Radio and broadcast

Satellite Broadcast

MIT's Technology Review web site has an article about narrowband (128 Kb/s) satellite broadcasting being used in Africa. This could be used to send updates to schools. http://www.technologyreview.com/read_article.aspx?id=16786&ch=infotech

Broadcast texts over shortwave radio

A major challenge is providing a continuing source of content for the OLPC. Access to the Internet in most of the regions of the world where children will benefit from the OLPC program is severely limited. However, most of these regions can receive shortwave radio signals, even in mountainous areas.

Rationale

The OLPC is (1) a tool for accessing information and (2) a tool for self-driven learning through investigation. A problem with the former role is "from whence cometh the information?". With the limited storage resources, "pre-loading" the information on the machines seems like an untenable approach. The crux of this proposal is that having easy and reliable access to a small library of information will be more useful than having spotty access to the entire Internet, even through mesh networking.

Idea

Continuosly broadcast e-book content over shortwave radio with the same content repeating at different times of the day to work around intermittent reception areas. Have the books broken up into chunks, and all the texts from a library interleaved in time. If possible, transmit different interleaving sequences on a set of different channels. The basic circuitry for a shortwave radio demodulator can be very simple, particularly if the decoding is done in software sitting behind a straightforward RF and analog front-end. When a child wants information on a topic, the implemented system captures fragments of a text relating to the topic off the air, and over time, the whole text is collected.

Example

Purely as an example, let the library of e-books being transmitted consist of

1. Project Guttenberg texts
2. mathworld.wolfram.com
3. Wikipedia.

All the content is broken up into packets of some size, encoded, all the packets interleaved according to some scheme, and the entire interleaved stream repeatedly transmitted. The infrastructure for transmitting the data streams need not even be in the nation or on the continent where the recipients are. Let, for example, the entire stream take two months to transmit. 4GB of encoded data at 1200 baud will take ~40 days. 1200 baud for a packet radio seems feasible, though I can't say how complex the hardware would be. Bear in mind we're only talking about receiving, not a full-blown modem. It could be as simple as a shortwave radio with a patch cord between its earphone jack and the microphone input of the OLPC.

Extensions

You can imagine having N different interleavings, which are transmitted on N different channels. When a child wants information on some topic, the request is sent out to at least N other OLPCs, over the mesh wireless network. All the machines start picking up chunks for the text on one of the N different channels. The chunks are sent to the requester over the mesh network. This is similar to the way in which the hosts on a P2P file sharing network cooperate to transfer files from far away into their local area.

Existing technology that can be adapted

There are various existing technologies that could be adopted or adapted to achieve this.

Digital Signal Processing for Ham Radio

The Ham Radio community has a vast amount of experience with weak-signal transmission (and reception of data) beginning with slowscan TV back in the 60's. Phil Karn, the developer of a popular DOS application to run TCP/IP over shortwave, has done some work that could be used. The Geode chipset does have MMX instructions which can be used to do DSP functions.

Digital Radio Mondiale

There is a new standard that is now beginning to be used for international shortwave broadcasting called Digital Radio Mondiale. This already has a subchannel allocated for transmission of data.

HF radio

The ham radio community has mature technology for sending data over long distances at low speeds over narrow high-frequency (3-30 MHz) channels using PC sound cards as data modems. This technology could be used for e-mail to remote regions.

I think this would be a good idea since some children live a mile or more in there towns and villages. Having data travel over long distances will help them keep in touch with each other through the network. I'm sure thought this will have to be approve by the IEEE as a new networking standard, but I'm sure this can be done.

Another historical note about radio broadcast of programs

Back in the 8-bit era, when floppies were still not cheap enough, some computers had a cassette recorder so you could store your programs in cassette. A local radio used to broadcast Atari programs so you could record them at your radio receiver and then play them on your Atari. It wasn't very reliable, since line noise could spoil the recording, but it was a nice idea back then. .:|you could broadcast boot code, mesh-networking software patches, and links to P2P resources. Just include a standard FM receiver (but why not a programmable transmitter as well!), record and process audio into bits, but don't listen to the noise ... oww! N888-9-AE|:.

Luis González

See Basicode 62.252.0.11 17:02, 17 March 2006 (EST)

12 March 2006

USB addons

Well, first of all, the OLPC has 4 USB ports. There is no reason why someone could not manufacture such a radio system as an accessory for the OLPC, to be used in those countries and those regions where this would be a good idea. This would most definitely be a dumb idea in the capital city of Thailand, for instance. But in mountainous western China it would be a very good idea, indeed.

For an example of how small an simple radio circuitry can be, look at this plan for a 3 penny radio. Note that he refers to using a lemonade battery to power it, i.e. electrodes dangling in a glass of lemonade. To use this as a shortwave receiver you just need to adjust the tuning circuitry to bring in the shortwave bands. Here is a circuit specifically for receiving shortwave bands that uses the same radio IC. A receiver like this could actually feed directly into the OLPC's microphone input, however some extra work could interface it with a USB port. This is an example of a microphone input via USB. If it was built as a USB device, it would be powered from the USB port and receive data in the background while the user reads e-books in monochrome mode.

Vertical retrace data channel

One way to mass download info, at least in areas that have TV reception, is to use the vertical retrace interval to send data.

Miscellaneous

Support for this and mention of telesoftware and of MHP

Yes, good idea.

You might like to consider using telesoftware, that is the unidirectional cyclic broadcasting of software and its selective use, to broadcast software packages for the laptop as well.

The following webspace about the DVB-MHP (Digital Video Broadcasting - Multimedia Home Platform) interactive televison system might be of interest.

http://www.mhp.org

The MHP system broadcasts Java programs to interactive television sets.

The following idea, not implemented as far as I know, might be of interest in relation to digital radio.

http://www.users.globalnet.co.uk/~ngo/tor00000.htm

William Overington

5 March 2006

There is now a page about the possibility of an MHP to laptop interface

There is now a page about the possibility of an MHP to laptop interface.

[[1]]

One way connection to internet helps nothing. This is passive usage like watching tv. Software distribution with USB is easy.

• Yet in areas of the world where a two-way link is impossible, a one-way system where lots of software and data such as electronic textbooks can be received from direct to school broadcasts from a geosynchronous television broadcasting satellite and stored localy, telesoftware could be very advantageous.

Historical note about the ATS-6 experimental satellite

Some interesting experiments in using direct satellite broadcasting for education took place in the 1970s using the ATS-6 experimental satellite.

http://www.nasm.si.edu/research/dsh/artifacts/CS-ATS6.htm

William Overington

6 March 2006

Distance and the Mesh Network

As I understand these laptops will have intergraded wireless with the 802.11 b and g standards. The problem I see is that in some countries, like Africa, the children live sometimes a half mile or so apart from each other. The 802.11 b and g IEEE standard only has a reach of 100 feet or more with out modifications. This means the only time the children will be networked with each other is when they are at school. What needs to be done is the wireless in each laptop needs to reach up to at least a mile so the children’s computers are always connected to the network even in their home. The wireless b and g standard can be mod up to 10 miles of reach but to do that requires either a large antenna or an amplifier that would consume too much power. My suggestion is that you create a new wireless networking standard with low radio frequencies like every one has been suggesting. I would like to see it so the children’s computers are always part of the network when they are at home, because as I see it most of the programs on the laptop except the office programs can’t work with out a network. --68.66.231.5 06:52, 31 May 2006 (EDT)

Speeds and data integrity

If I remember my modem hardware correctly, 1200baud is simple FM over half of a telephone channel. This would be more like a FAX channel where the entire frequency width of the channel is available; all normal fax modulations have a baud rate of 2400, with bps of 4800 to 14400.

The processor in this machine would be more than enough to demodulate this in software and decode some serious forward error correction eg par files

62.252.0.11 17:02, 17 March 2006 (EST)