1. Chapter 4 North American Intersystem Operations
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2. Architecture
TIA IS-41 (Telecommunications Industry Association Interim Standard 41)- an open communications interface between a pair of AMPS systems
IS-41.1-B: Functional Overview
IS-41.2-B: Intersystem Handoff
IS-41.3-B: Automatic Roaming
IS-41.4-B: Operations, Administration and Maintenance
IS-41.5-B: Data Communications
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6. Automatic Roaming Mobility Management Authentication Call Management
Mobility management procedures begin when a system detects the presence of a visiting terminal (refer to Figure 4.4).
Authentication
Authentication begins with a Qualification Request Invoke message initiated by the serving VLR (refer to Figure 4.4).
Call Management
Call management begins when someone dials the cellular phone number of the roaming subscriber (refer to Figure 4.5).
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9. Call Management The other conditions covered in Figure 4.6 are:
Delivery of call waiting service to a busy subscriber
Forwarding a call when the subscriber does not respond to an incoming call
Transmitting an announcement to the calling party when the subscriber does not respond
Unconditional call forwarding to another telephone number
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11. Intersystem Handoff The status of MSCs Handoff Categories Anchor MSC
Serving MSC
Candidate MAC
Target MAC
Handoff Categories
Handoff Forward
Handoff Back
Handoff to third
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16. Handoff Forward
The serving MSC sends Facilities Directive Invoke message to the target MSC.
If the target MSC accepts the handoff, it selects a channel to handle the call in the new cell and then sends Facilities Directive Result message to the serving MSC.
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18. Handoff Back
If the location phase results in a determination by the serving MSC that the call would best be handled in the system previously occupied by the terminal, the serving MSC initiates a handoff back procedure.
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20. Handoff to Third
Handoff to third is an example of a path minimization procedure, in which the system reduces the number of voice trunks carrying a call through three or more systems
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22. Status of IS-41 IS-41B (since 1991) IS-41C (since 1997) IS-136 (TDMA)
Is in wide-spread use in the USA and Canada.
IS-41C (since 1997)
For roaming calls to use the network operations defined in the TDMA and CDMA.
IS-136 (TDMA)
IS-95 (CDMA)
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Peter Yeh

23. Review Exercises
Why is a cellular phone capable of operating with more than one telephone number?
During a phone call, explain the conditions that cause a mobile switching center to perform each of the following functions:
Anchor MSC, Serving MSC, Candidate MAC and Target MSC
Why does IS-41 specify three different handoff procedures?
2018/9/22
Peter Yeh