无线通信系统第三章.pptVIP

Mobile Radio Propagation:Large-Scale Path Loss;;;Spectrum;Frequencies for mobile communication;Free Space Propagation Model;EIRPERP;;Path Loss;The far-field region of a transmitting antenna;The Reference Distance;Log-distance path loss model;If a transmitter produces power:Pt=50w, receive sensitivity (minimum usable signal level)is -100dbm.Assume d0=100m, with a 900MHz carrier frequency, n=4,Gt=Gr=1; find the coverage distance d. Transmit Power: Pt=50W=47dBm Pr(d0)=-24.5dBm PL(dB)=40log(d/d0)=-24.5-(-100)=75.5dbm If n=4,log(d/d0)=75.5/40=1.8875,d=7718m;Log-normal Shadowing;Simulation Results;Log-normal Shadowing ;Determination of Percentage of Coverage Area ; as a function of probability of signal above threshold on the cell boundary. ;Example Four received power measurements were taken at distances of 100 m, 200 m, 1 km, and 3 km from a transmitter. These measured values are given in the following table. It is assumed that the path loss for these measurements follows the model in Equation (3.12.a), where d0 = 100 m: (a) find the minimum mean square error (MMSE) estimate for the path loss exponent, n; (b) calculate the standard deviation about the mean value; (c) estimate the received power at d = 2 km using the resulting model; (d) predict the likelihood that the received signal level at 2 km will be greater than -60 dBm; and (e) predict the percentage of area within a 2 km radius cell that receives signals greater than -60 dBm, given the result in (d). ;The value of n which minimizes the mean square error can be obtained by equating the derivative of J(n) to zero, and then solving for n. (a)Using Equation (3.11), we find = pi(d0)-10nlog(di/ 100 m). Recognizing that P(d0) = 0 dBm, we find the following estimates for p, in dBm: ? ;(b)The sample variance o2 = J(n)/4 at n = 4.4 can be obtained as follows. ? ; (c)The estimate of the received power at d = 2 km is (d)The probability that the received signal level will be greater than -60 dBm is (e)67.4% of the users