http://www.arrl.org/news/features/2008/03/01/2/?nc=1
D-STAR at the 2007 Medtronic Twin Cities Marathon
By Erik Westgard, NY9D
[EMAIL PROTECTED]
March 1, 2008
Minnesota hams put the D-STAR system to work.
The Hennepin County Communications Van joins other Amateur Radio vehicles and
trailers in D-STAR integration testing.
Ryan Westgard standing by to scan the bib numbers into the Amateur Radio
tracking database of incoming injured runners at the Medical Tent at the 2007
MTCM.
The 1st generation ICOM RP-1 repeater.
The finish line area at the 2007 Medtronic Twin Cities Marathon.
The 40x80 foot Medical Tent and attached Amateur Radio managed Interagency
Dispatch Center at the MTCM 2007.
Peter Corbett, KD8GBL, monitors the database server and D-STAR and packet
uplink transmitters in the data trailer at the 2007 MTCM event.
The MTCM 2007 Family Medical Information Tent — amateurs in yellow shirts and
community medical volunteers use 802.11b networked laptops to query the Amateur
Radio database of runners who have left the course.
Kelly Black, KB0GBJ, (L) and Max Klingert, KB0RSQ, led the software development
team for the Linux appliance back end to the D-STAR repeaters and our database
uplink system for the 2007 MTCM.
At first glance, the Minneapolis/St Paul Metropolitan Area has a good Amateur
Radio infrastructure for public service events. We have more than 40 FM voice
repeaters, (about half are on good sites) and two 1200 bit/s packet radio
networks, three counting APRS. An increased focus on data applications by
served agencies has strained our data capabilities.
While it is certainly possible to use the operating range of commercial
Internet services, our stated goal of providing backup communications makes
this an imprudent choice. Many of our agencies use the Internet for primary
data communications, and using the Internet to back up the Internet may be fine
under normal conditions but is a poor design for truly catastrophic
emergencies. The recent collapse of the I-35 bridge in Minneapolis was marked
by a well publicized overload of the commercial cellular telephone networks in
the area of the incident, and in some cases, cellular data and voice services
share limited bandwidth to the cell sites.
A Big Marathon with Big Communication Needs
The Medtronic Twin Cities Marathon is one of the larger marathons in the United
States in terms of starting runners, with more than 6100 in 2007. There is also
a 5000 runner 10 mile race on a similar course at the same time, and hundreds
of thousands of spectators and family members also participate in the weekend
of events. The race organization has long relied on Amateur Radio for backup
medical communications, utilizing more than 130 amateur operators spread across
the racecourse and finish line area. We run five voice nets and also provide
net controls for the medical channels on the rented UHF business band radios
used by the medical teams.
On the data side, we track the location only (for HIPAA reasons) of runners who
seek medical attention or leave the course for other reasons. This data is
input based on voice reports to the on-course net controls and from information
input at runner bus stops and at the medical aid stations throughout the
course. For inputting information out on the course, packet and a character
interface have worked reasonably well, but we do not have enough data bandwidth
for much in the way of database queries. Families and medical teams are always
inquiring about the location of runners. This requirement is acute at the
finish line, when runners do not appear in the Family Meeting Area on schedule.
We set up six laptop computers in the Family Medical Information tent, where
queries can be made. We also have computers in the main medical tent for runner
check-in and check-out and in the communications center where finish line EMT
and physician “(Cardiac) Arrest
Teams” are dispatched.
This much data moving around at the finish line is well beyond the capability
of packet radio. We also needed an easy-to-use Web interface to our database so
untrained and non-amateur volunteers could be utilized. For this reason we have
implemented commercial 802.11b access points from our data trailer. Our
database, called Trivnetdb, has a packet AX.25 interface and TCP/IP support for
Web and telnet users.
Enter D-STAR
The recent release of the ICOM D-STAR L-band repeaters and radios (such as the
ID-1) presented a possible solution to our problems across the course. If
several wide area repeaters were installed, we could access our database of
runner status across the entire course using a familiar Web interface. We could
perform as many queries as we wanted, and be able to handle high data volumes
if we had hot or other unfavorable weather.
Doug Reed, N0NAS, bought our first RP-1D repeater under the ICOM “buy five
ID-1s and get a free repeater” program. After a few sessions of testing and
evaluation in monthly work sessions held at a local fire station, we decided to
install the repeater on one of our good sites. The repeater as-is allows
one-to-one sessions between ID-1 radios, encapsulating the 90 kbit/s of data
packets in amateur call signs. This was a problem though, as our database is
located in a trailer at the marathon finish line, and we wanted to have
multiple users access the database at once.
The repeater has an Ethernet interface on it. Multiple remote ID-1 users are
allowed to reach the Ethernet. You assign an IP address to the Ethernet, and if
the users of remote ID-1s are in the same subnet they can reach the Ethernet.
This is used for the ICOM Internet Gateway software, or you can put your own
server or router there. Max Klingert, KB0RSQ, from our software team has been
experimenting with Linux appliance computers removed from point-of-sale
systems. He uses a release of Slackware Linux on a flash drive so no hard
drives (prone to failure in our experience) or fans would be needed on a
repeater connected computer. We provide a tiny Web site on each repeater, and
also a copy of Citadel, an open source mail and conferencing package. We also
wrote a packet AX.25 interface for Citadel. AX.25 packet radio gateways on
these appliance computers behind the repeaters are very easy to implement, as
the AX.25 Linux software is readily available and
the computers have serial interfaces.
Good — but No Cigar
This did not solve our problem though, as we wanted our database server remote
from the repeater. The repeater itself stubbornly resisted attempts to allow
native one-to-many connections between ID-1s. We think this was to reduce
broadcast type traffic on the radio link, which is simplex — this would waste
bandwidth. Max and Kelly Black decided to use the destination NAT feature of
Linux- the DNAT command. So each ID-1 user connected to the Linux box, and the
database system came in as well from an ID-1 to the repeater. The repeater and
ID-1s do not seem to track relationships between IP addresses and call signs,
so the users could go up to the repeater, and the Linux machine could establish
a call sign tunnel using another IP address block back to the database server,
which could be remote.
This was tested and solved one major problem. We could also then allow our
served agencies to set up ID-1 “data uplinks” to our repeaters from their
offices or trailers/vans. The second problem was geographic. The finish line at
the base of the State Capitol in St Paul, was in a low-lying area. The location
of the Net 2 van was on a reverse slope of a hill a few miles away. We passed
the hat and bought another repeater for Minneapolis, but a few weeks before the
race we were urged to perform live radio path testing from our sites. No luck —
the hills were in the way. Unlike 2 meter packet, L-band propagation is
unforgiving. More team members bought more radios, and we got a third and then
a fourth repeater. We called in some markers and these were installed in a
round-the-clock effort the week before the race on a series of building rooftop
sites in downtown Minneapolis. The Thursday before race weekend, we confirmed
we had solid RF paths between
our repeaters, the net control location and the finish line site.
D-STAR Takes the Heat
Race day was marked by hot and muggy weather and a record volume of runners
dropping out and needing medical attention and/or transportation. Net 2 (miles
19-22.5) was live to D-STAR from their van out on the course, and on race day
we had five D-STAR L-band data repeaters online to support the event. Despite
the data volume, the system worked perfectly with no issues. In 2008, with the
infrastructure now in place, we plan to focus on linking the repeaters via
radio and on development of a system to allow better integration of runner
information as requested by the physicians in the medical tent. This reinforces
our role, clearly stated in the FCC Part 97 Rules, of advancing the state of
the radio art and providing trained experts in modern emergency communications.
All photos courtesy Erik Westgard, NY9D.
Erik Westgard, NY9D, is an ARRL Life Member who lives in St Paul, Minnesota. He
is the Volunteer Medical Communications Director for the Medtronic Twin Cites
Marathon, and is employed as a consultant in the telecommunications industry.
He led the development of the 14567.org Statewide Packet network in Minnesota,
which is now converting to D-STAR. He has an MBA from Metropolitan State
University, and is a frequent contributor to QST.
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