A Future for AMATEUR and COMMUNITY WLANS?
|Henry OTani G8OTA|
I have been a keen advocate of "broad band" for more years than I care to remember having built antennas and converters for Amateur Television as early as 1964 through to design and build of all the RF sections for GB3UT our first AM 1.3GHz TV Repeater in this part of the country in 1985/6 and the current interest in microwave WLANs.
I was introduced to AX25 Amateur "Packet Radio" fairly early in the mid-1980's and having recently designed one of the UK FM Citizens Band (CB) Transceivers (TC300) when legalised a few years earlier I realised how great it would be to have a "CB Data Network" across the country. Data on 27MHz FM CB was however specifically prohibited by the government.
In 1986 I helped set up a local branch of the national
Community Radio Association one of some 800 groups in the country
which unsuccessfully campaigned to create a national "Community
Broadcasting Service". In the late 1980s I joined the
dial-up computer bulletin board (BBS) movement and in 1993 did a
study for Stockwell Park Community Association funded by
South London Training & Enterprise Council (TEC) regarding
the building of community (ergo communication) on deprived
estates through provision of education and broadcast
entertainment media using municipal cable. With the introduction
of the World Wide Web my interest evolved into development of the
concept of a "Free Local Community Internet Server" but
the launch of Dixons free internet services at local
call charges (the first of many) in the Summer of 1998, made this
no longer necessary.
Interest in IEEE 802.11:
In Autumn - 1998 I realised that the proposed world-wide licence-free global specification for short-range IEEE 802.11 ISM band WLAN products (being on the upper half of our U.K. 13cms 2310 - 2450 MHz U.K. Amateur Band) could become the basis for a super broad band "Amateur Wireless Microwave Network Standard" which could do much to restore Amateur Radio here in the U.K. at least as the dynamic, exciting, modern scientific and technical hobby it once was.
The development of "Amateur Radio Internet Services" now could be particularly attractive to the current lost generation of young mobile phone and computer using children and teenagers for whom the atavistic operating procedures, limited potential achievement and appeal of 20th Century Amateur Radio must in the context of any intelligent youth forum nowadays appear bizarre, trivial and pointless to say the least!
A startling aspect was that with a comprehensive nation wide "amateur network" on 2.4GHz (A deployment of nodes no greater than the low-speed network which six thousand or so UK amateurs built nodes during the first five years of AX25) outsiders i.e. ordinary members of the public could participate providing they were using type approved kit and within hailing distance of another amateur node. Amateurs would on the whole be delighted to have an explosion of many new people joining the hobby and using their systems. At last amateur radio could be vertically-integrated as a popular local community activity.
When implementing WLANs on amateur microwave bands, UK Licensed amateurs are not as restricted in transmitter power (up to 400 watts pep) or antenna gain (unlimited). With the "simplex transceivers" used with IEEE 802.11 it is easy with automatic solid state switching between Tx/Rx modes to make "strip-line power amplifiers" and other performance enhancing "in-line goodies". Even without extra amplification, the WAP/Web Server fitted with an amateur omni-directional high performance repeater antenna could have a practical gain of up to +13.5dBd (ref. dipole) approximately quadrupling service range. The remote user who is licenced could have an outdoor ex-DBS parabolic dish reflector antenna of say 1200 mm. Dia. with a simple dipole and reflector feed, that would give over 25 dBi gain. A total improvement (just with high performance antennas) of 38 dB! - extending the normal operating radius of IEE 802.11 (normally of no more than two or three hundred metres) roughly some 64 times or up to 16 Km! Adequate for most municipal area schemes and simple inter-nodal links of 10 -15 Km.
With simple frequency conversion (which is easy at these low power levels) the discrete 2.4 GHz modalities of IEEE 802.11 can be replicated (translated) on any other sufficiently wide amateur microwave frequency segment.
2 to 10 Mb/sec "Community LANs" could enable clever young enthusiasts, students and the economically disadvantaged to access the internet without expensive telephone charges and at presently undreamed of connection speed. High speeds of this sort open up "Virtual Conferences", "Virtual Reality" the "Internet Broadcasting" possibilities of "Community Radio" "Community TV" and "Free Local Video Phone". These are areas which the existing speech bandwidth of 56Kb/sec via telephone modem internet cannot develop any further.
Since circulating my ideas in a Winter 1998 Newsletter (as a
kind of manifesto) shortly after my election as Secretary of the
local group (see file: Mendip Repeater Group Newsletter at
http://www.norton.demon.co.uk We have had a great deal of
enthusiastic support both locally and nationally. We have
gained support of the national Radio Society of Great Britain and
the U.K. Government have even recently relaxed an existing
prohibition on "Amateur Radio Internet Access".
In a few years there will be commercial broad-band services everywhere.
The key to this project is that we need to demonstrate a "Community LAN" actually working. That is:- "An open community owned and operated, not-for-profit WLAN operated like an Amateur Radio Repeater". It is an indictment of society today that this should appear such a strange or radical concept.
We have the support of Bath University Radio Society to install a WLAN running at the university as soon as we have configured a server and WAP. I have recently found a local computer business to act as "Official Sponsor" for the setting up of this pilot "Amateur 802.11 Community Server" so hope to shortly place an initial order with a firm for "samples" of a couple of WAPs and up to 12 Adapters.
Using a type approved WAP and conformal antenna does not require the initial unattended WAP and Web Server installation to be licenced at all. Anyone within range (probably at least half the campus area at Bath University) will be able to use portable and fixed computers for access also without a licence. Licenced Radio Amateurs in the region however will be able to use WLAN adapters with high gain dishes at line-of-site ranges of up to perhaps over 30 Km (perhaps 20 miles) line-of-sight.
Growth is difficult to predict but will be initially explosive and exponential. My opinion is that a new WAP and Web Server in an urban area (especially when upgraded to Licenced Amateur Repeater Specifications running 25W ERP) will today generate between 100 and 300 users in the first 12 months of operation. The extra gain possible at the users end made possible by ex-DBS satellite dishes (albeit de-rated 12 - 14 dB at 13 cms) makes the service area for a given installation somewhat better than existing FM 23cms ATV repeaters (with 18dBd user arrays at best). For most radio amateurs who have installed kit and are familiar with our existing 1200 baud AX25 digital network and repeater services, the demand (at about the same price as an AX25 node) will be irresistible and the uptake much faster than otherwise expected.
If we can get this practical demonstration of "A Community LAN In Operation" established in an easily repeatable and technically repeatable fashion (as planned) we will then be able to write this up for dissemination at a national level.
This is an entirely new and potentially super-popular (killer) application which while outside the "commercial rat-race" could bring users - in the hundreds of thousands very quickly. I would expect at least 50 to 100 similar groups to be setting up within the first 12 months. This works out for first 12 months as:
WAPs in U.K.
100 - 200
WLAN users 5000 - 30000
Note: that unlike 1200 baud AX25, the take-up will not saturate at the 50,000 or so licenced radio amateurs in the U.K. Members of licencees family in the U.K. are also now allowed to use equipment (under supervision) and the licence free use by anyone else will encourage many computer enthusiasts (like amateur BBS operators who existed in their thousands only a few years back) to operate their own neighbourhood/district "Community WAPs".
This is a classic "critical mass experiment". Nobody will buy a single WLAN adapter unless there is a WAP service to use it with. No free market investor can confidently provide saturation coverage of "Communal WAPs" at say one every 0.5 sq. Km (at a conservative cost of several U$ billion dollars) waiting for uptake of fee-paying customers.
Radio Amateurs as pioneers again! are in a unique position to set up WAPs with sufficient radius of operation (26 Km radius = 2000 sq. Km) such that a few strategic installations can cover very large service areas (similar to existing UHF repeaters). Since every early user can become a "node" there can very soon be WAPs covering even the smaller centres of population such as towns and villages.
The Direct Spread Spectrum (DSS) and cellular channelisation philosophy of IEEE 802.11 means that there can be unlimited bandwidth for unlimited numbers of users providing cells grow smaller as uptake increases.
This requires a 1Gb/sec or so super-network which given
the demand and many suitable amateurs sites our community should
be well equipped to facilitate.
G8OTA - Bath