[Κινητές και Δορυφορικές] Γενικές απορίες κι ανακοινώσεις/επικαιρότητα 2013/2014

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The Story of an 802.11ac Network

https://www.youtube.com/watch?v=XoC36DEUbf8&list=PL0C95AFFE4ABE88B3

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Arianespace—Sentinel-1A Getting Final Checkout (Launch Preparations)

[SatNews] Arianespace's seventh Soyuz to be launched from French Guiana is now undergoing final checkout for its April 3 liftoff following installation of the mission's satellite passenger—Sentinel-1A—atop this medium-lift vehicle.

Sentinel-1A's mating with Soyuz occurred yesterday, after the workhorse Russian-built vehicle rolled out to the launch pad in the Spaceport's northwestern sector. The satellite was fitted as part of an integrated "upper composite," consisting of Sentinel-1A, the Fregat upper stage that will place it into orbit, and the Soyuz ST fairing. The activity occurred inside the 53-meter-tall mobile gantry that provides a protected environment for the vertical payload installation.  This is one of the main differences in launcher processing at the Spaceport compared to the horizontal processing of vehicles on Soyuz launch sites at the Baikonur Cosmodrome in Kazakhstan and Plesetsk Cosmodrome in Russia.

The upcoming launch—designated Flight VS07 in Arianespace's numbering system— is scheduled at precisely 6:02:26 p.m. local time in French Guiana, on Thursday, with the mission lasting 23 minutes to Sun-synchronous orbit. Sentinel-1A is to deliver essential data for Copernicus, a program of the European Commission in partnership with the European Space Agency - which will create a sustainable European satellite network to collect and evaluate environmental data for civil safety and humanitarian purposes. The spacecraft was developed in an industrial consortium led by Thales Alenia Space as prime contractor, with Airbus Defence and Space responsible for the C-SAR synthetic aperture radar payload.

Follow Arianespace's launch activity at http://www.arianespace.com/.

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Statement by Neelie Kroes on EP votes to end roaming charges

http://ec.europa.eu/avservices/video/player.cfm?ref=I088198

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This presentation covers the advancement of wireless communications and networking technology for current generation as well as evolution of future generations.

Topics enable a wireless ecosystem, from service providers seeking answers on delivering services and meeting demand, to device manufacturers and developers seeking to understand the applications in LTE, LTE-A, 4G/5G, etc. Wireless access demands have given rise to wireless networks that significantly rely on satellite communication to enable rural and remote wireless connectivity via satellite backhaul. This trend presents many opportunities and challenges for capacity improvement and coexistence of various technological elements.

Free access compliments of: GL Communications

https://www.comsoc.org/form/tutorial-registration-next-generation-4g5g-cellular-networking

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Heterogeneous networks by Ericsson

http://www.ericsson.com/res/docs/whitepapers/WP-Heterogeneous-Networks.pdf

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Tutorial on  Small Cell/HetNet Deploymen

http://www.ieee-globecom.org/2012/downloads/t1/1SmallCellTutorialGlobecom12Jie_v1b.pdf

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LTE: The Future of Mobile Data
by Steven Hartley, Senior Analyst, Ovum, & Julien Grivolas, Principal Analyst, Ovum

Long Term Evolution (LTE), a new generation of mobile network technology, promises to revolutionize the use of data services on the move. Over the past year, it has gained unparalleled support from mobile operators around the world, particularly in North America. Its introduction is now inevitable, despite the major investment needed.

An Overview
LTE is a wireless technology often discussed alongside its more mature alternative, WiMAX, in relation to the evolution of mobile telecom networks to “4G.”* Both LTE and WiMAX technologies can deliver wireless data connectivity that is able to compete with fixed-line broadband services provided by DSL or cable. LTE’s proponents state that it may allow customers to drop their fixed-line broadband connections altogether.

LTE’s primary objective is to enable operators to better and more cost-effectively transport the rapidly growing volume of mobile IP data traffic on their networks. This mobile data traffic is growing exponentially, while the service revenues paid by end users are either flat or falling due to intense competition. This disconnection between income and costs is threatening to undermine the positive revenue-generating potential of mobile data services for operators.



Therefore, LTE offers a long-term route to financial security. Nonetheless, migrating to LTE does require significant investment from mobile operators, and not just in upgrading base stations. For example, operators’ core networks, which carry the consolidated traffic from all base stations, will also need to evolve. Operators will also have to deploy SAE/EPC (System Architecture Evolution/Evolved Packet Core) network elements in parallel with LTE.

LTE technical specifications are defined by the 3GPP (3rd-Generation Partnership Project). The 3GPP’s role is important because it provides the technology with an enormous addressable market. In 2008, 89% of mobile connections worldwide, including those from AT&T and T-Mobile in the U.S., used one of the standards defined by the 3GPP. In addition, in an unprecedented move in the industry, many operators are shifting away from rival technologies and converging on LTE. For example, several CDMA operators, including Verizon Wireless and MetroPCS in the U.S. or Bell and TELUS in Canada, have stated publicly that they will migrate to LTE. LTE offers the next stage in the evolution of the networks on which these users depend for mobile connectivity. Such a large addressable market ensures:

maximum equipment vendor focus;
a wide range of devices;
economies of scale for operators and end users buying equipment; and
support for international roaming.

*Technically speaking, “4G“ refers to technology defined by the International Telecoms Union (ITU) as IMT-Advanced. For LTE, this refers to the next step in the evolutionary process, LTE Advanced, while for WiMAX this actually refers to 802.16m, the successor of mobile WiMAX.

The Market for LTE Services
LTE gained significant momentum as the dominant next-generation mobile access technology throughout 2008. Commercial LTE launches will initially appear on a small scale in Japan, the U.S. and Sweden in 2010, with larger players in Western Europe following in 2011 to 2012.

The ramp-up in LTE deployments can be seen in the massive year-on-year connections growth forecast for both 2013 (219%) and 2014 (175%). We expect to see 109 million LTE connections worldwide by 2014, as shown in Figure 1. We estimate that the number of LTE connections will almost equal those for mobile WiMAX in 2013 and will be double the number of mobile WiMAX connections in 2014. Clearly, the window of opportunity for mobile WiMAX is closing rapidly with such widespread support for LTE.

However, challenges remain as to the business case for LTE at an individual operator level. In the current economic climate, investors will frown upon the significant investments required to deploy LTE if sufficient return on that investment cannot be proven. There are market circumstances that favor a more aggressive deployment, such as evolving to LTE from CDMA, particularly if faced with an operator deploying HSPA+. But operators need to take a very hard look at the business case, especially when the evolution of HSPA offers a potential alternative on existing infrastructure. HSPA will remain the dominant data-optimized network technology, accounting for 79% of high-speed data connections in 2014.



Key Suppliers of Mobile LTE Network Equipment
All the major mobile infrastructure vendors consider LTE the strategic technology for future mobile broadband communications and therefore are actively targeting this business opportunity. However, differences remain in the way they approach this opportunity due to several parameters:

Current market position in legacy technologies (e.g. CDMA, GSM/UMTS/HSPA and TD-SCDMA)
Ability to evolve the entire network or one part of the network
Ease of migrating from legacy products
The vendor’s R&D capabilities to enable customized solutions for specific operator needs
Vendor financial health to support operators throughout the whole migration, which is likely to span several years
The increased maturity of the technology is reflected in the announcement of the first contracts between LTE and SAE. However, the industry must avoid raising expectations too far. It did this with the expensive deployment of 3G, which is only now reaping dividends, thanks to HSPA—and not the oversold UMTS. Many issues still need to be addressed.

Device Development Lagging Behind Networks
Commercial launches of LTE networks are expected to start in 2010. However, the first devices will be data-only external modem devices such as data cards and USB modems. For operators, data-only devices are more significant for LTE compared to previous network rollouts, since voice services are now provided by legacy technologies.

Initial LTE handsets will follow after about a year, but are still most likely to rely on the existing network for voice calls and therefore only use LTE for data. Handsets that natively support voice over the LTE network will take approximately one year longer to appear on the market. In the meantime, handsets will need to support multiple mobile technologies to support voice services.

This highlights one of the primary obstacles to device development: Initial chipsets for LTE handsets will all need to be multimode. This means they must support 3G services alongside LTE, so that users can still receive a service even if they move to a location outside of LTE coverage, and to ensure that the handover between two technologies during a voice call or data session is seamless.

The technical complexity of the new technology means that LTE devices will be more expensive than their 3G counterparts. Costs will start to fall only once a volume market has been established. A premium associated with LTE devices will exist for some time due to the increased memory and processor requirements needed to process the volume of data enabled by LTE. Nonetheless, LTE will encourage smartphone adoption as service providers look to drive up data usage and offer superior browsing experiences.


Nokia Siemens Networks
An Interview with Sue Spradley, Head of Nokia Siemens Networks for North America


Broadband is everywhere. The Internet already plays a pivotal role in our daily lives, and it will become even more pervasive as the Internet goes mobile. Nokia Siemens Networks (NSN) has been at the forefront of LTE or 4G wireless technology development for many years. The company is the first network provider in the world to complete a number of LTE milestones, including the world’s first LTE call using commercial hardware and software. With its global scope and scale and deep understanding of network operation requirements, Nokia Siemens Networks is continually devising innovative ways to use this technology strategically to address its customers’ key business challenges and lead industry growth.

What do you see as the main trends in the mobile industry? How can LTE help in addressing the associated network issues?
Over the past few years, we have seen explosive data traffic growth as millions of services and billions of devices come online. As more and more people use mobile data for work, entertainment and social networking, service providers have to find ways to optimize their assets, like spectrum, and do so as efficiently as possible. This is where LTE comes in.

Our opportunity is to help operators discover new ways to leverage their networks to give their customers a unique experience that differentiates them. NSN’s vision of a “Network of One” puts the customer at the center of the network and allows service providers to create an environment that delivers a personalized experience easily and efficiently. Our Subscriber Data Management (SDM) solution is a game changer for our company. It plays a critical role in helping service providers tailor the user experience for each subscriber.

What is your view on LTE market development in the U.S. and globally?
Being involved in the LTE deployment for the provider NTT DoCoMo in Japan, we see Japan, along with the U.S., aggressively leading the world toward commercial LTE services. These operators want to move quickly. Knowing that companies like Verizon and AT&T are leading the way to LTE in the U.S., we have established our Next-Generation Lab and LTE Center of Competence in Dallas so that we have R&D, interoperability testing and much more in our own backyard.

What specific challenges will operators face when migrating to LTE?
It is critical to understand that LTE migration means an end-to-end evolution. People tend to only think about radio access, but it is really the tip of the iceberg of what is involved in 4G migration. For example, core network and backhaul also have to be considered. Everything has to be 100% IP, which means that wireless operators need to be, or at least need network partners who are, well versed in IP technology and its characteristics. We’re basically seeing the worlds of telecom and IT fusing together, so in some sense, many companies are entering uncharted territory, which can be an exciting adventure.

What is Nokia Siemens Networks’ key value proposition to support operators migrating to LTE?
In North America, Nokia Siemens Networks’ unique value proposition is providing a network advantage that makes the network a catalyst for communication service provider innovation. We do this in many ways, but key differentiators for us are the core networks and SDM solutions that we’ve delivered to the majority of tier one operators in the U.S. and Canada. This is actually the most critical part of the transition to get right, and it’s what we do best. We are leading the way in LTE as we help service providers create the best user experience for their customers.

Πηγή: http://www.forbescustom.com/TelecomPgs/LTEP1.html
 

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Radio Wrestlers Fight It Out at the DARPA Spectrum Challenge

Clash of the software-defined radio algorithms leaves two winners



Photo: Darpa
Flying Bits: The 465 square-meter, 400-node ORBIT radio grid facility at Rutgers University, in New Jersey, hosted DARPA Spectrum Challenge software defined radio algorithms in head-to-head competitions.
The words engineering and sports aren’t usually used in the same sentence, and the two activities usually don’t happen in the same room. But they were, and they did, last week at the DARPA Spectrum Challenge, held at the Defense Advanced Research Projects Agency headquarters in Arlington, Va.

The goal of the contest, the first ever DARPA challenge on the use of spectrum, was to demonstrate how a software-defined radio can use a given communication channel in the presence of other users and interfering signals. Over the course of two days, normally taciturn techies oohed, aahed, and cheered as 18 teams competed in a series of head-to-head matches to see who had the best algorithms.

A nearly yearlong process winnowed an initial field of 90 teams down to the 18 that competed last month. While most of the teams were composed of academics, there were also amateur hobbyists, including a medical doctor whose second love is electronics and a 28-year-old contract programmer with no formal education beyond high school.

For more: http://spectrum.ieee.org/telecom/wireless/radio-wrestlers-fight-it-out-at-the-darpa-spectrum-challenge

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A Survey on Device-to-Device Communication in Cellular Networks

http://arxiv.org/pdf/1310.0720v3.pdf

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The second phase of LTE-A

https://www.google.gr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&cad=rja&uact=8&ved=0CJIBEBYwCA&url=http%3A%2F%2Fwww.huawei.com%2Filink%2Fen%2Fdownload%2FHW_259010&ei=bXhPU_uPAsrPtAaT-YBg&usg=AFQjCNGqWt91brhtxabWq_-Zqb0QJqOTew&sig2=JNkzaW3ICzppRIs7f13Gaw&bvm=bv.64764171,d.Yms

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Design Aspects of Network Assisted Device-to-Device Communications

http://www1.ericsson.com/res/docs/2012/design-aspects-of-network-assisted-device-to-device-communications.pdf

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Fundamentals of Satellite Communications

http://www.ieee.li/pdf/viewgraphs/fundamentals_satellite_communication_part_1.pdf
http://www.ieee.li/pdf/viewgraphs/fundamentals_satellite_communication_part_2.pdf
http://www.ieee.li/pdf/viewgraphs/fundamentals_satellite_communication_part_3.pdf
http://www.ieee.li/pdf/viewgraphs/fundamentals_satellite_communication_part_4.pdf

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SATELLITE COMMUNICATION – AN INTRODUCTION

http://www.mu.ac.in/myweb_test/Satelight%20Comm..pdf

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Mobile Communications: Satellite Systems

http://paginas.fe.up.pt/~mleitao/CMOV/Teoricas/CMOV_SAT.pdf

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How Japan Plans to Build an Orbital Solar Farm

JAXA wants to make the sci-fi idea of space-based solar power a reality


Here Comes the Sun: Mirrors in orbit would reflect sunlight onto huge solar panels, and the resulting power would be beamed down to Earth.

Imagine looking out over Tokyo Bay from high above and seeing a man-made island in the harbor, 3 kilometers long. A massive net is stretched over the island and studded with 5 billion tiny rectifying antennas, which convert microwave energy into DC electricity. Also on the island is a substation that sends that electricity coursing through a submarine cable to Tokyo, to help keep the factories of the Keihin industrial zone humming and the neon lights of Shibuya shining bright.

But you can’t even see the most interesting part. Several giant solar collectors in geosynchronous orbit are beaming microwaves down to the island from 36 000 km above Earth.

It’s been the subject of many previous studies and the stuff of sci-fi for decades, but space-based solar power could at last become a reality—and within 25 years, according to a proposal from researchers at the Japan Aerospace Exploration Agency (JAXA). The agency, which leads the world in research on space-based solar power systems, now has a technology road map that suggests a series of ground and orbital demonstrations leading to the development in the 2030s of a 1-gigawatt commercial system—about the same output as a typical nuclear power plant.

It’s an ambitious plan, to be sure. But a combination of technical and social factors is giving it currency, especially in Japan. On the technical front, recent advances in wireless power transmission allow moving antennas to coordinate in order to send a precise beam across vast distances. At the same time, heightened public concerns about the climatic effects of greenhouse gases produced by the burning of fossil fuels are prompting a look at alternatives. Renewable energy technologies to harvest the sun and the wind are constantly improving, but large-scale solar and wind farms occupy huge swaths of land, and they provide only intermittent power. Space-based solar collectors in geosynchronous orbit, on the other hand, could generate power nearly 24 hours a day. Japan has a particular interest in finding a practical clean energy source: The accident at the Fukushima Daiichi nuclear power plant prompted an exhaustive and systematic search for alternatives, yet Japan lacks both fossil fuel resources and empty land suitable for renewable power installations.

Soon after we humans invented silicon-based photovoltaic cells to convert sunlight directly into electricity, more than 60 years ago, we realized that space would be the best place to perform that conversion. The concept was first proposed formally in 1968 by the American aerospace engineer Peter Glaser. In a seminal paper, he acknowledged the challenges of constructing, launching, and operating these satellites but argued that improved photovoltaics and easier access to space would soon make them achievable. In the 1970s, NASA and the U.S. Department of Energy carried out serious studies on space-based solar power, and over the decades since, various types of solar power satellites (SPSs) have been proposed. No such satellites have been orbited yet because of concerns regarding costs and technical feasibility. The relevant technologies have made great strides in recent years, however. It’s time to take another look at space-based solar power.

A commercial SPS capable of producing 1 GW would be a magnificent structure weighing more than 10 000 metric tons and measuring several kilometers across. To complete and operate an electricity system based on such satellites, we would have to demonstrate mastery of six different disciplines: wireless power transmission, space transportation, construction of large structures in orbit, satellite attitude and orbit control, power generation, and power management. Of those six challenges, it’s the wireless power transmission that remains the most daunting. So that’s where JAXA has focused its research.



Wireless power transmission has been the subject of investigation since Nikola Tesla’s experiments at the end of the 19th century. Tesla famously began building a 57-meter tower on New York’s Long Island in 1901, hoping to use it to beam power to such targets as moving airships, but his funding was canceled before he could realize his dream.

To send power over distances measured in millimeters or centimeters—for example, to charge an electric toothbrush from its base or an electric vehicle from a roadway—electromagnetic induction works fine. But transmitting power over longer distances can be accomplished efficiently only by converting electricity into either a laser or a microwave beam.

The laser method’s main advantages and disadvantages both relate to its short wavelength, which would be around 1 micrometer for this application. Such wavelengths can be transmitted and received by relatively small components: The transmitting optics in space would measure about 1 meter for a 1-GW installation, and the receiving station on the ground would be several hundred meters long. However, the short-wavelength laser would often be blocked by the atmosphere; water molecules in clouds would absorb or scatter the laser beam, as they do sunlight. No one wants a space-based solar power system that works only when the sky is clear.

But microwaves—for example, ones with wavelengths between 5 and 10 centimeters—would have no such problems in transmission. Microwaves also have an efficiency advantage for a space-based solar power system, where power must be converted twice: first from DC power to microwaves aboard the satellite, then from microwaves to DC power on the ground. In lab conditions, researchers have achieved about 80 percent efficiency in that power conversion on both ends. Electronics companies are now striving to achieve such rates in commercially available components, such as in power amplifiers based on gallium nitride semiconductors, which could be used in the microwave transmitters.

In their pursuit of an optimal design for the satellite, JAXA researchers are working on two different concepts. In the more basic one, a huge square panel (measuring 2 km per side) would be covered with photovoltaic elements on its top surface and transmission antennas on its bottom. This panel would be suspended by 10-km-long tether wires from a small bus, which would house the satellite’s controls and communication systems.

Using a technique called gravity gradient stabilization, the bus would act as a counterweight to the huge panel. The panel, which would be closer to Earth, would experience more gravitational pull down toward the planet and less centrifugal force away from it, while the bus would be tugged upward by the opposite effects. This balance of forces would keep the satellite in a stable orbit, so it wouldn’t need any active attitude-control system, saving millions of dollars in fuel costs.

The problem with this basic SPS configuration is its inconstant rate of power generation. Because the photovoltaic panel’s orientation is fixed, the amount of sunlight that hits it varies greatly as the geosynchronous satellite and Earth spin.

So JAXA has come up with a more advanced SPS concept that solves the solar collection problem by employing two huge reflective mirrors. These would be positioned so that between the two of them, they would direct light onto two photovoltaic panels 24 hours a day. The two mirrors would be free flying, not tethered to the solar panels or the separate transmission unit, which means that we would have to master a sophisticated kind of formation flying to implement this system. Space agencies have some experience with formation flying, most notably in the docking maneuvers performed at the International Space Station, but coordinating a formation flight involving kilometer-scale structures is a big step from today’s docking procedures.

We would also have to make several other breakthroughs before this advanced type of SPS could be built. We’d need very light materials for the mirror structures to allow for the formation flight, as well as extremely high-voltage power transmission cables that could channel the power from the solar panels to the transmission unit with minimal resistive losses. Such technologies would take years to develop, so if one or more nations do embark on a long-term project to exploit space-based solar power, they may employ a two-phase program that begins with the basic model while researchers work on the technologies that will allow for next-generation systems.

To generate the microwaves, researchers have proposed vacuum tubes such as magnetrons, klystrons, or traveling wave tubes, because their power conversion efficiency is reasonably high—typically 70 percent or higher—and they’re relatively inexpensive. Semiconductor amplifiers are getting better all the time, however; their efficiencies are going up, and their costs are coming down. Cost is important here because a 1-GW commercial SPS would have to include at least 100 million 10-watt semiconductor amplifiers.

To choose a microwave frequency for transmission, we have to weigh several factors. Low-frequency microwaves penetrate the atmosphere well, but they require very large antennas, which would make construction and maintenance more complicated. Frequencies in the range of 1 to 10 gigahertz offer the best compromise between antenna size and atmospheric attenuation. Within this range, 2.45 and 5.8 GHz are the potential candidates because they are in the bands set aside for industrial, scientific, and medical uses. Of these, 5.8 GHz seems particularly desirable because the transmitting antennas can be smaller.

Making a powerful beam of microwaves is important, of course, but the next step is a lot trickier: aiming the beam precisely so that it travels the 36 000 km to hit the rectifying antennas spot on.

Consider that the microwave transmission system would be composed of a number of antenna panels, each measuring perhaps 5 meters long, that would be covered in tiny antennas: In total, more than 1 billion antennas would likely be installed on a single SPS. Coordinating the microwaves generated by this vast swarm of antennas won’t be easy. To produce a single, precisely focused beam, the phases of the microwaves sent from all the antenna panels must be synchronized. That would be hard to manage, as these panels would move relative to each other.

This challenge of precisely directing a beam from a moving source is unique and hasn’t been solved by existing communication technologies. The beam must have very little divergence to prevent it from spreading out over too large an area. To send power at the 5.8-GHz frequency to a rectifying antenna, or rectenna, with a diameter of 3 km, the divergence must be limited to 100 microradians and the beam must have a pointing accuracy of 10 µrad.

JAXA’s solution involves a pilot signal that would be sent from the rectenna on the ground. As each individual antenna panel on the satellite received the pilot signal, it would calculate the necessary phases for its microwaves and adjust accordingly. The sum of all these adjustments is a tight beam that would zing down through the atmosphere to hit the rectenna. Such phase-adjusting technologies, known as retrodirective systems, have been used in small-scale antenna arrays in space, but additional work would be needed before they could coordinate several kilometers of orbital transmitters.

Once the beam reaches the receiving site, the rest of the process would be relatively easy. Arrays of rectennas would convert the microwave power to DC power with an efficiency greater than 80 percent. Then the DC power would be converted to AC and fed into the electrical grid.

When laypeople hear these orbital solar farms described, they often ask if it would be safe to send a powerful beam of microwaves down to Earth. Wouldn’t it cook whatever’s in its path, like food in a microwave oven? Some people have a grisly mental image of roasted seagulls dropping from the sky. In fact, the beam wouldn’t even be intense enough to heat your coffee. In the center of the beam in a commercial SPS system, the power density would be 1 kilowatt per square meter, which is about equal to the intensity of sunlight. As the regulatory limit for sustained human exposure to microwaves is typically set at 10 watts per square meter, however, the rectenna site would have to be a restricted area, and maintenance workers who enter that zone would have to take simple precautions, such as donning protective clothing. But the land outside the rectenna site would be perfectly safe. At a distance of 2 km from its center, the beam’s power density will have already dropped below the regulatory threshold.

In 2008, on a mountaintop on Hawaii’s main island, a rectenna received a beam of microwaves sent from the slopes of a volcano on the island of Maui, about 150 km away. That demonstration project, led by former NASA physicist John Mankins and recorded for a show on the Discovery Channel, was modest in its ambitions: Only 20 W of power were generated by the solar panels on Maui and beamed across the ocean. This setup was far from ideal because the microwaves’ phases were disturbed during this horizontal transmission through the dense atmosphere. Most of the power was lost in transmission, and less than a microwatt was received on the Big Island. But the experiment did demonstrate the general principle to an admiring public. And it’s worth remembering that in a space-based system, the microwaves would pass through dense atmosphere only for the last few kilometers of their journey.

In Japan, we are now planning a series of demonstrations for the next few years. By the end of this year, researchers expect to perform a ground experiment in which a beam of hundreds of watts will be transmitted over about 50 meters. This project, funded by JAXA and Japan Space Systems, will be the world’s first demonstration of high-power and long-range microwave transmission with the critical addition of retrodirective beam control. The microwave transmitter consists of four individual panels that can move in relation to one another in order to simulate antenna motion in orbit. Each panel, measuring 0.6 meter by 0.6 meter, contains hundreds of tiny transmitting antennas and receiving antennas to detect the pilot signal, as well as phase controllers and power management systems. Each panel will transmit 400 W, so that the total beam will carry 1.6 kW; in this early-stage experiment, we expect the rectenna to have a power output of 350 W.

Next, JAXA researchers hope to conduct the first microwave power transmission experiment in space, sending several kilowatts from low Earth orbit to the ground. This step, proposed for 2018, should test out the hardware: We hope to demonstrate microwave beam control, evaluate the system’s overall efficiency, and verify that the microwave beam doesn’t interfere with existing communications infrastructure. We also have some space science to conduct. We want to be sure that the intense microwave beam isn’t distorted or absorbed by the plasma of the ionosphere, the upper-atmosphere layer that contains electrically charged particles. We’re pretty sure that the beam won’t interact with this plasma, but our hypothesis can be confirmed only in the space environment.

If all goes well with these initial ground and space demonstrations, things will really start to get interesting. JAXA’s technology road map calls for work to begin on a 100-kW SPS demonstration around 2020. Engineers would verify all the basic technologies required for a commercial space-based solar power system during this stage.

Constructing and orbiting a 2-megawatt and then a 200-MW plant, the next likely steps, would require an international consortium, like the ones that fund the world’s giant particle physics experiments. Under such a scenario, a global organization could begin the construction of a 1-GW commercial SPS in the 2030s.

It would be difficult and expensive, but the payoff would be immense, and not just in economic terms. Throughout human history, the introduction of each new energy source—beginning with firewood, and moving on through coal, oil, gas, and nuclear power—has caused a revolution in our way of living. If humanity truly embraces space-based solar power, a ring of satellites in orbit could provide nearly unlimited energy, ending the biggest conflicts over Earth’s energy resources. As we place more of the machinery of daily life in space, we’ll begin to create a prosperous and peaceful civilization beyond Earth’s surface.

This article originally appeared in print as “It’s Always Sunny in Space.”

source: http://spectrum.ieee.org/green-tech/solar/how-japan-plans-to-build-an-orbital-solar-farm