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diff --git a/doc/phy_link.txt b/doc/phy_link.txt new file mode 100644 index 00000000..c49e328f --- /dev/null +++ b/doc/phy_link.txt @@ -0,0 +1,57 @@ + +== OsmoBTS PHY interface abstraction + +The OsmoBTS PHY interface serves as an abstraction layer between given +PHY hardware and the actual logical transceivers (TRXs) of a BTS inside +the OsmoBTS code base. + + +=== PHY link + +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 interface 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. Given the different bts-model / phy specific properties, the +VTY configuration options (if any) of the PHY instance differ between +BTS models. + +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. + + +=== PHY instance + +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. Given the different bts-model / phy specific properties, the +VTY configuration options (if any) of the PHY instance differ between +BTS models. + + +=== Mapping PHY instances to TRXs + +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. |