[arm-allstar] interconnection to other services/modes

[Eric Grumling]

At what point do we divorce ourselves from commercial gear? It seems to me the primary reason for the LMR world to move to digital was narrow banding. Even D-star was developed in a country where spectrum was sparse and because it adapted LMR world technology is narrowband. We have no such restrictions and as such should be able to use much more bandwidth for our digital transmissions. Remember that the FCC only specifies that we use the minimum power to transmit, nothing about minimum bandwidth other than the 56 Kbaud rule on VHF and above. It seems to me that a 56 K-symbols/sec QPSK or QAM signal should be more than sufficient for extremely HQ audio, and along with a modern error correction scheme like LDPC should perform better than FM. Using IP and SIP protocols could greatly simplify sorting out the logistics of making connections, and an element of open protocols and transparency. And as a side benefit we might actually get to send data faster than 1200 baud! The SDR code is already written for most of these modes, and FPGA chips are getting cheaper and more powerful all the time. The only thing missing is a pleasing package.

Eric Grumling
eric at grumling.com<mailto:eric at grumling.com>