Narrowband LBL Ping Unsupported by mm_driver

[Chris Murphy]

mm_driver.cpp implements support for several ranging types, including the remus digital transponder. Additionally, modem_message.proto defines the type "ModemRangingRequest" which has members appropriate for digital transponders. Narrowband LBL transponders, supported by the CCPNT command, require frequencies, timeouts, and turnaround times to be specified.

Is extending ModemRangingRequest to have a superset of all parameters the right approach, or is there a better one?

Both transponder types return the same traveltime message, so there should be no conflicts on that front.

[toby schneider (tes)]

Ultimately I think we have to decide what the "core" set of ranging features a "canonical" acoustic modem should support and these are what would be in the basic ModemRangingRequest. Any modem specific features that go beyond this "core" set should be extensions (see http://code.google.com/apis/protocolbuffers/docs/proto.html#extensions) to the ModemRangingRequest / ModemRangingReply messages.

For example, this division is how configuration for various modems is handled presently. The DriverConfig (driver_base.proto) has the "core" set of configuration values that all modem drivers need, whereas specific modems (in our case the WHOI Micro-Modem) extend this message (in mm_driver.proto) to give modem specific features (like NVRAM settings).

For now, I would not hesitate to add features to the ModemRangingRequest directly, and we can always split it into extensions as ranging using non-WHOI Micro-Modems becomes a relevant issue.