andoff activity whether the MSCs are on the same service provider's system or on two different wireless telephone systems next to each other. The signaling workload for handoffs is generated by the subscriber traffic at the bor- ders of MSC regions, as described in Sec. 34.5. It is the call activity in the border zone 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. Signaling Capacity Planning Planning for CDMA Capacity that determines how much inter-MSC signaling has to be done. The calls do not have to hand off to generate signaling messages. Once they get close enough, the serving MSC sends handoff measurement messages to any candidate MSCs for the serving base station. If the signal at the candidate MSC is good enough, then the MSCs coor- dinate a handoff using more ANSI-41 signaling messages. We want to know how much handoff traffic, or handoff candidate traffic, to expect. The best indication is to look at a 500-m-wide band (one-third of a mile) between MSC serving areas. Calls in this zone are likely to have good radio signals in each MSC area often enough to be generating handoff messages. If we get close to a triple-point where three MSC regions meet, then we expect a circle about 500 m across where all three MSCs are actively sending handoff messages for each call. Planning tools can help us refine the estimate of how much area is involved in hand- off activity. Not only might the activity band be wider or narrower than our 500-m es- timate, but local hot spots of high radio signal path gain can produce areas of inter- MSC handoff activity well inside an MSC service area. The signal reaching a base station served by a different MSC signal may never be strong enough for an actual handoff to take place, but the ANSI-41 signaling goes on as long as the radio path gain is high enough on different base stations served by different MSCS. 