InterMSC Handover » History » Version 3
laforge, 10/02/2018 06:50 PM
1 | 1 | laforge | h1. InterMSC Handover |
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3 | {{>toc}} |
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5 | *NOTE: This page doesn't describe an existing feature in OsmoMSC. Rather, it describes the general nature of a 3GPP feature which we plan to support at some time* |
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6 | 2 | laforge | |
7 | 3 | laforge | An Inter-MSC hand-over occurs if a subscriber with an active/ongoing call moves between two cells that are served by different MSCs. Each MSC serves a number of BSCs which in turn serve a number of BTS. The geographic area served by one MSC is considered the "MSC coverage area". Inter-MSC hand-over hence happens at mobility of subscribers between MSC coverage areas. |
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9 | From the MSC point of view, this involves transactions on both the A interface (towards the BSCs) as well as the E interface (towards other MSCs). |
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11 | As inter-MSC happens between different MSCs, a MSC can assume different roles in such a hand-over scenario: |
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13 | # The initial MSC which is serving the subscriber before any inter-MSC hand-over occurs. It is called *MSC A* in the relevant specs |
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14 | # The first MSC to which the call/subscriber is first handed over (so-called _basic Inter-MSC hand-over_). It is generally called *MSC B* in the relevant specs. |
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15 | # Any subsequent MSC to which the call/subscriber is handed over (so-called _subsequent Inter-MSC hand-over_). It is called *MSC B'* in the reelvant specs. |
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17 | *MSC A* is the anchor MSC which was serving the subscriber/call before the first hand-over. It continues to handle the Layer3 messages such as CC and MM from the MS, even after any number of hand-overs. Also, it continues to handle the termination of the voice call towards the PSTN (via MNCC in OsmoMSC). Any other MSC which may currently be serving the subscriber after a successful inter-MSC hand-over merely acts as a proxy for the BSSMAP messages, as well as for the voice communication. |
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20 | 2 | laforge | h2. Relevant specs |
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22 | * TS 23.009 -- Handover Procedures with ladder diagrams and tons of SDL diagrams |
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23 | * TS 29.002 -- MAP message encoding; can be used as guidance when specifying GSUP equivalent |
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24 | * TS 48.008 -- A[oIP] interface protocols BSSAP/BSSMAP |
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25 | * TS 29.010 -- Interworking betwen A (BSSAP) and E (MAP) interface |
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26 | * TS 49.008 -- BSSAP features supported during/after Inter-MSC HO |
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27 | * TS 23.284 -- LCLS implications of Inter-MSC HO |
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28 | * Misc: TS 24.237, TS 23.237, TS 23.231 |