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messages.txt

dexter, 01/08/2018 08:33 PM

 
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Series of minimal messages exchanged bitween BSC1, BSC2 and MSC.
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================================================================
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HANDOVER REQUIRED (BSC1->MSC, 3.2.1.9)
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(Source BSC asks to handover a subscriber)
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	 Cause						Tell the reason why we want to handover
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	 Cell Identifier List (Preferred)		Tell to which cell(s) do we want to handover.
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	 Current Channyl Type 1				Tell which channel type we are currently using (e.g. 0001 = Voice)
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	 Old BSS to New BSS information			This is an optional field, but the spec says it should always be include, what do we put in here?
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	 Speech version (used)				Tell which speech version we are currently using (see also ASSIGNMENT COMPLETE msg)
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	 AoIP: Speech Codec (used)			Tell which codec we are currently using (see also ASSIGNMENT COMPLETE msg)
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HANDOVER REQUEST (MSC->BSC2, 3.2.1.8)
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(MSC asks the target BSC for to take handover, much like ASSIGNMENT REQUEST)
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	 Channel Type					(see also ASSIGNMENT COMPLETE msg)
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	 Encryption Information				Tell the session key and the algorithm (but why is there a field "supported algorithms"? it can only one algo/one key!?)
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	 Classmark Information 1			Tell clasmark information?
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	 Classmark Information 2			Tell clasmark information?
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	 Cell Identifier (Serving)			Tell which cell is currently serving the subscriber (How are we supposed to know that?)
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	 Cell Identifier (Target)			Tell the cell that the MSC has decided for
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	 AoIP Transport Layer Address (MGW)		Tell where the target BSC should send its RTP stream
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	 Codec List (MSC Preferred)   			Tell which codecs we prefer
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	 Current Channel type 1				Tell channel type (same as in HANDOVER REQUIRED)
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HANDOVER REQUEST ACKNOWLEDGE (BSC2->MSC, 3.2.1.10)
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(Other BSC acknowledges the handover, much like ASSIGNMENT COMPLETE
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	 Layer 3 Information				DTAP (RR) message to assign a new channel on the new BSC/Cell?
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	 AoIP Transport Layer Address (BSS)     	Tell where the MSC side should send its RTP stream (MGW on the BSC2 side)
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	 Codec List (BSS Supported)   	    		Tell which codecs the BSS supports (mandatory for AoIP, but probably not that important for us at the moment?)
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	 Speech Version (Chosen)			(See ASSIGNMENT COMPLETE)
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	 Speech Codec (Chosen)				(See ASSIGNMENT COMPLETE)
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HANDOVER COMMAND (MSC->BSC1, 3.2.1.11)
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(Make the MS transitioning to the new cell)
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	 Layer 3 Information				DTAP (RR) message to assign a new channel on the new BSC/Cell?
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HANDOVER DETECT (3.2.1.40)
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(MS got detected by the new cell and is in transition)
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	 (no elements)
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HANDOVER COMPLETE (BSC1->MSC, 3.2.1.12)
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(MS transition is complete, maybe this is also a good location to perform the
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MDCX. Maybe its also a bit late until here. HANDOVER REQUEST ACKNOWLEDGE would
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also be a candidate)
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	 (no elements)
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CLEAR (MSC->BSC1)
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CLEAR COMPLETE (BSC1->MSC)
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