CNN.com - WiFi activists on free Web crusade - Nov. 29, 2002 (fwd)
camera_lumina at hotmail.com
Sun Dec 1 08:08:17 PST 2002
"Photons are bosons, so they don't interact with each other. Photon
detectors can and usually have anisotropic sensitivity. Sure you can never
beat fiber, but line of sight is free..."
Well, by interfere I meant in the detectors of course. So are you telling me
that two WiFi receivers pointed in different directions will not receive the
same information? I don't think WiFi (IR) is all that directional is it? If
it is, then maybe we CAN have a new LAN segment.
>From: Eugen Leitl <eugen at leitl.org>
>To: Tyler Durden <camera_lumina at hotmail.com>
>CC: <cypherpunks at lne.com>
>Subject: Re: CNN.com - WiFi activists on free Web crusade - Nov. 29, 2002
>Date: Sun, 1 Dec 2002 11:39:37 +0100 (CET)
>On Sat, 30 Nov 2002, Tyler Durden wrote:
> > I just don't see how a single WiFi cloud will be able to scale very far.
> > the WiFi users within "eyeshot" of each other are always going to
> > for bandwidth, no? It'll be just like the old half-duplex 10BaseT copper
>There is limited bandwidth within a cell, if you use omni radiators. How
>high is the limit? No one knows, but you can get 100 MBits/s with current
>ultrabroadband prototypes. Then you have stuff like
>Wireless Transfer Rate of 10 Gbps Possible, NTT says
>Always stretching the boundaries of wireless communications is Japanese
>The company?s most recent accomplishment was achieving a peak data
>transfer rate of 2.5 Gbps, breaking the recorded rate of 1 Gbps; NTT
>researchers now believe they will eventually break the 10 Gbps barrier.
>As the airwaves become increasingly congested, exploring uncharted
>airwaves could pay NTT high dividends in the future.
>As an article in ComputerWire explains, NTT's solution has been to harness
>new electronic and optical technologies to access the empty 120 GHz radio
>band. Optical systems are used to generate the original signal which is
>passed, using amplitude modulation to a 300 GHz photodiode, which creates
>an electrical signal that is passed to a direct slot antenna. The key to
>the whole process is the 300 GHz photodiode, which harnesses optical
>technology, in this case the Lithium Niobate substrate originally designed
>for light switching, to the business of generating an electrical signal.
>Commercial viability is still a ways off. At the moment, the sustained
>1.25 Gbps signal generates a range of only 50 cm. Nevertheless, as demand
>for wireless services out strips available spectrum, NTT will no doubt
>find itself swarmed by partners and competitors alike.
>Then, you have funky stuff like antenna arrays. People have started
>tinkering on MEMS galvanometers lately, which would allow to use line of
>sight lasers across free space without need for manual alignment; possibly
>dynamically tracking moving objects.
> > LANs. And I still don't understand how a WiFi router will help you...if
>Current routers use an omni to cover local area, and directional aeries to
>create a mesh with their peers. Directional aerials for long-range
>connections have both a longer range and are less sensitive to crosstalk
>from the omni.
> > different Layer2 LANs overlap in space at all, they'll interfere with
> > other optically even if they are on different segments. (With copper you
>Photons are bosons, so they don't interact with each other. Photon
>detectors can and usually have anisotropic sensitivity. Sure you can never
>beat fiber, but line of sight is free...
> > didn't even have this problem.) Thus, aren't you stuck with zillions o
> > little WiFi islands that must not overlap without things getting very
> > As for service providers not wanting freeloaders, I'd point out that DSL
> > "cares" much less....the DSL connection is mapped over ATM and is
>If I have a P2P infrastructure run on end-user owned hardware (little
>boxes glued to windowpanes) across an urban area with ~100 MBps/cell there
>is not all that much use for an ISP.
>Things only become difficult if you want to crosslink cities. Here you
>have to use fiber, or similiar.
> > a dedicated connection to a router port, with fixed bandwidth in either
> > direction. Whether that port is processing lots of freeloader packets or
> > idle packets from a single dedicated user shouldn't matter much.
> > Uh, but now that I think of it ATM does allow for some oversubscription,
> > in order to maximize the conection between the DSLAM and the ATM switch
> > that's in front of the router (it might be in thesame box as the router,
> > know!), maybe they'l discourage freeloading. BUT, DSL companies have
> > touting that they're very happy for you to put a home-based LAN on your
> > of the connection (Cable Modem providers don't normally like that).
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