n, and extra power for each call. If a subscriber is combining voice and data in one session, then there is only one pilot for both. The overhead in the reverse direction is the pilot plus any signaling activity. The effect of the reverse overhead is to reduce the value of a. This reduction is not a fixed amount because the pilot is a bigger share of a voice channel than of a high- capacity data channel. In fact, the effect of overhead is a fixed increase in 1/a. This is so because 1/a is the share of the total CDMA resource that a channel uses, and adding a fixed overhead will increase that share the same amount for different channels. 28.4.2 Soft and softer handoffs The reverse soft handoff has no effect on the CDMA equations. It ensures that each user terminal is operating at the lowest power for several radio paths. We can think of reverse soft handoff as the process ensuring that the equations hold true. If the user terminal has to make a sequence of hard handoffs to maintain the highest radio signal path gain, then delays and inaccuracies in the handoff process will degrade the capac- ity from the equation solution. 9We have already accounted for power control, both forward and reverse, in Sec. 28.2.2. 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 Softer handoff, on the other hand, actually may improve the capacity beyond the equation values because the combination of two sector signals may allow lower power levels. We do not know if this combining effect of softer handoff is significant, but it is safe to say that soft and softer handoffs enforce the selection of the best cell sector in- stant by instant. 28.4.3 Joint detection (JD) JD as described in Sec. 10.4.7 is a mathematically sophisticated approach that uses knowledge of all the CDMA signals i