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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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.

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Wireless Services: Stepping Outside the ‘Box’

Map of Nigeria

Nigeria, in the heart of West Africa, is home to leading mobile operator MTN Nigeria and the hottest wireless carrier market on earth.

Customers are looking for partners who can do more than just provide them with “boxes.” To really partner with customers, sometimes you have to step outside of the box. Providing a comprehensive, advanced Spares Management Program solution to MTN NigeriaAviat Networks’ largest customer and a major Tier 1 mobile network operator in Africa—is a prime example of what can be accomplished when stepping outside of the box.

Challenging Environment

As many are aware, Africa represents a challenging operating environment where on a daily basis mobile operators have to contend with power outages, lack of infrastructure and a shortage of trained personnel. Due to these issues, MTN Nigeria was experiencing significant challenges with its spares management related to its overall installed base of network equipment. This included having more spares than were needed but never having the right spare in the right place at the right time.

Even though the customer had a large supply of spares as part of capital expenditures, it was actually very difficult to keep track of the physical inventory. In this situation, MTN Nigeria asked its suppliers to manage the problem. Each supplier was to take accountability for owning and managing the problem for the customer.

For more, see the complete customer success story.

Ross Gillette
Director of Services, Africa, 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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Hybrid Microwave for Wireless Network Backhaul Evolution

Microwave telecommunications tower, silhouette...

Image via Wikipedia

There is no one-size-fits-all solution for wireless network backhaul. What will work for some operators’ mobile backhaul will not work for others. Many operators have large installed bases of TDM infrastructure, and it is too cost prohibitive to uninstall them wholesale and jump directly to a full IP mobile backhaul. There is going to be a transition period.

The transition period will need a different breed of wireless solutions. Fourth Generation Hybrid or Dual Ethernet/TDM microwave radio systems provide comprehensive transmission of both native TDM and native Ethernet/IP traffic for smooth evolution of transmission networks. They will enable the introduction of next-generation IP-based services during this transition period.

We will explore this category of digital microwave technology for wireless backhaul, which is becoming ever more important as the 4G LTE wireless revolution gets underway with all due earnestness, even while the current 3G—and even 2G—networks continue to carry traffic for the foreseeable future.

Our current white paper builds on Aviat Networks‘ previous April 2010 white paper titled “What is Packet Microwave?” and provides market data from recent industry analyst reports that demonstrate the significant and continuing role of TDM in mobile backhaul networks and some of the prevailing concerns of operators in introducing Ethernet/IP backhaul services.

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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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Backhaul for the Mobile Broadband or Wireless Broadband Network

iPad con dock y teclado inalámbrico

Image via Wikipedia

As 2G and 3G networks enter the upgrade path to 4G wireless, it will require that more than the base stations receive new wireless solutions. The path to LTE wireless—odds-on favorite to be the dominant 4G technology—is paved with increasing data demand from smartphones, iPads, other tablet PCs, electronic readers and probably some other intelligent mobile computing devices yet to be imagined.

All these devices will place throughput demands on the base stations, which in turn will place greater demands on the mobile backhaul network. Even as 4G devices place demands on mobile backhaul, the 2G and 3G technologies will be in place for sometime, coexisting in the same networks with 4G. In these situations, IP/Ethernet will be the next-generation networks‘ transport technology of choice.

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Aviat Networks: Official Wireless Transmission Headquarters

The Aviat Networks Headquarters in Santa Clara is perfectly positioned to serve its wireless customers. Watch this video to see the full capabilities of the Aviat Networks North American offices.

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CTO Insights from Mobile World Congress 2011

Aviat Networks SVP and CTO, Paul Kennard, shares technology trends and insights from Mobile World Congress 2011.

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