IMBE Conversion to Streaming VoIP and the Intellisite Rptr

[ASTROMODAT]

I understand that the IP-based Intellisite repeater (with SZ6.x software) somehow converts IMBE to streaming VoIP (and visa versa, of course), and thus eliminates the need for the DIU. Does anyone know what type of "box" is used to do the VOCODing function at the console, if there is no DIU involved?

To my knowledge, in order to accomplish IMBE VOCODing, one MUST pay a "per unit" licensing fee to DVSI, one way or the other, so I am very curious as to the approach involved with IMBE and VoIP (especially if there is no DIU involved---where is the IMBE VOCODER in this case?!). Is it simply on a chip somewhere in the console that is required with SZ6.x?

With DVSI's IMBE, one must either 1) buy the individual chips from DVSI, typically in small quantities (e.g., as ICOM is doing with their AMBE 2020 VOCODER chip used in their D-STAR radios), or 2) you can buy the rights to load "x" number of DSP chips with DVSI’s IMBE VOCODing code, and the more DSP units loaded with IMBE, the more you pay, and so on (which is essentially how Motorola handles the DVSI licensing fee, which is a part of the reason that an IMBE uplift on an ASTRO P or M radio is $800).

Larry

[xmo]

"...Does anyone know what type of "box" is used to do the VOCODing function at the console..."
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They call this box "MGEG" for "Motorola Gold Elite Gateway" It is based on the same compact PCI plarform as the other 'brains' of an SZ6x system [Zone Database Server, Fullvision Server, User Configuration Server, Air Traffic Router, System Statistics Server, etc.]

The catalog sheet [R3-13-2005] says: "The MGEG uses a Microsoft Windows operating system and custom application software developed by Motorola to provide audio vocoding, system fault management and configuration services"

[ASTROMODAT]

Thanks for the follow-up, xmo! This makes me more curious than ever. It seems to imply that they are loading IMBE on software on the MGEG PC? I was under the impression that this sort of appraoach was generally taboo, per DVSI, as IMBE code on a PC could make it somewhat easy (at least for a really good hacker!) to circumvent DVSI's licensing fees, etc. Thus, the dual option licensing approach that I mentioned in my previous post. Maybe Motorola has an ultra "special deal" with DVSI that allows this MGEG/PC software approach for the IMBE VOCODing?? I suppose it is consistent with Option #2 (load IMBE VOCODER software on a DSP, and pay a per DSP licensing fee). Still, once you load lines of code on a PC, think of the huge potential problem that now arises with hacking and pirating!

I understand that the TAPER guys have repeatedly begged DVSI for some way to get IMBE loaded onto a PC (strictly for experiementing /non-commercial Ham radio use only). This way, TAPER could port the IMBE VOCODER functionality onto a PC for experimentation, and the like. TAPER has consistently been told not only NO, but h_ll NO!, by DVSI. I may have this wrong, but this is my understanding of the situation.

Larry

[radiomidwest]

Seems like DVSI is pushing thier AMBE as the current technology and that IMBE is so "yesterday". With more and more products hitting the market with AMBE, do you think we will see a move to this more Advanced vocoder?

Here is a quote:
A subjective Mean Opinion Score (MOS) is used in speech processing research to assess the performance of a vocoder. Independent commercial and academic laboratories have confirmed that the 4.8 Kb/sec AMBE vocoder subjectively outperforms other vocoder standards at their significantly higher bit rates: G.729 at 8 Kb/sec; G.726 at 32 Kb/sec; and GSM at 13 Kb/sec. AMBE even subjectively outperforms the FS-1016 vocoder at the same 4.8 Kb/sec. These better MOS metrics obtained at lower bit rates have improved the performance of mobile satellite and radio systems, including the APCO Project 25

Should we just call it "quits" on IMBE and FDMA and start moving towards AMBE/OFDM and cut our loses now?

[ASTROMODAT]

Yes, we will see AMBE replace the P25 IMBE VOCODER as a future Phase of APCO 25. The IMBE design is now quite dated. AMBE is essentially DVSI's replacement technology for IMBE, given that we need time for the standards to evolve. It's important to understand that the primary reason for digital over anlog FM is to achieve more efficient use of limited bandwidth/spectrum. With P25, the first phase calls for 1, and then 2, talkpaths per 25 kHz, using FDMA and the IMBE full rate VOCODER. Phase 2 will utilize TDMA, with the AMBE half-rate VOCODER and we will achieve 4 talkpaths per 25 kHz. And, Yes, at that point folks will need to junk all of their old FDMA IMBE P25 radios and replace them with TDMA subscriber radios. Motorola probably just hates this, but they will reluctantly sell all new radio systems to the poor User Schmucks!

The full rate IMBE VOCODER runs at 4400 bps voice data, plus 2800 bps FEC, for a total of 7200 bps for P25 Phase I. AMBE is a so-called "half rate" VOCODER and it runs at 2450 bps voice data, plus 1150 FEC, for a total of 3600 bps. The AMBE half rate VOCODER, with its advanced design and markedly improved codebook, sounds as good, and even better, than the full rate IMBE VOCODER. This is not just a marketing hype by DVSI. This has been demonstrated in user listening tests using MOS (a technique developed many years ago by Bell Labs).

It's called "technology'---more, better, faster, cheaper, smaller, lighter and ALL for less money. You get the drill. Just like the Big Boss demands in 2004---it's the new American Sweat Shop!!

Larry