Monday, June 30, 2008
Asterisk is an Open Source PBX & Telephony Platform. It’s often labeled as the future of telephony.
PBX stands for private branch exchange. It is a machine that handles many businesses telephones calls for you. Its main functions are to transfer calls to different individual phones; play music when somebody is put on hold; to play automated voice responses when a call is received; to provide an options menu for the caller etc.
Asterisk allows one to build their own phone systems. It adds features, functionality and reduces deployment costs in ways which; at first are a little difficult to understand.
How does this relate to amateur radio?
Very simple, the future of two way radio is digital. As of writing, TV are required to be full digital and shut down their analog transmitters in Feb. 2009. The only spectrum broadcasters are required to vacate are channels 64 thru 69 that will become the new "700 MHZ band" that is being auctioned off by the FCC. The vacated areas of this spectrum will be utilized for: Public Wireless deployment (Cellular/PCS); A wide-band private data network that will be shared between public safety and paying customers; and new spectrum for public safety that will butt right up to the re-located NPSPAC National Public Safety Planning Advisory Committee band being moved to 806-809/851-853 by Sprint/NEXTEL.
Public safety also has guidelines to migrate to APCO-25 digital. The future of two way radio is digital, and we must also advance in this direction. The digital premise is that it generally allows more use in a more efficient/flexible use of band space.
Most present day government communication centers that use analog systems happen to have a VOIP based dispatch console. This analog to VOIP patching is something that we are presently also embracing in ham radio with IRLP, EchoLink, Yeasu WIRES II, and the like.
A different hardware board for each of these proprietary VOIP systems that you want to support is required. You also need a need a multi-port repeater controller, to support each hardware boards analog breakout. This seems redundant to me, and is something that slows the advancement. IRLP seems to be the system of choice because it runs on the Linux operating system. This is because Linux is much more stable that Windows, and is an open source development.
Your seeing the migration in the commercial world as I pointed out; hello digital TV. And the only analog part left of traditional telephone is the “last mile” drop to your home. Time Warner and now AT&T are providing digital phone service to close that up too.
I really feel there "Could be" something big with Asterisk Telephony and perhaps D-Star. The marriage seems natural. I even think it can be integrated with existing VOIP systems like D-Star and EchoLink.
I feel anything is only a "could" type of thing, only because of how the concepts are presented to the amateur audience. This hobby is supposed to be about advancing technology...
As of writing there aren't any directed approaches to tie this to the hobby that I can point you to. There are a number of open ended ideas from a variety of different people. What I'm saying is there is no one entity steering the ship, so to speak. This ideas are still in development. Which makes it precisely the time to jump aboard and get our hands in it and see what we can do with it. So in light of that I suggest a google search for more info... Once you get interested you're likely to bump into myself or other hams on various message boards. And you will likely also have run across a few ideas on how to integrate it to the hobby.
If your interested in giving Asterisk a test drive I found this video overview a good starting point for myself. AsteriskNOW, or PBX in A Flash are both good starting places. They are a Linux install with Asterisk and a Asterisk GUI rolled into a bootable ISO CD install.
Thursday, June 19, 2008
The second phase or revision of D-Star is out there. Both Icom and Kenwood are selling radios for it, it's general name is NXDN - FDMA.. It's know as Icom IDAS (Icom Digital Advanced System) and Kendwood calls it NEXEDGE.
NXDN Forum Announces its Formal Establishment
This is a brand-new digital format was co-designed by Kenwood & Icom that is geared towards the business sector. It is designed for those that want to meet the up-coming FCC mandate for 6.25 KHz channel spacing, but that can't (or don't) want to move to the APCO P25 Phase-II equipment that will soon come to market. The format is based on the AMBE+2 voice codec (similar to ICOM's D-STAR), but uses a 4-level FSK modulation (FDMA). The radios are capable of narrowband analog, along with 12.5 KHz & 6.25 KHz digital emissions. Kenwood is offering the system under the name NEXEDGE, and the radios are capable of both conventional & trunking operation. The attached sound file contains all of the formats the system is capable of producing, including the raw data streams of both digital formats.
D-Star, developed by ICOM, is the forerunner to the commercial counterpart of the technology we now know as IDAS (ICOM Digital Advanced System).
IDAS, also known as FDMA is the system generally best suited for commercial use since it meets all FCC technical standards through 2018 and is backwards compatible with 25 kHz, 12.5 kHz analog systems plus capable of operating in the digital mode on 25, 12.5, and 6.25 kHz channel spacing.
We have been to be Icom's lab rat for their rollout of commercial P-25 Phase-2 products. It's nice to know that the AMBE codec that was chosen for D-Star is slated to replace the IMBE codec in Phase 2 of APCO 25. For once it puts us as ham radio operators into state-of-the-art in communications for the first time in about 10 years. It's so nice to say that.
It uses AMBE+2 codec and 4FSK (4 level FSK) / FDMA (frequency-division multiple access scheme) digital modulation. AMBE+2 codec is compatible with IMBE used by P25 phase I.
NexEdge/IDAS was built off D-Star. Unlike D-Star, the NXDN repeaters can repeat analog or digital so you can have a smooth user migration.
It supports unit ID auto-roaming/registration much like how D-Star works.
Looks like the pricing to get going with NXDN will be about half the cost of D-STAR implementation. NXDN is like MOTOTRBO in that it can support mixed mode, but whats nice unlike MOTOTRBO & D-Star is more than one manufacture making radios & costs less on both accounts.
An ID-RP2C Repeater Controller for D-Star runs about $1500. You need to add an band specific RF voice module such as the ID-RP2000V for 2 meters which is another $1400
Where as the Icom IC-FR5000 Series VHF and UHF Repeaters run about $1500. This NXDN route also provides the analog/digital mixed mode backwards compatibility that D-Star doesn't.
The user end radios between D-Star and NXDN appear to be very similar in price.
The best overview I have found:
I'd like to think that now since Kenwood is making AMBE Digital voice radios for their Nexedge, that one might see a Kenwood D-Star radio here in the US in the not to distant future.
If they do this, I hope they can improved upon the current Icom line.
Thursday, June 12, 2008
I converted one of John, N5OOM's slide show presentations on HSMM. He created it for the North Texas Microwave Society to explain what high speed multi media is and why hams should be exploring it. As well as how it works, and how hams can use it along with so much more. http://n5oom.org/hsmm/