Computing on the Edge: Outdoor Deployment Classes
Fri, 02 Dec 2022 20:21:29 -0000
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Ultimately, all the testing involved with GR-63-CORE and GR-1089-CORE is intended to qualify hardware designs that have the environmental, electrical, and safety qualities that allow for installations from the Central Office, all the way out to the Cell Site. For deployments at the Cell Site, it turns out that NEBS Level 3 is really only the start and the minimum environmental threshold for Cell Site Controlled Environment.
This is where GR-3108-CORE comes into scope. GR-3108-CORE, Generic Requirements for Network Equipment in Outside Plant (OSP), defines the environmental tolerances for equipment deployed throughout a Telecom Network, from the Central Office, to up the tower of the Cell Site, and to the customer premises.
The four Classes of equipment defined in GR-3108-CORE are:
Class 1: Equipment in Controlled or Protected Environments
Class 2: Protected Equipment in Outside Environments
Class 3: Protected Equipment in Severe Outside Environments
Class 4: Products in Unprotected Environment directly exposed to the weather
The primary drivers of these classes include:
- Thermal, including Cold Start and Hot Start
- Temperature and Humidity Cycling
- Salt Fog Exposure
- Closure and Housing Requirements
Class 1: Equipment in Controlled or Protected Environments
The OSP for Class 1 enclosures includes Controlled Environmental Vaults, Huts and Cabinets with active heating and cooling, Telecom Closets in-Building/on-
Building or Residential Locations. The requirements for Class 1 installations are very much in line with NEBS Level 3 specifications with the recurring theme on these enclosures being that there is some active means of environmental control. The methods of maintaining a controlled environment are not specified, but the method used must maintain the defined operating temperatures between -5°C (23°F) to 50°C (122°F) and humidity levels between 5-85 percent.Other expectations for Class 1 enclosures include performing initial, cold, or hot startup throughout the entire temperature range and continued operation if device single fan failures occurs, but at a lower upper-temperature threshold.
Class 2: Protected Equipment in Outside Environments
The internal enclosures or spaces of a Class 2 OSP have an extended temperature range of -40°C (-40°F) to 65°C (149°F), with humidity levels the same as for Class 1. Typically, while these OSPs continue to protect the hardware from the outside elements, environmental controls are less capable and often involve the use of cooling fans, heat exchangers and raised fins to dissipate heat. Besides outdoor enclosures, Class 2 environments can also include customer premise locations such as garages, attics or uncontrolled warehouses.
For hardware designers, creating Carrier Grade Servers, this is where it’s particularly important to pay attention to the components being used when you’re looking at your target Class 2 deployment environment. Many manufacturers will provide specifications on the maximum temperature where the IC component will operate. Typically, the maximum temperature is a die temperature, and the method of heat evacuation is left to the HW designers, in the form of heat sinks, fans for airflow, and others.
However, for those attempting compliance with Class 2, the lower temperature range also becomes important because many ICs are not tested for operation below 0°C. The IC temperature grades generally come in commercial (0°C/32°F to 70°C/158°F), Industrial (-40°C/-40°F to 85°C/185°F), Military (-55°C/-67°F to 125°C/257°F), and Automotive grades.
So the specs for Commercial grade ICs may not even accommodate the requirements of even a Class 1 OSP. So, what do designers do? Sometimes, you’ll see an “asterisk” on the server spec sheet, indicating that the device can run at the lower temperature range, but not start at the lower range. This is where the design can start at 0C and provide sufficient heat to keep the IC warm down through -5°C (23°F).
Designers may also consider including some pre-heater or enclosure heater to bring the device up to 0°C before a startup is allowed or incur the added expense of extended temperature parts.
Class 3: Protected Equipment in Severe Outside Environments
Severe is certainly the theme for Class 3 OSPs. In these environments, while inside an enclosure to protect the device from direct sunlight and rain, the enclosure may not be sealed from other outside stresses like hot, cold and humidity extremes, dust and other airborne contaminants, salt fog, etc. Temperature ranges from -40°C (-40°F) to 70°C (158°F) and humidity levels from 5% to 95%, with single fan failure requirements of 65°C. Certainly, indoor hostile environments, such as boiler rooms, furnace spaces and attics also exist that would require Class 3 designed solutions.
Class 4: Products in Unprotected Environment directly exposed to the weather
This class of equipment is intended for outdoor deployments, with full exposure to sun, rain, wind and all the environmental challenges found, for example, at the top of a Cell Tower. For Telecom, Class 4 certification would typically be the domain of Antennas and Remote Radio Heads. These units, mounted on towers, buildings, street lamps, and other places are fully exposed to the entire spectrum of environmental challenges. Class 4 devices get a bit of a break on temperature, -40°C (-40°F) to 46°C (115°F), due to direct exposure to sunlight, but 100% humidity due to its exposure to rain.
Conclusion
For Carrier Grade Servers, Class 1 (NEBS Level 3 equivalent) is the most common target of designers creating compute, storage, and networking platforms for Telecom consumption. Class 2 servers are also achievable, and their demand may increase as Edge Computing and O-RAN/Cloud RAN deployments become more common, moving beyond Class 2 will require specialty, more purpose-defined designs.