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  1. #1
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    [EN] DataBank Plans Network of Micro Data Centers at Cell Towers

    DataBank, which operates a network of colocation facilities, will provide the data center expertise. Vertical Bridge, which owns 55,000 wireless sites, will provide the real estate.

    Rich Miller
    September 6, 2017

    Communication towers are emerging as the new frontier in edge computing, a trend that is boosting collaboration between data center companies and tower real estate specialists. Almost no one is better positioned to capitalize on this trend than Digital Bridge, a veteran of the tower industry that has built a formidable data center network through a series of acquisitions.

    Two Digital Bridge portfolio companies, DataBank and Vertical Bridge, today announced plans to build a network of micro data centers at the base of cell towers. DataBank, which operates a network of colocation facilities, will provide the data center expertise. Vertical Bridge, which owns 55,000 wireless sites, will provide the real estate.

    “Tower-based data centers bring the cloud into local areas and dovetail with the emerging C-RAN network architecture of the future,” said Bernard Borghei, Executive Vice President of Operations and Co-Founder of Vertical Bridge. “We’re looking forward to working with DataBank to be an important first mover in this space.”

    CRAN is short for Cloud-Radio Access Network (or sometimes Centralized RAN), which uses new topologies and virtualization to reduce the cost and power draw of the network infrastructure. It’s expected to be a key component of next-generation 5G wireless networks.

    Vertical Bridge isn’t alone, as it’s one of three planned networks of edge data centers at telecom towers. In June, cloud infrastructure specialist Vapor IO said it will team with tower REIT Crown Castle to create Project Volutus, a network of fully-managed micro data centers at the base of cell towers. In July, AT&T unveiled plans to deploy computing infrastructure at telecom towers, central offices and small cell antenna locations across its giant network.

    All of these initiatives target the growing market for edge computing, which moves content closer to users, improving the experience for streaming video and gaming. It’s a hot trend for 2017, as the emergence of the Internet of Things and AI reinforce the need for data centers in new places.

    The Missing Link in the Expanding Network

    The growth in edge computing is driven by increased use of consumer mobile devices – especially consumption of video and virtual reality content – and the growth of sensors as part of the Internet of Things. As large files proliferate and end points become more distributed, the geography of data centers is changing to reflect this shift.

    “In addition to improving distribution for content providers and carriers, edge computing can also create an important distribution point for the cloud at a lower cost,” said Raul Martynek, CEO of DataBank. “There’s just one jump to the micro data center at the base of the towers, so not only is the latency for accessing the cloud reduced, but it opens the possibility for real-time applications and a richer more immersive experience for end users.”

    There are many different components of this shift to a data-driven world. Digital Bridge is positioned to address an evolving network architecture. As voice, data and video have shifted to wireless delivery, the traffic on wireless networks has significantly increased. Legacy wireless network architecture typically has a cloud interface at the city or regional level. As a result, traffic is transported long distances at considerable cost and with significant latency.

    Vertical Bridge and DataBank say they are developing details on the type of infrastructure they intend to deploy at the cell towers.

    Different Strategies, Different Visions for the Edge

    The rise of edge computing is prompting the data center industry to expand well beyond the traditional “Big Six” markets – Northern Virginia, New York/New Jersey, Chicago, Dallas, Silicon Valley and Los Angeles – that have traditionally been magnets for third-party service providers. This is happening in two ways. For some providers, “edge”means more infrastructure in secondary markets. For others, the edge means cell towers and office buildings.

    Over the past 18 months we’ve seen a flurry of M&A activity and new investments targeting regional “second tier” data center markets, including the acquisition of ViaWest, Cologix, 365 Data Centers, and C7 Data Centers and new lead investors for Compass Datacenters. EdgeConneX and TierPoint have continued to build out their networks of data centers in second-tier cities.

    The providers targeting tower-based edge computing are led by the DataBank/Vertical Bridge partnership, the Project Volutus team of Vapor IO and Crown Castle. There’as also AT&T and DartPoints, which is building a network of micro data centers within existing office buildings.

    An Eye Towards the Future

    The principals in Digital Bridge are among the most experienced players in wireless real estate. CEO Marc Ganzi and Chairman Ben Jenkins founded the company after playing similar roles for a decade at Global Tower Partners (GTP), the largest privately owned operators of telecom towers. The company was created in 2002 and built a portfolio 16,000 sites before it was acquired by American Tower for $3.3 billion in 2013.

    Ganzi and Jenkins founded Digital Bridge in 2013 with a “singular focus” on owning and operating communications infrastructure companies with strong cash flow. That vision started with wireless infrastructure, but extended to a broader universe of connectivity and data storage companies, including Vertical Bridge and ExteNet Systems, which provides wireless connectivity through distributed antenna systems (DAS), small cells, WiFi and radio access networks (RAN) to extend wireless signals.

    “We’re bringing together two leaders of their respective fields, and the combination will be powerful,” said Ganzi, who is CEO and Co-Founder of Digital Bridge and Executive Chairman of Vertical Bridge. “This partnership is just one example of the convergence that we believe is the future of communications infrastructure, and we’re looking forward to continuing to provide more innovations like the Vertical Bridge/DataBank collaboration to support the needs of our customers.”

    http://datacenterfrontier.com/databa...t-cell-towers/

  2. #2
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    Multi-access Edge Computing

    Brian Santo
    September 8, 2017

    The industry knows that wireless networks are going to need mobile edge computing (MEC), and has formed support organizations. ETSI, for example, calls it Multi-access Edge Computing (it’s the same acronym).

    AT&T earlier this summer talked about its MEC plans, including colocating small data centers at cell towers. “Instead of sending commands hundreds of miles to a handful of data centers scattered around the country, we’ll send them to the tens of thousands of central offices, macro towers, and small cells usually never farther than a few miles from our customers,” the company explained.

    One of the results from implementing MEC will be reducing network latency, which will be critical for autonomous vehicles and other applications such as augmented reality (AR).

    Vendors and cell tower operators are figuring out how to make mobile edge computing happen.

    One example is Vapor IO, which recently formed to provide data center capabilities to cell towers. Earlier this summer, the startup said it is working with Crown Castle, one of the largest cell tower operators in the U.S., to set up tower/data center colocation. The companies are calling their collaboration Project Volutus. Crown Castle took a minority stake in Vapor IO to seal the deal.

    Investment firm Digital Bridge was formed in 2013 in part to target this opportunity. The principals first built Vertical Bridge, now the largest private operator of cell towers in the U.S. Vertical Bridge controls about 40,000 towers and rooftop antennas. Toss in its billboards and other land assets, and Vertical Bridge has roughly 55,000 locations across the U.S. Digital Bridge also bought companies that control cell tower networks in Mexico, Colombia, and Peru.

    Digital Bridge bought DataBank in 2016. The purchase was made deliberately to bring its two subsidiaries together to enter the most recent collaboration.

    “In addition to improving distribution for content providers and carriers, edge computing can also create an important distribution point for the cloud at a lower cost,” said Raul Martynek, CEO of DataBank, in a statement. “There’s just one jump to the micro data center at the base of the towers, so not only is the latency for accessing the cloud reduced, but it opens the possibility for real-time applications and a richer more immersive experience for end users.”

    https://www.sdxcentral.com/articles/...uting/2017/09/

  3. #3
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    Where is the center of the cloud? Iowa.

    Midwest Plays Growing Role in Cloud Geography

    Rich Miller
    August 30, 2017

    No one wants to wait for their music or video. That’s why the location of data centers is critical to delivering online services with low latency. As Internet titans seek to distribute large files to support videos, gaming and virtual reality, the center of the country is proving to be the ideal place to add data center capacity.

    This trend is spurring a data center building boom, pumping billions of dollars into towns across America’s heartland. Five large cloud companies – Apple, Google, Amazon, Microsoft and Facebook – are investing more than $11 billion to build massive server farms across Iowa, Ohio and Nebraska.

    In the latest of these projects, Apple has announced plans to invest $1.3 billion in a new data center campus in Waukee, Iowa. The company is expected to start construction of two data centers early next year, bringing the first building online in 2020.

    “Our new data center in Iowa will help serve millions of people across North America who use Siri, iMessage, Apple Music and other Apple services,” said Apple CEO Tim Cook. “We’re always looking at ways to deliver even better experiences for our customers.”

    During the first phase of Internet growth, data centers were built primarily in technology hubs near major cities on the coasts, especially Northern Virginia, New York and Silicon Valley. These markets remain healthy, but site selection with the emergence of the hyperscale data center – massive buildings optimized to house tens of thousands of web servers and data storage devices. Data center development shifted to areas with an abundance of cheap land and power, including rural locations.

    No state has benefited more from this trend than Iowa, which is home to huge cloud campuses for Google, Microsoft, Facebook and now Apple.

    “Apple’s significant investment and commitment to grow in Iowa is a clear vote of confidence in our state,” said Iowa Gov. Kim Reynolds. “This announcement further solidifies Iowa as a hub where innovation and technology flourish and demonstrates this is a place where world-class companies can thrive.”

    A Convergence of Clouds

    Placing data centers in the center of the country makes it easier to distribute content to major markets like Chicago and Dallas, reducing lag and buffering for streaming media like Netflix movies or Facebook videos. It also allows for data to move quickly to either coast, which can be important in application development.

    As an example, Amazon Web Services customers using the company’s Ohio data centers experience just 12 milliseconds of round-trip latency when sending data to the cluster of AWS facilities in Northern Virginia. This makes it easier for customers to replicate data across the two regions, which allows for automatic failover when web applications experience performance problems or outages.

    Google kicked off the Iowa data center boom with its 2007 announcement of a new facility in Council Bluffs, which over the last decade has grown into the company’s largest cloud campus, with well over 1 million square feet of data center space deployed.

    The trend has accelerated in the past two years with a flurry of mega-campuses arriving in the region.

    • Microsoft announced plans in June 2016 to invest up to $2 billion in a new data center in West Des Moines, where it already operates two huge data center campuses. Local officials said “Project Osmium” would boost Microsoft’s total investment in West Des Moines to nearly $3.5 billion.
    • In May Facebook broke ground on a 1 million square foot data center building in Altoona. It’s the fourth data center on the company’s cloud campus, and will boost its presence to more than 2.5 million square feet of space and $1.5 billion in investment.
    • Google continues to build out its campus in Council Bluffs, where it has begun building multi-story data centers to increase the data storage capacity of its existing real estate. The company expects to invest up to $2.5 billion in its Iowa cloud campus.


    Data centers have emerged as attractive projects for economic development, serving as symbols of the digital economy. At least 26 states now offer economic incentives for data center projects, which include tax breaks on land, power and the purchase of servers, storage devices and power equipment like UPS systems and backup generators.

    Why Cloud Campuses Love Iowa

    The rapid growth of cloud computing has spurred a building boom for the major Internet platforms, as Google, Microsoft, Amazon and Facebook are all super-sizing their cloud campuses to add data center capacity.

    Cloud campuses are where these companies concentrate massive amounts of computing power in multiple data center facilities. These data center hubs enable companies to rapidly add cloud capacity and electric power, creating economies of scale as more workloads migrate into these massive server farms.

    Iowa has benefited from a confluence of factors that make it attractive to data centers, including its location, which provides low latency to deliver online services to the center of the country. The state has relatively low costs for land and utility power, and lower exposure to natural disasters than many areas of the nation, with low risk from hurricanes and earthquakes. Data center projects also benefit from incentive programs passed by the Iowa legislature in 2009.

    Apple Joins the Data Center Party

    The enormous scale of new cloud campuses can be seen in Apple plans to purchase a whopping 2,000 acres of land in Waukee. The first phase of the project will include two data center facilities that are expected to run entirely on renewable energy.

    Procuring green energy has become a priority for cloud builders, who use enormous amounts of electricity as they consolidate enormous volumes of business activity inside their walls. In 2016, data center providers signed contracts for more than 1.2 gigawatts of renewable power, marking a dramatic turnaround from earlier headlines critiquing the industry’s dependence upon “dirty coal.”

    Iowa state and local officials spent 20 months working with Apple to find a suitable location for the new data center facility. The Iowa Economic Development Authority (IEDA) worked with the Greater Des Moines Partnership and Waukee officials once the company’s project team narrowed its Iowa search to one site. Waukee supported the project with a local tax abatement and infrastructure improvements, while the IEDA Board approved tax incentives via the High Quality Jobs program for the more than $1.3 billion project that will create at least 50 jobs at a qualifying wage of at least $29.12 per hour. All told, the incentives added up to an estimated $207 million.

    Apple will also contribute up to $100 million to a newly created Public Improvement Fund dedicated to Waukee community development and infrastructure. The fund will be managed by the City of Waukee and support the development of community projects like parks, libraries and recreational spaces, as well as infrastructure needs. The first project the fund will support is construction of the Waukee Youth Sports Campus featuring a greenhouse, playground, fishing pier and fields for high school and public sporting events.

    Here’s a look at the development of Iowa as a data center market, and the presence for the major hyperscale players.

    Google

    Google was the first cloud builder to arrive in Iowa, building its first data center in Council Bluffs in 2007. It soon acquired a larger plot of land on the outskirts of town for a larger cloud campus. Google has already invested $1.5 billion on infrastructure in Iowa, and has plans to spend an additional $1 billion building data centers in the state.

    Joe Kava, Vice President for Data Center Operations at Google, says the company’s multi-building project in Council Bluffs “is the world’s largest data center campus. Each of these building pads is more than a third of a mile long, with multi-story data centers.”

    Google has lots of land in Iowa. To boost its cloud capacity, Google is going vertical with its data center design, shifting from a single-story design to four-story data centers.

    (continua)

  4. #4
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    Microsoft

    Microsoft’s newest Iowa data center, known as Project Osmium, will be built on 200 acres of land spanning Warren County and 40 acres in Madison County. Plans call for four phases of construction, with data centers between 256,000 and 583,200 square feet in size, for a total planned footprint of 1.7 million square feet.

    Project Osmium is Microsoft’s third campus in the West Des Moines area. Why separate campuses, instead of one large campus? City officials say Microsoft is spreading out its risk out of concern about tornadoes, seeking to limit potential disaster damage from any single storm. The three sites are between five and seven miles apart.

    As with Apple, the Microsoft project brings benefits for the local community. Project Osmium will include infrastructure upgrades including new power lines, streets, water lines and sanitary sewer lines that will help accelerate the development of over 5,000 acres of land in northern Warren and Madison counties – including 10 miles of new roadway.

    Facebook

    Facebook’s project in Altoona has seen the most aggressive construction schedule of any of the company’s data center campuses. Just three years after announcing its plans for a server farm in Iowa, Facebook has completed two massive data centers and begun work on a third. Each building costs about $300 million to build and fill with servers and networking equipment, placing Facebook’s investment above $900 million.

    Altoona was the first location where Facebook committed to a third data center, which is likely a reflection of Iowa’s favorable environment. Earlier this year it boosted that commitment with the announcement of a fourth building in Altoon, a massive 1 million square foot facility that will be the company’s largest data center yet.

    One of the factors that worked in Iowa’s favor was the availability of renewable wind energy. Facebook worked with Iowa utility MidAmerican Energy and wind farm developer RPM Access to fund the construction of a wind turbine project that would generate 138 megawatts of new wind energy capacity to the Iowa grid – enough to more than offset the power Facebook uses on its Altoona campus.

    Amazon Web Services

    Although it is the largest player in cloud computing, Amazon Web Services focused its operations on the East and West Coasts of the U.S., with a massive cluster of data centers in Northern Virginia (which may soon reach 1 gigawatt in capacity) and smaller operations in Oregon and Northern California.

    That changed in 2016, when AWS opened a cloud region in central Ohio, with data centers in three towns: Hilliard, Dublin and New Albany. Amazon standardizes its data centers to house between 50,000 and 80,000 servers, according to company presentations. That consistent approach can seen in the Ohio projects, in which all the data centers are 150,000 square feet, – the same size as the company’s recent construction in Northern Virginia.

    http://datacenterfrontier.com/as-iow...oud-geography/

  5. #5
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    “There’s just one jump to the micro data center at the base of the towers, so not only is the latency for accessing the cloud reduced, but it opens the possibility for real-time applications and a richer more immersive experience for end users.”
    Eu ficaria satisfeito se pudesse falar no celular com qualidade.

    Mas deixa ver se entendi: a idéia seria replicar em cada torre para reduzir RTT de 1-50ms para 0ms, ainda que a comunicação da torre com celulares ultrapasse 200ms.

  6. #6
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    ETSI widens scope of mobile edge standard

    Richard Chirgwin
    29 Mar 2017

    It's more than just the mobile edge, so the MEC's taken on a new name and brief

    The European Telecommunications Standards Institute has decided its Mobile Edge Computing (MEC) effort needed a bigger brief, so it's renamed it as Multi-access Edge Computing (MEC).

    The basic brief of the Industry Specification Group (ISG) was to shepherd the transformation of mobile base stations from monolithic radio sets into computers in their own right.

    It published its first proofs-of-concept in 2015, followed by foundation specifications in April 2016.

    Standards to flow from MEC covered service scenarios, a framework and reference architecture, technical requirements, metrics and best practice guidelines.

    That effort seems to have schooled the ISG that its work stretched beyond mobile base stations – hence new name.

    The group's announcement says its “future work will take into account heterogeneous networks using LTE™, 5G, fixed and WiFi technologies. Additional features of the current work include developer-friendly and standard APIs, standards-based interfaces among multi-access hosts and an alignment with NFV architecture.”

    The kinds of capabilities the MEC highlights are support for various virtualization technologies, giving applications the ability to discover other applications and services, and API, management interface and orchestrator standardisation.

    https://www.theregister.co.uk/2017/0...dge_computing/

  7. #7
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    UK: Nearly half a million extra towers will be needed for the 5g network

    Experts from leading British universities say most of the new towers will need to be at least 80 feet tall to provide proper service.

    There are between 30,000 and 40,000 masts now.

    Sarah Knapton
    30 March 2017

    Rolling out high speed mobile phone coverage and internet to the forgotten corners of rural Britain will require at least 400,000 extra masts, many of which will need to be 80ft high, experts have predicted.

    In this month’s budget Phillip Hammond, the Chancellor, pledged to invest £1.1 billion the development of a 5g network which will bring faster and more reliable mobile broadband and phone coverage to the UK by the early 2020s.

    But a recent report by consumer watchdog Which? found that mobile users in half of England cannot even access 4g, while in Wales the fast signal is available for just one third of the time.

    Expert from the Institution of Engineering and Technology (IET), King’s College London, and the universities of Surrey and Sussex, warned that people living the countryside may have to accept 80 foot (25 metre) masts if they want to catch up and enjoy the faster service.

    More than 10 times the number of masts and base stations, will be needed for full coverage across the country, but super-fast 1-2 gigabits per second speeds will always be confined to cities, they warned.

    Professor Will Stewart, of the IET said: “There is nowhere near enough capacity to deliver what we think the system needs, there never has been.

    “The crucial thing is you need to be shorter range to deliver the extra capacity, that means more base stations, at least ten times more, maybe 100 times. There are between 30,000 and 40,000 masts now.

    “The coverage is enormously important. It’s not just ex-Prime Minister’s who are concerned that they can’t get coverage in Cornwall. We need services to always work, we see them now as a utility.

    “One of the things you are going to see in five years is the masts getting taller, to get more coverage. 25 metres is what the mobile operators are asking for. The UK has got the shortest masts in Europe. We’ve done something really stupid, we’ve kept the masts below the treeline, but the trees grow taller every year.”

    According to an HM Treasury report released this week, 5G will open the doors “to potentially revolutionary technologies such as automated cars and advanced manufacturing, as well as enabling the many thousands of connected devices, such as smart energy meters, that are predicted to enter our everyday world as part of the Internet of Things (IoT).”

    However the current signal in some rural areas is currently so bad that EE is preparing to launch a mobile mast suspended from a helium blimp as part of its effort to improve coverage.

    4G replaced 3G internet as a mobile communications standard several years ago and was designed to provide wireless internet access at a much higher speed, allowing customers to watch videos and use social media on the move.

    But even in London most people can only access a 4G signal 70% of the time and the capital has one of the worst downloads speeds in the country. And fewer than half of mobile connections were made on a 4G service at the end of last year according to Ofcom.

    Mischa Dohler, Professor of Wireless Communication at King’s College said: “The rural coverage problem is a big headache. If coverage wasn’t there in 4g it won't be in 5g.

    “The real problem is the cost to put up the base station in rural areas. So one recommendation is to deregulate street furniture. That’s what we really need. Then you can roll our the base stations you need.”

    Tom Fyans, director of campaigns and policy at the Campaign to Protect Rural England (CPRE), said networks should consider siting base stations on churches or farm buildings to avoid the need for intrusive masts.

    “Super slow speeds continue to frustrate communities in more remote areas. Yet we need to ask whether we can deliver the type of coverage being suggested here without markedly harming the character of our precious landscapes.

    “Rather than building thousands of ever higher masts at the behest of industry, we need to maintain strong planning protections and help local communities add new infrastructure to existing buildings. Churches or farm buildings can provide the right structure, if damage to their heritage value is prevented.

    “Creative efforts that engage local communities will make sure rural areas are not left behind and protect the countryside."

    Some communities are even being forced to pay for their own masts, or run fibres to nearby villages which do have coverage to pick up a signal.

    Prof Stewart, who clubbed together with locals in his village to pay £25,000 for internet link up to his village said: “We did it, and several villages around me have done so as well.

    “Since we did it BT has decided to come in to the billage, but it works our cheaper to do it through the community. BT charges £30 a month, but our community network is only £10 a month. So why would anyone ask for BT?”

    Prof Stephen Temple, of the Institute of Communication Systems at the University of Surrey, added: “The biggest headache for policymakers is going to be coverage over the next 20 years.”

    http://www.telegraph.co.uk/science/2...rural-britain/


    US: 5g could require cell towers on every street corner

    Bill Snyder
    Sep 8, 2016

    Would you want a cell phone tower or network base station in your neighborhood? For many people the answer is "no way." But when 5G — the ultra-fast, next generation of mobile connectivity — arrives it's likely that millions of new cell towers will spring up to handle the traffic, said FCC Chairman Tom Wheeler on Monday.

    The new 5G wireless is not the only technology that will require more and more cell towers. Google's much-hyped gigabit fiber deployments have stalled, and it appears to be turning toward wireless broadband. That too will likely require towers or some sort of relay equipment to beam signals to homes and offices.

    Already, 200,000 or so cell phone towers are scattered across the United States, Wheeler said Wednesday during a speech at the annual CTIA convention in Las Vegas. But unlike the current LTE (sometimes called 4G) technology most carriers use to beam data smartphones, 5G requires a more dense network of towers to handle the traffic, which is why Wheeler and the industry figure the towers will multiply like Tribbles on the Starship Enterprise.

    In the wireless industry, that process is called densification. "Network densification means more small cells, more mid cells, pico cells [and] metro cells," said Chris Pearson, President of the 5G Americas wireless trade industry association, who spoke with CIO.com at CTIA. In other words, 5G means a lot more towers.

    lthough 5G won't be here for a while, despite the hype, it should arrive at some point in this next decade, and when it does consumers will demand it. The wireless tech will be much faster than LTE, but exactly how much faster is not yet clear.

    Ericsson said it had achieved 5 Gbps on a testbed for 5G. That's about 50 times faster than today's fastest LTE networks. Samsung demonstrated potential 5G technologies running at 7.5 Gbps and got a stable 1.2-Gbps signal to a minivan traveling at highway speeds. By contrast, LTE speeds vary from about 10 Mbps to 40 Mbps.

    However, residents of many communities have blocked the construction of cell phone towers in their neighborhoods, some citing concerns over potential health problems. Others are simply put off by the sheer ugliness of the towers. Gaining approval from local governments can also be very slow. "If siting [or the approval process] for a small cell takes as long and costs as much as siting for a cell tower, few communities will ever have the benefits of 5G," Wheeler said.

    To my knowledge, no studies exist that confirm cell towers produce harmful radiation, but consumers who believe there is a link have to choose between allowing the towers or settling for less-robust wireless connectivity.

    Wheeler acknowledged those concerns and suggested that wireless carriers should consider sharing towers to reduce density. "If we're talking about thousands of antennas in a city, and you've got four carriers, and we are serious about leading the world in 5G deployment in our very large and spread out country, we ought to explore creative options on how best to build that infrastructure," he said.

    Although there is some history of cooperation between carriers, it tends to be the exception and not the rule, and I wouldn't hold your breath waiting for U.S. carriers to play nice.

    https://www.cio.com/article/3117705/...et-corner.html

  8. #8
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    Regardless of the standard, the real performance of every network will vary by provider, their configuration of the network, the number of active users in a given cell, the radio environment in a specific location, the device in use, plus all the other factors that affect wireless performance.

    ...

    Table 7-6. LTE, and LTE-Advanced comparison

    LTE LTE-Advanced
    Peak downlink speed (Mbit/s) 300 3,000
    Peak uplink speed (Mbit/s) 75 1,500
    Maximum MIMO streams 4 8
    Idle to connected latency (ms) < 100 < 50
    Dormant to active latency (ms) < 50 < 10
    User-plane one-way latency (ms) < 5 < 5

    User-plane one-way latency is the target time specified by the LTE standard for the one-way transit between a packet being available in the wireless device and the same packet being available at the radio tower. In other words, it is the one-way latency of the first wireless hop when the device is in the high-power continuous reception state. Every application packet will incur this cost—no shortcuts.

    Both 3G and 4G networks have a unique feature that is not present in tethered and even WiFi networks. The Radio Resource Controller (RRC) mediates all connection management between the device in use and the radio base station. Understanding why it exists, and how it affects the performance of every device on a mobile network, is critical to building high-performance mobile applications. The RRC has direct impact on latency, throughput, and battery life of the device in use.

    3G, 4G, and WiFi Power Requirements

    The radio is one of the most power-hungry components of any handset. In fact, the screen is the only component that consumes higher amounts of power when active—emphasis on active. In practice, the screen is off for significant periods of time, whereas the radio must maintain the illusion of an "always-on" experience such that the user is reachable at any point in time.

    One way to achieve this goal is to keep the radio active at all times, but even with the latest advances in battery capacity, doing so would drain the battery in a matter of hours. Worse, latest iterations of the 3G and 4G standards require parallel transmissions (MIMO, Multicell, etc.), which is equivalent to powering multiple radios at once. In practice, a balance must be struck between keeping the radio active to service low-latency interactive traffic and cycling into low-power states to enable reasonable battery performance.

    How do the different technologies compare, and which is better for battery life? There is no one single answer. With WiFi, each device sets its own transmit power, which is usually in the 30–200 mW range. By comparison, the transmit power of the 3G/4G radio is managed by the network and can consume as low as 15 mW when in an idle state. However, to account for larger range and interference, the same radio can require 1,000–3,500 mW when transmitting in a high-power state!

    In practice, when transferring large amounts of data, WiFi is often far more efficient if the signal strength is good. But if the device is mostly idle, then the 3G/4G radio is more effective. For best performance, ideally we would want dynamic switching between the different connection types. However, at least for the moment, no such mechanism exists. This is an active area of research, both in the industry and academia.

    So how does the battery and power management affect networking performance? Signal power (explained in “Signal Power”) is one of the primary levers to achieve higher throughput. However, high transmit power consumes significant amounts of energy and hence may be throttled to achieve better battery life. Similarly, powering down the radio may also tear down the radio link to the radio tower altogether, which means that in the event of a new transmission, a series of control messages must be first exchanged to reestablish the radio context, which can add tens and even hundreds of milliseconds of latency.

    Both throughput and latency performance are directly impacted by the power management profile of the device in use. In fact, and this is key, in 3G and 4G networks the radio power management is controlled by the RRC: not only does it tell you when to communicate, but it will also tell you the transmit power and when to cycle into different power states.

    LTE RRC State Machine

    The radio state of every LTE device is controlled by the radio tower currently servicing the user.

    ...


    RRC Idle
    Device radio is in a low-power state (<15 mW) and only listening to control traffic. No radio resources are assigned to the client within the carrier network.
    RRC Connected
    Device radio is in a high-power state (1000–3500 mW) while it either transmits data or waits for data, and dedicated radio resources are allocated by the radio network.

    The device is either idle, in which case it is only listening to control channel broadcasts, such as paging notifications of inbound traffic, or connected, in which case the network has an established context and resource assignment for the client.

    When in an idle state, the device cannot send or receive any data. To do so, it must first synchronize itself to the network by listening to the network broadcasts and then issue a request to the RRC to be moved to the "connected" state. This negotiation can take several roundtrips to establish, and the 3GPP LTE specification allocates a target of 100 milliseconds or less for this state transition. In LTE-Advanced, the target time was further reduced to 50 milliseconds.

    Once in a connected state, a network context is established between the radio tower and the LTE device, and data can be transferred. However, once either side completes the intended data transfer, how does the RRC know when to transition the device to a lower power state? Trick question—it doesn’t!

    IP traffic is bursty, optimized TCP connections are long-lived, and UDP traffic provides no "end of transmission" indicator by design. As a result, and not unlike the NAT connection-state timeouts solution covered in “Connection-State Timeouts”, the RRC state machine depends on a collection of timers to trigger the RRC state transitions.

    ...

    In the high-power state, the RRC creates a reservation for the device to receive and transmit data over the wireless interface and notifies the device for what these time-slots are, the transmit power that must be used, the modulation scheme, and a dozen other variables. Then, if the device has been idle for a configured period of time, it is transitioned to a Short DRX power state, where the network context is still maintained, but no specific radio resources are assigned. When in Short DRX state, the device only listens to periodic broadcasts from the network, which allows it to preserve the battery—not unlike the DTIM interval in WiFi.

    If the radio remains idle long enough, it is then transitioned to the Long DRX state, which is identical to the Short DRX state, except that the device sleeps for longer periods of time between waking up to listen to the broadcasts.




    What happens if the network or the mobile device must transmit data when the radio is in one of Short or Long DRX (dormant) states? The device and the RRC must first exchange control messages to negotiate when to transmit and when to listen to radio broadcasts. For LTE, this negotiation time ("dormant to connected") is specified as less than 50 milliseconds, and further tightened to less than 10 milliseconds for LTE-Advanced.

    So what does this all mean in practice? Depending on which power state the radio is in, an LTE device may first require anywhere from 10 to 100 milliseconds (Table 7-9) of latency to negotiate the required resources with the RRC. Following that, application data can be transferred over the wireless link, through the carrier’s network, and then out to the public Internet. Planning for these delays, especially when designing latency-sensitive applications, can be all the difference between "unpredictable performance" and an optimized mobile application.


    (continua)

  9. #9
    WHT-BR Top Member
    Data de Ingresso
    Dec 2010
    Posts
    18,556
    What Are "Assigned Radio Resources"?

    In LTE, just as in most other modern wireless standards, there are shared uplink and downlink radio channels, the access to which is controlled by the RRC. When in a connected state, the RRC tells each and every device which timeslots are assigned to whom, which transmit power must be used, modulation, plus a dozen other variables.

    If the mobile device does not have an assignment for these resources by the RRC, then it cannot transmit or receive any user data. Consequently, when in a DRX state, the device is synchronized to the RRC, but no uplink or downlink resources are allocated to it: the device is "half awake."

    ...

    Radio Access Network (RAN)

    The radio access network (RAN) is the first big logical component of every carrier network (Figure 7-10), whose primary responsibility is to mediate access to the provisioned radio channel and shuttle the data packets to and from the user’s device. In fact, this is the component controlled and mediated by the Radio Resource Controller. In LTE, each radio base station (eNodeB) hosts the RRC, which maintains the RRC state machine and performs all resource assignment for each active user in its cell.

    Whenever a user has a stronger signal from a nearby cell, or if his current cell is overloaded, he may be handed off to a neighboring tower. However, while this sounds simple on paper, the hand-off procedure is also the reason for much of the additional complexity within every carrier network. If all users always remained in the same fixed position, and stayed within reach of a single tower, then a static routing topology would suffice. However, as we all know, that is simply not the case: users are mobile and must be migrated from tower to tower, and the migration process should not interrupt any voice or data traffic. Needless to say, this is a nontrivial problem.

    First of all, if the user’s device can be associated with any radio tower, how do we know where to route the incoming packets? Of course, there is no magic: the radio access network must communicate with the core network to keep track of the location of every user. Further, to handle the transparent handoff, it must also be able to dynamically update its existing tunnels and routes without interrupting any existing, user-initiated voice and data sessions.

    In LTE, a tower-to-tower handoff can be performed within hundreds of milliseconds, which will yield a slight pause in data delivery at the physical layer, but otherwise this procedure is completely transparent to the user and to all applications running on her device. In earlier-generation networks, this same process can take up to several seconds.

    However, we’re not done yet. Radio handoffs can be a frequent occurrence, especially in high-density urban and office environments, and requiring the user’s device to continuously perform the cell handoff negotiations, even when the device is idle, would consume a lot of energy on the device. Hence, an additional layer of indirection was added: one or more radio towers are said to form a "tracking area," which is a logical grouping of towers defined by the carrier network.

    The core network must know the location of the user, but frequently it knows only the tracking area and not the specific tower currently servicing the user—as we will see, this has important implications on the latency of inbound data packets. In turn, the device is allowed to migrate between towers within the same tracking area with no overhead: if the device is in idle RRC state, no notifications are emitted by the device or the radio network, which saves energy on the mobile handset.

    ...

    http://chimera.labs.oreilly.com/book...0545/ch07.html

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