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August 24

Choosing the Right In-building Cellular Connectivity Solution

The workplace is now mobile, with employees who are more and more relying on smartphones and tablets to get work done. A recent survey of 2,000 workers by Zinwave found that such mobile devices are the second most widely used—and second fastest growing—communication tools in the workplace, behind only email. This isn’t only for making voice calls, workers are using these devices to access the internet and productivity applications, send text messages and make video calls. More than 62 percent of respondents use their cell phones every day for both internal and external communications, and 72.3 percent use it at least weekly.

This illustrates the need for reliable in-building cellular connectivity. Use of these mobile devices will only increase in the coming years, particularly as Millennials—who have grown up in a world of constant connectivity and already spend much of their lives online—and the generation behind them, Generation Z, become larger parts of the overall workforce.

Businesses and building owners need to ensure reliable, uninterrupted cellular coverage—not only to improve productivity, but also to retain talented employees and happy tenants. There are numerous tools they can use to improve connectivity. All come with advantages, but there also drawbacks.

To help you determine the connectivity solution that’s right for you, here are some of the most commonly used solutions and the pros and cons of each.

Repeaters and Bi-directional Amplifiers

Repeaters have been around a long time, and they’re essentially an electronic device that does what the name implies: They’re bi-directional amplifiers (BDAs) that receive signals from one source and transmit them somewhere else. They draw signals from neighboring cell towers to boost the wireless reception inside the building. They’re low-cost; you can buy them yourself, and they’re easy to deploy.

However, most repeaters are consumer-grade products. They’re low-power in terms of output, meaning they only cover a small area, and they are not multi-frequency.  And because they are reradiating signals from an adjacent cell tower, they are not providing additional capacity, just “borrowing” capacity from the macro network.

Repeaters with a little more oomph are considered industrial-grade, but those come with their own challenges. In particular, to install them and turn them up you need to file paperwork with the wireless operator (who has the rights to the spectrum) and get their permission (a process which can be quite lengthy). The permission is needed because you’re grabbing the strongest signals from their nearby cell tower and your users will be contending for the same capacity as users on the outdoor network, creating additional strain on the operator’s already heavily burdened network. That added capacity demand can create more noise in the network, so many carriers don’t approve the use of industrial-grade repeaters. For example, AT&T has had a ban on industrial grade repeaters in place for about eight years in the San Francisco Bay area.

In the slim chance the carrier does give permission, there are other challenges. The repeater is basically a box with a few strands of coaxial cable running out to antennas, creating what amounts to a passive distributed antenna system (DAS). And, as mentioned previously, because you’re taking signals from a neighboring cell tower, there isn’t capacity in the network set aside for your solution. That means you’ll be competing for capacity with all the others hitting that cell tower, from people driving by or others in the general coverage area of the tower. There’s no guarantee of bandwidth availability, throughput or performance.

Voice over WiFi

This involves customers using a standard WiFi network for talking over their phones. This can be useful in limited environments—where the company isn’t moving a lot of data, if there’s no carrier signal from the outside, or if there are only a handful of people in the office. It’s not a business-class solution. It will drop calls and won’t hand off calls to an outdoor network if someone were to step outside of the office, and there can be interference on the network. For example, the network doesn’t know if your phone call or the PowerPoint your colleague is downloading is more important, so it will stop transmitting one and let the other one through resulting in dropped calls. There’s no quality-of-service assurance, and if the WiFi has security features like SSID, someone who’s not an employee but has business in the office may not be able to get on the network.

Small Cells

Small cells are essentially low-powered radio access nodes that can be placed throughout a building for improved wireless connectivity and can run in licensed and unlicensed spectrum. They’re made by telco vendors like Ericsson, Cisco and Alcatel-Lucent, can be used outdoors or indoors (depending on how powerful the unit is) and come with a wide range of coverage areas. They connect directly back to the operator’s core switching network, putting out a single frequency and single LTE channel. They represent a cost-effective option for a good, clean signal and for providing capacity in the network, assuming that you only need coverage and capacity for a single wireless operator. Small cells can be brought together to deliver the coverage you need to run the apps you want and support dozens of simultaneous users, without capacity being an issue.

But they’re not as inexpensive as some believe. Individually they’re relatively cheap—roughly a couple thousand dollars each—but they come with provisioning costs, such as basic cabling and installation, the power to run them, the backhaul to connect to the network (which can be expensive and take some time to provision) and getting the necessary GPS signal, which can at times be challenging to get inside a building. Cell overlap is another issue and a delicate balancing act. Each small cell is running at its own frequency and has its own coverage area. The system needs to be set up in a way that there are enough overlapping coverage areas between them so calls aren’t dropped as the person moves from one coverage area to another. But too much overlap can create interference between the small cells.  And, even if the overlap is sufficient for voice calls, a weak signal at the cell edge can mean poor data performance.

Small cells also might not be the best technology to use in large facilities. Each small cell covers 6,000 to 10,000 square feet, so in a big building you may need a lot of small cells, meaning more backhaul and GPS signals, which can be difficult and expensive. Suddenly, your inexpensive solution just got very expensive very quickly.

The complexity only increases if you use more than one operator—with more carriers you need more small cells, and there are more holes punched in the ceiling for installation, which can roll up the costs. Efforts to make the system easier by creating self-optimizing networks (SON) where disparate small cells can recognize each other haven’t gotten far.

Distributed Antenna Systems

Another option is a distributed system, a solution that comprises pairs of amplifiers and antennas that are distributed throughout a building. They are linked through cables to a central distribution hub, which connects to the radio-frequency source used by the mobile provider. Through a DAS, the carrier’s wireless signal is distributed to all parts of the building.

A DAS solution answers a lot of the problems that come with the other options. Because the signal used to support a DAS is separate from external towers, you don’t get the concerns about capacity you have with repeaters and bi-directional amplifiers. And since it’s actually a cellular signal that’s being brought into the building, you will have a guaranteed level of service and don’t have the potential network interference you can get on a voice-over-WiFi system. Plus, calls can seamlessly hand-off from the inside network to the outside network if you need to leave the office.

Small cells are probably the closest in coming to matching a DAS for delivering the type of reliable cellular signal needed, but are still an inferior solution to a DAS. In this case, it all comes down to price. While a single small cell may be inexpensive, there are costs, as discussed previously, for the equipment and cabling needed to actually make the small cell functional. Also, individual small cells only cover limited areas. So for a large facility or multi-floor building, it may actually take dozens of small cells (depending on the size of the building) to provide the coverage needed to get a signal to every square foot causing the cost to increase exponentially. 

The other drawback to small cells is that they only cover a single frequency, or, in other words, the signal of one carrier. If you wanted to add an additional carrier, you’ve just doubled your investment.

With the right DAS—one that covers all the most common cellular and public safety frequencies at installation—there is no additional cost needed to add new carriers. There is no additional cost to add public safety support. And when new technologies are developed that take advantage of radio frequencies—like location-based services and IoT—there’s no cost to take advantage of those either. The infrastructure is already in place.

Cost is the biggest knock against DAS. It’s what small cell providers will try to use to dissuade someone from going with a DAS solution. And it is true that a DAS can be one of the more expensive options, if the application is such that it is a small building requiring support for only one wireless operator. But for mid-sized and larger facilities that need support for multiple wireless frequencies and operators, DAS is the most economical solution.  However, that is not to say that large venues needing multi-operator support on day one don’t require a significant investment.  But even that is something that DAS providers are addressing. With a Cellular as a Service™ pricing model, a DAS can become a more budget-friendly, monthly operational expense rather than a capital one. Businesses no longer have to invest in the hardware needed to provide improved indoor cellular coverage. They just get to enjoy the benefits.

The demand for strong indoor wireless connectivity is high now and will only increase in the coming years. Organizations have a broad array of options for improving the reception in their buildings, but they need to do their research to ensure what they decide on will not only meet their needs now but also in the future.

Learn more by reading our our ebook on comparing in-building wireless solutions.



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