September 2015

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Raising the Bars in Buildings

With cell phone penetration around 90-100% and studies showing people spend 80-90% of their time indoors, cell phone coverage in buildings is critical.
Jim Sinopoli
Jim Sinopoli PE,
Managing Principal,
Smart Buildings LLC

Contributing Editor

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The one IT device that almost everyone in the world has is a cell phone. Cell phones are an important part of the way we live, work, entertain, communicate and interact. There are almost as many cell-phone subscriptions (6.8 billion) as there are people on earth (seven billion). No other IT or communication device even gets close to the cell phone numbers. In 2013 there were 96 cell-phone service subscriptions for every 100 people in the world (information from the United Nations’ telecommunications agency). A subscription doesn’t mean that everyone has a cell phone; penetration rates in wealthy countries exceed 100% because some people have multiple phones and cell subscriptions. But even in developing and poor countries and economies, the penetration rate of cell phones is around 90%. Africa has very few fixed-line telephones with a rate of 1.4 subscriptions per 100 people, but has 63.5 cell subscriptions per 100 people.

Smartphone Subscriber Growth

Several studies have profiled the use, behavior and “bond” of a smartphone and its user. A study of 2,000 smartphone users indicates that the average cell phone user reaches for their phone at 7:31am in the morning, and checks personal emails and Facebook before they get out of bed. Incredibly, 40% of cell phone users admit to feeling lost without their device. Two other studies indicate that the average smartphone user checks their phone between 110 to 150 times per day.

Mobile Users Reach

With cell phone penetration around 90-100% and studies showing people spend 80-90% of their time indoors, cell phone coverage in buildings is critical. 80% of voice calls and 90% of data usage is indoors. Some buildings have poor cell phone quality, the result being dropped calls and spotty coverage. Very large facilities, tall buildings, facilities with a high density of occupants, and buildings with a steel roof or steel/aluminum siding or buildings with brick, concrete and steel joists may effect cell signals. Low-E glass windows, which typically are used to reduce energy consumption by minimizing the amount of ultraviolet and infrared light that can pass through glass also reflect radio waves and cell signals, creating reception issues with in-building wireless coverage.

Other wireless situations may be related to a lack of capacity of cell coverage where demand cannot be met; these facilities may be large public venues such as stadiums, convention centers, corporate offices, multi-tenant high-rise buildings, university campuses, hospitals, manufacturing facilities, upscale hotels and high-rise condos, casinos, and federal and local government facilities, and even rail and subway systems.

The major issues with cell coverage in buildings are essentially either weak signals from the closest cell tower or lack of capacity. The remedies are different for different problems. The issue with weak signals is typically addressed by strengthening the existing signal from the nearest cell site or tower, referred to as a “repeater-based” solution. It entails an outdoor antenna on the building pointed toward the nearest cell tower site. The antenna receives the signal from a cell tower and sends it through a cable to a bi-directional amplifier (BDA) that strengthens or boosts the signal and relays and amplifies the RF signal traffic between the remote base station and the mobile radios.
The issue with increasing cell capacity is typically addressed by installing smaller antennas in the building. These are active systems referred to as a distributed antenna systems (DAS). Distributed antenna systems are a network of amplifiers and antennas throughout a facility that are connected with copper or fiber cable. It provides voice and data wireless service within a geographic area or structure.

Distributed Antenna SystemsThe headend of the DAS may allow for multiple wireless providers to connect radios at various radio frequencies. This is a “neutral host DAS” where multiple wireless providers use the network at the same time. The DAS essentially feeds smaller cell antennas that cover the buildings’ zones or floors.  A distributed antenna system may be deployed indoors or outdoors. For outdoor DAS, some state Public Utility Commissions have rules requiring the utility to allow Distributed Antenna Systems in the utility right of way.

DAS Business Model

Initially wireless carriers deployed Distributed Antenna Systems (DAS) to expand their service into buildings. The carrier funded, installed and maintained the DAS, anticipating increases in data and voice usage, and eventually revenues. Many carriers realized that their investment in the DAS could be leveraged by leasing to other carriers, thus creating a “neutral host” DAS.

The deployment of a DAS can benefit both the building owner and the wireless carriers. With the building having a DAS, the tenants and occupants of the building have better cell coverage, and complaints and service calls are reduced. The DAS also improves the marketability of the property for the building owner by increasing connectivity and improves the safety of the building’s occupants by enhancing emergency services.

One projection is that DAS installations could grow by 300% by 2017 (iGR Research). Driving the growth is the user demand for ubiquitous reliable connectivity, growing bandwidth requirements and high expectations of quality of service. The cost for typical DAS systems now range from $5 to $10 million. Worldwide distributed antenna system (DAS) revenue reached $2 billion in 2013. The major DAS leaders are Commscope, Corning Mobile, and TE Connectivity. (Infonetics).

The DAS business models vary. One approach is the building owner simply owns the DAS and takes on the responsibility for service, maintenance and upgrades. Another option is a third party, that could provide a neutral-host multi-carrier network; the provider would own, operate, manage and monitor the network, and the building owner would not have to invest in the DAS. Finally, another possibility is for the building owner and the third party splitting the initial capital costs of the DAS, with the third party owning the network and responsible for all maintenance can service and carrier relationships.

Generally wireless carriers are less likely to finance the installation of a DAS in office buildings and malls, and look instead at larger venues such as airports and stadiums and  corporate campuses, as they seek to concentrate their efforts only on the most high-profile, most profitable opportunities. The costs to install and operate the DAS networks are significant and typically cannot be justified by the wireless carriers from a return on investment perspective. The carriers may install and operate a DAS in stadiums and airports, but cannot justified smaller buildings.

DAS VariantFinally another DAS variant is the large building which has an “anchor tenant” which is also the building owner. The anchor tenant occupies most of the building but leases out available or unused space. The wireless carrier for the anchor tenant would probably bring in single carrier but could benefit from the additional revenue for the leasers. Under the terms of most commercial real estate leases the building owner can pass through the cost of operating and maintaining the building to the tenants in the form of additional rent, common area maintenance (CAM) or utilities cost, including, but not limited to communication systems and other equipment used in common by the tenants. If the DAS infrastructure is paid for by the DAS provider, and the wireless communication service is sold back to the building as a “utility”, a commercial lease may cover this charge as a tenant utility expense. In these cases the DAS provider would be a licensed wireless carrier with the transaction structured as a “utility easement in gross”, with a “utility service agreement” provided by the carrier for a fixed term. In this scenario the DAS provider gets its return on investment and the building owner property owner collects fees for utility charges since the tenants are the beneficiaries of the improved wireless service.

The business considerations for these models involves: (a) who owns the network, (b) who provides the capital, (c) agreements with each carrier, and (d) the service level agreements (SLA) for the DAS including their scope, quality, responsibilities and a contracted delivery time (of the service or performance). Part of the ongoing service and maintenance may change to the building over time due to renovations and space modifications; such alternations could affect the performance of the building antennas. Also the latest technology changes such as the recent shift from 3G to 4G, will impact updates and changes to the DAS deployment.

Life Safety and Emergencies

A building with a DAS can increase the safety of the building’s occupants. During an emergency the DAS will enable 911 calls within the building. The multiple antennas in a DAS will provide improved communication reliability, and provide communications with first responders, police and fire fighters. Note that two national fire codes, the National Fire Protection Association’s NFPA-1 and the International Fire Code were enacted in 2009 that require “in-building amplification systems” such as a DAS. Such codes have been adopted in municipalities across the country.

The Federal Communications Commission (FCC) is responsible to ensure that 911 services and other critical communications remain operational during emergencies. One of the main components is 911 call processing and delivery through Public Safety Answering Points (PSAP). Typically a dispatcher can verify the caller’s location. However the use of cell phones makes determining a wireless 911 caller’s location more complicated than determining a traditional wireline 911 caller’s location. For callers placing wireless 911 calls, the FCC has required wireless service providers to make location information automatically available to the PSAPs. Basic 911 rules require wireless service providers to transmit all 911 calls to a PSAP, regardless of whether the caller subscribes to the provider’s service or not. The wireless service providers have to provide the PSAP with the telephone number of the originator of a wireless 911 call and the location of the cell site or base station transmitting the call. Eventually wireless service providers will be required to provide more precise location information.

[an error occurred while processing this directive] The advanced DAS systems can deploy a Self-Organizing Network (SON).  The SON capabilities are sophisticated. The network can automatically configure and integrate new equipment into the wireless network; something similar to plug and play; the DAS network discovers new components in a system without the need for a technician to manually configure the equipment. The SON can also automatically optimize the wireless network. It optimizes based on data from the system itself. An example of self-optimization is the automatic switch-off of a percent of base stations during the night hours which would reconfigure to cover a larger area or a significant increase in usage. Finally the network can self-heal; the network can identify faults or failures in the network such as failing base stations, and automatically compensates and re-configures the wireless network to minimize the impact.

The DAS networks can now move cell capacity from one location to another, and identify what radio spectrums and what uses are needed on-demand in real-time. The DAS can provide on-demand capacity wherever and whenever it is needed.

Smaller Cells

While distributed antennas systems are primarily focused on large venues and buildings, there are smaller cells available for more modest spaces and buildings. These cells are called micro cells, pico cells, femto cells, etc. They are small mobile phone base stations that are connected to the wireless carrier’s network via the Internet, and typically used in areas where the mobile signal is weak. Generally these are very low-range, low-power base stations, able to be deployed in a home, home office, enterprise businesses, and indoor and outdoor public spaces. Generally the equipment is provided by a wireless carrier mobile network operator, and operates in licensed frequency bands. A base station in a wireless carrier’s network may might have a radius of 20-30 km coverage; the small cells may have coverage radius in the range of 10 meters up to 2 kilometers in rural areas.


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