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802.11 vs. 3G For Mobile Access
bobdole34 writes: "A new way to give us fast mobile net access spells further trouble for 3G.Imagine being able to surf the net at speeds faster than DSL from anywhere, at any time - you could watch a live video webcast while waiting for the bus, email photos to your friends while sitting in the park, or download the MP3 of the song that's playing in the pub before it finishes. I smelled vapour until I saw a demo of MeshNetworks at 802.11Planet in Philly."
This article, at UltraWideband Planet suggest that 802.11 is doomed. Perhaps most interestingly, the Ultrawideband site is from the same people that offer 802.11-Planet, Internet.com.
Your Cisco teacher was referring to fully meshed networks and she was correct. Fully meshed networks, typically based on point-to-point or frame-relay connections such as those that would be used in corporate environments, do not scale well. They very rapidly become far too cumbersome and expensive to maintain due to the fact that these types of networks grow exponentially.
This 802.11 solution would not be a fully meshed network but, rather a series of partially meshed networks which would make them smaller and more manageable. Furthermore, these networks would have the ability to develop new interconnections automatically and dynamically so the management aspect would not be an issue. Also, due to the use of wireless for these connections, rather than physical connections used by point-to-point and frame-relay, cost would not be nearly as big an issue.
In other words, your teacher was correct but, those rules do not apply in this scenario.
this clip is from Business 2.0:
<clip> Ultimately, however, 3G and Wi-Fi should be able to coexist. "The technology is actually very complimentary, because they are not truly competitive technologies," King says. "I expect that mobile carriers will purchase some Wi-Fi providers, and we'll start to see some integration." </clip>
Also, is a collection of links on mobile routing protocols, and mesh routing protocols that were originally designed for wired backbone links.
The Mesh Networks Inc protocols are proprietary.
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.11 power management is to put the radio in sleep mode (and run the sleep protocol with the AP). This has not been a competitive focal point, but vendors are starting to improve.
.11 radios that are just starting to hit retail channels can operate on both the 11b and 11a bands and with both the 11b and a/g OFDM codecs. The prices for 11a nic cards is under $100 now (79?) and the a/b/g nic cards won't be far behind.
They are a byproduct of military-funded tactical
radio R&D. There is an emphasis onself-organizing topology and route discovery. If every soldier and vehicle is lugging a radio, then the network
has a good chance of continuing to operate even if parts of it are destroyed.
This kind of mesh does have some pathology.Take some number, say 10, of nodes placed in a straight
line. You are at one end of the line and the internet ISP is at the other end. And you have
10 wireless hops between you and the internet. And the people in the middle of the line may not be really happy with you either.
There are non-proprietary approches. Check out the ietf MANET working group at
http://www.ietf.org.html.charters/manet-chart
There are numerous university projects. Try Google(mesh network & university)
or Google(mobile network & university).
There have been numerous failed startup company attempts at mesh networks. One approach that I found very appealing used a self-organizing mesh
that organized itself into rooted tree structures.
The internal tree branches served as backhaul connections to the internet. The leaves represent the clients/users. The internal nodes are not mobile. They are devices to be installed on utility poles or public access locations. They find one another and create an uplink/downlink
infrastructure where uplink means a path to the ISP or other wired infrastructure and downlink
means to the client. I liked this approach because it builds a predictible structure that
can be analyzed and because the routing procedures
within the internal nodes are a lot simpler
than in the completely unconstrained mesh network.
The tree-like organization also seems to avoid
another conceptual problem with the fully
unconstrained network which is bandwidth sharing.
If you are a client in a full mesh, your node
must accept routing traffic from other nodes.
Thus a goodish portion of your bandwidth and battery power may be consumed by traffic going
through your client - but it's not your traffic.
I'd guess that most people would not want to act
as a router and be draining power pretty much
fulltime. Makes more sense to have a wireless
self-organizing infrastructure that can provide
bandwidth to clients that cruise within range.
There were a few misleading comments about power
in earlier emails. Cell phones typical draw
about 2 watts when transmitting. That exceeds
the current capacity of the battery. They actually charge a capacitor from the battery between time slots and drain the capacitor during transmission. 802.11 devices have lower peak current drains, and they continue to get better. The most important technique in
Next-generation
I think it is important to point out that 11b only has 3 channels to operate in. That doesn't give you much routing diversity when you need a lot of overlapping transmitters to create a useful (and thus redundant) mesh. But when you add 11a and can use the higher bandwidth ofdm codec in either the 11a bands or in the 11b bands (where they call it 11g), then you have more than a dozen channels that can be operating simultaneously. It seems obvious to me that this kind of channel diversity will be needed to successfully deploy a good mesh.