A presentation and video by Ben Toner, Founder & Director, Numerous Networks exploring the convergence of Mobile, Broadband and Wi-Fi *** SHARED WITH PERMISSION *** All our #3G4G5G slides and videos are available at: Videos: https://www.youtube.com/3G4G5G Slides: https://www.slideshare.net/3G4GLtd 5G Page: https://www.3g4g.co.uk/5G/ Free Training Videos: https://www.3g4g.co.uk/Training/

1. Exploring the convergence of Mobile, Broadband and Wi-Fi Brought to you by
www.numerousnetworks.co.uk
ben@numerousnetworks.co.uk
• What is Convergence and why do we need it
• 3GPP ATSSS
• Other convergence options
• How do you try it today
• The modes of convergence
Network Convergence
November 19 1
Numerous Networks provides consultancy and technical services to help anyone who wants to use Wi-Fi as a
serious mobile offering and get the best experience out of their infrastructure. That involves ensuring Wi-Fi
services are ready for mobile use while providing options to converge Wi-Fi, cellular and broadband together
for the best uninterrupted user experience.
Numerous Networks have been enhancing the user experience of carrier grade Wi-Fi for more than 10 years.

2. The Need
• BT are one of the largest
companies to state the
importance of convergence
in their strategy
November 19 2
“Seamless, consistent connectivity ” – Howard Watson, CTIO BT

3. The overall objective is to converge an user’s experiences into a
single expected experience.
• Network convergence is part of the required technical approach
• Primary network modes
• Home Wi-Fi / Office Wi-Fi / Public Wi-Fi
• Cellular
• Transitionary network modes
• Leaving Home Wi-Fi to use a cellular connection
• Arriving at the Office Wi-Fi from a cellular connection
• Stepping into a coffee shop and using public Wi-Fi
• Failure Modes
• Filling in congested (slow) Home DSL backhaul with fast 4G
cellular
• Filling in slow public Wi-Fi with fast 4G cellular
• Supplementary network modes
• Adding cellular to slow Wi-Fi to create a minimum speed
• Add cellular to DSL backhaul to deliver a minimum
public/private Wi-Fi
• Service differentiating network modes
• Local firewalled / VPN’d network for internal enterprise data
• Public network to connect to secure enterprise cloud
Predictable
service at a
predictable
cost
It should not
cost me more
than I expect
I should not
have to know (or
care) about
what I am
connected to
It should always
(typically)
perform to a
minimum
standard which I
am paying for
What is causing the need
November 19 3

4. Start services at home on Wi-Fi Drive away:
Weak Wi-Fi = bad app experience
1 2
Convergence solves this problem
The role of convergence for everyday network issues
November 19 4

5. What is Convergence
The use of Multiple Networks
The Simple Description
Home Wi-Fi
Public Wi-FiPublic
Cellular
Private
Cellular
To deliver a Combined or Converged Network
Capable of providing the end user with access to the Data
Network at a quality level which they expect
November 19 5

6. Defining Documents
A sample of the bodies defining and standardizing the next generation of convergence
Recommended Read
A great summary directed towards supporting
broadcast and multimedia
http://5g-xcast.eu/wp-content/uploads/2019/07/5G-
Xcast_D4.2_v3.0_web.pdf
Convergence Standardisation Bodies
November 19 6

7. Defining Documents
ATSSS is optional and has a preliminary specification + Technical Report to guide the evolution
Convergence in 3GPP
Initial Specification allows ATSSS to be implemented using MP-TCP as it has some adoption. e.g. Apple
Technical Report suggests many
more convergence options.
TBD what happens here
Some OTT
solutions might
disrupt here too
November 19 7

8. Mobile Device Convergence
Steering in ATSSS
November 19 8
Network
Wn
Network
W2
• Using multiple networks needs to be simple to the end user;
• all the complexity of selecting the network and managing the
choice of network for the data is automatically handled
• according to some governing rules or requirements
• made by the device or the network or both
Network
C1
Quality
Assessment
Data Path Decision
Network
W1
Quality
Assessment
User Preferences
Service Provider
PreferencesNot noticed by
the end user
Industry term
The procedure for selecting an access network for a
new data flow is known as ‘steering’ the connection
Traditionally
Wi-Fi OR
Cellular
8

9. Mobile Device Convergence
Switching & Splitting in ATSSS
November 19 9
• There is an increasing trend to use multiple connections at the same time to achieve an
experience target;
• No drops. Moving a data flow from one network to another without interruption
• Quick responses. Using multiple networks and selecting the response which
comes back quickest
• More data. Using multiple networks at the same time to increase the bandwidth
• Load balancing. Choosing the network which is least contended / congested
Industry term
The procedure of moving an ongoing data
flow from one access network to another
is known as ‘switching’ the connection
Network
Wn
Network
W2
Network
C1
Quality
Assessment
Data Flow / Packet
Decision & Direction
Network
W1
Quality
Assessment
User Preferences
Service Provider
Preferences
Industry term
The procedure of splitting the traffic of an
ongoing data flow across multiple access
networks is known as ‘splitting’ the connection

10. 3GPP define the Multi-Access Packet Data Unit (PDU)
• The Multi-Access PDU enables the concept of using multiple network access paths to
transfer data from a single data source (such as an application)
• It is fundamental to all multipath approaches
Virtual
Interface
NG-RAN
UPF-2
(optional)
UPF-1
(optional)
UPF-A
IP
5G
WL
AN
Child PDU
session #1
UE
N6
AMF
N2
N2
N3
N3
SMF
N4N11
WLAN
AN
N3IWF
Child PDU
session #2
Multi-Access
PDU session
Multipath PDU as defined by 3GPP R16 in 23.793
A MA PDU Session may be established either:
a) when it is explicitly requested by an ATSSS-capable UE; or
b) when an ATSSS-capable UE requests a single-access PDU
Session but the network decides to establish a MA PDU Session
instead.
Key Concept for Convergence
November 19 10

11. ATSSS Technical Report TR 23.793
extending the support for Steering, Switching, Splitting
However, 23.793 Technical Report proposes Multipath Convergence could take one of the
following options
1. NULL tunnel (IP flow steering)
1. All packets from the same flow are sent on the same access (based on 5-tuple)
2. GRE tunnel
1. Both access types can be used at the same time over individual tunnels
3. Trailer based L3 Generic Multi-Access (GMA)
1. Trailers used to allow for packet ordering when using multiple access
4. User Plane Convergence using L4 multipath
1. MP-TCP
2. QUIC / MP-QUIC
3. SCTP
4. UDP Generic
23.50x R16 specifies only one higher layer option which is MP-TCP. Low Layer steering is also
defined as ATSSS-LL but no additional protocol is applied
Only MPTCP specified in R16
Can currently only be NULL tunnel
Other IETF protocol will be allowed
but none are ready
November 19 11

12. Practicalities
• MPTCP is a higher layer multipath protocol which works for TCP flows only.
• It can be difficult to schedule traffic in order to avoid head of line blocking
• Other methods such as MP-QUIC aim to remove these difficulties and also support all traffic types
• Some non-TCP applications cannot fall back to TCP and will not benefit (e.g. some real time
voice/video)
• ATSSS- Lower Layer is suitable for steering and switching flows of any type
• It applies no additional protocol so could only be used for steering (today) and maybe switching in
the future
• It is required for all ethernet PDU types
• Something similar is available TODAY on some broadband / LTE hybrid home equipment
• And as over the top applications on smartphone devices. (They currently need to use the
VPN service on the UE to capture all the traffic)
• No mention of dual 3GPP Access – Private LTE (e.g. CBRS) + Public LTE
• Even where the device has 1 radio, the use case for seamless handover in a Dual-Sim Dual-Standby
(DSDS) environment is important for offload continuity
3GPP R16 ATSSS and the practicalities
November 19 12

13. Broadly based on Generic UDP L4 convergence
• These challenger solutions are implementing a proprietary UDP approach to perform aggregation
• There are 3 deployment models
• On mobile devices there are two integration methods
• SDK integrated into an application, acts similar to an L4 aggregation such as MPTCP or
MPQUIC
• Whole device aggregation using the VPN service to capture traffic. All applications see a
virtual IP address of the aggregation tunnel to the aggregation server (equivalent to ATSSS)
• For Home Gateways and Access Points an SDK exists which can be integrated into the network
stack
• All traffic types can be supported
• New congestion control is implemented to optimise the use of the links and has been empirically tuned to
suit the varying latencies between Wi-Fi and Cellular networks
• Enhancements such as Forward Error Correction are already in use in these solutions
• Up to date encryption can be used (but will be an overhead)
• Provides all the desired aggregation modes and is already tuned for mobile behaviour
• Offers out of box redundancy and gapless handover for real time media streams (e.g. IP calling)
• Offers aggregation to achieve a minimum bandwidth while preferring a primary low cost access
when available.
Other non-standardized challenger solutions
November 19 13
Any application
traffic
Captured by VPN
Proprietary Congestion Control /
re-ordering scheme / packet-
access assignment / FEC /
encryption
Dual IPSEC tunnels
Single virtual interface

14. Multipath TCP
From Tessares;
a major contributor to the MP TCP IETF RFC
Multipath QUIC
From Quentin De Coninck;
a major contributor to the MP QUIC IETF RFC
Source Code
Proprietary UDP
From Connectify;
The largest distributed public over the top application
Implementations available to try user plane
convergence on your own mobile device – today!
ATSSS future (as defined in TR23.793) expects to allow for any one of these options:
User Plane Convergence Method using L4 Multipath Solutions (MP-TCP, QUIC, MP-QUIC, SCTP, UDP generic)
November 19 14
Various other
proprietary UDP solutions exist

15. Using rules to manage ATSSS
• After the establishment of a MA PDU
Session, the UE receives a prioritized list
of ATSSS rules from the SMF
Structure of the ATSSS rule
• Traffic steering policy: This rule is used to select an access
when initiating a new data flow.
• Traffic switching policy: This rule is used to determine when a
data flow should be moved from 3GPP to non-3GPP or vice
versa.
• Traffic splitting policy: This rule is used to determine when a
data flow should be split across 3GPP and non-3GPP.
November 19 15

16. How performance is measured and governed
measures which feed into rule set
PCF (Policy) sets rules
Loss, Latency, Jitter Measures
Traffic distribution based on ensuring
no packets get out of order
Performance Management Function
• Requires measurement and reporting of Packet Loss, Jitter,
RTT
• Need careful combination to avoid rapid switches and bad
decisions
November 19 16

17. Networks are combined to provide a user experience target which includes
stability or consistency of the connection, perceived minimum speed and
optimisation of cost to the end user and service providers
Tech Capture
3GPP description of convergence options. Part 1
Steering Mode = Active-Standby
MA-PDU
Session
Non-3GPP
Access
3GPP
Access
Data flows to be sent over
the MA-PDU session
Active Standby
Steering Mode = Priority-based
Non-3GPP
Access
3GPP
Access
Data flows to be sent over
the MA-PDU session
MA-PDU
Session
Overflow
traffic
High
Priority
Low
Priority
Typical fallback
scenario such as a
home broadband
router. The primary
access is preferred
unless it is failing
Certain traffic types
are assigned to a
priority network.
Fallback to a low
priority access occurs
of there is
performance
impairment
November 19 17
Modes of Convergence - 1

18. Combination options exist to handle multiple use cases where traffic can be
overflowed or copied onto an alternative network
Tech Capture
3GPP description of convergence options. Part 2
Steering Mode = Best-Access
Non-3GPP
Access
3GPP
Access
Data flows to be sent over
the MA-PDU session
MA-PDU
Session
Best
access
Overflow
traffic
Steering Mode = Redundant
Non-3GPP
Access
3GPP
Access
Data flows to be sent over
the MA-PDU session
MA-PDU
Session
When the user choice
may not matter (e.g.
unlimited data plan)
Use best network (e.g.
smallest delay) and
overflow to secondary
to ensure minimum
service quality
All traffic copied. Rare
but found today in some
over the top applications
offering gapless handover.
The redundancy is
generally only happening
during a transition period
when the primary
network quality is below
standard
November 19 18
Modes of Convergence - 2

19. More networks = more opportunities to provide a quality of service to the
customer while balancing the load between networks.
Tech Capture
3GPP description of convergence options. Part 3
Steering Mode = Load-balance
MA-PDU
Session
Non-3GPP
Access
3GPP
Access
Data flows to be sent over
the MA-PDU session
50% 50%
Data is split between the
access on a percentage basis
(only suitable for non-GBR
flows)
November 19 19
Modes of Convergence - 3

20. MPTCP Scheduling and the importance of head of line blocking mitigation
http://blog.multipath-tcp.org/blog/html/2014/03/30/why_is_the_multipath_tcp_scheduler_so_important.html
DT slides on convergence testing experience
https://mailarchive.ietf.org/arch/msg/banana/Z6ch6F50ICL8E5DKEox2Qcw-yl4/2
Links
November 19 20
Huawei's GRE Tunnel Bonding Protocol
(Informational)
https://tools.ietf.org/html/rfc8157
Generic Multiple Access (GMA) Convergence
(Informational)
https://tools.ietf.org/html/draft-zhu-intarea-gma-04
https://datatracker.ietf.org/wg/mptcp/documents/
https://tools.ietf.org/html/draft-deconinck-quic-
multipath-03
Recommended Reads
5G X Cast
A great summary directed towards supporting
broadcast and multimedia
http://5g-xcast.eu/wp-content/uploads/2019/07/5G-
Xcast_D4.2_v3.0_web.pdf
https://www.itu.int/rec/T-REC-Y.3130-201801-I/en
https://www.broadband-
forum.org/technical/download/TR-348.pdf
https://www.broadband-
forum.org/technical/download/TR-378.pdf
https://portal.3gpp.org/desktopmodules/Specificatio
ns/SpecificationDetails.aspx?specificationId=3254