Senin, 31 Mei 2010

4G wireless: It's fast, but outstripped by hype

4G wireless: It's fast, but outstripped by hype

Sprint HTC Evo 4G. (Courtesy Sprint)


NEW YORK – Cell phone companies are about to barrage consumers with advertising for the next advance in wireless network technology: "4G" access. The companies are promising faster speeds and the thrill of being the first on the block to use a new acronym.

But there's less to 4G than meets the eye, and there's little reason for people to scramble for it, at least for the next few years.

Sprint Nextel Corp. is the first carrier to beat the drum for fourth-generation wireless technology. It's releasing its first 4G phone, the EVO, this week.

In the fall, Verizon Wireless will be firing up its 4G network in 25 to 30 cities, and probably will make a big deal of that. A smaller provider, MetroPCS Communications Inc., is scheduled to introduce its first 4G phone around the same time.

So what is 4G?

Broadly speaking, it's a new way to use the airwaves, designed from the start for the transmission of data rather than phone calls. To do that, it borrows aspects of the latest generation of Wi-Fi, the short-range wireless technology.

For consumers, 4G means, in the ideal case, faster access to data. For instance, streaming video might work better, with less stuttering and higher resolution. Videoconferencing is difficult on 3G and might work better on 4G. Multiplayer video games may benefit too.

Other than that, it's difficult to point to completely new uses for 4G phones — things they can do that 3Gphones can't.

Instead, the upgrade to 4G is more likely to enhance the things you can already do with 3G, said Matt Carter, president of Sprint's 4G division.

"View it as the difference between watching regular TV and high-definition TV," Carter said. "Once you've experienced high-definition TV it's hard to go back to standard TV. It's the same sort of thing here."

So the improvement from 3G to 4G is not as dramatic as the step from 2G to 3G, which for the first time made real Web browsing, video and music downloads practical on phones. The introduction of 3G started in earnest about five years ago, but it isn't complete — AT&T Inc. and T-Mobile USA still have little rural 3G coverage, for instance.

There's an important caveat to the claim that 4G will be faster, as well. It will definitely be faster than the 3Gnetworks of Sprint and Verizon Wireless — about four times faster, initially. But the other two national carriers, AT&T and T-Mobile, are upgrading their 3G networks to offer data-transfer speeds that will actually be higher than the speeds 4G networks will reach this year or next.

That means that rather than focusing on real speeds, Sprint and Verizon will try to frame their marketing around the "4G" term, said Dan Hays, who focuses on telecommunications at management consulting firm PRTM.

"It's a terrible story from a consumer standpoint, because it's tremendously confusing," he said.

AT&T and T-Mobile are able to upgrade their 3G networks because they use a different 3G technology than Verizon and Sprint, which have maxed out their 3G speeds. Taking the step to 4G is natural for Verizon and Sprint, especially because they have new chunks of the radio spectrum that they want to take advantage of.

The fact that Verizon Wireless and Sprint are adding fresh spectrum may be more important than the fact that they are using it for 4G service. No matter if used for 4G or 3G, new spectrum means the companies can accommodate more data-hungry devices such as smart phones.

AT&T's network is already staggering under data congestion caused by the iPhone in New York and San Francisco. The carrier has made relieving the congestion a top priority this year, and its 3G upgrades are part of that process. (As an aside, there is a lot of talk of a coming "iPhone 4G." Apple Inc. will most likely release the fourth generation of the iPhone for AT&T's network this summer, but it's virtually certain that it will not be able to use a 4G wireless network. It likely won't be called the "iPhone 4G" either.)

There's another, more subtle benefit to 4G. While it's not always faster than the best 3G when it comes to helping you download a big file in less time, it is definitely faster in the sense that it takes less time to initiate the flow of data to you. What that means is that 4G is faster for quick back-and-forth communications. You wouldn't notice this when surfing the Web or doing e-mail: We're talking delays of 0.03 second rather than 0.15 second. But it could mean that 4G will work better for multiplayer gaming, where split-second timing is important. Even phone calls could benefit from shorter audio delays.

Sprint and Verizon are taking different routes in 4G. Sprint owns a majority of Clearwire Corp., which is building a network using WiMax technology. Once seen as very promising, WiMax looks set to be a niche technology, and WiMax devices like the Sprint EVO phone won't be able to use networks built using the dominant 4G standard, called LTE, for Long Term Evolution. Verizon and MetroPCS plan to use LTE, as does AT&T, starting next year. T-Mobile says it will probably use LTE eventually. Even Sprint hasn't ruled out using LTE eventually, because the technology has huge momentum.

In five years or so, many phones are likely to have 4G capabilities, but they'll complement it with 3G. Rather than a sudden revolution, consumers are likely to experience a gradual transition to the new technology, with increasing speeds. But for now, 4G is no magic bullet.

"It's an important thing for the industry," said Bill Davidson, senior vice president of marketing and investor relations at wireless technology developer Qualcomm Inc. "It's absolutely needed. ... But I just think some of this has gotten a bit ahead of itself in terms of expectations for consumers."

http://news.yahoo.com/s/ap/20100530/ap_on_hi_te/us_tec4g_hype

Kamis, 27 Mei 2010

USAF vehicle breaks record for hypersonic flight

USAF vehicle breaks record for hypersonic flight

In this image provided by the U.S. Air Force, an X-51A Waverider rides under the wing of a B-52 Stratofortress, Dec. 9, 2008. A similar X-51A successfully launched from a B-52 Stratofortress, Wednesday May 26, 2010. (AP Photo/U.S. Air Force - Mike Cassidy)

X-51A WaveriderAP – In this image provided by the U.S. Air Foce an X-51A Waverider rides under the wing of a B-52 Stratofortress …
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WASHINGTON – An experimental aircraft has set a record for hypersonic flight, flying more than 3 minutes at Mach 6 — six times the speed of sound.

The X-51A Waverider was released from a B-52 Stratofortress off thesouthern California coast Wednesday morning, the Air Force reported on its website. Its scramjet engine accelerated the vehicle to Mach 6, and it flew autonomously for 200 seconds before losing acceleration. At that point the test was terminated.

The Air Force said the previous record for a hypersonic scramjet burn was 12 seconds.

[Related: Secret X-37B space plane spotted by amateur skywatchers]

"We are ecstatic to have accomplished many of the X-51A test points during its first hypersonic mission," said Charlie Brink, an X-51A program manager with the Air Force Research Laboratory at Wright-Patterson Air Force Base, Ohio.

"We equate this leap in engine technology as equivalent to the post-World War II jump from propeller-driven aircraft to jet engines," Brink said.

The Waverider was built for the Air Force by Pratt & Whitney Rocketdyne and Boeing Co.

Joe Vogel, Boeing's director of hypersonics, said, "This is a new world record and sets the foundation for several hypersonic applications, including access to space, reconnaissance, strike, global reach and commercial transportation."

Four X-51A cruisers have been built for the Air Force, and the remaining three will be tested this fall.

"No test is perfect," Brink said, "and I'm sure we will find anomalies that we will need to address before the next flight."

http://news.yahoo.com/s/ap/20100527/ap_on_sc/us_hypersonic_flight

Mystery Spirals on Mars Finally Explained

Mystery Spirals on Mars Finally Explained


Solved: The 40-year mystery of the Martian ice capAFP/NASA – An undated handout photo of a view of the north polar region of Mars from orbit. Astronomers on Wednesday …

Huge troughs curving outward from the north pole of Mars like the arms of a pinwheel were not carved into the polar ice caps by some mysterious force, researchers have discovered. Instead, the shifting pattern arose from a long process of formation and erosion that gave it the appearance of slowly moving and spiraling inward over time.

A similarly snail-like process gave rise to the Chasma Boreale canyon that cuts into the side of the giant pinwheel pattern, known as the north polar layered deposits (NPLD). The unveiling of the origins of the canyon and NPLD came courtesy of ground-penetrating radar carried by two Mars orbiters.

Scientists had previously favored the idea that a natural force recently carved both the canyon and pinwheel pattern into older geological deposits. But they could not test their theories beyond what they could see on the Martian surface, as if trying to judge a book by its cover.

"Radar is like opening the book; we can read each page now," said Isaac Smith, a planetary scientist at the University of Texas Austin. "People were looking at the outside and thinking they knew what the book was about, but they didn't."

Such technology allowed scientists to take 2-D cross-section images of the troughs and reveal the layers within the walls, like snapshots in time going back through the red planet's history. Radar also helped trace reflective markers that followed the geometry of underground structures to build up a 3-D sense of the layers.

The radar studies do not answer the riddle of what changes in the Martian atmosphere spurred the formation of both the canyon and the younger spiraling troughs. But they do give scientists a new understanding of the timing of the processes that allow the wind and sun to shape the Martian surface over a certain period, and that may lead to more evidence-based climate models for the red planet.

Not built in a day

The Chasma Boreale appears to cut into the side of the ice-rich polar layered deposits which sprawl across 621 miles (1000 kilometers) and are about 1.2 miles (2 kilometers) thick. But the radar studies showed that the massive canyon formed long before the appearance of the shallower troughs which make up the spiraling arms.

Some researchers had suggested that pressure-induced melting or sub-ice volcanic activity caused the canyon to appear. Yet the canyon's birth turned out to result more from the slow workings of climate and time, rather than rapid or catastrophic forces.

"There were many hypotheses about the Chasma Boreale, and all assumed it was a recent feature cut into the polar ice," said Jack Holt, a geophysicist at the University of Texas, Austin. "But now we know it's an old feature, and you can interpret the stratigraphy in that context."

Holt led the radar study on the Chasma Boreale, while his colleague Smith focused on the spiral troughs. Their two studies appear in the May 27 issue of the journal Nature.

Both the Chasma Boreale and the younger troughs formed on top of an older polar ice cap. Layers of water-ice and grit began depositing, and soon an early form of the canyon appeared. But it wasn't alone; a similarly-sized canyon also began to take shape.

Then something in the Martian climate caused the deposits to stop. Erosion then took over, as the wind wore at the surface and the sun caused some ice to sublimate and turn directly into vapor. There was no evidence of water melt from the radar studies, Holt told SPACE.com.

Eventually the layers began depositing again on top of one another, and one of the canyons ended up getting filled in. But natural forces such as the wind somehow spared the Chasma Boreale by preventing deposits from filling it, and helped preserve the canyon that today stretches 311 miles (500 kilometers) long and 62 miles (100 kilometers) wide.

"The [canyon formation] happened for some time with no good age constraints," Holt said. "That was about 75 percent of the way through the history of this, but then the troughs started forming. We don't know why."

Picking up good migrations

The younger, shallower troughs began to form sometime between 2.49 million years and 467,000 years ago. They represented depressions on top of about three quarters of built-up polar layered deposits, but they didn't just sit still.

Instead, a combination of wind and perhaps sun erosion began to wear away at the southern, equator-facing sides of the polar layered deposits. Wind then carried a trickle of eroded material to the northern, polar-facing sides of the deposits.

As a result, the troughs appeared to slowly spiral inward as they crept northward toward the pole. That appearance of movement has strong resemblance to how sand dunes seem to move over time, Smith said.

"Radar shows that three quarters of the ice has been sitting there, but the surface was altered by wind," Smith explained. "Some troughs have moved as much as 65 kilometers [40 miles], and many moved much less."

More material also accumulates on top of the deposits as the spiral pattern tightens, Holt said. That means the deposits get thicker and higher all the time.

More climate mysteries

Understanding how the north polar ice cap patterns appeared may also help scientists understand the global climate of Mars. Holt and Smith hope to continue examining the patterns of accumulation and try to understand why snow or frost built up unevenly to create the polar layered deposits.

"That tells us a story about the wind and possibly the sun," Smith said. "That's the continuing story."

Researchers can plug their evolved understanding of the natural forces into Mars climate models to make the models more realistic. And better models might help reconstruct how water ice transfers between the poles and the mid or lower latitudes of the red planet, through sublimation and frost or snow.

"You can then start placing age constraints on ice deposits at lower to mid latitudes, which are more accessible to robot and human missions," Holt pointed out.

Future work might also solve the mystery of the south polar layered deposits, which also resemble the spiral pattern of their north polar cousins. But unlike in the north, the south polar layered deposits don't appear to move.

Smith speculated that a colder climate and higher elevation at the south polar ice cap may translate into stickier frozen material and weaker winds. Holt also noted that the southern region appears older, so that perhaps the climate simply did not allow for movement during the time in which the deposits formed.

What lies beneath

Part of the reason that the southern polar ice cap remains more mysterious is that radar does not work as well in that region. Reflective markers or structures beneath the north polar layered deposits helped the radar studies trace the geometry and layers underground, but such markers appear less common in the south.

Still, Holt and Smith praised the radar carried by the Mars orbiters as the crucial components that solved at least the origins of the north polar layered deposits. Such equipment has been used in Antarctica since the 1970s, but did not fly out to Mars until the past decade.

The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on the Mars Express orbiter can probe deep beneath the surface with less resolution, while the Mars Reconnaissance Orbiter's SHAllow RADar (SHARAD) has both higher frequency and bandwidth with shallower penetration that can still examine the underground layers and structure of the polar layered deposits.

Such powerful tools could begin to make a case for flying even better radar out to Mars someday.

"In the future, we could probably learn even more about the subsurface," Holt said. "There's still more we could learn with a newer, better radar."

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http://news.yahoo.com/s/space/20100526/sc_space/mysteryspiralsonmarsfinallyexplained