“[S]tatistics can lie. But cast as ‘studies’ by commentors, they take on the weight that a decision maker chooses to make of them.”

– Daniel Brenner

As a follow-on to its National Broadband Plan, the FCC last year released a Technical Paper intended to validate the Plan’s prediction of a 300 MHz mobile-broadband spectrum deficit by 2014. The Paper describes a spectrum requirements model that totals current spectrum assigned to mobile broadband and applies a multiplier based on expected demand, taking into account expected increased tower density and improvements in air-interface spectrum efficiency. The model’s result is a predicted deficit of 275 MHz in 2014, which rounds to 300 MHz. On the way toward that result, however, the analysis uses just a few of the available data forecasts, ignores offloading of macrocell data to Wi-Fi and femtocells, and assumes the continuation of flat-rate plans for consumers. Some of these oddities I noted in a post at the time. I had hoped the FCC would make the Paper a subject of public comment. That hasn’t happened. So, I’ve looked at the Paper in more detail. I find that when looking at the above factors in a more realistic manner, predicted spectrum requirements go down significantly.

INVALID ASSUMPTION #1: THREE ARBITRARILY-PICKED FORECASTS ARE REPRESENTATIVE

To estimate spectrum requirements in 2014, the FCC’s model uses a multiplier based on an average of three forecasts of mobile-broadband data demand. These are by Cisco, Coda Research, and Yankee Group. From 2009 to 2014, they predict mobile broadband data growth of 4722%, 3464%, and 2332%, respectively, for an average of 3506% (or, if you prefer, 35x).

The FCC characterizes these as “industry analyst mobile data demand forecasts” when in fact only two are from industry analysts. Cisco is an equipment vendor. The preparation of its forecast is managed by a member of Cisco’s marketing team. The Cisco forecast is used to promote the sale of Cisco’s core-network hardware that can be used to help address the increased data demand the forecast predicts. The Technical Paper gives no indication as to why these three forecasts were chosen and others rejected. It would be as if the FDA looked at clinical trial data, ignored the statistics, and made decisions based on its favorite data points.

The decision to use Cisco’s forecast, and not those of other equipment vendors, is odd. Forecasts are also available from Alcatel-Lucent, Ericsson, and Nokia Siemens Networks (NSN), among others. Unlike Cisco, these companies have core competency in the 3G/4G radio air-interface that is the most challenging bottleneck when it comes to mobile capacity, so it would seem useful to include their findings. For the same time frame looked at by the FCC, 2009-2014, Alcatel-Lucent, Ericsson, and NSN predict data growth of 3893%, 2541%, and 811%, respectively. The 811% looks very low, but is consistent with recent forecasts predicting data increases in the 8x-10x range over the next several years; these lower estimates may be an indication of large-cell model of cellular hitting an inflection on a technology-maturation S-curve.

When the forecasts are considered with those of Cisco, Coda Research, and Yankee Group, the six-forecast average is 2961%, or 15.5% less than the FCC’s estimate of 3506%. What does this do to spectrum requirements? From the FCC’s own sensitivity analysis in the Paper (p. 22), this reduces the 2014 shortfall from 275 MHz to approximately 165 MHz.

INVALID ASSUMPTION #2: OFFLOADING IS AN ABSTRACT CONCEPT

Today’s typical macrocell (large cell) wireless systems have always expended disproportional resources trying to overcome building attenuation and reach user devices indoors; it’s been an outside-in approach. Adding to the challenge, we’re inside 70% of the time, and will be inside even more as time goes on, according to Informa estimates. Building attenuation is not the only indoor problem; signals indoors weaken as the distance to base stations increases. Furthermore, capacity available to a user goes down as more users join the cell.

At the same time, our indoors increasingly have fixed broadband service. This can be used in conjunction with small cells, such as Wi-Fi access points or femtocells, to offload data from the macrocell. When the user is close to small cells, a lot of good things happen, things beyond the ability of additional spectrum to provide. Building attenuation goes down because we’re not punching through as many walls. Signal strength increases because of the shorter distance. Throughput to the user goes up because capacity is no longer shared with several dozen others. (Throughput to those still on macrocells goes up, too, because they’re no longer competing with the small cell users.) As an added benefit, since the user is close to the cell, not as much power is needed on the uplink; handset transmit power goes down, increasing battery life. Taking all these factors into account, data rates available to a user can go up 80x or more using small cells depending on the deployment scenario.  In contrast, doubling available spectrum increases throughput only 2x. Allocating the entire 300-3000 MHz band to mobile broadband would increase throughput only 7x, were that a practical option.

The outside-in approach of macrocells is turning inside-out, bring the user closer to the base station. This offloading concept is consistent with the ITU’s 2003 vision of heterogeneous networks; each wireless access technology excels in certain circumstances, and shouldn’t be force-fit into others. It’s hopeless to reach the capacity increases that can be achieved through small cells by the use of additional spectrum. Qualcomm, a longtime advocate of more spectrum for mobile broadband, recently said that “the next performance and capacity leap will come from network topology evolution by using a mix of macro cells and small cells – also referred to as a Heterogeneous Network (HetNet) – effectively bringing the network closer to the user.” The same improvements in electronics technology that enable smartphones, and their increased data requirements, likewise enable new small-cell technology that can address the demand. Wireless innovation is not only on the user-device side.

Despite this progress in small cells, the Technical Paper inexplicably dismisses offloading:

“Since this paper is focused on mobile data traffic, strategies to offload traffic to femto-cells and WiFi is [sic] not directly considered. In addition, the rollout of such network architecture strategies has been slow to date, and its effects are unclear.”

First, mobile broadband data traffic and offloading go hand in hand and thus must be considered; the more data offloaded, the less carried by the mobile broadband network, and the less spectrum required for that network. Second, offloading strategies are ramping up quickly. The “effects” are clear. Less data is carried on the macrocell, reducing the need for new spectrum.

If the Technical Paper does not directly consider the effects of offloading, perhaps the input forecasts from Yankee Group, Coda, and Cisco do. It’s not clear, from information provided in the Paper, to what extent the three forecasts take offloading into account. Looking at the Cisco forecast separately, we can see it estimates that in 2014, 23% of wireless data in the U.S. will be offloaded to Wi-Fi and femtocells. More recent observations and forecasts, however, are substantially higher than Cisco’s. Commenting on the issue in its latest wireless competition report, the FCC said “AT&T has experienced significant growth in hot spot usage in the first half of 2010, with an estimated 40 percent of iPhone traffic in the United States being transmitted over a Wi-Fi connection.” Independent analysts ABI Research and Juniper Research predict worldwide offloading rates of 48% and 63%, respectively, in 2015. ComScore estimates that in August 2011, 37.2% of mobile phone data was sent using a WiFi connection, a percentage that grew almost 3 points in just the preceding three months.  For 2014, Juniper Research predicts North American offloading will reach 76.9%. Cisco’s underestimation of offloading contributes to its forecast usually being the highest of the bunch, making it the go-to forecast for spectrum crisis adherents.

The FCC didn’t directly consider offloading, but we can. For the purposes of this post, let’s average the low and high offload estimates, from Cisco and Juniper Research. That gives us 50% as an offload factor. Adjusting Cisco’s forecast using the 50% offload factor instead of 23%, one gets a Cisco 2014 data growth relative to 2009 of 3066%. This lowers the six-forecast average to 2685%, which is 23.4% less than the FCC’s estimate. Returning to the sensitivity analysis, the revised spectrum shortfall is approximately 115 MHz instead of 275 MHz.

INVALID ASSUMPTION #3 – FLAT-RATES RULE

Most U.S. operators have gone from flat-rate “all you can eat” rate plans to usage-based plans where the consumer is charged based on the amount of data used. AT&T made the change in June 2010, T-Mobile in April 2011, and Verizon Wireless in July 2011. (Sprint is the only major operator with an unlimited plan today, on its 3G network for the iPhone.) These new rate plans will further encourage users to offload data. The Technical Paper, again inexplicably, does not take this into account:

“The projections of mobile data demand used in this analysis are based in part on historic market dynamics, such as “all you can eat” pricing for data. The effect of new pricing strategies on consumer data demand is not yet known, but has the potential to impact data traffic projections if widely adopted in the market.”

I expect the effect of these new pricing strategies will be that consumers moderate their less essential use of mobile broadband. This will be especially so for the data hogs, a few of whom consume the bulk of mobile broadband data in each cell. There is not much public information yet on consumer response to these new pricing plans, but it’s something to watch out for, and then we can make a further correction to the spectrum deficit estimate.

The effects of usage based plans on data consumption will be far reaching. With the cost of bits more aligned with what it costs the operator to supply them, the consumer has more price signals on which to act upon. These signals, in turn, will be felt by the rest of the wireless ecosystem. Under flat-rate plans there was little incentive for consumers to be conscious about how efficiently-coded the phone’s operating system or applications were. Under newer plans that charge by use, consumers will have a heightened awareness of how much data they’re using, and for what purpose. Software will increasingly compete on efficiency. On the application side, operators know where every bit goes, and which applications consume the most data. There is no such awareness on the consumer side. Perhaps the industry will provide greater granularity in data metering, to the application level, so users can better prioritize usage of their data plans. Once this happens, developer sensitization to the issue will increase.

Some of this software-based improvement is nearly “free,” requiring only improved programming practices. Last year, the World Wide Web Consortium adopted a recommendation for best practices in mobile web application development.  As one example in the recommendation, mobile web applications often use several static images to represent buttons. Each image that is sent uses a separate HTML request. HTML requests can be reduced to one by combining the buttons into one static image, sending that image, and cutting the buttons from the image. That saves data. Under flat-rate plans, why bother?

On the operating system side, different phones can vary greatly as to the amount of data needed to perform the same function. One analysis, sponsored in part by Research in Motion, finds that across multiple applications and for the particular smartphones studied, the BlackBerry used much less data than the iPhone or Android phones. For web browsing, the Blackberry was 2.1 times more efficient (i.e., used 2.1 times less data) than iPhone iOS or Android. For e-mail, the Blackberry was 4.5 times more efficient than Android and 11.4 times more efficient than iPhone iOS. As users become more aware of what data they’re getting for their money, competitive pressures will lead the less efficient operating systems to become more so.

FURTHER ADJUSTMENTS TO THE ESTIMATED SPECTRUM DEFICIT

We’ve looked at the estimated spectrum deficit from the basis of demand and the FCC’s model. Before we finish, let’s take a quick look at where we are today on the supply side. The following efforts show promise for making more spectrum available for mobile broadband within the 2014 timeframe:

• LightSquared is seeking approval to use 40 MHz of spectrum near 1500 MHz for terrestrial mobile broadband. Such use is pending resolution of GPS interference issues.

• The FCC has an open proceeding looking at maximizing the mobile broadband potential of a total 75 MHz of spectrum around 2 GHz. Some 40 MHz of that belongs to Dish Network, which recently asked the FCC for permission to deploy a hybrid satellite and terrestrial mobile and fixed broadband network. Qualcomm, Dish, and others have various smaller pieces of the 700 MHz band, which might be practical for use with LTE in a TDD mode using unpaired spectrum.

• NTIA has issued a plan and timetable identifying over 2200 MHz of Federal and non-Federal spectrum that might provide opportunities for wireless broadband use.For mobile use, the most promising band in the near term is 1755-1850 MHz. NTIA is finishing a detailed review of the band to determine to what extent it can be made available for commercial broadband use. The review was supposed to be completed by September 30, 2011 but is running late; perhaps we’ll see the results by the end of the year. I hoping at least 40-50 MHz becomes available from this band.

An accurate and current inventory of frequency assignments and usage would help identify new mobile spectrum, but such an inventory doesn’t exist. The preliminary steps the FCC has taken so far are so laden with disclaimers they can’t be relied upon. On the Federal side, the Government Accountability office (GAO) recently reported that “NTIA’s data management system lacks transparency and data validation processes,  making it uncertain if spectrum management decisions are based on accurate and complete data.” The U.S. should conduct a thorough spectrum inventory, informed by measurements.

CLOSING THOUGHTS

We’ve seen that reasonable updating of the FCC’s spectrum deficit model significantly reduces the short-term forecast deficit for 2014. As adjusted, the Technical Paper doesn’t support the National Broadband Plan’s mobile broadband spectrum recommendations, as was its intent.

We might step back and ask why the FCC is forecasting spectrum demand at all. If the U.S. moves more toward a property-rights and marketplace regime for spectrum use, as it may with the incentive auction approach, the Technical Paper estimates and National Broadband Plan recommendations become less important as the market will tend to allocate spectrum resources efficiently. To the extent it does not, and fails to meet a public policy goal, policymakers can change the market outcome.

If a forecast is to be maintained, the FCC should reconcile the National Broadband Plan with an updated forecast spectrum deficit, openly prepared with broad input and using the latest data. Part of that examination should be the validity of other methodology used the Technical Paper. The work should be thorough enough that the FCC Chairman no longer feels the need to cite Cisco’s forecast in speeches, and can instead cite the work of the FCC’s own staff — with authority.

A 3G feature phone on Verizon’s network uses about 1.25 MHz of spectrum. Using the above multipliers, a smartphone would need 30 MHz and a tablet 150 MHz, more than the total spectrum inventory of some carriers. In reality, smartphones and tablets use the same 1.25 MHz. What’s going on?

I assume the numbers Mobile Future cites come from the latest Cisco forecast (p7), but those are for increases in data traffic, not spectrum. Mobile Future seemingly equates the two, but they’re different. Data traffic increases with smartphones and tablets, but that data takes up capacity in existing spectrum. At some point, that spectrum runs out of capacity. More spectrum, along with other techniques, can be used to add capacity.

I sense the hand of a PR firm in this, which means it wasn’t cheap. Fortunately, the error seems confined to the voiceover, which can be redone relatively easily. To be breezy about it, for the sake of a two-minute video, the revised message might be that spectrum capacity is limited, smartphones and tablets use much more, when we run low performance suffers, more spectrum adds capacity improving performance.

Wireless service rationing? Millions of new jobs? Hey, it’s an advocacy video. I’d be very pleased if this video drew more attention to spectrum issues, and did not contribute to the myths.

NAB – Shortages of Capacity, Not Spectrum

The NAB report is prepared by Uzoma Onyeije, a consultant who was once Broadband Legal Advisor to the Chief of the FCC’s Wireless Telecommunications Bureau. The main claims are that there is no need for an urgent and massive reallocation of spectrum, that there are numerous alternatives to spectrum that can boost network capacity, and that sources of spectrum other than TV are more readily available.

It starts by noting there wasn’t a “spectrum crisis” until the American Recovery and Reinvestment Act of 2009, which required the FCC to promote broadband access. The National Broadband Plan followed calling for 500 MHz of spectrum to be made available for broadband within 10 years, with 300 MHz of that for mobile within five years, and 120 MHz of that to come from television broadcasting. Seven months after concluding that 300 MHz was needed in the short term, the FCC released a Technical Paper intended to support the 300 MHz figure. In November I wrote on that Paper, pointing out several factors not considered that, had they been, would have acted to reduce the estimate of short-term spectrum requirements. Later, I questioned the appropriateness of the FCC relying on a forecast prepared by the marketing department of an equipment vendor, without critically and openly examining the assumptions that went into the forecast. Onyeije shares some of the concerns I had, and still do, with that Paper.

I expect the American Recovery and Reinvestment Act turned some spectrum wants into needs, but by all accounts mobile network data volumes are increasing significantly, fed by a volatile mixture of old flat-rate plans and new bandwidth-hungry devices, though the growth rate of those data volumes is decreasing. Getting additional spectrum is a natural option to consider for more capacity. Onyeije provides a list of non-spectrum options. Some have been mentioned here before – offloading to Wi-Fi and other technologies, adjusting rate plans so largest data users pay more, tighter software coding of applications and operating systems. I don’t think I’ve discussed channel bonding, which is a technique that uses non-contiguous spectrum – combining a sliver here and a sliver there. Support for this will be appearing in LTE-Advanced, going on the air in a few years. Backhaul is also something I haven’t focused on; how much of the current spectrum crunch is really due to backhaul bottlenecks?

Another capacity-increasing technique mentioned is sectorization – changing a non-directional transmission system to a directional one using two or more sectors at the same cell site. In the most congested urban areas in the US, antenna systems are generally configured with three sectors, with each sector 120 degrees wide. You don’t see many six-sector configurations, in which each sector is 60 degrees wide. Theoretically, that doubles capacity from the same tower. A long time ago there was more activity in six-sector antenna systems, but the sense then was it wasn’t too practical; you might end up with just a 70% capacity increase because of real-world issues such as imperfect antenna patterns. It was hard to justify the expense. These days, however, with better transmission technology, it should be looked at again. I note SK Telecom in Korea is deploying 500 six-sector sites, after good results with 20 test sites.

Onyeije looks at the spectrum warehousing issue. If an operator has spectrum that isn’t being used, but is on track to build it out, I’m fine if it is fallow for a year or so. Maybe longer if the delay is to wait for much more efficient transmission technology that is on track in the standards process. If it is just sitting there with no build-out requirement and no prospect for utilization, I’d think the operator’s investors would create pressure to sell it. If a spectrum holder has “no plans to sell, lease or use” its spectrum, to quote one in Onyeije’s report, I’m more concerned.

Aside from the warehousing issue, Onyeije identifies a few bands that have been languishing at the FCC for years and makes the point that, since they have been idle for so long, the spectrum crisis must not be so great. These are the AWS-3 spectrum at 2155-2175 MHz, H block spectrum at 1915-1920 MHz and 1995-2000 MHz and J block spectrum at 2020-2025 MHz and 2175-2180 MHz, 700 MHz D block at 758-763 MHz and 788-793 MHz. What’s the story there?

Onyeije suggests mandatory receiver standards. Receivers are already very good in mobile broadband because of vendor competition and the need to operate in a congested environment. Receiver design is proprietary and an important source of differentiation among vendors. I’d think continued improvement of receiver performance in the marketplace, in the long run, would achieve greater capacity benefit than imposed government standards.

The report calls on the FCC to complete and publicly release a comprehensive spectrum inventory, along the lines of the Snowe-Kerry RADIOS Act, which includes measurements. The FCC has made available several spectrum tools online, including LicenseView and the Spectrum Dashboard, which it says is its inventory. According to their disclaimers however, LicenseView “is not intended for analysis of spectrum utilization or spectrum holdings of licensees” and “the FCC makes no representations regarding the accuracy or completeness of the information maintained in the Spectrum Dashboard.” Regarding federal spectrum, I’d add that an inventory becomes more important in light of GAO’s report on NTIA processes that said “NTIA cannot ensure that spectrum is being used efficiently by federal agencies” in part because “NTIA’s data collection processes lack accuracy controls and do not provide assurance that data are being accurately reported by agencies.” Thus, “it is unclear whether important decisions regarding current and future spectrum needs are based on reliable data.”

CTIA , CEA, and WCAI dismiss the NAB report, saying it’s a stalling tactic and they know these things already. One of Onyeije’s points, however, is that it’s the Commission that needs to know these things, and fully investigate and quantify the impact of all capacity-generating alternatives. It has not. It tried with the Technical Report, but inadequately.

CTIA Establishes the Efficient Properties of Cellularization

The CTIA report is intended to demonstrate that US mobile wireless providers are “extremely efficient” in their use of spectrum. The report was prepared by Peter Rysavy, a consultant known in wireless circles for his series of technical reports, with many pertaining to spectrum, air-interface, and mobile device issues.

This report seems to be a response to an NAB claim, some time back, that broadcasting is a more efficient user of spectrum than wireless. I presume NAB’s claim is based on broadcasters’ DTV system transmitting about 19 Mbps in a 6 MHz bandwidth, while the wireless operators are sending about 10 Mbps in 10 MHz bandwidth. (So, TV has more bits per Hertz.) This is kind of an apples and oranges comparison, but the comparison has been made and we have this report in response. Having spent a lot of time in 3G and 4G standards battles, I have no doubt that those participating are trying wring out all the efficiency that is both possible and practical. Wireless standards groups sweat to get another tenth of a dB improvement. Of course, part of efficiency is an implementation issue and not covered by standards. I agree cellular services are more efficient at delivering unicast traffic. Broadcasters, however, can be more efficient in another way. The efficiency debate occurs in part because we have not agreed on a definition of efficiency. More on this below.

The CTIA paper starts with a section on spectral efficiency. It discusses its fundamental measures and technologies that have been used to continually improve it, including adaptive modulation and coding. (Rysavy says his list of technologies is not exhaustive, but to his list I’d add Hybrid Automatic Repeat Request as a key enabler.)

Rysavy observes that the industry’s technologies are operating close to the Shannon Bound, the theoretical limit on the spectrum efficiency that can be had for a given signal-to-noise ratio. Capacity improvements thus must come from advanced antenna techniques (such as MIMO) and topology evolution (e.g., adding picocells to a macrocell).

The report is hopeful on the prospects for Wi-Fi and femtocells to relieve traffic on the macro-cellular network. I’m somewhat more cautious on the potential of femtocells to relieve the capacity crunch.  For various reasons, including interference management, what I think may happen with femtocells is that they get pulled out of the home and put up in neighborhoods using existing structures for support. (The more-favorable pole-attachment rules recently adopted by the FCC are timely.) There are many small-cell trials underway but I haven’t seen much in the way of results.

Network evolution is discussed in a larger sense, focusing on developments in heterogeneous networks, but Rysavy says that’s not enough and that more spectrum is needed, too.

Back to the efficiency issue, the efficiency of cellular systems is compared to that of broadcast television. The point made is that if you take many small cells and place them within a larger area  covered by one transmitter (e.g., one for TV), the cellular system can deliver many times the unique bits in that area. This is true, if that is the definition of efficiency. Let’s look at it another way and compare the maximum number of users served by each scheme. As a best-case scenario, assume the cellular users are using a low-bit-rate application such as LTE VoIP. In 10 MHz we can support about 400 users. That times 3 sectors is 1,200 users per cell. That times 30 cells (as per the example in the paper) is 36,000 users that can be supported at once. In contrast, a TV  station covering the same area can support an unlimited number of users, albeit one-way, since it isn’t limited by uplink capacity nor MAC addresses. Is it a fair comparison? No. One is broadcasting and the other is cellular. Can’t cellular broadcast also? Yes, but to the extent it does the unique-bits argument becomes weaker. We can go around and around. The television example is used, along with other analysis in that section, in an attempt to persuade the reader that “cellular architectures represent a configuration that is capable of providing tremendous service capacity to its users.” I’m convinced, but I was before reading the report.

Rysavy depicts how voice minutes, message volume, and data volume have increased on cellular networks over the years. Yesm growth has been dramatic, but the growth rate is slowing.

Epilogue

Concurrent with this debate, ATSC is in the early stages of planning and developing the second DTV standard to replace the current one that’s been around for about 15 years. LTE specifications support broadcasting, which can be done in a cellular manner on the same frequency. Transmissions are synchronized so the terminal can combine energy from multiple sites. The broadcasters looked at cellularization a year ago assuming use of the current ATSC DTV standard, and rightly found it was not practical. It just wasn’t designed for that purpose. With the new LTE standards, it’s time to look at TV cellularization again but with LTE as a core technology. There could be a return path, inexpensive chips for receivers, and it might  be able to be done in less than 100 MHz, making over 200 MHz available for auction. With DTV, the broadcasters found significant deployment and operating costs with cellularization, but with LTE infrastructure would be shared; it remains to be determined if it’s a business. The technology is there; it just has to be architected by broadcasters and infrastructure vendors into suitable form.

UPDATE 5/20/2011

The FCC issued a Public Notice today seeking comment on using the 2 GHz bands identified as “languishing” by NAB. Some are listed above. 75 MHz total.

There is overlap between the people who prepare the forecast and the people responsible for marketing Cisco’s line of core-network hardware to service providers. The forecast is used to help sell that hardware. Put simply, it’s a sales brochure. For business purposes, that’s fine. We look at marketing materials all the time, get useful information from them, consider the source, and make a decision. In spectrum policy, we’re not doing that. We’re taking Cisco’s claims as-is, and not considering how the company’s interest in selling hardware might influence its forecast, let alone critically and openly examining the assumptions that go into the forecast.

The Commission should rely more heavily on two forecasts in its possession that, unlike Cisco’s, are independently prepared. One is by Yankee Group and the other is by Coda – both independent research firms. These two forecasts are cited, along with Cisco’s, in the FCC’s October 2010 Technical Paper, Mobile Broadband:  The Benefits Of Additional Spectrum. A chart from the report comparing three forecasts is shown below.

As with any sales pitch, whenever you hear a spectrum claim, consider the source.

The methodology described in the paper is relatively straightforward and pragmatic, in contrast to methodologies used by other spectrum estimates cited in the NBP. The paper looks at current spectrum use and adjusts it upward based on forecasts of mobile data demand, downward based on air-interface spectral-efficiency improvements, and downward based on increased cell-site density. With such an approach, the demand forecasts are critical. Forecasts from Cisco Systems, Coda Research, and Yankee Group are used and averaged to get a single forecast.

Related to the 300 MHz estimate, directly or indirectly, are the three items the FCC has placed on the tentative agenda for its November 30 meeting: TV spectrum innovation, opportunistic spectrum use, and experimental licensing rules. Perhaps as part of one of these proceedings, the FCC will seek comment on the paper and the three forecasts. Here are some areas for consideration:

• Rate plans. The paper says, “projections of mobile data demand used in this analysis are based in part on historic market dynamics, such as ‘all you can eat’ pricing for data.” There is anecdotal evidence, however, of movement toward “pay as you go” pricing.
• Offloading of mobile broadband data onto Wi-Fi and other technologies. The paper chooses to not consider such offloading “directly.” Certain of the forecasts consider it, but incompletely, at least from what I can tell (see the last point below). As we see improvements in, and deployment of, interworking technologies for Wi-Fi and 4G, and perhaps more rationalization of rate plans away from “all you can eat” single flat rates, consumers will have more incentive to offload mobile broadband data. A reference cited by the paper downplays this effect by saying that a mobile user is often not near a Wi-Fi hotspot. The Cisco forecast, however, cites data showing that most mobile broadband use is at home or at work — locations increasingly having hotspot coverage.
• Scenarios for mobile broadband video use. Cisco predicts that video will account for 66% of mobile data traffic by 2014. It also predicts that in 2014, smartphones will use 21% of mobile data traffic and “laptops and other mobile ready portables” will use 70%. Looked at another way, video on laptops and portables is predicted to consume almost half of mobile broadband data. If we reconsider offloading of data and rate plans, estimates of mobile broadband video use can likewise be reconsidered.
• New technology. The paper looks at improvements in technology and the resulting increased spectral efficiency with respect to the air interface. Other technologies have the potential to reduce the number of bits needed to do the same thing. For example, video and audio compression technology continues to improve. What practical advances can be realized and when? Related to new technology, I’d also include software improvements resulting in reduced application data requirements and phone operating system overhead. If the industry is moving toward “pay as you go,” programmers will have greater incentive to reduce unnecessary data overhead.
• Use of non-public data. Many references cited by the paper or in the forecasts are described as proprietary or unpublished or are accessible only at considerable cost. Perhaps the FCC can encourage these sources to make more data publicly available.

There’s more that could be said about the technical paper and the three forecasts, but the above points are the first considerations that come to mind.

As background, the National Broadband Plan recommends repurposing 120 MHz of from the TV bands to mobile broadband. On June 14 the FCC released an Omnibus Broadband Team Technical Paper that describes some of the analyses supporting this repurposing. Chairman Genachowski asked the Commission staff to hold the Forum to consider ideas in the Paper.

At this Forum there were four areas discussed:

• Advancements in Compression Technology
• Cellularization of Broadcast Architecture
• Improvements in VHF Reception
• Methodologies for Repacking the TV Band

Each area had been the subject of discussion by groups in workshops earlier in the day. At the Forum each of the four groups reported  preliminary findings and recommendations.

After hearing the Forum, which is a preliminary effort, I”d say its gist is that technical changes in the TV industry aren’t going to free up significant TV spectrum for mobile broadband.  There are no advancements in compression technology that can be implemented in a timely manner (i.e., less than 13 years). State-of-the-art in compression technology, and market realities, makes channel sharing by different licensees impractical. Cellularization of broadcast architecture is seen as not practical nor economical. There is room for improvement in VHF reception, perhaps through higher transmit power levels and better, smart receive antennas. An examination of methodologies for repacking the TV band shows no scenarios where stations can avoid sharing channels, unless some stations voluntarily go off-the-air. (And, as we heard in the presentation on compression, sharing is seen as impractical.)

The slides used in each of the four sessions are to be made available on the FCC web site. For those interested in more details now, I share my notes below.

Advancements in Compression Technology

The results of this group were presented by Andrew Setos from the Fox group.

MPEG-2 was published in 1994, and no significant improvements are expected.

Compression equipment has improved such that artifacts are less noticeable, but they are still there. For example, where five years ago there might have been an obvious pixilation, now there is more of a blurring effect.

There are more-modern compression technologies such as MPEG 4. Current TVs do not support MPEG-4, and it could take 13 years to migrate that technology to consumer TVs.

The FCC Technical Paper scenario of multiplexing two HD programs for two different licensees in one 6 MHz channel is not viable due to quality degradation that would result when needing to choose a winner and loser when one HD stream exceeds the bandwidth of the other.

Statistical multiplexing efficiencies are lost with two separate licensees. It can work with the same licensee because the licensee knows what is in the different programs.

As far as pairing an HD station and an SD station in one 6 MHz channel, this is not viable as the trend is toward all HD.

The bit allocation for Mobile DTV is a straight carve-out, and statistical multiplexing does not help.

Cellularization of Broadcast Architecture

Bob Seidel of CBS presented the results of the cellularization group.

A Single Frequency Network (SFN) is much easier with OFDM than with the current 8-VSB modulation method.

“Self-jamming,” or interference between two cells in a SFN, was raised as an undesirable artifact of SFNs that would result in lack of coverage between cells.

SFNs will not help improve reception at the edge of coverage areas because of desired/undesired signal ratios that must be maintained there.

The lack of performance requirements for DTV equalizers is an issue.

Practical issues involved in implementing SFNs include feeding programming to multiple sites, and the cost of building and maintaining multiple sites.

It was suggested that, regarding Mobile DTV, wireless broadband providers should work with broadcasters. The point here is, why broadcast, say, the Super Bowl from hundreds of cell sites when Mobile DTV from one broadcast site will suffice.

Little or no UHF TV spectrum can be repurposed from cellularization.

Improvements in VHF Reception

Kerry Kozad from Dielectric Communications reported on the VHF reception panel.

The group was focused on fixed reception; mobile operation on VHF is not contemplated due to the large mobile antennas that would be required.

The low-VHF band (channels 2-6) is a bigger problem than the high VHF band (channels 7-13). Noise is a bigger problem, for one thing.

There are only 39 stations in the low-VHF band.

Noise varies from location-to-location at low-VHF, making it difficult to have consistent  performance and use common planning factors. There are also undesirable propagation effects at the low VHF band. It would likely require an impractical 15 to 20 dB power increase to alleviate these problems.

High-band VHF suffers from the same noise problems, but not as much. A 10 dB power increase would be required to help significantly.

Receiver antennas can be improved, but not much. The best candidate for improved antenna performance is indoor reception, perhaps through smart antennas working in conjunction with the TV set. The TV and antenna manufacturers have to work together for this to happen.

The FCC should not set consumer antenna performance standards. There are too many variables for a one-size-fits-all performance standard.

It would help to standardize descriptive terminology and performance measurement standards.

The FCC should increase maximum power limits, but be aware that there can be more interference with higher power.

Methodologies for Repacking the TV Band

The spectrum repacking session was led by Bruce Franca from MSTV.

He summarized the status of new modeling efforts and reviewed Technical Paper study assumptions.

Population loss (loss of people served) is one of the costs in reclaiming spectrum.

The focus is on reclamation in the UHF band, as mobile broadband operators are not interested in VHF spectrum.

The study assumptions included locating all stations in channels 2-30, and adding no new stations to channels 2-6.

The minimum number of stations that must share in this scenario are 248. From 20 to 40 percent of Designated Market Areas (DMAs) are impacted and must share, depending on border protection.

A more careful approach to DTV interference is suggested. In analog television, interference can be increased 8 dB before someone notices, and can increase 20-30 dB  before someone stops watching. In DTV, however, most TV sets go from perfect picture to no picture in 1 dB.

Interference performance is governed mostly by DTV receive performance.

Different propagation models are available, but there is no indication any are generally better than the Longley-Rice model.

One question was whether protected service areas should be adjusted to more accurately reflect viewing practices, and if so, how. Nielsen reports 10.9 million over-the-air homes, but it is not clear what that means. For example, a home with both FIOS and over-the-air reception is not considered over-the-air by Nielsen.

Hispanic households have a high percentage of over-the-air reception: 20% in Los Angeles, 35% in Houston, and 28% in Phoenix.

50 million DTV converter boxes were sold.

In discussion, it was noted that this panel’s results refer to sharing being “required.” That assumes no stations voluntarily choose to go off the air. If sufficient stations choose to go off, sharing is not required.