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Peer-to-Peer Cellular
Phos writes: "A cool article over at the O'Reilly Network outlines a possible solution to cellular network outages in the event of an emergency. A P2P SMS technique where individual handsets act as autonomous SMS relays."
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...but the telco's would never want it to happen... they can't bill you (per second) for something that isn't on their network. :)
BlackNova Traders
This will go well until the RIAA finds out people are trading pirated MP3's on the network, so they'll sue and shut it down.
I like fire ants. They are very spicy!
I'd give it a week before an open cellphone is considered as antisocial as an open smtp relay.
I don't read ACs: If a post isn't worth so much as a nom de plume to its author then I wont bother either.
The author just had to take a shot at Napster:
Gnutella is a completely decentralized, or peer-to-peer, file-sharing system. Unlike Napster, there is no centralized server that acts as a broker in processing search requests, matching users with each other. Gnutella clients automatically seek out other Gnutella clients elsewhere on the Internet.
(I guess gnutella is free from lawsuit then?)
I'm not so sure I like the idea: what if some cell phone junkie figures out a way to display all of the messages coming into his phone (a friend of mine can do similar things) and he gets to read everyone's text messages... not a good thought.
~ now you know
How strong is the signal power of a mobile phone?
A base-station is built to receive signals from mobiles far away and is usually equipped
with large antennas and located at a high point.
But the range for mobilephone2mobilephone
communication shouldn't be so long.
A mobile phone signal is very weak.
In the article they are onle talking about the network aspect but not about the "mobile" aspect.
Has anyone an idea about that?
--- censored
When your phone is idle, you don't use much battery life. My phone, for example, can last about a week with only a small number of calls and most of its time being idle. This is also in areas where the signal strength is at least 60%.
I'm sure many Slashdot readers know that modern cell phones increase their power when signal strength drops below a certain level. I'm sure you also know that when the transmitter is active, you use a lot of energy. So now that my phone is a node, not only is my transmitter probably constantly on (thanks to the people who can't live without talking on a cell phone), my battery will drain within a few days to hours, and to top it all off, making it more of an EMF hazard to me; the transmitter is what tauses dain bamage.
Cool idea, but I'd at least like the option to turn it off.
Never hit your grandmother with a shovel, for it leaves a bad impression on her mind...
This would be also a very useful feature when you have no network connection, the phone would poll at regular times for another phone but only if that one is connected on the network. It seems to be a technological leap forward, though, compared to the situation today.
An easier solution, and also useful, would be the ability to send local messages, without network support. The problem here would be reluctance from the network operators as they would loose revenues.
As we are on the subject, all cell phones should have an "offline" option when you want to read/write messages but are not allowed to or do not want to be connected.
Men are born ignorant, not stupid; they are made stupid by education. Bertrand Russel
In order for peer to peer mode to work, you have to have some idea who to send messages you want to get to a certain phone. Which means your phone needs a routing table, and possibly a very large one. Not to mention that all the possible routes need to be sent to every phone. Also, if you send your message to somebody's cell phone, who then leaves the network (power off, phone drops in water, etc) for a long period of time, the message disappears, this possibility might encourage people to just keep trying for a voice connection for messages they need delivered.
Need a Catering Connection
No way! your battery would die within minutes... Think about how much SMS messaging there is, and imagine your phone relaying just 0.01% of that. That would be about 10 messages a minute... Sending and receiving, with verification packets to boot... Battery life would drop big time on any phone implementing this scheme.
---
Programming is like sex... Make one mistake and support it the rest of your life.
This article examines the task of creating a wireless communication system that can survive a catastrophic failure, and still provide basic communication services to its users.
It's called Amateur or 'ham' radio - every year they have an event called 'field day' which is an exercise in taking your gear out and operating on generators, etc. 2 Meter handy talkies can work thru a repeater or direct simplex (peer-to-peer) if the repeater is down.
I'll never forget listening to a ham during hurricane floyd, w/o power, operating on emergency backup power, 80 meter band, crouched in his garage on the NCarolina cost reporting the fierce winds in the night.
try { do() || do_not(); } catch (JediException err) { yoda(err); }
The guy who wrote this article probably doesn't know much about how wireless devices actually work.
First of all, for a number of technical reasons, the phones cant actually HEAR each other. Yes, the phone receives and transmits on different frequencies, and it cannot receive on the same frequency it transmits. It would of course be possible to build a phone that could receive on the same freq. it transmits on, but that intorduces a lot of problems that are expensive to solve.
So, unless everybody is willing to pay 10% more for their phones, no amount of software will make this work.
And if the hardware did support this, making it work software wise would be quite a nightmare. I suppose it wouldn't necessarily work worse in emergecies, because it wouldnot work well at the best of times either.
Another thing about these phones is that they are about as far removed from the world of open source as you can imagine - much further than Microsoft. The manufacturers wouldn't be allowed to open up the source even if they wanted to.
The problem with this (and a great deal of wireless technology development for those of us outside of the industry) is that a majority of cellular technology is proprietary - damn near everything but the 802.11 protocol itself. If a peer to peer option (hack, really) were to appear, it would have to come from a company that has derived its own unique cellular technology so as to avoid the threat of lawsuits from the dominant manufacturers.
Another issue is one of bandwidth and ranges. Corporations have literally 'bought' ranges in which their devices transmit, or lease these aforementioned ranges to other companies. Yes, people you can buy air - and it's rediculously expensive.
I don't mean to sound down on the idea - I love it. We've unfortunately seen the muscle of larger market providers steer the relatively ignorant halls of justice away from the better alternatives far too often.
-sting3r
I worked in the wireless industry as an engineer when the idea of PCS first emerged. At that time, everybody had their own definition of what a PCS network looked like. One recurring part of that definition was that PCS phones would be able to connect to one another in a point-to-point fashion if the two PCS phones were close enough to one another. Of course, such a scheme would bypass the phone company and would decrease the PCS companies profits, so this idea seemed to just sadly disappear. And since the FCC did not impose a protocol standard on the PCS industry, point-to-point calls would have only worked between phones using compatible technologies.
Send/track messages to 100K people: www.xPressAlert.com
Even if every phone had a perfect routing table, you'd still have very severe scaling problems.
Even if almost all of the messages being routed are to phones in the same city, the density of messages at each relay node will be large (total traffic is proportional to the number of nodes talking, and for an even distribution, traffic per node is proportional to the square root of this). A city has a million phones or more. This means that each phone would be routing messages for hundreds or thousands of other phones on a *normal* day. *If* all of the load-balancing in the routing table works perfectly.
Fast forward to Sept. 11th. You have everyone in North America trying to call or message relatives in New York City. The traffic densities as you approach New York would be *HUGE*. Inside the city, you'd have phones trying to handle thousands of messages or *more* at *once*, instead of whenever phone users decided to send. This would melt down the message network in the city and for a little ways around it.
All of this assumes that each phone knows the best route for all messages. In practice, they don't. I'll let someone with more network expertise than I have describe how nasty things get when your phone can only fit a small routing table and you have a constantly-shifting pattern of connections that has to update itself in a decentralized manner (instead of being tracked by a central server that knows where everyone is). Short version: It's not going to be pretty.
In summary, I think that the authours of the article are overlooking a significant problem, especially given that they're proposing this as a way of overcoming system load problems in situations like the Sept. 11th attacks.
p2p Protocol - you do not want the situation where you broadcast to 5 other handsets around you and those broadcast out to "x" others...the target phone will get spammed. (ie, ACK - Thank you, I've received this message x 50 times) On the other hand, you do not want the situation where you relay on THE ONE closest mobile phone to act as your ONLY single relay point and so on....as if you do, probability statistic calculations show if (lets just say) 1/10 chance of failure per hop, this might not be acceptable in emergency situations.
Anyway, you might say "hey, but we could utilize timeouts, routing protocols (similar to RIP) etc etc etc", ......no matter what in the end, you will need to have
- more battery power
because you are constantly transmitting/receiving and processing on your mobile whether your mobile is in client mode or relay mode.You could also argue, you only use these features in emergencies situations. My idea would be for a telco to setup portable (and powerful) base station(s) (whether it be towers, or flexible cable antennas) around and in the emergency site.
It is called a Mobile Ad-hoc Network (manet) and the IETF has a working group which has come up with some protocols and such.
. ht ml
http://www.ietf.org/html.charters/manet-charter
While its a great concept, I don't believe its feasable. In order to properly, and accurately route messages, every cell phone on the SMS network would have to know where every other phone is on the topology. On the gnutellaNET, not all hosts are communicating... with gnutella, depending on your client, you're probably only communicating within your "cloud", which is more a local subset of the topology rather than the ENTIRE network. (likely only 7-10 node hops) Unfortunately, in an SMS implimentation, messages are likely to get lost or bounce around for days until they by chance find the recipient? I don't think that'll work. Cell phones don't have the storage or bandwidth requirements needed to manage a large amount of dynamic routing information.
Skiers and Riders -- http://www.snowjournal.com
The first based on the way cellular systems work. The major cost of the system is centred in those parts of the network that are shared between the users, namely the base stations. This makes the handsets (which each user must have) cheaper and thus lowers the system cost by sharing the cost of the expensive parts between users. Great, but why is that relevant? It is relevant because the maximum range between a cell and a base station is primarily determined by the low noise (read: expensive) receiver and high power (read: expensive) transmitter at the base station. So the range of cell-to-cell communication will be MUCH less than the base station-to-cell range. So much so that it is possible that the distance between a cell that can see a base station and a cell that can't will be no more than a few metres. This means that a large number of hops will be required in most cases clogging up the system bandwidth and meaning that each cell will need to be able to store a large number of messages. These problems will be even worse in an emergency when everyone and their dog are sending messages. Also, cell-to-cell communication will require much more power from the cell than base station-to-cell communication because the reciever in a cell is not nearly as good as that in a base station.
The second problem has to do with battery life. The battery life of cell phones is rather short when the transmitter is used. As explained previously, the power needed for cell-to-cell communication is rather high, aggravating the problem. This could cause major problems when people's batteries start going flat because the person in the next office likes sending lots of messages and is out of range of a base station (quite possible in buildings).
I think this is a great suggestion, but it assumes that the cellular environment is the same as the internet, which it is not.
I don't know... seems to me that you'd wind up spending an awful lot on SMS charges just to render a picture of Natalie Portman...
/Brian
First you'd form a piconet. If any of the systems is physically connected to (internet | base station | something else), relay there, else form/connect next device on a (same | different) piconet (the next device might have different piconets available). When the working relay is found, send back a message, targetting the original device. Relay it randomly and add a node to the route table the message contains. The original sender can deduce a short path (it's not necessarily the shortest!) just by looking at the message that arrives first/has the shortest route.
At this point, it should be possible to send small text messages with some efficiency.
It's also possible for other devices that happen to recieve a route recovery message to use the some of the readymade routes (so that everyone doesn't need to do this slow procedure).
The total amount of transferrable payload *per device* should probably be limited to something like 2kB, if this is to be used as an emergency network, to insure everyone can transmit their messages.
Any ideas/corrections from those "in the know", especially bluetooth people here?
Disclaimer: I'm not a bluetooth specialist... In fact I don't know much at all about it! :)
Interested readers should probably read A Performance Comparison of Multi-Hop Wireless Ad Hoc Network Routing Protocols to find out why this is difficult.
According to the article, phones would have to exchange and update their routing information all the time, even while everything was working normally (because by definition a phone can not know if a neighboring base station that's just out of reach is still working or not). Every phone would continuously keep broadcasting a list of every other phone and base station in it's reach.
This overhead alone (just to update the routing tables) would consume a big chunk of the bandwith all the time. Since a base station dropout or overload is an exception (hopefully), a dynamic on-demand routing protocol would make much more sense in this case.
Idempotent operation: Like MS software, wether you run it once or often, that doesn't make it any better.
The TX stage is totally designed to talk to the base station, and nobody else. That means it can only push low power (base station has big expensive high gain receive systems to extract signal from noise) and only at the TX frequency band.
Similary, the RX stage is designed to hear from the base station, and nobody else. That means it expects rather high power signals (base station is not running on batteries and can generate huge power if needed) and only at the RX frequency band.
This is the most fundamental part of RF network design -- do the small remote stations (handsets in this case) need to talk directly to each other, or just to a hub station (base in this case) that is equipped with a collosally more expensive array of equipment? THAT decision (and bitrates) drives ALL the remaining design decisions in the RF sections of both the remote and hub.
These kinds of things are fixed in hardware (e.g. capacitors and inductors, filters) and can't just be changed by downloading new firmware.
One simple rule for its versus it's
Self-structuring ad-hoc data networks are pretty cool. Pagers, Cellphones, PDAs and the like (all these embedded devices) would serve themsevlves well to build an adhoc network like this...
a cool little device that i bought my niece for Xmas '00 was a Cybiko see Cybiko.com
The specs are here
With two units, one in the hand and one married to your PC the device will enable a limited sort of 'home wireless access' on WAP.
Who needs service fees and a monolithic oppressive corporate watcher, why not build a low power, low bandwidth network of peers in the 'cybiko fashion'.
..or wait till 802.11b(or 'a') chipsets become SUPER small and SUPER cheap...
I have been wondering if something like the Cybiko could be made to work for real use. If you haven't seen them, they are handheld computers for kids that communicate in an ad-hoc peer-to-peer wireless relay network. And they're like $80. A cable to your computer turns one into an internet bridge, so that your unit can pass signals from nearby units over the net to span larger ranges. Their biggest drawback (aside from being cheesy and designed for kids) is that the range is only a few hundred feet, so the device density has to be high to span any distance. (like in a high school or a mall, where their target audience spends all their time)
If, say, a palm-pilotish device could be coupled with a cell-phone level transceiver (or possibly an FRS radio component for 2-5 mile range) we could have ad-hoc wireless wherever we go without paying network fees. In dense areas, the power could be lowered to prevent interference with all the other devices in the area, and internet bridges could help span large rural areas.
Is there anything preventing a company with no networking interests (they'd want monthly fees, then) from doing this?
If you're a ham radio op. If you have a loose network of hams with dual band handhelds, you can cross-band and relay a message a long distance using other people's handhelds. Of course, this all requires the cooperation of the user. Let's look, perhaps, at how this could have helped in the NYC tragedy:
Op with a 5 watt handheld has set up a small communication base near ground zero. The op can sync up with another op a few miles away and relay help and welfare information. Ground zero does not have power. The second op does not have power. The second op is able to relay the message to a ham with power who can relay the info on 20 meter to the other side of the country. With minimal amounts of planning and just a few hams, a system is devised that permits message relaying all over the country, even though the phone system is jammed and power is down for miles. Anyone with a decent scanner can pick up the signal on 20 meters and hear a nice formatted report of people who are OK.
There is no reasonable defense against an idiot with an agenda
:wq
And fix the link
http://www.ietf.org/html.charters/manet-charter.ht ml
-Ben
You beat me to it-- you must have posted this while I was writing mine. (see the post below this one!) A super-cybiko with a better transceiver and a form factor an adult could carry in a pocket would be the coolest thing ever.
Another optimization-- you could design the network to prefer the shortest route to an internet gateway (any unit in its cradle hooked to a PC would be such a gateway), to move traffic off the relay network as soon as possible. This would allow much greater scaling and distance even in low-density areas.
If Cybiko can do it for less than $100, surely an industrial-strength one can be made for less than $700 or so-- which would be a deal considering there would never be a network fee!
Cheaper transceiver-only cards could enable existing laptops to access the network as well.
Payment for SMS would become a problem.
I come from Denmark, and yes we have a very useful and standardised network (sorry US). I think this new idea is really cool, but there is one major problem surrounding payment and the revenue streams for the mobile operators.
Today the mobile service providers have revenue on SMS messages. In Norway they overtax the SMS messages to have a really nice profit (up to more than one US$ pr message). In Denmark some government regulations have put a limit to the revenue/taxation on SMS messages.
What do this mean for the idea? If an SMS was being redirected from phone to phone, who would pay? If the last user (before the base station) should pay for all the massages he relays, I think he would choose other types of mobile phones. If the protocol contained the phone that sends the SMS, we would open up the network for hackers etc... Potentionally this type of network could render SMS completely out of their control, as an SMS message theoretically could move from phone to phone without touching a base station, pretty much like a message is being routed through the internet... (not completely like the internet, I know.)
And I don't think the mobile operators would give up their income stream.
-:) Oh no - not again.
www.rednebula.com
What the article describes is the old military concept of "mobile mesh network". Highly survivable solutions are a must in a combat environment, but their their characteristics make them completely unmarketable. In our specific example, the reasons are as follow :
Full-mesh wireless networks like JTIDS are inherently inefficient because one cannot make
range (timing) and Doppler corrections at the transmitters, and because there is no frequency
reuse. With a repeater-based architecture, all transmitters can adjust timing and frequency to
correct for their range from the repeater and for relative velocity. In a full-mesh network, all of
the other nodes are potential receivers, but one can make range and Doppler corrections for only
one of them. With multiple repeaters (base stations), two repeaters that are not close to one
another can use the same frequencies without interference; such frequency reuse enables large
increases in system capacity over full-mesh and single-repeater architectures. Decreasing cell size in order to increase frequency reuse reduces the survivability of the network.
A closely related concept is that of the self-organizing hierarchical network. These networks are similar to the homogeneous mobile mesh networks, except that nodes organize themselves into clusters and by some means "elect" a cluster head (see, for example, Alwan et. al, 1996). The cluster head is responsible for keeping track of the membership of the cluster and the locations of nearby cluster heads, and for performing routing, switching, and trunking functions. However, since any node must be able to function as the cluster head, cost and battery life are likely to be problematic. Remember that mobile devices are highly contrained.
The problem with military stuff is that it is grossly overengineered from a civilian point of view. We all would like to carry cutting edge radio hardware with us and be ready for all kinds of emergencies, but there is a price to pay and the civilian market won't bear it, preferring to take long term risks and to get more features and more performance in the short term. If survivability was foremost, everyone would be backing up their data. Field experience shows that it is not he case.
Sources :
http://www.google.com/search?q=cache:3fDYY36opQQ:w ww.rand.org/publications/MR/MR960/MR960.chap3.pdf+ tactical+network+relay+node++survivability
http://dss.ll.mit.edu/dss.web/98F-SIW-143.html
Finally, my idea is going to be put to use! I should have gotten the patent on this before they stole it though!
Of course my idea was for wireless P2P internet, not SMS, but the same basic principles apply.
Your battery life transmitting SMS messages should be no worse than simply being out of contace with a tower.
If you have lost connection to the main network, then battery life is going to be short anyway. Currently, your phone operates at the lowest power possible to be able to communicate with a cell tower. (And if you think your phone only transmits when you are using it, try putting it on top of a computer monitor, they transmit quite frequently). When there is no tower available, your phone will increase power until it successfully contacts a tower or hits the max power.
The longer you are out of the area, the shorter the time your phone's battery lasts.
For good peer to peer mobile phone systems it's best to use systems based on Time Division Duplexing rather than Frequency Division Duplexing. TDD is used in Japan's Personal HandyPhone System (PHS) and the early models had peer to peer voice. FDD is used mostly on all other digital networks (GSM/CDMA/TDMA etc.), this means that the base station talks to mobiles on one band and all mobiles talk back to the base on another. They're not designed in hardware to support transmissions in bands they don't normally use. Further, the base sends out all kinds of extra data to mobiles: timing control, paging info, frequency channel allocation, etc. It'd take WAY more than a software upgrade to support that.
Also, mobile phones get away with small antennas and relatively low power transmissions because the place they're talking to is usually a HUGE antenna sitting on top of a hill somewhere, high up or on top of a building. That system gives you reasonable cell size. If you had to have mobile to mobile it'd shrink the distance that you could send to quite considerably.
Finally, sad to say it but in North America you basically have 3 different and incompatible digital systems, in addition to the analog one. That'd cut down the possible intermediate hop hosts.
I'm not saying this is a bad idea but given the current cellular technology it is infeasible. Didn't the cell sites for the most part stay up in NY though? Heard on the radio this morning how there's been a huge increase in cell phone sales since then.
http://www.nomadphones.org/
At what price learning? At what cost wisdom? The price is a man's peace of mind, and the cost is his life.