Evolution

1G: Analog voice (1980s)
2G: Digital voice (1990s)
3G Mobile data (2000s)
4G Mobile broadband (2010s)
5G "Wireless Edge" (2020s)

Each generations lasts +- 10 years
For each new generation:
First 5 years, a set of requirements are set
The implementers fight and develop
We try to standardise, based on developments
In every generation, we want more throughput, efficiency and reliability (but throughput most of all)

Legacy Architectures

Called cellular because coverage area is divided into regions called cells
Each cell will have 1 base station
When you move form one cell to another, you will switch to a new base station (handover)
Air-interfcae: physical and link-layer protocol between mobile device and base station

2G

Cells are further grouped
Base stations grouped into Base Station System (BSS)
Controlled by a Base Station Controller (BSC)
Linked up to a Mobile Switching Centre (MSC)
MSC hooked up to gateway

3G: Voice + data

Base Station Controller -> Radio Network Controller (RNC)
Adds Serving GPRS Support Node (SGSN)
and Gateway GPRS Support Node (GGSN)
Both are essentially routers
SGSN also does some mobility management

4G

The solution for wide-area mobile internet
Higher peak speeds
Running on 450MHz-6GHz
LTE standard
Came from 3rd Generation Partnership Project (3GPP)

International Telecommunication Union (ITU) came with a new 4G directive:
All IP switched
Higher data rates and better efficiency
Dynamically share network resources
Smooth handovers across heterogenous networks (e.g. 2G 3G)
High quality service for multimedia applications

LTE:
OFDMA: frequency AND time multiplexing
4x4 MIMO for more throughput, availability and signal strength
Modulation up to 64QAM (more bits per symbol)

LTE advanced:
Worldwide functionality & roaming
Interworking with other radio access systems
Enhanced data rated
Relay nodes (repeaters) to increase coverage
5x20MHz bandwidth
8x8 MIMO
Modulation up to 256QAM

• Mobile device
  • e.g. smartphone, tablet. Anything with an IP
  • Has International Mobile Subscriber Identity (IMSI) stored on your Subscriber Identity Module (SIM) card
  • A.k.a User Equipment (UE)
• Base station
  • The "antenna" you connect to
  • Manages radio resources and all devices in its area (cell)
  • Coordinate device authentication based on IMSI with other elements
  • Similar to wifi AP, except
    • Also handles mobility between cells
    • Coordinates with nearby base stations to optimise radio usage (inter-cell interference coordination)
  • A.k.a. eNode-B
• Home Subscriber Service (HSS)
  • Stores info about devices for which this HSS is their "home network"
  • Works with Mobility Management Entity (MME) in device auth
• Gateways
  • Serving Gateway (S-GW) and PDN Gateway (P-GW)
  • On path from device to/from internet
  • P-GW
    • Gateway to mobile cellular networks
    • Looks like any other gateway router
  • Other routers make extensive use of tunnelling
• Mobility Management Entity (MME)
  • Handles device authentication, coordinated with the home network HSS
  • Establishes bath from base station to P-GW (through tunnelling)
  • Mobile device management
    • Handover between cells
    • Tracking/paging device location

Evolve Packet Core

Interfaces:
S11 interfaces between MME and S-GW
S5/S8 interface between S-GW and P-GW
Control plane and data plane traffic
S1 interfaces between E-UTRAN (base station) and Evolve Packet Core (a.k.a just core)
X2 interfaces between base stations

Data- and Control Plane separation

Protocol Stack

Use ACK and NACK since we use a wireless (unreliable) medium, and control traffic should not be lost

"Downstream" ??
Use OFDMA
Each device gets one or more 0.5ms time slots over 12 frequencies (PRBs)
Scheduling is up to the operator
"Upstream" ??
Use SC-FDMA
Power/spectral efficient, more complex to implement

TL;DR

• 15 more protocols follow
• 6 types of bearers
• Mobility management & handover

Associating with a base station

X2-Mobility Management

5G

Goal:
10x increase in peak rate
10x decrease in latency
100x increase in traffic capacity
New millimeter wave frequencies (24GHz-52GHz)
These do not have as much range, so we need denser deployment
Not backwards compatible, need new hardware

Three key application areas:
Enhanced Mobile Broadband (eMMB)
Ultra-reliable and low-latency (URLLC), e.g. vehicle-to-vehicle, or 3D gaming
Massive Machine Type Communications (mMTC): a lot of devices with low data rate

5G Slicing

A 5G slice is composed of a collection of 5G network functions and specific Radio Access Technology (RAT) settings that are combined together for the specific use case or business model

• Optimised service delivery for different use cases
• Multiple independent instances on the same physical network
  

(Non-)standalone 5G

5G depending on the 4G core, only changing the radio access part
Allows faster and cheaper rollout
Not yet a killer application that makes us need standalone 5G
In standalone, deploy a whole new 5G core
Less than 5% in Europe

5G Service-based architecture

We love micro-services

• Session management
• IP address allocation
• Signalling between core and device
• Authentication
• Security
• Mobility (Access and Mobility Function & Session Management Function)
• ...

NRF: Network Repository Function
Helps service discovery
NEF: Network Exposing Function
Exposes network capabilities to applications
E.g. analytics
NSSF: Network Slice Selection Function
Allows the control plane to select the appropriate network slice function based on information provided by the SIM card + network
PCF: Policy Control Function
Creates the QoS rules for different sessions
Identifies how traffic will be treated across the network
AF: Application Function
Interacts with the PCF to request resources for certain applications
UDM: Unified Data Management
Repository of subscriber information
AUSF: AUthentication Server Function
Take the place of the existing XSS

Control plane and user plane are separated

5G QoS model

4G was based on the bearer
Single logical connection to the PDN
5G is based on QoS flow instead
Set of IP flows associated with QoS requirements
Each have a QoS Flow Identifier (QFI)

Two types of flows: those with and without a guaranteed bitrate
QoS flows are part of a PDU sessions
PDU session = notion of a slice in 5G

5G User Plane

5G Protocol Stack

Access Stratum

Non-Access Stratum

N11 Stack = Control Plane communication

6G

Even more services baby