OsmoBTS/abis/rsl: combine separate dyn ts sections
There were two separate sections saying basically the same. Move the entire 'Dynamic Channel Combinations' section further above and combine with the 'IPA Style PDCH Management' section to avoid repetition. Change-Id: Ic370ba34de5cb14f0194ff8c8661e45d7ca98e2b
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Neels Hofmeyr
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6dc47a8dd9
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9b1cdce0f6
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@ -350,12 +350,36 @@ non-acknowledged *RSL Delete Connection (DLCX) Indication* to the BSC.
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See <<rsl_dlcx_ind_msg>>
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[[ipa_style_pdch_mgmt]]
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=== IPA Style PDCH Management
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[[rsl-dynamic-channels]]
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=== Dynamic Channel Combinations
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When using an IPA style dynamic TCH/F+PDCH channel type on an
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on-air timeslot, there are a couple of non-standard RSL messages used
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in order to activate or deactivate this timeslot in PDCH mode.
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In the classic data model established by ETSI/3GPP for A-bis, each
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timeslot (channel) is configured using a static channel combination by
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means of A-bis OML. Particularly in presence of GPRS services, this
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is very unflexible and leads to inefficient use of air interface
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resources.
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As such, several methods have been implemented to overcome this
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limitation. The fundamental operation can be outlined like this:
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* Configuration of a particular _dynamic_ channel combination via OML
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* activation of TCH works like on a classic TCH channel combination
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* activation of PDCH requires some specific PDCH activation procedure
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There are two variants implemented in the OsmoBTS A-bis dialect:
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[[ipa_style_pdch_mgmt]]
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==== IPA Style Dynamic Channels
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This method is used when OML uses 'NM_CHANC_IPAC_TCHFull_PDCH' (0x80)
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as channel combination for the given time-slot.
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'IPA style' refers to 'ip.access' compatible PDCH activation and deactivation.
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When the IPA style dynamic channel combination _TCH/F or PDCH_
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is set, the non-standard 'PDCH ACTIVATE' (<<pdch_act>>) and 'PDCH
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DEACTIVATE' (<<pdch_deact>>) procedures are used for switching an idle
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channel into PDCH mode and back into idle mode.
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When the channel is used as TCH/F, regular circuit-switched activation
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is performed, like on any traditional TCH/F. However, the BSC must
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@ -365,7 +389,7 @@ be deactivated using standard RSL signalling, before the specific PDCH
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related procedures are used to enable the PDCH.
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[[pdch_act]]
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==== PDCH Activate
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===== PDCH Activate
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This procedure is used by the BSC to request the BTS to activate an
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IPA style dynamic TCH/F+PDCH channel in PDCH mode.
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@ -375,7 +399,7 @@ The operation is not supported on any other physical channel type.
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See <<rsl_pdch_act>>, <<rsl_pdch_act_ack>>, <<rsl_pdch_act_nack>>
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[[pdch_deact]]
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==== PDCH Deactivate
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===== PDCH Deactivate
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This procedure is used by the BSC to request the BTS to deactivate an
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active PDCH on any an IPA style dynamic TCH/F+PDCH channel.
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@ -384,6 +408,53 @@ The operation is not supported on any other physical channel type.
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See <<rsl_pdch_deact>>, <<rsl_pdch_deact_ack>>, <<rsl_pdch_deact_nack>>
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===== IPA Style Dynamic Switchover Example
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.Example for dynamic channel switchover, for IPA style dynamic timeslots
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["mscgen"]
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----
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include::dyn_ts_ipa_style.msc[]
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----
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[[OSMOCOM_DYN_TS]]
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==== Osmocom Style Dynamic Channels
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This method is in use when OML uses
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'NM_CHANC_OSMO_TCHFull_TCHHalf_PDCH' (0x90) for the given time-slot.
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The activation of PDCH is performed by using the regular 'RSL CHANNEL ACTIVATE'
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procedure according to <<CHANNEL_ACTIVATION>>, with these modifications:
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* The 'C-bits' part of the 'Channel Number' IE take the non-standard binary
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value 11000 (C5 thru C1 as seen in 3GPP TS 08.58 § 9.3.1).
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* The 'A-bits' part of the 'Activation Type' IE take the non-standard binary
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value 1111, with an additional fourth bit (add A4 to A3 thru A1 as seen in
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3GPP TS 08.58 § 9.3.3; all remaining reserved bits as well as the 'R' bit are
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coded as zero).
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* The normally mandatory 'Channel Mode' IE is omitted; none of the optional IEs
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are included.
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Hence the message consists of exactly these IEs:
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.PDCH type _Channel Activation_ message IEs
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[options="header",cols="10%,30%,60%"]
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|===
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| TS 08.58 § | IE Name | Handling
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| 9.1 | Message discriminator | Dedicated Channel Management
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| 9.2 | Message type | CHANnel ACTIVation
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| 9.3.1 | Channel number | 'C-bits' 11000, plus TS bits as usual
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| 9.3.3 | Activation type | 'A-bits' 1111
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|===
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===== Osmocom Style Dynamic Switchover Example
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.Example for dynamic channel switchover, for Osmocom style dynamic timeslots
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["mscgen"]
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----
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include::dyn_ts_osmocom_style.msc[]
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----
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=== Message Formats and Contents
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@ -860,76 +931,3 @@ illustrated by the differences of <<rsl-msc-pri>> and <<rsl-msc-sec>>.
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Since the secondary TRX has no BCCH, it does not (need to) receive any 'RSL
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BCCH INFORMATION' messages from the BSC.
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[[rsl-dynamic-channels]]
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=== Dynamic Channel Combinations
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In the classic data model established by ETSI/3GPP for A-bis, each
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timeslot (channel) is configured using a static channel combination by
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means of A-bis OML. Particularly in presence of GPRS services, this
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is very unflexible and leads to inefficient use of air interface
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resources.
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As such, several methods have been implemented to overcome this
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limitation. The fundamental operation can be outlined like this:
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* Configuration of a particular _dynamic_ channel combination via OML
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* activation of TCH works like on a classic TCH channel combination
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* activation of PDCH requires some specific PDCH activation procedure
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There are two variants implemented in the OsmoBTS A-bis dialect:
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==== IPA Style Dynamic Channels
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This method is used when OML uses 'NM_CHANC_IPAC_TCHFull_PDCH' (0x80)
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as channel combination for the given time-slot.
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'IPA style' refers to 'ip.access' compatible PDCH activation and deactivation.
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When the IPA style dynamic channel combination _TCH/F or PDCH_
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is set, the non-standard 'PDCH ACTIVATE' (<<pdch_act>>) and 'PDCH
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DEACTIVATE' (<<pdch_deact>>) procedures are used for switching an idle
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channel into PDCH mode and back into idle mode.
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.Example for dynamic channel switchover, for IPA style dynamic timeslots
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["mscgen"]
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----
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include::dyn_ts_ipa_style.msc[]
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----
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[[OSMOCOM_DYN_TS]]
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==== Osmocom Style Dynamic Channels
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This method is in use when OML uses
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'NM_CHANC_OSMO_TCHFull_TCHHalf_PDCH' (0x90) for the given time-slot.
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The activation of PDCH is performed by using the regular 'RSL CHANNEL ACTIVATE'
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procedure according to <<CHANNEL_ACTIVATION>>, with these modifications:
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* The 'C-bits' part of the 'Channel Number' IE take the non-standard binary
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value 11000 (C5 thru C1 as seen in 3GPP TS 08.58 § 9.3.1).
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* The 'A-bits' part of the 'Activation Type' IE take the non-standard binary
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value 1111, with an additional fourth bit (add A4 to A3 thru A1 as seen in
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3GPP TS 08.58 § 9.3.3; all remaining reserved bits as well as the 'R' bit are
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coded as zero).
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* The normally mandatory 'Channel Mode' IE is omitted; none of the optional IEs
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are included.
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Hence the message consists of exactly these IEs:
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.PDCH type _Channel Activation_ message IEs
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[options="header",cols="10%,30%,60%"]
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|===
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| TS 08.58 § | IE Name | Handling
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| 9.1 | Message discriminator | Dedicated Channel Management
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| 9.2 | Message type | CHANnel ACTIVation
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| 9.3.1 | Channel number | 'C-bits' 11000, plus TS bits as usual
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| 9.3.3 | Activation type | 'A-bits' 1111
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|===
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.Example for dynamic channel switchover, for Osmocom style dynamic timeslots
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["mscgen"]
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----
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include::dyn_ts_osmocom_style.msc[]
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----
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