science

High-speed multimedia radio

High-speed multimedia radio is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand High-speed multimedia radio rather than just read about it. In short: High-speed multimedia radio (HSMM) is the implementation of high-speed wireless TCP/IP data networks over amateur radio frequency allocations using commercial off-the-shelf (COTS) hardware such as 802.11 Wi-Fi access points. This is possible because the 802.11 unlicensed frequency bands partially overlap with amateur radio bands and ISM bands in many countries.

Key takeaways

High-speed multimedia radio belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect High-speed multimedia radio to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of High-speed multimedia radio from memory before moving on to harder problems.

Reference excerpt

High-speed multimedia radio (HSMM) is the implementation of high-speed wireless TCP/IP data networks over amateur radio frequency allocations using commercial off-the-shelf (COTS) hardware such as 802.11 Wi-Fi access points. This is possible because the 802.11 unlicensed frequency bands partially overlap with amateur radio bands and ISM bands in many countries. Only licensed amateur radio operators may legally use amplifiers and high-gain antennas within amateur radio frequencies to increase the power and coverage of an 802.11 signal.

Basics The idea behind this implementation is to modify commercial 802.11 equipment for use on licensed amateur radio frequencies. The main frequency bands being used for these networks are: 900 MHz (33 cm), 2.4 GHz (13 cm), 3.4 GHz (9 cm), and 5.8 GHz (5 cm). Since the unlicensed 802.11 or Wi-Fi frequency bands overlap with amateur frequencies, only custom firmware is needed to access these licensed frequencies. Such networks can be used for emergency communications for disaster relief operations as well as in everyday amateur radio communications (hobby/social).

Capabilities HSMM can support most of the traffic that the Internet currently does, including video chat, voice, instant messaging, email, the Web (HTTP), file transfer (FTP), and forums. The only differences being that with HSMM, such services are community instead of commercially implemented and it is mostly wireless. HSMM can even be connected to the Internet and used for web surfing, although because of the FCC regulations on permitted content, this is done only when directly used for ham radio activities (under Part 97). Using high gain directional antennas and amplifiers, reliable long-distance wireless links over many miles are possible and only limited by propagation and the radio horizon.

Bandwidths and speeds HSMM networks most-often use professional hardware with narrower channel bandwidths such as 5 or 10 MHz to help increase range. It is common for networks to use channel -2 with a 5 MHz bandwidth. For long-range links extending outside of metropolitan areas 802.11b DSSS modulations, 802.11g BPSK/QPSK, or 802.11ah (900 MHz) equipment can be used, further increasing range at the cost of speed.

US / FCC frequencies and channels The following is a list of the 802.11 channels that overlap into an amateur radio band under the FCC in the United States. Note that the 5 cm amateur band extends from 5.65 to 5.925 GHz, so that there are many frequencies outside the Part 15 ISM/UNII block used for 802.11a. 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. 802.11a channels 132, 136 and 140 are only available for unlicensed use in ETSI regions. Channels and frequencies marked in red should not be used.

Acronyms Used: (amateur radio) (ISM) (Radar)

Channels and power

FCC / United States

5 GHz All 802.11 standards in the 5 GHz band are OFDM. This band consists of 30 overlapping channels in the 5.650–5.925 GHz.(5 cm) band. The 802.11a/h/n/ac/ax/be standards use Orthogonal Frequency Division Multiplexing (OFDM) to transmit data and therefore is not classified as spread-spectrum. Because of this 802.11a/h/n/ac/ax/be hardware is not subject to the power rules in FCC Part 97 § 97.311 and the maximum allowable output power is 1,500 watts (W) PEP. This band also exists in ITU Regions 1 and 3, but it is narrower at 5.650–5.850 GHz.

2.4 GHz The amateur ratio band in 2.4 GHz consists of 8 overlapping channels in the 2.390–2.450 GHz (13 cm) 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 for 802.11b transmission in the USA is 10 W PEP. The 802.11g/n/ax/be standard use Orthogonal Frequency Division Multiplexing (OFDM) to transmit data and therefore is not classified as spread-spectrum. Because of this 802.11g/n/ax/be hardware is not subject to the power rules in FCC Part 97 § 97.311 and the maximum allowable output power is 1,500 W PEP.

3.4 GHz The 3.300–3.500 GH amateur ratio band is allocated on a secondary basis. It consists of 24 overlapping channels. The 802.11y standard uses Orthogonal Frequency Division Multiplexing (OFDM) to transmit data and therefore is not classified as spread-spectrum. Because of this 802.11y hardware is not subject to the power rules in FCC Part 97 § 97.311 and the maximum allowable output power is 1,500 W PEP. It exists in ITU Region 2 and 3, but not in ITU Region 1. The standardized frequency for 802.11y is 3.655–3695 GHz with 8 non-overlapping channels (and 6 overlapping ones built on top of them). This used to be a licensed range, but is now part of the 3.55–3.7 GHz Citizens Broadband Radio Service (CRBS) band, managed by an automated Spectrum Access System.

Frequency sharing

FCC / United States

5 GHz 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 privileges 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 (compared to 2.4 GHz), the noise level tends to be lower in many parts of the US but can be quite congested in urban centers and on mountaintops. The frequencies from 5.6-5.65 GHz (channel 132) should generally be avoided to prevent interfering with TDWR weather radar stations.

2.4 GHz 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 privileges to the Federal radiolocation service in the entire band and may not cause interference to these users. Amateur radio operators have primary privileges 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.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with High-speed multimedia radio

Start with the simplest possible case. Write down what High-speed multimedia radio claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to High-speed multimedia radio before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about High-speed multimedia radio ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of High-speed multimedia radio

In research: High-speed multimedia radio appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses High-speed multimedia radio in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: High-speed multimedia radio is common in secondary-school and first-year university syllabi. It links to neighbouring topics Packet radio, so understanding it makes those chapters shorter.
In everyday life: Look for High-speed multimedia radio outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study High-speed multimedia radio in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what High-speed multimedia radio means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain High-speed multimedia radio out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is High-speed multimedia radio in simple terms?

Why does High-speed multimedia radio matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study High-speed multimedia radio?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on High-speed multimedia radio.