phillip@bartal.CRLABS.COM (Phillip M. Vogel) (10/25/90)
I read in the Wall Street Journal (Tue, Oct.23 1990) that Motorola is announcing ---begin unauthorized quote from WSJ--- "....a new method for sending data within buildings using digital radio transmission......based on several components, including an omnidirectional antenna, a miniaturized digital transmitter and receiver (about the size of a Western-style belt buckle) and software........These components would operate in the little-used frequency band of 18 gigahertz and are designed to allow networks of personal computers and minicomputers to transmit data to one another at up to 15 million bits per second." ---end unauthorized quote from WSJ--- Anybody know anything about this? I'd particularly like to know who to contact at Motorola to get further information. If anyone from Motorola is out there, please give me a call. Phillip -- Phillip M. Vogel, President | 1-800-631-2524 ext. 272 Bartal Design Group, Inc. Englewood, NJ | (201)567-1343 FAX:(201)568-2891 UUCP: pyrnj!bartal!phillip | Domain: phillip@bartal.crlabs.com
kwe@buit13.bu.edu (Kent England) (10/25/90)
In article <418@bartal.CRLABS.COM> phillip@bartal.crlabs.com (Phillip M. Vogel) writes: > >---begin unauthorized quote from WSJ--- > "....a new method for sending data within buildings using >digital radio transmission......based on several components, >including an omnidirectional antenna, a miniaturized digital >transmitter and receiver You are describing one of several varieties of wireless LAN technology that will be coming to market in the near future. Unlike older technologies that sent radio signals on power lines or used infrared, these new technologies are based on a type of radio modulation invented many years ago for the military: spread spectrum technology. Spread spectrum involves spreading a "narrow" bandwidth signal across a much larger spectrum using pseudo-random number sequences known to both transmitter and receiver. The spectrum spreading improves signal to noise dramatically (if done right) in the presence of multi-path, which is a severe problem at these frequencies in the steel-lattice buildings most of us work in. But beware of corner cutting vendors whose spectrum spreading is just within FCC definitions. Not all implementations are created equal. Look for at least 10:1 spreading. More is better, but costly. You still have to install wire and repeater units, so you don't get rid of upfront costs altogether. What you will eliminate is the necessity of "installing" new nodes. The headache you get, of course, is you will have to look to find out who is using your radio LAN and you won't know til you look how crowded it is getting. And like cellular phones, the spectrum will get crowded and will be regulated eventually, so your systems are somewhat vulnerable to future interference. Remember the early cordless phones? I think we will have to build a lot of these systems before we can find out how many of these wireless LANs can share the same bandwidth space before the noise floor gets too high. Does anyone have an test data for how many wireless LANs can co-exist independently in the ether? --Kent England Boston University
henry@zoo.toronto.edu (Henry Spencer) (10/26/90)
In article <67070@bu.edu.bu.edu> kwe@buit13.bu.edu (Kent England) writes: >... The headache you get, of >course, is you will have to look to find out who is using your radio >LAN... Including that van parked out in front with your competitor's name on it! Nobody who has any concern for privacy or confidentiality should even be considering wireless LANs unless they plan to encrypt all traffic. -- The type syntax for C is essentially | Henry Spencer at U of Toronto Zoology unparsable. --Rob Pike | henry@zoo.toronto.edu utzoo!henry
wiml@milton.u.washington.edu (William Lewis) (10/29/90)
In article <418@bartal.CRLABS.COM> phillip@bartal.crlabs.com (Phillip M. Vogel) writes: >---begin unauthorized quote from WSJ--- > "....a new method for sending data within buildings using >digital radio transmission......based on several components, >including an omnidirectional antenna, a miniaturized digital >transmitter and receiver Sure hope nobody uses telnet or FTP on a LAN like this. It sounds *far* too easy to eavesdrop on. I hope I'm missing something here ... whst is it? -- wiml@milton.acs.washington.edu Seattle, Washington (William Lewis) | 47 41' 15" N 122 42' 58" W "These 2 cents will cost the net thousands upon thousands of dollars to send everywhere. Are you sure you want to do this?"
kwe@buit13.bu.edu (Kent England) (10/30/90)
In article <1990Oct26.155442.27053@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >In article <67070@bu.edu.bu.edu> kwe@buit13.bu.edu (Kent England) writes: >>... The headache you get, of >>course, is you will have to look to find out who is using your radio >>LAN... > >Including that van parked out in front with your competitor's name on it! >Nobody who has any concern for privacy or confidentiality should even be >considering wireless LANs unless they plan to encrypt all traffic. >-- Henry, that's a good point and I failed to note that spread spectrum has a certain degree of security that it gains from the pseudo-random encoding that is used to spread the spectrum. An observation of a deterministic pseudo-random number sequence does not help much in determining the algorithm and seed used to generate the PSN sequence. Without the PSN sequence, the actual data cannot be extracted from the spread spectrum digital sequence. Spreading the spectrum makes the signal hard to jam and pseudo-random encoding sequences make the actual data difficult to decipher, both features initially attracted the military development. A receiver has to have the pseudo-random number algorithm (easy), seed (hard), and a good idea of the time (a little tricky) to decipher a spread spectrum signal. You might find spread spectrum technology to be sufficiently secure for your purposes, although I would recommend Kerberos or other robust authentication mechanism for access to your wireless LAN and for distributing information like seed number changes to your authorized users. Thanks for pointing out this problem area. It is something that potential users will have to satisfy themselves about. --Kent
pat@hprnd.rose.hp.com (Pat Thaler) (10/30/90)
> >---begin unauthorized quote from WSJ--- > > "....a new method for sending data within buildings using > >digital radio transmission......based on several components, > >including an omnidirectional antenna, a miniaturized digital > >transmitter and receiver > > Sure hope nobody uses telnet or FTP on a LAN like this. It sounds > *far* too easy to eavesdrop on. I hope I'm missing something here ... > whst is it? > What you are missing is part of the nature of spread spectrum. Rather than transmitting on one frequency, the signal hops around between several frequencies at a very fast rate. To receive the signal, the receiver has to know the pattern. A receiver listening to just one frequency will just hear noise. In theory, several networks could operate in the same spectrum area with different codes without interfering with each other. This seems to eliminate the threat of a casual listener eavesdropping. I'm not sure how hard it would be for a determined eavesdropper to crack by trying different patterns or such. I would agree with much of what Kent posted. I believe that spread spectrum is a secondary use on much of the spectrum space alloted to it and as such must not interfere with the primary use. The advangages are: for low power spread spectrum in certain bands you don't need a site license from the FCC, it is more immune to noise, it can't be casually overheard. Pat Thaler
macklin@garnet.berkeley.edu (Macklin Burnham) (10/31/90)
Spread spectrum frequency was originally developed by the military for secure, jam-proof battlefield communications, I believe. I have an article in front of me (Network World, 10/29) on the Motorola wireless lan offering, and it seems that they are not using spread spectrum (man, that's hard to say!) technology, but rather miniaturized low-power radio in the 18GHz range. They call it Wireless In-building Network, and I quote: "Motorola said WIN provides data security through the use of low-power 18-GHz signals, which lose strength if they pass through walls or doors. This means that one WIN is essentially invisible to another system that is more than 120 feet away." Hmmmmm. Mack Burnham
henry@zoo.toronto.edu (Henry Spencer) (10/31/90)
In article <67319@bu.edu.bu.edu> kwe@buit13.bu.edu (Kent England) writes: >An observation of a deterministic pseudo-random number sequence does not >help much in determining the algorithm and seed used to generate the >PSN sequence... Sorry, not true. Determining the algorithm by observation is indeed hard. However, the algorithm is usually a property of the system design, i.e. it is fixed and can in principle be determined by examining another copy of the system. Given the algorithm, determining the seed from the sequence often is no big deal: methods for cryptanalysis of the more common types of pseudorandom-number generators have been published. >... You might find spread spectrum >technology to be sufficiently secure for your purposes... Relying on a commercially-available spread-spectrum system for your security is foolish, I'm afraid. It will stop a casual eavesdropper but will be only a minor nuisance to a sophisticated industrial spy. -- "I don't *want* to be normal!" | Henry Spencer at U of Toronto Zoology "Not to worry." | henry@zoo.toronto.edu utzoo!henry
Chris.Rusbridge@levels.sait.edu.au (11/02/90)
In article <1990Oct26.155442.27053@zoo.toronto.edu>, henry@zoo.toronto.edu (Henry Spencer) writes: >>course, is you will have to look to find out who is using your radio >>LAN... > > Including that van parked out in front with your competitor's name on it! > Nobody who has any concern for privacy or confidentiality should even be > considering wireless LANs unless they plan to encrypt all traffic. Since that van can probably pick up the screen on your terminal, perhaps you should be considering tempest as well. Where does one stop? Chris Rusbridge Academic Computing Service Manager, SA Institute of Technology AARNet: Chris.Rusbridge@sait.edu.au Phone: +61 8 343 3098 Fax: +61 8 349 4213 Post: The Levels, SA 5095 Australia