dimensioning of the shared transport network for ... · 10 r s1_lte (k) or r iub_hs . comnets...
TRANSCRIPT
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Dimensioning of the Shared Transport Network for Collocated Multiradio: LTE and HSDPA
Ming Li, M.Sc. FFV Workshop 2012-II
October 19th, Hamburg
X. Li, M. Li, U. Toseef, D. Dulas, M. Nowacki, A. Timm-Giel, C. Goerg, R. Ruchala, “Dimensioning of the Shared Transport
Network for Collocated Multiradio: LTE and HSDPA” in the WiMob 2012, Barcelona, October, 2012.
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Shared Transport Network for Collocated Multiradio
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Different radio technologies (2G, 3G, LTE)
will still coexist for some time
How to aggregate the traffic?
How much gain do we have?
How to dimension the common link?
Shared Transport Networks(IP Based)
Internet Cloud
We propose a multiradio shared transport system
• Reduced costs on renting transport resources
• Maximized reuse of existing infrastructure
• Provide smooth migration to new
technologies (LTE and LTE-Advanced)
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Our Focuses and Contributions
• Our Focuses – Focus on the elastic traffic (TCP-based traffic)
– Cover the User-Plane interfaces (LTE: S1; HSPA: Iub)
– Only the DL direction is considered
• Our Contributions – Investigate the shared transport network
• Proposed a QoS framework
• Analysis of the achievable sharing gain (bandwidth saving)
– Propose analytical models to dimension the shared link • Reduce the dimensioning time from hours/days to several seconds
• Portable dimensioning tools are implemented
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Process Sharing Model for Elastic Traffic
• The dimensioning model for elastic traffic (TCP-based traffic) is based on M/G/R-PS Model
– Due to TCP flow control all TCP flows share the link bandwidth equally the system can be modeled as a Processor Sharing system
– The M/G/R-PS Model has been used for dimensioning
• networks, e.g. IP network, ADSL, etc.
• mobile networks, e.g. UMTS
M/G/R-PS Model
Processor Sharing-Poisson Arrivals
Departures
1
2
R
Peak data rate
File length
Link utilization Delay factor
Number of servers
R = C / rk
Average File Transfer Delay of QoS class k
2 ( , )( ) 1
(1 )
k k k k kk k
k k k k
x E R R xT x f
r R r
Xi Li (PhD thesis): “Radio Access Network Dimensioning for 3G UMTS”. Vieweg+Teubner Verlag, 2011.
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R = C / rk
C: Link capacity
rk : Flow peak data rate
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WFQ Scheduler
AF31 PHB
AF21 PHB
AF11 PHB
BE PHB
Transport Network
IP DiffServ QoS Class based on PHBs
(Per Hop Behavior)
Transport Scheduler
Dimensioning Models
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Weighted
M/G/1-PS
M/G/R-PS
Extended M/G/R-PS
for DiffServ with WFQ
HSPA
LTE
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Dimensioning Framework for Elastic Traffic (nGBR)
LTE Air Interface
Model
Weighted
M/G/1-PS
Shared Transport
Model
Extended M/G/R-PS
for DiffServ with WFQ 𝑟𝐼𝑢𝑏_𝐻𝑆
Traffic load per
PHB
WFQ weight
File size
Shared transport capacity
App. delay per PHB TN
Delay
Model
TN delay per PHB • Cell capacity
• QCI types
• Traffic model
• QCI weights
• …
HSDPA Air Interface
Model
M/G/R-PS
• Cell capacity
• Cell load
• UE category
• UE peak data
rate
• #UEs
scheduled
per TTI
• …
𝑟𝑆1_𝐿𝑇𝐸(𝑘)
eNB/NB
RNC/
aGW
Shared TN
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Modeling the LTE air interface
Estimate the avg. UE Uu throughput of Elastic traffic (nGBR) with Weighted M/G/1-PS Model
o Model Parameters for elastic traffic
- Air interface capacity of a LTE cell: CUu_LTE
- the defined QCI weight for the QoS class k in LTE MAC scheduler: WQCI(k)
- Mean traffic load of the elastic traffic of QoS class k: LUu_LTE(k)
a) Step 1: calculate the available cell capacity used for elastic traffic of QCI class k
b) Step 2: calculate the estimated peak data rate at the LTE S1 interface for each QCI class k
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_ _ _ _
( )( ) max , ( )
( )
QCI
Uu LTE Uu LTE Uu LTE Uu LTE
j kQCI
i
w kC k C C L j
w i
1_ _ _( ) ( ) ( )S LTE Uu LTE Uu LTEr k C k L k
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Estimate the avg. UE Uu throughput of Elastic traffic (nGBR) with M/G/R-PS Model
o Model Parameters for elastic traffic
- Air interface capacity of a HSDPA cell: CUu_HS
- Peak data rate (bits/s) of a HSDPA bearer (TCP flow): rHS
- Mean traffic load of all elastic traffic in a cell: LUu_HS
a) Step 1: calculate the air interface delay factor
b) Step 2: calculate the estimated peak data rate on the Iub interface
Modeling the HSDPA air interface
HSUu
HSUu
HS
HS
HSUu
HS
HSHS
HSHSHS
HSUu
C
Land
r
CRwhere
R
RREf
_
__
2
_)1(
),(1
HSUuHSHSIub frr __ /
1
0
2
!!
!),(R
i
Ri
R
AR
R
R
A
i
A
AR
R
R
A
ARE
# Servers Link Utilization Delay factor
Erlang’s second formula (Erlang C formula)
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Modeling of the Shared Transport Network
The dimensioning model for elastic traffic (TCP-based traffic) is based on extended M/G/R-PS Model*
( ) ( ) / ( )TN TN TNj L j BW j
( )( ) max , ( )
( )
WFQ
TN TN TN TN
i jWFQ
i
w jBW j BW BW L i
w i
2 ( , ( ))( ) 1 ( )
( ) (1 ( )) ( )
j j j TN j
j TN
TN j TN TN
x E R R j xT x f j
r j R j r j
( ) / ( )j TN TNR BW j r j
* Extended M/G/R-PS K. Lindberger (1999)
File Size # Servers
Peak data rate Link Utilization Delay factor
app. mean
delay for PHB
class j
(sojourn time)
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rS1_LTE(k) or rIub_HS
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Validation of the Analytical Dimensioning Models
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LTE Part, 1GB TCP buffer size, 20MHz cell bandwidth
Services Load per cell PHB (WFQ weight)
FTP (QCI9) 8, 12, 16Mbps BE (1)
HSDPA Part, 64KB TCP buffer size, 5MHz cell bandwidth
Services Load per cell PHB (WFQ weight)
FTP 6Mbps AF21 (100)
HSPA only LTE only Shared TN Model0
20
40
60
80
100
120
Transport Network Bandwidth [Mbps]
Scenarios
Ba
nd
wid
th [M
bp
s]
8Mbps 12Mbps 16Mbps0
20
40
60
80
100
120
Transport Network Bandwidth [Mbps]
LTE cell load [Mbps]
Ba
nd
wid
th [M
bp
s]
Analytical
Simulation
Analytical
Simulation
* Dimensioning target: HSDPA 50ms, LTE 15ms 44% 55% 66% 77%
0
5
10
15
TN
Dela
y [
ms]
BE PHB: Analytical
BE PHB: Simulation
AF21 PHB: Analytical
AF21 PHB: Simulation
44% 55% 66% 77%10
12
14
16
18
20
Transport link utilizationF
ile d
ow
nlo
ad
dela
y [
s]
BE PHB: Analytical
BE PHB: Simulation
AF21 PHB: Analytical
AF21 PHB: Simulation
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Analysis of the Achievable Sharing Gain
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0
5
10
15
20
25
30
35
40
1 2 3 4 5 6 7 8
Sh
ari
ng
ga
in [
%]
LTE/HSDPA cell load [Mbps]
LTE/HSDPA Sharing Gain
0
2
4
6
8
10
12
14
16
18
20
10 20 30 50 70 80 90
Sh
ari
ng
ga
in [
%]
HSDPA load share [%]
LTE/HSDPA Sharing Gain
Sharing gain decreases with the increased cell loads.
Higher when HSDPA percentage is higher than LTE
highest when equal load
* Dimensioning target: HSDPA 15ms, LTE 15ms
𝑆ℎ𝑎𝑟𝑖𝑛𝑔_𝐺 = 1 −𝐵𝑊𝑆ℎ𝑎𝑟𝑒𝑑_𝑇𝑁
𝐵𝑊𝐻𝑆 + 𝐵𝑊𝐿𝑇𝐸⋅ 100%
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Summary
• A multiradio shared transport system is presented, and developed in a system simulation model in OPNET.
– Both application and Transport network delays are improved
– Around 20~30% gain on bandwidth saving from the example scenarios
• Propose an analytical framework to dimension the shared transport interface for the elastic traffic based on the extended M/G/R-PS model
– Modeling the LTE/HSDPA radio interface
– Modeling the DiffServ QoS scheme in shared transport network
– Dimension the shared transport network to fulfill the QoE/QoS requirements
• The presented validation results demonstrate the proposed analytical models
– Can appropriately estimate the application/link level performances of different traffic and priorities
– Can estimate the achievable LTE/HSDPA sharing gain from sharing the transport
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Next Steps
• Extend the dimensioning models for multiple base stations (eNBs, NBs) scenarios, and other traffic types
• Adding other radio technologies like HSUPA, GSM and UMTS Rel’99
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