, 2s + 1b, and Os + 2b. These are the states that use 5 or 6 units of resource, so there is room for a small call but not a big call. The blocking rate for big calls is the sum of the probabilities of the three black circles and the five gray circles because these are the states that will block a big call. If we have been directed to offer both small calls and big calls the same blocking rate, then this is not an efficient scenario. If the target blocking rate is fairly low, then the gray circles will have equilibrium probabilities at least as high as the black circles. In the general case with big calls b times bigger than small calls, a low blocking rate, and a resource large enough for several big calls, the blocking probability for big calls will be at least b times higher than the blocking probability for small calls. We can balance the service blocking rates between small calls and big calls by decid- ing to block all calls in any state where the physical system would block any calls. The dark circles in Fig. 23.5 are states where we are blocking both small calls and big calls even though the physical system has the resources to serve a small call in some of those states. This has the effect of raising the blocking rate for small calls, but it reduces the blocking for big calls without having to increase the resource. The same technique balancing service blocking rates is useful when there are more than two services. In fact, having a single condition for blocking calls is a natural thing to do in a CDMA system. The system can use some radio condition as a blocking criterion. For example, if the forward transmit amplifier power level exceeds some predetermined fraction of the total amplifier power, then the wireless system would be instructed to deny all new calls on that cell sector. Both low-rate voice calls and high-rate data calls would be de- nied service once the transmit power reaches this level. Users 2,111 Small Users Figure 23.5 State diagram for balanced service for two types of users. Downloaded