1. The NGN Initiative – Why? Who
benefits?
In the discussion thread “Can VoIP meet the quality compare to PSTN” a detailed
discussion has been carried out on the above subject and it has been clearly
established that
1. VoIP calls need higher bandwidth.
2. VoIP suffers from problems of
a. Jitter
b. Latency
c. QoS
d. Need lot more effort to manage the network to produce acceptable voice
quality
3. VoIP is here to stay and coexist with PSTN, but can never replace it since
a. P2p leased lines derived from the PSTN networks are required for
i. Setting up private networks for enterprises / organisations to ensure
100% security of internal databases.
ii. Connecting POPs of IP Backbones (IPBs) of TSPs (telephone
service providers) and ISPs (Internet service Providers) in mesh or
tri-node topologies.
b. The need for the ISDN (a sub-set of PSTN) synchronous communication
network for quality public video-conferencing.
4. The belief that VoIP is needed for unification of communications (convergence) is
unfounded as has been seen in the triple play systems implemented by various
TSPs for supplying simultaneous telephony (PSTN), high speed Internet access,
and Video (broadcast or on-demand) over ADSL 2+ subscriber access over
existing telephone cable pairs, using IP transport of Video from Head-end to
DSLAMs. This has caused
a. Packet loss resulting in fall in QoS
b. High Zap times – time between change of channels
c. Higher maintenance costs
5. These problems can be easily resolved by having flexible channelized TDM
transport from the Head-end of the TV Broadcast and the Regional Content
Farms for VOD, to the DSLAMs in the LEX building. This step would replace the
IP transport of Video signals from the broadcast Head-end of the TSP and
various VOD content Farms to the DSLAMs at the LEX buildings, by the flexible
channelized TDM transport and
a. Ensure 100% QoS, zero packet loss
b. Reduced Zap time
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2. c. Lower cost of maintenance
6. It has also been established that convergence can be achieved more cost
effectively using mixed networks – Circuit Switched (CS) (for voice / fax / video)
and Packet Switched (PS) (for data and other IP services).
One of the factors which have been influencing the serious consideration of VoIP
despite all its inherent problems is the advent of the Next Generation Network (NGN)
initiative of some telecom operators.
As telecom professionals it is necessary for us to analyse the relevance criteria
of the NGN initiative and to understand what is driving this initiative.
1. With the limitation of data speeds on subscriber access networks in PSTN, the
TSPs set up their respective IP Backbones (IPBs) to facilitate high speed data
communications.
2. The IPBs provide facilities for setting up VPNs for individual enterprise /
organisation data connectivity.
3. The IPBs are also used for connecting the NIXI (National Internet Exchange
Interface) and provides high speed Internet access through Broadband
Subscriber Access, p2p leased lines, and also for dial-up access through PSTN /
ISDN.
4. TSPs do not normally encourage voice calls using VoIP over their IPBs, but have
no means of checking VoIP calls coming in through the Internet.
5. Even for the broadband ADSL 2+ connectivity telephony is through the metered
PSTN network.
6. The IPBs of TSPs are built by connecting their POPs through TDM/SDH links
derived from the PSTN network as shown in Fig.2 of the document
Telephony.pdf available in the URL http://www.slideshare.net/pankajmitra., in full
mesh or tri-node topology. This is shown in Fig.1 of the document VPN.pdf
available in the same URL. The links used for the main TSP IPB could range
from STM1 to STM64. The IPB of ISPs may have links nxE1, E3, lower order
STM.
7. Thus in the present TSP networks we have the PSTN networks based on
digitised CS for voice / fax / public video (multiple ISDN connections); and the
IPB for high speed data communication and Internet access through Broadband
Subscriber Access, p2p leased lines to TSP IPB POPs, and VPN created
through the IPB.
8. What is being planned in the NGN (Next Generation Network) is the transfer of
CS voice running through the PSTN worldwide, to PS voice over the IPBs of
each TSP and through linked IPBs worldwide.
9. As we have seen in the earlier discussion thread referred to at the beginning of
this note, for the same quality of speech and at the same level of compression
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3. and the same MOS (mean opinion scale), PS voice (VoIP) needs 5 times more
bandwidth than CS voice (PSTN).
10. Again we have seen that the cost ratio of voice to non-voice (data and fax)
communications worldwide ranges from 80:20 (developed countries) to 95:5 or
97:3 (developing countries).
11. At the data speeds available on the PSTN, the corresponding volume ratios
would be 80:1200, 95:300, 97:180.
12. With the data speeds available in the IPB, the volume ration would increase
substantially in favour of data. However, the cost ratio will also alter due to the
higher cost of bandwidth used in the IPB.
13. The IPB will continue to be formed using TDM/SDH links connecting the POPs
through full mesh or tri-node topologies.
14. What would be the implications of transforming from the Present
Generation Network (PGN) to NGN?
a. The existing PSTN infrastructure which is fully functional and very stable
will be made redundant at
i. The local exchange
ii. The Access Network (AN)
iii. The TAX (trunk automatic exchange) of the transport network.
b. The IPB will have to be strengthened many fold to take the total voice load
of the present PSTN network which presently occupies the major telecom
traffic worldwide (95-98%), over its present data load.
c. The TDM/SDH transport network will continue.
d. The FO and HO Muxes in the Local Exchange Buildings used for deriving
the p2p leased lines between the TSP / ISP POPs and between
Enterprise / Organisation premises to form private networks for 100%
security of internal databases, will continue.
e. Travelling through multiple POPs, introduces latency, jitter, etc. In PS
voice.
f. Any failures in the p2p links forming the IPB and any other network
components will need more time to detect and rectify than in the case of
CS voice networks run on PSTN.
15. Which parts of the PGN will need to be changed to transform it to the NGN?
a. The subscriber to the exchange aggregator (EA) / IP router in the
exchange building will continue to be the existing copper cables through
the ADSL2+ digital subscriber access broadband lines.
b. New subscribers or p2p links to the IPB POPs may be through OFCs
(optical fibre cables), as is the case now.
c. The PCM/TDM switches will be replaced by the routers/switches placed in
the LEX building, and / or EAs (exchange aggregators) for flexible
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4. channelized TDM transport of video signals from Head-end to DSLAMs in
the exchange buildings.
d. The public FOMs (first order Muxes) and HOMs (higher order Muxes)
associated with the PSTN networks will be made redundant.
e. The TAX switches associated with the PSTN in the transport network will
be made redundant.
f. The FO and HO Muxes in the LEX building associated with the formation
of the p2p leased lines will have to continue.
g. The non-TAX mux associated with the p2p leased lines in the transport
network will have to continue.
h. The distribution copper infrastructure along with the broadband access
infrastructure for individual subscribers will be retained.
i. The existing p2p leased lines for connecting enterprises / organisations to
the IPB POPs will be retained and strengthened as these will now have to
carry the voice traffic as well.
j. The TDM/SDH transport network and the access network for forming the
p2p links within a city and across the country and the world will be
retained.
16. What are reasons ascribed for this transformation?
a. Unification of services on a single network.
b. Quicker deployment.
c. Management and maintenance of one network in place of the present
generation network (PGN)
17. Basic disadvantage?
a. Large bandwidth requirement
b. More difficult to manage
18. The experience of the UK NGN implementation has indicated that
a. It does not speed up deployment.
b. The outages are very difficult to restore, causing hours of outages.
c. Maintenance cost of the unified network is higher than two separated
networks.
19. Who are driving the transformation and change and why?
a. In a total world population of 6.8 billion people, there are already between
4 to 5 billion telephone subscribers. Hence there will be slowing down of
the growth of further subscribers as this reaches saturation levels.
b. This is realised by the manufacturers of present generation network (PGN)
infrastructure equipment manufacturers. They know that the growth of new
infrastructure equipment will become tardy and they will have to be
satisfied with incremental growth, and supply of spares.
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5. c. By changing the system which cannot use existing infrastructure, they will
open up opportunity of new and rapid growth of business for the products
required for the new system.
d. Thus it is the manufacturers of the new products and the older ones
who also have these products who are driving the change /
transformation of the PGN to NGN.
20. Who benefits?
a. Subscriber –
i. All he/she wants is to be able to communicate. Impervious to how it
is being done.
ii. He/she does not get any major quality advantage as has been seen
in the discussion thread “Can VoIP meet the quality compare to
PSTN”
iii. Will still have to pay as they use the service for which charges will
be determined.
iv. The TSPs will have to recover the expenditure during the life of the
new infrastructure, and this will have to be done from their
subscribers. There are no free lunches.
b. TSP –
i. Will be losing valuable working assets – no compensation for this.
ii. Will have to install new switching, CPE, management, and billing
infrastructure, at high costs.
iii. Will incur higher management costs.
iv. Will have to retrain their staff.
v. Large sums of money will have to be spent to carry out the
transformation from PGN to NGN.
vi. Such expenditure gives some benefits to some of people in the
spending organisation.
vii. They will recover this additional capital expenditure from their
subscribers within the lifespan of the new infrastructure and will
have to fix the tariffs accordingly subject to market conditions.
c. Manufacturers of existing infrastructure –
i. Will lose ongoing business for their existing products
ii. May gain if they are manufacturers of Soft Switches, Media Control
Gateways, new CPE, and Billing Equipment / software.
d. Manufacturers of new infrastructure –
i. These people are the real beneficiaries of the change
ii. They are the ones pushing for the change and transformation
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6. 21. What is the relevance of transformation from PGN to NGN?
a. Subscribers
i. Irrelevant
ii. Have to pay so that TSPs can recover their upfront expenditure
within the lifespan of the new infrastructure
b. Telephone Service Providers (TSPs)
i. Expected advantages of unification is nebulous
ii. High upfront capital expenditure
iii. Higher maintenance cost than that incurred in the PGN.
iv. No major technical benefits.
c. Manufacturers of existing infrastructure
i. Losers unless they have the products required for the new system
and have pushed for the transformation to cash in on the new
opportunities.
d. Manufacturers of new infrastructure
i. Gainers
e. Overall
i. No one benefits except the manufacturers of new
infrastructure and some people in the spending organisations.
ii. No major technical gains to be made from the transformation
from PGN to NGN.
iii. Is all this additional expenditure and the hullabaloo around
this transformation necessary? I do not think so.
22. Why then does the world opt for such irrelevant, nebulous, transformation,
and at such additional costs?
a. It is the same old story.
b. We have seen that the foreign policy of some major nations have been
largely dictated by the manufacturers of war machinery.
c. Manufacturers produce equipment and then try and force this on possible
users. This is done for two reasons
i. To get major technical and operating cost benefits, or
ii. To create new opportunities when the market for the current range
of products saturates. In such situations a change of technology
makes existing equipment redundant forcing a change and
increase in business for the replacement products.
d. Once they have convinced and influenced the key decision makers in the
prospect organisation, these people then set about finding the justification
for carrying out the change.
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7. e. Should we allow this trend to continue particularly if the
transformation does not give significant technical or operating cost
benefits?
f. Should we not ask manufacturers to produce that which will benefit society
in which they operate?
g. Should we not ask manufacturers to make equipment which is relevant to
the users and for which their expenditures come down?
23. I would like to hear the views of what other Telecom Professionals have to
say and would urge them to consider the relevance criteria of this and all
other initiatives in the future.
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