to CDMA Capacity Issues Specific to CDMA varies the rate in steps and makes full use of this rate reduction by broadcasting less power. This gives the carrier the immediate opportunity to handle more traffic on the same radio carrier. Conventional-reuse systems also benefit from suppressing transmission when the speaker is quiet, but the benefits are a statistical reduction in interference in another cell, an engineering opportunity in overall system design. The difference is that CDMA allows us to take advantage of speaker pauses moment by moment and to realize im- mediate capacity improvement. 30.6 Soft Blocking When a sector is unable to serve more traffic, we would like to overflow its traffic onto neighboring sectors. In Sec. 23.4 we saw how much more efficient a telephone network becomes with traffic overflow instead of blocking. In the small channel groups of wire- less telephone systems this traffic overflow is a very important positive capacity factor. The CDMA channel is not so cooperative. Having a call served on a nonoptimal sec- tor is actually worse for the optimal sector. The interference is actually more damaging to the nonserving sector than overloading it with the extra call. 2 Thus, once a sector's CDMA channel is full, its traffic has to be blocked rather than overflowed. There is some good news in the CDMA blocking picture. The capacity of a CDMA sec- tor depends on its neighbors, so there is a notion of the capacity of a community of CDMA sectors and cells. This notion of the CDMA carrier having a pliable upper limit is called soft blocking. This gives the CDMA channel some more latitude than the hard upper limit of the Erlang-B values in Table 23.1. There is another soft side to CDMA blocking. When a conventional-reuse sector is full, it is full. It is not like socks in the laundry bag, where we almost always can squeeze in just one more. However, a CDMA carrier will let us put one more call on it if we do not mind some deterioration of call quality. Thus a wireless carrier may decide to al