|
Overview
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:
- the information is public (no access restrictions)
- 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)
- a stateless broadcast protocol transfers it (so the server
does
not need to spend resources for each client)
- 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:
- 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.
- 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
- 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.
- 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.
- 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:
- 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.
- 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.
- 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
- 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
- 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.
|