Tag Archive for MIMO

| March 1, 2018
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MIMO Antennas Explained

MIMO Antennas ExplainedWave 2 of the IEEE 802.11ac Wi-Fi standard has been out for a while now. Wave 2 Wi-Fi can support speeds up to 2.3 Gbps. One of the techniques used to generate the increased speeds of the 802.11ac networks is multi-spacial streams or several streams of the same Wi-Fi signal radiating out from several antennas. The multiple antennas are the most noticeable indicator that an access point is 802.11ac capable, especially in the consumer market.

Multiple-Input Multiple-Output

The technology behind using several antennas is called Multiple-Input Multiple-Output (MIMO). MIMO antennas have two or more antennas in a single physical package and are designed for use in IEEE 802.11n/ac Wi-Fi networks. MIMO makes antennas work smarter by utilizing multiple antennas to combine data streams arriving from different paths and at different times to increase data throughput and range compared to a single antenna using the same radio transmit power. By transmitting multiple data streams at the same time, wireless capacity is increased.

Additionally MIMO antennas improve link reliability and experience less fading than a single antenna system. MIMO antennas use spatial diversity technology, which puts surplus antennas to good use. When there are more antennas than spatial streams, the antennas can add receiver diversity and increase range.

Radio-wave multipath

Asus AC5600 routerMIMO technology takes advantage of a natural radio-wave phenomenon called multipath to improve wireless performance. In the past, multipath caused interference and slowed down wireless signals. With this iteration, Wi-Fi takes advantage of multipath. With multipath transmitted information bounces off walls, ceilings, and other objects, reaching the receiving antenna multiple times via different angles and at slightly different times

MIMO technology takes a single data stream and breaks it down into several separate data streams and sends it out over multiple antennas. This technique provides redundancy. The receiving MIMO antenna will “look” at each stream being sent to determine the strongest one to choose.

Legacy wireless devices use Single-Input Single-Output (SISO) technology. These devices cannot take advantage of multipath, and can only send or receive one spatial stream at a time.

802.11ac Wave 2 MIMO

A new version of MIMO has been developed. TechHive reports that Multi-user multiple-input, multiple-output (MU-MIMO) technology, enables AP’s to transmit and receive data from multiple Wi-Fi devices at the same time. Although the devices must also support MU-MIMO to utilize it, they aren’t required to have multiple antennas.

MU-MIMO was introduced with 802.11ac Wave 2. Wave 2 MU-MIMO support is required on both the access point and client device to work. It operates in the downstream direction, access point to the client, and allows an access point to transmit to multiple client devices simultaneously. This means networks with a dense number of users in an area, such as public Wi-Fi hotspots, could be able to handle more Wi-Fi devices.

TechHive warns the biggest caveat of MU-MIMO is it doesn’t directly improve the wireless speeds of uplink connections.

Only a handful meet the criteria today

MU-MIMO technologyIt’s also important to note that the only way to gain the full benefit of MU-MIMO is when the technology is supported on both the access point and the device that’s connecting to the AP. So in addition to having an 802.11ac adapter onboard, the client must explicitly support MU-MIMO—there are only a handful of adapters that meet that criteria today.

Finally, TechHive says MU-MIMO works best with stationary Wi-Fi devices. If users are walking around while watching a video on a smartphone or tablet, they are not going to get the full benefit of MU-MIMO even if that device supports it. Your router might even limit that connection to using SU-MIMO, so that the connection doesn’t negatively impact stronger MU-MIMO connections.

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The client issue is the main reason 802.11ac Wave 2 will not be widely used in the enterprise. it is a big issue to keep the clients up to date to match the AP version. In fact, Zeus Kerravala at NetworkWorld points out that many of the high-volume manufacturers, such as Apple and Samsung, are skipping 802.11ac Wave 2 and plan to support IEEE 802.11ax in the future.

So skip Wave 2 devices in the enterprise and stick to an 802.11ac Wave 1 AP, and get exactly the same performance as its higher-priced Wave 2 counterpart.

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Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.

Category: wi-fi | Tags: , , , , , , , , ,
| November 7, 2013
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802.11ac Wi-Fi – Don’t Bother Yet

802.11ac Wi-Fi - Don't Bother YetThe new iPads are here! The new iPads are here! There’s no 802.11ac here! But that’s expected. Experienced Apple watchers know that Apple likes to let new radio technologies mature before they integrate them into their new idevices. So that means most enterprises can slow their plans to upgrade their Wi-Fi to the new standard according to Kevin Fitchard at GigaOM.

The new iPads are hereThe latest Apple (AAPL) tablet doesn’t sport the new soon-to-be-completed IEEE 802.11ac standard, even though Apple’s latest generation routers, PCs, and laptops all support it. GigaOM reports Apple is providing is a speed boost to the now thoroughly established 802.11n networking standard in the form of multiple-input multiple-output (MIMO) smart antenna technology. Like many Wi-Fi routers on the market, the iPad Air has dual antennas, allowing it to wend two parallel paths over the unlicensed airwaves. The MIMO implementation will double the speeds at which the iPad can access Wi-Fi networks, according to Apple.

The Wi-Fi Alliance only began certifying commercial 802.11ac devices in June, and even those devices only incorporate partial versions of the full 802.11ac spec. The IEEE isn’t expected to fully complete the standard until 2014. Very few smartphones and tablets have ac embedded as of yet, though the technology is making its way into consumer and enterprise routers and PCs, including Apple’s newest MacBooks and iMacs.

iPad AirBut waiting another year for 802.11ac-enabled iPhones and iPads also means we’ll probably have to wait another year before we see wide-scale adoption of the standard in public hotspots and access points. Unlike in the home, most outdoor and public Wi-Fi connections are made over mobile devices, not PCs.

In an interview with GigaOM, Boingo VP of corporate communications Christian Gunning said it hasn’t turned up 802.11ac in any of its hundreds of thousands of owned and managed hotspots yet, simply because it’s seeing very few devices with ac radios trying to access its network.

higher-powered 802.3at Power over EthernetFierceCIO‘s Paul Mah offers more reasons to delay the roll-out of 802.11ac. The advanced 802.11ac radio is more power-hungry than earlier iterations of Wi-Fi. So it will more likely need the use of the higher-powered 802.3at Power over Ethernet (PoE) to run 802.11ac with all its bells and whistles. It is possible that businesses still on 802.3af PoE (rb- Majority) may well have to incur extra infrastructure costs to deploy 802.11ac today. Mr. Mah contends that it is yet to be seen if improved 802.11ac chipsets will allow firms to stick with legacy PoE. (rb- For a refresher on PoE, check out these posts 802.3af and 802.3at)

Another consideration according to FierceCIO is clients. The handful of business-grade 802.11ac wireless APs on the market today typically support three spatial streams, which allows for a (theoretical) maximum data rate of 1.3Gbps in the 5GHz band. Though this is a significant improvement over 450 Mbps 802.11n, the dearth of 802.11ac client devices renders this a moot point. Some will argue that Apple did incorporate 802.11ac into the new MacBook Air laptops.  However, they did not include it in the new iPads, or the iPhone 5S and iPhone 5C smartphones. And with no smartphones or tablets equipped with 802.11ac capabilities today, this does make deploying it a rather pointless strategy for BYOD.

802.11ac "second wave"Finally, Mr. Mah points out that while 1.3Gbps is a good speed to have, we should keep in mind that 802.11ac does have a theoretical maximum speed of 7 Gbps. A “second wave” of 802.11ac that implements four or more data streams for much faster speeds should be arriving in the second half of 2014. He says current signs are that this second wave of 802.11ac devices might need new processor chips–which means you will have to buy new 802.11ac hardware to benefit.

GigaOM’s Fitchard stresses Apple’s influence when it comes to popularizing new technology, he says the iPhone and the iPad’s reach shouldn’t be underestimated. As an example, new Passpoint-certified phones have been out for more than a year, but it wasn’t until Apple started offering support for Passpoint’s automatic login technology in iOS7 that the wireless industry took notice. It was only after Apple made iOS7 publicly available, that Boingo started Passpoint trials.

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I’m not saying 802.11ac is a bad thing, but enterprises need to ignore the hype cycle and make decisions that are best for them and not the multi-billion dollar networking industry. IMHO 802.11ac is still immature, there are few devices out there that can fully take advantage, the full feature set is not fully implemented in silicon and you finished the upgrade to 802.11n yet?

What to do?

What does your wired network look like? Are you still connecting your AP’s at 100 Mbps? That is a bottleneck with 802.11n.

Do you have enough juice? What is your PoE status? Do you have enough PoE+ ports? Are they being used for just an access port – wasting the extra costs of a PoE port?

Both switches cost money, is there a budget available for these items or is IT going to spend an operational budget to address a structural issue?

 

Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.

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| October 17, 2013
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A Close Look at 802.11ac Wi-Fi

TA Close Look at 802.11ac Wi-Fiech pundits argue that the new Wi-Fi standard 802.11ac will replace wired gigabit Ethernet networking. 802.11ac is a supercharged version of 802.11n, offering link speeds ranging from 433 Mbps, up to multiple gigabits per second.

Wi-FiTo make 802.11ac dozens of times faster than 802.11n, the new standard works exclusively in the 5GHz band uses a huge chunk of bandwidth (80 or 160MHz), operates in up to eight spatial streams (MIMO), and a technology called beamforming.

At its core, 802.11ac is essentially an updated version of 802.11n, according to Sebastian Anthony the author of an ExtremeTech article “What is 802.11ac WiFi, and how much faster than 802.11n is it?” 802.11n was a huge performance increase over 802.11a and g. 802.11n introduced some key technologies that brought massive speed boosts. Where 802.11n had support for four spatial streams (4×4 MIMO) and a channel width of 40MHz, 802.11ac can use eight spatial streams and has channels up to 80MHz wide, which can be combined to make 160MHz channels. This means that 802.11ac has 8 x 160MHz of spectral bandwidth to play with, versus 4 x 40MHz – a huge difference that allows 802.11ac to send vast amounts of data across the airwaves.

Beamforming

What is new in Wi-Fi

802.11ac also introduces 256-QAM modulation (up from 64-QAM in 802.11n), which sends 256 different signals over the same frequency by shifting each signal to a slightly different phase. In theory, this quadruples the spectral efficiency of 802.11ac over 802.11n. Spectral efficiency is a measure of how well a given wireless protocol/modulation/multiplexing technique uses the bandwidth available to it.

802.11ac also introduces standardized beamforming Matthew Gast, Director of Product Management at AeroHive Networks published an article, “Investing in Beamforming: Is it worth it?” that explains beamforming.

Aerohive logoRather than transmitting a radio signal in all directions, beamforming figures out where the receiver is, and focus the energy towards the receiver. Instead of spraying radio energy all over the place, send packets as a “rifle shot” directly to the receiver’s antenna Mr.Gast explains.

Beamforming is a two-step process: First, figure out how to “aim” the transmission at the receiver, and second, send the transmission. With beamforming, a transmitter is betting that by paying the cost of the channel measurement process, the data transmission that follows will speed up enough to pay off the cost.

802.11n Beamforming was non-standardized, in 802.11ac, there is only one method of beamforming, called the Null Data Packet (NDP). (rb- Read the AeroHive article for a full description of NDP)

Aerohive’s Gast concludes that by steering the energy towards a receiver, beamforming enables you to take a step up to a higher data rate. Mr. Gast estimates that 802.11-based beamforming gives you a 3-5 dB gain.

802.11ac is speedyIn theory, at the 5GHz band with beamforming, 802.11ac should have the same or better range than 802.11n  However, Mr. Anthony says the 5GHz band, has less penetration power so it doesn’t have the same range as 2.4GHz (802.11b/g). The ExtremeTech article concludes that’s an acceptable trade-off: there simply isn’t enough spectral bandwidth in the cluttered 2.4GHz band to allow for 802.11ac’s gigabit-level speeds.

ExtremeTech‘s Anthony calculates there are two answers to how fast is Wi-Fi 802.11ac, the theoretical max speed, and the practical max speed that mere mortals will get surrounded by lots of signal-attenuating obstacles.

He calculates the theoretical max speed of 802.11ac is eight 160MHz 256-QAM channels, each of which is capable of 866.7Mbps – a grand total of 6,933Mbps, or just shy of 7Gbps. That’s a transfer rate of 900 megabytes per second. Compare this with 802.11n’s max theoretical speed, which was 600Mbps. He then says in practice, the current max speed of 802.11ac devices is 1.7Gbps.

ExtremeTech points out there will be a second wave of 802.11ac devices – due in 2014 after the standard is finalized – before 160MHz channels and multi-gigabit speeds become a reality. The max speed over an 80MHz channel is 433.3Mbps, and there aren’t any 802.11ac chipsets that support up to eight streams.

Broadcom logoKevin Fitchard at GigaOM reports that recently the Wi-Fi Alliance kicked off its 802.11ac certification program. First to get the official Wi-Fi stamp of approval was the Samsung Mega 6.3, followed by two other Samsung models.

As with the 802.11n certification process, the Wi-Fi equipment makers are moving faster than the standards bodies. The IEEE is actually still putting the finishing touches on the 802.11ac standard, which is not due until 2014.

Wi-Fi certifiedThe Wi-Fi Alliance expects the first batch of ac devices will support speeds of 433 Mbps and progress into more advanced levels of the standard. The Alliance has pre-certified systems from companies like Broadcom (BRCM), Qualcomm (QCOM), Realtek, and Marvell (MRVL). Cisco (CSCO) was one of the first vendors to get an access point certified.

“AC is going into mobile and portable devices first…,” Wi-Fi Alliance Marketing and Program Management Director Kelly Davis-Felner said. ABI Research estimates that 40 percent of all ac devices shipped in 2013 will be handsets.

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Wi-Fi will replace wired Ethernet networkingWhile tech pundits argue that the new 802.11ac Wi-Fi will replace wired gigabit Ethernet networking at home and in the office. While the consumerization of IT and BYOD are strong forces, the life-cycle of cabling infrastructure is 25 years, a cost not lightly abandoned in the walls. it is more likely to happen at home first. Who wants all the crappy wires running all over the house?

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Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.

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| September 3, 2013
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802.11ac Wi-Fi Clears the Way for Collaboration

802.11ac Wi-Fi Clears the Way for CollaborationThe emerging gigabit 802.11ac, Wi-Fi standard is the current darling of the hype machine. The standard will be finalized in February 2014. However, that has not stopped manufacturers from shipping 802.11ac routers, access points, and mobile devices. Shortel (SHOR) recently provided their opinion on what this means for your business.

IEEE 802.11acThe article points out that more people are using mobile apps and devices. Shortel calculates that a typical worker may have three IP addresses, while digital natives may have up to six IP addresses. These stats suggest that mobility has become a must-have and the author claims that 802.11ac can meet the needs of increasing mobility because 802.11ac is faster, more reliable, and delivers more Wi-Fi capacity. 802.11ac is:

  • Faster – 802.11ac is three times faster than 802.11n Wi-Fi. 802.11ac will deliver up to 1.3 Gbps, which is about three times faster than 802.11n. This capacity will be ideal for real-time applications, such as IP voice and streaming video. Faster data throughput means better battery life for mobile devices, too.
  • More reliable – 802.11ac is more reliable with less interference. 802.11ac operates at 5 GHz, which is far less crowded than the 2.4 GHz band that by 802.11b/g/n access points — as well as cordless phones, automatic garage door openers, and other home appliances. That means that there’s less interference from other Wi-Fi-enabled devices, which will result in a better user experience.
  • Improved throughput. 802.11ac uses multiple antennas for transmitting and receiving RF signals, and that means better data throughput. More specifically, MIMO, or Multiple-Input and Multiple-Output, is key to providing wireless performance that is more switch-like, compared to the shared media nature of 802.11n.

W-Fi Alliance logoShortel believes that Gigabit Wi-Fi can be a real asset for unified communications, streaming media, and other bandwidth-hungry apps. They plan to use the greater capacity of 802.11ac to support more devices and more apps. In the workplace, teams want to engage and share without hassle using modern collaboration tools with the devices of their choice creating the need for BYOD.

The newest generation of workers are digital natives, who are more inclined to use videoconferencing for quick chats or to share ideas. In addition, many people use tablets to stream media, and more organizations are turning to streaming media over Wi-Fi for digital signage, training, company meetings, and customer support. And those bandwidth-hungry applications will love the new gigabit Wi-Fi.

Wave 1 802.11ac only offers incremental benefits over 802.11nShoretel reassures those that have deployed an 802.11n WLAN recently, you don’t need to be in a hurry to move to 802.11ac. You can be confident in the investment that you made, as the first-generation 802.11ac will offer only incremental benefits over 802.11n. But if you are replacing old Wi-Fi or expanding your wireless LAN or looking to downsize your wired network in favor of wireless, you should weigh the options between 802.11n and the new 802.11ac.

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802.11ac will only get faster, the theoretical max speed of 802.11ac is just shy of 7Gbps, which you will never see in the wild, but don’t be surprised to see link speeds of 2Gbps or more in the next few years. At 2Gbps, you’ll get a transfer rate of 256MB/sec.

To reach such Wi-Fi speeds, chipset and device makers will have to figure out how to make second-generation chipsets with four or more 802.11ac streams in software and hardware. The engineers at Broadcom (BRCM), Qualcomm (QCOM), Marvell (MRVL), and Intel (INTC) are already working on ways to implementing four and eight-stream 802.11ac solutions. A lot of work will need to be done by the chipset and device makers to make sure that advanced features, such as beamforming, comply with the standard and are interoperable with other 802.11ac devices.

In general, then, you can certainly expect some impressive speeds from 802.11ac in situations where you don’t need the performance and reliability of wired GigE. But I do not believe that 802.11ac will replace a wired Gigabit Ethernet network just yet.

What do you think?

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Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.

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| July 12, 2011
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Put a Hemi in Your Mobile Phone

Put a Hemi in Your Mobile PhoneResearchers at the University of Michigan have found a way to put a hemi into your next mobile phone. While it is not the legendary MOPAR Hemi engine, it is a hemispherical antenna. U of M researchers have figured out how to mass-produce antennas so small that they approach the fundamental minimum size limit for their bandwidth, or data rate, of operation according to the U of M News Service.

University of Michigan logoThe antenna is typically the largest wireless component in mobile devices. Shrinking it could leave more room for other gadgets and features, Anthony Grbic, an associate professor in the Department of Electrical Engineering and Computer Science said.

Mr. Grbic and Stephen Forrest, a professor in the departments of Materials Science and Engineering and Physics, led the development of the hemisphere-shaped antennas, which can be manufactured with innovative imprint processing techniques that are rapid and low-cost. The finished product is 1.8 times the fundamental antenna size limit established in 1948 by L.J. Chu. The dimensions of this limit vary based on an antenna’s bandwidth.

U of M hemispherical antenna“Ever since the Chu limit was established, people have been trying to reach it,” Mr. Grbic said in the article. “Standard printed circuit board antennas don’t come close. Some researchers have approached the limit with manually built antennas, but those are complicated and there’s no efficient way to manufacture them. We’ve found a way to cut the antenna’s size while maximizing its bandwidth, using a process that’s amenable to mass production.”

The researchers’ prototype operates at 1.5 gigahertz, in the frequency range of Wi-Fi devices as well as cordless and mobile phones. The antenna is 70 percent efficient and ten times smaller than conventional antennas, Mr. Grbic said. It has three times the conductivity of similar devices produced by 3-D ink-jet printing techniques, a process that serially writes the antenna geometry.

This new method is a very general process, said Carl Pfeiffer, a doctoral student in the Department of Electrical Engineering and Computer Science and first author of a paper on the work, “Novel Methods to Analyze and Fabricate Electrically Small Antennas” will be presented at the 2011 IEEE International Symposium on Antennas and Propagation.

“It can be used to fabricate antennas that are of a wide variety of sizes, shapes, frequencies, and designs,” Mr. Pfeiffer said. “Basically if you tell me the data rate that is required for a particular application, I can make an antenna that does this while at the same time being as small as possible.”

Internet of ThingsThe prototype was made in the College of Engineering’s Lurie Nanofabrication Facility. The work was funded by the Department of Education’s Graduate Assistance in Areas of National Need program, the National Science Foundation, and the U.S. Air Force Office of Scientific Research.

The researchers believe this development could lead to new generations of wireless consumer electronics and mobile phones that are either smaller or can perform more functions. Beyond consumer electronics, this work could be useful in wireless sensing and military communications. Wireless sensor networks could be used for environmental monitoring or surveillance.

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Like the Chrysler Hemi, these new antennas may supercharge mobile phones. The small size could allow multiple antennas to be built into mobile devices allowing MIMO connections. The small size should also cut down on the power requirements, decreasing the size of the battery required and increasing the time between charges.

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Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.

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