the system has a loss in efficiency, a reduction factor in a. If the power control is a statistically log- normal distribution with a standard deviation of 0.5 dB, then it reduces the CDMA ef- ficiency of each channel about 0.5 dB, about 10 percent. We can model this effect by multiplying a by 0.9. The power-control data stream can be punctured bits, a separate channel, or specif- ically allocated bits in the data stream. In any case, it is taking up CDMA channel space that is not subscriber voice or data. We can model this effect, too, as a multipli- cation factor in a. If a 7200-bit-per-second channel has 800 bits of power control, then we can multiply a by 0.9 to compensate. The tone of the last two paragraphs makes it sound like power control is bad news. This is not accurate. The bad news is the near-far problem and changing radio condi- tions. Power control makes it possible to run a CDMA system in a hostile radio envi- ronment, and these multiplication factors reflect the cost of the problem and its solution. 28.2.3 Smart antennas The effect of adaptive phased arrays, smart antennas, is to focus the two-way radio link on the user terminal being served. This is clearly a good thing that is not modeled di- rectly in the multicellular CDMA equations. The problem in the analysis is that there is a notion in the equations of a fixed collection of antenna faces, and we refer to the radio signal path gains Gub from user terminals U to antenna faces b. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. CDMA Principles for Multicellular Systems CDMA Principles for Multicellular Systems In a system with smart antennas, each user terminal has its own separate antenna radiation pattern used for both forward and reverse directions. If we wanted to be per- fectly complete, then we would have to generate a set of equations with a separate vir- tual ant