Telecom Industry Participants call on FCC for E-band Action

While U.S. regulators decide on flat-panel antenna rules for E-band, operators and subscribers walk a tightrope of red tape.

While U.S. regulators decide on flat-panel antenna rules for E-band, operators and subscribers walk a tightrope of red tape.

Back in April the telecom experts over at CommLawBlog weighed in on a simmering issue in the 70-80GHz radio space. Since October 2012, the Federal Communications Commission (FCC) has mulled over a motion by the Fixed Wireless Communications Coalition (FWCC) to relax rules for flat panel antennas as well as a 2013 waiver to the existing rules while it considers a new rulemaking.

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Should National Telecom Regulators Impose Buildout Requirements on Operators?

FCC-Ofcom-and-other-national-wireless-regulators-should-have-spectrum-use-it-or-lose-it-policy-says-microwave-vendor-Aviat-Networks-August-23-2013

Photo credit: fingle / Foter / CC BY-NC-SA

In the mobile operator space in many countries, the national regulators are imposing so-called “buildout requirements” as a license condition on many wireless providers. In some countries, these requirements are restricted to licenses awarded by the auction process (e.g., cellular access spectrum) or block allocations while in others these conditions are attached to the majority of licenses.

Where buildout requirements are employed, a license typically has a clause that requires the licensee to build out a network/link or specified portion of a network within a certain period of time, with penalties imposed for failure to do so.

The rationale behind imposing these requirements is to ensure that after spectrum is assigned it is put to its intended use without delay. By doing this, or so the theory goes, bidders are discouraged from acquiring spectrum with the sole intent of blocking competitors’ activities without themselves offering service. Of course, the ultimate goal is the protection of spectrum—a finite and precious resource. There is no reason buildout requirements cannot be attached to any license grant, assuming that the detail of the requirements recognizes any constraints of the application for which the spectrum is sought.

Nevertheless, Aviat Networks is strongly against auctions and block allocations, but where these are a necessity then buildout requirements must be part of any award, with strong enforcement rules. The problem is that with strong enforcement operators and regulators can be at loggerheads and get tied up in court with lawsuits and countersuits for years. For example, in the U.S. you have the case of Fibertower. The FCC claims that Fibertower deliberately underbuilt its network and so moved to revoke its spectrum licenses. With the regulator moving against the operator, it came under insurmountable financial pressure and filed for bankruptcy. But even now, the operator’s creditors are fighting the FCC in order to recoup frequencies valued at more than US$100 million. So it is questionable whether this actually works in practice.

Microwave is the point
Focusing on point-to-point microwave, let’s examine the approach taken in two different countries. In the United States, for traditional link-by-link allocation, the FCC imposes an 18-month deadline by which time the link in question needs to be in service. However, in the United Kingdom, Ofcom imposes no such deadline. For certain applications, certain routes and sites are critical and can quickly become “full.” If these key locations are being filled by license applications that are not being translated into operational services, then this spectrum is effectively wasted as no one else can use it, nor is there any service being offered. Spectrum wasted in this manner reduces overall spectrum efficiency, and all spectrum authorities are motivated to ensure that spectrum is used in the most efficient way possible.

Of course having these rules is fine, but what happens when the rules are breached? In some cases, an operator will apply for an extension prior to the expiration of the original deadline; this may or may not be granted. However, the real test is what happens when the deadline passes. Ideally, what should happen is that the license(s) in question would be revoked and the associated spectrum made available for reallocation. Furthermore, if the spectrum in question was originally made available by block allocation or auction, then again, ideally, this spectrum should be returned to the pool of spectrum available for link-by-link licensing.

Additionally in shared bands, i.e., spectrum shared by the Fixed Service (FS) and the Fixed Satellite Service (FSS) should be governed by the same requirements in this instance. Therefore, unused/defunct FSS allocations/licenses should also be revoked with the spectrum being made available for reuse. In the case of FSS locations, this can have a significant effect owing to the geographic full-arc protection area that is usually associated with earth stations.

Counterpoint
The alternative viewpoint is that the current buildout requirements are counterproductive, in their aim to foster efficient use of spectrum. One reason cited for this view is that it takes time for an equipment supply ecosystem to develop, which will serve the spectrum users. However, when we examine this claim more carefully, it seems that this is often used where the spectrum has been awarded to a single user either by block allocation or by auction. We have written before about how auctions and block allocations are unsuitable for point-to-point microwave, and the claim above is a direct result of this process, which negatively impacts the number of operators. In turn, that reduces the ranks of equipment vendors, leading to thinner competition and, therefore, decreased incentive for innovation. This situation is made worse if the operator in question chooses a band plan that is nonstandard in terms of either existing U.S. or international arrangements.

Signal termination
In the final analysis, it does not serve any stakeholders’ goals to have valuable spectrum allocated but unutilized. Thus, having buildout requirements would appear to be a good idea. But along with that, an effective mechanism for reclaiming and making available to others spectrum that runs afoul of these rules is paramount to making the process work for the Greater Good. In Aviat’s view, buildout requirements are a valuable tool in ensuring spectrum efficiency and as such, their use should be seriously considered in all countries.

Ian Marshall
Regulatory Manager
Aviat Networks

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5.8GHz FCC Rule Change: Good or Bad?

Microwave-radio-wireless-fixed-services-Backhaul-link-FCC-5GHz-rule-change-would-be-detrimental-comment-by-June-24-2013

Photo credit: John “I’m…kind of…fun” L / Foter.com / CC BY-NC

In the United States, the fixed service for wireless communications usually operates in bands licensed either on a link-by-link basis or by block allocation. So why is the 5.8GHz ISM band so important and why should the industry be concerned about current FCC proposals to change the rules of operation in this band.

Many operators use this band because they can install and operate a link in a very short period—much quicker than the usual route of prior coordination and license application that is required in other bands. There are numerous reasons why this approach is attractive, even if it is difficult to guarantee Quality of Service (QoS) in ISM. A common use of this approach sees the operator set up a link in the 5.8GHz band to get the link up and running while in parallel it goes through the coordination process for the same link in the L6GHz band. Then when that license is granted, the operator will move the link to the L6GHz band. This has the advantage that the same antenna may be reused and sometimes the same radio with just a filter change. Another use of the 5.8GHz band for fixed service links is in support of disaster relief efforts where because there is no need for prior coordination that means vital communications links can be up and running very quickly.

Under the current FCC Part 15 rules, equipment can be certified using section 15.247 whereby the above scenarios are attractive to operators as they mimic the conditions that can be found in the L6GHz band. However, the FCC has issued a notice of proposed rulemaking, NPRM, which will change this by requiring a reduction in conducted output power of 1dB for every dB of antenna gain over 23dBi for Part 15.247 point-to-point links. At present, the conducted power at the antenna port in this frequency range is limited to 1 watt, but there is no penalty applied to the conducted power in relation to higher gain antennas on point-to-point links. Should this proposal by finalized then this would reduce the effective range of point-to-point links in this band and would so change the dynamics that the ability to deploy a link in the 5.8GHz band and then “upgrade” to the L6GHz band at a later date would no longer be a feasible option. We would encourage all readers, especially those using the 5.8GHz band to file a comment with the FCC regarding Proceeding 13-49 that this particular change would be detrimental to many fixed link operators, as well as those who rely on this band for fast deployment during disaster recovery.

For more information on this proceeding, email Aole Wilkins at the Office of Engineering and Technology.

Ian Marshall
Regulatory Manager
Aviat Networks

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The Gavel Comes Down: Auctions are Bad for Wireless Backhaul

Blue-payphone-unless-you-want-to-go-back-to-this-cellular-phones-need-cooperatively-licensed-microwave-backhaul-to-function-properly

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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Low Latency Microwave Crosses Europe for the First Time

financial-trades-depend-on-ultra-low-latency-microwave-point-to-point-wireless-networks

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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Wireless Regulators Move to Prevent Spectrum Waste

Historically, in many countries the 26GHz and 28GHz wireless frequency bands have been allocated to point-to-multi-point systems, such as LMDS in the United States and LMCS in Canada. However, most of these systems have failed to reach their expected potential in terms of revenue generated and, as such, much of the allocated spectrum is now unused. This, along with the growth in demand for point-to-point microwave spectrum, has meant a number of national regulators have started to consider reallocation of this spectrum.

In Canada, the spectrum allocations for both the 26GHz and 28GHz bands have been revisited, owing to their underutilization by LMCS operators, with a new band plan having been developed during the drafting of SRSP 325.25. The diagrams below show the new allocations that accommodate more FDD spectrum suitable for microwave in point-to-point usage.

Figure 1 - 25.25 - 26.5 GHz Band Plan and Associated Usage - Industry Canada

Figure 1 – 25.25 – 26.5 GHz Band Plan and Associated Usage – Industry Canada

While the technical details of this draft SRSP have been finalized, consideration of licensing options by Industry Canada has so far delayed the formal publication of this SRSP. Note that the remaining point-to-multipoint operators are catered to in the TDD section in the middle of the 26GHz plan.

Figure 2 - 27.5-28.35 GHz Band Plan and Associated Usage - Industry Canada

Figure 2 – 27.5-28.35 GHz Band Plan and Associated Usage – Industry Canada

In the Republic of Ireland, ComReg (the Irish national telecommunications regulator) recently issued a consultation resulting from an operator request to change the use of its allocated spectrum from point-to-multipoint to point-to-point. Figure 3 shows the current situation in Ireland and Figure 4 shows the same band after the proposed change of use.

Figure 3 - Current 26GHz Band Plan - ComReg Ireland

Figure 3 – Current 26GHz Band Plan – ComReg Ireland

In the United States, the LMDS service occupies the following spectrum blocks:

  • 27.5 – 28.35 GHz
  • 29.1 – 29.25 GHz
  • 31.075 – 31.225 GHz
  • 31.0 – 31.075 GHz
  • 31.225 – 31.3 GHz

Thus, that would make a total of 1300MHz of spectrum—more than double the recent allocation at 7 and 13GHz—potentially available across the entire country. LMDS take up has been very low, and, as previously mentioned, much of this spectrum is now unused. This begs the question: Would spectrum reallocation in the U.S., as is happening in Canada and Ireland, promote its more active usage?

Figure 4 - Revised New 26GHz band plan - ComReg Ireland

Figure 4 – Revised New 26GHz band plan – ComReg Ireland

It is worth noting that existing users are protected in both the examples given above, but unused spectrum is now available to point-to-point operators. Therefore, it is now time to approach the FCC and request a similar exercise to be carried out for the United States. Aviat Networks intends to be one of the driving forces in requesting this reallocation of spectrum.

Ian Marshall
Regulatory Manager
Aviat Networks

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Microwave Backhaul for Public Safety LTE

US Navy 031026-M-4815H-029 Fire fighters from ...

(Photo credit: Chance W. Haworth via Wikipedia)

Public safety agencies will soon experience a dramatic improvement in communications capabilities enabled by advances in technology. New broadband multimedia applications will give first responders and commanders alike far better situational awareness, thereby improving both the effectiveness and safety of all personnel charged with protecting the public.

The specific technology, now mandated by the U.S. Federal Communications Commission (FCC) for all new emergency communications networks, is Long Term Evolution, or LTE—a fourth-generation (4G) broadband solution. The FCC has also allocated licensed spectrum to ensure the best possible performance in these new networks. These FCC rulings support the goal of achieving an interoperable nationwide network for public safety agencies.

The FCC chose LTE based on its proven ability to support voice, video and data communications at remarkably high data rates that were previously only possible with wired links. Although there will be some differences in a nationwide public safety network involving capacity and coexistence with Land-Mobile Radio communications, lessons learned from LTE’s deployment in large-scale commercial mobile operator networks will help ensure agencies are able to achieve the FCC’s goal cost-effectively.

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42GHz: A New Global Standard for Wireless Backhaul?

Parabolic antennas

With ever-increasing demand for spectrum in fixed services, FWCC has endorsed opening up the 42GHz band as a new global standard for microwave backhaul. (Photo credit: Miguel Ferrando via Wikipedia)

An ever-increasing demand for spectrum has recently turned focus on the 42GHz band. Initially opened in some European countries following the development of ECC REC(01)04, the recently published ECC Report 173 states 12 countries have opened this band including Germany, Norway, Poland, Switzerland and the United Kingdom. In the U.K., this band was part of a wider auction of fixed service bands in 2010, with three operators being granted blocks of spectrum in the 42GHz band as a result.

Building on this growth there is a move to make this band global and earlier this year saw the publication of ITU-R Rec F.2005, which in effect promoted the aforementioned CEPT recommendation to global status. Aviat Networks has been lobbying key regulators to open this band. We are eagerly awaiting a consultation from Canada and responses have already been submitted to recent consultations from France and Ireland containing considerations regarding opening this band. The process is also underway in Finland and Sweden to open up this band. Recently our attention has turned to the United States and whether the FCC will open this band for use by the fixed service.

Back in autumn 2011, Aviat Networks raised this topic within the FWCC (Fixed Wireless Communications Coalition) as the first stage of a petition of rulemaking to the FCC. At first there was only a lukewarm reception to our idea as there was concern that the FCC would refuse the request out-of-hand as some previously released spectrum below 40 GHz is underutilized and, therefore, why is more needed? We pointed out that much of this spectrum (e.g., 39 GHz) was block-allocated by auction and thus has not been readily available to all users and that the licensees have underutilized the spectrum. There is a growing need for spectrum that can be licensed on a flexible, site-by-site basis, and this is reflected by the fact that there are no underutilization issues in bands such as 18 and 23 GHz, which are licensed in this manner. It is no coincidence that auctioned bands tend to underperform in terms of efficiency and utilization. So, undeterred, we forged ahead and this resulted in the production of a FWCC petition to the FCC in May 2012. The FCC has recently placed this petition on public notice, per its procedures. This is a great success for Aviat Networks and our commitment to seeking more spectrum for the fixed service, but the story has not ended here as can be seen from a recent blog entry from the FWCC.

Aviat Networks will continue work with the FWCC to ensure that the FCC gives this proposal full consideration and, having learned important lessons from past spectrum allocations, we will lobby for a flexible approach to the licensing model.

Ian Marshall
Regulatory Manager
Aviat Networks

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Coverage Maps for New Wireless Spectrum Available to Fixed Services

United States radio spectrum frequency allocat...

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

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

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

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

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Are Auctions an Appropriate Way to Allocate Microwave Spectrum?

frequency auction imageRecently the U.S. Congress requested information from the FCC regarding the usage of the 11, 18 and 23GHz microwave point to point bands. This move is seen by many industry watchers as the first step in preparing these bands for auctioning.

Auctioning spectrum is seen by many in the political establishment as a good way of raising large sums of money.  The 3G auctions in Europe raised $30 billion in the U.K. and $45 billion in Germany and although these figures will probably never be reached again, the attraction for governments trying to balance the books in an economic downturn is clear to see. However, these figures were for cellular access spectrum and there is evidence of microwave spectrum auctions being priced too high for operators and no bids being received, e.g. the original 28GHz auction in the U.K during 2000-2002. But even if the bidding process itself is successful, is granting large amounts of spectrum to a single operator the right way to allocate microwave spectrum?

Let’s look a little deeper into how microwave spectrum is used and allocated in most cases today in licensed common carrier frequency bands. An operator wanting to install a microwave link between points A and B would seek to obtain an individual license for that link in that specific location and frequency. This allows others to apply for other frequencies or even the same frequency in different locations.  This approach maximizes use of the available spectrum.

Now let’s look at the block licensing approach. Here a block of spectrum (either on a national or regional basis) is allocated to one user. Block allocations on a regional basis make sense for multipoint applications like fixed wireless access or mobile network applications. However, in the case of point to point (PTP) allocation a block license holder may not have requirements for that entire spectrum, but because it is now their spectrum, no one else can gain access, often resulting in under utilization. This is the situation currently with the 38GHz band in the U.S. and is leading to some in the industry to push for the availability of additional spectrum.

Another example of this is the 28GHz LMDS band, where service take up has been very low, but has effectively blocked out this band from other uses/users. Another concern for the block licensing approach and one that affects equipment vendors is that with fewer operators there are fewer equipment contracts thus leading some manufacturers to be “frozen” out of the market. This will ultimately reduce choice for all and reduce innovation and competition.

Referring back to the announcement, it makes no mention of what would happen to the holders of existing link licenses who will have engineered their networks based upon the current rules. What would happen to these links should that band now be auctioned off as a block? Spectrum auctions also break the U.S. into many smaller regions, with each regional block license being auctioned to the highest bidder. This leads to the question of demarcation and coordination between adjacent regions, particularly for links that may need cross-regional boundaries.

All in all, it would appear that based on evidence to date, auctioning FCC Common Carrier microwave spectrum will be tremendously complicated and likely not in the long term interests of the industry.

Ian Marshall
Regulatory Manager
Aviat Networks

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What is Asymmetrical Link Operation?

Introduction
Last year one of our microwave competitors introduced a new development for the point-to-point licensed microwave market – asymmetrical link operation. There are some very real challenges with the growth of mobile multimedia that are driving interest in this approach. However there are numerous harsh realities involved in introducing such a ‘radical’ technique into the relatively conservative licensed microwave industry. The myriad of Regulatory studies and approvals that will be needed to enable asymmetric operation to be deployed in existing bands means that it could be years, if ever, before asymmetric links can be deployed in most countries around the world.

Today’s Licensed Microwave Bands are Exclusively Symmetric
In current licensed microwave bands and all commercially available equipment today, transmission is symmetric – i.e., the same capacity and bandwidth in both directions. Frequency bands are arranged for frequency division duplex (FDD) operation, where two identical channels are used for Tx (‘go’) and Rx (‘return’). Asymmetric operation is usually reserved for unlicensed time division duplex (TDD) radios, which use a single channel for both go and return.

Spectrum Borrowing
The proposed Asymmetrical scheme is based upon a concept called ‘Spectrum Borrowing’, where frequency spectrum is taken from the upstream direction of a lower capacity link, and given to the downstream direction of an adjacent higher capacity link.

What is Asymmetrical Link Operation?

Before - Symmetrical Microwave Network

A second (but related) proposal has been also tabled to amend the standard channel options from the current 7, 14, 28, 56 MHz to an n*7MHz arrangement (i.e. 7, 14, 21, 28, 35, 42, 49, 56 MHz), which is required to support the asymmetric concept.

What is Asymmetrical Link Operation?

Asymmetrical Microwave Network, after Spectrum Borrowing

What is driving the need for this Asymmetry?
The underlying rationale is that in 3G and 4G mobile networks, a majority of the traffic over the network is increasingly web- and video- based, meaning more capacity is needed in the backhaul network in the direction towards the base station, and less in the opposite direction back to the core.

However, while this is true today, new emerging mobile applications such as video chat, video uploading, P2P sharing, and new cloud based services (eg: iCloud), have the potential to change the imbalance between upload and download demand over the longer term. This presents a challenge for the proposed asymmetric implementation, which is fixed in nature, not dynamic. This means that the link has no way to adapt to instantaneous uplink/downlink traffic demand, or to change over time as more uplink capacity is needed. Changing this ratio could prove to be very difficult once an asymmetric link is in place and has been operating for several years.

Regulatory Approval
Making substantial changes in the way that licensed microwave bands are used is not a simple process, since strict regulations and standards at the international and national level have been put in place to ensure that links deployed in these bands are assured to be virtually interference free.

A proposal has now been submitted to the Electronic Communications Committee (ECC), the Regulatory Body responsible for amending the channel plans for the existing frequency bands, a part of the European Conference of Postal and Telecommunications Administrations (CEPT), representing 48 countries throughout Europe and Russia. The ECC has agreed to set up a study group to examine the proposal, which is due to report their finding in February 2013.

If the ECC agrees to amend the channel plans to permit asymmetric operation, which may not happen before 2015, the national regulator in each CEPT country will then have to decide whether or not to adopt the recommendations. Further lobbying will also be necessary beyond the CEPT region, for example with the FCC in the USA, to successfully influence regulatory policy in favor of Asymmetrical operation.

A Long Road to (Possible) Adoption
In summary, asymmetrical operation may be a potentially useful technique to improve the efficiency of backhaul networks and frequency utilization. However, introduction of this technique will be extremely difficult within existing congested frequency bands, and will face significant and lengthy regulatory scrutiny and approval before we will see widespread adoption.

Stuart Little
Director of Marketing

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Antennas: Why Size is Important for This Wireless Equipment

Antenna tower supporting several antennas. The...

Image via Wikipedia

In response to the recent FCC docket 10-153, many stakeholders proposed relaxing antennas requirements so as to allow the use of smaller antennas in certain circumstances. This is an increasingly important issue as tower rental costs can be as high as 62 percent of the total cost of ownership for a microwave solutions link. As these costs are directly related to antenna size, reducing antenna size leads to a significant reduction in the cost of ownership for microwave equipment links.

The Fixed Wireless Communications Coalition (FWCC), of which Aviat Networks is a major contributor, proposed a possible compromise that would leave Category A standards unchanged while relaxing Category B standards. The latter are less demanding than Category A, and after some further easing, might allow significantly smaller antennas. The rules should permit the use of these smaller antennas where congestion is not a problem, and require upgrades to better antennas where necessary.

A further detailed proposal from Comsearch proposed a new antenna category known as B2, which would lead to a reduction in antenna size of up to 50 percent in some frequency bands. This would be a significant cost saving for link operators.

At the present time, the industry is waiting for the FCC to deliberate on the responses to its 10-153 docket, including those on reducing antenna size.

See the briefing paper below for more information.

Ian Marshall
Regulatory Manager, Aviat Networks

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