----- Original Message Posted to illinoisdigitalham-yahoogroup Sun Jul 22, 2007 -----
A key component in all these digital voice systems is the vocoder. P25 uses IMBE from Digital Voice Systems Inc (DVSI). It costs $150K to get the rights to play with that mode plus $5 a seat. There is no off the shelf IC to do it.
D-Star uses AMBE from DVSI. Same $150K if you want the software source but they do offer a single chip solution for $20 single qty and are happy to sell to hams. (The AMBE IC 2020 as of January 2008 is $20. The AMBE 2000, used in the DVDongle, is $33. DVSI's usual policy is to sell in minimum lots of 5 or so chips, they decided to sell the AMBE 2020 in quantities of just one to hams.)
There seems to be a lot of hand wringing because the DVSI chip's source code is not available to hack and so hams should not use it. I look at it as just another chip like a Pentium processor or ethernet controller IC, who cares that I don't have access to the chip's internal mask set as long as I am able to use it however I want.
The D-Star protocol is all open and can be designed to with a little work. The internet backbone is also now understood and being documented thanks to Robin, AA4RC. (opendstar.org)
I am working on two D-Star related projects now. One is now working and is an "AMBE Dongle" which plugs into a PC USB port and looks like a serial port. The dongle contains an AMBE2020 chip and can be used for voice compression/decompression using a PC. This will allow D-Star operation using a pc and soundcard over the network or whatever.
The dongle currently just gives/takes the raw 16bit PCM 8ksps data and the entire 48byte AMBE compressed data/control frame and
sends/receives it over the standard serial port. The serial COM port runs at 230400bps to be able to keep up.
The dongle processor is an Atmel SAM7s256 which is not using much of its resources so custom apps can easily be downloaded. It has a boot loader so you can update over the same serial port. The current code uses FreeRTOS and the Eclipse/GNU tools to generate so can be developed for free. The code will all be open source as well as the HW.
The USB/serial interface uses the FTDI FT232RL chip which has drivers for Windows, Linux and I think the Mac. It just looks like a standard 8N1 230400 serial port on the PC.
Not sure when/how it will be made available. No idea what qty's are involved. I need one more PCB spin to make it compatible with the AMBE 2000 full duplex chip but after that it should be ready to go. See: http://www.moetronix.com/dvdongle/
The minimum I would do is make the PCB's available and if the qty's are sufficient then maybe it could get built as a complete unit. It was designed to fit in a cheap little standard Hammond plastic box.
The other project is a D-Star GMSK modulator/demodulator that will allow D-Star operation using a non-Icom radio. This project is still in the planning stages. The user interface is the kicker.
Someday I may get back to finishing the original DVX radio project but alas time seems to be a diminishing resource :(
See Moe, AE4JY's Digital Voice Transceiver Project.
The DV Dongle is now a product and can be purchased from AES & HRO (http://hamradio.com) ... large stock of DV Dongles in on the 28th of January 2008. More info can be found at http://www.dvdongle.com. To clarify it doesn't handle GMSK modulation/demodulation.
The DV dongle is an important development. It was started by AE4JY and AA4RC. It contains the ability to process AMBE full duplex. Presently software applications exist to use this to communicate from a computer to a D-Star gateway. Further development are expected so that it can be interfaced to a radio's packet radio port that has the necessary discriminator connections.
To clarify it doesn't handle GMSK modulation/demodulation yet. Moe has mentioned a possible GMSK modulator/demodulator project.
Fred N. van Kempen, PA4YBR has also announced that he too, has a working decoder. GMSK Smart Modemcontroller. He does the GMSK in hardware though, so probably his code is not too useful for people who want to play with D-Star on their PC's using the soundcard.
This may be a huge milestone. The ability to retrofit an existing repeater could be possible with this. Not only that, but you may be able to retrofit it in such a way that it can be useable in analog and for D-Star. Something to keep an eye on!
D-Star's greatest threat to itself is the cost. If they figure out how to bring the price down near what analog radios can be bought for, it might have a better chance. Motorola and other commercial manufacturers had little success selling their ultra expensive digital systems until the Federal government started pressuring (mandating) a transformation to narrowband and trunking to conserve spectrum. Digital will never be mandated in the amateur radio service so market forces will determine the survivors.
The DV-Dongle (http://www.moetronix.com/dvdongle/),
being tested by the fellows in Atlanta, is the missing piece of the puzzle.
With the DV Dongle you will be able to use DPLUS or the future OpenDSTAR gateway software to connect to the gateway computer behind the ID-RP2C (repeater controller). Then you will use the DV Dongle to extract the audio streams and can transcode them to standard G.711a/u, GSM, G.729, etc. and then use the Asterisk PBX power for telephone, voicemail, DID-Callsign-DID, repeater, etc. interconnection.
DPLUS is a gateway addon daemon that provides a number of functions see: http://opendstar.org/tools/readme.txt
When you take a digital radio platform like D-Star, this is where integrating Asterisk could be very powerful. Since the call sign is part of every packet, this could be assigned to a direct inward dialing number (DID) or extension.
Using the AMBE-2020 chips in a PCI card or USB dongle will allow the conversion of the DSTAR Digital Voice to/from alaw or ulaw 8k digital voice and the chip decodes/encodes DTMF ... this combined with the datastream (containing callsigns) should enable making DSTAR radios extensions on a Asterisk PBX (or even assign a DID to them) -- total 2-way ROIP/VOIP integration that can route to/through the PSTN. (Example: dial 1-800-4KB9MWR and get a call you can pick up on your DSTAR radio and vice-versa.) Pretty powerful for EMCOMM and personal use. All enabled by open source.
Until we have the OpenDSTAR gateway software replacement (with source), the DPLUS to SIP solution could be made to work.
However this dongle to SIP approach (at least for now) is a non-RF application. What would be even more ideal is if the various D-Star radios had a digital interface port/jack. I'd love it if I could buy a D-Star radio, that has an digital interface of sorts. Something along the lines of D-Star non-proprietary interface. Perhaps a mini-USB interface that perhaps transcodes to a more open standard codec like G711 using SIP and RTP protocols (standardized protocols) so one can connect the radios together into wide area networks. It would be great to see an a D-Star radio that supports something like this on the market possibly before the P25 interface idea ever makes it to the market.
Interconnection with Asterisk, not for linking in other repeaters, but for a variety of applications that can then be added using callsign routing married to the SIP protocol.
The open source project25 interface is a good idea. Unfortunately the problem they're facing is that most of the manufacturers don't bother following the ISSI spec, nor does the ISSI spec call out hardware interface details. So basically the "plugs" on the back of say, a Quantar... don't match the "plugs" on the back of a MASTR III.
"The Project 25 Inter RF Subsystem Interface (P25 ISSI) is a
non-proprietary interface that enables RF subsystems (RFSSs) built by different
manufacturers to be connected together into wide area networks."
ARRL: It Seems to Us: Interoperability October 1, 2007 We should encourage D-Star manufactures to come up with a similar style non-proprietary interface for D-Star.
I'd love to be able to have a D-Star radio in my
shack also interconnected to various Asterisk powered applications in my house.
Where if I wasn't around to take a directed D-Star call, it could be configured
as a DID to my system and use a ring group / follow me list to let the radio
caller ring my home phone or leave a voice mail. Unfortunately at this
time there are no known interfaces to the Icom D-STAR radios that allow access
to the on-air data stream.
http://groups.yahoo.com/group/gmsk_dv_node D-STAR GMSK Node Adapter - This group is dedicated to discussion regarding the construction of 7M3TJZ/AD6GZ's D-STAR GMSK Node Adapter. More information can be found on Satoshi's web site: http://d-star.dyndns.org/ His adapter which will turn an analog radio into a D-Star radio (Satoshi is a member of the D-STAR standardization committee)
Satoshi has two different constructions projects available. The one that is
the main focus of this group - the node adapter - is basically a GMSK smart
modem tailored to D-STAR. The other, which has not been discussed on this group,
is a full blown adapter to turn an analog radio in to a D-STAR radio and does
include provisions to encode/decode AMBE.
The node adapter has two modes - simplex and repeater. In simplex mode, node adapter only serves to decode/encode the GMSK modulation used by D-STAR radios and turn it into a bit stream that can be fed into a computer. In repeater mode, the node adapter serves as a bit regenerative repeater. However, while in repeater mode, the node adapter does not have the capability to pass any data in/out of the computer. So, in repeater mode, the node adapter can not be linked to any D-STAR gateways/reflectors.
In simplex mode, the node adapter can be used with D-STAR Hot Spot to provide a simplex RF point of presence to the D-STAR network. In my case, I live just slightly out of range of my local D-STAR repeater to be able to work it with my HT in my house. Setting up a node adapter with D-STAR Hot Spot, allows me to basically extend the RF range of my local repeater (on a different simplex frequency). I can also connect directly connect to other D-STAR repeaters/reflectors and QSO's there as well.
The node adapter/Hot Spot combination has NO PROVISIONS TO CONVERT D-STAR DIGITAL VOICE TO ANALOG VOICE. That is not it's purpose, and it will never do so. This hardware software combination operates in 100% digital mode.
I am planning to work on a future version of D-STAR Hot Spot that will have a repeater mode. This new version will use Jakub Hruska's GMSK sound card decoder in receive mode and Satoshi's node adapter in transmit mode to operate as a D-STAR repeater with connectivity (via DPlus) to the D-STAR network. As long as there's enough free CPU cycles to process the DV stream, this should be simple extension of D-STAR Hot Spot.