Interference from low-duty cycle 26 GHz automotive Short Range Radar (SRR) : assessment of the effect of low-duty cycle operation on the interference from automotive Short Range Radar (SRR) on licensed Fixed Wireless services in the 24.25-26.65GHz band

Currently, there are two frequency bands allocated to Ultra-Wideband (UWB) automotive short range radar (SRR) equipment in Europe. In its Decision 2005/50/EC of 17 January 2005 [1] the European Commission (EC) designated the frequency band 21.65-26.65 GHz (referred to as the "24 GHz band") for use until mid 2013. The frequency band 77-81 GHz (the "79 GHz band") has been designated and made available for permanent usage by EC Decision 2004/545/EC of 8 July 2004 [2] In order to ease the transition from 24 GHz to 79 GHz technology the EC considers authorizing the use of a band in the 24 GHz range for SRR beyond 2013. In Report 37 of the European Conference of Postal and Telecommunications Administrations (CEPT) [3] which was prepared in response to the "SRR mandate 2" issued by the EC to the CEPT it is proposed to allocate the frequency band 24.25 - 27.50 GHz (the "26 GHz band") to SRR and reduce the risk of interference to licensed services operating in the same band through lower transmit power limits and low duty cycle (LDC) operation. As this proposal was not accepted the discussion now centres on the frequency band 24.25 - 26.65 GHz (the "revised 26 GHz band"). The objective of this report is to complement the very detailed and comprehensive compatibility studies that have been undertaken by CEPT, ITU-R, ETSI, and other institutions over the past years by evaluating the impact of LDC on the level of interference generated by automotive UWB SRR systems in the revised 26 GHz band. In particular, the impact on digitally modulated single carrier signals as used by licensed microwave fixed wireless links is investigated. The conclusions drawn in this report will hopefully be useful for defining the future regulation for automotive SRR in the European Union.