Aviat’s FAS Expert System software is custom built to monitor and detect interference, perform trend analysis of the network over time to track the growth of interference, and isolate problem links often before noticeable impacts occur.
Aviat Networks is the leading pure play microwave, software and services provider, with unrivaled microwave expertise. Learn more about our end-to-end transport solution portfolio in our corporate presentation.
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.
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.
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
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
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
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
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.
Last Friday, 03 August 2012 saw the release of FCC Report and Order 12-87, which contained some significant changes that will lower the total cost of ownership for many microwave links. The two most significant changes concern antenna sizes and wider bandwidths.
Following lobbying by Comsearch and the Fixed Wireless Communications Coalition (FWCC), within which Aviat Networks plays an important role, the FCC has allowed an additional alternative set of antenna parameters to be used in the 6, 18 and 23GHz bands. These new parameters are an alternative to the existing antenna parameters, which have been retained. It is worth noting that while the FCC does not specify actual antenna sizes, the realization of antennas based upon these new parameters does represent a reduction in size and thus provides for the reduced cost of both CAPEX and OPEX that has already been championed by Aviat Networks and other interested parties. The new working alternative antenna parameters are as follows:
3 feet for the 6GHz band
1 foot for the 18GHz band
8 inches for the 23GHz band
To put these changes into perspective the typical cost of renting space for an antenna on a tower is US$400 + US$100 per foot (diameter) per month. So a link consisting of two 6ft antennas will cost 2x (400 + 6×100) = $2000 per month, i.e. $24,000 per annum.
If the antenna diameter could be reduced to 3 feet the cost is reduced to 2x (400 + 3×100) = $1400 per month, i.e. $16800 per annum—a saving of $7200 per year on a single link!
The above calculations are not only ours but also those of MetroPCS, which is quoted in the report and order. MetroPCS specifically notes, as an example, that “the cost of a microwave dish antenna is approximately $100 per foot per month. Thus, even if the revised rule allows for a reduction of just one foot, the annual savings would be $1,200, and the savings over a ten year period would be $12,000.”
Smaller antennas also open up more options in terms of locations for these antennas, and their smaller size reduces wind loading and the need for specialist mountings and strong towers.
Additionally, the FCC in a further notice of proposed rule making attached to this report and order seeks feedback on allowing similar alternative antenna parameters in the 11 and 13GHz bands. Aviat Networks intends to support this proposal via the FWCC.
With the ever-growing demand for bandwidth the FCC has decided to allow aggregation of two 30MHz channels in the 6GHz band and two 40MHz channels in the 11GHz band, giving maximum bandwidths of 60MHz and 80MHz, effectively allowing a doubling of the capacity of a microwave link. This represents another significant cost saving because this increased capacity can be achieved with the same amount of hardware.
Also in this report and order were changes to the definition of efficiency standards to a bits/sec/Hz standard as proposed by the FWCC, and a clarification of the definition of payload capacity: “The bit rate available for transmission of data over a radiocommunication system, excluding overhead data generated by the system.” The FCC has also introduced a welcome simplification of the rules with regard to bit rate efficiency. FCC Part 101.141 has been amended to include a table (below) that details the efficiency criteria according to two frequency ranges and three bandwidth ranges:
Aviat Networks welcomes the FCC’s progressive changes as the amendments will stimulate the microwave industry and enhance the cost effectiveness of microwave networks across the United States. We expect the rule changes to be effective approximately in October.
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.
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:
Recently 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.
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.
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 spectrum—comprising 280 MHz of underused commercial spectrum and 220 MHz of federally owned radio spectrum now administered by the NTIA—would 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 releases—especially in the 4 to 8GHz range—which is suitable for high-capacity trunking backhaul.
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