State-Wide Microwave Network Case Study: Extra High Power Radios

State-Wide Microwave Network Case Study: Extra High Power Radios

This large western US state had a longtime relationship with a microwave radio vendor and would have continued buying from them if their radios and support evolved with the State’s needs. However, over time its needs changed and it had to have more capabilities from its communications network. But it did not want to unnecessarily build new sites and erect costly new towers.

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Case Study: When Extra High Power Can Reduce Need for Space Diversity

Case Study: When Extra High Power Can Reduce Need for Space Diversity

When designing microwave networks, backhaul engineers have a wide variety of techniques at their disposal. One method that remains highly effective is Space Diversity (SD). With SD, two antennas separated by some distance can increase the availability of a link from something less than 99.999 percent to in excess of five-nines uptime. However, the introduction of a second parabolic antenna on a microwave path poses a substantial increase in the capital expenditure (capex) budget.

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Quantifying the Benefits of Extra High Power Radios

Quantifying the Benefits of Extra High Power Radios

IRU-600-EHP-Radios-Enable-Use-of-Cheap-Small-Antennas-Aviat-Blog

Figure 1: 8-foot antenna (left) clearly much bulkier than a 3-foot antenna (right in carton). Basketball included to indicate relative scale.

You may have noticed we’ve been talking a lot lately about our new 39dBm EHP radio (the most powerful digital microwave radio ever built by the way). We’ve been getting a phenomenal response to this product mostly because of the real business benefits it delivers…benefits largely related to the antenna.

As a rule of thumb in microwave backhaul, the more powerful the radio (i.e., system gain) the smaller the antenna has to be (i.e., overall diameter). More than any other factor, smaller antennas drastically lower the total cost of ownership for microwave.

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How Microwave Networking Enables Nationwide 4G

How Microwave Networking Enables Nationwide 4G

LTE mobile connectivity now exists in many more urban places than not. Virtually all big cities have multiple choices for LTE and most have at least one choice for LTE Advanced—the real 4G wireless. For example, you can see iPhone and Android users taking advantage of all this high-capacity coverage as they leisurely view high-definition YouTube videos without buffering and actually livestream major league sports in cafes, parks and just walking around at lunch.

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3 Types of Microwave Propagation and the Horn Antenna

Antennas on the roof of a microwave relay stat...

Horn antennas on the roof of a microwave relay station near Madison St. and 17th Ave, Capitol Hill, Seattle, Washington state, USA. (Photo credit: Vladimir Menkov via Wikipedia)

Between any two microwave radio antennas, there is one direct ray and multiple refractive/ reflective multi-path rays. In the eighth and last installment of our Radio Head Technology Series, Aviat Networks Principal Engineer and master storyteller, Dick Laine, relates how restrictive tower rules for San Francisco’s historic China Basin Building required fine adjustments of a horn antenna to resolve reflective rays from the surrounding bay.

As Dick tells it, to accommodate a Space Diversity arrangement, one horn antenna on the building had to be hung upside down. During the installation process, the alignment for the upside-down diversity antenna created a reflection point 3 miles out into the bay. The performance was horrible, but at the time, no one knew why. So when a little speedboat or anything larger went through the reflection point, there would be an outage as the signal was interrupted. There did not seem to be an obvious fix to the alignment issue. The horn antenna did not have a way to check the alignment on the horizontal with a bubble level.

To find out how Dick solved this antenna mystery, register for the Radio Head series (it’s free). Then to put it all in context, Dick goes over Huygens’ Principle as it applies to microwave signal diffraction. And if you ever wondered what happened to periscope antennas, Dick provides some key insight! Tune in to find out!

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All-Indoor Microwave: LTE’s Best Backhaul Solution for North American Operators

Eclipse Packet Node IRU600 all-indoor microwave radio

Aviat Networks’ Packet Node IRU600 is an example of an all-indoor microwave radio, which is one choice wireless operators should consider for implementations in North America.

There’s a lot of buzz in the microwave industry about the trend toward all-outdoor radios, but those who haven’t been through LTE deployments may be surprised to learn that based on our experience deploying LTE backhaul for some of the world’s largest LTE networks, all-indoor is actually the best radio architecture for LTE backhaul.

We can debate today’s LTE backhaul capacity requirements, but one thing we do know is that with new advances in LTE technology, the capacity needed is going to grow. This means that microwave radios installed for backhaul will likely have to be upgraded with more capacity over time. Although people are experimenting with compression techniques and very high QAM modulations and other capacity extension solutions, the most proven way to expand capacity is to add radio channels because it represents real usable bandwidth independent of packet sizes, traffic mix and the RF propagation environment.

All-indoor radios are more expensive initially in terms of capital expenditures, but they’re cheaper to expand and (as electronics are accessible without tower climb) are more easily serviced. While an outdoor radio connects to the antenna with Ethernet or coax cable, indoor radios usually need a more expensive waveguide to carry the RF signal from the radio to the antenna. So you pay more up front with an all-indoor radio but as the radio’s capacity grows you save money. There are several reasons.

When everything related to the radio is indoors, you just have a waveguide and an antenna up on the tower. To add radio channels with an all-indoor radio you go into the cabinet and add an RF unit. With an outdoor radio, you have to climb the tower, which can cost as much as $10,000. Also, when you add a new outdoor RF unit you may have to swap out the antenna for a larger one due to extra losses incurred by having to combine radio channels on tower….(read the full story at RCR Wireless).

Gary Croke
Senior Product Marketing Manager
Aviat Networks

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FCC Rule Changes Lower the Cost of Microwave Deployments

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Last Friday, 03 August 2012 saw the release of FCC Report and Order 12-87, which contained some significant changes that will lower the total cost of ownership for many microwave links. The two most significant changes concern antenna sizes and wider bandwidths.

Following lobbying by Comsearch and the Fixed Wireless Communications Coalition (FWCC), within which Aviat Networks plays an important role, the FCC has allowed an additional alternative set of antenna parameters to be used in the 6, 18 and 23GHz bands. These new parameters are an alternative to the existing antenna parameters, which have been retained. It is worth noting that while the FCC does not specify actual antenna sizes, the realization of antennas based upon these new parameters does represent a reduction in size and thus provides for the reduced cost of both CAPEX and OPEX that has already been championed by Aviat Networks and other interested parties. The new working alternative antenna parameters are as follows:

  • 3 feet for the 6GHz band
  • 1 foot for the 18GHz band
  • 8 inches for the 23GHz band

To put these changes into perspective the typical cost of renting space for an antenna on a tower is US$400 + US$100 per foot (diameter) per month. So a link consisting of two 6ft antennas will cost 2x (400 + 6×100) = $2000 per month, i.e. $24,000 per annum.

If the antenna diameter could be reduced to 3 feet the cost is reduced to 2x (400 + 3×100) = $1400 per month, i.e. $16800 per annum—a saving of $7200 per year on a single link!

The above calculations are not only ours but also those of MetroPCS, which is quoted in the report and order. MetroPCS specifically notes, as an example, that “the cost of a microwave dish antenna is approximately $100 per foot per month. Thus, even if the revised rule allows for a reduction of just one foot, the annual savings would be $1,200, and the savings over a ten year period would be $12,000.”

Smaller antennas also open up more options in terms of locations for these antennas, and their smaller size reduces wind loading and the need for specialist mountings and strong towers.

Additionally, the FCC in a further notice of proposed rule making attached to this report and order seeks feedback on allowing similar alternative antenna parameters in the 11 and 13GHz bands. Aviat Networks intends to support this proposal via the FWCC.

Other Changes

With the ever-growing demand for bandwidth the FCC has decided to allow aggregation of two 30MHz channels in the 6GHz band and two 40MHz channels in the 11GHz band, giving maximum bandwidths of 60MHz and 80MHz, effectively allowing a doubling of the capacity of a microwave link. This represents another significant cost saving because this increased capacity can be achieved with the same amount of hardware.

Also in this report and order were changes to the definition of efficiency standards to a bits/sec/Hz standard as proposed by the FWCC, and a clarification of the definition of payload capacity: “The bit rate available for transmission of data over a radiocommunication system, excluding overhead data generated by the system.” The FCC has also introduced a welcome simplification of the rules with regard to bit rate efficiency. FCC Part 101.141 has been amended to include a table (below) that details the efficiency criteria according to two frequency ranges and three bandwidth ranges:FCC new bits/sec/Hz efficiency standard

Aviat Networks welcomes the FCC’s progressive changes as the amendments will stimulate the microwave industry and enhance the cost effectiveness of microwave networks across the United States. We expect the rule changes to be effective approximately in October.

Ian Marshall
Regulatory Manager
Aviat Networks

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FCC: New Spectrum for Wireless Backhaul, Relaxed ACM Rules

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Image via Wikipedia

On 9 August 2011, the FCC announced several changes to the rules (Part 101) that govern the use of microwave communications in the Fixed Service bands in the U.S. These changes are great news for operators and will be encouraging increased adoption of microwave technology as a wireless transmission alternative to fiber for next generation mobile networks and fixed/private networks.

New Frequency Band for Fixed Services

The FCC opened 650 MHz of new spectrum for Fixed Service (FS) operators in the 6875-7125 MHz and 12700-13100 MHz bands, which will be shared with the incumbent Fixed and Mobile Broadcast Auxiliary Service (BAS) and Cable TV Relay Service (CARS). These bands will primarily be used as an alternative to the 6 and 11 GHz “Common Carrier” bands in rural areas, where the band is not currently licensed to TV mobile pickup stations used in newsgathering operations.

Frequency allocations in these new bands should commence later this year and will be based upon the existing 25MHz channelization. To facilitate adoption, the FCC is also allowing the use of 5, 8.33 and 12.5 MHz channels, as well as 50 MHz channel operation in the 12700-13100 MHz band using two adjacent 25MHz channels.

Allowing Adaptive Modulation

Adaptive Modulation, or AM—or ACM when used with Adaptive Coding—is a relatively recent innovation in microwave technology that allows the radio to dynamically adapt to path conditions to allow a much higher degree of spectrum efficiency, increased wireless link throughput, use of smaller antennas or a combination of all three benefits.

Up until now, the use of AM was restricted by the requirement to comply with FCC spectrum efficiency rules, which dictate a minimum data rate for certain bands. For example in the 6 GHz band a minimum capacity of 130 Mbit/s, or 3xDS3, must be maintained at all times within a 30 MHz channel assignment, using 64QAM modulation. The FCC now allows AM operation where the capacity of the link may drop below the minimum data rate, as long as the operators “design their paths to be available at modulations compliant with the minimum payload capacity at least 99.95 percent of the time,” or in other words, operators will have to “design their paths to operate in full compliance with the capacity and loading requirements for all but 4.38 hours out of the year.”

Aviat Networks, through our membership of the Fixed Wireless Communications Coalition (FWCC), supported rule changes to permit ACM, and the FCC included in its Rulemaking (Clause 48) our analysis on the benefits of ACM in terms of reducing the costs associated with tower leasing:

By way of hypothetical, consider a single link in the 6 GHz band that would require 10-foot antennas with a 99.999 percent standard instead of 6-foot antennas under the 99.95 percent standard. The total cost increase over a 10-year period in this hypothetical example could exceed $100,000.

The smaller antennas offer a number of advantages over larger ones, including more TCO savings over those 10 years.

Still Under Consideration by the FCC

Of all the new proposals being considered, the FCC also announced a Further Notice of Proposed Rulemaking (FNPRM) to further investigate the following proposals:

  • Allowing Smaller Antennas in Certain Part 101 Antenna Standards without materially increasing interference
  • Exempting Licensees in Non-Congested Areas from Efficiency Standards to allow operators to increase link length in rural areas
  • Allowing Wider Channels, including 60 MHz in the 6 GHz band, and 80 MHz in the 11 GHz bands
  • Revising Waiver Standard for Microwave Stations Near the Geostationary Arc to align with ITU regulations
  • Updating Definition of Payload Capacity rules in Part 101 rules to account for Internet Protocol radio systems

Aviat Networks continues to work on these issues, via the FWCC, which we believe will assist operators in lowering their total wireless network operational costs by taking advantage of the newest innovations that are now available in microwave technology.

With these new rules, along with the potential for further changes under consideration, microwave solutions provide an even more compelling case to enable mobile operators in the U.S. to keep pace with the IP mobile backhaul capacity demand driven by the introduction of new 4G wireless/LTE wireless networks.

Ian Marshall
Regulatory Manager, Aviat Networks

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