Demonstrator of a scanning receiver subsystem for cognitive Professional Wireless Microphone Systems

Professional Wireless Microphone Systems (PWMS), transmitting voice and music in live events such as concerts or conferences, demand the highest level of sound quality and reliability. Dropouts, noise and interference have to be prevented at any moment of the transmission. At present, these requirements can be fulfilled as PWMS utilize locally unused TV channels and thus operate in a protected radio environment. However, in the near future, the "Digital Dividend" will open the spectrum to other users, leading to less spectrum allocation to PWMS. In order to maintain the high quality of service of the radio links, the Specialist Task Force STF386 on Cognitive Programme Making and Special Events (C-PMSE) of the European Telecommunications Standards Institute (ETSI) proposed a proactive cognitive approach. A major part of this proposition is a Scanning Receiver Subsystem (SCS) that monitors the current spectrum occupation according to which a Cognitive Engine can dynamically configure the radio links. The SCS is composed of multiple Scanning Receivers (SCR) that measure the spectrum occupation at different locations within an event site and one or more Scanning Receiver Controllers (SCC). The SCC combine these observations to determine positions of interferers and estimate their future locations as well as their impact on the microphone links. This paper reviews the current activities of ETSI for standardization of a cognitive wireless microphone system with an in depth focus on the scanning receiver subsystem. Furthermore, the hardware of a low-cost scanning receiver, which has been developed and tested at our institute, is presented. The proposed receiver architecture fulfills the spectrum sensing capabilities recommended by ETSI and can be built at an affordable price, allowing the described proactive cognitive radio system to be realized.