 cellular system is to more or less maintain a cell boundary at the 39-dB u contour (Ref. 9). Note that 39 dBu = -95 dBm (based on a 50-S2 impedance at 850 MHz). Then at this contour, a mobile terminal would have a 24.16-dB fade margin. If a cellular transmitter has a 10-W output per channel and an antenna gain of 12 dBi and 2-dB line loss, the EIRP would be +20 dBW or +50 dBm. The maximum path loss to the 39-dBu contour would be +50 dBm - (-119.16 dBm) or 169 dB. 4Remember that a is the conventional notation for wavelength. F2 = 3 X 108m/s, where F is the frequency in Hz and a is the wavelength in meters. 5The 39-dBu contour is a threshold for good AMPS operation. CELLULAR AND PCS RADIO SYSTEMS 18.5 THE CELLULAR RADIO BANDWIDTH DILEMMA 18.5.1 Background and Objectives The present cellular radio bandwidth assignment in the 800- and 900-MHz bands cannot support the demand for cellular service, especially in urban areas in the United States and Canada. AMPS, widely used in North and South America and elsewhere, requires 30 kHz per voice channel. The system employs FDMA (frequency division multiple access), much like the FDMA/DAMA system described in Section 9.3.5.3. We remember that the analog voice channel is a nominal 4-kHz channel, and 30 kHz is about seven times that value. The trend is to convert cellular radio to a digital format. Digital transmission, as described in Chapter 6, is notoriously wasteful of bandwidth, when compared to the 4-kHz analog channel. We can show that conventional PCM requires 16 times more bandwidth than its 4-kHz analog channel counterpart. In other words, the standard PCM digital voice channel occupies 64 kHz (assuming 1 bit per hertz of bandwidth). Cellular system designers have taken two approaches to reduce the required bandwidth. First is to use voice compression on the digital voice channel. The second approach was to use more efficient access techniques. We briefly review several techniques of speech compression and then describe two distinctly different schemes for mobile sta