What kind of codec makes the most sense to you? We have things like D-Star that have existing hardware (the codec exists and is documented). Many really seem to find it unusable since they have to pay for it. I find it odd that their time to reinvent the wheel is somehow free.
Are there any other answers, such as the GSM codec? Echolink uses that, and thus a path out of an echolink client to the ISS could be direct. I have a Java version of the echolink client that I wrote quite a few years back that could be used to investigate digital voice with other software codecs.
It would seem wise for the RF modulation scheme to have a reasonable FEC to try and minimize retransmission. What kinds of modulation schemes would be easy to put on board the ISS and potentially other craft that could be 100% hardware based to minimize the "moving" parts? For example are there any existing "FPGA" kind of device based SDR kits with "digital data modulation"? I've seen quite a few that are based on complete programs running on Windows or other OSes. We'll need something in hardened hardware I'd think.
Thoughts?
Gregg Wonderly
On 8/20/2011 9:10 PM, Phil Karn wrote:
On 8/19/11 7:51 AM, Gregg Wonderly wrote:
What kind of digital are you suggesting? Voice and data both? A digital path from anywhere on the planet to the appropriate ground station is easily doable with some "documentation" of the ground stations.
Digital voice would be the easiest to support since the data rate is so modest. Low rate data (< 100 kb/s) wouldn't be much harder. All it takes is a stabilized platform with microwave antennas. Any ground station with an Internet connection could automatically link with the ISS and relay it to a central point (e.g., Houston) and then hand it off to the next ground station. One advantage we hams have always had over NASA itself are our numbers and geographical distribution. We obviously wouldn't be able to cover the large parts of the earth that are entirely water but we could still do a pretty good job with the rest.