jsloan@wright.UUCP (12/01/87)
Some time ago I helped write an RFP for a 10 Mb/sec ethernet-to-ethernet link via microwave (thanks, Kent England at BU for the info!). We have since contracted with the vendor and installation should be completed around Christmas. In the process there has been some mutual education between the microwave group and the networking group on campus. There are now incredibly cheap (a few thousand $s) microwave systems, with dishes that you could put in a briefcase, that could conceivably be pushed to 10 Mb/sec over very short distances. How long will it be before it will be cheaper to run networks between adjacent buildings on a campus or research park etc. using these tiny microwave systems instead of running copper or fiber? I suspect the major cost would be the ether bridges on either end that may be necessary (and maybe not), but it could also be that you would want packet filtering with bridges even if you used copper or fiber. I remember reading about lasers doing similar things. Also an interesting thought. Our RBOC bid a optical fiber link. Although their ethernet-to-ethernet product (if its not vaporware) was not available by our deadline, this too is an interesting idea, not for short distances (a solution which has been around for a while) but for long distances, like over five miles or more. Managing a geographically dispersed ethernet would be challenging, but the functionality is appealing. Anyone have any concrete ideas on any of this? Those little microwave dishes are looking better and better. -- John Sloan Wright State University Research Center jsloan@SPOTS.Wright.Edu 3171 Research Blvd., Kettering, OH 45420 ...!cbosgd!wright!jsloan (513) 259-1384 (513) 873-2491 Logic Disclaimer: belong(opinions,jsloan). belong(opinions,_):-!,fail.
kwe@bu-cs.BU.EDU (kwe@bu-it.bu.edu (Kent W. England)) (12/02/87)
In article <203@wright.EDU> jsloan@wright.EDU (John Sloan) writes: > >There are now incredibly cheap (a few thousand $s) microwave systems, >with dishes that you could put in a briefcase, that could conceivably >be pushed to 10 Mb/sec over very short distances. Now this is something new to me. If you can put them in a briefcase they must be around 100GHz. That would probably limit the range to a mile or so. The problem with infrared laser technology is the atmospheric attenuation of smog, fog, and rain. Sounds like this new ultra-high freq microwave fills the gap between low freq uwave and infrared. > >Our RBOC bid a optical fiber link. Although their ethernet-to-ethernet >product (if its not vaporware) was not available by our deadline, this >too is an interesting idea, not for short distances (a solution which >has been around for a while) but for long distances, like over five >miles or more. Managing a geographically dispersed ethernet would be >challenging, but the functionality is appealing. I like fiber. I can't wait to see what happens to FDDI as it develops. Fiber optic FDDI will be robust, high speed, and simpler than broadband. I think the ring circumference is around 23 km which will cover a lot of campuses. Speed is 100/200 Mbps. Of course, Pronet-80 is here now and works much the same way FDDI will. I won't repeat the arguments regarding routers versus bridges or introduce a new argument about slow routers versus smart/fast bridges, but I definitely favor routers if we can get some new hardware architectures that will run thousands of packets per second in a multi-protocol environment. Multibus and Interlan Enet cards won't cut it with FDDI and embryonic ISO protocols. Fiber optic token ring is my preference over a fiber optic monolithic Ethernet. You should be excited about managing a geographically dispersed internet, but appalled at the thought of managing a geographically dispersed (large) Ethernet.-- ------------------------------------------------------------------- Kent W. England | Boston University Network & Systems Engineering Group | Information Technology kwe@bu-it.bu.edu internet | 111 Cummington Street itkwe@bostonu BITnet | Boston, MA 02215 harvard!bu-cs!kwe UUCP | (617) 353-2780 -------------------------------------------------------------------
dab@ALLSPICE.LCS.MIT.EDU (12/11/87)
> Now this is something new to me. If you can put them in a >briefcase they must be around 100GHz. That would probably limit the >range to a mile or so. The problem with infrared laser technology is >the atmospheric attenuation of smog, fog, and rain. Sounds like this >new ultra-high freq microwave fills the gap between low freq uwave and >infrared. In the ham radio community for several years there have been devices called Gunnplexers available (I don't know if that's a brand name or a generic name) which are a 10 GHz microwave system for about $200. When they first showed up there were several articles in ham radio magazines descibing how to send video through them, so 10 Mb/sec is probably not too far out of line. Except for maybe the feedhorn (or the dish itself) it would easily fit into a briefcase. The range is limited but I think to line of sight rather than 1 mile. Dave Bridgham
paulf@umunhum.STANFORD.EDU (12/12/87)
In article <8712101810.AA00864@PTT.LCS.MIT.EDU> dab@ALLSPICE.LCS.MIT.EDU writes: > In the ham radio community for several years there have been >devices called Gunnplexers available (I don't know if that's a brand >name or a generic name) which are a 10 GHz microwave system for about >$200. When they first showed up there were several articles in ham >radio magazines descibing how to send video through them, so 10 Mb/sec >is probably not too far out of line. Except for maybe the feedhorn >(or the dish itself) it would easily fit into a briefcase. The range >is limited but I think to line of sight rather than 1 mile. > Dave Bridgham The biggest problem with using GunnPlexers (TM) for digital communications is their lack of linearity. GunnPlexers have both phase and amplitude distortion, and have some real temperature - frequency dependence problems. Despite this, by using FSK or MSK combined with some equalization, one can make an incredibly cheap digital link. We're currently working on a modem that uses temperature stabilized GunnPlexers, and MSK with some simple adaptive equalization, to be used by the 230.4kbps AppleTalk protocol. Look for the article in the March '88 issue of _MacWorld_. -=Paul Flaherty, N9FZX | "The only thing that we've learned from Computer Systems Laboratory |history is that we havn't learned anything Stanford University |from history..." Domain: paulf@shasta.Stanford.EDU| -- William Jennings Bryant
rhorn@infinet.UUCP (Rob Horn) (12/13/87)
I think that these systems are operating in the 23 GHz band. The frequencies between 21.2 and 23.6 GHz are set aside for commercial short-haul communications. This band has 2.4 GHz available, which is a whole lot. The equipment also tends to be relatively cheap, typically under $50K. The antennas that I have seen have been 2-3 foot diameter, giving antenna beam widths of a few degrees. This is more suitcase size than briefcase size. The wider beam width and small antenna make these easy to install. The reliable range at 23 GHz is at most a few miles. The attenuation in air is not too bad, but fog and rain cause significant problems. You have to expect dropouts during heavy rains. The greater the distance, the more you need to worry about these things. Short-haul microwave is a good complement to fiber optic and copper wiring. The installation cost is much lower than physical cable, provided you have line of site between the two ends. FCC licensing is required but usually easy to get. The frequency band is huge, not too heavily used (yet), and the attenuation is such that you can ignore sites that are many miles away. You have to put up with dropouts during heavy rains, so for applications that must work during bad weather they are a bad choice. (Dropouts act like a very overloaded gateway. Traffic can still pass occasionally but lots of packets get lost.) -- Rob Horn UUCP: ...harvard!adelie!infinet!rhorn Snail: Infinet, 40 High St., North Andover, MA (Note: harvard!infinet path is in maps but not working yet)