Microwave Capacity: Examining Techniques to Improve Throughput

Microwave telecommunications tower, silhouette...

Recently we’ve kicked off the “Aviat Technology Series” – which are a series of bi-monthly live video streaming webinars for our customers and partners, giving a detailed overview of various technology topics (these are NOT sales pitches…)

Last week, Stuart Little and I gave a live streaming video webinar where we gave an in-depth analysis of all the possible technology options for getting the most out of your microwave system including what’s possible, what’s not, and a realistic look at what you can expect to achieve.  We covered the below topics:
•    Options for maximizing IP microwave capacity
•    Understanding capacity requirements: What’s real and what’s hype
•    The timing/availability of new capacity improvement technology

We reviewed techniques for increasing spectrum, improving spectrum utilization and growing effective utilization using higher layer protocol optimizations.  Technologies covered included: ling aggregation, co-channel dual polarization (CCDP), adaptive coding and modulation, 512/1024QAM, ethernet header compression, payload compression and asymmetrical RF.

We had lots of great questions and a ton of good feedback.  Please email: marketing@aviatnet.com to get the URL for the microwave capacity webinar replay.

Thanks to all who participated and see you in 2 months for the next one when we’ll talk about “Ethernet Protection and Redundancy”

Gary Croke
Product Marketing

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What is Packet Microwave?

“Packet Microwave” radio systems continue to enjoy a lot of coverage and hype within our market. But it helps to understand exactly what packet Microwave is, including its benefits and limitations, and how Packet Microwave compares to Hybrid radios. We created a white paper a while ago to address these issues, and since it is still relevant today we are highlighting it again.

The paper provides a clear definition of this technology and also answers the following questions:

  • What features should you expect from Next Generation microwave radios?
  • How does Packet Microwave it differ from Hybrid microwave transport?
  • Is Packet Microwave ‘All-IP’ or ‘IP-Only’?
  • Do hybrid systems meet the requirements of packet microwave?
  • What is the best approach for operators trying to choose a microwave solution?

 

 

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Wireless ‘Feel Good’ Factor

It has been satisfying to help a ‘go-getting’ wireless company from down-under win an award recently. Adelaide-based MIMP Connecting Solutions won the environment and energy efficiency category at the NECA (National Electrical and Communication Association) excellence awards using our Eclipse microwave radios.

MIMP won the award with a unique comms solution that links the Adelaide Zoo with the Warrawong Wildlife Sanctuary. The sanctuary is home to 100 species of birds and native mammals, most of which are nocturnal and endangered.

The Zoo’s old system ran at 256 kilobit-per-second at a very high cost until MIMP installed four environmentally friendly microwave radios. They now have a 32 Mb/s full-duplex connection between the sites with minimal ongoing costs. Now, the radios use less power than a light bulb.

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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.

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FCC: New Spectrum for Wireless Backhaul, Relaxed ACM Rules

Logo of the United States Federal Communicatio...

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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Why Bigger is not Always Better for Mobile Backhaul!

Terrestrial microwave radio system with two an...

Terrestrial microwave radio system with two antennas employing space diversity. (Image via Wikipedia: Photo credit David Jordan)

Antenna gain is directly related to the size (diameter) of the antenna, and wireless transmission engineers looking for more system gain to improve link performance on long or tough paths in frequency bands below 10 GHz may resort to using very large antennas with diameters of 12 feet (3.7 m) or more. However, bigger is not always better. In fact, large antennas should only be used under the most unusual of circumstances.

Use of large, oversized antennas was commonplace during the 1960s and 1970s, for analog FM-FDM heterodyne microwave communication high-capacity links operating in the L6 GHz band. This was for good reason. Communications paths consisting of multiple radio links required very high receive signal levels, and fade margins of up to 50 dB, on each link to meet end-to-end noise objectives. The large antennas helped cut baseband thermal noise by more than 3 dB, which is half that of smaller antennas. Many of these paths were relatively short and many of these analog wireless links employed frequency diversity, so higher fade margins were needed to reduce outage—especially in N+1 hops. This reliance on large antennas is often still prevalent in the minds of many wireless transmission engineers.

Today’s Digital Microwave Systems

In contrast to old analog systems, digital microwave operates essentially error-free (i.e., with a bit error rate of 1 in 1,013 transmitted bits), even with much smaller fade margins. Adequate path clearance, optimal selection of diversity arrangements using smaller antennas and the precise alignment of antennas are far more effective to ensure that error performance objectives for microwave communications are met.

Big Antennas = High TCO

So because big antennas are not really needed to ensure high path availability, they do directly impact the total cost of deploying and operating a microwave link, namely:

  • Wind Loading—There is more wind loading because of the larger surface area. A 12-ft antenna has 45 percent more loading (e.g., 1,400 lbs wind load in a 70mph wind) compared to a 10-ft antenna (e.g., 980 lbs wind load). This means the microwave tower needs to be stronger to be less susceptible to the sway that results in antenna misalignment. Stronger towers mean more costly new towers, or expensive upgrades to existing towers
  • Beamwidth—Beamwidth of a 12-ft dish is 25 percent narrower compared to a 10-ft antenna, which further increases the tower’s rigidity requirements and thus cost
  • Non-Diversity vs. Diversity—Large 12-ft antennas are sometimes justified by assuming that the single large dish is more cost-effective and/or has performance characteristics as good as two smaller diversity dishes. A single 12-ft dish with its 1,400-lb single-point wind load—and narrower beamwidth—puts far more stress on a structure than dual 8-ft diversity dishes with a distributed wind load of 1,260 lbs (2x630lbs) and much wider beamwidths. Smaller diversity dish arrangements also increase the wireless link’s performance by reducing multipath outage by more than 80 percent compared to a single 12-ft dish deployed in a non-diversity hop
  • Antenna Decoupling and Alignment—The smaller beamwidth of larger antennas also increases the difficultly to align accurately, and the risk of antenna decoupling due to angle-of-arrival variations during nocturnal atmospheric (k-factor) changes. Antenna decoupling, directly proportional to path length, is increased on those longer paths in difficult geoclimatic areas that attract the use of 12-ft dishes. It can be a death spiral—the longer, more difficult paths that attract the use of larger, narrower beamwidth antennas are those that are even more sensitive to the resulting geoclimatic conditions!
  • Aesthetics—Bigger isn’t better when deploying dishes on towers, buildings and—especially—mountaintop sites, due to aesthetic concerns, building/tower owners’ concerns and local planning limitations. These can often be mitigated by using smaller antennas
  • Deployment Costs—The overall deployment cost differential between a single 10-ft and 12-ft antenna can exceed $10,000 when transport, installation and ancillary hardware are taken into consideration, and this does not include the potential cost of added tower strengthening and increased monthly tower lease charges

So before you consider using large 12-ft+ antennas, think again and consider the bigger picture. You may well end up spending a lot more money for a path that may perform more poorly than it would have if smaller antennas had been used.

For more tips, we’ve also included some wireless transmission engineering guidelines for antennas and other wireless equipment.

Stuart Little
Director of Corporate Marketing, Aviat Networks

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‘The Cloud’ and What it Means for Wireless Technology

Cloud

Image via Wikipedia

The cloud is an all-encompassing thing that’s actually been around for a while (e.g. distributed computing, Network Attached Storage). Most of it exists today in the enterprise but is being pushed to the Internet and rebranded “The Cloud.” This affects three wireless networking segments: consumers (e.g., you, me, mom, dad), Internet providers (e.g., mobile operators, ILECs, CLECs) and wireless solutions vendors (e.g., Symmetricom, Aviat Networks).

For consumers, it represents the ability to store information—pictures, music, movies—virtually and access them wherever we go from devices of our choice. No longer do we have to worry about backing up smartphones, tablets or laptops. The downside is that this magic is going on in the background all while your data caps are being reached. So, watch out….

On the mobile operator side, this will represent a substantial increase in bandwidth used. In addition, bandwidth usage starts to become more symmetrical as more uplink bandwidth is utilized while uploading to the cloud. This also means more frequency consumption on the RAN-side as subscribers stay “on” more often. Operators need to figure how to get users off the air interface as quickly as possible. This calls for greater throughput and potentially much lower latency. Trickling data to end users compounds the air interface problem. For the most part, subscribers won’t realize what’s happening and data caps are more likely to be reached. This translates into either more revenue and/or dissatisfied customers. Clearly, operators must monetize transport more effectively and at the same time provide more bandwidth.

Lastly, for wireless solutions vendors this translates into increased sales of wireless equipment to ease the sharp increase in bandwidth consumption. This also translates into more intelligent and robust network designs (e.g., physical and logical meshes, fine-grained QoS controls) as subscribers rely more on network access for day-to-day activities. As for the cloud in general and the overall effect:

  • Traffic starts to become more and more symmetrical (i.e., photos and videos automatically upload and then downloaded to all individual peer devices (e.g., your iPhone video uploads to the cloud and then syncs to your laptop and iPad)
  • Lots more bandwidth will be used. Today, content drives bandwidth demand (e.g., you open a browser and connect to a website, you launch your Facebook mobile app and upload photos). Tomorrow, those activities will happen automatically and continuously
  • Over the Air (OTA) updates to the phone are now downloaded over Wi-Fi or 3G/4G networks. Seemingly, updates are the only things that have changed, but it still amounts to about 150 MB per phone per update—another bandwidth driver
  • More prevalent use of video conferencing—low latency, sustained bandwidth demand

Therefore, the amount of bandwidth consumption will rise dramatically this September when Apple releases iOS 5 and iCloud. Android has already driven much bandwidth demand, but it’s not nearly as “sexy” as what Apple is releasing for its 220 million users—or alternately total iOS devices: iPod touch, iPad, iPhone). It’s more than just bandwidth—it’s quality, reliable bandwidth where QoS and Adaptive Modulation will play significant roles—of this, I’m certain.

At a recent TNMO event they were talking about LTE-Advanced and leveraging the cloud for virtual hard drives. Imagine, no physical hard drive in your computer. Laptops are connected via 4G wireless/5G LTE wireless to a cloud-based hard drive, equating to lots and lots of bandwidth plus stringent latency requirements….

Steve Loebrich
Director of Product and Solutions Marketing, Aviat Networks

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Managing Wireless Networks with Element Management Systems

Management of Complexity

An EMS can be thought of as managing all the elements in a complex network, keeping them all in balance. Image by michael.heiss via Flickr

Managing a wireless network is essential. Radios, routers and third-party add-ons control vast amounts of valuable user data. Any wireless network downtime damages the user’s business and the operator’s long-term reputation. Thus, operators need a powerful but easy-to-use element management system (EMS) to monitor and administer all the disparate elements in their wireless communication networks.

Also, operators should be able to manage complete networks from a user-friendly interface, which must provide all the necessary information for fast network management system decision-making. And this system must be capable of complete standalone operation or being integrated into an operational support system using NorthBound Interfaces (NBIs).

Other additional functionality in the form of event management and notifications capability is also necessary in an EMS for wireless networks. An EMS should inform wireless operators about network events and device failures and let them to diagnose problems and apply network updates remotely. This reduces the time between a fault occurring and the fault being repaired. It may even allow a repair to be completed before a wireless link fails completely. For day-to-day management, operators need an EMS that can:

  • Deploy, manage and auto-discover wireless equipment—including all Aviat Networks devices, partner products and third-party devices
  • Display an entire network at once, via one of several map views
  • Provide an overview of network events
  • Deliver notifications of important network events
  • Enable analysis of network events, device events and performance data
  • Generate detailed reports on all aspects of a network
ProVision Screen Shot

The ProVision EMS solution can manage all Aviat Networks wireless solutions, partner wireless equipment and third-party devices from a user-friendly GUI.

Fortunately, such a carrier-class EMS solution does exist. Aviat Networks develops its ProVision EMS based on customer demand and continues to upgrade it as per user requests and requirements. For customers, implementing ProVision is vastly more efficient than developing an in-house EMS, saving time, resources and money. Aviat Networks EMS solutions are the most cost-effective way to manage wireless solutions. Aviat Networks works closely with customers to make sure that ProVision is user-friendly. The goal is that ProVision EMS allows operators to manage their networks proactively—rather than reactively—and with reduced network operating costs.

Look for future blog posts on must-have EMS data features and stats on operators using carrier-class EMS.

Mick Morrow
Sr. Product Marketing Manager, Aviat Networks

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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.

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Feds Update Spectrum Release to Relieve Wireless Congestion

Photo of HTC Mogul smartphone

Smartphones such as the HTC Mogul are driving the demand for more wireless spectrum to be released.

To help relieve wireless network congestion, the Obama Administration made a commitment to release up to 500 MHz of spectrum for reuse in commercial wireless solutions. In April 2011, the NTIA updated the progress toward this commitment in its first interim report. This 500 MHz of spectrumcomprising 280 MHz of underused commercial spectrum and 220 MHz of federally owned radio spectrum now administered by the NTIAwould help ease the growing shortage of spectrum as demands on the wireless network rise. This demand is primarily fueled by the explosive adoption rate of smartphones and other mobile broadband devices and the corresponding infrastructure—both access and mobile backhaul—required to support their use.

The timescales and conditions for the availability of this spectrum is in the hands of the FCC and is expected to take about five years as the first part of its 10 year plan. However, the first four blocks of spectrum have recently been identified for release by the NTIA at 1675-1710 MHz, 1755-1780 MHz, 3500-3650 MHz, 4200-4220 MHz and 4380-4400 MHz.

It is estimated that an auction of 500 MHz of spectrum could raise more than $20 billion for the U.S Treasury.

Many wireless technology industry commentators expect the lower bands to be taken up for wireless access. But the higher three bands could be allocated for mobile backhaul use to begin the process of easing congestion in the current 6GHz bands.

The microwave backhaul industry welcomes this first step. We look forward to follow through on further spectrum releasesespecially in the 4 to 8GHz range—which is suitable for high-capacity trunking backhaul.

Ian Marshall
Regulatory Manager, Aviat Networks

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