• April 13, 2012

Coverage Maps for New Wireless Spectrum Available to Fixed Services

United States radio spectrum frequency allocat...

United States radio spectrum frequency allocations chart. The FCC has freed 650 MHz of spectrum to increase sharing possibilities for 7GHz and 13GHz bands. (Photo credit: United States Department of Commerce employee via Wikipedia)

As we blogged last summer, the FCC has released 650 MHz of new wireless technology spectrum for Fixed Service wireless communication technology operators. Now Comsearch, a leading provider of spectrum management and wireless engineering services in the US, has highlighted this issue in its latest online newsletter, with an article that includes some very informative coverage maps showing the zones where the new bandwidth is available.

These maps are excellent at conveying the limitations of the newly released spectrum for microwave link applications in the 7 GHz (6.875–7.125) and 13 GHz (12.7–13.1) bands. After taking into account the zones that are reserved for existing Fixed and Mobile Broadcast Auxiliary Service (BAS) and the Cable TV Relay Service (CARS) users, these new bands are only available in about 50 percent of the US land mass covering only 10 percent of the population.

What do you think? Should the FCC loosen the spectrum sharing rules even more for 7GHz and 13GHz bands? Take our poll and tell us:

  • April 6, 2012

Wireless Network Services: Disaster Monitoring and Recovery

Category F5 tornado (upgraded from initial est...

Category F5 tornado (upgraded from initial estimate of F4) viewed from the southeast as it approached Elie, Manitoba, on Friday, June 22, 2007. (Photo credit: Justin1569 at Wikipedia)

In 2011, the United States experienced its worst tornado outbreak in more than 50 years. And communication systems were not spared from the carnage.

In the video below, Robert Young, senior manager for Aviat Networks’ Americas TAC/NOC explains how the company’s San Antonio network operations center (NOC) and its expertise in disaster monitoring and recovery helped microwave communication systems rebound from severe weather challenges. He details how the Aviat Networks Technical Assistance Center (TAC) and NOC team provided support for customers during the 2011 tornado outbreak.

One of the special services Aviat Networks’ NOC offers is in the form of Special Event Recovery and Monitoring. Two of Aviat Networks’ major customers were directly affected by the 2011 tornado outbreak. The storms were tracked, and the customers were preemptively notified of the storm tracks. Approximately 600-plus tornadoes were monitored in one week, and Aviat Networks managed disaster recovery of more than 300 outages due to the storms.

  • March 23, 2012

10 Things to Know About the Status of Asymmetrical Wireless Backhaul

Paging through the radio spectrum

The ECC held a meeting in March to further consider updating regulations to allow the use of asymmetrical links in microwave backhaul (Photo credit: blese via flickr)

Last autumn we wrote about potential plans from a microwave competitor regarding using asymmetric band plans for point to point microwave communication links. To update this topic, we have put 10 things in parentheses that you should know about the current status of asymmetrical links in wireless backhaul. Last month at an Electronic Communications Committee  SE19 (Spectrum Engineering) meeting this microwave technology subject was discussed again. (1) The proposal under consideration has been reduced in scope and (2) the regulators present still wish to see more evidence regarding the need for change before agreeing to such significant amendments.

Asymmetric Band Plan Altered
A quick reminder of what was originally requested back in the autumn of 2011; a move from channel sizes of 7, 14, 28 and 56MHz to channel sizes of 7, 14, 21, 28, 35, 42, 49 and 56MHz in order to support different granularities of channel widths in all bands from L6GHz to 42GHz. However in March these proposals were altered to reflect channel sizes of 7, 14, 28 and 56MHz (i.e., no change to existing channel sizes) and asymmetric only in the 18GHz band and above.

The national regulatory authorities stated that even the (3) revised proposal cannot be accommodated with existing planning tools so they cannot imagine asymmetric links being deployed alongside existing links in their countries. A few stated that in block allocated spectrum the owner of the spectrum may be able to implement this channelization, but Aviat Networks believes that (4) the complexity of coordinating links even in block allocated spectrum should not be underestimated.

Saving Spectrum?
Traditionally, links are planned on an equal bandwidth basis, e.g., 28MHz + 28MHz, with a constant T/R spacing throughout the band in question. This new proposal would see links of 28MHz + 7MHz and furthermore makes the claim that spectrum would be saved. Numerically speaking this arrangement would save 21MHz for each pair, but (5) saved spectrum is only of value if it is reused. In many cases the “saved” spectrum would be orphaned due to difficulties coordinating it into usable pairs.

Asymmetric Channel Plan Limits Future
In our last blog on this topic we reflected on the fact that while there is some level of asymmetry today, (6) this trend may well be balanced in the near future by cloud services and other services that involve the user uploading content. We believe that (7) committing to an asymmetric channel plan now limits the future. (8) Symmetric channel planning allows networks to dynamically adjust to changing demands. A related concern is the fact that (9) spectrum once reallocated may not be easily clawed back to create symmetric pairs in the future. While some applications are experiencing asymmetry in traffic presently, we should not forget that some traffic patterns are still symmetric and where asymmetry is a feature, (10) the scale of this phenomenon may be overstated. Indeed, a major European operator present at the SE19 meeting voiced skepticism about the need for asymmetric support.

What do you think? Will mobile traffic remain or increasingly become asymmetric? Are asymmetric microwave links needed or can they be practically deployed in existing bands? Answer our poll below and tell us. Select all answers that apply.

Ian Marshall
Regulatory Manager
Aviat Networks

  • March 15, 2012

Diverse Wireless Network Topologies Cost Savings

To compare how different wireless backhaul network topologies perform under the same operating scenario, let’s analyze how a traditional hub-and-spoke and a ring configuration compare in connecting the same six sites (See table below). For the hub-and-spoke configuration, each cell site is provided 50 Mbps capacity in 1+1 protection. With five links and no path diversity, full protection is the only way to achieve five nines reliability. In this configuration, 10 antennas are employed, which average a large and costly 5.2 feet in diameter. Total cost of ownership for this six-site network is close to $700,000 for five years.

TCO Comparison by Topology

For a ring design for the same six sites, throughput of 200 Mbps is established to carry the traffic for each specific hop and any traffic coming in that direction from farther up the network. Designed to take advantage of higher-level redundancy schemes, the ring configuration only requires antennas that average 2.3 feet in diameter, which are much lower in cost compared to the antennas in the hub-and-spoke configuration. And even though the ring configuration requires 12 antennas and six links, its overall TCO amounts to a little under $500,000 over five years—30 percent less than TCO for the hub-and-spoke design for the same six sites.

This comparison is based upon deployments in the USA, where most operators lease tower space from other providers.

Gary Croke
Senior Product Marketing Manager
Aviat Networks

 

Related articles

  • December 21, 2011

Not Your Usual Microwave Installation

Have you ever had an unusual experience at a microwave radio site?

Here’s one we would like to share with you. Aviat Networks Account Manager Mark Davis recently experienced an ascent of Mt. Pisgah in North Carolina (mid-Atlantic coast USA) in a cable car—climbing 3,600 feet in 11 minutes. The cable car is purpose-built to carry engineers to the TV broadcast tower on top of Mt. Pisgah, in this intance it transported 6-ft antennas and Aviat Networks radio gear. The microwave radio installation will connect U.S. National Park Service offices along the entire Blue Ridge Parkway.

Check out the video:


We are sure there are many more interesting examples of radio installations out there. Post comments below or email us your story or images. We want to hear from you!

  • September 22, 2011

Time for an update on Timing Solutions

Time for an update on Timing Solutions

A network without synchronization is like an orchestra without a conductor.

Our partner, Symmetricom, recently announced the launching of a new segment of their SyncWorld ecosystem for microwave backhaul.  Our hat’s off to them; this is great news for Symmetricom and the new players that are now on board. We boarded this train awhile back.  After a couple years of collaborative testing between us, we first joined the ecosystem when it was initially launched in March at CTIA 2011.  

So, what have we learned since then you might ask?

Well for one, packet based timing is still growing in interest, evaluation, and deployment.  Customers around the world — including mobile operators, state and utility providers and others – are increasingly looking for timing solutions that operate over their Ethernet fiber and microwave network as effectively as their TDM timing solutions do.  A recent Heavy Reading analyst report projects close to 2 million cell sites will have deployed the two most dominant solutions, IEEE 1588v2 and Synchronous Ethernet (SyncE), by 2015.

Secondly, we’ve learned this is by no means the technology race it started out to be.   Remember when Blu-ray and HD–DVD were competing a few years ago?  Or perhaps that has well faded into memory.  Well, I still recall the industry buzz a couple years ago about whether Synchronous Ethernet (SyncE) was going to kill IEEE 1588v2, or vice-versa. Who was going to come out on top?  

Telecom watchers and players are always primed for a tech battle it seems.  Well lo and behold; this battle has become more of an alliance, as of late.  

The dominant discussion today is now about how BOTH these technologies can co-exist, and where best to deploy them in a network, either side by side or in parallel, with one backing up the other.  Hmmm, now that’s an interesting conclusion to a tech battle. 

Case in point, a couple of our customers are planning to deploy both technologies to take advantage of their respective strengths and are in the process of doing just this.  See this whitepaper for more information about synchronization over microwave backhaul or maybe this one for insight into deploying IEEE1588v2 synchronization.

So, with the reality today that packet timing is still growing and that options for packet timing (including TDM, 1588v2, SyncE, and GPS) will continue to co-exist for a long time, it becomes even more critical to seek experience when it comes to planning your sync migration. 

An ecosystem is probably a good place to start, especially with those players that have been at it for some time.

Errol Binda,
Sr. Manager, Solutions Marketing

  • August 23, 2011

4 Realities about Rain Fading in Microwave Networks

Rain fading (also referred to as rain attenuation) at the higher microwave frequencies (“millimeter wave” bands)  has been under study for more than 60 years. Much is known about the qualitative aspects, but the problems faced by microwave transmission engineers—who must make quantitative estimates of the probability distribution of the rainfall attenuation for a given frequency band as a function of path length and geographic area—remains a most interesting challenge, albeit now greatly assisted by computer rain models.

A surprising piece of the puzzle is that the total annual rainfall in an area has almost no correlation to the rain attenuation for that area. A day with one inch of rainfall may have a path outage due to a short period of extremely high localized rain cell intensity, while another day of rain may experience little or no path attenuation because rain is spread over a long period of time, or the high intensity rain cell could miss the microwave hop completely.

Over the years, we have learned a lot about deploying millimeter wave microwave hops for our customers:

  • Rain outage approximately doubles in each higher millimeter wave band, e.g. 18 to 23 GHz
  • Rain outage is directly proportional to path length—assuming a constant fade margin for each hop
  • Rain outage in tandem-connected short hops is the same as for a single long hop—if they have the same fade margin
  • Multipath fading in optimally aligned millimeter wave hops does not occur during periods of heavy rainfall, so the entire path fade margin is available to combat rain attenuation fades

More information about assessing rain-induced attenuation is available in our white paper, Rain Fading in Microwave Networks.

  • The influence of rain attenuation (sce.carleton.ca)
  • The World’s Longest All-IP Microwave Link (aviatnetworks.com)
  • Comparison of Multiple Rain Attenuation Models with Three Years of Ka Band Propagation Data Concurrently Taken at Eight Different Locations (spacejournal.ohio.edu)
  • Microwave Wireless Backhaul Case Study: Tooele County (Utah) (aviatnetworks.com)
  • Proposed Rain Attenuation Model Revised From ITU Used For Prediction in Tropical Climates (aprsaf.org)
  • August 5, 2011

Fiber Isn’t Everything: Key Role of Microwave in Mobile Backhaul

Fiber

If fiber is this much of a mess in your wiring closet, just imagine the difficulty of deploying it to your cell site. Image by DrBacchus (Rich Bowen) via Flickr

Last year in August, Aviat Networks presented its argument for why fiber optics technology isn’t everything where backhaul of wireless networks is concerned. If anything, this point has only been reinforced by analyses and anecdotal stories showing that fiber can be overkill for the mobile backhaul requirements of  LTE wireless. Plus, there is the simple truth that fiber cannot be deployed to every cell site due to financial and topological issues. That’s why microwave technology remains the world’s first choice for backhauling wireless networks. So let’s look at last year’s FierceWireless webinar slide presentation and refresh our memories.

These slides present the findings of an Ovum survey of North America’s largest backhaul players to understand their strategies regarding media types used to supply cell-site backhaul.

Ovum found that demand for wireless backhaul equipment in North America will continue to grow as mobile operators upgrade their networks to support higher-speed LTE networking technologies. The most common backhaul strategy for mobile operators in the region comprises leasing services over fiber combined with owning and operating microwave-based facilities. Microwave has a distinct advantage vis-a-vis leased services over the long-term due to the opex associated with leasing.

If you would like to see more, you may register for the on-demand replay of the full webinar. It will also present the latest trends and advancements in microwave transmission technology that support the evolution of mobile backhaul networks to all-IP.

  • Telecom PR: Looking for the “Back Story” in Today’s Wireless Boom (customerthink.com)
  • Backhaul for the Mobile Broadband or Wireless Broadband Network (aviatnetworks.com)
  • Pictures From LTE World Summit (for 4G Wireless) (aviatnetworks.com)
  • Ethernet OAM Meets Demands on Microwave (Wireless) Networks (aviatnetworks.com)
  • Small Cell Mobile Backhaul: The LTE Capacity Shortfall (aviatnetworks.com)
  • July 22, 2011

Evolution of Microwave: History of Wireless Communications

The Microwave Sky

This image of microwave energy in a "total sky" picture of the known universe shows it's everywhere in primordial space, more than 13 billion years ago.

Microwaves are as old as the beginning of the universe. Well, they’ve been around for at least 13.7 billion years—very close to the total time since the Big Bang, some 14 billion years ago. However, we don’t want to go that far back in covering the history of microwave communications.

Having just observed the 155th anniversary of the birth of Nikola Tesla, arguably the most important inventor involved in radio and wireless communications, this is a good time to take a broader view of the wireless industry. If you have been in the wireless transmission field for some time, you are probably familiar with Dick Laine, Aviat Networks‘ principal engineer. He has taught a wireless transmission course for many years—for Aviat Networks and its predecessor companies.

The embedded presentation below comes from one of those courses. In a technological field filled with such well-educated scientists and engineers from some of the finest universities and colleges, it’s hard to believe that microwave solutions and radio itself started in so much controversy by men who were in many cases self-taught. Dick’s presentation goes over all of this in a bit more detail. Hopefully, it’s enough to whet your appetite to find out more. If you like the presentation, consider hearing it live or another lecture series on wireless transmission engineering at one of our open enrollment training courses.

  • NASA’s ‘Age of Aquarius’ Dawns With California Launch (spacefellowship.com)
  • Solar Power from the Moon (empressoftheglobaluniverse.wordpress.com)
  • Ireland Issues Spectrum Consultation on Wireless Communications (aviatnetworks.com)
  • Backhaul for the Mobile Broadband or Wireless Broadband Network (aviatnetworks.com)
  • Homage to Nikola Tesla, Great Inventor of Wireless Technology (aviatnetworks.com)
  • May 4, 2011

The World’s Longest All-IP Microwave Link

Successfully Implementing a 193-km Microwave Link over Water to Deliver 99.9995 Percent Availability

Introduction

For most designers of microwave transmission paths, engineering a reliable link over water can be a daunting task. Reflections off the water surface can play havoc with the received signal, leading to high levels of interference resulting in fading and ultimately a high level of errors and signal interruptions. For these types of paths, performance calculations using commercially available software planning tools will be insufficient to ensure superior path performance. In these cases, experience and understanding of the key parameters that influence microwave performance are critical.

Recently, Aviat Networks and our agent, Telecomunicaciones y Sistemas S.A. (TELSSA), deployed an Eclipse microwave link for Central American Corporation for Air Navigation Services (COCESNA) in Honduras that crosses over 193 km, most of which is over water. With careful design and installation, this link is now operating successfully.

COCESNA is responsible for the air traffic control over Central America territory and oceanic areas, therefore, availability of service is a critical issue.

Subscribe to our newsletter