Cognitive Radios for Spectrum Sharing: Technical Appendices

This is a technical appendix to the paper titled Cognitive Radios for Spectrum Sharing which will appear in the January issue of the IEEE Signal Processing Magazine. Due the severe space constraints the technical details had to be moved out of the paper and incorporated into this report. I. TECHNICAL DETAILS FOR FIGURE 1 To calculate the available white space we retrieved the FCC’s transmitter database which lists the latitude, longitude, effective radiated power (ERP) and transmitter height above sea level for all licensed transmitters [1]. This database together with the ITU-R recommendations on propagation (ITU-R P-1536-3) were used to calculate the protected radius for all towers. To calculate the value of of the no talk radius, we assumed a 4W cognitive radio with a height above average terrain (HAAT) of 75m. These assumptions are similar to the assumptions made by the IEEE 802.22 working group [2]. We assumed that the total white space was the total number of channels (67 channels – channel 2 to 69 excluding channel 37) times the area of the United States. The available white space was calculated as a percentage of the total white space. A. Calculating the protected radius Firstly, we assumed that all signals are ATSC signals i.e. the assumption is made that NTSC signals would switch to ATSC signals with the appropriate transmit power limits as shown in Table I. The required field strength (Erp(dBu)) for the Grade B (protected radius) contour is defined by the FCC for ATSC signals [3] as shown in Table II. For each transmitter we need to determine the distance value at which the received signal is above this specified level for 50% of the locations, 90% of the time. These numbers were calculated using the following procedure which is similar to the procedure used by the IEEE 802.22 Working Group: • The Effective Radiated Power (dBm) is converted to Effective Isotropic radiated Power (dBW) (EIRP (dBm) = ERP (dBm) + 2.15dB). • The Electric field at a distance of 1m from the transmitter is calculated as E1m(dBu) = 104.8 + EIRP (dBm). • The required path loss is calculated as RPL = E1m − Erp . • The ITU-R recommendations are used to determine the maximum distance (beyond 1m) at which the path loss is less than (or equal to) RPL for 50% of the locations, 90% of the time. (The ITU-R recommendations provide a mechanism to extrapolate the tables for different distances, heights and frequency [4]). For a 1MW TV transmitter on channel 38 with a HAAT of 500m the calculated protected radius is 135km. Channels Maximum Transmit Power (ERP) (kW) 2− 6 45 7− 13 160 14− 69 1000 TABLE I MAXIMUM TRANSMIT POWER FOR ATSC SIGNALS.