Introduction to Millimeter Wave Technology for E-Band

E-Band MMW Summary

Millimeter Wave (MMW) using E-Band and V-Band is a technology for high speed (10Gbps) high capacity wireless links, ideal for urban areas. Using high frequency microwave in the E-Band (70-80GHz) and 58GHZ to 60GHz (V-Band) spectrum, links can be densely deployed in congested cities without interference, and without need for digging for cables and fibre optics, which can be costly, slow and highly disruptive. By contrast, MMW links can be deployed in hours, and moved and reused on different sites as network requirements evolve.

History of MMW

In 2003, the North American Federal Communications Commission (FCC) opened the high frequency 70, 80, and 90 GHz millimeter-wave (MMW) bands for commercial and public use, offering around 13 GHz of spectrum. This enabled the development of high-speed, point-to-point radio links, delivering:

• Full-duplex data rates up to 1.25 Gbps

• Carrier-class availability (99.999%)

• Transmission ranges close to or over one mile

Due to their high capacity and cost-effectiveness, MMW radios are reshaping mobile backhaul and enterprise “last-mile” connectivity solutions.

Regulatory Background

In October 2003, the FCC opened 13 GHz of spectrum in the 71–76 GHz, 81–86 GHz, and 92–95 GHz ranges (collectively known as the E-band) for commercial and high-density fixed wireless use. This was a landmark decision, enabling, for the first time, full-duplex gigabit-speed wireless links over distances of one mile or more at carrier-class availability levels.

Key highlights:

• Largest spectrum release in FCC history for licensed commercial use

• Added 20% more to total FCC-approved bands

• Provides 50 times more bandwidth than the entire cellular spectrum

• Enables gigabit Ethernet and beyond with relatively simple radio designs

• Rain fade is manageable, allowing for multi-mile link distances

The ruling also introduced an innovative online licensing system, offering fast and affordable registration with frequency protection. This move has since inspired global adoption of millimeter-wave (MMW) spectrum for fibre replacement, last-mile wireless access, and high-speed broadband.

Target Markets and Applications for High Capacity “Last-Mile” Access Connectivity

In the US, only 13.4% of the roughly 750,000 commercial buildings with 20+ employees are connected to fibre networks, despite increasing demand for high-speed Internet (e.g. DS-3 at 45 Mbps or faster). The remaining 86.6% rely on slower copper-based connections, which are expensive (e.g. ~$3,000/month for DS-3).

Although 75% of non-fibre buildings are within one mile of existing fibre, the cost of laying new fibre – up to $250,000 per mile in major cities – and moratoriums on digging in urban areas, make fibre expansion economically and logistically difficult. In Europe, fibre penetration in commercial buildings is even lower-estimated at around 1%.

Millimeter-wave (MMW) radio systems offer a practical solution for “Last Mile” high-speed access, meeting carrier-class reliability standards at a fraction of the cost of fibre. When compared to laying just one mile of fibre in a major metropolitan US or European city, MMW gigabit Ethernet radios can be deployed for as little as 10% of fibre trenching costs, enabling much faster Return on Investment (ROI) and expanding service feasibility. Many high data rate applications can now be served and are economically feasible with MMW radio technology, including:

• CLEC and ILEC fibre extensions and replacements

• Metro Ethernet backhaul and ring closures

• Wireless campus LAN extensions

• Fibre backup and path diversity in campus networks

• Disaster recovery solutions

• High capacity SAN connectivity

• Redundancy, portability and security for Homeland Security and Military

• 3G/WiFi/WiMAX backhaul in dense urban areas

• Temporary or portable high-definition video and HDTV transport links

Why use E-Band MMW Technology?

Among the three newly opened millimeter-wave (MMW) bands, the 70 GHz and 80 GHz ranges have seen the most interest from manufacturers due to their 5 GHz of full-duplex bandwidth, ideal for Gigabit Ethernet (GbE) and even 10-40 Gbps transmissions with advanced modulation.

• Direct data conversion (OOK) and low-cost diplexers enable reliable, cost-effective radio designs.

• Using only the 71-76 GHz band for full-duplex GbE transmission has benefits for deployments near astronomical sites and in international markets.

In contrast, the 92-95 GHz band is less attractive due to its split allocation and a 100 MHz exclusion zone at 94 GHz. It is more suited for short-range indoor or specialised applications and is not discussed further here.

Propagation and Attenuation Characteristics

Figure 1 shows the variation of atmospheric attenuation with frequency. The relatively low atmospheric attenuation window between 70 GHz and 100 GHz makes E-band frequencies attractive for high capacity wireless transmission.

• E-band (70–80 GHz) offers low atmospheric attenuation, enabling multi-mile transmission under clear weather.

• At 60 GHz, oxygen absorption spikes, severely limiting range.

• Beyond 60 GHz, a low-attenuation window opens up again from 70–100 GHz, making E-band ideal for high-capacity links.

• Attenuation increases beyond 100 GHz due to more molecular absorption (O₂ and H₂O).

Weather Impacts on Transmission

Figure 1 also shows how rain and fog impact attenuation in microwave, millimeter-wave and infrared optical bands that start around 200 THz and that are used in FSO transmission systems.

• Rain impacts signal strength slightly depending on frequency and rainfall rate.

• Fog causes negligible attenuation at millimeter-wave frequencies, but severely affects Free Space Optics (FSO) systems operating in the infrared band (~200 THz), explaining why FSO fails in fog, while MMW continues to operate reliably.

Transmission Distances for E-Band

As with all high-frequency systems, rain attenuation is the main factor limiting the practical transmission distance of E-band radio links, as shown in Figure 2. Heavy rain (e.g. at a rate of 100 mm/hr) can cause significant signal loss, up to 30 dB/km. Such intense rain is usually brief and localised, such as short cloud bursts. These short-duration outages mostly affect longer links, as storms typically move quickly across the path.

Decades of global rainfall data from the International Telecommunication Union (ITU) and others allow engineers to design reliable links by predicting outage durations, adjusting link lengths and margins, and understanding rainfall patterns by region. Rainfall characteristics and relationships between rainfall rate, statistical rain duration, rain drop sizes etc. are well-understood.

The ITU rain zone classification ranks areas from Region A (least rain) to Region Q (most rain) to guide deployment planning.

Figure 3: ITU rain zone classification of different regions around the world

80% of the continental US falls under ITU rain zones K or lower, meaning systems must handle up to 42 mm/hr of rainfall to achieve 99.99% availability. The highest rainfall in North America can be observed in Florida and along the Gulf Coast, classified as zone N. Australia experiences less rain, with the most populated areas in zones E and F (under 28 mm/hr).

By combining rainfall data with attenuation curves (Figures 2-4), it is possible to predict system performance. 70/80 GHz radio transmission equipment can achieve GbE connectivity at 99.99–99.999% availability at distances close to or over 1 mile, and 99.9% availability at over 2 miles. Using ring or mesh topologies, effective distances can double, thanks to path redundancy and the localised nature of heavy rain.

Figure 4: ITU rain zone classification for North America and Australia

A key advantage of millimeter-wave (MMW) technology over free space optics (FSO) is its resilience to environmental impairments. At 70/80 GHz, thick fog causes only 0.4 dB/km attenuation, while FSO systems suffer >250 dB/km, making them impractical for long distances. E-band radios are also unaffected by dust, sand, snow, and other path impairments, ensuring higher reliability across more challenging conditions.

Alternative High Data Rate Wireless Technologies

As alternatives to E-band wireless technology, there are a limited number of viable technologies capable of supporting high data rate connectivity. This section of the white paper provides a short overview.

Fibre-Optic Cable

Fibre-optic cable offers the highest bandwidth and supports very high data rates over long distances. While widespread in long-haul and inter-city networks, “Last-Mile” access is limited due to high installation costs, right-of-way-issues, and lengthy delays from construction, environmental and bureaucratic challenges. For these reasons, many cities are restricting trenching to avoid traffic disruption and public inconvenience.

Microwave Radio Solutions

Microwave radio provides high-speed point-to-point links, supporting full-duplex 100 Mbps Fast Ethernet and up to 500 Mbps per carrier in the 4-42 GHz range. However, the spectrum is limited and often congested in traditional microwave bands, and typical licensed spectrum channels are narrower than in the E-Band spectrum.

Figure 5: Comparison between high data rate microwave radios and a 70/80 GHz radio solution.

In general, licensed channel widths are 30 MHz or less, with some bands offering up to 56 Hz, and 112 MHz only in higher frequency, short-range bands. To achieve higher data rates (up to 880 Mbps), systems must use complex modulation schemes such as 1024QAM, which limit transmission distance and increase system complexity and cost. These bands also suffer from the limited spectrum, broader antenna beamwidths, and high QAM sensitivity to interface. As a result, dense urban deployments using traditional microwave solutions are difficult and inefficient compared to E-band solutions.

60 GHz (V-Band) Millimeter Wave Radio Solutions

The 60 GHz spectrum, particularly the 57–66 GHz range, is regulated differently across regions. In the US, the FCC has allocated a relatively wide 57–64 GHz block, enabling full-duplex Gigabit Ethernet operation. However, many other countries, such as Germany, France, and the UK, have access only to narrower, channelised portions of this band, making high-data-rate, cost-effective 60 GHz radio solutions less feasible outside the US. Even within the US, the high atmospheric absorption caused by oxygen (see Figure 1) significantly limits propagation, restricting reliable link distances to about 500 meters for achieving carrier-class availability (99.99–99.999%). The 60 GHz band is license-free in the US, making it attractive due to ease of use, but it lacks protection from interference. Overall, while 60 GHz radios may be suitable for short-range deployments in the US, they are not viable for longer links or where high reliability is required.

Free Space Optics (FSO, Optical Wireless)

Free Space Optics (FSO) uses infrared laser beams to transmit high data rates (1.5 Gbps and above) between remote locations. It is secure, interference-resistant due to its narrow beam, and operates license-free worldwide. However, FSO performance is severely impacted by visibility-reducing conditions such as fog, dust, and sandstorms, which can cause extreme signal attenuation- up to 130 dB/km in fog. These weather events are often localised, unpredictable, and can last for hours or days, leading to prolonged outages. As a result, achieving high availability levels (99.99-99.999%) typically limits FSO use to short distances of a few hundred meters, particularly in foggy or dust-prone areas. While FSO is a cost-effective solution for short-range connections, its reliance on clear line-of-sight and sensitivity to atmospheric conditions inherently restrict its use to limited-range deployments, often requiring backup link technologies for reliable operation.

The majority of industry experts agree that FSO technology can offer an interesting and potentially inexpensive alternative in wirelessly connecting remote locations over shorter distances. However, the physics of signal attenuation in the infrared spectrum will always restrict this technology to very short distances.

Table 1: Comparison chart of commercially available high data rate wireline and wireless transmission technologies

Commercially Available Millimeter-Wave Solutions

The CableFree Millimeter-wave product portfolio includes point-to-point radio solutions operating from 100 Mbps to 10 Gbps (10 Gigabit Ethernet) speeds in the licensed 70 GHz E-band spectrum, and up to 1Gbps in the unlicensed 60 GHz spectrum. The systems are available with different antenna sizes to meet the customer’s availability and distance requirements, while remaining competitively priced. Unlike other solutions that use both 70 and 80 GHz bands simultaneously, Wireless Excellence’s E-band radio solutions operate exclusively in the lower 5 GHz frequency band of the licensed 70/80 GHz E-band spectrum. This avoids potential deployment issues near astronomical or military sites in Europe, where the 80 GHz band may be restricted. The systems are easy to deploy, and due to the low voltage power feed of 48 volts direct current (Vdc), no certified electrician is required for installing the system. Photographs of the Wireless Excellence products are shown in Figure 6 below.

Figure 6: CableFree MMW radios are compact and highly integrated. 60cm antenna version shown.

 

Summary and Conclusions

To meet growing demands for high-capacity network interconnectivity, wireless solutions now offer fibre-like performance at significantly lower costs compared to laying or leasing fibre. This is especially important since fibre access remains limited- only 13.4% of US commercial buildings with 20+ employees are connected, with even lower rates in many other countries.

Among the available technologies, licensed E-band systems (70/80 GHz) stand out for delivering gigabit speeds with carrier-class availability over distances of one mile or more. In the US, a 2003 FCC ruling enabled commercial use of this spectrum through a quick and inexpensive online licensing process, with other countries following suit. While unlicensed 60 GHz radios and free-space optics (FSO) also support gigabit Ethernet, they are limited to much shorter distances- typically under 500 meters- when high availability is required.

References

1. ITU-R P.676-6, “Attenuation by Atmospheric Gases,” 2005.
2. ITU-R P.838-3, “Specific Attenuation Model for Rain for Use in Prediction Methods,” 2005.
3. ITU-R P.837-4, “Characteristics of Precipitation for Propagation Modeling,” 2003.
4. ITU-R P.840-3, “Attenuation Due to Clouds and Fog,” 1999.

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