Multiple Transceivers in Osmocom

First OpenBSC supported BTS Siemens BS-11 was 2-TRX
- OpenBSC (OsmoNITB) had multi-trx support from the very beginngin
ip.access nanoBTS can be stacked for multi-TRX
- OpenBSC (OsmoNITB) has supported this for many yeasr
Classic OsmoBTS was single-TRX
osmo-bts-trx was extended with 2 TRX support but not in master until recently

OsmoBTS supported hardware (currently)

osmo-bts-trx for OsmoTRX (UmTRX, USRP, …)
- had two-trx support in fairwaves branch
- assumes two soft TRXs in a single "transceiver" program (OsmoTRX)
- has lots of global variables assuming a single transceiver program handling all TRXs :(

osmo-bts-litecell15 for Nuran Litecell 1.5
- shared memory message queues between PHY-DSP and ARM core
- very similar to osmo-bts-sysm, but:
- has two TRXs available to ARM CPU

A PHY link is a physical connection / link towards a given PHY. This might be, for example,
- a set of file descriptors to device nodes in the /dev/ directory (sysmobts, litecell15)
- a packet socket for sending raw Ethernet frames to an OCTPHY
- a set of UDP sockets for interacting with OsmoTRX
Each PHY links has a set of attribute/parameters and a list of 1 to n PHY instances.
PHY links are numbered 0..n globally inside OsmoBTS.
Each PHY link is configured via the VTY using its individual top-level vty node.
The PHY links and instances must be configured above the BTS/TRX nodes in the configuration file. If the file is saved via the VTY, the code automatically ensures this.

A PHY instance is an instance of a PHY, accessed via a PHY link.
In the case of osmo-bts-sysmo and osmo-bts-trx, there is only one instance in every PHY link. This is due to the fact that the API inside that PHY link does not permit for distinguishing multiple different logical TRXs.
Other PHY implementations like the OCTPHY however do support addressing multiple PHY instances via a single PHY link.
PHY instances are numbered 0..n inside each PHY link.
Each PHY instance is configured via the VTY as a separate node beneath each PHY link.

Each TRX node in the VTY must use the phy N instance M command in order to specify which PHY instance is allocated to this specific TRX.

Questions?