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diff --git a/2021/osmodevcall-gsmr/osmodevcall-gsmr.adoc b/2021/osmodevcall-gsmr/osmodevcall-gsmr.adoc new file mode 100644 index 0000000..ba6ec53 --- /dev/null +++ b/2021/osmodevcall-gsmr/osmodevcall-gsmr.adoc @@ -0,0 +1,280 @@ +GSM-R and its difference to GSM +=============================== +:author: Harald Welte <laforge@osmocom.org> +:copyright: 2021 by Harald Welte (License: CC-BY-SA) +:backend: slidy +:max-width: 45em + +== Overview + +What this talk is about + +* GSM-R history, stakeholders +* GSM-R technical introduction +* assumes good understanding of GSM +* focuses on differences between GSM-R and GSM + +== key GSM-R types of communication + +* 1:1 voice calls (normal CS calls) +* 1:n voice calls (broadcast calls) +* n:m voice calls (group calls) +* transmission of data for train control +** between RBC and train engine + +== GSM-R key acronyms before we start + +UIC:: International Union of Railways +ERTMS:: European Rail Traffic Management System +ETCS:: European Train Control System +RBC:: Radio Block Centre +Controller:: A person in a RBC in charge of controlling trains + +more acronyms to come, of course + +== GSM-R stakeholders / players + +UIC:: International Union of Railways +* established in 1922 with 51 members from 29 countries +* today 208 members from 5 continents +EC:: European Commission +GSM-R IG:: Industry Group +* representatives from equipment suppliers +CEPT:: Conférence Européenne des Administrations des Postes et des Télécommunications + +== GSM-R history + +* pre-1992: UIC requests allocation of frequencies from CEPT +* question whether to use TETRA or GSM +** GSM wins as it is already deployed in 1991/1992 +* 1992: EIRENE project started by UIC and EC +** specify requirements of railways for mobile networks +** first specs released 1995 +* 1995: MORANE project started by UIC +** validate EIRENE functional specs +** develop detailed technical specs [with ETSI, 3GPP] +** steering group of French, Italian and German Railways +** 3 trial deployments with all parts of the network +* 1997: MoU in UIC to stop investing in analog sytems +** later amended by AoI (Agreement of Implementation) +* 2000: conclusion of EIRENE and MORANE + + +== GSM-R related groups + +* ERTMS/GSM-R group +** ERIG: European Railway Implementors Group +*** those railways signing the MoU and AoI +** FG: Functional Group +*** maintains FRS (Functional Requirements Spec) +** OG: Operators Group +*** maintains SRS (System Requirements Spec) + + +== GSM-R related specs + +* EIRENE (European Integrated Radio Enhanced NEtwork) +** FRS (Functional Requirements Spec) +** SRS (System Requirements Spec) +** both are one document, versioned. current: FRS 8.0 and SRS 16.0 +* MORANE (MObile radio for RAilway Networks in Europe) +** many specs, divide in three classes of spec documents +*** FFFIS (Form Fit Function Interface Specification) +*** FIS (Functional Interface Specification) +*** FFFS (Form Fit Functional Specification) +* ETCS specifications +* plus of course the ETSI / 3GPP GSM specs (R99 or R4) + + +== GSM-R mobile station types + +* Cab Radio +** fixed installation in the engine cab, mainly for voice communication of driver +* EDOR (ETCS Data Only Radio) +** fixed installation in engine, exclusively for ETCS +* GP (General Purpose) Radio +** handheld for staff +* Operational / Shunting Radio +** handheld for staff in specific use cases + +== GSM-R frequencies + +* R-GSM band +** 876-880 MHz UL / 921-925 MHz DL +** mandatory in EU +* ER-GSM band +** 873-876 MHz UL / 918-921 MHz DL +** optional, used in Germany +* other countries use GSM-R in normal bands +** China: E-GSM, India: P-GSM, Australia: DCS 1800 + + +== GSM-R teleservices + +* mandatory +** classic GSM voice calls +** CSD (circuit switched data) +** Supplementary Services (SS) like UUS1 +** USSD +* optional +** GPRS/EGPRS +** SMS + + +== ASCI - Advanced Speech Call Items + +VBS:: Voice Broadcast System +* 1:n voice calls using shared radio resources +VGCS:: Voice Group Call System +* n:m voice calls using shared radio resources +UUS:: User-to-User Signaling +* ability to send information along call signaling (CC) +eMLPP:: Enhanced Multi-Level Precedence and Pre-emption +* different priorities of users / calls + +== VBS/VGCS on Um interface + +* uni-directional activation of TCH +** listeners are using DL-only TCH +** all MS in one cell assigned to same TCH/timeslot +** each BTS with at least one participant transmits same DL data +* talker (VGCS only) requests access via RACH in UL +* one talker at a time gets allocated the uplink TCH +* signaling via a new NCH (steals one SDCCH/8 like CBCH) +** NCH notification acts like a "shared assignment" +** group call reference + channel description + +== VBS/VGCS extensions in BTS + +* uni-directional TCH +* talker detection +* listener detection +* NCH support in downlink +* handle RSL notification procedure + +== VBS/VGCS extensions in BSC + +* definition of BS areas in BSC +* generation of RSL NOTIFICATION +* parsing VBS ASSIGNMENT REQ +* generating VBS ASSIGNMENT RESULT +* generationg VBS ASSIGNMENT STATUS + +== VBS/VGCS extensions in MGW, MSC + +* in MGW +** AoIP circuit sharing [one RTP in, many out] +* in MSC +** A/BSSMAP procedures +** BCC (Broadcast Call Control) protocol support +** GCC (Group Call Control) protocol support + + +== eMLPP + +* priorities A, B, 0, 1, 2, 3, 4 +** A+B not used in GSM-R +** 0 used for railway emergency calls +** 4 used for classic 1:1 / ptp calls +* BSC will pre-empt (kill) lower priority calls if higher priority calls come up + + +== ETCS / Euroradio + +* ETCS signaling between RBC and train engine +** exchanges information on position of train, permission to enter section of track, ... +* typically uses an EDOR installed in the engine +** at least two GSM-R MS inside, for redundant connection +* traditionally uses GSM CSD calls with transparent, async teleservice +** network required to support 2.4, 4.8 and 9.6 kbps +* EURORADIO layer inside the CSD call +* most recently also possible via TCP over GPRS + + +== ETCS extensions per network element + +* libosmocoding +** CSD convoluitional coding +* osmo-bts +** CSD de-interleaving +** RSL channel mode parsing +** CSD RTP encapsulation/decapsulation +* osmo-bsc +** RSL channel mode encoding +* osmo-mgw / libosmo-mgcp-client +** CSD in SDP +* osmo-msc +** CSD in L3 CC / MNCC + + +== Functional + Location Dependent Addressing + +* in classic GSM, addresses (MSISDN) identify a subscriber +* in railway networks, you often want to address users +** by their function (conductor, catering, driver, ...) +*** dialling plan encodes train number + function +** by their location (manager of _this_ train) +* USSD is used to register/deregister as a function +* HLR stores related functional addresses + +== GSM-R numbering plan + +The following prefixes define the GSM-R numbering plan: + +[cols="1,9"] +|=== +|1|Reserved for short codes +|2|Train Function Number +|3|Engine Function Number +|4|Coach Number +|50|Group calls +|51|Broadcast calls +|6|Maintenance and shunting team members +|7|Train controllers +|8|Mobile Subscriber Number +|=== + + + +== GSM-R SIM cards + +* specified in MORANE FFFIS for GSM-R SIM cards +* normal GSM SIM card with DF_GSM and DF_TELECOM +* additional files in DF_GSM related to +** eMLPP +** VGCS +** VBS +* additional files in [additional] DF_EIRENE, related to +** functional numbers +** shunting, call confirmation for emergency calls +** GSM-R network selection +** international code, network name + + +== GSM-R RAN / CN feature requirements + +* RANflex / MSC pooling required for redundancy +* ISUP + MAP for roaming between networks +* if GPRS (optional) is supported: +** NACC (network assisted cell change) mandatory +** inter-PCU LLC forwarding mandatory +* connection of controller equipment via ISDN or SIP +** DTMF is used to end/mute calls + + +== Roaming + +* international roaming between railway companies +** trains crossing borders is normal in Europe +* national roaming from GSM-R to public GSM +** in case of coverage gaps +** for fail-over + + +== EIRENE / MORANE specs + +can be found and downloaded at https://uic.org/rail-system/gsm-r/ + +== EOF + +End of File |