Public Information Servers and

Public Information Terminal Software

Improving Life Through High Tech
Copyright 2006 by Stephen Vermeulen


A thought that occurred to me on 7-Aug-06, no doubt I'll later find there is some sort of RFP with this in it. But for the record I thought I would share it all the same.

The basic concept is to define a new class of server device, and have it share its information according to the following criteria:
  1. the information is public (no access restrictions)
  2. the data is published in a user-ready way (typically as HTML pages) to an audience in physical proximity of the server (think of browsing the web by travelling to each server)
  3. a stateless broadcast protocol transfers it (so the server does not need to spend resources for each client)
  4. a wireless network protocol is used to distribute it over a relatively short range (WiFi would be fine)
By doing this the servers can be made very low-cost, low-power and low-maintenance devices. Typically little more than a WiFi router box that has been flashed with new software. Since there is no security any WiFi equipped PDA, laptop, personal media device, car GPS navigation box... can be used as the client, and once in physical range could pickup the pages the server is broadcasting, cache them and let the user browse them.  Again, since the browsing is done entirely on the client device, there is no extra load imposed on the server by each client - this allows a very small server to provide information to a very large number of clients.

Potential applications:

  1. place at public transit stations (train platforms and bus stops) to provide the passengers with more detailled information about current service conditions (than are usually available through electronic sign boards - and at lower cost). As well, the device can serve some static content, such as route maps etc.
  2. place in public transit busses and trains to provide information on the next few stops and the current connection schedules (and route information) for these stops
  3. use at airports to distribute airplane arrival and departure times and gates, meeting places and announcements, information about transit connections, busses, rental cars, parking etc. 
  4. stores, restaurants, theatres and other businesses could set these up to broadcast current and future sales announcements and static store information such as store hours.
  5. museums could use these to provide information about the exhibits or even a self guided tour

Enabling Technology

The existance of these devices depend on the following key enabling technologies, that are already well established, but are not currently used together in this fashion:
  1. stateless, broadcast networking protocol, such as broadcast UDP, that allows one server to send a message that can reach an unlimited number of clients. In an application like this the unreliable aspect of UDP is not particularly important, all that would be needed is for the data to be checksummed so that the clients can throw away bad or incomplete packets and just wait for the inevitable re-broadcast. A way of marking several packets as containing a single larger message would also be needed.
  2. low cost widely-available wireless networking is already available with WiFi (Bluetooth probably cannot be used for this due to its pairing etc). The WiFi LAN would need to operate in a broadcast only mode (no sense in opening up a security hole by allowing clients to send data to the server) and clients would just need to sniff for these packets - devices like war driving scanners make it appear that WiFi could probably be used without modification already.
  3. HTML format for the pages of data, each page would need a name so that hyperlinks between pages on the same server (within the users cache) would work and allow him to navigate a tree of pages
  4. a client device that caches a number of pages of data for later review by the user - this idea has been around since the late 1970s when it was used by TELETEXT systems to broadcast information to set-top boxes for display to TV viewers
  5. client devices that have a small display and the necessary WiFi capability, there are many PDAs that meet this specification already, as well as laptops and probably other devices (like cell phones, personal media players and vehicle GPS navigation systems) will get this technology in the future.

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