Hacker Newsnew | comments | show | ask | jobs | submit login
Mesh network before/after Hurricane Sandy in Red Hook, Brooklyn [pdf] (tidepools.co)
41 points by jrbaldwin 751 days ago | 12 comments



I've recently wondered, what's the maximum bandwidth that can be pushed through a mesh network? Where would current wireless technology max out if significant portions of currently-allocated spectrum were reassigned for general consumer and business use, and used to build mesh networks?

For example, would it be feasible to reallocate FM and AM spectrum for general-use wireless mesh networks, and then replace the lost commercial radio service by installing, let's say, mesh routers in automobiles and having them programmed to easily pull audio streams from radio broadcasters via a pervasive wireless mesh network?

In other words, how close could we get to replacing the current broadcast TV/radio infrastructure (in terms of broadcasting and consuming video and audio) with mesh-routed wireless IP communications, if all of that spectrum were made available to be used by the mesh network?

Would pervasive mesh networking be more feasible if more spectrum were made available, and if so, could the displaced services be replaced via IP over the mesh network itself?

-----


There is no general answer.

It depends on the granularity of the mesh, i.e. the range of each node.

The smaller the range the greater the bandwidth (and the more complicated the mesh).

A wire essentially has a range of one centimeter * length. If you had a mesh with nodes with a range of one centimeter (and multiple of them line up to create the length) you can duplicate the bandwidth of a wire.

In a perfect world you would saturate the air or ground with tiny transmitting stations (powered by magic presumably). They would automatically make a mesh and create an almost unlimited bandwidth for everyone.

In a less perfect world you glue them (you don't want people breathing them) to buildings, trees, rocks, etc. Then saturate the ground and air with a powerful electrostatic field that the nodes could use for power. (A la http://en.wikipedia.org/wiki/Wardenclyffe_Tower .) Probably with a bunch of synchronized towers for efficiency.

Make the bandwidth and electrical power a public good paid for by taxes. (Each country could probably opt in individually.)

PS. I know people will suggest solar power, but that would require solar collectors that are just too large, plus batteries that wear out (or capacitors that are too large). It would also complicate installation - you can no longer apply the nodes randomly everywhere.

-----


Maximum bandwidth all depends on the technology used. If we're talking 802.11n using MIMO (Multiple Tx and Rx antennas/spatial streams) then we could theoretically expect 600mbps. However, even if we're using top quality kit, today's speeds are more like 150mbps to 300mbps.

See... http://www.ruckuswireless.com/products/zoneflex-outdoor and https://en.wikipedia.org/wiki/IEEE_802.11n-2009

However, the problem with a mesh, particularly WiFi, comes from the size of the broadcast domain, or the service area footprint and, more specifically, the frequency channels.

If you operate a mesh where single access points mesh with their direct neighbours, then that 300mbps is shared over all the AP's and the bandwidth reduces dramatically, especially if it's a dense deployment where noise from one transmitter can be easily picked up by multiple receivers.

One way around this is to copy what cell carriers do and... create some cells. A cell is a part of a larger network but it operates on a different channel to it's neighbours, so that 300mb is just for that AP, it's subscribers, and a select, but small, number of neighbour AP's.

The problem with this is you then need two radios (two AP's), connected via Ethernet cable, to operate on two channels. I.e. One radio looks left on channel 1, the other radio looks right on channel 11. This way you get frequency re-use and can get much closer to that full channel capacity, but at the cost of doubling the infrastructure cost.

-----


To answer your other point about replacing AM/FM broadcast with IP delivery.

This is not an efficient way of delivering the information. A broadcast is a single transmission that can be received by anyone without impacting the ability of others to then receive it. For large numbers of viewers/listeners it's a very efficient method of delivering information, and very cost effective, only having to pay for one big transmitter and a license for one channel.

If we look at it in terms of data-rates, a typical DAB radio channel may be 128kbps and might reach a million people.

Using a WiFi mesh network would mean that 128kbps audio stream would need to be transmitted to each user individually, so that's increased the data transmitted by a factor of 1 million (or however many listeners there are). Of course this is spread over the whole listener base, the real impact would be much more localised. Perhaps 10 people are listening to the same stream on 'your' mesh. That's still 10 identical streams going to 10 people where before you only had 1.

Of course there is IP Multicasting which reduces this problem, not sure how it would work in a Wireless Mesh environment though.

-----


Well to answer your question of pervasive mesh networking, recently in USA NTIA got 700Mhz spectrum to as public safety networks. They are trying to deploy ubiquitous public safety network over LTE, and one of the back end technology will be mesh networks. We should be seeing such networks in 1-2 years from now.

-----


There seems to be so many meshnet projects. Is there any comprehensive list of them? Both actual deployments and related software/hardware projects.

-----


https://wiki.projectmeshnet.org/Category:Mesh_Local

It's a small list, and it doesn't say anything about their activity. The project posted here is unrelated to Project Meshnet (which is an outgrowth of r/darknet et al).

-----


The Red Hook mesh is not related to meshnet (meshnet is a reddit.com/r/darknetplan intitiave from the beginning).

This one was developed directly with the community from the beginning, and it is still growing today. The city now funds Digital Stewards (local residents who learn about mesh networking) to expand and maintain their own network.

-----


Edited to clarify. Yesterday's Chicago mesh thread prompted a search that didn't turn up much besides darknet/meshnet which is why I posted it. I'm glad to see this update though– when I saw the title I was a little bit worried that it was going to be a project postmortem. (I was only tenuously aware of the project beforehand, but seeing the OTI affiliation made it much more clear.)

-----


oh, meshnet is a name of a specific project. well, that tells how well informed I'm about them, I thought it as a generic abbreviation of mesh network.

-----


Seems some dummy text was left in, or content encoding issues on multiple pages.

-----


Weird, here's a Scribd link: http://www.scribd.com/doc/147627564/Red-Hook-Initiative-Tide...

-----




Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | DMCA | Apply to YC | Contact

Search: