By Tracy Ford
From the February 2017 Issue
Smartphones and tablets are changing the way society communicates with each other and accesses content. Forrester Research labels this as “the mobile mind shift—the expectation that a person can get what they want in their immediate context and moments of need.” Simply put, people turn to their mobile devices for answers to their questions. A strong wireless infrastructure foundation is needed to accommodate these mobile moments. Wireless connectivity is needed to address public safety concerns as well. Today, 70% of 911 calls take place over the cellular network, and 64% of calls made to 911 are indoors.
Mobile broadband connectivity is not often thought about during initial architectural drawings, or early on in the process for designing new buildings. In fact, some building envelope elements (like low-emission glass) and building material choices (like aluminum) hinder radio frequency (RF) transmission, necessitating the need for in-building connectivity to be brought into the facility.
Established buildings also may suffer from poor in-building connectivity even if the facility previously had sufficient coverage. The surrounding physical landscape may have changed; trees grow taller and other structures may be built, which can impede the cellular signal. If the cellular signal is weak inside a building, facility management may want to add an in-building solution such as a Distributed Antenna System (DAS), building amplifier, or other small-cellular solution to boost coverage and capacity. Wireless carriers own the RF spectrum required to bring cellular connectivity inside a building so facility managers must work with carriers and their partners (often called third-party neutral host providers or systems integrators) to achieve coverage.
Much of the cost of deploying in-building cellular coverage can be defrayed by including plans for cellular connectivity early in the design stage for new buildings and during planned renovations to an existing one. It is easier to run fiber, antennas, and other equipment while ceilings, floors, and walls are exposed.
Once the solution has been chosen, there are physical considerations to examine before deployment. These include: fiber availability throughout the building; cabling pathways; physical space to house equipment; building aesthetics; ensuring equipment being deployed has been approved by carriers; power requirements; determining who will maintain the system; building size; and traffic (density of population and traffic patterns).
The installation of these systems within buildings can present challenges. While each venue is unique, there are generally common design, approval, and construction issues. While small-cell installations may take up less space than a DAS, the general principles apply to any in-building installation. The following list of considerations should be part of the initial design process and followed during construction.
Depending on building(s)/venue size and number of wireless carriers connecting to the DAS, having a common equipment space for the head-end equipment is critical, and often difficult to find. Locating equipment in existing IT rooms and closets can be an option. However, the building IT department will need to review and understand future space and resource requirements for both the building IT and DAS equipment. Often these spaces end up on mechanical, basement, or parking levels, which can pose a number of environmental issues. The design in these areas should be reviewed carefully to mitigate issues like moisture and dust.
HVAC is critical for DAS equipment spaces. Existing cooling capacity should be assessed for the initial system and anticipated growth. Dedicated IT cooling is required, so standard building cooling or small residential type applications should be reviewed carefully for this application. HVAC systems that are designed specifically for IT applications and that are scalable are strongly recommended. Ductwork and raised floor applications required for proper air circulation should be coordinated with cabling design to minimize pathway conflicts.
Power for the DAS head-end is an important consideration. Capacity of the existing power distribution system should be analyzed. Neutral-host DAS power designs should consider additional requirements of future carriers. If the building is supplying the power, the metering and interconnection for smart building monitoring will need to be coordinated with facility management. Utility metering will require coordination with the local power provider and can be a long lead item. Utilizing building backup power or installing a backup generator to harden the system are also design considerations.
Fire protection for the head-end and maintenance of existing fire wall assemblies is another important design consideration. For spaces with existing sprinkler systems, new walls or rooms within the space may require modifications for additional sprinkler heads. For critical system infrastructure or larger DAS systems, a pre-action sprinkler system may be considered to reduce the chance of accidental discharge. Clean agent gas systems like the FM-200 fire suppressant agent also can be used to minimize damage to electrical equipment should fire suppression be required. Early warning notification air sampling systems can minimize notification and response time to smoke or fire.
Firestopping of cabling and utility penetrations is also important. All wall/floor penetrations should be sealed to maintain existing wall rating. Where future cabling is anticipated, penetration products are available that are resealable and speed up future installations. It should be noted that cabling should never be routed through egress hallways or stairwells unless it is related to the function of that egress as allowed by the building code. Cabling that passes through plenum spaces is required to be plenum rated to meet low-smoke, low-flame spread requirements.
Design requirements for accessory equipment cabinets should not be overlooked. Depending on the system manufacturer and system configuration, remote cabinets that are required for conversion from fiber to coaxial cabling will need to be located throughout the building. Locations for these remotes are often in IT or mechanical rooms, where space may be limited, so initial walks of potential remote locations should be done during the design phase. Considerations for power and backup batteries should be reviewed and included as part of the design.
Once a design is completed, critical points of discussion include work hours, restricted access points, occupant space restrictions, union requirements, and preferred specialty vendors. Coring and firestopping of vertical and horizontal pathways for RF cabling and power are critical. Scanning of floor and wall penetrations often will be required, and review of pathways is key to identifying areas that require cutting and patching because they do not have accessible ceilings.
In-building mobile communications is becoming a utility in that building occupants expect to have it when they turn on their devices. Delivering that connectivity can be done more cost-effectively if the project is planned at the beginning of a new construction or renovation project.
Ford is director of the HetNet Forum at the Wireless Infrastructure Association. The HetNet Forum is a membership group of WIA dedicated to the advancement of the heterogeneous network. Ford has spent more than two decades covering the rapidly changing wireless industry.
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