need to consider future communication systems different from the current licensed systems in use. Ultra-wideband (UWB) communications is one of them. In UWB communications, due to the very low power spectral density (PSD) of the transmitted signal, the UWB system can operate as an underlay system in the same frequency band. Despite the low PSD of such systems, the European and Japanese regulatory agencies have made the implementation of detect-and-avoid (DAA) techniques mandatory in some common bands so as to protect the license rights of the licensed users. Therefore, the challenge here is to implement the new UWB systems so that they can coexist with the licensed communication systems peacefully.

The main objective of this research is to investigate the coexistence of UWB systems with licensed systems. The research has two main parts; the implementations of detection and avoidance techniques considering practical scenarios. In the implementation of detection, the realistic case of active multiple systems with possible dependencies will be considered. This approach is different from the general approach that assumes the independence of the systems. In the implementation of avoidance, the linear combination of pulses with limited pulses will be considered as suggested by the IEEE 802.15.4a UWB standard. This approach is different from the general approach that assumes having enough number of pulses (i.e., filter coefficients). The main expected result of this research is to make suggestions for the coexistence of primary and secondary systems as a result of the considering the realistic cases. The research results are expected to provide benefit especially to the international communications research and development community and the European regulatory agency.'

Introduzione (Teaser)

Coexistence of licenced (i.e., primary) and secondary systems is a major standardisation issue as emerging communication systems may cause interference to existing ones and vice versa. An EU-funded project was dedicated to investigate coexistence solutions.

Descrizione progetto (Article)

The need to consider alternative communication systems is rising with the increasing number of licensed systems in the spectrum. Due to low power of transmitted signal, ultra-wideband (UWB) communications can operate as an unlicensed underlay system in the same frequency bands with licensed systems. Nevertheless, European and Japanese regulations require detect-and-avoid techniques in some common bands to protect the usage rights of licensed users.

The EU-funded project 'Coexistence of ultra-wideband and licensed systems' (CUWLS) investigated use of UWB with primary systems. They explored licensed system 'detection' to decide whether the common band is in use or not. In addition, they investigated 'avoidance' issues in case the licensed system is active most of the time.

The project sought to improve the UWB system ability to detect primary systems, assuming that primary systems are dependent. Instead of selecting the detection thresholds for each band individually as in conventional detection approaches, the bands were jointly processed. Maximum a posteriori decision variables were generated at the receiver, and bias terms were introduced to achieve trade-off between detection and false alarm probabilities. The gains were quantified in terms of the primary system interdependence and signal-to-noise ratio.

Regarding the avoidance part, CUWLS investigated various pulse shapes and modified the UWB transceiver. Primary systems were modelled as orthogonal frequency-division multiplexing (OFDM) wideband systems, where the effects of bandwidth and number of subcarriers were investigated for various pulses. Higher-order linearly combined pulses compensated better for system performance. Furthermore, the UWB bit-error rate performance was improved with increasing OFDM bandwidth and the UWB system exhibited better performance in the presence of an OFDM system with a large number of subcarriers in the low signal-to-interference ratio region. These results were important as the modified transceiver can achieve reasonable system performance while complying with the European regulatory agency mandates.

CUWLS addressed issues that are important for deploying wireless communication technologies in the future. Project results are therefore expected to have a positive impact.