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Homemade VoIP Network Over Wi-Fi Routers

timothy posted more than 6 years ago | from the warms-the-cochleas-of-the-heart dept.

Communications 71

AnInkle writes "A blogger on The Tech Report details his research and testing of wireless voice communication options for remote mountainous villages in rural undeveloped areas. The home-built project involves open-source software, low-cost wireless routers, solar power, mesh networking, unlicensed radio frequencies and VoIP technology. Although his research began several months ago, he has concluded the first stage of testing and is preparing to move near one of the sites where he hopes to eventually install the final functional network. Anyone with experience or ideas on the subject is invited to offer input and advice."

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Urban Networks... (3, Insightful)

PC and Sony Fanboy (1248258) | more than 6 years ago | (#23390052)

Wouldn't this be great! You could use your networking skills to setup a private, free telephone system. And, if it was encrypted, no one could snoop in on it... and if it was in an urban environment... Hmmm....

Re:Urban Networks... (4, Funny)

William Robinson (875390) | more than 6 years ago | (#23390200)

And, if it was encrypted, no one could snoop in on it

Hold your horses, Osama, it's not perfect yet :)

Re:Urban Networks... (2, Insightful)

Catbeller (118204) | more than 6 years ago | (#23394306)

Shrug. Killing the joke, but:

Al Qaeda NEVER uses electronic communications. They communicate face to face, always. No cell phones, no computers, no GPS, no mail, no land lines, nada. This is why I scream madly at every "homeland" security citation about encryption and internet use. They don't use anything of the sort. That's why we can't find them. That's why they got away. We're building a surveillance state that has no way of watching people riding horses in mountains, but does a bang-up job in keeping us from, oh, building a free hippyphone system using wifi.

Re:Urban Networks... (2, Insightful)

Dan541 (1032000) | more than 6 years ago | (#23396708)

Don't tell me you Actually believe the Anti-Terrorism laws are to do with terrorists.

Re:Urban Networks... (1)

StudMuffin (167171) | more than 6 years ago | (#23400942)

You sure seem *awfully* familiar with the internal working of Al Qaeda.

*waves to the nice men reading all our email in Langley, Virginia* :-)

Re:Urban Networks... (4, Interesting)

Opportunist (166417) | more than 6 years ago | (#23390286)

Zero chance. I'd even deem it unlikely that the original project survives for long. Telcos are missing out revenue when you communicate for free, the feds owe them one for the wiretapping thing, so I expect a law soon against this. Because of ... because of ... national security or whatever fits.

Re:Urban Networks... (1)

MichaelSmith (789609) | more than 6 years ago | (#23390308)

Zero chance. I'd even deem it unlikely that the original project survives for long. Telcos are missing out revenue when you communicate for free, the feds owe them one for the wiretapping thing, so I expect a law soon against this. Because of ... because of ... national security or whatever fits.
Cell phones should be able to communicate point to point over 100 metres or so. For some reason no phone manufacturer has thought to introduce this feature.

Re:Urban Networks... (3, Interesting)

jamesh (87723) | more than 6 years ago | (#23390364)

There are (still?) cell phones with DECT (household grade cordless phone technology) built in. I always thought this would be a much better alternative to a cell phone with wifi built in to accomplish VoIP. DECT is pretty lightweight, so do VoIP to the DECT base station, then DECT to the phone. When you are in range of the DECT base station (eg at your house) you'd make calls via that instead of the more expensive cell network.

Not sure why this never took off... could have something to do with the less money that the cell providers would make.

Re:Urban Networks... (2, Insightful)

Spokehedz (599285) | more than 6 years ago | (#23390560)

"Not sure why this never took off... could have something to do with the less money that the cell providers would make."

Gee, you think?

Re:Urban Networks... (1)

sumdumass (711423) | more than 6 years ago | (#23402940)

It is probably more like there is no signal privacy and very limited access control with cordless phone tech that would sometimes vary from manufacturer to manufacturer and the inability for most cordless phones to carry a signal to more then one handset at a time. Things have changed but not really since wifi has taken off.

Without a lot of the security and stuff that WIFI offers, it could generally be possible to just walk down the street and connect to someone else's land line through their cordless phone and make all the toll calls on their dime. With VoIP and the WIFI, it is more of a matter of knowing if you have access to the network (open or protected) and if the phone checks in with a server, forwarding calls to the VoIP client instead of through the cell tower.

In short, it is more of a limit to the controls of the calls then who makes money. If it was about making money then they wouldn't do the VoIP and hot spot stuff were people can make unlimited calls on a hot spot. Seeing how more and more Cell Phones are enabling this and making it possible, it seems like they can control the issues regular cordless phone tech left open.

Re:Urban Networks... (4, Interesting)

jimthehorsegod (1210220) | more than 6 years ago | (#23390630)

BT tried something not a million miles from this in the UK. Went by the name of BT Fusion and the principle was that the compatible handsets used Bluetooth to communicate with a base station (which was also a DSL Router) and thus your mobile/cell phone used that to route calls when in range. AFAIK the base station used normal PSTN lines to route the calls out, but that's just a technicality - it could have been doing whatever at that point, it would be transparent to the end user

Re:Urban Networks... (0)

Anonymous Coward | more than 6 years ago | (#23391652)

DECT doesn't work. It is pretty closed to development and doesn't play by any of the known industry standards.
We were on a project trying to use DECT for VoIP over a WiFi network, and it was a nightmare. DECT couldn't integrate with the infrastructure, its range was short, call quality was bad, it was not able to carry the right signaling for SIP or H323, so, it was a nightmare and took the company to bankruptcy. Google for Globetel Wireless if you want to know more...

Re:Urban Networks... (1)

Urza9814 (883915) | more than 6 years ago | (#23393704)

T-Mobile I believe has that already in place. When you're near a wifi hotspot, it'll give you VoIP service. When you're not, they use the cell towers. It does appear that you also have to have t-mobile broadband though. Service is part of T-Mobile HotSpot I think.

Re:Urban Networks... (1)

Nethead (1563) | more than 6 years ago | (#23394056)

It sounds like what I have at home right now through T-Mobile. see: http://talkforever.t-mobile.com/ [t-mobile.com] My Linksys router has slots for SIM cards too.

Re:Urban Networks... (1)

petermgreen (876956) | more than 6 years ago | (#23398852)

Unfortunately in many countries the cellphone networks have set up thier price plans such that (unless you ave a very light user who is better off on a pay as you go plan) you pay them for a new cellphone every year or so whether you actually take said phone or not,

While pay as you go users don't get "free" phones from the network there is often still some subsidy of the phone price and of course a lot of pay as you go users are using phones handed down by contract users who have since received a new "free" phone.

The result is of course that phones which act in ways that are against the networks interests do not become common.

Re:Urban Networks... (1)

Constantine XVI (880691) | more than 6 years ago | (#23390554)

Actually, iDEN (Nextel) allows one to use the PTT service without a tower.

radio option (1)

zogger (617870) | more than 6 years ago | (#23391746)

The electric company down here had a wireless option a while ago (don't know if it still exists), where you got cellphone coverage plus normal licensed band 2-way radio in the same unit, meaning you could talk either with normal cellphone *or* push to talk direct to other subscribers and across their multi state network of repeaters.

OK- checked, still exists http://www.southernlinc.com/index.asp [southernlinc.com]

Re:Urban Networks... (1)

jgoemat (565882) | more than 6 years ago | (#23392038)

Cell phones should be able to communicate point to point over 100 metres or so. For some reason no phone manufacturer has thought to introduce this feature.

GSM at least is encrypted. The SIM that goes in your phone is registered with the HLR for that company and it includes the key used for encryption. You wouldn't want people to be able to easily eavesdrop on your conversations, would you?

Re:Urban Networks... (0)

Anonymous Coward | more than 6 years ago | (#23392754)

For some reason no phone manufacturer has thought to introduce this feature.
Maybe because no cell company would sell it in their stores.

And they would probably tell their "affiliated" dealers that it would be a "bad idea" to stock it in their stores.

Re:Urban Networks... (1)

Dan541 (1032000) | more than 6 years ago | (#23396722)

Why would they want people to be able to make free calls?

Why would they want to screw their customers?

Re:Urban Networks... (0)

Anonymous Coward | more than 6 years ago | (#23398954)

Hmm, I seem to remember a story a couple YEARS ago about the wifi network that ran on wind and solar energy and was built by the Tibetan Community in Dharamsala India. Antennas were incorporated into the temple spires. They hold a Wifi mesh net conference there yearly, I believe.

Also, wifi mesh was deployed over some disaster areas via balloon by some guys out of MIT.

Why not cellular? (3, Insightful)

ostiguy (63618) | more than 6 years ago | (#23390094)

Read this yesterday, still don't get it. Can omni directional wifi ever compete with a cell tower's coverage range? Cellular has the advantage of insanely cheap commoditized phones.

Seems a bit like trying to use bluetooth to connect two buildings in a campus together - nominally cheap hardware, but probably cannot be coerced into doing what you seek.

Re:Why not cellular? (3, Insightful)

Anonymous Coward | more than 6 years ago | (#23390132)

Insanely cheap commoditized phones subsidized by an insanely marked up cell phone plan. The point of this exercise is to provide the infrastructure where private business currently doesn't feel there would be return on investment. Think OLPC for VoIP.

Re:Why not cellular? (1)

Idbar (1034346) | more than 6 years ago | (#23392748)

Perhaps I missed the point too, but, isn't keeping the power low what maintains this frequencies free? If someone attempts to exceed the power in those frequencies, the first thing a government will do, is regulate those frequencies to avoid people abusing from transmitting power.

IMHO, that's what will happen if someone decides to transmit at high power in unregulated frequency bands.

Re:Why not cellular? (2, Insightful)

MichaelSmith (789609) | more than 6 years ago | (#23390140)

Read this yesterday, still don't get it. Can omni directional wifi ever compete with a cell tower's coverage range? Cellular has the advantage of insanely cheap commoditized phones.
But cellular base stations have to transmit at high power. Doing that attracts attention from authorities. Wireless mesh networks can be low power everywhere.

Re:Why not cellular? (1)

Yvanhoe (564877) | more than 6 years ago | (#23390142)

Wifi has the advantage of insanely cheap communication.

Re:Why not cellular? (1)

MrCrassic (994046) | more than 6 years ago | (#23390144)

That's not the point of this research project.

The point is that many developing countries do not have the economical manpower to deploy cellular antennas everywhere, thus eliminating the possibility of many areas receiving cell phone service. This person is attempting to solve that problem by using consumer-grade hardware and open-source software.

Though it will surely not deliver the kind of quality one would receive from using VoIP or even cellular, it would probably be a highly desirable alternative to the natives in the areas where this will be implemented. I'm glad that people are taking the initiative to rectify this issue.

Re:Why not cellular? (1)

peragrin (659227) | more than 6 years ago | (#23390148)

one problem with cell phones is that if the company who builds them doesn't think there are enough people in the area then that area doesn't get a tower.

there are still huge sections of the USA who can't get cable TV as they are to spread out for a cable company to find value in it.

Re:Why not cellular? (1)

sumdumass (711423) | more than 6 years ago | (#23403260)

I'm in one of those areas. I'm lucky enough to be able to get 3 meg DSL through verizon though.

When I moved to this location, I was aware of a time warner cable running along the road that my road ends on. I'm about 300 yards from the intersection and closer to 200 yards from my nearest neighbor on the same road who has Time warner Cable and Internet. When I attempted to get it, I was told that they needed to do an engineering survey first to determine availability. They then told me it wasn't economically feasible to run service the 200 or so yards to my house and that I wouldn't be able to get their service.

On a plus note, I wrote the public utilities commission (PUCO) asking them why Time Warner is still allowed a monopoly in my area when the trade off for benefits of a monopoly should be service to less economically viable sections and that isn't happening. About a 6-9 months after that, some company started a property survey down my road along the Telephone right of way. 3 months ago, Time Warner announced that they would soon be offering service to every house down my road. I don't know it is was something they were planning all along or it my complain got some people motivated enough to scare service out of Time Warner. Either way, I don't think it would hurt to call your cable company asking for service then asking for an official denial in writing and passing that information on to your state public utilities commissions office. It might just carry enough weight to get service where there isn't any available and make that area with no service a lot smaller.

Re:Why not cellular? (5, Interesting)

Timberwolf0122 (872207) | more than 6 years ago | (#23390154)

I think the main drive according to the article is the 802.11x frequencies tend to be de-regulated and free to use, cell networks have ongoing fees to use that portion of the spectrum. Also wireless routers have very low power requirements and can be run via hippy fuel (aka solar) instead of some poor bugger having to run the mother of all extension cords up a mountain.

Re:Why not cellular? (1)

GeorgeMonroy (784609) | more than 6 years ago | (#23390164)

True but how many people can set up cell phone towers for private use?

Re:Why not cellular? (4, Informative)

William Robinson (875390) | more than 6 years ago | (#23390172)

FTFA,

Technology alone is not sufficient. For any project like this to work for more than a couple of years, it must have a sustainable business model. (In the long run, at least as much money needs to come in as is going out.) Village Phone, which builds on traditional cell phone technology, has been very successful in bringing communications to rural Africa. Their model, in summary, involves an entrepreneur from the village purchasing a cell phone, roof antenna, and charger with the help of a microloan. They are then able to sell minutes to villagers for a profit. The cell phone antenna must be within about 35 km of a cell phone tower and have line of sight, thus making the technological aspect of this model unworkable in many rural or mountainous regions.The business model, however, could potentially be used just as successfully with other technologies, including WiFi paired with VoIP.

Re:Why not cellular? (1)

ostiguy (63618) | more than 6 years ago | (#23390300)

35km line of sight for the cellular bridge station isn't bad - any wifi based technology is going to need line of sight for those same distances. Cellular means cheap GSM phones that work everywhere, as opposed to wifi phones that have limited coverage in the village, and perhaps none elsewhere (the route to the nearest urban center, and perhaps within the city itself, as it is likely already blanketed with GSM)

Re:Why not cellular? (1)

Midnight Thunder (17205) | more than 6 years ago | (#23390700)

35km line of sight for the cellular bridge station isn't bad - any wifi based technology is going to need line of sight for those same distances

In a mountainous region you are sometimes lucky to get 10km line of sight. If you can't get enough users to cover the cost of installation, then the tower won't be put in place.

Re:Why not cellular? (0)

Anonymous Coward | more than 6 years ago | (#23399150)

Yeah the line of sight thing is very important. I've been camping out in the desert. In Ocotillo Wells, our cell phone reception was either poor and non-existent, especially when we went into the fish creek gorge. (obviously)

However, when we went eastwards towards the Salton Sea, I watched my cellphone because on one slight hill I saw the very top of a cellphone tower, and my signal was full for a second, when we got out of a slight dip and over another slight hill, suddenly, the cell phone tower was in full view, on the horizon, and my reception was full bars.

The great thing about wifi, despite its small coverage area, is how cheap it is, and how it can cover an immediate area.

Though in the case of Ocotillo Wells, that wouldn't matter much because their phone lines can only handle 14.4k and the only internet they can get is satellite. Enjoy your laggy calls with satellite.

Re:Why not cellular? (0)

Anonymous Coward | more than 6 years ago | (#23412132)

The 35km limit is just a limitation of GSM. It's a timing problem -- GSM uses timeslots, and a "timing advance" value to adjust for time-of-light delay... but the timing advance value maxes out at 35km, your call would leak into the next timeslot so any attempted call is dropped. (Technically, GSM has an option that uses double-sized timeslots, halving capacity but doubling range, but from what I've read most vendor's cell site equipment does not support this option.)

          The old US-spec TDMA also used timeslots but allowed for at least 100km (since some analog cell sites went 50 miles, or ~90km using the old bag-phones, and further using amps, directional antennas, etc.) CDMA allows for at least 100km cells, and apparently UMTS does too. So any areas with CDMA (900mhz is basically all GSM, but some areas have CDMA in the portion of the US-style 800mhz cellular band that doesn't overlap with 900mhz cellular, and some also have CDMA at 450mhz, which used to be internationally used for NMT analog.)

Re:Why not cellular? (1, Insightful)

Anonymous Coward | more than 6 years ago | (#23390250)

The cell providers own the slices of the spectrum that the cell phones use. And while they can't be bothered to install towers to give coverage to rural areas no doubt they would be quick to take away your birthday if you tried to use "their" spectrum.

Wifi you'd be using directional antennas from point to point. Even cell phones have lousy range with a stubby antenna and low power. The point is to use off the shelf wireless tec as a replacement for running land lines, not to build a wireless mobile phone system.

Re:Why not cellular? (2, Informative)

Steauengeglase (512315) | more than 6 years ago | (#23390284)

Why not? Easy, you could give your kids an old PDA or hacked Skype phone or something for use around the neighborhood without having to pay an extra phone bill.

In a somewhat similar vein (4, Informative)

fuzzyfuzzyfungus (1223518) | more than 6 years ago | (#23390126)

David Rowe [rowetel.com] has been quite busy working on cool, low-cost telcomm stuff. His site also has links and comments and so forth from others interested in the subject, including people doing actual, in the field, deployments in fairly poor and hostile(to the tech) environments.

Re:In a somewhat similar vein (1)

chappel (1069900) | more than 6 years ago | (#23390648)

Brian Capouch has set up something similar with low-end netgear routers and asterisk in rural Indiana - http://conferences.oreillynet.com/cs/etel2006/view/e_spkr/2202 [oreillynet.com] He's given several presentations, but I'm not sure what the current status is.

Don't Bother (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#23390206)

Rural voters cling to guns and religion because they are frustrated about their own lives.

You can see it plain as day. You just aren't allowed to say it.

analogue radio phone (0)

Anonymous Coward | more than 6 years ago | (#23390212)

I've had a radio phone in a remote, mountainous region since the early 70's. Uptime is 100%. What goal must be achieved that can't be accomplished with older tech?

Re:analogue radio phone (0)

Anonymous Coward | more than 6 years ago | (#23390602)

Insane profits from lock in.

conspiracy therorists world wide having their days (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#23390224)

watching the rest of US/them continuing to pretend that all is well.

mountains and wireless (1)

FudRucker (866063) | more than 6 years ago | (#23390228)

the two do not mix well, mountains will severely block radio waves from any part of the spectrum...

relays (1)

MichaelSmith (789609) | more than 6 years ago | (#23390234)

...when strategically placed can deal with that.

Re:relays (1)

FudRucker (866063) | more than 6 years ago | (#23390244)

they better put repeaters on the very tops of the mountains that they need to get over...

Re:mountains and wireless (2, Informative)

klapaucjusz (1167407) | more than 6 years ago | (#23390958)

mountains will severely block radio waves from any part of the spectrum...

The way I read the article, he's using carefully positioned directional antennas to get line-of-sight links.

Re:mountains and wireless (1)

goosman (145634) | more than 6 years ago | (#23393890)

Any part of the spectrum? So how do I pick up all those shortwave and longwave stations and talk to my buddies back home on 20M while at base camp?

Re:mountains and wireless (1)

FudRucker (866063) | more than 6 years ago | (#23396228)

you are right, HF & lower is the exception, a 2GHz wifi is a long way from way down there...

Tried something similar... didn't work well (5, Interesting)

cciRRus (889392) | more than 6 years ago | (#23390296)

I experimented with 5 units of WRT54G wireless routers running Freifunk firmware [freifunk.net] and I tried saturating the link with several G.729 VoIP calls. The system doesn't scale well. Over 3 hops, the number of calls greatly reduces as there is just too much random delay. In order for voice communication to be worthwhile, the latency cannot be more than 200ms although there are good forward error correction schemes and huge buffers.

Latency is a real problem especially when you are doing it over several hops. The "lag" isn't consistent. It will hit you at random interval, and that can be extremely irritating. This may be due to the use of CSMA/CA and RTS/CTS (depending on configuration). I haven't found a way to improve it though...

Re:Tried something similar... didn't work well (1)

MichaelSmith (789609) | more than 6 years ago | (#23390340)

Sounds like a job for ATM [wikipedia.org]

Re:Tried something similar... didn't work well (1)

klapaucjusz (1167407) | more than 6 years ago | (#23390892)

Sounds like a job for ATM

How is ATM going to help, when you're suffering from jitter due to ARQ in the presence of interference?

Re:Tried something similar... didn't work well (1)

FudRucker (866063) | more than 6 years ago | (#23390400)

i have one of those WRT54G routers and they are as light as a feather, the wifi radio part of it is probably no more powerful than one of those FRS radios you see for sale for 20 dollars (cheap and low power) i bet the transmitter does not kick out more than 1 watt...

Re:Tried something similar... didn't work well (1)

cjb658 (1235986) | more than 6 years ago | (#23391122)

i have one of those WRT54G routers and they are as light as a feather, the wifi radio part of it is probably no more powerful than one of those FRS radios you see for sale for 20 dollars (cheap and low power) i bet the transmitter does not kick out more than 1 watt...

The default, according to DD-WRT, is 28mW. DD-WRT lets you adjust it up to 230mW.

Re:Tried something similar... didn't work well (1)

MilesAttacca (1016569) | more than 6 years ago | (#23393360)

I used HyperWRT for a time on my WRT54GL. I boosted the power to probably 50mW, to overcome bad router placement. (In an alcove, in a corner of the house, where the cable modem was, behind a computer. It had to go through three or four walls to reach my parents' laptop on their desk, because they were too cheap to spring for a repeater. Ack.)

Things were peachy for a few months, but eventually the router wouldn't actually *route* or even load its control panel page for minutes at a time, several times every hour. It may have been unstable custom firmware, but I failed to account for the extra heat generated by the higher transmit power. Luckily, I restored the original Linksys firmware, at the standard power level, and it's worked fine ever since. Next time, I'll start with a bigger antenna, then add a repeater, then if I *really* have to go all out, use custom firmware and *mod a case fan into the router.*

Re:Tried something similar... didn't work well (1)

cjb658 (1235986) | more than 6 years ago | (#23394762)

I failed to account for the extra heat generated by the higher transmit power.

they were too cheap to spring for a repeater.

I guess water cooling was out of the question...

Re:Tried something similar... didn't work well (0)

Anonymous Coward | more than 6 years ago | (#23392278)

>i bet the transmitter does not kick out more than 1 watt...

1/4 watt maximum by law, actually. But I believe most APs have chipsets that can't handle more than 100 mW.

Re:Tried something similar... didn't work well (3, Informative)

klapaucjusz (1167407) | more than 6 years ago | (#23390860)

Over 3 hops, the number of calls greatly reduces as there is just too much random delay.

Yes, there are a number of issues with building multihop mesh networks over wifi.

If you're using omni-directional antennas, the most serious issue is that the multiple hops interfere with each other. Ideally, you'd have multi-radio nodes [wikipedia.org] that use different frequencies, and a routing protocol that attempts to maximise path diversity, but the multiple radios increase total cost, and building a routing protocol that takes diversity into account is not completely trivial.

This issue doesn't happen with directional antennas, which is what the author of the article appears to be using.

The second issue is that 802.11 performs reemissions, which cause timing jitter when there is interference. The solution is to modify the link layer to send VoIP packets with lower reliability, which is supported in 802.11e [wikipedia.org] . Unfortunately, current hardware doesn't do 802.11e in ad-hoc mode.

Re:Tried something similar... didn't work well (1)

sxpert (139117) | more than 6 years ago | (#23391562)

babel ( http://www.pps.jussieu.fr/~jch/software/babel/ ) will handle this as required

Re:Tried something similar... didn't work well (1)

skiingyac (262641) | more than 6 years ago | (#23392036)

How does babel fix this? It seems like babel is just a routing mechanism, does it modify the MAC as well? This problem arises because of channel reservation messages & collisions, so not modifying the MAC is going to give limited improvement.

Re:Tried something similar... didn't work well (1)

klapaucjusz (1167407) | more than 6 years ago | (#23394388)

(Sorry for the delay, I was busy rotating all of my ssh keys.)

Babel [jussieu.fr] will handle this as required
How does babel fix this? It seems like babel is just a routing mechanism, does it modify the MAC as well? This problem arises because of channel reservation messages & collisions, so not modifying the MAC is going to give limited improvement.

In case you didn't get the joke -- please mod sxpert as +1, Sarcastic.

Babel could potentially alleviate the problem, since its one of the few routing protocols that are flexible enough to take diversity into account, and hence use different radio frequencies for neighbouring hops. But as you rightly note, there's not much more that can be done for single-radio nodes as long as we stick with CSMA.

My personal hope is that multi-radio routers will become cheap enough to be used instead of our current single-radio nodes.

Re:Tried something similar... didn't work well (1)

skiingyac (262641) | more than 6 years ago | (#23398172)

If you rotate your keys, I will still be able to guess them. You should use gentoo, the developers are far too busy refreshing the packages and compiling their own systems to do something useless like memory debugging.

I think OFDM and FFT chips are becoming cheap enough that multi-radio isn't much of an issue. Having multiple channels doesn't fix what cciRRus is complaining about, the delay of multiple hops... now you have lots of slow, non-conflicting channels... so the per-hop delay of a successful transmission is now a fixed, but longer delay and you still have to manage access to the channels if you want the delay to be reasonable.

Re:Tried something similar... didn't work well (1)

cciRRus (889392) | more than 6 years ago | (#23392294)

If you're using omni-directional antennas, the most serious issue is that the multiple hops interfere with each other. deally, you'd have multi-radio nodes that use different frequencies, and a routing protocol that attempts to maximise path diversity, but the multiple radios increase total cost, and building a routing protocol that takes diversity into account is not completely trivial.

Exactly. Unfortunately the simple WRT54G setup is unable work with multiple directional antennas.

Interestingly, I was advised to disable one of the two omni-directional antennas (and disable diversity) to improve the overall connectivity of the mesh. I didn't try it with two antennas to investigate any the diffences though. Would this really help?

Re:Tried something similar... didn't work well (1)

klapaucjusz (1167407) | more than 6 years ago | (#23392554)

Interestingly, I was advised to disable one of the two omni-directional antennas (and disable diversity) to improve the overall connectivity of the mesh. I didn't try it with two antennas to investigate any the diffences though. Would this really help?

No, it probably wouldn't. First, it's only spacial diversity, which isn't particularly interesting with omnidirectional antennas. Second, the diversity algorithm is very primitive â" every packet is sent using the antenna that had the best reception of the previous packet. There's no way to control it from the higher layers (i.e. the routing protocol).

Re:Tried something similar... didn't work well (1)

klapaucjusz (1167407) | more than 6 years ago | (#23392518)

Sorry to follow up on myself, but there's third issue as well, specific to the Linksys routers.

The binary wl driver for the Broadcom chip has an annoying tendency to drop for a few seconds while it is performing a scan. If you were seeing massive jitter on fairly unloaded mesh networks, that's probably the cause.

I have no idea whether the new b43 driver has the same issue.

i know someone (4, Funny)

extirpater (132500) | more than 6 years ago | (#23390442)

Anyone with experience or ideas on the subject is invited to offer input and advice.
http://img368.imageshack.us/img368/5753/macgyver2rs.png

Routing protocol? (1)

klapaucjusz (1167407) | more than 6 years ago | (#23390914)

Anyone know what he's using for routing?

Check the site of this wifi coop, full of specs (2, Informative)

Pirulo (621010) | more than 6 years ago | (#23391540)

We at Santa Fe, NM, don't have high speed internet everywhere,
the option was this coop [lcwireless.net] formed by advanced users.

The results on the shared T4, (yes, as in tee-four), are amazing and it's the fastest and most inexpensive, -at $30/month- internet access in town.

You just need to provide your own hardware,

I have but one thing to say in response... (1)

jabber (13196) | more than 6 years ago | (#23396048)

ALOHA!

And now for some filler to get the filter to let me post.

overhead (2, Interesting)

sgt scrub (869860) | more than 6 years ago | (#23396696)

This brings me to a thought I have every time someone wants to know if they have enough bandwidth for voip. How much of h323, voip, etc.. is consumed to keep the whole accounting; pay per call, distance of call, who is calling, etc.. type stuff together? It seems to me a constant open stream where audio could traverse in any direction and any distance would not be that bandwidth intensive. Maybe I just don't understand everything involved.
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