Path: utzoo!attcan!uunet!cbmvax!grr From: grr@cbmvax.UUCP (George Robbins) Newsgroups: comp.dcom.modems Subject: Re: Break definition (Some Answers from the Standards, LONG) Message-ID: <4765@cbmvax.UUCP> Date: 17 Sep 88 03:18:24 GMT References: <39157@pyramid.pyramid.com> <39163@pyramid.pyramid.com> <2035@looking.UUCP> Reply-To: grr@cbmvax.UUCP (George Robbins) Organization: Commodore Technology, West Chester, PA Lines: 33 In article <2035@looking.UUCP> brad@looking.UUCP (Brad Templeton) writes: > But if DAMQAM is really a broadband scheme with 511 carriers using up > the entire band, why do all 511 of the carriers have to be in the > same direction? In interactive mode at least, I wish they always had > at least one carrier in each direction, so that no turnaround would be > required. > > In fact, even if having a reverse direction carrier meant you couldn't > use several of the nearby bands in the forward direction, it would still > be worth it in interactive mode. Ideally it would be nice to see 2 > permanent carriers in each direction, and 507 switchable carriers. > (You may need more than 2 to achieve the information rate required with > error correction, but you get the gist. 100 bps would be adequate for > typing and ACK/NAKs of other protocols.) The disparity between transmitted and received signal levels mean that you need either fairly sophisticated processing or a wide guard band to prevent interference. Obviously it could be done, and might be a real win. Note that 100 bps is probably ok for typing, but some protocols, for example uucp "g", require a backwards channel of somewhere between 300 and 600 bps to keep up with 9600 baud forward. Tis why the USR Courier HST isn't the magic modem for uucp... > -- > Brad Templeton, Looking Glass Software Ltd. -- Waterloo, Ontario 519/884-7473 -- George Robbins - now working for, uucp: {uunet|ihnp4|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@uunet.uu.net Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)