Ham Radio Ethernet - High Speed Amateur Packet Radio

 

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 wasnít 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 itís 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 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.

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

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.

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.  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 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.

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.

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.

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, 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 having 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)

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 the "Hinternet." or 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

Hinternet overview GBPPR Main Projects Main