link has an estimated busy-hour message prediction based on our estimates and forecasts of activity. Consider the small example in Fig. 25.1. The network has 13 logical functions for three MSC regions in 4 physical locations: The upper-left location has MSC A, VLR A, and all three HLRs. The upper-right location has MSC B, VLRB, and all three MCs. The lower-left location has MSC C and VLR C. The lower-right location has the SCP database. Thus there are 6 possible paths connecting pairs of physical locations. MSC/VLR/HLR MSC/VLR/MC A A ABC B B ABC MSC/VLR Database Figure 25.1 A simple multi-MSC wireless network. 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. ANSI-41 Signaling Capacity ANSI-41 Signaling Capacity MSC VLR HLR MSC VLR MC A A ABC B B ABC Network Database Figure 25.2 Starting to engineer a simple multi-MSC network. Suppose that we have done the forecasting and calculating so that we have specific ANSI-41 load projections for handoff, roaming, call processing, and SMS. For each pair of logical functions, we have a load estimate, so we can add up the total expected ANSI- 41 signaling traffic for each of the six point-to-point paths. From there, we can engineer a network. In Fig. 25.2 we have the first steps toward capacity engineering for the ANSI-41 net- work. We have dual A-links to an SS7 network cloud from all four physical locations plus a dedicated fully associated (F) link connecting the location with all three HLRs to the location with all three MCs. The next step is to analyze the SS7 network to make sure that it can handle the traf- fic this network is going to put on it. An operating requirement of SS7 is to have no link more than 40 percent occupied. In this way, the packet network has a comfortable mar- gin even if one of the dual transport links fails. 25.7 Conclusion Having laid out the principles of calculating capaci