Source: IEEE Spectrum

Cloud computing has been very boring for a long time. Everything is inside the data center and you don’t even see the systems that you are working on. But not anymore. With Edge Computing, the server is no longer confined to inside the data center. It is out there touching our daily life and computing is happening in real-world and real-time.

Unlike the servers inside the data center which never see the sunlight, edge computers can be covered in snow or exposed to scorching heat in the middle of a desert.ell station out in the desert. Source: MarcoPolisIndoor versus OutdoorCell phone tower damaged by Hurricane in Florida (Verizon)

Indoor versus Outdoor

Compare with an outdoor edge server, a server hosted in the data center is like living in a sheltered environment. With outdoor edge server, it is subjected to random events which cannot be predicted e.g. natural disaster and vandalism. Hence, the design of the outdoor edge server has to be weather proof, water proof and temper proof etc. 

To provide guidance to designers, a two-digit number system was created by the International Electro Technical Commission. Please see the IP Ratings guide below from NEMA Enclosures on how to decode the two-digit number.

The IP Code, or Ingress Protection Code, IEC standard 60529, sometimes interpreted as International Protection Code, classifies and rates the degree of protection provided by mechanical casings and electrical enclosures against intrusion, dust, accidental contact, and water. It is published by the International Electrotechnical Commission (IEC). The equivalent European standard is EN 60529.

The standard aims to provide users more detailed information than vague marketing terms such as waterproof. For example, a cellular phone rated at IP68 is “dust resistant” and can be “immersed in 1.5 meters of freshwater for up to 30 minutes”. Similarly, an electrical socket rated IP22 is protected against insertion of fingers and will not be damaged or become unsafe during a specified test in which it is exposed to vertically or nearly vertically dripping water. IP22 or IP2X are typical minimum requirements for the design of electrical accessories for indoor use. For more details, please visit the web page below.

https://www.nemaenclosures.com/blog/ingress-protection-ratings/

As an example, the picture below is an IP65 design for 5G. That means the design is protected from total dust ingress and from low pressure water jets from any direction.

What Is Inside the Edge Server

An edge server can be a standalone system that handles all the processing locally without being connected to the cloud or data centers. With most of the outdoor edge servers, it will interact with the outside world. What is inside the edge server will depend on the applications. Using different add on cards and software, the edge server can support different applications.

Here is an example of a 5G O-RAN Distribution Unit (DU). In a distributed 5G cloud RAN architecture the DU is collocated with the Remote Radio Unit (RRU). Inside the server, there are two add on cards.

The first card is the Intel® Ethernet 700 Series Network Adapter with Hardware-Enhanced Precision Time Protocol (PTP) which brings higher accuracy IEEE 1588 PTP synchronization signaling to the Ethernet and onto the Edge platform to provide more precise clock synchronization for 5G use cases.

The second card is the Intel FPGA Programmable Acceleration Card N3000. The DU in this example will support 12 sectors of RRUs requiring a large amount of digital signal processing in real time to perform the CPRI-to-eCPRI conversion. This task can be offloaded to the FPGA card. This card accelerates network traffic up to 100Gbps to support low latency and high bandwidth tasks such as FEC acceleration at the PHY layer. (Note. CPRI stands for Common Public Radio Interface and eCPRI stands for Enhanced Common Public Radio Interface.)

Now that we have figured out the hardware inside the edge server, the next step is making it work in an outdoor environment. And this is where the fun begins!

Outdoor Edge Server

To make the edge server ready for outdoor, the first thing we have to do is to match it with an IP65 enclosure so that it can handle the harsh outdoor environments. Since this is for telecom usage, it has to be compliant with the GR-3108-CORE and GR-487-CORE requirements.

After the enclosure is chosen, we need to figure out how to make the edge server work when it is freezing cold or under extreme heat. In this example, the operating temperature range is -40°C ~ 50°C (-40°F ~ 122°F.) To make it work, the design has a high-efficiency heat exchanger and a 300W heater.

To meet the IP65 requirements, the design also has to be temper proof. The enclosure is designed to have lockable buckles, cabinet intrusion detection and self-diagnosis. 

Hardware cannot work without software. While it is not the scope of this article to go into details on the application software that goes inside the edge server, it is important to have robust remote management software as the edge server could be located somewhere that is hard to reach. 

Bringing It All Together

Designing an outdoor edge server can be very challenging. However, making it all work together is the fun part. On top of the hardware and software integration, depending on the type of applications, it’ll have to pass a number of certifications before it can be deployed. And there are a lot of different variables such as how it is being connected to the network, how it is being powered and how it is being secured etc? 

Compare with doing a cookie-cutter server designs for the data center, the increased complexity in designing an outdoor edge server can be very daunting. But it can also be so much more fun once you get everything working.