diff --git a/OsmoBTS/abis/rsl.adoc b/OsmoBTS/abis/rsl.adoc index c9bb555..ed8676e 100644 --- a/OsmoBTS/abis/rsl.adoc +++ b/OsmoBTS/abis/rsl.adoc @@ -350,12 +350,36 @@ non-acknowledged *RSL Delete Connection (DLCX) Indication* to the BSC. See <> -[[ipa_style_pdch_mgmt]] -=== IPA Style PDCH Management +[[rsl-dynamic-channels]] +=== Dynamic Channel Combinations -When using an IPA style dynamic TCH/F+PDCH channel type on an -on-air timeslot, there are a couple of non-standard RSL messages used -in order to activate or deactivate this timeslot in PDCH mode. +In the classic data model established by ETSI/3GPP for A-bis, each +timeslot (channel) is configured using a static channel combination by +means of A-bis OML. Particularly in presence of GPRS services, this +is very unflexible and leads to inefficient use of air interface +resources. + +As such, several methods have been implemented to overcome this +limitation. The fundamental operation can be outlined like this: + +* Configuration of a particular _dynamic_ channel combination via OML +* activation of TCH works like on a classic TCH channel combination +* activation of PDCH requires some specific PDCH activation procedure + +There are two variants implemented in the OsmoBTS A-bis dialect: + +[[ipa_style_pdch_mgmt]] +==== IPA Style Dynamic Channels + +This method is used when OML uses 'NM_CHANC_IPAC_TCHFull_PDCH' (0x80) +as channel combination for the given time-slot. + +'IPA style' refers to 'ip.access' compatible PDCH activation and deactivation. + +When the IPA style dynamic channel combination _TCH/F or PDCH_ +is set, the non-standard 'PDCH ACTIVATE' (<>) and 'PDCH +DEACTIVATE' (<>) procedures are used for switching an idle +channel into PDCH mode and back into idle mode. When the channel is used as TCH/F, regular circuit-switched activation is performed, like on any traditional TCH/F. However, the BSC must @@ -365,7 +389,7 @@ be deactivated using standard RSL signalling, before the specific PDCH related procedures are used to enable the PDCH. [[pdch_act]] -==== PDCH Activate +===== PDCH Activate This procedure is used by the BSC to request the BTS to activate an IPA style dynamic TCH/F+PDCH channel in PDCH mode. @@ -375,7 +399,7 @@ The operation is not supported on any other physical channel type. See <>, <>, <> [[pdch_deact]] -==== PDCH Deactivate +===== PDCH Deactivate This procedure is used by the BSC to request the BTS to deactivate an active PDCH on any an IPA style dynamic TCH/F+PDCH channel. @@ -384,6 +408,53 @@ The operation is not supported on any other physical channel type. See <>, <>, <> +===== IPA Style Dynamic Switchover Example + +.Example for dynamic channel switchover, for IPA style dynamic timeslots +["mscgen"] +---- +include::dyn_ts_ipa_style.msc[] +---- + + +[[OSMOCOM_DYN_TS]] +==== Osmocom Style Dynamic Channels + +This method is in use when OML uses +'NM_CHANC_OSMO_TCHFull_TCHHalf_PDCH' (0x90) for the given time-slot. + +The activation of PDCH is performed by using the regular 'RSL CHANNEL ACTIVATE' +procedure according to <>, with these modifications: + +* The 'C-bits' part of the 'Channel Number' IE take the non-standard binary + value 11000 (C5 thru C1 as seen in 3GPP TS 08.58 § 9.3.1). +* The 'A-bits' part of the 'Activation Type' IE take the non-standard binary + value 1111, with an additional fourth bit (add A4 to A3 thru A1 as seen in + 3GPP TS 08.58 § 9.3.3; all remaining reserved bits as well as the 'R' bit are + coded as zero). +* The normally mandatory 'Channel Mode' IE is omitted; none of the optional IEs + are included. + +Hence the message consists of exactly these IEs: + +.PDCH type _Channel Activation_ message IEs +[options="header",cols="10%,30%,60%"] +|=== +| TS 08.58 § | IE Name | Handling +| 9.1 | Message discriminator | Dedicated Channel Management +| 9.2 | Message type | CHANnel ACTIVation +| 9.3.1 | Channel number | 'C-bits' 11000, plus TS bits as usual +| 9.3.3 | Activation type | 'A-bits' 1111 +|=== + +===== Osmocom Style Dynamic Switchover Example + +.Example for dynamic channel switchover, for Osmocom style dynamic timeslots +["mscgen"] +---- +include::dyn_ts_osmocom_style.msc[] +---- + === Message Formats and Contents @@ -860,76 +931,3 @@ illustrated by the differences of <> and <>. Since the secondary TRX has no BCCH, it does not (need to) receive any 'RSL BCCH INFORMATION' messages from the BSC. -[[rsl-dynamic-channels]] -=== Dynamic Channel Combinations - -In the classic data model established by ETSI/3GPP for A-bis, each -timeslot (channel) is configured using a static channel combination by -means of A-bis OML. Particularly in presence of GPRS services, this -is very unflexible and leads to inefficient use of air interface -resources. - -As such, several methods have been implemented to overcome this -limitation. The fundamental operation can be outlined like this: - -* Configuration of a particular _dynamic_ channel combination via OML -* activation of TCH works like on a classic TCH channel combination -* activation of PDCH requires some specific PDCH activation procedure - -There are two variants implemented in the OsmoBTS A-bis dialect: - -==== IPA Style Dynamic Channels - -This method is used when OML uses 'NM_CHANC_IPAC_TCHFull_PDCH' (0x80) -as channel combination for the given time-slot. - -'IPA style' refers to 'ip.access' compatible PDCH activation and deactivation. - -When the IPA style dynamic channel combination _TCH/F or PDCH_ -is set, the non-standard 'PDCH ACTIVATE' (<>) and 'PDCH -DEACTIVATE' (<>) procedures are used for switching an idle -channel into PDCH mode and back into idle mode. - -.Example for dynamic channel switchover, for IPA style dynamic timeslots -["mscgen"] ----- -include::dyn_ts_ipa_style.msc[] ----- - -[[OSMOCOM_DYN_TS]] -==== Osmocom Style Dynamic Channels - -This method is in use when OML uses -'NM_CHANC_OSMO_TCHFull_TCHHalf_PDCH' (0x90) for the given time-slot. - -The activation of PDCH is performed by using the regular 'RSL CHANNEL ACTIVATE' -procedure according to <>, with these modifications: - -* The 'C-bits' part of the 'Channel Number' IE take the non-standard binary - value 11000 (C5 thru C1 as seen in 3GPP TS 08.58 § 9.3.1). -* The 'A-bits' part of the 'Activation Type' IE take the non-standard binary - value 1111, with an additional fourth bit (add A4 to A3 thru A1 as seen in - 3GPP TS 08.58 § 9.3.3; all remaining reserved bits as well as the 'R' bit are - coded as zero). -* The normally mandatory 'Channel Mode' IE is omitted; none of the optional IEs - are included. - -Hence the message consists of exactly these IEs: - -.PDCH type _Channel Activation_ message IEs -[options="header",cols="10%,30%,60%"] -|=== -| TS 08.58 § | IE Name | Handling -| 9.1 | Message discriminator | Dedicated Channel Management -| 9.2 | Message type | CHANnel ACTIVation -| 9.3.1 | Channel number | 'C-bits' 11000, plus TS bits as usual -| 9.3.3 | Activation type | 'A-bits' 1111 -|=== - -.Example for dynamic channel switchover, for Osmocom style dynamic timeslots -["mscgen"] ----- -include::dyn_ts_osmocom_style.msc[] ----- - -