Feature #3537
closedBSC support for CBSP (cell broadcast service protocol)
100%
Description
Right now, the only way to send cell broadcast messages is to use the BSC VTY.
3GPP Specifies CBSP in TS 48.049 as the protocol used between BSC and CBC to configure which kind of messages shall be broadcast where, and for how long.
It's a simple TLV based protocol encapsulated in TCP, so the protocol itself should be rather easy to support. However, it requires an underlying SMSCB scheduler that provides the required functionality for routing/scheduling. See #3536.
Related issues
Updated by laforge over 5 years ago
- Related to Feature #3536: BSC: support for repeated scheduling of SMSCB messages added
Updated by laforge over 5 years ago
- Is duplicate of Feature #2392: Support for BSC-CBC interface (CBSP) to a cell broadcast centre added
Updated by laforge almost 5 years ago
- Due date set to 05/06/2019
- Start date changed from 09/09/2018 to 05/06/2019
- Follows Feature #3972: CBSP definitions, encoder, decoder for libosmocore added
Updated by laforge almost 5 years ago
- Related to Feature #3973: wireshark dissector for CBSP protocol added
Updated by laforge almost 5 years ago
- Related to Feature #3974: TTCN-3 ProtocolModule for CBSP added
Updated by laforge almost 5 years ago
- Related to Feature #4046: BSC support for generating ETWS primary notifications added
Updated by laforge almost 5 years ago
- Priority changed from Low to Normal
I've been re-reading specs and thinking a bit more about implementation. They key part of this seems to be:
allocator¶
The allocator takes care of determining if a new SMSCB message of given size (number of pages), repetition period and category(priority) can still be sent over the given channel (basic/extended) at a given BTS.
This allocator then is executed for each cell in the list of cells where the message is to be broadcast, and the results from the allocator determine if we send a CBSP WRITE-REPLACE COMPLETE or a WRITE-REPLACE FAILURE. Where interestingly, the FAILURE can very well be a partial failure, containing a list of cells in which it failed and in which it succeeded.
scheduler¶
The scheduler runs for each BTS separately. It has a list of SMSCB which are to be broadcast in this BTS, and must determine which page of which SMSCB message to transmit at which given point in time to ensure the repetition period is respected
CBSP client¶
The CBSP client will connect/reconnect to the CBC, ensure the link works (keep-alive).
It will [optionally] use some Osmocom-propietary means to identify the BSC (and its served cells) to the CBC, avoiding the need for manual configuration of this data out-of-band to the CBC.
CBSP server¶
The spec appears to require the BSC to accept an inbound TCP connection from the CBC. We should support this for interoperability. Only one CBC can ever talk to a BSC, so we should have some kind of "either client or server" configuration. Only one connection shall be accepted in the server-side socket.
Implementation Strategy¶
Iterative approach¶
In terms of an interative implementation approach, the following short-cuts could be taken while stubbing out some of the functionality:- assume that there's unlimited CBCH capacity, i.e. accept all WRITE-REPLACE even if they cannot be scheduled. Works for low CBCH load situations, which are likely in practise
- always broadcast each SMSCB on all cells in the BSC, avoiding implementing 5 different ways on how the Cell List can be encoded in CBSP
Test driven¶
Let's first implement BSC_Tests.ttcn coverage for SMSCB/CBSP and then use that to drive the implementation. Emulating a number of BTSs on the RSL side as well as the CBC on the CBSP side are sufficient for testing anything we need.
Updated by laforge almost 5 years ago
- Status changed from New to In Progress
- % Done changed from 0 to 10
work on this has started a few days ago.
Updated by laforge almost 5 years ago
- % Done changed from 10 to 60
laforge/cbsp
branch of osmo-bsc.git. It is currently untested, but should do the following things:
- handling of WRITE_REPLACE, KILL and RESET procedures via CBSP from the CBC
- VTY configuration for the CBSP link
- CBSP TCP client and server role
- CBSP LOAD QUERY
- CBSP MSG STATUS QUERY
- tests, tests, tests
Updated by laforge over 4 years ago
- % Done changed from 60 to 80
ots of work has been done on this, see https://gerrit.osmocom.org/#/c/osmo-bsc/+/15373/ for the actual code, and https://gerrit.osmocom.org/15374, https://gerrit.osmocom.org/15375 and https://gerrit.osmocom.org/15376 for related tests.
Updated by laforge over 4 years ago
- Status changed from In Progress to Resolved
- % Done changed from 80 to 100
code merged