Monday, November 18, 2013

New Horizon of Telecommunication in BTCL: 171 KL Project

Md. Shahidul Alam*
Md. Aslam Hossain


1.      Introduction: A glimpse of the past

1.1 Manual/Analogue Era: Bangladesh Telecommunications Company Ltd (BTCL) inherited telecommunication system from the then British India through a series of transformation. Telegraph system was first introduced in Bengal in 1853 by the East India Company of England, the then colonial ruler of Bengal. Following the telegraph system different telecommunication services were introduced one after another. During independence from British India, the telecommunication system of the then East Pakistan (also in Indian subcontinent) was manual. Manual Magneto Exchange was the main exchange for voice communication and telegraph system was the main source of data communication using Morse code. Over head Physical lines were the main transmission media. Since then there was a lot technological change in the field of telecommunication. After Magneto exchange another manual exchange Central Battery (CB) Exchange was introduced. In magneto and Central Battery manual exchanges a call set up between two persons was done with the help of operators i.e., when someone intends to talk to another one he had to rotate the handle of magneto phone or off hook receiver of telephone set belonging to Central Battery system to notify the operators and he gave the telephone number of his intended person to the operator. For long distance call nation and International calls some times more than two operators were involved to connect a call.  The operators then connect both caller & called party through a Switch Board.  After manual system Electromechanical system such as F1, Cross bar and EMD system were installed and worked until mid 80s of last Century in BTCL (the then BTTB) network. Though these Electromechanical Exchanges were automatic, except voice communication, there was no Value Added Services (VAS).

1.2 Automatic/Digital Era: Bangladesh Telecommunications Company Ltd entered into the era of digital telecommunication through the introduction of NEC's NEAX 61K/M Model digital Trunk Automatic Exchanges(TAX) in Dhaka, Chittagong, Bogra and Khulna and 0ne  International Trunk Exchange (ITX) in Dhaka. With the introduction of digital TAXs and ITX, subscribers themselves could make long distance national and international call by direct dialing using local area code and overseas Telephone number without the help of operator. With the aim of total digitization, the 1st digital telephone exchange (class 5 service) of the country was introduced in Dhaka during the late 80s with NEC's NEAX 61E. These digital exchanges were deployed with some Value Added services. Later in 90s Digital exchanges [E-10, Alcatel, France] were installed in Dhaka, Chittagong, Khulna, Rajshahi and Sylhet with ISDN facilities. From then onwards different networks consist of switches of many vendors such as Ericsson, Nortel, Shanghai Bell, Huawei, ZTE etc were installed throughout the country. At present telecommunication network of Dhaka metro city is a non-homogeneous mixture of digital exchanges of various generations and techniques.

1.3 IP/Packet based communication Era:  The technology applied in the telecommunication systems is changing rapidly. The customer now demands all types of entertainment and communication services from a single delivery point. As the Circuit-switched exchange can’t meet this integration requirement, BTCL has no choice but adopting IP based NGN technology to cope with the present demand and to modernize the telecommunication system by undertaking a project named ‘Replacement of Old Digital Telephone System of Dhaka city’ commonly known as 171 KL Project.

*General Manager, BTCL
   ** Divisional Engineer, BTCL






2.      Aim/Objective of the Project:
All [total 747 as of now] of the telephone exchanges [Class 5] of BTCL that are operational now based on circuit-switching technology and a huge amount of copper cables are required to connect each customer. In this project, Optical fiber will be installed from exchange [Soft- switch or a node of it: there will be 2 soft-switches one at SBN and another at Ramna with 5 other nodes at Gulshan, Uttara, Mirpur, Nilkhet & Mogbazar] to AGW [Access Gateway: A small exchange which will be installed near customer’s house at rented/outdoor premises] to reduce the application of copper cable. In some places optical fiber will be installed up to customers’ homes [FTTH] or buildings [FTTB]. With the application of optical fiber at the distribution level, a huge bandwidth [Minimum 20 Mbps per customer for the case of FTTB and even more in the case of FTTH] is possible to offer each customer with a range of diversified value added services like IPTV, VoD, Online Gaming etc. The project has chosen Mirpur DOHS as its first FTTH site and the implementation work is going on. Upon completion of this site, other areas of Dhaka city can be considered. FTTB will be implemented some important areas like part of Dhanmondi, Gulshan, Nilkhet, Mogbazar, Uttara and Ramna. AGW will be installed throughout Dhaka city.

3.      Project Details :Facilities/Services to be provided by this project—

This project is the 1st of its kind taken by BTCL to provide multiple services like voice, video & data by a pair of wires from a single delivery point. This NGN based solution will make the new system cheaper and more versatile. It will also reduce copper cable portion of customer lines and hence will reduce the occurrence of regular faults. A huge potential/hidden demand for telephones and different value added services presently exist in the telecom sector and BTCL can exploit it upon completion of this project.

3.1    AGW, LAN Switch, FTTH/FTTB Equipment/Terminals:
Main items
Quantity
Total AGWs

196
[Inside BTCL exchanges: 52, rented indoor: 81, Outdoor:63]
POTS only [80%] and POTS+ADSL2plus [20%]
Total Type-1 LAN Switch
2
[SBN and Ramna for interconnection with other network devices]
Total Type-2 LAN Switch
6
[installed at Gulshan, Mogbazar, Uttara, Nilkhet, Mirpur and DoHS, Mirpur site for interconnection with other network devices]
Total Type-3 LAN Switch
35
[installed at 35 sites where a demand of Internet bandwidth exists]
Total GPON OLT sites
7
[SBN, Ramna, Gulshan, Mogbazar, Uttara, Mirpur DoHS and Nilkhet]
Total GPON Ports
376
[The capacity of each port is 2.5Gbps down & 1.25Gbps up link and each OFC line can be splitted up to 8x8=64 lines]
Total FTTH/FTTB
FTTH [4,500 Homes only for Mirpur DoHS area],
FTTB [1,600 Buildings through Dhaka city]
Total MDUs
[To connect buildings]
1,600
950 nos of capacity [24 POTS+24 FE] & 650 nos of capacity [16 POTS+16 FE]
Total SBUs
[To connect small business units]
25
Each SBU’s capacity is [8POTS+4FE+8E1]
Total ONTs
[To connect each home]
4,500
Each ONT’s capacity is [2 POTS+4FE]
Total ONT Batteries
500
 [out of total 4500 ONTS, 500 will have batteries]
Total UPS for MDU
150
[out of total 1600 MDUs, 150 will have UPS]
3.2    Quantity of Total POTS Lines, ADSL2+ Lines and FE Ports:

Technology used
POTS Line
ADSL2+ line
FE port

Through AGW
196,672
35,840
0

Through MDU [FTTB]
33,200
0
33,200

Through SBU
200
0
100

Through ONT [FTTH]
9,000
0
18,000

Total
239,072
35,840
51,300
         
     3.3  Capacity & quantity of AGWs exchange-wise:


Sites
Qty of AGW Cabinets
Line/Cabinet
Total Line/site
MDF Capacity/site
No of cards

POTS
ADSL
POTS
ADSL
POTS
ADSL

AGW, TYPE-1

Sher-e-Bangla Nagar
5
1,600
256
8,000
1,280
8,000
1,280
21*64+8*32

Ramna
5
1,600
256
8,000
1,280
8,000
1,280

Nilkhet
5
1,600
256
8,000
1,280
8,000
1,280

Moghbazar
5
1,600
256
8,000
1,280
8,000
1,280

Mirpur
5
1,600
256
8,000
1,280
8,000
1,280

Gulshan
5
1,600
256
8,000
1,280
8,000
1,280

Uttara
5
1,600
256
8,000
1,280
8,000
1,280

TOTAL for Type-1
35
56,000
8,960
56,000
8,960

AGW, TYPE-2

Different Rented Place (with LAN Switch)
35
1,216
192
42,560
6,720
56,000
8,960
16*64+6*32 expandable upto 21*64+8*32

Total for type-2
35
42,560
6,720
56,000
8,960

AGW, TYPE-3

Chawkbazar
6
1,664
192
9,984
1,152
9,984
1,152
23*64+6*32

Babubazar
6
1,664
192
9,984
1,152
9,984
1,152

TOTAL for Type-3
12
19,968
2,304
19,968
2,304

AGW, TYPE-4

Lalbagh
1
1,216
192
1,216
192
1,600
256
16*64+6*32                                                       expandable upto 21*64+8*32

Khilgaon
2
1,216
192
2,432
384
3,200
512

Goran
1
1,216
192
1,216
192
1,600
256

Mohanagar
1
1,216
192
1,216
192
1,600
256

Different Rented Place (without LAN Switch)
46
1,216
192
55,936
8,832
73,600
11,776

TOTAL for Type-4
51
62,016
9,792
81,600
13,056

AGW, TYPE-5 (Outdoor Type)

Different Sites
63
256
128
16,128
8,064
30,240
14,112
2*64+4*32 expandable upto 4*64+7*32

TOTAL for Type-5
63
16,128
8,064
30,240
14,112

Grand Total for AGWs
196
196,672
35,840
243,808
47,392

4.      Conclusion:  
The implementation period for this project is September 2009 to June 2014. The OSP implementation work is difficult in Dhaka city and renting of houses is costly. Getting electricity connection for AGWs at rented premises is also very troublesome.
So for the future projects to be taken by BTCL, we recommend the following:

a)      The Access network will be an integral part of the GPON system. The GPON OLT will have different types of interface boards which are capable of providing different types of services like POTS, ADSL, VDSL, FTTB, FTTH, FTTC etc. The customer end device namely MDU [for FTTB, POTS, ADSL and VDSL services], ONT [for FTTH] and SBU [for small business units] will be connected with GPON OLT by a pair of optical fibers.
b)      ONT and SBU will be placed inside the customer’s home/office while the MDUs will be installed inside any building. No renting of houses & no commercial electricity connection will be necessary but an arrangement with the building owner will be required. From MDU copper cable networks will be implemented but within a very small area [for POTS, ADSL & VDSL only telephone cables and for POTS and FEs both telephone and Cat5 cable up to customer will be needed].
c)       Before implementing the cable [both OFC & copper] networks, a comprehensive survey of existing cables will have to be done by the vendors/contractors to utilize the existing cables and to avoid repetition of works.
d)      There should be intelligent fault diagnosis system to help locate faults quickly and accurately for all the new and existing OFC and copper cable networks. Automated messages to the maintenance staffs for any occurrence of such faults should have to be sent immediately.
e)      At BTCL Exchange [CO], we need to arrange only GPON OLT.
   


Type-1.  GPON OLT interface (Optical) broad
Type-2.  GE Ethernet interface (optical)
Type-3.  STM-1 interface cards (Optical)
Type-4.  Electrical E1 boards
Type-5.  POTS  only  or POTS + ADSL [combo cards] or POTS  +VDSL [combo cards]  cards.




f)       Outside BTCL Exchanges we need only small cabinets:

From GPON OLT to customer end: Splitters may or may not be used [for Type-1service boards splitters may be used and for Type-2 service boards no splitting will be used].
 


                                               
Consists: Mainly MDU which will need a cabinet box completed with battery, MDF and
               Splitter & splice tray (where necessary)

Option 1: functions like AGW coming from type-2 cards of GPON OLT without splitting

POTS+VDSL [Combo] cards
POTS+ADSL [Combo] cards
POTS Only cards

Option 2: functions like FTTB coming from type-1 cards of GPON OLT with splitting
Option 3: functions like FTTH coming from type-1 cards of GPON OLT with splitting
Option 4: functions like Small Business Unit (SBU) to feed enterprise customers

g)      Service to be offered to the customers:
1.       POTS only.
2.       POTS+ ADSL2+ [internet speed up to 2 Mbps or even more]
3.       POTS+VDSL  [Speed up to 10 Mbps]
4.       POTS+FE [Speed up to 20 Mbps]   à  FTTB
5.       multiple POTS+ multiple FEs [speed up to 78 Mbps] à  FTTH
6.       multiple POTS+ multiple FEs + multiple E1s à SBU for enterprise customers.
[For serial 3 to 6 value added services like IPTV, VoD and On Line Gaming shall be offered]
7.   Other services like VPN [point to point & point to multi point], Leased line internet of any band
      width will also be offered to customers by utilizing LAN Switch already placed at different places   
      of Dhaka city.

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