Many wireless operators, such as MTN in Ghana, need to optimize management of their networks and Aviat can help with products, services and software capabilities. Photo credit: Rachel Strohm / Foter.com / CC BY-ND

Wireless backhaul operators, both mobile phone networks and others carrying dedicated traffic, face the constant issue of maximizing the functionality of their systems.

In the emerging markets around the world, the pressure can be most intense. Wireless network reliability, availability and capacity all need to be increased. Customer expectations are on the rise, and operators must take the appropriate steps to meet and exceed them.

In working with MTN Ghana, Aviat Networks recently completed an implementation to increase network visibility (i.e., intelligence) by close to one-third. Aviat’s professional services experts designed the mobile operator’s backhaul links for high capacity and resiliency. Using ProVision, Aviat’s leading network management software, MTN Ghana can now administer its wireless backhaul efficiently and effectively with a reduced level of manpower.

To get the full details please download the case study. Or you may view it online below:

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Trevor Burchell, Aviat VP of Middle East, Africa and Europe Sales and Services.

In a recent interview, Trevor Burchell, Aviat Networks VP for Middle East, Africa and Europe sales and services, commented on the recent trend of low latency microwave networks. Though increasingly found in the telecom infrastructure of financial institutions, low latency microwave is not limited to these applications, he says. Burchell sees its applicability in uses as diverse as health care, government and utilities.

Some considerations are common to all microwave networks—low latency and all others, according to Burchell. Proper path planning and network engineering must be executed in order to have the most fully functional wireless point-to-point  backhaul possible, he says.

In general, Burchell sees microwave as the best choice where telecommunications have to be rolled out quickly and cost effectively. There are many other points to consider. The complete interview is available online in Engineering News.

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Unless you want to return to payphones, cellular technology requires cooperatively licensed microwave backhaul to function properly. Photo credit: UggBoy / Foter.com / CC BY

Competitive licensing of fixed microwave backhaul bandwidth is a bad idea. And it should not go any further. The reasons why are laid bare in a new article in IEEE Spectrum by former electrical engineer and current telecom law firm partner Mitchell Lazarus. In general, he argues against federal spectrum auctions for microwave frequencies, and in particular for fixed microwave links. Undoubtedly, readers are familiar with the large cash bounties governments around the world have netted from competitive bidding on cellular bandwidth—first 3G and now 4G. An inference can be drawn from Lazarus’ article that some governments (i.e., the United States, the United Kingdom) had in mind a similar, if perhaps smaller, revenue enhancement through competitive auctions of microwave channels.

The problem lies in the fallacious thinking that operating fixed point-to-point wireless backhaul bandwidth is comparable to that of mobile spectrum. Whereas mobile spectrum license holders can expect to mostly—if not fully—use the frequencies for which they have paid top dollar, the same has not historically been true of license holders of microwave backhaul bandwidth. In most cases, mobile license holders have a virtual monopoly for their frequencies on a national, or at least regional, basis. Their base stations send and receive cellular phone signals omnidirectionally. They expect throughput from any and all places. So they have paid a premium to make sure no competitors are on their wavelengths causing interference.

On the other hand, U.S. holders of microwave backhaul licenses have specific destinations in mind for the operation of their point-to-point wireless networks. They only need to communicate between proverbial Points A and B. And, historically, they have only sought licenses to operate in their particular bandwidth on a particular route. They had no need to occupy all of their licensed frequency everywhere. That would be a waste. They just have to make sure they have a clear signal for the transmission paths they plan to use. To do that, before licensing, they would collaborate with other microwave users in the vicinity and a frequency-coordination firm to establish an interference-free path plan. Any conceivable network issues would usually be resolved at this stage prior to seeking a license from the Federal Communications Commission. Essentially, the FCC is just a glorified scorekeeper for fixed microwave services, passively maintaining its transmitter location license database.

But starting in 1998, with dollar signs in their eyes, governmental spectrum auctioneers started to sell off microwave frequencies in block licenses. The need for fixed microwave wireless services then was growing and has only grown fiercer with each additional iPhone and iPad that has been activated. However, access device throughput demand on one side of a base station does not necessarily fully translate all the way to the backhaul. Lazarus points out the example of now defunct FiberTower and its failure to make block microwave licenses work economically. After buying national block microwave backhaul licenses at 24 and 39 GHz, Lazarus notes, the firm resold the frequencies to Sprint and a county 911 emergency network operator. But those were the only customers. Lacking a robust enough utilization of its licensed backhaul frequencies, FiberTower had several hundred of its licenses revoked by the FCC and was forced into bankruptcy November 2012.

Subsequent auctions have attracted far fewer bidders and generated much less income for the Treasury Department. Much bandwidth has lain fallow as a result. And infrastructure buildout has stagnated.

Regulators should return the microwave backhaul licensing process to that of letting wireless transmission engineers cooperate informally among themselves, with the help of frequency-coordination firms, to arrive at fixed point-to-point wireless plans in the public interest. These are then submitted only for maintenance by the FCC or other regulators for traditionally nominal license fees—currently $470 per transmitter site for 10 years in the U.S., per Lazarus.

Forget the quixotic quest for chimerical hard currency. The commonweal demands it. You should demand it of the regulators—you can still give input regarding this scheme in some jurisdictions where it is under consideration. Clearly, the most efficient use of spectrum is to make it openly available to all because it means that every scrap of commercially useful spectrum is picked clean. We welcome your comments pro or con.

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Successful financial trades depend on ultra low latency microwave networks. Photo credit: francisco.j.gonzalez / Foter.com / CC BY

Germany is well-known for its autobahn highway system, where there are no official speed limits. Now there is a new high-speed network that traverses Western Europe from Frankfurt in Germany to London in the UK.

In addition, you may have read elsewhere in recent weeks about low latency microwave networks being constructed in the United States in support of the financial markets. The busiest route there is between the financial centers in Chicago and New York, where microwave can shave off 5 milliseconds off the transmission time along the 700 mile (1,000 km) route when compared to fastest fiber network (13 milliseconds). This saving directly equates to revenue for trading houses that are able to leverage this speed advantage.

In the United States, planning and deploying a point-to-point (PTP) microwave network is relatively predictable and straightforward: acquire sites and avoid interference from other network operators. Where PTP wireless networks cross state boundaries, a network operator need only deal with the national telecom regulator, the Federal Communications Commission (FCC), when obtaining required licenses to operate the microwave system.

But in Europe, this is a very different matter. While trans-European fiber networks have been a reality for many years, a microwave route like London to Frankfurt must traverse several national borders, forcing operators to deal with multiple regulators, with complex negotiations needed for microwave paths that cross national boundaries. For this reason very few—if any—microwave networks of this type have been built, up until now. However, the opportunities offered by the combination of the new low latency sector, along with the performance advantage of microwave over fiber, have now made the case  for these kinds of networks compelling enough to outweigh the challenges, and costs, of planning and implementing them.

For a low-latency microwave network servicing the financial sector on the London-to-Frankfurt route, there are a number of major challenges beyond just identifying and securing suitable sites and coordinating frequencies. The difficulty of planning a long trunk route is also greatly exacerbated by going through the densely urbanized region of Western Europe. This results in a constant iteration between finding the right route, identifying accessible sites, and securing required microwave frequencies. To be successful you need all three—a site on a great route is useless if no microwave spectrum is available. All the while, there are other competing providers all trying to complete the same route in the fastest time possible—not only in latency terms, but also time to revenue.

This poses huge potential pitfalls in having to take the long way around, requiring additional sites and links, if a site is not available. The added latency caused by any such deviation could kill the entire project. This race is like no other in the microwave business—whoever is fastest wins first prize, and it is winner take all in this competition. The potential revenue for the London-to-Frankfurt low-latency path is quite staggering, even on a regular day, but on busy days when the market is volatile the potential can be much higher.  Operators can plan on recouping their total investment in the microwave network in well under a year. Then once you have the most direct route, compared to your competitors, your problems may not be over, so it can come down to squeezing those extra few microseconds, or even nanoseconds, out of your equipment.

On this particular route there is also one significant natural barrier to contend with—the English Channel. There are only a few ways across that are short enough to allow a reliable microwave path, space diversity protection is a must and only a few towers are tall enough to support these distances. Even though there are no obstacles over the channel (apart from the occasional container ship), towers need to be high enough to allow the microwave signal to shoot over the bulge of the earth. Again, securing tower space at these sites is critical to success, but also obtaining the right to use one or more of a finite pool of available frequency channels, otherwise fiber may be needed across this stage, adding latency. One group even took the step of purchasing a microwave site in the Low Countries to secure it precisely for this purpose.

London to Frankfurt will only be the start for low latency microwave networks in Europe, as there is always a need and an opportunity to provide competitive transmission services to other financial centers throughout the continent. The winners will be those with the speed and agility to quickly seize these opportunities, along with working with the right microwave partner who can help them with the intensely complex business of planning and deploying these trans-national networks, and who can also supply microwave systems with ultra-low latency performance.

We will have more to say publicly on this topic in the near future. Or if you prefer not to wait that long, we would be more than happy to have a private conversation about low-latency microwave with you.

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John Lennon was still alive when Aviat’s oldest microwave link first went operational in 1980. Photo credit: Roy Kerwood / Foter.com / CC BY

The year was 1980. The Americans beat the Russians for the Olympic gold medal in hockey. John Lennon of The Beatles was killed. Mount St. Helens erupted. The Soviet Union had just invaded Afghanistan. Ronald Reagan was elected president. The hostages were still in Iran. People asked themselves, “Who shot J.R.?” and caught Pac-Man fever. Voyager 1 flew by Saturn and left the solar system. The Empire struck back. John Belushi and Dan Aykroyd were on a “mission from God.” The Clash came calling on London. Led Zeppelin broke up. And Farinon Electric, Aviat Networks’ direct predecessor, put into service a series of analog microwave radio hops for the Canadian province of Nova Scotia’s Department of Natural Resources. The radios in question were the SS2000 model.

The province used them to carry government data traffic for firefighters and police, where data bits were stuffed into 4kHz voice channels. Remarkably, 33 years later, three hops of these SS2000 radios are still in operation, making these, quite possibly, the world’s oldest continuously in-service microwave links.

Farinon SS2000 analog microwave radio transmitters (but not entire units) were available for sale on eBay as recently as 2011! How’s that for longevity?!

Offering 120, 300 or 600 voice channels on the old 2GHz band, SS2000 radios were considered cutting-edge technology at the time—check out their cool retro-style data sheet—and highly reliable with their ability to provide microwave links despite the challenging weather and difficult propagation conditions of Nova Scotia—snow, ice, sleet, fog…they have it all! As proof, four other SS2000 radio hops were recently decommissioned and found to still be working up to spec as per the original, accepted level of performance. Then there was someone selling SS2000 radios on eBay in 2011!

But we challenge you, our loyal blog readers, to tell us of any even older microwave links that have been in operation for more than 33 years. So if you have an Aviat Networks link, or that from a predecessor company, which is still operating today and was installed before 1980, please comment! We want to hear from you!

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P25 continues to be the only source of mission-critical voice, and the consensus is that will not change for maybe 10 more years—or longer. We saw really cool product enhancements from Motorola and Harris. Clearly, there is plenty of investment continuing in P25, and vendors believe they will get a return on that investment. There is still a tremendous amount of work to be done on going from analog to digital systems and wideband to narrowband.

In contrast, LTE broadband will probably take another 1.5 years just to get to the stage of RFQs. However, we did see a lot of innovative technology and interoperability demonstrations. Who would have thought that Harris handheld radios would be located in the Alcatel-Lucent booth and Motorola in the Raytheon booth?

There were many talks on FirstNet strategy and planning. Chief Dowd said FirstNet would announce a general manager within a couple weeks…let’s hope it is a public safety professional with many years of experience in setting up mission-critical networks. Of course, the industry pundits were there to discuss their view of this enormous challenge…unfortunately it appears the thinking is still very divergent…which can only mean that someone is going to be disappointed by the decisions FirstNet will make.

Many provider-based discussions were also held. For example, Aviat’s own Gary Croke gave a presentation on the considerations that any organization must make for high-speed backhaul and how microwave fits into those.

Lastly, we heard some excellent talks on engineering this network. Skilled network designers like Bob Shapiro gave us some insight into how the LTE network will look different from P25 networks (e.g., number of basestations, capacity of traffic, complexity of design). Good news is the industry is developing some excellent design tools to aid in designing the network.

The signs are positive for the public safety industry. IWCE show attendance was good, vendors showed up with real innovation and investment in new products, the Public Safety Broadband Network continues to move ahead…cannot wait for APCO in the fall!

Randy Jenkins
Director Business Development
Aviat Networks

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Although, Paul did have plenty to present regarding capacity. For example, with proper use of rings, overbooking, QoS, XPIC and other techniques and technologies, microwave backhaul can provide 400 Mbps-plus throughput. Compare this to the realistic throughput demands of a typical LTE site that max out at about 100 Mbps.

He also delved into the emerging backhaul category for Small Cells—designed to supplement traditional cellular infrastructure. The fact is that traditional techniques of deploying cellular macrocell basestations will be insufficient to provide broad enough coverage for this LTE wireless technology. To augment macrocell coverage for LTE mobile telecommunications providers have been investigating, trialing and, in some cases, deploying one or more of several small cell technologies (e.g., picocell, microcell, femtocell). Consequently, new methods will be needed to backhaul traffic from Small Cell sites.

Fiber backhaul may not be available at all small cell sites and when it is it could be very expensive to trench long distances. Regular line-of-sight (LOS) microwave with its parabolic dishes could prove aesthetically unsuitable for many Small Cell locations and/or difficult to install. Non-line-of-sight (NLOS) microwave and millimeter-wave point-to-point and point-to-multi-point wireless may have their applications, but their latency of 5-10 ms may be too much for real-time applications and voice—not to mention licensed spectrum is costly and unlicensed spectrum is very risky due to interference issues.

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Ultra-long microwave links between backhaul towers enable long-distance telecommunications in the Mojave Desert. Photo credit: °Florian / Foter.com / CC BY-SA

Designing and engineering microwave radio networks has always been challenging and a bit of an art—especially when they are ultra-long point-to-point wireless networks. In an article published February 25, 2013, Aviat’s solutions architect Charles Dionne outlines some of the key considerations that need to be made when designing and building these ultra-long microwave backhaul links for point-to-point wireless networks.

The article on RCR Wireless provides an overview and detailed checklist of the relevant items for designing ultra-long point-to-point wireless microwave links including:

• Site selection
• Frequency selection
• Antenna size
• Atmospheric conditions

Readers will take away more than just a laundry list of potential pitfalls; they will gain an enhanced appreciation of the very specialized skills and thorough understanding of microwave technology that is necessary for successfully implementing point-to-point wireless microwave backhaul.

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Figure 1: QAM modulations and associated bits/symbol and incremental throughput increases

1. What is QAM?

Modulation is a data transmission technique that transmits a message signal inside another higher frequency carrier by altering the carrier to look more like the message. Quadrature Amplitude Modulation (QAM) is a form of modulation that uses two carriers—offset in phase by 90 degrees—and varying symbol rates (i.e., transmitted bits per symbol) to increase throughput. The table in this blog post (Figure 1) describes the various common modulation levels, associated bits/symbol and incremental capacity improvement above the next lower modulation step.

2. Must all operators who use microwave backhaul use higher-order QAMs?

Higher-order QAMs are not necessarily a must-have for all network operators. However, higher-order modulations do provide one method of obtaining higher data throughput and are a useful tool for meeting LTE backhaul capacity requirements.

3. What is the main advantage of using higher-order QAMs with microwave radios?

The main advantage is increased capacity, or higher throughput. However, capacity improvement diminishes with every higher modulation step (i.e., moving from 1024QAM to 2048QAM the improvement is only about 10 percent!), so the real capability of higher-order modulations alone to address the objective of increasing capacity is very limited. Other techniques will be needed.

4. What are the tradeoffs of higher-order QAMs on RF performance?

First, with each step increase in QAM the RF performance of the microwave radio is degraded as per the Carrier-to-Interference (C/I) ratio. For example, going from 1024QAM to 2048QAM will produce an increase of 5 dB in C/I (Figure 2). This results in the microwave link having much higher sensitivity to interference, making it more difficult to coordinate links and reducing link density. Along with this increase in phase noise there will be an increase in design complexity cost.

Figure 2: Using higher-order QAMs entails making tradeoffs in increased C/I noise and reduced system gain.

Also, by increasing from 1024QAM to 2048QAM, system gain will decrease from above 80 dB to just above 75 dB (Figure 2). With much lower system gain microwave links will have to be shorter and larger antennas will have to be employed—increasing total cost of ownership and introducing additional link design and path planning problems.

All of the above are the results of linear functions: they degrade in a one-to-one relationship with the move to higher-order QAMs. Meanwhile, the capacity increases derived from higher-order QAMs are the function of a flattening curve: Each step increase in QAM results in a reduced percentage increase in capacity compared to prior increases in QAM. The added capacity benefits are diminished when considering the added costs of higher C/I and lower system gain.

5. Do you need to use Adaptive Coding and Modulation (ACM) while using higher-order QAMs?

ACM should be implemented while employing high-order QAMs to offset lower system gain. However, while ACM does help mitigate the effects of more difficult propagation when using higher-order modulations, it cannot help offset increased C/I.

6. What gives Aviat Networks a “heads-up” here when other big name companies seem to be supporting the technology?

Aviat Networks realizes higher-order modulations are not a panacea—a cure-all. While every minor technology improvement in throughput can help, a focus on technologies that grow capacity in hundreds of percentage points vs. tens of percentage points is most critical now. Aviat believes that these hundreds-of-percentage-points-of-improvement-in-capacity solutions will be the most important moving forward. It is in these technologies that Aviat has a “heads-up.” Such techniques include deploying more spectrum—particularly in the form of multichannel RF bonding (N+0) solutions—to achieve a minimum of 200 percent capacity increase. This technique is subject to frequency availability, but with flexible N+0 implementations (such as being able to use frequency channels in different bands and different channel sizes) many congestion issues can be avoided.

Second, intelligently dimensioning the backhaul network based on proven rules, best practices and L2/L3 quality of service (QoS) capabilities is another technique to provide potentially very large gains in backhaul capacity. Higher-order modulations can be one tool to achieve required capacity increases in the backhaul network. However, their inherent drawbacks should be well understood, while the most attention should be paid to other techniques that deliver more meaningful and quantifiable benefits.

7. Will operators need to “retrofit” microwave radios to be capable of higher-order QAM operation in their existing microwave infrastructure? Or will completely new hardware be required?

This depends on the age and model of the existing radios. Older microwave systems will likely need to be “retrofitted” to support 512QAM and higher modulations. Recently installed microwave systems should be able to support these technologies without new hardware.

8. How will QAM evolve in the future? Is the introduction of higher-order QAMs an indefinite process, with no end in sight?

The introduction of higher-order QAMs is not an endless process. As per Figure 1 above in this blog post, the law of diminishing returns applies: Throughput percentage improvement declines as modulation rates increase. The cost and complexity of implementing higher-order QAMs probably is not worth the capacity increase benefits derived—not past 1024QAM, in any event.

Gary Croke
Director, Marketing and Communications
Aviat Networks

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