2017/6/12

Background

1/2

Cellular networks have to accommodate massive M2M/IoTcommunications
Accommodating massive M2M/IoT communication increases
load on mobile core network nodes

Design and performance evaluationof bearer aggregation method
in mobile core networkwith C/U plane separation

 Signaling procedure to establish per-UE bearers which are logical paths
for data packets before UEs start data communication
 For bearer establishment, various signaling messages propagate between
the nodes and are processed on the nodes
Cloud environmentof mobile operator

HSSM2M/IoT UEsMMEeNodeB

PCRF○Shuya Abe, Go Hasegawa, Masayuki Murata

External IP network

Osaka University
SGW/PGW

E-UTRAN

Transport network

6/13/2017

Background

2/2

2PurposeVarious methods for accommodation of massive
M2M/IoT terminals

Performance evaluation of the mobile core network
considering signaling processing load

server virtualization, C/U plane separation, SDN, etc.
Signaling procedure and network slices dedicated to M2M/IoT
communication
Conveying data in C-plane signaling messages

These existing methods

Exploits the number of statements for processing signalingmessages

Bearer aggregation method is proposed and evaluatedShares a bearer by multiple UEs
Decreases the load of bearer establishment

Can utilize server and network resources more efficiently
Can not reduce overhead required for bearer establishment
itself

𝑈𝐸1
No
𝑈𝐸2
Aggregation

Existing researches on bearer establishment overhead are
based on the number and size of the signaling messages

𝑈𝐸3

Actually, the load of signaling messages are determined by manyfactors

𝑈𝐸1
Aggregation

𝑈𝐸2
𝑈𝐸3

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Network Model

C/U Plane Separation

UE: Terminal accommodated to the mobile core network

eNodeB: Base station for LTE

Separating SGW/PGW node into C-plane and U-planenodes and moving C-plane node to the cloud

MME: Pillar of signaling procedure for bearer establishment,
Mobility management, Authentication, etc.

SGW/PGW: Anchor point for intra-LTE mobility/

 C/U plane separation decreases propagation delay of signaling messages
between cloud nodes
 Server resources can be shared among cloud nodes
 Additional signaling messages between SGW/PGWc and SGW/PGWd

Gateway to external IP networks
HSS

Cloud environmentof mobile operator

MME

M2M/IoT UEs
eNodeB

PCRF
External IP network

SGW/PGW
E-UTRAN

Transport
networkCloud environmentof mobile operator

HSS

Bearer(Data path)

MME

M2M/IoT UEs

PCRF

eNodeB

SGW/PGWc

C-planesignaling(for bearerestablishment)
5

SGW/PGWd

External IP network

Transport
network
E-UTRAN

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Control plane signaling
SDN signaling61

2017/6/12

Bearer Aggregation

Aggregation PointSharing a bearer by multiple UEs

Aggregation at SGW Shares bearers between SGW and PGW (S5/S8 bearer) Requires small modification to the mobile core network S5/S8 bearer is kept
No aggregation
established when UE
becomes idle
eNodeBDecreases signaling messages and node processing forestablishing per-UE bearers
Increases signaling messages and processing for bearer
aggregation

Aggregation PointNo
𝑈𝐸2
Aggregation
𝑈𝐸3

Aggregation Timing

𝑈𝐸1

When UEs attach (connect)
to the mobile core network
When UEs start
communication

Aggregation

𝑈𝐸2

 Shared S1-u bearer must bekept established until all UEs
become idle

𝑈𝐸3

Data PacketAggregation Point

Aggregation TimingUEs

PGW
SharedS5/S8 bearer

S1-u bearer

RRCs

Aggregation

SGWeNodeB

Aggregation at eNodeB (3 UEs -> 1 bearer)
Aggregation

eNodeB

UEsRRCs

7PGW
S5/S8 bearer

Aggregation at SGW (3 UEs -> 1 bearer)

D-Plane Bearer

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SGW

S1-u bearer

RRCs

Shares bearers between
eNodeB and SGW(S1-u bearer)
S5/S8 bearers are also
aggregatedRequires large modification
to the mobile core network

𝑈𝐸1SGW
eNodeBUEs

Aggregation at eNodeB

SGW
SharedS1-u bearer

PGW
SharedS5/S8 bearer

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8Aggregation Timing

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Pre-determined Aggregation

On-demand Aggregation

A UE is associated with a shared bearer
when the UE attaches to the network

A UE is associated with a shared bearer
when the UE starts data communication
Each UE must wait for the communication requests until thenumber of requests reaches the number of UEs in each group(aggregation level)
Only one data path setting procedure is necessary when thenumber of requests reaches aggregation levelA shared bearer is activated when it is not established
The data path setting to data plane nodes is necessary foreach UE
BearerEstablishment

NodeProcessing

Data Path
Setting for 𝑈𝐸1

NodeProcessing

Data Path
Setting for 𝑈𝐸2(Wait Time)(Wait Time)

NodeProcessing
Msg. arrival(from6/13/2017
𝑈𝐸1)

Msg. arrival(from 𝑈𝐸2)

AssignvIMSI

Data Path
Setting for 𝑈𝐸𝑘

Msg. arrival(from 𝑈𝐸𝐾 )t9

Msg. arrival Msg. arrival(from6/13/2017
𝑈𝐸1) (from 𝑈𝐸2)

BearerEstablishment

Propagation DelayEvaluation metrics

Propagation delay depends
on distance between nodes

𝑇 is the sum of the followingtimes
𝑇τ : Propagation delay𝑇𝑡 : Processing time𝑇𝑤 : Waiting time
when on-demand aggregation

 In the cloud environment: small delay Between cloud nodes and E-UTRAN /Transport network: large delay

Propagation
Delay
BearerEstablishment
Time

NodeProcessing

Data Path Setting for
𝑈𝐸1 , 𝑈𝐸2 , … , 𝑈𝐸𝐾tMsg. arrival(from 𝑈𝐸𝐾 )Performance Analysis
Bearer establishment time (𝑇):
Execution time required forthe signaling procedure

NodeProcessing
NodeProcessing

10Propagation
Delay

The number of propagations ofsignaling messages is determined bythe signaling procedure
Cloud environmentof mobile operator

HSSMME

ProcessingTime

M2M/IoT UEs

PCRF

eNodeB

SGW/PGWc

External IP network

𝑻 = 𝑻τ + 𝑻𝒕 + 𝑻𝒘

SGW/PGWd
GTPTransportnetwork
E-UTRAN

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Control plane signaling
SDN signaling122

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Processing Time

Evaluation Results

M/G/1/PS queuing model is exploited
Signaling
Message

Subsequent
Signaling
Message𝑬𝑹

Node𝑬𝑺𝝀 Average processing time at a node 𝑬 [𝑹]𝑬𝑹 =𝝆 𝒓 𝑬 𝑺𝟐
𝟏 − 𝝆𝒓+𝑬[𝑺]
𝟏 − 𝝆 𝟐𝑬 𝑺
𝟏 −𝝆Variable in queuing modelRelated Parameter in evaluation

λ: Arrival rate(of signaling messages)# of UEs, # of processing, # of the nodes,
UE’s communication frequency

E S : Mean workload(Ave. signaling processing time)

Ave. # of statements, Server resources

ρ: System utilization

λ, E[S]

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Effect of Aggregation Point

Aggregation methods for evaluation combine
aggregation point and aggregation timing
Aggregation level (# of UEs for each shared bearer):64
Server resources and propagation delay are
determined assuming a nation-wide mobile corenetwork

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14Effect of Aggregation TimingBearer establishment time increases sharply with acertain number of accommodated UEsNASGW + PredeterminedDefined as ``network capacity''
NASGW+ Predetermined

eNodeB+ Predemand

SGW + OndemandOn-demand aggregation (OA)
has larger network capacity
than Pre-determined With OA, only one data pathsetting procedure is necessaryfor each group of UEs

Network capacity further
increases by applying abearer aggregation
methodOA has a large bearer
establishment time when thenumber of UEs is small

Aggregation at eNodeB
has larger network
capacity than that at SGW Caused by waiting time The number of total
bearers in the network issmaller

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Discussion

Conclusion

Recommended combinations of aggregation point
and timing is determined depending on thenumber of UEs and the mobility of UEs
The amount of modification depends on theaggregation method

SummaryUEs’ characteristics

Point

TimingRequired
modification

Network
capacityhigh mobility

SGW

Pre-determinedsmalllowmassive, high mobility

SGW

On-demandsmall

mediumlow/no mobility

eNodeB Pre-determined

large

high

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Evaluation of bearer aggregation methods to aggregate
multiple M2M/IoT communication
Bearer aggregation methods improve the performance ofthe mobile core network
Appropriate aggregation method is determined dependingon the characteristics of accommodated UEs

Future work
C/U plane separation at eNodeBEvaluation of U-plane performanceExperimental evaluation to support the results

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Propagation Delay

Backup Slide

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19

Nodes

Delay

UE – eNodeB

20 msec

eNodeB – SGW/PGWd

7.5 msec

eNodeB – MME

10 msec

SGW/PGWd – SGW/PGWc

10 msec

MME – SGW/PGWc

1 msecGTP module – SGW/PGWd

1 msec

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Server Resources
NodeServer Resources

UE

3,000 statements/sec

eNodeB

1,500 statements/sec

MME

3,000,000 statements/sec

SGW/PGWc

3,000,000 statements/sec

SGW/PGWd

3,000,000 statements/sec

GTP module

600,000 statements/sec

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