‘My Experience’ with Microwave Radio Systems

Like-a-star-in-a-distant-galaxy-each-users-experience-with-Aviat-Networks-microwave-radio-is-unique-and-positive-13Dec13

Quasar GB 1428, 12.4 billion light years from Earth, a celestial source of enormous X-ray and microwave energy. Photo: NASA’s Marshall Space Flight Center / Foter.com / CC BY-NC

Collectively, we as consumers of high-tech communications systems tend to think very analytically, very logically, about the solutions that form the core of our working lives. In all the fields that we pursue from mobile telecom to public safety to utilities to oil and gas to financial, microwave radio has touched, shaped and framed our worldview. But like a star in a distant galaxy, every user’s experience with microwave radio is unique. No exception to that totality of reality is Ron Beck, president emeritus and past chairman of the Utilities Telecom Council, a trade group dedicated to advocating telecommunications issues for energy companies and associated concerns.

In a recent video, Beck talks about his life with microwave radio for almost 30 years. Starting with analog TDM microwave radio, he has traveled the technology evolutionary path to arrive at the present day systems of digital IP/Ethernet microwave communications. However, before ever touching on any technical considerations, he talks about the people responsible for his and his company’s success with microwave. For utilities applications, Beck feels it is critical that the people he deals with at a microwave solutions provider understand his business. “The (Aviat) sales force understands utility applications; they understand what we need in a radio system,” he says.

Beck goes on to elaborate how Aviat design and engineering groups collaborate closely with his team to deliver exactly the solution that is needed. Service and standards-based technology are very important to him and make microwave radio very user-friendly because “frankly, you don’t have to touch it very much.” See and hear all Beck has to offer below:

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All-Outdoor Radios Part II: Three Ways to Choose the Right ODR

Photo credit: mrbill / Foter.com / CC BY

Photo credit: mrbill / Foter.com / CC BY

A quick Google-glance around the Internet will reveal a panoply of all-outdoor radios (ODRs) in both microwave and millimeter-wave bands. ODRs do not conform to a universal norm in terms of networking features, power consumption, bandwidth scalability (i.e., capacity) or outright radio horsepower (i.e., system gain).

So if you find yourself asking the questions, “Which ODR is the best fit for my network?” or “How do I narrow the ODR field?” it is good to start with the basics.

The right product choice can be quickly resolved—or at least the candidates can be short-listed—by focusing on three ODR product attributes that most heavily influence the value-for-the-money (i.e., total cost of ownership or TCO) equation:

  • Packet throughput capacity, which dictates the usable life of the ODR
  • Power consumption, which affects the energy bill
  • RF performance, which impacts antenna size—more system gain equates to smaller antennas

For many microwave backhaul networks, the growth in underlying traffic is such that products which cannot scale to 500 Mbps/1 Gbps per channel will run out of momentum too early and precipitate the dreaded “forklift upgrade” (also known as the “CFO’s nightmare”).

These same CFOs are also suffering sleepless nights due to rising energy costs—which in some countries can double year-over-year. Therefore, it behooves the operator to seek and prioritize the use of über energy-efficient products, such as the Aviat WTM 3200, which—and this is important—do not compromise on RF performance.

That brings me to my last point: System gain (RF performance) remains a core TCO factor insofar as it can drive smaller antenna usage with the concomitant capex savings. Still, there might be little to differentiate ODRs in terms of RF performance—in which case the spotlight will fall on these other attributes to sway the decision.

Having worked on the operator side and wrestled with TCO analysis on many occasions, my experience tells me that you can narrow your ODR choice quickly by reflecting on these three attributes and the TCO gains they can deliver.

Jarlath Lally
Product Marketing Manager
Aviat Networks

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All-Outdoor Microwave Radios: Site Considerations

One of the great things about the microwave radio market today is the diversity of products available to network operators. But like many situations where there is a glut of options, it tends to put more stress on making the right choice.

An operator looking at products in the microwave radio sector will notice that there are three general categories of product to choose from: all-indoor, split-mount and all-outdoor, and within each, they are myriad different flavors.

All-outdoor radios are the most recent addition to the microwave radio party, and for the sake of easy reference, I’ll refer to them as ODRs (outdoor radios). These self-contained systems incorporate the traffic interfaces, switching/multiplexing elements, radio modem and radio transceiver—all packaged in a weatherproof outdoor housing. By contrast, an outdoor unit (ODU) used in split-mount systems only contains the radio transceiver, which connects to a radio modem embedded in an indoor unit (IDU). In a split-mount radio system, the IDU also provides the traffic interfaces and switching/multiplexing elements.

The rationale for ODRs is straightforward—networks are getting denser, new sites are getting smaller and established sites more densely populated. Space for equipment such as IDUs is at a premium and costs of upgrading sites with bigger equipment shelters is often not viable or possible due to site constraints. As a result, more network devices are being repackaged for deployment outdoors on supporting structures such as towers, walls or masts. Advances in electronics have made microwave radios viable for all-outdoor treatment, so ODRs came into being.

They did so to a fanfare of claims that pointed to fantastic gains in terms of operator TCO (total cost of ownership). No doubt, an ODR can deliver cost benefits, but it is important to fully scope and quantify those benefits, because although ODRs represent simplification in terms of product architecture, most networks have remained stubbornly complex. In practical terms, this means for each type of site in the network an operator needs to closely examine the gains an ODR might generate vs. a split-mount radio, for example. Our experience is that ODRs provide the most operator benefits at sites where:

  • One gigabit Ethernet (GbE) interface is adequate
  • Only a single local device will be connected (such as an LTE basestation)
  • There are no requirements to aggregate traffic from “downstream” sites
  • Out-of-band management facilities are not required
  • Non-protected (1+0) link configuration is adequate

Once operators consider sites with requirements beyond this scope—usually the majority—then ODRs (somewhat ironically) start to generate complexity and cost. This becomes manifest in the form of multiple Ethernet cable runs, multiple power cable runs, multiple PoE injectors, multiple lightning protection devices and, in some cases, the need for a separate outdoor Ethernet switch.

Even at modestly complex sites, the overhead costs ODRs can generate mean that a split-mount radio will often be a more effective option and deliver better TCO, assuming space can be found. On that note it is worth highlighting that IDUs already deployed at such sites are often modular and can be scaled without consuming any additional rack space, and the most advanced fixed (i.e., non-modular) IDUs only consume a half-rack unit of space.

On the surface, the case for ODRs can seem compelling but before jumping in, I would encourage operators to carefully examine how marketing claims translate into meaningful (real) TCO gains.

I am convinced ODRs represent a new and potentially very useful product category for microwave radio, but they are not a panacea; our experience (at Aviat Networks) is that optimum TCO is based on a mix of split-mount and all-outdoor radios (i.e., one “size” does not fit all).

So there you have it, in the right environment, an ODR can offer a winning formula but in other situations, it may not work so well. An old saying comes to mind: Knowledge is knowing a tomato is a fruit, but wisdom is knowing not to put a tomato in a fruit salad.

Next time, we will examine ODRs in more detail, how they differ and how to choose the best option for your network.

Jarlath Lally
Product Marketing Manager
Aviat Networks

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Evolution of Trunking Microwave Radios

Aviat WTM 6000 trunking microwave radio

Aviat WTM 6000 trunking microwave radio

Back in the day, trunking microwave radios were huge power-hungry beasts that consumed vast quantities of power and space at equal rates. They were complex “animals” that took days to install and hours to configure. Then they had to be looked after like well-loved but aged members of the family—with care, all due respect and consideration. Over time, components went out of adjustment and had to be brought back into line through various tuning routines, but overall they did their job as the super-reliable backbone of the POTS (i.e., Plain Old Telephone Service).

Jump forward a few decades and the latest trunking microwave solutions are elegant and graceful—almost svelte. With their current high levels of electronic integration, a complete repeater system can stand in a single rack space—unheard of until the most recent products. Furthermore, these new systems consume dramatically less power—a typical 3+1 system (i.e., four transceivers) consumes less than 400 watts. So now, backbone operators can save significantly on operating expenditure because of decreased space and power requirements at their microwave radio shelters.

Evolving microwave systems from analog to digital microwave systems carrying digital payloads was a rocky and dangerous path. The next migration from TDM payloads to IP payloads appears to be just as treacherous. How can a traditional TDM backbone radio, typically configured with N+1 radio protection switching, be reconfigured to transport a non-TDM payload that does not suit N+1 switching? IP transport is a completely different environment altogether! Luckily, trunking radio system designers have not ignored the Internet revolution and are perfectly aware of these challenges. In fact, well-appointed trunking microwave radio systems allow a graceful evolution from TDM to IP, with capability to transport both types of traffic simultaneously—and with their own ultra-reliable protection schemes!

Today, trunking microwave radios can support both TDM and IP seamlessly, offer robust radio performance and highly reliable switching and really do make it easy for operators to design mission-critical backbone networks. They offer mean time between failure (MTBF) reliability figures into the hundreds-of-years and highly integrated yet modular designs, which make expansion very straightforward. Before deciding on a trunking microwave radio, consider if the system:

  • Allows easy migration from TDM to IP with a minimal amount of replacement materials
  • Can expand to an expected maximum channel capacity (for example, six channels) without needing additional racks, etc.
  • Enables repeater configurations within one rack
  • Has a field-proven heritage of reliability and performance

Terry Ross
Senior Product Manager
Aviat Networks

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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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Diversity, Hot Standby and Alarms for Wireless Backhaul—Oh My!

Microwave radio relay tower on Cimetta mountai...

(Photo credit: LittleJoe via Wikipedia)

Do not be Alarmed by this latest video in the Radio Head Technology Series (complimentary registration). For the insider’s perspective on Hot Standby, we will not keep you waiting. Dick Laine, Aviat Networks’ principal engineer, has many informed views on Diversity and relates them in his familiar relaxed presentation style.

All puns aside, Dick covers the multitude of options available in Diversity Schemes (and all their acronyms!). Plus, there is a lot to know about the differences in asymmetrical splitters for digital radios and their analog predecessors. Turns out there is no point in using symmetrical splitters in digital microwave radios. Even a heavily asymmetrical split provides as much protection as a symmetrical split but it avoids 2-3 dB in fade margin losses, providing significantly more uptime.

And if there is anything you need to know about Alarms, Dick takes a fine-toothed comb to the subject and teases out the details, providing context for the strategy of how they function in keeping your wireless communication network online. Dick will also tell you how improvement in digital radios has led to large gains in recovery time when radios in a Hot Standby arrangement are switched and quadrature relock can now essentially be avoided. On errorless switching, although it has greatly benefitted microwave radio usage, Dick will tell you the importance of early warning alarms to it.

So make no mistake, Dick is your information source for all things microwave radio—wrap your head around it!

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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

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How Many Radio Options Are You Juggling?

Juggling Radio OptionsBalancing cost and performance is a tough act for most operators dealing with telecom networking, especially when it comes to equipment procurement.  Getting all the bells and whistles can sometimes result in having a lot of options to choose from.   Often times microwave users have to juggle with a variety of radio options that suit a particular site requirement, for example, having to select between low power or high power radios to meet varying distance or system throughput/gain needs.  Depending on location and licensing requirements, this may even translate into different products types for different frequency bands.  More products result in more spares to maintain in inventory, along with added support and maintenance, inevitably leading to higher costs.

To help address this challenge, Aviat recently unveiled the industry’s first universal outdoor unit (ODU) to support software- defined base and high power modes in a single ODU, with Aviat’s unique Flexible Power Mode (FPM) capability.  FPM allows operators to optimize both cost and performance, minimizing their overall total cost of ownership, by paying for the power they need only when needed.  As a result, operators can procure a single ODU for multiple locations and via a simple software licensing mechanism, remotely adjust the transmit output power to meet the needs of a particular site.  No need to spare multiple radios, nor deal with the operational burden of managing and supporting a variety of product options.

Additionally, operators can apply this flexibility to migrate from legacy low power, low capacity radios to a high power and performance ODU  to support much greater link throughput, without having to change their installed antennas. This minimizes both their CAPEX and OPEX while migrating their network from a legacy low capacity TDM microwave link to a high speed Ethernet one.

So while juggling may still be a well needed skill to survive in Telecom, Aviat is reducing the load when it comes to microwave networking. Click here to find out more.

Errol Binda
Senior Solutions Marketing Manager
Aviat Networks

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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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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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