Jae Cheol Park

Deployment and coverage of cognitive radio networks in TV white space

This article presents experimental and simulation results for the use of TV band devices (TVBDs) in TV white space, considering the presence of interference by incumbent services. Digital TV (DTV) services are major incumbent services currently operating in the TV bands. With DTV service, co-channel and adjacent channel deployment scenarios of TVBD networks are introduced. To safely protect the incumbent service, a minimum separation distance from the DTV protected contour, which is called the keep-out distance, is required. We estimate the keep-out distance for different ranges of TVBD transmit antenna height by using several propagation models and measurements of ultra-high-frequency signals in Korea. We also investigate the hidden node problem for the spectrum sensing operation mode of TVBDs. According to the results of these measurements, the hidden node margin should be at least 38 dB in order to protect DTV service. Finally, the service coverage reduction of TVBD networks caused by neighboring DTV service is discussed. It is shown that the service coverage of a wireless local area network system decreases about 50 percent by co-channel interference from neighboring DTV service when the field strength of the DTV received signal is 41 dBu.

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.

A design approach of radio frequency module for TV white space based on filter bank

This paper presents a design scheme of radio frequency (RF) module using filter bank in order to operate the overall TV broadcast band (470 MHz ~ 698 MHz). To this end, several band pass filters (BPFs) with a relatively sharp skirt characteristic are employed for compliance with TV white space (TVWS) regulations. Performance test results show that the error vector magnitude (EVM) of the implemented RF transmitting chain is less than 1.5 %. The noise figure (NF) of the RF receiving chain is measured to be 6.0 dB. From the results, the proposed RF module can be adequately utilized for TV white space applications.

Design scheme of a passive intermodulation distortion finder for common feeder cable in in-building

This paper presents the design scheme of a passive intermodulation distortion (PIMD) finder in order to find out the birthplace of PIMD which is introduced by sharing a feeder cable in in-building wireless multi-band networks. To this end, a frequency-modulated continuous-wave (FMCW) signal generation module and a fast Fourier transform (FFT)-based signal processing module are implemented to figure out the exact PIMD occurrence point. By improving the common feeder cable conditions with the timely PIMD detection, mobile consumer devices are expected to be well operated in in-building without call drop due to the PIMD.

Resource Allocation for Power Minimization in Multi-Band Wireless Networks

This paper designs a resource allocation to minimize the total transmit power of a multi-band wireless network under the required rate constraint. The required rate splitting scheme is proposed to reduce the computational complexity of the multi-band resource allocation. On the basis of the primal decomposition method, the multi-band resource allocation is decomposed into multiple sub-band resource allocations and the required rate splitting. Numerical results show that the performance gap between the proposed resource allocation and the optimal resource allocation is negligible. It is also observed that the proposed resource allocation provides better performances than the conventional resource allocation.

Power allocation for sum-rate maximization in multi-band wireless networks

This paper considers the optimal power allocation for a multi-band wireless network where links are partially sharing spectrum bands. In this scenario, the power allocation is proposed to maximize the instantaneous sum-rate of the wireless network. For the proposed power allocation, the optimal power allocation factor is derived. Numerical results show the validity of the proposed power allocation.