Hinternet

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The correct title of this article is hinternet. The initial letter is shown capitalized due to technical restrictions.

hinternet is a name for the implementation of wireless data networks over amateur radio frequencies using commercial off-the-shelf (COTS) hardware such as 802.11 access points. Licensed amateur radio operators may use amplifiers and specialized antennas to increase the power and coverage of the 802.11 signal. This is also known as HSMM (High Speed Multi Media).

A typical piece of equipment used for HSMM (Linksys WRT54G)
A typical piece of equipment used for HSMM (Linksys WRT54G)

Contents

[edit] Basics

The idea behind this implementation is to use the 900MHz (33cm), 2.4 GHz (13cm), 3.4GHz (9cm), and 5.8 GHz (5cm) amateur radio bands under the FCC Part 97 Rules (Amateur Radio Service) instead of the Part 15 Rules (Unlicensed). This will enable amateur operators to legally use higher output power for wireless devices and allow for long range communications. Such communications can be used to assist in emergency communications, disaster relief operations and everyday amateur radio communications.

[edit] What can it do?

The "hinternet" can support most of the features that the internet currently does including video-chat, VOIP chat, instant messaging, webpages (HTTP), file transfer / sharing (FTP), and bulletin boards (BBS) / forums. The only differences being that on the hinternet such services are community instead of commercially implemented and the "hinternet" is mostly wireless. The hinternet can even be connected to the regular internet and used for "web-surfing" although because of the FCC regulations on permitted content this is rarely done. Using high gain antennas and amplifiers reliable long distance wireless links over many miles are possible and only limited by the radio horizon.

[edit] Frequencies and Channels

The following is a list of the 802.11 channels that overlap into an amateur radio band. Note that the 5 cm amateur band extends from 5650 to 5925 MHz, so that there are many frequencies outside the Part 15 ISM/UNII block used for 802.11a. Some equipment can be programmed to operate on these 'extra' channels, some cannot. Many commercial grade 802.11a access points can also operate in-between the normal channels by using 5 MHz channel spacing instead of the standard 20 MHz channel spacing.

802.11b/g (13cm)
Channel Center Frequency
1 2.412 GHz
2 2.417 GHz
3 2.422 GHz
4 2.427 GHz
5 2.432 GHz
6 2.437 GHz
  
802.11a (5cm)
Channel Center Frequency
132 5.660 GHz
136 5.680 GHz
140 5.700 GHz
149 5.745 GHz
153 5.765 GHz
157 5.785 GHz
161 5.805 GHz
165 5.825 GHz

The following images show the overlapping relationship of the part15 unlicensed bands and the part97 licensed bands. The images are not to scale.

2.4 GHz 802.11b/g



5.8 GHz 802.11a


[edit] Channels and Power

[edit] 802.11a

The 802.11a amateur radio band consists of eight non-overlapping channels in the 5.8 GHz (5cm) band. The 802.11a standard uses OFDM or "Orthogonal Frequency Division Multiplexing" to transmit data and therefore is not classified as spread-spectrum. Because of this 802.11a hardware is not subject to the power rules in FCC Part 97 §97.311 and the maximum allowable output power is 1500 Watts PEP.

[edit] 802.11b

The 802.11b amateur radio band consists of six overlapping channels in the 2.4 GHz (13cm) band. The 802.11b specification uses Direct Sequence Spread Spectrum (DSSS) to transmit data and is subject to the rules of FCC Part 97 §97.311. Therefore the maximum allowable power output is 100 Watts PEP. If the transmitter power exceeds 1 Watt, the station must use automatic power control.

[edit] 802.11g

The 802.11 g amateur radio band consists of six overlapping channels in the 2.4 GHz (13cm) band. The 802.11 g standard uses OFDM or "Orthogonal Frequency Division Multiplexing" to transmit data and therefore is not classified as spread-spectrum. Because of this 802.11 g hardware is not subject to the power rules in FCC Part 97 §97.311 and the maximum allowable output power is 1500 Watts PEP.

[edit] Frequency Sharing

[edit] 802.11a

The 5 cm band is shared with the fixed-satellite service in ITU Region 1, and the radiolocation service. In ITU Region 2 (US) the primary user is military radiolocation, specifically naval radar. Amateur radio operators have secondary privilages to the Federal radiolocation service in the entire band and may not cause interference to these users. Amateur operators are allocated this band are in a co-secondary basis with ISM devices and space research. Amateur, space research, and ISM operators each have the "right to operate". Due to the lack of a high number of Part 15 users, the noise level tends to be very low in many parts of the US, but in urban centers and on mountaintops it can be quite congested.

[edit] 802.11b/g

The 13 cm band is shared with Part 15 users as well as the Federal radiolocation service, and ISM (industrial, scientific, medical) devices. Amateur radio operators have secondary privilages to the Federal radiolocation service in the entire band and may not cause interference to these users. Amateur radio operators have primary privilages to ISM devices from 2.390-2.417 GHz and secondary privileges from 2.417-2.450 GHz. Because of the high number of Part 15 users, the noise level in this band tends to be rather high.

[edit] Pros and Cons

[edit] 802.11a

[edit] Pros

Since the channels in 802.11a do not overlap stations may be placed close together without interference. Channels 132, 136, 140, & 165 are also inaccessible to unlicensed (Part 15) users inside the United States adding inherent security to these channels. There are also less users on these bands leading to better signal to noise ratios. The modulation scheme used is OFDM and as such the maximum power output is 1500 Watts PEP with no power control required.

[edit] Cons

Hardware for 802.11a is less popular than hardware for 802.11b/g and is therefore more expensive. Either modified hardware or foreign software drivers may be needed in order to access channels 132, 136, 140, & 165. Also, given the same power output and antenna gain an 802.11b/g (2.4 GHz) signal will have a greater range than an 802.11a (5.8 GHz).

[edit] 802.11b

[edit] Pros

Hardware for this band is very popular and therefore relatively inexpensive. Given the same power output an 802.11b (2.4 GHz) signal will travel farther than an 802.11a (5.8GHz) signal.

[edit] Cons

Due to the popularity of this band the chance for interference both to and from unlicensed users is high. Security is also a major concern since the frequencies are shared with unlicensed users thereby increasing the chance of wardriving attacks. Spread spectrum is used as the modulation scheme in 802.11b and therefore stations transmitting over 1 Watt must use automatic power control. The bandwidth of the signals in 802.11b/g are 22 MHz wide and the channel spacing is only 5 MHz. Because of this overlap only 2 of the authorized channels (1 and 6) are spaced far enough apart to be used in the same area without causing interference to one another. Channel 6 however is the default channel for 802.11b.g hardware and the most likely frequency on which to both cause and receive interference. Also AMSAT has requested that HSMM operators stay away from 802.11b/g channel 1 to prevent interference to satellite operations. It was recommended in CQ magazine that users use channels 3 and 5.

[edit] 802.11g

[edit] Pros

Hardware for this band is very popular and therefore relatively inexpensive. Given the same power output an 802.11b (2.4 GHz) signal will travel farther than an 802.11a (5.8GHz) signal. The modulation scheme used is OFDM and as such the maximum power output is 1500 Watts PEP with no power control required.

[edit] Cons

Due to the popularity of this band the chance for interference both to and from unlicensed useres is high. Security is also a major concern since the frequencies are shared with unlicensed users, increasing the chance of wardriving attacks. The bandwidth of the signals in 802.11b/g are 22 MHz wide and the channel spacing is only 5 MHz. Because of this overlap only 2 of the authorized channels (1 and 6) are spaced far enough apart to be used in the same area without causing interference to one another. Channel 6 however is the default channel for 802.11b.g hardware and the most likely frequency on which to both cause and receive interference. Also AMSAT has requested that HSMM operators stay away from channel 1 to prevent interference to satellite operations. It was recommended in CQ magazine that users use channels 3 and 5.

[edit] Identification

As with any amateur radio mode stations must identify at least once every 10 minutes. One acceptable method for doing so is to transmit one's callsign inside of an ICMP echo request commonly know as a ping. If the access point is set to "master" then the users callsign may be set as the "SSID" and therefore will be transmitted at regular intervals.
Be aware that 802.11 hardware will transmit and receive the entire time that it is powered on even if the user is not sending data.

[edit] Security

Because amateur transmissions may not be encoded or encrypted in any way, security measures that are implemented must be published. This makes it very difficult to keep unauthorized users from accessing HSMM networks. Current schemes include using MAC address filtering, WEP and WPA/WPA2. MAC address filtering and WEP are both hackable by using freely available software from the internet, making them the less secure options. Per FCC rules the encryption keys themselves must be published in a publicly accessible place if using WEP, WPA/WPA2 or any encryption, thereby undermining the security of their implementation.
Using professional or modified hardware it is possible to operate on 802.11a channels that are outside the FCC authorized Part15 bands but still inside the 5.8 GHz (5cm) amateur radio band. Transverters or "frequency converters" can also be used to move HSMM 802.11b/g operations from the 2.4GHz (13cm) band to the 3.4GHz (9cm) amateur radio band. Moving HSMM operations to 'licensed only' frequencies and away from unlicensed Part15 users offers security without the need for access controls such as MAC filtering and encryption.

[edit] Custom Frequencies

Using professional grade commercial hardware or modified consumer grade hardware it is possible to operate 802.11 on channels that are outside of the normal FCC allocated frequencies for unlicensed users but still inside am amateur radio band. Some of these frequencies are inside the 3.4GHz (3cm) band and the 5.8GHz (5cm) amateur radio bands, thereby providing better security and interference characteristics to amateur radio operators. While using amateur-only frequencies all but alleviates the security concerns of using 802.11, the relative high cost of such devices is a large deterrent to their widespread deployment.

[edit] 3.4GHz Transverters

Frequency conversion involves the use of transverters that convert the operating frequency of the 802.11b/g device from 2.4 GHz to another band entirely. Transverter is a technical term and is rarely used to describe these products which are more commonly known as frequency converters, Up/Down converters, and just converters. Transverters currently exist commercially that can convert a 2.4 GHz 802.11b/g signal to the 3.4 GHz (9cm) band which is not authorized for unlicensed Part15 users.

[edit] 5.8GHz Custom Frequencies

Using professional grade hardware or modified consumer grade hardware it is possible to operate on 802.11a channels 116-140 (5.57-5.71GHz) and channels above 165 (>5.835GHz). These frequencies are outside of the FCC allocated Part15 unlicensed band, but still inside of the 5.8GHz (5cm) amateur radio band. Modifying consumer hardware to operate on these expanded channels often involves installing after-market firmware and changing the "country code" setting of the wireless card. When buying professional grade hardware, many companies will authorize the use of these expanded frequencies for a small additional fee.

[edit] See also

[edit] External links

[edit] Sources

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