Multi-Carrier and Spread Spectrum Systems: From OFDM and MC ...

RF Issues 209above formula becomes( ) ( )dfcPath loss LOS = 32.4 + 20 log 10 + 20 logkm10 . (4.102)MHzThe noise power at the receiver input isP Noise = FN Thermal = FKTB (4.103)where F is the receiver noise factor, K is the Boltzmann constant (K = 1.38 × 10 −23 J/K),T is the temperature in Kelvin, and B is the total occupied Nyquist bandwidth. The noisepower is expressed in dBm. G Antenna is the sum of the transmit and receive antenna gainsexpressed in dBi. Offset is the margin for all uncertainties such as interference, shadowing,and fading margin reserve. Rx loss is the margin for all implementation uncertainties. C/Nis the carrier-to-noise power ratio to guarantee a given BER. The receiver sensitivitythreshold is given byRx th = P Noise + Rx loss + C/N. (4.104)In Table 4-10, an example of a link budget evaluation for using MC-TDMA in mobileindoor and outdoor communications is given. We consider for the base station transmitantenna a gain of about 16 dBi. However, for the terminal side, we consider an omnidirectionalantenna with 0 dBi gain. This table shows that about 25–27 dBm transmitTable 4-10Example of link budget evaluation for mobile and indoor communicationsParameters Mobile outdoor WLAN indoorcommunications communicationsCarrier frequency 2 GHz 5 GHzCoverage Macro cell (10 km) Pico cell (30 m)Path loss power, n 2.2 3Path loss 130 dB 112 dBIndoor penetration N/A 10 dBNoise factor 6dB 6dBBandwidth 2MHz 20 MHzBase station antenna gain (90 ◦ ) ∼ 16 dBi ∼ 16 dBiTerminal station antenna gain 0dBi 0dBiOffset ∼ 5dB ∼ 5dBC/N for coded QPSK (rate 1/2) 6dB 6dBReceiver sensitivity −94 dBm −84 dBmNeeded Tx power 25 dBm 27 dBm