1. Lecture 5 Intersystem Operation

2. Basic AMPS Gives air interface between tower and mobile phone Does not provide capability to deliver roaming between different service providers –Why? Business arrangement between providers Validate the user

3. Initial solutions Clearing house database Special number (two numbers) system Call forwarding by forcing the user to punch special numbers whenever the user moves to new locations

4. IS-41 Telecommunications Industry Association (TIA) produced a Interim Standard 41. IS-41 is open air communications interface between a pair of service (AMPS) providers IS-41 is a seven layer protocol conforming to the OSI model –Layer 7 and layers 1 thro’ 4 are used

5. IS-41 reference model MSC PSTN VLR ACHLR ISDN EIR BS MSC CSS AC – Authentication center BS – Base Station CSS - User EIR – Equipment identity register HLR – Home location register ISDN – integ. services digital net MSC – mobile switching center PSTN – public switched tele. Net VLR – visitor location register

6. Elements of the model Two databases (VLR and HLR) Though we have functionally different elements, they may be in the same location Connection between two systems (or MSC) is established by two separate lines called –Voice trunks (transport of user info) –Data link (signaling)

7. Prior MSC Prior VLR HLRVLRMSC Base Registration of a user while visiting a new Base Reg. info store Reg. notification store Reg. notification Reg. Notification ack Reg. cancellation Reg. Cancellation ack Remove user

8. Prior MSC Prior VLR HLRVLRMSC Base Registration of a user while visiting a new Base Reg. cancellation Reg. Cancellation ack. Authenticate user Authentication info Remove user User profile? User profile info Store profile

9. Home MSC HLRVLRMSCBase Call Setup to a roaming subscriber User Receive Call AMPS call setup protocol Location request Route request Route info Location info Call setup request (use temp. phone #) Page command PAGE Detect MIN