Beta

×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Stanford Team Tries For Better Wi-Fi In Crowded Buildings

samzenpus posted about 5 months ago | from the greased-lightning dept.

Wireless Networking 43

alphadogg writes "Having lots of Wi-Fi networks packed into a condominium or apartment building can hurt everyone's wireless performance, but Stanford University researchers say they've found a way to turn crowding into an advantage. In a dorm on the Stanford campus, they're building a single, dense Wi-Fi infrastructure that each resident can use and manage like their own private network. That means the shared system, called BeHop, can be centrally managed for maximum performance and efficiency while users still assign their own SSIDs, passwords and other settings. The Stanford project is making this happen with inexpensive, consumer-grade access points and SDN (software-defined networking)."

cancel ×

43 comments

Sorry! There are no comments related to the filter you selected.

LOL (-1)

Anonymous Coward | about 5 months ago | (#46425463)

Do you hate beta? Do you hate Dice.com? Do you hate the technically-ignorant newfags that are infesting Slashdot? Do you hate niggers, jews and fags? Well don't fret! Join SoylentNews! A site by straight, white nerds for straight, white nerds!

We have also recently received the highly coveted "5 Swastikas" rating from the KKK for our commitment to the furtherance of the white race. Heil Soylent!

You are a troll (-1)

Anonymous Coward | about 5 months ago | (#46425513)

The Swastika was used by the German National SOCIALIST party. The KKK is a supporter of old fashioned Southern american values, including freedoms, free market capitalism, among other things.... Needless to say, those political parties are incompatible.

I have not seen anything on soylentnews indicating a push for aryan supremecy.

Re:You are a troll (-1)

Anonymous Coward | about 5 months ago | (#46425549)

The Swastika was used by the German National SOCIALIST party.

So you believe that North Korea is a democracy because it calls itself the "Democratic People's Republic of Korea"? Are you retarded by choice or because of the inbreeding between your grandpa and your mom?

Re:You are a troll (-1)

Anonymous Coward | about 5 months ago | (#46426911)

Socialism != National Socialism
Socialism != Communism

Re:LOL (1)

buswolley (591500) | about 5 months ago | (#46425559)

Not an authorized Soylenter

Re:LOL (1)

Anonymous Coward | about 5 months ago | (#46426693)

Ethanol-fueled, is that you? :)

and how do they track users across muilt units? (3, Interesting)

Joe_Dragon (2206452) | about 5 months ago | (#46425467)

also what about stuff like file shearing and other stuff that the cops only look at the IP and not that real end user.

Re:and how do they track users across muilt units? (1)

Vesvvi (1501135) | about 5 months ago | (#46425499)

I assume this is something like Ubiquiti's "zero-handoff" system, where the wireless APs coordinate to form an virtual network that spans across all the APs. I'm not a networking pro, but I guess you could say it's like the opposite of a VLAN? Although based on the article, it sounds like there are effectively VLANs running on their mesh to partition it into per-user virtualized segments. In that situation, there is nothing that prevents you from having a static or even public IP.

Re:and how do they track users across muilt units? (5, Funny)

grcumb (781340) | about 5 months ago | (#46425893)

also what about stuff like file shearing...

Well, typically, you start by grabbing the file by its strings, give 'em a twist and get it on its back. Then you lift the tail[*] such that all the loose bits run off onto the floor as you make your first pass. Some prefer Occam's Razor when shearing data, but I find Hanlon's Razor works, too.

-----------
[*] I find that tail -n 100 is enough to get a decent grip, but it really depends on the size of the RAM....

Re:and how do they track users across muilt units? (2)

Schrockwell (867776) | about 5 months ago | (#46426029)

On a university network, every networked device is usually registered by its MAC address, which is tied to that student's school-wide login for tracking purposes. The university already knows everything you do. I assume the same would be true over this public WiFi architecture.

I tried to get around this one time by spoofing my MAC with one from a library computer. THAT didn't go over so well. Since I was using the personal WiFi in my dorm room (stupid, I know), they knew exactly which network spigot it was coming from. Alarms went off all over their monitoring tools. Luckily I had a friend in IT who saw it, laughed, and told me to not do it again.

Re:and how do they track users across muilt units? (1)

AK Marc (707885) | about 5 months ago | (#46426413)

I've set up static IPs (or reserved DHCP) across hundreds of APs in multiple buildings. Roam all you want from floor to floor, and building to building, and keep your single IP. Oh, and send out another SSID for your neighbor, and he can be on a whole different network, and roam across all the same APs and keep his IP. Hell, it's possible to have one SSID per person, with hundreds of individual people/SSIDs on a single AP, and have all those SSIDs available on all APs in the cluster.

You are thinking small and "old way".

Re:and how do they track users across muilt units? (1)

AmiMoJo (196126) | about 5 months ago | (#46426989)

It's actually the perfect defence against speculative copyright infringement claims. "We don't have that information."

Single network redistribution (1)

relisher (2955441) | about 5 months ago | (#46425471)

Doesn't this just mean that all of the networks have to be put under the control of a singe entity, and then redistributed amont those living in the condo?

Re:Single network redistribution (1)

Joe_Dragon (2206452) | about 5 months ago | (#46425537)

Comcast would love that and yes online Sunday ticket does eat up a big part of your cap and don't even think about installing an dish.

Yes. (1)

khasim (1285) | about 5 months ago | (#46425581)

All of the WiFi routers (access points) would be under central control for things like assigning them to specific channels.

But the "owner" (student) of the router will get to set things like SSID and QoS and such.

Re:Single network redistribution (1)

LiENUS (207736) | about 5 months ago | (#46425591)

not at all. you would plug your router that is compatible with this system into your cable modem and into a seperate port for the building network or whatever and the software defined network would route all of your vlan traffic back to your own router for it to travel out your cable modem, any traffic going to your router but for a different vlan would hit the building network and go to whoevers home router it was for.

talk about good reception & or crowd pleasers (-1)

Anonymous Coward | about 5 months ago | (#46425545)

this kid's on fire http://youtu.be/txT1TFuYt3w

VPN (1)

Dan East (318230) | about 5 months ago | (#46425653)

VPN called. It wants its acronym back.

Re:VPN (0)

Anonymous Coward | about 5 months ago | (#46425881)

Sort of. A VPN makes a single virtual network out of two separate networks. While these would be virtual networks, they wouldn't necessarily be linked to any other networks. "Virtual Subnetworks" would seem like a better term. I've also seen them called "Supplementary Networks."

How efficient is WiFi when crowded? (1)

timeOday (582209) | about 5 months ago | (#46425765)

Let's say you live in an apartment building and you can see 16 different SSIDs. Is it slow because there's a lot of data in total being transferred, or does CSMA just collapse (gridlock) so hardly anybody is getting anything? It seems like back when ethernet was actually used as a shared medium (hubs) throughput was good up to about 85% and then it would just die.

Re:How efficient is WiFi when crowded? (1)

khasim (1285) | about 5 months ago | (#46425803)

Is it slow because there's a lot of data in total being transferred, or does CSMA just collapse (gridlock) so hardly anybody is getting anything?

Usually it is because of data. But not necessarily that simple.

You can see 16 SSID's but if no one is transmitting traffic right then then there shouldn't be a problem.

If someone else is transmitting data then it depends whether he is on the same channel as you (or one that overlaps yours). With the 2.4GHz range there are only 3 channels that don't conflict/overlap each other. 1, 6 and 11. If he's not on your channel then there shouldn't be a problem.

Finally, if he is transmitting and he is on your channel then the issue is whether he's using enough broadcast power to cause problems with your communications. Basically, a WiFi channel is the same as a bunch of people sitting in a room and yelling whenever they want something. The more broadcast power, the louder he's yelling. And most people crank their systems up to max power if that's an option.

There is also another possibility. Anything that uses electricity can generate radio frequency "noise". Such as a microwave oven. Which can also cause problems with WiFi transmission.

Re:How efficient is WiFi when crowded? (3, Informative)

Guspaz (556486) | about 5 months ago | (#46425813)

2.4ghz is still usable with 16 networks in the same area, but it's not a great experience. There are only three non-overlapping bands in the 2.4 GHz band, so you can see how there can be a rather lot of congestion.

The 5.8 GHz band, on the other hand, wouldn't have nearly as much of an issue. 802.11n in the 5.8GHz band devices can use 8 non-overlapping channels, significantly reducing the amount of interference.

802.11ac is kind of in a wierd spot. It's really 40MHz per channel minimum (twice the minimum for 802.11g or 802.11n), but many devices also support a whole whack of new frequencies that require the use of DFS to avoid interfering with radar (basically if the router detects radar on the channel, it blacklists the channel for a set amount of time and switches to another channel). That brings the total up to a possible 12 channels, even though they're twice as wide...

802.11ac also supports beam forming, which enables multiple simultaneous transmissions to happen on the same frequency at the same time without interfering. I believe that's more targeted at handling more users on a single network rather than letting multiple networks co-exist, though.

Beamforming (0)

Anonymous Coward | about 5 months ago | (#46426803)

Beamforming in the wifi world has existed on Atheros chipsets (which nearly everyone uses) since 802.11n.
It has to do with controlling the signal's quality to a specific client - it doesnt allow multiple clients to occupy the airwaves at the same time. Wifi is and remains a shared medium.

Re:How efficient is WiFi when crowded? (1)

AmiMoJo (196126) | about 5 months ago | (#46427017)

2 networks on the same channel can be unusable if one is saturating it (big download, BitTorrent etc.). If you are lucky the two will at least share the channel and both will get some bandwidth, but in the event that the one being saturation can't hear the other but is still interfering with it you are SOL. Typically it looks like this:

A------u------B

A and B are the access points, u is the user in the middle. A and B are too far apart to hear each other, but if A is transmitting it will interfere with transmissions from B being received by the user. B can't hear A either so has no idea what happened, until the user's laptop fails to respond for some time and it tries to re-send.

5GHz is clear for now but will get worse. How much worse it gets depends on a lot of things, not least being how good the walls in buildings were you live are at blocking that frequency. New buildings should be designed to keep wifi in.

Re:How efficient is WiFi when crowded? (2)

niftymitch (1625721) | about 5 months ago | (#46425879)

Let's say you live in an apartment building and you can see 16 different SSIDs. Is it slow because .....snip...

Someone needs to make a reference to the Aloha Protocol (http://en.wikipedia.org/wiki/ALOHAnet).
Multiple routers and multiple end points sharing a limited bandwidth shared commons
is just darn difficult.

I do hope Stanford makes this work because dense living just happens.

More and more work places are getting to be "dorm living" on caffeine.
Old folks homes and retirement communities are just around the corner
for lots of us and the bandwidth needed for Gramps and Gma to browse
all the photos and videos of kids and food boggles the mind.

Re:How efficient is WiFi when crowded? (1)

Solandri (704621) | about 5 months ago | (#46426541)

Let's say you live in an apartment building and you can see 16 different SSIDs. Is it slow because there's a lot of data in total being transferred, or does CSMA just collapse (gridlock) so hardly anybody is getting anything?

Unfortunately, the way 802.11b/g were made, they're essentially FDMA. You assign channels to certain frequencies. If two routers happen to use the same frequency, they stomp over each other. (n and ac may do the same thing, I haven't read up on those yet.)

If they'd gone with something like CDMA or OFDMA (orthogonal FDMA), we wouldn't be having this problem. Those two assign orthogonal codes or frequencies to each device. Their transmissions can stomp over each other all day long and the receiver can still tell them apart. Bandwidth scales automatically with number of devices. If you're the only device, you get most of the bandwidth to yourself. If there are lots of other devices transmitting, they essentially increase the noise floor for your signal, and your bandwidth scales down accordingly and automatically. That's the reason these two coding schemes account for the vast majority of 3G and 4G transmission standards on CDMA, GSM (most 3G and 3.5G GSM uses wideband CDMA), and LTE networks.

Incidentally, I ran across a failure mode for CSMA just this weekend. My sister called me over because she couldn't get her TV to connect to her wireless network. It turned out both her router and her neighbor's router were transmitting on the same channel despite their channel selection being in auto mode. The routers were far enough from each other that they weren't picking up each others' transmissions. Her TV however happened to be just about in the middle of the two routers, and was getting a weak but equal strength signal from both. I guess other wifi networks in the neighborhood were causing those two routers to automatically select channel 11.

Re:How efficient is WiFi when crowded? (1)

timeOday (582209) | about 5 months ago | (#46428431)

I am really glad this came up, because my WiFi at my house hasn't been working as well lately, and it gives me something to try... maybe manually placing it on a different channel will help.

Dorms (1)

wiredlogic (135348) | about 5 months ago | (#46425769)

It's a shame the kids these days can't be bothered to plug a computer into the Ethernet drops that were installed in their rooms 20 years ago.

Re:Dorms (0)

Anonymous Coward | about 5 months ago | (#46425871)

No one wants to use 10BASE-T at 10 Mbps across Cat3 cable installed in 1994.

Re:Dorms (1)

Anonymous Coward | about 5 months ago | (#46427123)

That still might be faster than crowded 802.11g (possibly even "n")...

Re:Dorms (2)

Voyager529 (1363959) | about 5 months ago | (#46428385)

It's a shame the kids these days can't be bothered to plug a computer into the Ethernet drops that were installed in their rooms 20 years ago.

To be fair, plenty of the anorexic laptops being sold these days have shed the ethernet port (obnoxiously, most of the sub-$500 laptops only have 10/100 NICs...), and phones and tablets are wi-fi or cellular only; wired isn't even an option for them.

Software Defined Networking = Telephony (2)

Animats (122034) | about 5 months ago | (#46425771)

"Software Defined Networking", as Stanford uses the term, means a centrally controlled virtual circuit switching system. Every time someone makes a "call" (a new IP/port IP/port tuple), the first packet is routed to Master Control, which decides if they get to make the call, logs the call, decides whether the call gets wiretapped or filtered, and chooses the priority given to the call. All the routers involved are then issued instructions from Master Control on how to route that call.

(Yeah, they don't use the term "call". But that's what it is, really.) Goodbye, "net neutrality". Goodbye, flat rate billing. Goodbye, distributed control. This puts everything you do on the Internet under central control and makes it billable.

Re:Software Defined Networking = Telephony (2, Insightful)

Anonymous Coward | about 5 months ago | (#46425829)

Your upstream provider can already do all of those things to you. They don't control where your packet goes upstream from you, but if your local ISP chooses to shut you out, the upstream folks will never see your packet in the first place. (The only difficult one is choosing the priority of the packet. Your local ISP can't raise the priority of your packet, but you bet they can lower it as much as they want by simply not sending it.)

The fact that ISPs don't do that is based on tradition and the threats of competition and regulation, not on any technical limitations.

Re:Software Defined Networking = Telephony (1)

cdwiegand (2267) | about 5 months ago | (#46431891)

Sounds just like any firewall, so what's the diff?

Ok (0)

Anonymous Coward | about 5 months ago | (#46425781)

Who will "centrally manage" it in the wild? Seems the channel selection needs extension...

Re:Ok (1)

guruevi (827432) | about 5 months ago | (#46429463)

Typically in a housing unit (like an apartment) the owners would do this. There have been some that started to do this, offer network services to their residents for free or for a premium. This saves them money by not having different cable installers trampling over the last cable installer (which are all from the same company off course because you don't have much choice) and damaging existing infrastructure, it also saves them complaints from one system interfering with the other and less effort adhering to laws that allow everyone to have their own dish/cable/phone line of choice.

One of the apartment complexes I lived in installed a 100/20 Mbps line with a contracted really large dish for TV and distributed phone, internet and tv to all units for $20/month. TWC could suck it as the majority of the residents stepped over.

pCells (1)

Ken_g6 (775014) | about 5 months ago | (#46425809)

Isn't there some way they could create pCells [slashdot.org] around each device, so nobody would interfere with anyone else?

The next question is, could that be done in each individual's router(s), or does it require the collective network described here?

Re:pCells (0)

Anonymous Coward | about 5 months ago | (#46427139)

Per Cringely, "pCell is only as good as the Linux it runs on" (with particular reference to security):

http://www.cringely.com/2014/03/06/pcell-good-linux-runs/

Re:pCells (1)

Ken_g6 (775014) | about 5 months ago | (#46427631)

I'm not referring to picocells for 4G, exactly.

1. I'm referencing the specific pCell technology I linked to, which apparently creates pockets of constructive interference around devices connected to the pCell, and generally destructive interference elsewhere.
2. I'm suggesting using similar technology, not to run 4G, but to run WiFi. It seems like it should reduce interference between individuals' routers, without requiring one big-brother network.

Re:pCells (1)

dumky2 (2610695) | about 5 months ago | (#46430033)

Doesn't the security argument apply equally to pCell and to BeHop (which is based on OpenWRT according to the article)?

Hasn't this been done before? (0)

Anonymous Coward | about 5 months ago | (#46425891)

I read about this concept some time ago.

Check out https://github.com/lalithsuresh/odin

Warning: sarcasm ahead! (1)

soccerisgod (585710) | about 5 months ago | (#46426259)

Love how this article gives so much detail. It was easy to form an opinion on the usefulness of... this... thing... whatever it is.

SDN = "yet another layer of indirection" (0)

Anonymous Coward | about 5 months ago | (#46429513)

I think this "virtualization" craze is all mildly amusing. What if users insisted on baking needed features from the start into their platforms instead of tolerating layering of hacks upon hacks?

Computers within computers, Q-in-Q-in-Q ad absurdity. It all adds up in unnecessary management and product costs.

Legions of folk talking "secure networks" operating under assumption cyberspace castle defense has or will ever become a sane strategy.

What if the operating system out of the box guaranteed an isolated execution environment for applications allowing suspension, migration and fault tolerance for the application and environmental dependencies? Would people still insist on stringing up virtual computers within computers all over the place?

What if migration of applications also updated naming resources and provided for seamless network handover? Would people still insist on stringing up tunnels and virtual lans?

Things like VPNs/tunnels are convenient I get it I get why people use them today yet if you get rid of the constraints to underlying technology which make them useful (Lack of address space, lack of end to end security, lack of mobility) then VPNs become rather pointless.

In this specific case the stated problem was availability of spectrum. The answer is 802. things with "n" and "ac" after them. Screwing with very limited real channel space in ISM band is pointless compared with modern beam forming and seamless roaming is free on Ethernet networks.

I suspect the real motivation has more to do with centralized control and monitoring of the network by the University. The fact that this is at all possible or useful is itself due to failure to universally deploy proper end to end security.

Check for New Comments
Slashdot Login

Need an Account?

Forgot your password?
or Connect with...

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>