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The fate of the L6GHz band for fixed microwave services could be decided when the World Radio Conference (WRC) meets in Geneva in 2015. Because these meetings at ITU headquarters only occur every three or four years, 2015 will be pivotal. Procedurally, at these conferences, delegates from member states review and—if necessary—revise the Radio Regulations, the international treaty governing the use of radio-frequency spectrum and geostationary- and non-geostationary-satellite orbits. They make revisions based on an agenda determined by the ITU Council, which takes into account recommendations made by previous world radiocommunication conferences.
Generally, the scope of world radiocommunication conference agendas is established four to six years in advance, with the final agenda set two years before the conference by the ITU Council, with concurrence of a majority of member states.
As WRC-15 approaches, many national regulatory authorities are busy harmonizing their national positions this year ahead of the actual conference in 2015. This conference is likely to see one of the biggest—if not the biggest—reallocations of spectrum ever undertaken. Much of this is currently being addressed under agenda item 1.1:
To consider additional spectrum allocations to the mobile service on a primary basis and identification of additional frequency bands for International Mobile Telecommunications (IMT) and related regulatory provisions, to facilitate the development of terrestrial mobile broadband applications, in accordance with Resolution 233 (WRC-12)
This will present the microwave community with a number of challenges and opportunities moving forward, one of which will be how we will address increased demand for capacity arising from mobile operators gaining huge swaths of additional access spectrum, enabling them to offer more and more high-demand, high-bandwidth services. This will require the regulatory environment governing fixed microwave to evolve at least in step or ideally ahead of this demand to ensure microwave remains an attractive and viable means for backhauling this access demand. The second challenge that the microwave community will face with WRC-15 agenda item 1.1 is more urgent: the proposal from Russia to open up the L6GHz band to mobile access.
The L6GHz fixed microwave band between 5925MHz and 6425MHz is available worldwide and with its propagation characteristics provides spectrum that is used for critical long-haul infrastructure links. The very nature of these links means that they are likely to be operational for many years and thus explains why many national regulators report stable and/or low growth in the number of licences issued in this band. In fact, with only a small number of channels available, in some locations congestion is becoming a problem. One scenario where use of this band cannot be replaced is when links have to cross open water, such as the Great Lakes in North America or the English Channel, the Oresund and the Aegean Sea in Europe. Here we see greatly increased activity from those building trans-national low latency networks linking together the various financial centers.
Now that we know the band’s use, why highlight it today? Admittedly, while the Russian proposal under agenda item 1.1 is for shared access between microwave and mobile access, many industry insiders realize that the two services cannot realistically live side by side in the same geography. It’s not possible because mobile access requires nearly blanket area coverage to be viable. Add the fact that user terminals can be anywhere means sharing is difficult if not impossible to achieve. Some have proposed that mobile access at this frequency will only be attractive in urban areas, leaving rural areas to microwave. This is fine until you need to cross or terminate your L6GHz microwave link in an urban area. In reality, this approach is more of a migration solution than a sharing solution and is not in the best interests of the microwave community.
What to do? The way WRC-15 works is that each member state has the same weighted vote as every other member. Consequently, any proposal for spectrum reallocation needs to be taken seriously. If there are concerns about a proposal then only by convincing a majority of national regulatory authorities of the validity of your argument can your position prevail. Aviat Networks has been working on several fronts in recent months to achieve a sufficiently large counter vote to the Russian proposals so that the status quo is maintained.
Lobbying national regulatory authorities Specifically, Aviat Networks and other members of the U.S. microwave community have been working to formulate an American position. At present, this looks promising in terms of our L6GHz stance. Aviat Networks is also active in many African countries helping formulate national positions to oppose the Russians. The position of the African countries is key in this debate because there is not the fallback of long distance fiber. With the distances involved copper has never been a viable option for high capacity services. The current cloud over all this is Europe. Even with Europe’s very strong bent toward supporting growth of cellular services, many countries are still undecided, a situation further complicated by Russia’s CEPT membership. For example, Ofcom (U.K.) despite industry efforts is still unwilling to commit to a definitive strategy—or view—although the regulator admits a position must be agreed upon prior to the conference.
The message above is simple: if you use or want to use the L6GHz band for fixed microwave services find out what your national regulator’s position will be under WRC-15 agenda item 1.1. Remember, there are many bands up for discussion under this agenda item so ensure that you get your answer for the 5925-6425MHz band. Moreover, check whether it is a definitive position then lobby for the status quo to remain and oppose the Russian proposal.
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.
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)
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:
On 9 August 2011, the FCC announced several changes to the rules (Part 101) that govern the use of microwave communications in the Fixed Service bands in the U.S. These changes are great news for operators and will be encouraging increased adoption of microwave technology as a wireless transmission alternative to fiber for next generation mobile networks and fixed/private networks.
New Frequency Band for Fixed Services
The FCC opened 650 MHz of new spectrum for Fixed Service (FS) operators in the 6875-7125 MHz and 12700-13100 MHz bands, which will be shared with the incumbent Fixed and Mobile Broadcast Auxiliary Service (BAS) and Cable TV Relay Service (CARS). These bands will primarily be used as an alternative to the 6 and 11 GHz “Common Carrier” bands in rural areas, where the band is not currently licensed to TV mobile pickup stations used in newsgathering operations.
Frequency allocations in these new bands should commence later this year and will be based upon the existing 25MHz channelization. To facilitate adoption, the FCC is also allowing the use of 5, 8.33 and 12.5 MHz channels, as well as 50 MHz channel operation in the 12700-13100 MHz band using two adjacent 25MHz channels.
Allowing Adaptive Modulation
Adaptive Modulation, or AM—or ACM when used with Adaptive Coding—is a relatively recent innovation in microwave technology that allows the radio to dynamically adapt to path conditions to allow a much higher degree of spectrum efficiency, increased wireless link throughput, use of smaller antennas or a combination of all three benefits.
Up until now, the use of AM was restricted by the requirement to comply with FCC spectrum efficiency rules, which dictate a minimum data rate for certain bands. For example in the 6 GHz band a minimum capacity of 130 Mbit/s, or 3xDS3, must be maintained at all times within a 30 MHz channel assignment, using 64QAM modulation. The FCC now allows AM operation where the capacity of the link may drop below the minimum data rate, as long as the operators “design their paths to be available at modulations compliant with the minimum payload capacity at least 99.95 percent of the time,” or in other words, operators will have to “design their paths to operate in full compliance with the capacity and loading requirements for all but 4.38 hours out of the year.”
Aviat Networks, through our membership of the Fixed Wireless Communications Coalition (FWCC), supported rule changes to permit ACM, and the FCC included in its Rulemaking (Clause 48) our analysis on the benefits of ACM in terms of reducing the costs associated with tower leasing:
By way of hypothetical, consider a single link in the 6 GHz band that would require 10-foot antennas with a 99.999 percent standard instead of 6-foot antennas under the 99.95 percent standard. The total cost increase over a 10-year period in this hypothetical example could exceed $100,000.
The smaller antennas offer a number of advantages over larger ones, including more TCO savings over those 10 years.
Still Under Consideration by the FCC
Of all the new proposals being considered, the FCC also announced a Further Notice of Proposed Rulemaking (FNPRM) to further investigate the following proposals:
Allowing Smaller Antennas in Certain Part 101 Antenna Standards without materially increasing interference
Exempting Licensees in Non-Congested Areas from Efficiency Standards to allow operators to increase link length in rural areas
Allowing Wider Channels, including 60 MHz in the 6 GHz band, and 80 MHz in the 11 GHz bands
Revising Waiver Standard for Microwave Stations Near the Geostationary Arc to align with ITU regulations
Updating Definition of Payload Capacity rules in Part 101 rules to account for Internet Protocol radio systems
Aviat Networks continues to work on these issues, via the FWCC, which we believe will assist operators in lowering their total wireless network operational costs by taking advantage of the newest innovations that are now available in microwave technology.
With these new rules, along with the potential for further changes under consideration, microwave solutions provide an even more compelling case to enable mobile operators in the U.S. to keep pace with the IP mobile backhaul capacity demand driven by the introduction of new 4G wireless/LTE wireless networks.
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