February 4, 2020
FWCC Webinar Recap: Potential problems permitting unlicensed RLAN operations in the 6 GHz band
As many readers are aware, the FCC issued a notice of proposed rulemaking (NPRM) regarding RLAN operation within the 6 GHz bands. Over the last two and a half years, the FWCC has dedicated itself to protecting fixed links from t in these bands. Understandably so, this is especially important given the diversity of fixed link users in the 6 GHz bands; among others, utility companies, oil and gas companies, and local government agencies, including those dealing with public safety, have large numbers of 6 GHz links that perform unique and crucial tasks. There are approximately 97,000 fixed links in the 6 GHz bands.
April 26, 2013
The Gavel Comes Down: Auctions are Bad for Wireless Backhaul
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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- Would Millimeter Waves be preferred Metrocell backhaul option? (ytd2525.wordpress.com)
- E-Band Global Regulation Roundup (aviatnetworks.com)
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April 19, 2013
Low Latency Microwave Crosses Europe for the First Time
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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November 9, 2012
Know Your Microwave Backhaul Options
If you look in the November issue of MissionCritical Communications, you will see an article by Aviat Networks director of marketing and communications, Gary Croke. In his article “Know Your Microwave Backhaul Options,” Gary covers:
- Benefits of using indoor, outdoor and split-mount microwave radios in various scenarios
- Rationale for choosing microwave over fiber (especially for LTE)
- Deployability of microwave
- Software-upgradeable capacity for “pay-as-you-grow” capex scalability
- Cost contribution of towers over the first 10 years of LTE implementation
- And more
You can read Gary’s article (on page-30) here—MissionCritical Communications—November 2012.
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October 23, 2012
Pole Sway and Small Cell Deployments for Wireless Backhaul
The two main vibration types for light poles are shown in this figure. Both of these two vibration types will create sway that might affect the link performance for small cell microwave backhaul.
There is real concern from operators that utility, streetlight and traffic poles are not designed to meet the minimum twist and sway standards for deploying microwave solutions for small cell backhaul. Our research suggests that not all poles are created equal, however. Under certain circumstances these structures can be an option for deploying microwave backhaul for small cells.
Twist and sway requirements for towers and poles that support microwave backhaul hops are more stringent than for other RF equipment. This is especially true for deployments in frequency bands above 18 GHz where the antenna beamwidth is narrower than below 18 GHz. Standards such as the TIA-222-G set a minimum twist and sway that a structure should be able to endure for hosting a microwave installation. This creates concerns for operators interested in deploying microwave for small cell backhaul on structures including utility, streetlight and traffic poles that are not designed to meet this standard. Although the use of a sturdy structure is always recommended a close look at utility, streetlight and traffic poles suggests that under certain circumstances these structures can be an option for deploying microwave backhaul for small cell.
The installation of any equipment on existing poles—including small cell and backhaul radios and antennas—will necessarily change the weight and wind loading characteristics of the deployment pole. This will require a structural analysis to verify if the existing pole still meets the standards or the commercial criteria set by the pole manufacturer. For more information on Aviat’s analysis of pole sway for small cell backhaul see our PDF.
Eduardo Sanchez
Marketing Engineering Specialist
Aviat Networks
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October 5, 2012
Developments in Fixed Link Spectrum Access in Ireland
Spectrum (Photo credit: Free Press Pics)
In response to the ever-growing demand for spectrum to satisfy the increase in usage of data hungry mobile applications and in line with recently published ECC recommendations, ComReg (i.e., Ireland’s telecom regulator) issued a consultation document looking at the future demands on spectrum for point-to-point fixed links. September saw the publication of the conclusions and subsequent decisions arising from that consultation, to which Aviat Networks was the only manufacturer to respond. This blog highlights some of those decisions:
New Spectrum
One of the major topics was the requirement for more spectrum allocated for point-to-point usage. Consequently, ComReg has made the following announcements:
- ComReg intends to open the frequency bands below, as there is a significant demand for fixed links services in the 28 GHz, 31 GHz and 40 GHz band:
- The 32 GHz band may be made available for fixed links services at a later stage subject to its potential for future PP/PMP use and the demand on spectrum for PP use in the 31 GHz (31.0 – 31.3 GHz paired with 31.5 – 31.8 GHz) band
- Within the 28 GHz band, as per REC T/R 13-02 Annex C, the following frequency ranges will be made available for fixed links services: 27.9405 – 28.4445 GHz and 28.9485 – 29.4525 GHz
- Frequency bands 28 (27.5 – 29.5) GHz, 31 (31.0 – 31.3 paired with 31.5 – 31.8) GHz, 32 (31.8 – 33.4) GHz and 40 (40.5 – 43.5) GHz will not be opened for PMP use in the current spectrum strategy period 2011 – 2013
Aviat Networks supported this initiative during the consultation process and is pleased to see ComReg make these announcements as a move to satisfy the increasing demand for microwave spectrum. Specifically, frequencies in the range of 28 to 42 GHz are ideal for short-haul urban links, and we expect the decision by ComReg to stimulate further growth of microwave for fixed line and mobile network applications.
Technical Changes
- High-Low search radii for the 23 GHz and 26 GHz bands will be reduced from 200 meters to 100 meters. The consensus of current licensees operating within the 23 GHz and 26 GHz bands is that the reduced radius will improve spectrum planning and reuse, which will improve spectral efficiency
- There will be no distinction between rural and urban areas concerning the High-Low search radius
- Antenna size will be limited to 0.6 meters in the 23 GHz and 26 GHz bands
- ComReg will allow use of 56 MHz channels in the 26 GHz band only where the licensee has a National Block license containing contiguous blocks of spectrum
- ComReg will permit the use of higher bandwidths, as shown in the table below, to facilitate the increase in mobile data demand:
Block Licensing
ComReg signalled its intention to potentially reopen the 26 GHz block license scheme for a further round of National Block assignments, subject to market demand. In the past, Aviat Networks commented that it believes block licensing is not the most appropriate method of licensing in the microwave bands. However, ComReg disagrees with that view.
Summary
The combined expansion in spectrum use—new bands and larger channel allocations—underlines the popularity and ongoing viability of microwave as an alternative to fiber in urban networks experiencing rapid traffic growth and geographic expansion.
Aviat Networks welcomes the ComReg announcement. We already address all the band/channel assignments made by ComReg.
Ian Marshall
Regulatory Manager
Aviat Networks
Related articles
- FCC Chair Proposes to Repurpose WCS Band for 4G (phonescoop.com)
- Wireless Regulators Move to Prevent Spectrum Waste (aviatnetworks.com)
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- FCC: More Backhaul at 6, 11 and 23 GHz (dailywireless.org)
- FCC’s Genachowski: We’re on track to free up 300 MHz of spectrum by 2015 (fiercewireless.com)
September 28, 2012
Simplifying Carrier Ethernet Networks Scalability and Operations
As symbolized at the recent EANTC interoperability testing event, Aviat microwave radios can help solve the complexity and scalability problems of Carrier Ethernet technology.
Carrier Ethernet (CE) transport networks are growing in both scale and complexity, requiring both vendors and operators to deliver solutions to sustain their growth. To help address this, Aviat Networks recently participated in the European Advanced Networking Testing Center’s (EANTC) annual multi-vendor interoperability testing event to validate several aspects of scaling CE networks, among other things.
Increasing CE network sizes increase the complexity of management—especially from a services perspective—when CE services span multiple network domains. The ability to partition management domains and effectively manage alarms that accurately identify and propagate notification of network faults, dramatically speeds up the fault isolation and resolution process across large networks. Utilizing and effectively implementing “Hierarchical Service OAM” in growing CE networks is valuable to overcoming this challenge and was a key area of the recent interoperability testing.
Another critical aspect of growth is dealing with multi-technology—not just multi-vendor—interoperability. As CE networks scale, there is an increasing mix of Ethernet switching, MPLS and, most recently, MPLS-TP internetworking emerging. One potentially complex area that was also tested was validating the operation and survivability of intersecting Ethernet and MPLS-TP rings in a multi-homed topology. The “ERPSv2 and VPLS Interworking” test validated that standards-based G.8032 Ethernet protected rings and MPLS-TP VPLS rings can interoperate, or more significantly “co-operate,” to allow complex multi-technology networks to deliver reliable end-to-end services.
To learn about these aspects of scaling and dealing with complex CE networks check out the EANTC white paper for more details.
Errol Binda
Sr. Product and Solutions Marketing Manager
Aviat Networks
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August 17, 2012
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
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.
Ian Marshall
Regulatory Manager
Aviat Networks
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May 29, 2012
The Modulation Arms Race: A Case of Diminishing Returns
A standard Quadrature Amplitude Modulation constellation (non-gray code) diagram showing a demonstrative 4-bit binary code pattern. (Phase offset and amplitude values may not represent those used in real life) (Photo credit: Chris Watts via Wikipedia)
There’s a new arms race in the microwave industry, and it’s over who can claim support for the highest QAM level. Now two vendors are out in the market fighting it out over who had 2048QAM first, yet go back a little more than 12 months and 512 or 1024QAM had barely hit the market. We even are seeing mentions of 4096QAM in some conference presentations. We here at Aviat Networks view these advances as a good thing for our industry, but this heavy marketing of 2048QAM does no one any favors, as it focuses purely on only one aspect of high modulations—capacity—and ignores several other aspects that need to be understood, namely:
- Capacity improvement diminishes with every higher modulation step
- High modulations come with much lower radio system performance—requires shorter hops and/or larger antennas
- High modulations are much more sensitive to interference—makes link coordination difficult (if not impossible)
- High modulations need higher Tx power, increased phase noise and linearity—increases radio design complexity cost
So as with most things that are presented as a cureall, higher order modulations are a useful tool to help operators address their growing backhaul capacity needs, but the catch is in the fine print. Operators will need to look at all the tools at their disposal, of which 1024/2048QAM is a useful option, albeit one that will require very careful planning and strategic deployment. In general, operators need practical solutions for capacity increases, as detailed in “Improving Microwave Capacity“. In fact, speaking of practicalities, the real challenges with LTE backhaul has very little to do with capacity…as detailed by this article. For the complete “Modulations Arms Race” article, click here.
Stuart Little
Director, Corporate Marketing
Aviat Networks
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March 23, 2012
10 Things to Know About the Status of Asymmetrical Wireless Backhaul
The ECC held a meeting in March to further consider updating regulations to allow the use of asymmetrical links in microwave backhaul (Photo credit: blese via flickr)
Last autumn we wrote about potential plans from a microwave competitor regarding using asymmetric band plans for point to point microwave communication links. To update this topic, we have put 10 things in parentheses that you should know about the current status of asymmetrical links in wireless backhaul. Last month at an Electronic Communications Committee SE19 (Spectrum Engineering) meeting this microwave technology subject was discussed again. (1) The proposal under consideration has been reduced in scope and (2) the regulators present still wish to see more evidence regarding the need for change before agreeing to such significant amendments.
Asymmetric Band Plan Altered
A quick reminder of what was originally requested back in the autumn of 2011; a move from channel sizes of 7, 14, 28 and 56MHz to channel sizes of 7, 14, 21, 28, 35, 42, 49 and 56MHz in order to support different granularities of channel widths in all bands from L6GHz to 42GHz. However in March these proposals were altered to reflect channel sizes of 7, 14, 28 and 56MHz (i.e., no change to existing channel sizes) and asymmetric only in the 18GHz band and above.
The national regulatory authorities stated that even the (3) revised proposal cannot be accommodated with existing planning tools so they cannot imagine asymmetric links being deployed alongside existing links in their countries. A few stated that in block allocated spectrum the owner of the spectrum may be able to implement this channelization, but Aviat Networks believes that (4) the complexity of coordinating links even in block allocated spectrum should not be underestimated.
Saving Spectrum?
Traditionally, links are planned on an equal bandwidth basis, e.g., 28MHz + 28MHz, with a constant T/R spacing throughout the band in question. This new proposal would see links of 28MHz + 7MHz and furthermore makes the claim that spectrum would be saved. Numerically speaking this arrangement would save 21MHz for each pair, but (5) saved spectrum is only of value if it is reused. In many cases the “saved” spectrum would be orphaned due to difficulties coordinating it into usable pairs.
Asymmetric Channel Plan Limits Future
In our last blog on this topic we reflected on the fact that while there is some level of asymmetry today, (6) this trend may well be balanced in the near future by cloud services and other services that involve the user uploading content. We believe that (7) committing to an asymmetric channel plan now limits the future. (8) Symmetric channel planning allows networks to dynamically adjust to changing demands. A related concern is the fact that (9) spectrum once reallocated may not be easily clawed back to create symmetric pairs in the future. While some applications are experiencing asymmetry in traffic presently, we should not forget that some traffic patterns are still symmetric and where asymmetry is a feature, (10) the scale of this phenomenon may be overstated. Indeed, a major European operator present at the SE19 meeting voiced skepticism about the need for asymmetric support.
What do you think? Will mobile traffic remain or increasingly become asymmetric? Are asymmetric microwave links needed or can they be practically deployed in existing bands? Answer our poll below and tell us. Select all answers that apply.
Ian Marshall
Regulatory Manager
Aviat Networks
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July 1, 2011
Antennas: Why Size is Important for This Wireless Equipment
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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June 10, 2011
TDD or FDD Wireless: That is the Question!
TDD, or Time Division Duplex, where a single radio channel is used to send and receive data, has been a common technique employed in unlicensed microwave transmission bands, such as 2.4 and 5.8GHz. The advantage of TDD is a simplified and lower cost design, often based upon 802.11 standards. In contrast, FDD, or Frequency Division Duplex, where data is transmitted in one frequency channel and received in another (separated by anywhere from less than 100 to more than 1,000 MHz) has been the staple of licensed frequency bands between 2 and 38 GHz worldwide.
Now, a number of the CEPT recommendations for the new point to point bands over 40GHz contain provisions for TDD operation. TDD is accommodated either as an alternative band plan or a mixed TDD/FDD band plan, in addition to the more common FDD band plan. However, CEPT recommendations are only just that—recommendations. How these bands will be implemented in each country will be determined by the individual national regulatory authority.
Recently, we asked a number of European national regulators about if and how they would introduce TDD operation in these new bands. The general response was that they were not opposed to the introduction of TDD in principle, and that such operation would have to be worked into existing or revised band plans. One complication raised was that spectrum would have to be reserved for guard bands between TDD and FDD segments within the same band. Regulators usually try to avoid having to waste valuable spectrum in this way. Also, once a band plan is established and the spectrum allocated to users, efforts to introduce TDD operation at a later date is extremely difficult.
Some regulators have already issued new national band plans at 42GHz and above, and to date none of these allow for TDD operation. Furthermore, for countries that have allocated new bands through spectrum auction, there we see the usual FDD style symmetric band approach.
Despite the appeal of TDD operation from a cost perspective, early indications are that although provision for TDD operation is being made in these higher bands, practical complications and concerns over maximizing the use of new bands may prevent its widespread introduction.
What are your thoughts on using TDD more in national band plans? Leave a comment, if you’d please.
Ian Marshall
Regulatory Manager, Aviat Networks
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