Transition from PSTN
to NGN: Possible
Scenarios
ITU-D Regional Development Forum for the EUR and CIS Region
NGN and Broadband, Opportunities and Challenges
Chisinau, Moldova, 24 – 26 August 2009
NGN – Next Generation Network
ITU-T Recommendation Y.2001:
The NGN (Next Generation Network) is
conceived as a concrete implementation of the GII
(Global Information Infrastructure)
NGN is a packet-based network able to provide
telecommunication services and able to make use of multiple
broadband, QoS-enabled transport technologies and in which
service-related functions are independent from underlying
transport related technologies. It enables unfettered access for
users to networks and to competing service providers and/or
services of their choice. It supports generalized mobility which
will allow consistent and ubiquitous provision of services to
users.
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Incentives of transition to NGN (1)
Historical aspects of the telecom market evolution
Voice services were a “milking cow" for the telecom Operators
in XX century. In XXI century situation changes, although
voice services remain important source of revenue.
Source: B. Jacobs. Economics of NGN deployment scenarios: discussions of
migration strategies for voice carriers. – www.ieee.org.
How much is subscriber eager to pay for broadband access in Russia, per month:
$10 – 31,2%; $20 – 43,8%; $30 – 12,5%; $40 – 6,2%; $50 – 6,2%; >$50 – 0%.
Source: Inform Courier Sviaz, October 2008 (in Russian).
Incentives of transition to NGN (2)
Economical aspects of the telecommunication Operator’s
service
Type of Operator’s costs
Today
Change
Tomorrow
Capital investments share
35%
1,25
43,75%
Operational costs share
65%
0,5
32,5%
Total volume of costs
100%
–
76,25%
Source: P.K. Edholm. Networks transformation: correlation of the resources limitation
and system complexity. – Mobile telecommunications, 2005, №8.
2
Incentives of transition to NGN (3)
Aspects of the traffic change
Incentives of transition to NGN (4)
Aspects of the equipment aging in the telecommunication
networks
3
Incentives of transition to NGN (5)
Aspects of integration and convergence
Specifics of the access networks modernization
Changes in the access network
xDSL
Tone frequency channel
(two-wire circuit)
.
.
.
FTTx
BWA
Broadband paths
Tone frequency channel
(single-wire circuit)
Time
XX century
XXI century
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Statement of the transition to NGN problem (1)
PSTN Operators should find viable strategy of the transition
to NGN, which provides protection of investments in circuitswitched technology.
Source: B. Jacobs. Economics of NGN deployment scenarios: discussions of
migration strategies for voice carriers. – www.ieee.org.
It is necessary to combine PSTN’s quality of service
and IP technologies’ economical efficiency!
Statement of the transition to NGN problem (2)
5
Quality of service indices for the NGN
In the table below QoS indices for six classes are given. These values are defined for the
following indices: IPTD – IP packet transfer delay, IPDV – IP packet delay variation,
IPLR – IP packet loss rate, IPER – IP packet error rate.
Source: ITU-T Recommendation Y.1541.
QoS class
IPTD
IPDV
IPLR
IPER
0
100 ms
50 ms
10-3
10-4
1
400 ms
50 ms
10-3
2
100 ms
U
10-3
3
400 ms
U
10-3
4
1s
U
10-3
5
U
U
U
U
IPDV definition
F(t) - distribution function of the packets delay
1,0
∆=0.001
IPDV = TMAX − TMIN
Time
0
TMIN
TMAX
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QoS aspect: time irreversibility
Speech quality impairment compensation in CS
networks:
Elaboration of the speech signal processing algorithms;
Signal amplification (when necessary).
Speech quality impairment compensation in IP networks
under condition of the excessive packet exchange delay:
Impossible
in principle!!!
QoS aspects: ISO model (1)
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QoS aspects: ISO model (2)
Z – normalized quantity of the IP packet
mean delay between UNIs,
T – propagation time between UNIs,
N – acceptable number of NGN domains
between two terminals:
 Z −T 
N≤
 X + Y 
Modernization principles of the PSTN as a whole
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Scenarios and variants of the transition to NGN
Pragmatic approach towards NGN construction
Initial stage − t0 : K j (t0 ) << M j (t0 ); time t1 : K j (t1 ) < M j (t1 );
dismantling CO (time t2 ) : K j (t2 ) = M j (t2 ) + K j (t2 ).
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Two variants of the transition to NGN
MSAN1
MSAN1
V5.2
V5.2
CO1
MSAN2
CO1
CO2
CO2
MSAN2
V5.2
V5.2
CO3
CO3
V5.2
V5.2
MSAN3
MSAN3
MSAN21
MSAN1
ADSL
R1
VDSL
R2
MSAN22
MSAN2
MSAN11
MSAN23
MSAN24
MSAN3
a) Variant of the NGN
construction without change of
the existing network
MSAN25
Served area of the
dismantled CO3
b) Variant of the NGN
construction with changes
according to preconceived plan
Modernization of the urban network
with transit exchanges (1)
10
Modernization of the urban network
with transit exchanges (2)
MSAN11
(61)
IP network with QoS
MSAN13
(21)
MSAN22
R1
MSAN12
(62)
MSAN23
R2
R6
MSAN24
MSAN25
MSAN63
R5
R3
MSAN31
MSAN51
MSAN32
MSAN52
R4
MSAN33
MSAN53
MSAN34
MSAN35
MSAN54
CR2
CR1
MSAN55
MSAN56
Modernization of the urban network
with transit exchanges (3)
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Modernization of the urban network
with transit exchanges (4)
IP network with QoS
MSAN11
R2
MSAN22
R1
MSAN12
TX1o
MSAN23
R5
R3
IP-PBX1
MSAN52
TX2o
IP-PBX2
MSAN24
MSAN53
TX1i
MSAN25
TX2i
IP-PBX3
CO13
CR2
CO23
Toll exchange
Modernization of the urban network
with transit exchanges (5)
MSAN11
(61)
IP network with QoS
MSAN13
(21)
MSAN22
R1
MSAN12
(62)
MSAN23
R2
R6
IP-PBX1
MSAN24
MSAN25
MSAN63
R5
R3
MSAN51
MSAN33
MSAN52
IP-PBX2
MSAN31
R4
MSAN32
IP-PBX3
MSAN53
MSAN34
MSAN35
MSAN54
CR2
CR1
MSAN55
MSAN56
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Risk estimation for PSTN Operator
Development of the
PSTN without
transition to NGN
Construction of the
NGN as overlaid
network
Pragmatic approach
towards NGN
construction
Mean
value
Variation
coefficient
Mean
value
Variation
coefficient
Mean
value
Variation
coefficient
0.81
0.25
0.40
0.59
0.35
0.69
Poll results acquired by means of Delphi method
Economics and risks: typical NPV curves
NPV (Net present value)
RIII
RII
Payback period
RI
Time
TI
TII TMAX
TIII
II
tI
III
IMAX
tII
Event “X”
IIII
tIII
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Transition from PSTN to NGN:
Possible Scenarios
Thank you!
Nikolay Sokolov, Saint-Petersburg
e-mail: sokolov@niits.ru
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