ll gel. One manageable element in optimizing CDMA cells is the distribution of carriers as- signed for DO versus those assigned to a mix of voice and data. This optimization is po- tentially quite complex. Here are two approaches worth exploring: Should allocation of DO carriers on a cell change with time of day? Perhaps more band- width should be given to DO services during business hours and more to voice in the evenings. It seems highly likely that certain cells, such as those which serve downtown business dis- tricts, will need more channels devoted to data capacity. What measurement tools, ana- lytic tools, and statistical tools are best for estimating the total demand for data capacity? These questions will need to be resolved in the coming years as demand for high speed wireless data services increases. Another variable that may be significant in overall system data capacity but which is not as easy to manage is the amount of capacity reserved for 1x channels that sup- port cdmaOne user terminals. These terminals operate at somewhat lower efficiency, especially on the reverse channel, which has a pilot in cdma2000 but is pilotless in cdmaOne. As described in Chap. 28, cdmaOne has no reverse pilot, which keeps its re- verse voice link simple, whereas 3G systems have a reverse pilot that makes them use the air interface more efficiently at the cost of extra complexity. When it comes to improving the air interface, changing the base stations is only half the story. Overall cell capacity and data capacity might be affected by the number of cdmaOne user terminals, versus the number of cdma2000 user terminals, active on a cell at a given time. 4 Some sources predict an increase in capacity by a factor of 1.5 to 2 when cdma2000 1x service replaces cdmaOne service as long as cdma2000 user ter- minals are used. It remains to be seen if these improvements actually appear in a frequency-limited real-world radio environment. If the improvements are real, then 4It is also possible that future 3G terminals will improve 