Oct 15, 2021
Utilizing cellular networks – Understanding Network and Security for Far-Edge Computing
In this main section we will take a closer look at the different cellular networks and understand how we can utilize them. We will mainly cover 4G/LTE, 5G, C-V2X, and NB-IoT.
4G/LTE
What is known as 4G/LTE is not a single specification. It is a family of technologies that set out to meet a proposed definition of 4G laid out by the ITU in 2008. Its designers had the following improvements in mind over 3G:
Fully packet-switched (3G was circuit-switched)
Peak data rates up to 100 Mbps for mobile devices
1 Gbps for stationary devices such as 4G hotspots
Increased density of devices per cell through resource sharing:
Figure 3.20 – An example of a 4G/LTE network
How 4G/LTE is implemented varies considerably between Mobile Network Operators (MNOs). There are also key differences in how a given MNO’s 4G/LTE network functions across regions9. MNOs began rolling out 4G/LTE networks around 2011, and it was 2016 before MNO coverage could be considered widespread.
9 The Americas, Europe, Africa, and Asia all had different regulatory constraints that drove this.
Evolved Node B (eNodeB)
The part of a 4G/LTE network you are likely most familiar with is the front end – the ubiquitous cell tower. In 4G/LTE parlance, these are known as eNodeBs. They are elements of a standard cellular network component known as the Radio Access Network (RAN). They include antennas, transceivers, and radio access controllers.
Evolved Packet Core (EPC)
Note that 4G/LTE base stations (eNodeBs) only communicate with each other directly for control plane functions, such as to hand off a device from one tower to another.
Figure 3.21 – 4G/LTE logical architecture
Otherwise, communication needs to go through one of the subcomponents of EPC:
Serving gateway (SGW): Routes user data plane traffic, either between mobile devices or out to other EPC functions, such as a Packet Data Network Gateway (PGW). It also provides core network services such as routing, switching, and transport of data packets.
Packet data network gateway (PGW): Routes user data-plane traffic between EPC and external IP networks such as the internet. It’s also responsible for handling the exchange of data between the mobile device and the wider internet, and it consists of several interconnected network elements.
Mobility management entity (MME): This handles critical control plane functions for mobile devices, including authentication, location tracking, and handover signaling.
4G/LTE latency
EPC instances are centralized and often physically distant from the eNodeBs in a cellular network.
Figure 3.22 – 4G/LTE hairpin routing
Because user data plane traffic has to go back up to the EPC layer to be routed (this is known as hairpin routing), the average RTT on 4G hovers around 50 ms.
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