Path: utzoo!utgpu!watserv1!maytag!xenitec!zswamp!root From: root@zswamp.fidonet.org (Geoffrey Welsh) Newsgroups: comp.dcom.modems Subject: Re: PEP vs. v.32 Message-ID: <6927.27D24513@zswamp.fidonet.org> Date: Mon, 04 Mar 91 00:50:30 EST Organization: Izot's Swamp BBS - Kitchener, Ontario In a letter to All, Greg Andrews (gandrews@netcom.COM ) wrote: >In article <6895.27CDE02A@zswamp.fidonet.org> >root@zswamp.fidonet.org (Geoffrey Welsh) writes: > > For instance, I've noticed that the trend in 9600+ bps modems is to >increase the resolution in the coding constellation. PEP still uses sixteen >point QAM; has DSP technology not improved enough to enable us to code more >than four bits per baud in a multicarrier scheme? > >PEP isn't limited to a 16 point constellation. In the >cleanest parts >of the line you'll see carriers using a 64 point (6 bit) >constellation. >Unless the modem decides the line won't support that kind of >signal resolution... My disappointment has doubled. At first I believed that Telebit & co. were simply not pushing the technology. Now I that I have reason to believe that they are, I can't avoid the conclusion that they are doing so poorly! If there are 511 carriers operating at a maximum of 8 baud with 4 bit QAM, the maximum possible raw throughput is in the vicinity of 16000 bps, a figure which I have seen Telebit modems approach on clean lines. If, as you say, they're using a 64 point constellation, the maximum raw throughput should be around 24000 bps, and I've never seen a TB come even close to that. -- UUCP: watmath!xenitec!zswamp!root | 602-66 Mooregate Crescent Internet: root@zswamp.fidonet.org | Kitchener, Ontario FidoNet: SYSOP, 1:221/171 | N2M 5E6 CANADA Data: (519) 742-8939 | (519) 741-9553 The mile is traversed not by a single leap, but by a procession of coherent steps; those who insist on making the trip in a single element will be failing long after you and I have discovered new worlds. - me