In the prior installment of this series, we discussed Ethernet networking and horizontal cable plant options to connect installed radios to the Telecommunications Room supporting a single floor of a building. FYI, if you are new to this series and want to get the most out of it, please start here and read the posts in sequence.
This post covers the critical, yet usually overlooked, topic of the Telecommunications Room. The word “overlooked” is used on purpose because uncovering issues associated with it are usually discovered during an installation site survey. These discoveries may have remediation costs that can result in budget deviations, construction delays, and/or potential project cancellation. For reference; Telecommunications Rooms, cable pathways and other structural design elements are well documented in the EIA/TIA-569B specification.
Use this diagram as a reference (source):
Let’s explore the elements of a Telecommunications Room and the ramifications associated with an inability to meet the needs of an installation.
- Rack Space – Vertical rack space is usually discussed in terms of Rack Units “RU” that are 1.75” high. If the present rack in a Telecommunications Room does not have enough free RU’s to house the equipment required for the installation, an additional rack can be added. If the room does not have enough space for an additional rack, it may need to be physically expanded. This is an expensive project that could result in delay/cancellation of cellular service improvement. See this for additional details on standard 19” computer racks.
- Rack Clearance – There is equipment that could be only one RU in height, but have special requirements that an incumbent rack may not be able to satisfy.
- Enterprise has a two post rack and the telecom equipment requires a four post rack due to equipment depth. Equipment is mounted to a rack by a “rack ear” attached to each side. The ears can only take a certain amount of downward stress, and deeper equipment needs the support of the additional two posts in rear of rack. If there are enough RU’s available for an installation and necessary additional physical floor space inside the Room, then the project budget and schedule must accommodate changing the rack.
- Enterprise has no rear access to the rack as the room is very limited in it’s depth. If the telecom equipment requires rear access, the room has to be physically expanded (move one or more walls outwards). This can be an expensive proposition and, in some cases, impossible due to configuration or adjacent use of floor space around the room.
- Uninterruptible Power Supply “UPS” – This is a design choice of each mobile operator and there are three options for AC power failure:
- Utility Power only – design UPS for X hours of uptime under X kilowatts of load. X hours is specified by the operator.
- Protected Backup – “protected” assumes a generator supplies backup power if Utility power fails. Design UPS for 15-30 minutes of uptime under X kilowatts of load. The uptime needs to be sufficient for the generator to come online after a Utility power failure.
- No UPS – mobile devices fail to the macro-cellular network in event of power loss that takes down indoor cellular service.
Note that a UPS can either require vertical RU’s of space in a rack or wall mount in the room. Either option requires space and cable route planning.
- AC Power – Depending on the needs of the additional telecom equipment, additional dedicated circuits from serving AC distribution panel may be required. There can be additional costs if a dedicated circuit must be run from an AC distribution panel that is on a backup generator.
- Heating, Ventilation, Air Conditioning “HVAC” – the HVAC systems managing the temperature in the Telecommunications Room must be able to handle the additional BTU load generated by new equipment added for the indoor cellular improvement. It is recommended to supply the combined BTUs generated by the gear to the enterprise IT/facilities people to make sure the HVAC can support the additional load. We use a handy Watt-BTU conversion tool located here.
Now, let’s connect this to indoor small cell architectures.
When E-RAN is deployed using a VLAN carved out of the existing enterprise network, impacts are:
- No physical RU’s consumed in the rack.
- Additional HVAC load of 78.5 BTU/hr (23W) per PoE+ attached Radio Node.
- No additional AC outlets required.
For alternate indoor architectures that have originated by downsizing outdoor macro-cellular technology, they have separate technology end-to-end from the enterprise that has these impacts:
- RU Consumption.
- 1-2 RU’s for separate Cable Patch panel.
- Up to 12 RU’s for IRU/rHUB.
- Up to 6 RU’s for AC-DC Rectifier.
- Additional HVAC load of 700+ BTU/hr per IRU.
- Additional AC outlets as-needed.
- Potential AC-DC rectifier needed to supply -48 VDC.
In following the theme of re-opening the discussion on how indoor cellular should be built, infrastructure that is common to all wireless is key to future enterprise use of small cells. In the last post we stated that “Enterprises will not want to acquire solutions that require construction of a parallel network.” That statement is even more important when physical resource constraints and the high cost of remediation of limited rack space, AC power and HVAC enter the equation.
To recap, E-RAN is “enterprise IT friendly” by using:
- Incumbent enterprise cabling and PoE+ Ethernet switches.
- ZERO footprint in Telecommunications Rooms.
- Ethernet PoE+ use that is already planned into HVAC load.
In the next installment, we will delve into the Telecom vertical riser that networks the Telecommunications Rooms throughout a given building back to the main room and/or enterprise Data Center.
– Art King, SpiderCloud Wireless, Director of Enterprise Services & Technologies
Other posts from the Enterprise Deployment Series:
- Enterprise Deployment – Setting the Stage
- Enterprise Deployment – Ethernet and the Physical Layer
- Enterprise Deployment – Telecommunications Room
- Enterprise Deployment – Telecommunications Room Interconnection
- Enterprise Deployment – Equipment Room
- Enterprise Deployment – Backhaul
- Enterprise Deployment – Summary