Wi-Fi’s Future is in the Air

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In many ways, Wi-Fi is a victim of its own success. What started out as a way to use what some engineers called the “garbage band of 2.4 GHz” to connect varied equipment has evolved into a standards-based system used by billions of devices. In fact, some 12 billion Wi-Fi products have already been shipped, with another 3 billion to be shipped in 2016, according to the Wi-Fi Alliance. Wi-Fi will continue to be one of the most prolific technologies around the world, with 38 billion products touching nearly all aspects of our lives by 2020.

As device makers and consumers see Wi-Fi as a key technology in everyday life, the wireless spectrum is becoming more congested and impacting performance. This is especially true in dense urban areas, where dozens of access points can overlap. Another factor is the growth of high-bandwidth applications, such as video streaming and multi-user gaming. To keep up with demand, Wi-Fi and the equipment used to test Wi-Fi devices must continue to evolve.

Wi-Fi Evolution

Modern Wi-Fi took root when the IEEE formed the 802.11 working group back in 1990 to promote the standard. The initial release, 802.11 Wireless LAN, was approved in 1997. Since then, several advances to the Wi-Fi standard have occurred. Perhaps the most significant was 802.11n, released in 2009 and considered a fourth-generation wireless LAN technology standard. It operates in both the 2.4 GHz and 5.0 GHz bands. Users had already begun migrating to 802.11n, based on the Wi-Fi Alliance's certification of products conforming to a 2007 draft of the 802.11n proposal. This version of the standard improved Wi-Fi in two major ways:

First, it opened up the 5 GHz band. Although support for 5 GHz is optional under 802.11n, many users found this feature desirable because it relieved the congestion users were experiencing on the 2.4 GHz band.
Second, it offered better throughput, as the maximum net data rate was increased from 54 Mbit/s to 600 Mbit/s. One of the ways it did this was by increasing the channel width from 20 MHz to 40 MHz. Another way it improved performance was to incorporate multiple-input-multiple-output (MIMO) technology. MIMO is made possible by devices utilizing multiple antennas. The antennas enable data to be transmitted over multiple streams, which provides much higher and faster overall data throughput.

Through the years, the evolution of 802.11 continued; the 802.11ac standard was published in December 2013. Compared to 802.11n, it features wider channels (80 or 160 MHz versus 40 MHz) in the 5 GHz band, more spatial streams (up to eight versus four), higher-order modulation (up to 256-QAM versus 64-QAM), and the addition of multi-user MIMO (MU-MIMO).

“Wave 1” implementations support 80 MHz channels, three spatial streams, and 256-QAM, yielding a data rate of up to 433.3 Mbit/s per spatial stream (1,300 Mbit/s total) in 80 MHz channels in the 5 GHz band.
"Wave 2" devices include support for 160 MHz channels, four spatial streams and MU-MIMO. Device makers began shipping Wave 1 devices in late 2013 and are starting to ship Wave 2 devices this year.

Today, 802.11ax is touted as the next generation Wi-Fi standard. 802.11ax promises to deliver even higher throughput than 802.11ac by using a more efficient modulation scheme called orthogonal frequency division multiple access (OFDMA). OFDMA is a huge benefit of the 802.11ax standard. The primary goal is to increase the data rate per user by a factor of 4x and enables 10x more capacity over 802.11ac.

The current official release date of the 802.11ax standard is sometime in 2019. As with the rollout of 802.11n, though, we should begin to see devices that support the draft standard before then. It is absolutely essential for 802.11ax to keep progressing, as another technology is beginning to compete for bandwidth.

On Your Mark

Wi-Fi is in a horse race with two LTE technologies: LTE in Unlicensed Bands (LTE-U) and LTE Licensed-Assisted Access (LTE-LAA). LTE-U is quietly emerging in the 4G/LTE wireless networks specific to North America that use unlicensed spectrum—the same unlicensed 5 GHz spectrum currently being used by Wi-Fi.

Some studies have shown that LTE technology—originally used in cellular phones in licensed bands—has performance advantages over Wi-Fi when operating in unlicensed bands. These advantages include:

Better link performance
Medium access control
Mobility management
Excellent coverage

These benefits, combined with the vast amount of available spectrum (> 400 MHz) in the 5 GHz band, make LTE-U a promising radio access technology in the unlicensed arena. Mobile operators are hot to implement this technology, as it will enable them to offload data traffic onto unlicensed frequencies and reduce the load on their wireless networks that use licensed spectrum. Devices that use LTE-U are currently being field-tested, and commercial devices will be available to consumers starting this year.

Some of the industry's biggest players are behind LTE-U. In 2014, Verizon, in cooperation with Alcatel-Lucent, Ericsson, Qualcomm Technologies Inc. (a subsidiary of Qualcomm Incorporated), and Samsung, formed the LTE-U Forum. The LTE-U Forum is a consortium, much like the Wi-Fi Alliance. In March 2015, the group published technical specifications, including minimum performance specifications for operating LTE-U base stations and consumer devices on unlicensed frequencies in the 5 GHz band and coexistence specifications.

The coexistence specifications are meant to address concerns that LTE-U devices will interfere with Wi-Fi networks. The FCC requires that devices using unlicensed spectrum do not interfere with the operation of other devices using those frequencies, but that's easier said than done.

The LTE-U Forum has conducted tests and published a report that shows that LTE-U will not cause interference to Wi-Fi. The study concludes that, “With a set of well-designed coexistence algorithms, the level of protection that LTE-U nodes provide to nearby Wi-Fi deployment can be better than what Wi-Fi itself provides.”

Not surprisingly, Wi-Fi companies aren't quite so optimistic. Google has issued a report predicting that LTE-U would seriously interfere with Wi-Fi. Fortunately, we're at a point where these issues can be worked out before the widespread sale and implementation of devices that will cause harmful interference to one another. Consumers will benefit greatly if the Wi-Fi Alliance and the LTE Forum work out these issues.

One possible scenario is that devices support both 802.11ax and LTE-U. This is certainly in the realm of possibility, since the 802.11ax spec describes some of the same mechanisms found in LTE-U. For this to happen, chipset manufacturers will have to make chipsets that support both standards. Another scenario is that the IEEE 802.11ax committee will continue to improve the Wi-Fi specification, so that when it is released, it will be competitive with LTE-U.

Increased Testing Challenges

Of course, new technologies mean new testing challenges. Range and battery life will continue to be a concern. Higher data rates can reduce range and battery life, and manufacturers will have to make sure that their new designs don't fall short in these two areas. Comprehensive testing during the design phase is important to ensure that the customer experience isn't degraded.

Chipset calibration is also an issue. As opposed to cellular, many device manufacturers do not perform Wi-Fi calibration in order to minimize test time and reduce cost. Failing to do so, however, can adversely affect range and battery life.

Another test challenge is that consumer devices are supporting more cellular and connectivity technologies. For example, smartphone manufacturers need to support 2G, 3G, and 4G cellular technologies today to ensure worldwide operation. Manufacturers need test equipment that can cover all of the communications protocols that a device supports.

More standards, in general, means increased test times. More test time has an impact on the test process and leads to a financial quandary. Balancing new test methodologies with managing reasonable test times, at the same time ensuring a high level of quality, deserves a fresh look. Test methodologies or test strategies should be periodically re-evaluated, keeping mindful of the impact on the economies of test.

In addition, advanced technologies will drive the need for more sophisticated test equipment. Because 802.11ax and LTE-U use advanced modulation techniques, tester manufacturers will have to upgrade their equipment. For example, the next generation of Wi-Fi devices will use more advanced modulation techniques, such as 1024 QAM, which will drive the test equipment manufacturers to introduce products to meet stricter performance requirements.

Another example is the addition of MU-MIMO technology to 802.11ax. In addition to multiple radios, the main test challenge is validating the routers’ beamforming performance.

Conclusion

Without a doubt, Wi-Fi technology and the equipment needed to test it will need to adapt over the next few years. On the one hand, consumers are demanding more from their Wi-Fi in terms of more devices, more users and more bandwidth. On the other, competing technologies (such as LTE-U) are looking to grab a share of the market, if not dominate it.

The next two years are crucial. The longer it takes manufacturers to develop and test LTE-U consumer devices, the better for 802.11ax, as it gives the standards committee time to make the standard more competitive. And, chances are that the groups supporting Wi-Fi and LTE-U will make concessions that make co-existence possible.

Adam Smith, Director of Marketing

LitePoint