High Speed Multi Media

Using Part 15 Wireless Ethernet
Devices For Amateur Radio

 

 

Background:

The 13 centimeter band, 2300-2450 and 5250-5650MHz became available for amateur use in 1945.   The 5 centimeter band was realigned to the present allocation, 5650 to 5925 in 1968.  The 33 centimeter, 902-928 MHz was allocated to the amateur radio service in 1985.

At the same time of the 33 centimeter allocation, the FCC opened the industrial, scientific and medical (ISM) bands to Part 15 radio use in 1985.  Prior to about 1980, the ISM bands were considered unacceptable for radio communication because of harmful interference created by such equipment. But several companies and industry groups petitioned the FCC and showed that by using spread spectrum modulation, low-power radios could coexist with ISM radiators.  (It should be noted that using unlicensed equipment to provide services to third parties wasn't in this original scope.)

By 1995 it was realized that the complete system authorization rules of Part 15.247 were burdensome for device-based service providers that were starting to emerge. At that time a few new unlicensed bands were created to address this. These include the Unlicensed PCS band, and the more common Unlicensed National Information Infrastructure (U-NII) bands, which has it's own rules in Part 15.401 to 15.407

There are three U-NII bands, each to address the mixed use. The first 5 GHz chunk is for indoor use with integrated antenna like the original Part 15/ISM sharing scope. The second chunk is for mixed use, and the third for outdoor use with provisions for a user-installable antenna.

Packet radio and the use of TCP/IP for wireless networking by radio amateurs began in the 1970's.  This was about the same time Defense Advanced Research Projects Agency (DARPA) was becoming the fundamental pioneer in the call for a global network that later became the internet.  (DARPA is an agency of the United States Department of Defense responsible for the development of new technology for use by the military)

In 1989 Glenn, N6GN first described an inexpensive 2-Mbit/s microwave data link,  to build an amateur radio network capable of variety of applications, enabling amateurs to share resources. "Remote digital control of repeaters or even complete stations, including audio or video uplinks and downlinks, can be supported. Conventional voice repeaters (analog) may be replaced by digital hardware for completely digital round tables. Since this data can be transmitted anywhere the network permits..."  A decade later after the internet became mainstream, John, KE5FX detailed an Experimental Microwave Data Link for 10-Megabit Ethernet based on Glenn's work.  John, noted that "little progress has been made towards realizing the benefits of high-speed data networking in the Amateur Radio realm" and documented his work  "to help bring Amateur Radio into the twenty-first century."

In 1981 the FCC authorized spread spectrum  on amateur frequencies.  In 1989 Al Broscius, N3FCT suggested the use of Part 15 Spread Spectrum wireless ethernet devices that were becoming available for amateur packet radio use.  

Implications for the Radio Amateur- an excerpt from "License-Free Spread Spectrum Packet Radio" by N3FCT in 1989

There are numerous manufactures of these spread spectrum networking devices. They operate on the shared 900 MHz (33 cm), 2.4 (13 cm) and 5.7 (5 cm) GHz bands with speeds between 1 and 54 Mbps.

1998 Wireless LAN product/feature comparison- by Barry McLarnon, VE3JF (dated) (mirrored in 1998 from http://hydra.carleton.ca/info/)
Amateur Band Allocations and Permissible Power Comparison - for the 900 MHz, 2.4 & 5.7 GHz bands 

At the ARRL 9th Computer Networking Conference in 1990, Phil Karn, KA9Q, delineated A New Channel Access Method conceived for Packet radio.  This Request to Send / Clear to Send scheme was later adopted by IEEE 802.11.

In early 1997 TAPR began development of a 1 watt, 128 Kbps 900 MHz FHSS radio, suggesting this is the future for amateur packet radio.

At a workshop at the 1997 TAPR/ARRL Digitial Communications Conference, Barry McLarnon, VE3JF gave a primer for digital experimenters on VHF/UHF/Microwave Radio propagation. His paper attempts to provide some insight into the nature of radio propagation in that part of the spectrum (upper VHF to microwave) used by experimenters for high-speed digital transmission.

In late 1999 the FCC relaxed Amateur Spread Spectrum rules. Now allowing any commercially available Part 15 SS device to be reclassified under Part 97. (Prior only certain spreading codes where allowed.  However from roughly 1996 to 1998, TAPR encouraged hams interested in spread spectrum experimentation using commonly available hardware to obtain special temporary authorization (STA) from the FCC.)

Part 97.311- current Amateur spread spectrum rules

In late 1999 we formed GBPPR to encourage advancement in packet radio using readily available - off the shelf hardware.   Some of our media attention included CQ and QST magazines, postings to Slashdot and QRZ.  From this our more well noticed work included:

     915 MHz BDA schematic, 2.4 GHz BDA schematic, Interactive Wireless Design Utilities

In mid 2001 the ARRL's High Speed Multimedia Working Group (HSMM) was formed & began encouraging widespread use of spread spectrum modes of communications such as IEEE 802.11 on amateur radio frequencies.  Unveiled at Dayton 2002 was Icom's 1.2 GHz Digital D-Star system.  In the fall of 2002 TAPR announced it would discontinue it's stalled 900 MHz FHSS radio efforts.  In March 2006, the ARRL requested to drop the automatic power control requirement on amateur spread spectrum above 1 watt, as it impractical and deters experimentation (granted in 2011).  Shortly thereafter, the HSMM working group fell apart due to dissatisfaction and friction with their recommendations to the ARRL board of directors.

In June 2004, open source advocates discovered that the Linksys WRT54 series routers are based on Linux components and thusly asked for the source code to be released.  This opened the door for aftermarket/third-party firmware developments.

In 2006 an informal hardware abstraction layer (HAL) driver is reached with the Atheros wireless chipset.  This as instigated by open source advocates, and benefits hams.  It enables operation outside the Part 15 overlap, as well as half and quarter rate wide channels using  reflashed/enabled consumer-grade Atheros chipset based gear.  (A formal open HAL is reached with the manufacture in July 2007)

In 2005 pending the Atheros HAL hacking, a company called Ubiquiti Networks emerges.  Their "frequency freedom technology" uses onboard transverters opening the possibility of 400MHz to 9GHz integrated radio technology.  In August 2007, they release a competing WiMax product.  The XR3; specifically designed for long-distance, outdoor broadband wireless applications.  This worked out well for us hams, a their XR3-3.5 version yields over thirty 3 GHz non-overlapping full-width channels unshared with Part 15 unlicensed devices.  In February 2009 they release an outdoor mountable, POE, 3 GHz NanoStation.

In the Fall of 2008, a group of amateurs from the Texas area announced development of their own custom firmware for the WRT-54G to enable HSMM-Mesh networking.

In 2011 a company based in Singapore, called Doodle Labs offers the industries first OFDM broadband Atheros based radio transceivers for the Amateur Radio Bands capable of 5 MHz channel widths in the 420-450 MHz, 70 cm band.  In 2012 a second company based out of Canada, called Xagyl Communications also makes available a Atheros based radio capable of operation on the 70cm band.

Today:

We know it is possible as unlicensed Part 15 devices to obtain omnidirectional ranges up to about 5 miles and directional ranges up to about 17 miles using high gain antennas.  There are five major bands suitable for use by hams transmitting spread spectrum: 420-430 MHz, 900 MHz, 2.4 GHz, 3.4 GHz, and 5.8 GHz.

We should also realize that greater communication ranges are possible (if necessary) by reclassifying these devices under Part 97. We are then allowed to modify them using pre-amps, RF amplifiers and high gain antennas. Then by placing a central routing node in the middle of town on top a tall building/tower or hill they can serve as a inexpensive high speed supplement/alternative to existing packet radio systems.  Mesh networking protocols can make up for some of the line of site-microwave issues, enabling high-speed self-configuring access over a wide area. 

Part 97 vs Part 15 & Permissible Power Comparison - and clarification
Price comparison- between a conventional packet setup and a Symphony setup
Misc. Part 97 clarifications- pertaining to this application

True some urban areas may be very infested with Part 15 devices already. But you have 3 bands to choose from, and you shouldn't have many problems if you use FHSS and or reduced channel widths, with one watt amplifiers before your antenna polarized the opposite of everyone else (typically horizontal).

My Experiences:

I have experimented with Proxim's Symphony 1.6 Mbps Frequency Hopping Spread Spectrum 2.4 GHz network card. It was only $130 and as a Part 15 device coupled with an old 24 dB MMDS 2.5 GHz partial screen parabolic antenna (previously used for receiving rural wireless cable) you could easily obtain ranges up to 6 miles line of sight.

Low Cost Wireless Network How-To- our abundance of documented, experiences, work and research (which includes homebrew bi-directional amplifier designs and path-loss calculators)

Other Peoples Experiences:

During my Proxim Symphony experimentation I sought out reports from other hams who had attempted long distance communications paths:

Symphony based links: KE6WED, VE3JF, K5OKC, and 4Z4ZQ

Other hams exploring and using this technology using different hardware: KO6YQ, N3WFI, KG6DFV

Re-classifying:

All commercially available wireless ethernet devices are suitable for Amateur use. However there are 3 things you may need to pay attention to when re-classifying.

  1. You need to identify your station every 10 minutes by transmitting your callsign in ASCII or by some other method that is publicly documented.
    I suggest manipulating your devices MAC address to represent your callsign, or have a script send out a ping every 10 minutes with your callsign embedded in it,. (more info)
  2. You will need to keep your operations within the 2400-2450 MHz amateur overlap if you plan to re-classify under Part 97. (this is only an issue on the 2.4 GHz band with FHSS, all other bands have full overlap & DSSS systems can be set by user for center freq below 2.45)
    Order your Symphony directly from Proxim and send a copy of your license and they will change your cards country code shifting operation below 2450. (more info)
  3. If you need to amplify your spread spectrum signal over 1 watt PEP you will need to incorporate automatic transmitter power control.
    You may need to buy a expensive commercial amplifier (such as Teletronics Bi-directional SmartAmp) to accomplish this. (more info)

What can it do?

It all seems to stem from the ARRL HSMM working group from a number of years ago.  Despite that group falling apart, independently amateurs all over the place have embraced
the technology.  It's great in my opinion.  

First and foremost it can put our microwave frequency allocations to good use.   These allocations (23cm-300GHz) make up 99% of hams total available frequency allocations.  Yet, it's estimated that only 1% of hams are involved with any microwave operations.

As interest in voice repeaters continues to wane, multi-media networks do make perfect sense.  These more modern types of networks have the potential to draw new blood into the hobby.  New hams who have software skills that can help the community with software defined radio and so forth.

High Speed Multi Media data links can support most of the traffic that the Internet currently does, including; remote printing and facsimile, video conferencing & instant messaging, voice, the Web (HTTP), file transfer (FTP), and forums.   D-Star Digital voice and data, Voice Over IP using SIP & Asterisk private branch exchange (PBX) open source telephony switching technology's well as Electronic Mail even via WinLink, AX.25 and more, can all be supported over a High Speed Multi Media network.  Talk about flexibility!

The only differences being that on HSMM networks such services are community instead of commercially implemented and are mostly wireless.   Thusly, in the event of a back-hoe hitting a fiber optic cable or other catastrophe, such amateur wireless networks can be used to temporarily bridge the broken connection.

The "drag and drop" flexibility of network file sharing protocols over a HSMM network can offer reliable exchange of large image files, email, word-processing and other files that emergency responders and served agencies find invaluable.  

Emergency communications offer the greatest opportunity for HSMM technology to excel and for amateurs to push the envelope in the public service sector, using this technology. Low power requirements, low cost, portability, point-to-point, point-to-multipoint and multicast capabilities, coupled with high bandwidth, makes HSMM an excellent technology for "on-the-spot" emergency communications.  

From the Level 1 ARES training manual: "Do not think about how to use ham radio to send the message - just think about the best and fastest way to send it".

Remote digital control (and linking) of repeaters or even complete stations, including audio or video uplinks and downlinks, can be supported. Conventional voice repeaters (analog) may be replaced by digital hardware for completely digital round tables. Since this data can be transmitted, routed and relayed anywhere the network permits, this is a great way to connect repeaters together that have quite a distance between them (or poor radio path).

Ham radio used to be a good starting place for many who later entered broadcast and electronics careers.  Today those positions are few and far between due to disposable electronics and consolidation of engineers with mega broadcast groups.  What is the most notable/abundant "tech" career today is IT (information technology) work.  

In my humble and simple opinion: These types of networks are long over due, and I am glad they are continuing to grow.  It helps ham radio stay relevant.  And ham radio provides a platform for those who want to learn about wireless technology by experimenting.

The cost of the equipment has finally come down to the point where even a modestly funded amateur radio club can afford to set up a small regional network by themselves.  So, if your like me and are seeking a simple way to build a high speed, affordable, RF network, where you mimic the internet and have web, mail, and FTP services, streaming digital audio/video over IP, conferencing, and so on, I encourage you to look into this technology and use it. (This is now commonly referred to as High Speed Multimedia- HSMM.)  If you use this technology and would like to share your experiences, or if you have questions, you may contact me . Also feel free to link to this document and or reprint any portion of it.

Steve Lampereur, KB9MWR

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