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: <6895.27CDE02A@zswamp.fidonet.org> Date: Thu, 28 Feb 91 20:38:52 EST Organization: Izot's Swamp BBS - Kitchener, Ontario >From: tnixon@hayes.uucp > I would think PEP, using more of the available frequency bandwidth > should be able to get consistently 18,000 bps or higher. Why not? >PEP already uses virtually all of the available bandwidth; I think the question here is, why does V.32bis (or the newer HST modulation) get 14,400 bps raw carrier throughput on all decent lines, while PEP may reach 16,000 bps only under very rare 'ideal' lines. I've often wondered what could be done to improve DAMQAM modulation. It is, after all, the oldest of the current high speed dialup modem technologies, predating the HST, the V-9600, and even the widespread public acceptance of 2400 bps! 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? I've also wondered about the overlap of the bandwidth; if their carriers are 7.8 Hz apart and operating at 8 baud, does this not make their outside harmonics, according to Fourier's theorems, overlap the next carriers' (both up and down) fundamental frequencies? If these harmonics are subject to a significant reduction in amplitude, could they perhaps be crammed a bit closer or operated at higher baud rates? Bottom line: I can imagine multicarrier technology benefitting from the application of improved technology, but there seems to be no move on Telebit's part to do so. From this I can only conclude that the future of multicarrier technology lies with maintaining compatibility with existing PEP installations... I do not think that we will see improvements in DAMQAM from Telebit. PEP is coasting. >Other companies that promote multicarrier modulation have >eliminated ISI through other methods, allowing throughput >well over 20kbps. I was not aware that any companies were promoting, in a large way, general purpose multicarrier modems... -- 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