I. Guryanov, M. Bоgatyrev, P. Drychik, S. Pastukh, V. Pustovit, E. Shamaev, I. Fefilov

From the point of view of implementation, the range from 470 to 686 MHz [1,2] is currently considered the most attractive for broadband wireless access cognitive systems (BWA). The specified range is primarily intensively used in the digital television broadcasting systems (DTV). The following scenario of joint application of the BWA cognitive systems and DTV represents a practical interest. The base station (BS) of the BWA cognitive system is placed on one mast with the DTV transmitter to service the stationary subscriber stations (SS) at the range of up to 20 km. Thus the SS transceiver antennas are placed in close proximity to the DTV receiver antennas (in one building). Taking the specified scenario into account, the experimental studies of estimation of the technical possibility of joint functioning of the BWA and DTV cognitive systems are carried out applicably to two interference situations. In the first situation, the influence of unintentional interferences from the DVB-T DTV transmitter to the BS receiver was studied. A standard test program \"iPerf\" for the data transmission rate monitoring in WiMax radio channels was used in the research works. In the second situation, the influence of BWA SS transmitter emission to the DVB-T DTV receiver was studied. The assessment of influence was carried out according to ITU-R BT.1368-7 recommendations, at the useful signal level equal to minus 60 dBm at the DTV receiver input, for the following transmission channel types: Gauss, Rice and Reley. The following data were defined by the experimental studies: The maximum data rate from SS to BS (\"up\" line) as a function of the frequency diversion and the level unintentional interference from the DTV transmitter affecting the BS input. The maximum tolerable levels of an interfering signal at the DTV receiver input at which the bit error rate (BER) after the Viterbi decoder is below 2x104 in case of unintentional interference from the SS transmitter. The analysis of results of our calculations allows drawing the following summary concerning the joint operation 0 conditions of the BWA and DTV cognitive systems. 1. In all cases of joint operation of the BWA and DTV cognitive networks, the frequency spacing not less than 16 MHz (via the DTV channel) shall be provided. 2. In case of a \"critical\" mask for a range of signals of DTV and an additional decoupling of the antennas of DTV and BS transmitters not less than 30 dB, and also in case of an additional decoupling of the antennas of DTV receivers and the SS not less than 20 dB, the joint operation of such equipment is possible at acceptable antenna spacing (diversity of BS antennas - up to 50 m, and that of SS antennas - up to 3 m) in case of DTV transmitter capacity no more than 10 kW.