Is 5G a Better Choice for Indoor Mobile Data?Is 5G a Better Choice for Indoor Mobile Data?

For the vast majority of IT shops, a functional, centrally controlled wireless LAN (WLAN) is one of the most valuable infrastructure elements provided. Using the ubiquitous Wi-Fi standards, WLANs have become the most common portal for wireless-equipped laptops and smartphones to connect to the Internet and other computer resources. Some have even tapped their WLANs to support wireless PBX stations using equipment from companies like Vocera and SpectraLink.

However, the combination of 5G and small cells has provided the mobile operators with what they feel is a viable option for connecting both voice and data mobile devices in indoor enterprise environments. The 5G New Radio (NR) standard has greatly expanded the range of frequencies that can be used to transport 5G signals, so the carriers now boast the RF capacity to emulate the performance users experience on a well-designed WLAN. Using small cells configured like Wi-Fi access points, the carriers say they can seamlessly extend their wide-area wireless voice and data coverage into the office.

As those indoor wireless voice and data offerings begin to take shape, enterprise IT buyers will need to decide they’re as viable as carriers say they are.

Wi-Fi & Cellular: A Difficult Marriage

I’ve always been intrigued by the cellular industry’s open disdain for Wi-Fi. Cell carriers have longed seemed to have a vendetta against the cheeky upstarts that had the audacity to provide an alternative wireless technology that didn’t involve a two-year contract and a monthly bill. In support of their case, the cellular folk gleefully recount tales of congested Wi-Fi networks, RF saturation on unlicensed frequency bands, and all manner of risk from mysterious “security concerns” they can never specifically identify -- probably because the Wi-Fi industry put those concerns to bed 15 years ago.

Those of us who were in the “wireless” field (as opposed to “Wi-Fi” or “cellular” fields) clearly see the irony of the cellular guys trashing Wi-Fi when we all know that Wi-Fi has actually saved the carriers’ bacon. Apple initially gave AT&T exclusive rights to distribute the iPhone, the first truly revolutionary wireless product since the inception of cellular. AT&T’s reward was the opportunity to watch its network collapse in spectacular fashion… and Wi-Fi turned out to be its salvation.

When the first iPhones hit the streets in 2007, the carriers were selling 2G services, which means users were getting data rates measured in tens of kilobits per second. The only way users could get their iPhones to deliver decent performance was to connect to Wi-Fi!

To add insult to injury, AT&T’s response to its overstretched cellular data network was to resort to Wi-Fi offloading in dense usage areas. As the macro cellular network clearly couldn’t carry the load, AT&T deployed accessible Wi-Fi hot spots in areas with dense usage. Since the iPhone’s first choice for data service was Wi-Fi, this was a pretty simple solution to deploy. Once the iPhone saw an available Wi-Fi option, it automatically jumped off the AT&T cellular network.

Virtually all smartphones still default to Wi-Fi, so your smartphone will jump onto a Wi-Fi network, including that expensive Wi-Fi infrastructure the IT guys have deployed throughout your facility, any time it can get access.

5G: Answer to All Prayers (Particularly the Carriers’)

Despite their long-term dependence on Wi-Fi, 5G’s emergence seems to have given carriers the idea that they will now have the capability to handle all of our data traffic, indoors and out, over their vastly improved wireless networks. The key development is 5G NR, with its expanded frequency options.

Cellular networks have traditionally operated on a few frequency bands generally topping out at around 2 GHz. The original band (Advanced Mobile Phone Service, or AMPS) was in the 800-MHz range. In the 1990s, the FCC opened the 1.9-GHz Personal Communications Service, or PCS, band, which increased the number of channels, reduced the cost per minute, and changed cellular from an enterprise to a consumer service. In this century, the FCC has auctioned off a number of frequency slots in the 600-MHz and 700-MHz bands that offer even greater coverage areas and better building penetration.

What all of those bands have in common is the ability to support transmission ranges suitable to cover wide areas (e.g., several miles). The obvious advantage is they allow carriers to cover large areas with fewer cell sites.

5G NR covers all those legacy bands (including those used in other countries), as well as defines operation at much higher frequencies. These higher frequencies are often referred to as millimeter bands (a reference to the signal’s wavelength at those frequencies).

In 2017, Verizon acquired Straight Path Communications, gaining extensive nationwide holdings in the 39-GHz band and 28-GHz holdings in major markets. For its part, AT&T is testing millimeter wave systems in its early 5G trials, apparently using spectrum it acquired in its 2018 purchase of FiberTower.

5G allows the integration of other frequency bands into the network, too. These include the 2.5-GHz bands Sprint acquired with its Nextel purchase (now designated Band 41), the licensed 3.5-GHz CBRS bands, and the 5-GHz Unlicensed-NII bands the FCC opened to mobile operators in 2017.

The availability of those along with the millimeter bands greatly increases the carriers’ potential network capacity. However, the integration of these additional bands does change the network configuration substantially.

Click below to continue to Page 2: Enter the Small Cell, and more

Enter the Small Cell

There are two important things to know about millimeter wave spectrum. First, transmissions on these bands won’t interfere with the lower-frequency (sub-6 GHz) bands carriers have traditionally used. That means the traditional channels and millimeter wave channels can operate simultaneously in the same areas. The other is that the transmission range on millimeter waves is relatively short. Millimeter wave testing is ongoing, but the expected range maxes out at 100 to 200 meters -- basically, the transmission range of Wi-Fi.

The short range and non-interference characteristics mean that in an outdoor network, a macro site might cover a large area with long-reach channels in the 600- to 800-MHz band. For dense usage areas, however, a carrier could light up non-interfering small cells operating on those higher-frequency millimeter bands underneath that wide-area 5G (or even 4G) coverage umbrella. Just like Wi-Fi offloading, mobile devices would seamlessly roam off the macro channels onto a millimeter wave channel when they moved into one of those small cell coverage areas.

Importantly, as those small cells utilize 5G cellular standards, devices could use the same cell identification and handoff techniques they use to move between macro cells. We have seen problems with devices roaming between Wi-Fi and cellular networks, particularly when the Wi-Fi network isn’t operating up to par.

What Does This Have to Do With My Wi-Fi Network?

As it turns out, carriers have identified two important roles for small cells in the new cellular architecture. Besides providing a way to densify coverage in high-use areas, small cells can replace traditional distributed antenna systems (DAS).

Indoor cellular coverage is inherently problematic, with the network being outdoors and the users indoors. Building penetration is always a factor in radio coverage, and the advent of energy efficient LEED-certified building techniques have turned office buildings into virtual Faraday cages.

When pressed to improve indoor coverage, carriers had typically deployed in-building DAS, which captured the signal from the nearest cell tower (or from a dedicated cellular base station installed in the building) and used a system of cables, amplifiers, and antenna heads to distribute it throughout the facility. In what’s known as a neutral host configuration, one operator (or a third party like Crown Castle) would install the DAS and then charge other carriers for its use in distributing their signals.

Problems arose when the cellular standards outgrew the original DAS design. The big culprit was the use of multiple-input and multiple-output (MIMO) transmissions in cellular. With MIMO, the idea is to create multiple non-interfering channels in the same frequency band to effectively multiply the transmission rate. A two-channel MIMO will double the raw transmission rate while a three-channel system will triple it, and so forth. As you can imagine, MIMO was a main contributor to the improvement in transmission rates we saw with the move from 3G to 4G LTE.

The gotcha is that for MIMO to work, the two channels, or streams, must be sent from different antennas, and those antennas must be placed some distance apart (nominal spacing one-half wavelength). The problem was that DAS could only distribute one channel or stream. As the networks moved to MIMO transmission, DAS would still work, but indoor users could only get one stream. That effectively gave indoor users a fraction of the capacity outdoor users would get; user devices automatically adjusted to the capabilities of the cell tower or the DAS through which they connected.

It should be noted that the industry has come up with a variety of home solutions (e.g., femtocells) and for business locations of up to about 50,000 square feet. Most of these solutions use your Internet access to connect back to the carrier’s network, though some use an outdoor antenna to connect to the nearest cell site. And Sprint offers Magic Box, which uses a separate radio link to connect back.

For large enterprise installations, the options for improving indoor coverage are far more limited. Given that installing two or three DAS systems to distribute two- or three-stream MIMO transmissions was entirely impractical, the industry came up with a solution using small cells that inherently support MIMO. Companies like SpiderCloud and Airvana/CommScope now make small cells of this type, and the deployments look very much like enterprise Wi-Fi networks.

In an indoor small cell deployment, a central controller would connect over in-house wired LAN connections to smart antennas located throughout the facility. Again, testing at millimeter wave frequencies is ongoing, but the expectation is that we should have roughly as many small cell antennas as we have Wi-Fi access points (APs).

For enterprise infrastructure groups, the big question is: Will the carrier connect all of this equipment over the customer’s existing wired infrastructure (an unlikely prospect given the carriers’ control complex), or will it want to install its own cabling and LAN switches in parallel with the customer’s? I hope you’ve got some room in your closets.

One last nightmare is that we might need a separate indoor small cell solution for each carrier supported. There are discussions of neutral host deployments, similar to those used with DAS, for supporting multiple carriers on a shared small cell infrastructure. Those plans, however, are in the very early stages.

Click below to continue to Page 3: So, What Are My Choices?

So, What Are My Choices?

If approached with the idea of scrapping their WLANs and buying cellular data plans for all of their mobile devices (including data cards for all the laptops), most of my clients would tell the carriers to take a walk. However, there are some mitigating circumstances.

While Wi-Fi has proved it can take care of our mobile data users, we still need cellular voice coverage. We can set up a smartphone to use VoLTE over Wi-Fi, but the device’s default choice for voice is cellular. The option for voice calls is selectable in some Android models, but iPhones still dominate in the enterprise. We still need cellular voice capability, and we’ll likely need something from the cellular carriers to boost the signal for cellular voice, regardless of what we’re doing with the data traffic. All the indoor small cell solutions being described for large-scale deployment look at carrying all voice and data. Delusions of grandeur, I suspect.

For the data requirement, I do have some clients suffering from Wi-Fi fatigue and they might be interested in a cellular data option. The primary cause of that fatigue is the never-ending Wi-Fi upgrade cycle. I have clients that go absolutely apoplectic when I inform them there’s yet another Wi-Fi upgrade on the way, as they know what kind of budget they’ll have to come up with for replacement APs.

The tough part is that as newer versions of Wi-Fi become available (e.g. 802.11ax), we can’t string users along with mediocre Wi-Fi -- they’ll have the upgraded versions on their home networks (an unchallenging $100 investment) and their latest smartphones will always have the newest Wi-Fi capability. In this new consumer-driven world, users hold IT to the standard of delivering a service that matches the performance they have at home -- despite the fact it might cost many millions to pull that off.

Conclusion

With a traditional DAS to support cellular voice users and a Wi-Fi network for mobile data traffic, IT departments were pretty much free to ignore wireless, but that may have to change. Of course, I still have clients that entrust cellular decisions to the Purchasing Department; I wonder how they’re going to fare in this new environment.

Some businesses faced with Wi-Fi’s “can’t live with it, can’t live without it” scenario are starting to pursue the approach hotels and small businesses have used for years… i.e., they’re outsourcing their Wi-Fi infrastructure. Cellular operators like AT&T and Sprint offer managed Wi-Fi services, providing yet another option to outsource your Wi-Fi infrastructure.

For now, most businesses have accepted the status quo of privately owned and operated Wi-Fi as an ongoing annoyance, and continue to pay the piper. We still hear the occasional dream of an all-wireless environment, but that wished for panacea continues to stay at least one generation ahead of wherever we are in the technology development.

Many enterprise users are simply looking for a cellular solution that effectively addresses voice requirements while they continue to maintain and upgrade Wi-Fi infrastructure. However, what we really need from the carriers are more choices, and those choices will have to be presented clearly and intelligently.

For enterprise buyers, the clear message is that the wireless landscape is undergoing a monumental shift with the introduction of 5G, and IT departments are going to have to sharpen their understanding of what’s going on in cellular as they plot how they’ll continue to offer the mobile services their users demand. Knowledge is power.

To learn about more of the subtleties involved in this transition, join me at Enterprise Connect 2019, taking place the week of March 18 in Orlando, Fla., where I’ll be leading the session, “What You’ll Wish You Knew About 5G,” on Thursday, March 21, at 9:00 a.m.

Register for Enterprise Connect 2019 today using the code NJPOSTS and save $200 off our current conference rate!