Page 399 - Integrated Wireless Propagation Models
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T h e   l e e   C o m  p r e h e n s i v e   M  o d e l -  I n t e g r a t i o n   o f   t h e   T h r e e   l e e   M  o d e l s    377

               kind of losses will still be strong enough, and the noise floor must be kept as low as pos­
               sible. Therefore, we have to count all the noise sources, including the interference sources,
               as one kind of noise. Usually, the interference is much higher than the thermal noise.

                    .
               6.5.2 1    Thermal Noise-The thermal noise power is
                                             N  =  kTB watts                     (6.5.2.1)
                                                         l
               where k = Boltzmann's constant= -174 dBm/Hz at  7 °C, T = temperature in Kelvin, and
               B  b andwidth, in hertz.
                 =
               6.5.2.2  Transmitter and Receiver Noises
               The local oscillator phase noise, the AM-FM conversion noise in nonlinear devices, and the
               IM noise, which the intermodulation (IM) products, appear within the bandwidth region.
               6.5.2.3  Feeder Line Loss
               The waveguide or cables between the receiving antenna and the receiver front contrib­
               ute both signal attenuation and thermal noise.

               6.5.2.4  Atmosphere Loss
               A primary atmosphere loss is from rainfall. The more intense the rainfall and the higher
               the frequency, the more signal energy will be absorbed. Operating below 10 GHz, the
               loss can be negligible.

               6.5.2.5  Interference
               Interference can be considered as one kind of noise. Based on the interfered power linkg
               into the signal channel, the interference plus noise level would be used to compare with the
               received signal level. Usually, the interference level is much higher than the thermal noise in
               the cellular system due to the co-channel reuse scheme. The required signal-to-interference
               ratio can provide an error probability from transmitting a signal that meets our system
               requirement. The signal-to-interference ratio is a parameter to calculate the link budget. Sys­
               tem Interferences-System interference is formed by adjacent channel interference and co­
               channel interference. These types of interference can be predicted by the prediction model as
               long as the input data are complete and accurate. Those data will be found in Sec. 6.5.5.
               6.5.2.6  Antenna Efficiency and Gain
               Antenna efficiency is the ratio of its effective aperture to its physical aperture. The
               reduction of antenna efficiency is due to aperture tapering, aperture blockage, scatter­
               ing, re-radiation, spillover, edge diffraction, and dissipative loss. Antenna gain is the
               ratio of the maximum radiation intensity from the subject antenna to the radiation
               intensity from isotropic source with the same power input. The relationship between
               antenna effective aperture A e and antenna gain G is
                                              G = 4nAJA.2
               All of these items would be used to calculate the link budget.

               6.5.3  Received Signal Power and Noise Power
               The received signal power after a distance d is

                                              p   =  P, G,GmLo                   (6.5.3.1)
                                               r   A dY
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