A new scheme for compliance with TV white space regulations using Wi-Fi modules in a cognitive radio system

This paper presents a cognitive radio system (CRS) that complies with the maximum allowable transmit power and emission limits of TV band devices (TVBDs). The CRS consists of a TVBD that uses the existing Wi-Fi module and two Wi-Fi modules operating in the 2.4 GHz and 5 GHz bands. Design methods are proposed for a radio frequency (RF) module, a digital signal processing (DSP) module, and a circuit for transmit-receive mode switching in the TV band device (TVBD). The performance of the implemented TVBD is investigated in both wired and wireless environments. The measured data rates of the implemented TVBD at the application layer are approximately 60 % of the theoretical data rates at the physical layer in the Wi-Fi system. The service coverage of a TVBD network is also measured according to several modulation and coding schemes (MCSs) of the TVBD for a single spatial stream. The coverage measurements of a TVBD network are conducted in both a suburban area, Jeju Island, and a nearly open area, Incheon, South Korea. The results show that the service coverage of a mobile network in TV white space (TVWS) can be enlarged by more than 2 km in the suburban area and by more than 8 km in the nearly open area.